[RFC PATCH v4 00/17] powerpc: Core ftrace rework, support for ftrace direct and bpf trampolines

[RFC PATCH v4 00/17] powerpc: Core ftrace rework, support for ftrace direct and bpf trampolines

[Naveen N Rao]

This is v4 of the series posted here:
http://lkml.kernel.org/r/cover.1718908016.git.naveen@kernel.org

This series reworks core ftrace support on powerpc to have the function 
profiling sequence moved out of line. This enables us to have a single 
nop at kernel function entry virtually eliminating effect of the 
function tracer when it is not enabled. The function profile sequence is 
moved out of line and is allocated at two separate places depending on a 
new config option.

For 64-bit powerpc, the function profiling sequence is also updated to 
include an additional instruction 'mtlr r0' after the usual 
two-instruction sequence to fix link stack imbalance (return address 
predictor) when ftrace is enabled. This showed an improvement of ~22% in 
null_syscall benchmark on a Power 10 system with ftrace enabled.

Finally, support for ftrace direct calls is added based on support for
DYNAMIC_FTRACE_WITH_CALL_OPS. BPF Trampoline support is added atop this.

Support for ftrace direct calls is added for 32-bit powerpc. There is 
some code to enable bpf trampolines for 32-bit powerpc, but it is not 
complete and will need to be pursued separately.

This is marked RFC so that this can get more testing. Patches 1 to 10 
are independent of this series and can go in separately though. Rest of 
the patches depend on the series from Benjamin Gray adding support for 
patch_uint() and patch_ulong():
http://lkml.kernel.org/r/20240515024445.236364-1-bgray@linux.ibm.com


Changelog v4:
- Patches 1, 10 and 13 are new.
- Address review comments from Nick. Numerous changes throughout the 
  patch series.
- Extend support for ftrace ool to vmlinux text up to 64MB (patch 13).
- Address remaining TODOs in support for BPF Trampolines.
- Update synchronization when patching instructions during trampoline 
  attach/detach.


- Naveen


Naveen N Rao (17):
  powerpc/trace: Account for -fpatchable-function-entry support by
    toolchain
  powerpc/kprobes: Use ftrace to determine if a probe is at function
    entry
  powerpc64/ftrace: Nop out additional 'std' instruction emitted by gcc
    v5.x
  powerpc32/ftrace: Unify 32-bit and 64-bit ftrace entry code
  powerpc/module_64: Convert #ifdef to IS_ENABLED()
  powerpc/ftrace: Remove pointer to struct module from dyn_arch_ftrace
  powerpc/ftrace: Skip instruction patching if the instructions are the
    same
  powerpc/ftrace: Move ftrace stub used for init text before _einittext
  powerpc64/bpf: Fold bpf_jit_emit_func_call_hlp() into
    bpf_jit_emit_func_call_rel()
  powerpc/ftrace: Add a postlink script to validate function tracer
  kbuild: Add generic hook for architectures to use before the final
    vmlinux link
  powerpc64/ftrace: Move ftrace sequence out of line
  powerpc64/ftrace: Support .text larger than 32MB with out-of-line
    stubs
  powerpc/ftrace: Add support for DYNAMIC_FTRACE_WITH_CALL_OPS
  powerpc/ftrace: Add support for DYNAMIC_FTRACE_WITH_DIRECT_CALLS
  samples/ftrace: Add support for ftrace direct samples on powerpc
  powerpc64/bpf: Add support for bpf trampolines

 arch/Kconfig                                |   6 +
 arch/powerpc/Kconfig                        |  23 +-
 arch/powerpc/Makefile                       |   8 +
 arch/powerpc/Makefile.postlink              |   8 +
 arch/powerpc/include/asm/ftrace.h           |  32 +-
 arch/powerpc/include/asm/module.h           |   5 +
 arch/powerpc/include/asm/ppc-opcode.h       |  14 +
 arch/powerpc/kernel/asm-offsets.c           |  11 +
 arch/powerpc/kernel/kprobes.c               |  18 +-
 arch/powerpc/kernel/module_64.c             |  66 +-
 arch/powerpc/kernel/trace/Makefile          |  11 +-
 arch/powerpc/kernel/trace/ftrace.c          | 295 ++++++-
 arch/powerpc/kernel/trace/ftrace_64_pg.c    |  69 +-
 arch/powerpc/kernel/trace/ftrace_entry.S    | 246 ++++--
 arch/powerpc/kernel/vmlinux.lds.S           |   3 +-
 arch/powerpc/net/bpf_jit.h                  |  12 +
 arch/powerpc/net/bpf_jit_comp.c             | 842 +++++++++++++++++++-
 arch/powerpc/net/bpf_jit_comp32.c           |   7 +-
 arch/powerpc/net/bpf_jit_comp64.c           |  68 +-
 arch/powerpc/tools/Makefile                 |  10 +
 arch/powerpc/tools/ftrace-gen-ool-stubs.sh  |  52 ++
 arch/powerpc/tools/ftrace_check.sh          |  45 ++
 samples/ftrace/ftrace-direct-modify.c       |  85 +-
 samples/ftrace/ftrace-direct-multi-modify.c | 101 ++-
 samples/ftrace/ftrace-direct-multi.c        |  79 +-
 samples/ftrace/ftrace-direct-too.c          |  83 +-
 samples/ftrace/ftrace-direct.c              |  69 +-
 scripts/Makefile.vmlinux                    |   8 +
 scripts/link-vmlinux.sh                     |  11 +-
 29 files changed, 2083 insertions(+), 204 deletions(-)
 create mode 100644 arch/powerpc/tools/Makefile
 create mode 100755 arch/powerpc/tools/ftrace-gen-ool-stubs.sh
 create mode 100755 arch/powerpc/tools/ftrace_check.sh


base-commit: 582b0e554593e530b1386eacafee6c412c5673cc
prerequisite-patch-id: a1d50e589288239d5a8b1c1f354cd4737057c9d3
prerequisite-patch-id: da4142d56880861bd0ad7ad7087c9e2670a2ee54
prerequisite-patch-id: 609d292e054b2396b603890522a940fa0bdfb6d8
prerequisite-patch-id: 6f7213fb77b1260defbf43be0e47bff9c80054cc
prerequisite-patch-id: ad3b71bf071ae4ba1bee5b087e61a2055772a74f
-- 
2.45.2

[RFC PATCH v4 01/17] powerpc/trace: Account for -fpatchable-function-entry support by toolchain

[Naveen N Rao]

So far, we have relied on the fact that gcc supports both
-mprofile-kernel, as well as -fpatchable-function-entry, and clang
supports neither. Our Makefile only checks for CONFIG_MPROFILE_KERNEL to
decide which files to build. Clang has a feature request out [*] to
implement -fpatchable-function-entry, and is unlikely to support
-mprofile-kernel.

Update our Makefile checks so that we pick up the correct files to build
once clang picks up support for -fpatchable-function-entry.

[*] https://github.com/llvm/llvm-project/issues/57031

Signed-off-by: Naveen N Rao <naveen@kernel.org>
---
 arch/powerpc/kernel/trace/Makefile | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kernel/trace/Makefile b/arch/powerpc/kernel/trace/Makefile
index 125f4ca588b9..d6c3885453bd 100644
--- a/arch/powerpc/kernel/trace/Makefile
+++ b/arch/powerpc/kernel/trace/Makefile
@@ -9,12 +9,15 @@ CFLAGS_REMOVE_ftrace.o = $(CC_FLAGS_FTRACE)
 CFLAGS_REMOVE_ftrace_64_pg.o = $(CC_FLAGS_FTRACE)
 endif
 
-obj32-$(CONFIG_FUNCTION_TRACER)		+= ftrace.o ftrace_entry.o
-ifdef CONFIG_MPROFILE_KERNEL
-obj64-$(CONFIG_FUNCTION_TRACER)		+= ftrace.o ftrace_entry.o
+ifdef CONFIG_FUNCTION_TRACER
+obj32-y					+= ftrace.o ftrace_entry.o
+ifeq ($(CONFIG_MPROFILE_KERNEL)$(CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY),)
+obj64-y					+= ftrace_64_pg.o ftrace_64_pg_entry.o
 else
-obj64-$(CONFIG_FUNCTION_TRACER)		+= ftrace_64_pg.o ftrace_64_pg_entry.o
+obj64-y					+= ftrace.o ftrace_entry.o
 endif
+endif
+
 obj-$(CONFIG_TRACING)			+= trace_clock.o
 
 obj-$(CONFIG_PPC64)			+= $(obj64-y)
-- 
2.45.2

[RFC PATCH v4 02/17] powerpc/kprobes: Use ftrace to determine if a probe is at function entry

[Naveen N Rao]

Rather than hard-coding the offset into a function to be used to
determine if a kprobe is at function entry, use ftrace_location() to
determine the ftrace location within the function and categorize all
instructions till that offset to be function entry.

For functions that cannot be traced, we fall back to using a fixed
offset of 8 (two instructions) to categorize a probe as being at
function entry for 64-bit elfv2, unless we are using pcrel.

Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Naveen N Rao <naveen@kernel.org>
---
 arch/powerpc/kernel/kprobes.c | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index 14c5ddec3056..ca204f4f21c1 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -105,24 +105,22 @@ kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
 	return addr;
 }
 
-static bool arch_kprobe_on_func_entry(unsigned long offset)
+static bool arch_kprobe_on_func_entry(unsigned long addr, unsigned long offset)
 {
-#ifdef CONFIG_PPC64_ELF_ABI_V2
-#ifdef CONFIG_KPROBES_ON_FTRACE
-	return offset <= 16;
-#else
-	return offset <= 8;
-#endif
-#else
+	unsigned long ip = ftrace_location(addr);
+
+	if (ip)
+		return offset <= (ip - addr);
+	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && !IS_ENABLED(CONFIG_PPC_KERNEL_PCREL))
+		return offset <= 8;
 	return !offset;
-#endif
 }
 
 /* XXX try and fold the magic of kprobe_lookup_name() in this */
 kprobe_opcode_t *arch_adjust_kprobe_addr(unsigned long addr, unsigned long offset,
 					 bool *on_func_entry)
 {
-	*on_func_entry = arch_kprobe_on_func_entry(offset);
+	*on_func_entry = arch_kprobe_on_func_entry(addr, offset);
 	return (kprobe_opcode_t *)(addr + offset);
 }
 
-- 
2.45.2

[RFC PATCH v4 03/17] powerpc64/ftrace: Nop out additional 'std' instruction emitted by gcc v5.x

[Naveen N Rao]

Gcc v5.x emits a 3-instruction sequence for -mprofile-kernel:
	mflr	r0
	std	r0, 16(r1)
	bl	_mcount

Gcc v6.x moved to a simpler 2-instruction sequence by removing the 'std'
instruction. The store saved the return address in the LR save area in
the caller stack frame for stack unwinding. However, with dynamic
ftrace, we no longer have a call to _mcount on kernel boot when ftrace
is not enabled. When ftrace is enabled, that store is performed within
ftrace_caller(). As such, the additional 'std' instruction is redundant.
Nop it out on kernel boot.

With this change, we now use the same 2-instruction profiling sequence
with both -mprofile-kernel, as well as -fpatchable-function-entry on
64-bit powerpc.

Signed-off-by: Naveen N Rao <naveen@kernel.org>
---
 arch/powerpc/kernel/trace/ftrace.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
index d8d6b4fd9a14..2ef504700e8d 100644
--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/arch/powerpc/kernel/trace/ftrace.c
@@ -246,8 +246,12 @@ int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
 		/* Expected sequence: 'mflr r0', ['std r0,16(r1)'], 'bl _mcount' */
 		ret = ftrace_read_inst(ip - 4, &old);
 		if (!ret && !ppc_inst_equal(old, ppc_inst(PPC_RAW_MFLR(_R0)))) {
+			/* Gcc v5.x emit the additional 'std' instruction, gcc v6.x don't */
 			ret = ftrace_validate_inst(ip - 8, ppc_inst(PPC_RAW_MFLR(_R0)));
-			ret |= ftrace_validate_inst(ip - 4, ppc_inst(PPC_RAW_STD(_R0, _R1, 16)));
+			if (ret)
+				return ret;
+			ret = ftrace_modify_code(ip - 4, ppc_inst(PPC_RAW_STD(_R0, _R1, 16)),
+						 ppc_inst(PPC_RAW_NOP()));
 		}
 	} else {
 		return -EINVAL;
-- 
2.45.2

[RFC PATCH v4 04/17] powerpc32/ftrace: Unify 32-bit and 64-bit ftrace entry code

[Naveen N Rao]

On 32-bit powerpc, gcc generates a three instruction sequence for
function profiling:
	mflr	r0
	stw	r0, 4(r1)
	bl	_mcount

On kernel boot, the call to _mcount() is nop-ed out, to be patched back
in when ftrace is actually enabled. The 'stw' instruction therefore is
not necessary unless ftrace is enabled. Nop it out during ftrace init.

When ftrace is enabled, we want the 'stw' so that stack unwinding works
properly. Perform the same within the ftrace handler, similar to 64-bit
powerpc.

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Naveen N Rao <naveen@kernel.org>
---
 arch/powerpc/kernel/trace/ftrace.c       | 6 ++++--
 arch/powerpc/kernel/trace/ftrace_entry.S | 4 ++--
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
index 2ef504700e8d..8c3e523e4f96 100644
--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/arch/powerpc/kernel/trace/ftrace.c
@@ -240,8 +240,10 @@ int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
 	} else if (IS_ENABLED(CONFIG_PPC32)) {
 		/* Expected sequence: 'mflr r0', 'stw r0,4(r1)', 'bl _mcount' */
 		ret = ftrace_validate_inst(ip - 8, ppc_inst(PPC_RAW_MFLR(_R0)));
-		if (!ret)
-			ret = ftrace_validate_inst(ip - 4, ppc_inst(PPC_RAW_STW(_R0, _R1, 4)));
+		if (ret)
+			return ret;
+		ret = ftrace_modify_code(ip - 4, ppc_inst(PPC_RAW_STW(_R0, _R1, 4)),
+					 ppc_inst(PPC_RAW_NOP()));
 	} else if (IS_ENABLED(CONFIG_MPROFILE_KERNEL)) {
 		/* Expected sequence: 'mflr r0', ['std r0,16(r1)'], 'bl _mcount' */
 		ret = ftrace_read_inst(ip - 4, &old);
diff --git a/arch/powerpc/kernel/trace/ftrace_entry.S b/arch/powerpc/kernel/trace/ftrace_entry.S
index 76dbe9fd2c0f..244a1c7bb1e8 100644
--- a/arch/powerpc/kernel/trace/ftrace_entry.S
+++ b/arch/powerpc/kernel/trace/ftrace_entry.S
@@ -33,6 +33,8 @@
  * and then arrange for the ftrace function to be called.
  */
 .macro	ftrace_regs_entry allregs
+	/* Save the original return address in A's stack frame */
+	PPC_STL		r0, LRSAVE(r1)
 	/* Create a minimal stack frame for representing B */
 	PPC_STLU	r1, -STACK_FRAME_MIN_SIZE(r1)
 
@@ -44,8 +46,6 @@
 	SAVE_GPRS(3, 10, r1)
 
 #ifdef CONFIG_PPC64
-	/* Save the original return address in A's stack frame */
-	std	r0, LRSAVE+SWITCH_FRAME_SIZE+STACK_FRAME_MIN_SIZE(r1)
 	/* Ok to continue? */
 	lbz	r3, PACA_FTRACE_ENABLED(r13)
 	cmpdi	r3, 0
-- 
2.45.2

[RFC PATCH v4 05/17] powerpc/module_64: Convert #ifdef to IS_ENABLED()

[Naveen N Rao]

Minor refactor for converting #ifdef to IS_ENABLED().

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Naveen N Rao <naveen@kernel.org>
---
 arch/powerpc/kernel/module_64.c | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
index e9bab599d0c2..1db88409bd95 100644
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -241,14 +241,8 @@ static unsigned long get_stubs_size(const Elf64_Ehdr *hdr,
 		}
 	}
 
-#ifdef CONFIG_DYNAMIC_FTRACE
-	/* make the trampoline to the ftrace_caller */
-	relocs++;
-#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
-	/* an additional one for ftrace_regs_caller */
-	relocs++;
-#endif
-#endif
+	/* stubs for ftrace_caller and ftrace_regs_caller */
+	relocs += IS_ENABLED(CONFIG_DYNAMIC_FTRACE) + IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS);
 
 	pr_debug("Looks like a total of %lu stubs, max\n", relocs);
 	return relocs * sizeof(struct ppc64_stub_entry);
-- 
2.45.2

[RFC PATCH v4 06/17] powerpc/ftrace: Remove pointer to struct module from dyn_arch_ftrace

[Naveen N Rao]

Pointer to struct module is only relevant for ftrace records belonging
to kernel modules. Having this field in dyn_arch_ftrace wastes memory
for all ftrace records belonging to the kernel. Remove the same in
favour of looking up the module from the ftrace record address, similar
to other architectures.

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Naveen N Rao <naveen@kernel.org>
---
 arch/powerpc/include/asm/ftrace.h        |  1 -
 arch/powerpc/kernel/trace/ftrace.c       | 49 +++++++++--------
 arch/powerpc/kernel/trace/ftrace_64_pg.c | 69 ++++++++++--------------
 3 files changed, 56 insertions(+), 63 deletions(-)

diff --git a/arch/powerpc/include/asm/ftrace.h b/arch/powerpc/include/asm/ftrace.h
index 107fc5a48456..201f9d15430a 100644
--- a/arch/powerpc/include/asm/ftrace.h
+++ b/arch/powerpc/include/asm/ftrace.h
@@ -26,7 +26,6 @@ unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip,
 struct module;
 struct dyn_ftrace;
 struct dyn_arch_ftrace {
-	struct module *mod;
 };
 
 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_ARGS
diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
index 8c3e523e4f96..fe0546fbac8e 100644
--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/arch/powerpc/kernel/trace/ftrace.c
@@ -106,28 +106,43 @@ static unsigned long find_ftrace_tramp(unsigned long ip)
 	return 0;
 }
 
+#ifdef CONFIG_MODULES
+static unsigned long ftrace_lookup_module_stub(unsigned long ip, unsigned long addr)
+{
+	struct module *mod = NULL;
+
+	preempt_disable();
+	mod = __module_text_address(ip);
+	preempt_enable();
+
+	if (!mod)
+		pr_err("No module loaded at addr=%lx\n", ip);
+
+	return (addr == (unsigned long)ftrace_caller ? mod->arch.tramp : mod->arch.tramp_regs);
+}
+#else
+static unsigned long ftrace_lookup_module_stub(unsigned long ip, unsigned long addr)
+{
+	return 0;
+}
+#endif
+
 static int ftrace_get_call_inst(struct dyn_ftrace *rec, unsigned long addr, ppc_inst_t *call_inst)
 {
 	unsigned long ip = rec->ip;
 	unsigned long stub;
 
-	if (is_offset_in_branch_range(addr - ip)) {
+	if (is_offset_in_branch_range(addr - ip))
 		/* Within range */
 		stub = addr;
-#ifdef CONFIG_MODULES
-	} else if (rec->arch.mod) {
-		/* Module code would be going to one of the module stubs */
-		stub = (addr == (unsigned long)ftrace_caller ? rec->arch.mod->arch.tramp :
-							       rec->arch.mod->arch.tramp_regs);
-#endif
-	} else if (core_kernel_text(ip)) {
+	else if (core_kernel_text(ip))
 		/* We would be branching to one of our ftrace stubs */
 		stub = find_ftrace_tramp(ip);
-		if (!stub) {
-			pr_err("0x%lx: No ftrace stubs reachable\n", ip);
-			return -EINVAL;
-		}
-	} else {
+	else
+		stub = ftrace_lookup_module_stub(ip, addr);
+
+	if (!stub) {
+		pr_err("0x%lx: No ftrace stubs reachable\n", ip);
 		return -EINVAL;
 	}
 
@@ -262,14 +277,6 @@ int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
 	if (ret)
 		return ret;
 
-	if (!core_kernel_text(ip)) {
-		if (!mod) {
-			pr_err("0x%lx: No module provided for non-kernel address\n", ip);
-			return -EFAULT;
-		}
-		rec->arch.mod = mod;
-	}
-
 	/* Nop-out the ftrace location */
 	new = ppc_inst(PPC_RAW_NOP());
 	addr = MCOUNT_ADDR;
diff --git a/arch/powerpc/kernel/trace/ftrace_64_pg.c b/arch/powerpc/kernel/trace/ftrace_64_pg.c
index 12fab1803bcf..8a551dfca3d0 100644
--- a/arch/powerpc/kernel/trace/ftrace_64_pg.c
+++ b/arch/powerpc/kernel/trace/ftrace_64_pg.c
@@ -116,6 +116,20 @@ static unsigned long find_bl_target(unsigned long ip, ppc_inst_t op)
 }
 
 #ifdef CONFIG_MODULES
+static struct module *ftrace_lookup_module(struct dyn_ftrace *rec)
+{
+	struct module *mod;
+
+	preempt_disable();
+	mod = __module_text_address(rec->ip);
+	preempt_enable();
+
+	if (!mod)
+		pr_err("No module loaded at addr=%lx\n", rec->ip);
+
+	return mod;
+}
+
 static int
 __ftrace_make_nop(struct module *mod,
 		  struct dyn_ftrace *rec, unsigned long addr)
@@ -124,6 +138,12 @@ __ftrace_make_nop(struct module *mod,
 	unsigned long ip = rec->ip;
 	ppc_inst_t op, pop;
 
+	if (!mod) {
+		mod = ftrace_lookup_module(rec);
+		if (!mod)
+			return -EINVAL;
+	}
+
 	/* read where this goes */
 	if (copy_inst_from_kernel_nofault(&op, (void *)ip)) {
 		pr_err("Fetching opcode failed.\n");
@@ -366,27 +386,6 @@ int ftrace_make_nop(struct module *mod,
 		return -EINVAL;
 	}
 
-	/*
-	 * Out of range jumps are called from modules.
-	 * We should either already have a pointer to the module
-	 * or it has been passed in.
-	 */
-	if (!rec->arch.mod) {
-		if (!mod) {
-			pr_err("No module loaded addr=%lx\n", addr);
-			return -EFAULT;
-		}
-		rec->arch.mod = mod;
-	} else if (mod) {
-		if (mod != rec->arch.mod) {
-			pr_err("Record mod %p not equal to passed in mod %p\n",
-			       rec->arch.mod, mod);
-			return -EINVAL;
-		}
-		/* nothing to do if mod == rec->arch.mod */
-	} else
-		mod = rec->arch.mod;
-
 	return __ftrace_make_nop(mod, rec, addr);
 }
 
@@ -411,7 +410,10 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 	ppc_inst_t op[2];
 	void *ip = (void *)rec->ip;
 	unsigned long entry, ptr, tramp;
-	struct module *mod = rec->arch.mod;
+	struct module *mod = ftrace_lookup_module(rec);
+
+	if (!mod)
+		return -EINVAL;
 
 	/* read where this goes */
 	if (copy_inst_from_kernel_nofault(op, ip))
@@ -533,16 +535,6 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 		return -EINVAL;
 	}
 
-	/*
-	 * Out of range jumps are called from modules.
-	 * Being that we are converting from nop, it had better
-	 * already have a module defined.
-	 */
-	if (!rec->arch.mod) {
-		pr_err("No module loaded\n");
-		return -EINVAL;
-	}
-
 	return __ftrace_make_call(rec, addr);
 }
 
@@ -555,7 +547,10 @@ __ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
 	ppc_inst_t op;
 	unsigned long ip = rec->ip;
 	unsigned long entry, ptr, tramp;
-	struct module *mod = rec->arch.mod;
+	struct module *mod = ftrace_lookup_module(rec);
+
+	if (!mod)
+		return -EINVAL;
 
 	/* If we never set up ftrace trampolines, then bail */
 	if (!mod->arch.tramp || !mod->arch.tramp_regs) {
@@ -668,14 +663,6 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
 		return -EINVAL;
 	}
 
-	/*
-	 * Out of range jumps are called from modules.
-	 */
-	if (!rec->arch.mod) {
-		pr_err("No module loaded\n");
-		return -EINVAL;
-	}
-
 	return __ftrace_modify_call(rec, old_addr, addr);
 }
 #endif
-- 
2.45.2

[RFC PATCH v4 07/17] powerpc/ftrace: Skip instruction patching if the instructions are the same

[Naveen N Rao]

To simplify upcoming changes to ftrace, add a check to skip actual
instruction patching if the old and new instructions are the same. We
still validate that the instruction is what we expect, but don't
actually patch the same instruction again.

Signed-off-by: Naveen N Rao <naveen@kernel.org>
---
 arch/powerpc/kernel/trace/ftrace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
index fe0546fbac8e..719517265d39 100644
--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/arch/powerpc/kernel/trace/ftrace.c
@@ -82,7 +82,7 @@ static inline int ftrace_modify_code(unsigned long ip, ppc_inst_t old, ppc_inst_
 {
 	int ret = ftrace_validate_inst(ip, old);
 
-	if (!ret)
+	if (!ret && !ppc_inst_equal(old, new))
 		ret = patch_instruction((u32 *)ip, new);
 
 	return ret;
-- 
2.45.2

[RFC PATCH v4 08/17] powerpc/ftrace: Move ftrace stub used for init text before _einittext

[Naveen N Rao]

Move the ftrace stub used to cover inittext before _einittext so that it
is within kernel text, as seen through core_kernel_text(). This is
required for a subsequent change to ftrace.

Signed-off-by: Naveen N Rao <naveen@kernel.org>
---
 arch/powerpc/kernel/vmlinux.lds.S | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index f420df7888a7..0aef9959f2cd 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -267,14 +267,13 @@ SECTIONS
 	.init.text : AT(ADDR(.init.text) - LOAD_OFFSET) {
 		_sinittext = .;
 		INIT_TEXT
-
+		*(.tramp.ftrace.init);
 		/*
 		 *.init.text might be RO so we must ensure this section ends on
 		 * a page boundary.
 		 */
 		. = ALIGN(PAGE_SIZE);
 		_einittext = .;
-		*(.tramp.ftrace.init);
 	} :text
 
 	/* .exit.text is discarded at runtime, not link time,
-- 
2.45.2

Re: [RFC PATCH v4 08/17] powerpc/ftrace: Move ftrace stub used for init text before _einittext

[Nicholas Piggin]

On Sun Jul 14, 2024 at 6:27 PM AEST, Naveen N Rao wrote:
> Move the ftrace stub used to cover inittext before _einittext so that it
> is within kernel text, as seen through core_kernel_text(). This is
> required for a subsequent change to ftrace.

Hmm, is there a reason it was outside einittext anyway?

Does it do anything else? Other than symbols, on some 32-bit platforms
it looks like it could change some of the initial mapping/pinning. Maybe
they jut get lucky and always map it before the change anyway?

It looks like the right thing to do even without the subsequent ftrace
change though.

Thanks,
Nick

>
> Signed-off-by: Naveen N Rao <naveen@kernel.org>
> ---
>  arch/powerpc/kernel/vmlinux.lds.S | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
> index f420df7888a7..0aef9959f2cd 100644
> --- a/arch/powerpc/kernel/vmlinux.lds.S
> +++ b/arch/powerpc/kernel/vmlinux.lds.S
> @@ -267,14 +267,13 @@ SECTIONS
>  	.init.text : AT(ADDR(.init.text) - LOAD_OFFSET) {
>  		_sinittext = .;
>  		INIT_TEXT
> -
> +		*(.tramp.ftrace.init);
>  		/*
>  		 *.init.text might be RO so we must ensure this section ends on
>  		 * a page boundary.
>  		 */
>  		. = ALIGN(PAGE_SIZE);
>  		_einittext = .;
> -		*(.tramp.ftrace.init);
>  	} :text
>  
>  	/* .exit.text is discarded at runtime, not link time,

[RFC PATCH v4 09/17] powerpc64/bpf: Fold bpf_jit_emit_func_call_hlp() into bpf_jit_emit_func_call_rel()

[Naveen N Rao]

Commit 61688a82e047 ("powerpc/bpf: enable kfunc call") enhanced
bpf_jit_emit_func_call_hlp() to handle calls out to module region, where
bpf progs are generated. The only difference now between
bpf_jit_emit_func_call_hlp() and bpf_jit_emit_func_call_rel() is in
handling of the initial pass where target function address is not known.
Fold that logic into bpf_jit_emit_func_call_hlp() and rename it to
bpf_jit_emit_func_call_rel() to simplify bpf function call JIT code.

We don't actually need to load/restore TOC across a call out to a
different kernel helper or to a different bpf program since they all
work with the kernel TOC. We only need to do it if we have to call out
to a module function. So, guard TOC load/restore with appropriate
conditions.

Signed-off-by: Naveen N Rao <naveen@kernel.org>
---
 arch/powerpc/net/bpf_jit_comp64.c | 61 +++++++++----------------------
 1 file changed, 17 insertions(+), 44 deletions(-)

diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
index 2cbcdf93cc19..f3be024fc685 100644
--- a/arch/powerpc/net/bpf_jit_comp64.c
+++ b/arch/powerpc/net/bpf_jit_comp64.c
@@ -202,14 +202,22 @@ void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx)
 	EMIT(PPC_RAW_BLR());
 }
 
-static int
-bpf_jit_emit_func_call_hlp(u32 *image, u32 *fimage, struct codegen_context *ctx, u64 func)
+int bpf_jit_emit_func_call_rel(u32 *image, u32 *fimage, struct codegen_context *ctx, u64 func)
 {
 	unsigned long func_addr = func ? ppc_function_entry((void *)func) : 0;
 	long reladdr;
 
-	if (WARN_ON_ONCE(!kernel_text_address(func_addr)))
-		return -EINVAL;
+	/* bpf to bpf call, func is not known in the initial pass. Emit 5 nops as a placeholder */
+	if (!func) {
+		for (int i = 0; i < 5; i++)
+			EMIT(PPC_RAW_NOP());
+		/* elfv1 needs an additional instruction to load addr from descriptor */
+		if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V1))
+			EMIT(PPC_RAW_NOP());
+		EMIT(PPC_RAW_MTCTR(_R12));
+		EMIT(PPC_RAW_BCTRL());
+		return 0;
+	}
 
 #ifdef CONFIG_PPC_KERNEL_PCREL
 	reladdr = func_addr - local_paca->kernelbase;
@@ -266,7 +274,8 @@ bpf_jit_emit_func_call_hlp(u32 *image, u32 *fimage, struct codegen_context *ctx,
 			 * We can clobber r2 since we get called through a
 			 * function pointer (so caller will save/restore r2).
 			 */
-			EMIT(PPC_RAW_LD(_R2, bpf_to_ppc(TMP_REG_2), 8));
+			if (is_module_text_address(func_addr))
+				EMIT(PPC_RAW_LD(_R2, bpf_to_ppc(TMP_REG_2), 8));
 		} else {
 			PPC_LI64(_R12, func);
 			EMIT(PPC_RAW_MTCTR(_R12));
@@ -276,46 +285,14 @@ bpf_jit_emit_func_call_hlp(u32 *image, u32 *fimage, struct codegen_context *ctx,
 		 * Load r2 with kernel TOC as kernel TOC is used if function address falls
 		 * within core kernel text.
 		 */
-		EMIT(PPC_RAW_LD(_R2, _R13, offsetof(struct paca_struct, kernel_toc)));
+		if (is_module_text_address(func_addr))
+			EMIT(PPC_RAW_LD(_R2, _R13, offsetof(struct paca_struct, kernel_toc)));
 	}
 #endif
 
 	return 0;
 }
 
-int bpf_jit_emit_func_call_rel(u32 *image, u32 *fimage, struct codegen_context *ctx, u64 func)
-{
-	unsigned int i, ctx_idx = ctx->idx;
-
-	if (WARN_ON_ONCE(func && is_module_text_address(func)))
-		return -EINVAL;
-
-	/* skip past descriptor if elf v1 */
-	func += FUNCTION_DESCR_SIZE;
-
-	/* Load function address into r12 */
-	PPC_LI64(_R12, func);
-
-	/* For bpf-to-bpf function calls, the callee's address is unknown
-	 * until the last extra pass. As seen above, we use PPC_LI64() to
-	 * load the callee's address, but this may optimize the number of
-	 * instructions required based on the nature of the address.
-	 *
-	 * Since we don't want the number of instructions emitted to increase,
-	 * we pad the optimized PPC_LI64() call with NOPs to guarantee that
-	 * we always have a five-instruction sequence, which is the maximum
-	 * that PPC_LI64() can emit.
-	 */
-	if (!image)
-		for (i = ctx->idx - ctx_idx; i < 5; i++)
-			EMIT(PPC_RAW_NOP());
-
-	EMIT(PPC_RAW_MTCTR(_R12));
-	EMIT(PPC_RAW_BCTRL());
-
-	return 0;
-}
-
 static int bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32 out)
 {
 	/*
@@ -1102,11 +1079,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, u32 *fimage, struct code
 			if (ret < 0)
 				return ret;
 
-			if (func_addr_fixed)
-				ret = bpf_jit_emit_func_call_hlp(image, fimage, ctx, func_addr);
-			else
-				ret = bpf_jit_emit_func_call_rel(image, fimage, ctx, func_addr);
-
+			ret = bpf_jit_emit_func_call_rel(image, fimage, ctx, func_addr);
 			if (ret)
 				return ret;
 
-- 
2.45.2

[RFC PATCH v4 10/17] powerpc/ftrace: Add a postlink script to validate function tracer

[Naveen N Rao]

Function tracer on powerpc can only work with vmlinux having a .text
size of up to ~64MB due to powerpc branch instruction having a limited
relative branch range of 32MB. Today, this is only detected on kernel
boot when ftrace is init'ed. Add a post-link script to check the size of
.text so that we can detect this at build time, and break the build if
necessary.

We add a dependency on !COMPILE_TEST for CONFIG_HAVE_FUNCTION_TRACER so
that allyesconfig and other test builds can continue to work without
enabling ftrace.

Signed-off-by: Naveen N Rao <naveen@kernel.org>
---
 arch/powerpc/Kconfig               |  2 +-
 arch/powerpc/Makefile.postlink     |  8 ++++++
 arch/powerpc/tools/ftrace_check.sh | 45 ++++++++++++++++++++++++++++++
 3 files changed, 54 insertions(+), 1 deletion(-)
 create mode 100755 arch/powerpc/tools/ftrace_check.sh

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index f8891fbe7c16..68f0e7a5576f 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -244,7 +244,7 @@ config PPC
 	select HAVE_FUNCTION_DESCRIPTORS	if PPC64_ELF_ABI_V1
 	select HAVE_FUNCTION_ERROR_INJECTION
 	select HAVE_FUNCTION_GRAPH_TRACER
-	select HAVE_FUNCTION_TRACER		if PPC64 || (PPC32 && CC_IS_GCC)
+	select HAVE_FUNCTION_TRACER		if !COMPILE_TEST && (PPC64 || (PPC32 && CC_IS_GCC))
 	select HAVE_GCC_PLUGINS			if GCC_VERSION >= 50200   # plugin support on gcc <= 5.1 is buggy on PPC
 	select HAVE_GENERIC_VDSO
 	select HAVE_HARDLOCKUP_DETECTOR_ARCH	if PPC_BOOK3S_64 && SMP
diff --git a/arch/powerpc/Makefile.postlink b/arch/powerpc/Makefile.postlink
index ae5a4256b03d..bb601be36173 100644
--- a/arch/powerpc/Makefile.postlink
+++ b/arch/powerpc/Makefile.postlink
@@ -24,6 +24,9 @@ else
 	$(CONFIG_SHELL) $(srctree)/arch/powerpc/tools/relocs_check.sh "$(OBJDUMP)" "$(NM)" "$@"
 endif
 
+quiet_cmd_ftrace_check = CHKFTRC $@
+      cmd_ftrace_check = $(CONFIG_SHELL) $(srctree)/arch/powerpc/tools/ftrace_check.sh "$(NM)" "$@"
+
 # `@true` prevents complaint when there is nothing to be done
 
 vmlinux: FORCE
@@ -34,6 +37,11 @@ endif
 ifdef CONFIG_RELOCATABLE
 	$(call if_changed,relocs_check)
 endif
+ifdef CONFIG_FUNCTION_TRACER
+ifndef CONFIG_PPC64_ELF_ABI_V1
+	$(call cmd,ftrace_check)
+endif
+endif
 
 clean:
 	rm -f .tmp_symbols.txt
diff --git a/arch/powerpc/tools/ftrace_check.sh b/arch/powerpc/tools/ftrace_check.sh
new file mode 100755
index 000000000000..33f2fd45e54d
--- /dev/null
+++ b/arch/powerpc/tools/ftrace_check.sh
@@ -0,0 +1,45 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0-or-later
+#
+# This script checks vmlinux to ensure that all functions can call ftrace_caller() either directly,
+# or through the stub, ftrace_tramp_text, at the end of kernel text.
+
+# Error out if any command fails
+set -e
+
+# Allow for verbose output
+if [ "$V" = "1" ]; then
+	set -x
+fi
+
+if [ $# -lt 2 ]; then
+	echo "$0 [path to nm] [path to vmlinux]" 1>&2
+	exit 1
+fi
+
+# Have Kbuild supply the path to nm so we handle cross compilation.
+nm="$1"
+vmlinux="$2"
+
+stext_addr=$($nm "$vmlinux" | grep -e " [TA] _stext$" | cut -d' ' -f1 | tr '[[:lower:]]' '[[:upper:]]')
+ftrace_caller_addr=$($nm "$vmlinux" | grep -e " T ftrace_caller$" | cut -d' ' -f1 | tr '[[:lower:]]' '[[:upper:]]')
+ftrace_tramp_addr=$($nm "$vmlinux" | grep -e " T ftrace_tramp_text$" | cut -d' ' -f1 | tr '[[:lower:]]' '[[:upper:]]')
+
+ftrace_caller_offset=$(echo "ibase=16;$ftrace_caller_addr - $stext_addr" | bc)
+ftrace_tramp_offset=$(echo "ibase=16;$ftrace_tramp_addr - $ftrace_caller_addr" | bc)
+sz_32m=$(printf "%d" 0x2000000)
+sz_64m=$(printf "%d" 0x4000000)
+
+# ftrace_caller - _stext < 32M
+if [ $ftrace_caller_offset -ge $sz_32m ]; then
+	echo "ERROR: ftrace_caller (0x$ftrace_caller_addr) is beyond 32MiB of _stext" 1>&2
+	echo "ERROR: consider disabling CONFIG_FUNCTION_TRACER, or reducing the size of kernel text" 1>&2
+	exit 1
+fi
+
+# ftrace_tramp_text - ftrace_caller < 64M
+if [ $ftrace_tramp_offset -ge $sz_64m ]; then
+	echo "ERROR: kernel text extends beyond 64MiB from ftrace_caller" 1>&2
+	echo "ERROR: consider disabling CONFIG_FUNCTION_TRACER, or reducing the size of kernel text" 1>&2
+	exit 1
+fi
-- 
2.45.2

[RFC PATCH v4 11/17] kbuild: Add generic hook for architectures to use before the final vmlinux link

[Naveen N Rao]

On powerpc, we would like to be able to make a pass on vmlinux.o and
generate a new object file to be linked into vmlinux. Add a generic pass
in Makefile.vmlinux that architectures can use for this purpose.

Architectures need to select CONFIG_ARCH_WANTS_PRE_LINK_VMLINUX and must
provide arch/<arch>/tools/Makefile with .arch.vmlinux.o target, which
will be invoked prior to the final vmlinux link step.

Signed-off-by: Naveen N Rao <naveen@kernel.org>
---
 arch/Kconfig             |  6 ++++++
 scripts/Makefile.vmlinux |  8 ++++++++
 scripts/link-vmlinux.sh  | 11 ++++++++---
 3 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 975dd22a2dbd..ef868ff8156a 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -1643,4 +1643,10 @@ config CC_HAS_SANE_FUNCTION_ALIGNMENT
 config ARCH_NEED_CMPXCHG_1_EMU
 	bool
 
+config ARCH_WANTS_PRE_LINK_VMLINUX
+	def_bool n
+	help
+	  An architecture can select this if it provides arch/<arch>/tools/Makefile
+	  with .arch.vmlinux.o target to be linked into vmlinux.
+
 endmenu
diff --git a/scripts/Makefile.vmlinux b/scripts/Makefile.vmlinux
index 49946cb96844..6410e0be7f52 100644
--- a/scripts/Makefile.vmlinux
+++ b/scripts/Makefile.vmlinux
@@ -22,6 +22,14 @@ targets += .vmlinux.export.o
 vmlinux: .vmlinux.export.o
 endif
 
+ifdef CONFIG_ARCH_WANTS_PRE_LINK_VMLINUX
+targets += .arch.vmlinux.o
+.arch.vmlinux.o: vmlinux.o FORCE
+	$(Q)$(MAKE) $(build)=arch/$(SRCARCH)/tools .arch.vmlinux.o
+
+vmlinux: .arch.vmlinux.o
+endif
+
 ARCH_POSTLINK := $(wildcard $(srctree)/arch/$(SRCARCH)/Makefile.postlink)
 
 # Final link of vmlinux with optional arch pass after final link
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index 518c70b8db50..aafaed1412ea 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -122,7 +122,7 @@ gen_btf()
 		return 1
 	fi
 
-	vmlinux_link ${1}
+	vmlinux_link ${1} ${arch_vmlinux_o}
 
 	info "BTF" ${2}
 	LLVM_OBJCOPY="${OBJCOPY}" ${PAHOLE} -J ${PAHOLE_FLAGS} ${1}
@@ -178,7 +178,7 @@ kallsyms_step()
 	kallsymso=${kallsyms_vmlinux}.o
 	kallsyms_S=${kallsyms_vmlinux}.S
 
-	vmlinux_link ${kallsyms_vmlinux} "${kallsymso_prev}" ${btf_vmlinux_bin_o}
+	vmlinux_link ${kallsyms_vmlinux} "${kallsymso_prev}" ${btf_vmlinux_bin_o} ${arch_vmlinux_o}
 	mksysmap ${kallsyms_vmlinux} ${kallsyms_vmlinux}.syms
 	kallsyms ${kallsyms_vmlinux}.syms ${kallsyms_S}
 
@@ -223,6 +223,11 @@ fi
 
 ${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init init/version-timestamp.o
 
+arch_vmlinux_o=""
+if is_enabled CONFIG_ARCH_WANTS_PRE_LINK_VMLINUX; then
+	arch_vmlinux_o=.arch.vmlinux.o
+fi
+
 btf_vmlinux_bin_o=""
 if is_enabled CONFIG_DEBUG_INFO_BTF; then
 	btf_vmlinux_bin_o=.btf.vmlinux.bin.o
@@ -273,7 +278,7 @@ if is_enabled CONFIG_KALLSYMS; then
 	fi
 fi
 
-vmlinux_link vmlinux "${kallsymso}" ${btf_vmlinux_bin_o}
+vmlinux_link vmlinux "${kallsymso}" ${btf_vmlinux_bin_o} ${arch_vmlinux_o}
 
 # fill in BTF IDs
 if is_enabled CONFIG_DEBUG_INFO_BTF && is_enabled CONFIG_BPF; then
-- 
2.45.2

Re: [RFC PATCH v4 11/17] kbuild: Add generic hook for architectures to use before the final vmlinux link

[Nicholas Piggin]

On Sun Jul 14, 2024 at 6:27 PM AEST, Naveen N Rao wrote:
> On powerpc, we would like to be able to make a pass on vmlinux.o and
> generate a new object file to be linked into vmlinux. Add a generic pass
> in Makefile.vmlinux that architectures can use for this purpose.
>
> Architectures need to select CONFIG_ARCH_WANTS_PRE_LINK_VMLINUX and must
> provide arch/<arch>/tools/Makefile with .arch.vmlinux.o target, which
> will be invoked prior to the final vmlinux link step.

Maybe POSTLINK should move to more like this with explicit config
option too rather than just picking up Makefile.postlink...

>
> Signed-off-by: Naveen N Rao <naveen@kernel.org>
> ---
>  arch/Kconfig             |  6 ++++++
>  scripts/Makefile.vmlinux |  8 ++++++++
>  scripts/link-vmlinux.sh  | 11 ++++++++---
>  3 files changed, 22 insertions(+), 3 deletions(-)
>
> diff --git a/arch/Kconfig b/arch/Kconfig
> index 975dd22a2dbd..ef868ff8156a 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -1643,4 +1643,10 @@ config CC_HAS_SANE_FUNCTION_ALIGNMENT
>  config ARCH_NEED_CMPXCHG_1_EMU
>  	bool
>  
> +config ARCH_WANTS_PRE_LINK_VMLINUX
> +	def_bool n
> +	help
> +	  An architecture can select this if it provides arch/<arch>/tools/Makefile
> +	  with .arch.vmlinux.o target to be linked into vmlinux.

Someone bikeshedded me before for putting comments for putting comment
for non-user-selectable option in 'help'. Even though heaps of options
are like that here, apparently they preferred # comment above the option
for developer comments. I personally thought this looks nicer but do
Kconfig maintainers prefer #?

> +
>  endmenu
> diff --git a/scripts/Makefile.vmlinux b/scripts/Makefile.vmlinux
> index 49946cb96844..6410e0be7f52 100644
> --- a/scripts/Makefile.vmlinux
> +++ b/scripts/Makefile.vmlinux
> @@ -22,6 +22,14 @@ targets += .vmlinux.export.o
>  vmlinux: .vmlinux.export.o
>  endif
>  
> +ifdef CONFIG_ARCH_WANTS_PRE_LINK_VMLINUX
> +targets += .arch.vmlinux.o
> +.arch.vmlinux.o: vmlinux.o FORCE
> +	$(Q)$(MAKE) $(build)=arch/$(SRCARCH)/tools .arch.vmlinux.o
> +
> +vmlinux: .arch.vmlinux.o
> +endif

Does .vmlinux.arch.o follow convention better? I guess the btf does
not. So, nevermind.

Could this just be done entirely in link-vmlinux.sh like kallsyms and
btf?

> +
>  ARCH_POSTLINK := $(wildcard $(srctree)/arch/$(SRCARCH)/Makefile.postlink)
>  
>  # Final link of vmlinux with optional arch pass after final link
> diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
> index 518c70b8db50..aafaed1412ea 100755
> --- a/scripts/link-vmlinux.sh
> +++ b/scripts/link-vmlinux.sh
> @@ -122,7 +122,7 @@ gen_btf()
>  		return 1
>  	fi
>  
> -	vmlinux_link ${1}
> +	vmlinux_link ${1} ${arch_vmlinux_o}
>  
>  	info "BTF" ${2}
>  	LLVM_OBJCOPY="${OBJCOPY}" ${PAHOLE} -J ${PAHOLE_FLAGS} ${1}

BTF generation needs  the prelink .o?

> @@ -178,7 +178,7 @@ kallsyms_step()
>  	kallsymso=${kallsyms_vmlinux}.o
>  	kallsyms_S=${kallsyms_vmlinux}.S
>  
> -	vmlinux_link ${kallsyms_vmlinux} "${kallsymso_prev}" ${btf_vmlinux_bin_o}
> +	vmlinux_link ${kallsyms_vmlinux} "${kallsymso_prev}" ${btf_vmlinux_bin_o} ${arch_vmlinux_o}
>  	mksysmap ${kallsyms_vmlinux} ${kallsyms_vmlinux}.syms
>  	kallsyms ${kallsyms_vmlinux}.syms ${kallsyms_S}
>  

> @@ -223,6 +223,11 @@ fi
>  
>  ${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init init/version-timestamp.o
>  
> +arch_vmlinux_o=""
> +if is_enabled CONFIG_ARCH_WANTS_PRE_LINK_VMLINUX; then
> +	arch_vmlinux_o=.arch.vmlinux.o
> +fi
> +
>  btf_vmlinux_bin_o=""
>  if is_enabled CONFIG_DEBUG_INFO_BTF; then
>  	btf_vmlinux_bin_o=.btf.vmlinux.bin.o
> @@ -273,7 +278,7 @@ if is_enabled CONFIG_KALLSYMS; then
>  	fi
>  fi
>  
> -vmlinux_link vmlinux "${kallsymso}" ${btf_vmlinux_bin_o}
> +vmlinux_link vmlinux "${kallsymso}" ${btf_vmlinux_bin_o} ${arch_vmlinux_o}
>  
>  # fill in BTF IDs
>  if is_enabled CONFIG_DEBUG_INFO_BTF && is_enabled CONFIG_BPF; then

I guess it looks okay, similar to btf although I'm not a kbuild expert.

Thanks,
Nick

[RFC PATCH v4 12/17] powerpc64/ftrace: Move ftrace sequence out of line

[Naveen N Rao]

Function profile sequence on powerpc includes two instructions at the
beginning of each function:
	mflr	r0
	bl	ftrace_caller

The call to ftrace_caller() gets nop'ed out during kernel boot and is
patched in when ftrace is enabled.

Given the sequence, we cannot return from ftrace_caller with 'blr' as we
need to keep LR and r0 intact. This results in link stack (return
address predictor) imbalance when ftrace is enabled. To address that, we
would like to use a three instruction sequence:
	mflr	r0
	bl	ftrace_caller
	mtlr	r0

Further more, to support DYNAMIC_FTRACE_WITH_CALL_OPS, we need to
reserve two instruction slots before the function. This results in a
total of five instruction slots to be reserved for ftrace use on each
function that is traced.

Move the function profile sequence out-of-line to minimize its impact.
To do this, we reserve a single nop at function entry using
-fpatchable-function-entry=1 and add a pass on vmlinux.o to determine
the total number of functions that can be traced. This is then used to
generate a .S file reserving the appropriate amount of space for use as
ftrace stubs, which is built and linked into vmlinux.

On bootup, the stub space is split into separate stubs per function and
populated with the proper instruction sequence. A pointer to the
associated stub is maintained in dyn_arch_ftrace.

For modules, space for ftrace stubs is reserved from the generic module
stub space.

This is restricted to and enabled by default only on 64-bit powerpc,
though there are some changes to accommodate 32-bit powerpc. This is
done so that 32-bit powerpc could choose to opt into this based on
further tests and benchmarks.

As an example, after this patch, kernel functions will have a single nop
at function entry:
<kernel_clone>:
	addis	r2,r12,467
	addi	r2,r2,-16028
	nop
	mfocrf	r11,8
	...

When ftrace is enabled, the nop is converted to an unconditional branch
to the stub associated with that function:
<kernel_clone>:
	addis	r2,r12,467
	addi	r2,r2,-16028
	b	ftrace_ool_stub_text_end+0x11b28
	mfocrf	r11,8
	...

The associated stub:
<ftrace_ool_stub_text_end+0x11b28>:
	mflr	r0
	bl	ftrace_caller
	mtlr	r0
	b	kernel_clone+0xc
	...

Signed-off-by: Naveen N Rao <naveen@kernel.org>
---
 arch/powerpc/Kconfig                       |   5 +
 arch/powerpc/Makefile                      |   4 +
 arch/powerpc/include/asm/ftrace.h          |  11 ++
 arch/powerpc/include/asm/module.h          |   5 +
 arch/powerpc/kernel/asm-offsets.c          |   4 +
 arch/powerpc/kernel/module_64.c            |  58 +++++++-
 arch/powerpc/kernel/trace/ftrace.c         | 157 +++++++++++++++++++--
 arch/powerpc/kernel/trace/ftrace_entry.S   | 116 +++++++++++----
 arch/powerpc/tools/Makefile                |  10 ++
 arch/powerpc/tools/ftrace-gen-ool-stubs.sh |  48 +++++++
 10 files changed, 381 insertions(+), 37 deletions(-)
 create mode 100644 arch/powerpc/tools/Makefile
 create mode 100755 arch/powerpc/tools/ftrace-gen-ool-stubs.sh

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 68f0e7a5576f..f50cfd15bb73 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -568,6 +568,11 @@ config ARCH_USING_PATCHABLE_FUNCTION_ENTRY
 	def_bool $(success,$(srctree)/arch/powerpc/tools/gcc-check-fpatchable-function-entry.sh $(CC) -mlittle-endian) if PPC64 && CPU_LITTLE_ENDIAN
 	def_bool $(success,$(srctree)/arch/powerpc/tools/gcc-check-fpatchable-function-entry.sh $(CC) -mbig-endian) if PPC64 && CPU_BIG_ENDIAN
 
+config PPC_FTRACE_OUT_OF_LINE
+	def_bool PPC64 && ARCH_USING_PATCHABLE_FUNCTION_ENTRY
+	depends on PPC64
+	select ARCH_WANTS_PRE_LINK_VMLINUX
+
 config HOTPLUG_CPU
 	bool "Support for enabling/disabling CPUs"
 	depends on SMP && (PPC_PSERIES || \
diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index bbfe4a1f06ef..c973e6cd1ae8 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -155,7 +155,11 @@ CC_FLAGS_NO_FPU		:= $(call cc-option,-msoft-float)
 ifdef CONFIG_FUNCTION_TRACER
 ifdef CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY
 KBUILD_CPPFLAGS	+= -DCC_USING_PATCHABLE_FUNCTION_ENTRY
+ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
+CC_FLAGS_FTRACE := -fpatchable-function-entry=1
+else
 CC_FLAGS_FTRACE := -fpatchable-function-entry=2
+endif
 else
 CC_FLAGS_FTRACE := -pg
 ifdef CONFIG_MPROFILE_KERNEL
diff --git a/arch/powerpc/include/asm/ftrace.h b/arch/powerpc/include/asm/ftrace.h
index 201f9d15430a..0589bb252de7 100644
--- a/arch/powerpc/include/asm/ftrace.h
+++ b/arch/powerpc/include/asm/ftrace.h
@@ -26,6 +26,10 @@ unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip,
 struct module;
 struct dyn_ftrace;
 struct dyn_arch_ftrace {
+#ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
+	/* pointer to the associated out-of-line stub */
+	unsigned long ool_stub;
+#endif
 };
 
 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_ARGS
@@ -132,6 +136,13 @@ static inline u8 this_cpu_get_ftrace_enabled(void) { return 1; }
 
 #ifdef CONFIG_FUNCTION_TRACER
 extern unsigned int ftrace_tramp_text[], ftrace_tramp_init[];
+#ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
+struct ftrace_ool_stub {
+	u32	insn[4];
+};
+extern struct ftrace_ool_stub ftrace_ool_stub_text_end[], ftrace_ool_stub_inittext[];
+extern unsigned int ftrace_ool_stub_text_end_count, ftrace_ool_stub_inittext_count;
+#endif
 void ftrace_free_init_tramp(void);
 unsigned long ftrace_call_adjust(unsigned long addr);
 #else
diff --git a/arch/powerpc/include/asm/module.h b/arch/powerpc/include/asm/module.h
index 300c777cc307..9ee70a4a0fde 100644
--- a/arch/powerpc/include/asm/module.h
+++ b/arch/powerpc/include/asm/module.h
@@ -47,6 +47,11 @@ struct mod_arch_specific {
 #ifdef CONFIG_DYNAMIC_FTRACE
 	unsigned long tramp;
 	unsigned long tramp_regs;
+#ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
+	struct ftrace_ool_stub *ool_stubs;
+	unsigned int ool_stub_count;
+	unsigned int ool_stub_index;
+#endif
 #endif
 };
 
diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index 23733282de4d..6854547d3164 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -674,5 +674,9 @@ int main(void)
 	DEFINE(BPT_SIZE, BPT_SIZE);
 #endif
 
+#ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
+	DEFINE(FTRACE_OOL_STUB_SIZE, sizeof(struct ftrace_ool_stub));
+#endif
+
 	return 0;
 }
diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
index 1db88409bd95..6816e9967cab 100644
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -205,7 +205,9 @@ static int relacmp(const void *_x, const void *_y)
 
 /* Get size of potential trampolines required. */
 static unsigned long get_stubs_size(const Elf64_Ehdr *hdr,
-				    const Elf64_Shdr *sechdrs)
+				    const Elf64_Shdr *sechdrs,
+				    char *secstrings,
+				    struct module *me)
 {
 	/* One extra reloc so it's always 0-addr terminated */
 	unsigned long relocs = 1;
@@ -244,6 +246,24 @@ static unsigned long get_stubs_size(const Elf64_Ehdr *hdr,
 	/* stubs for ftrace_caller and ftrace_regs_caller */
 	relocs += IS_ENABLED(CONFIG_DYNAMIC_FTRACE) + IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS);
 
+#ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
+	/* stubs for the function tracer */
+	for (i = 1; i < hdr->e_shnum; i++) {
+		if (!strcmp(secstrings + sechdrs[i].sh_name, "__patchable_function_entries")) {
+			me->arch.ool_stub_count = sechdrs[i].sh_size / sizeof(unsigned long);
+			me->arch.ool_stub_index = 0;
+			relocs += roundup(me->arch.ool_stub_count * sizeof(struct ftrace_ool_stub),
+					  sizeof(struct ppc64_stub_entry)) /
+				  sizeof(struct ppc64_stub_entry);
+			break;
+		}
+	}
+	if (i == hdr->e_shnum) {
+		pr_err("%s: doesn't contain __patchable_function_entries.\n", me->name);
+		return -ENOEXEC;
+	}
+#endif
+
 	pr_debug("Looks like a total of %lu stubs, max\n", relocs);
 	return relocs * sizeof(struct ppc64_stub_entry);
 }
@@ -454,7 +474,7 @@ int module_frob_arch_sections(Elf64_Ehdr *hdr,
 #endif
 
 	/* Override the stubs size */
-	sechdrs[me->arch.stubs_section].sh_size = get_stubs_size(hdr, sechdrs);
+	sechdrs[me->arch.stubs_section].sh_size = get_stubs_size(hdr, sechdrs, secstrings, me);
 
 	return 0;
 }
@@ -1079,6 +1099,37 @@ int module_trampoline_target(struct module *mod, unsigned long addr,
 	return 0;
 }
 
+static int setup_ftrace_ool_stubs(const Elf64_Shdr *sechdrs, unsigned long addr, struct module *me)
+{
+#ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
+	unsigned int i, total_stubs, num_stubs;
+	struct ppc64_stub_entry *stub;
+
+	total_stubs = sechdrs[me->arch.stubs_section].sh_size / sizeof(*stub);
+	num_stubs = roundup(me->arch.ool_stub_count * sizeof(struct ftrace_ool_stub),
+			    sizeof(struct ppc64_stub_entry)) / sizeof(struct ppc64_stub_entry);
+
+	/* Find the next available entry */
+	stub = (void *)sechdrs[me->arch.stubs_section].sh_addr;
+	for (i = 0; stub_func_addr(stub[i].funcdata); i++)
+		if (WARN_ON(i >= total_stubs))
+			return -1;
+
+	if (WARN_ON(i + num_stubs > total_stubs))
+		return -1;
+
+	stub += i;
+	me->arch.ool_stubs = (struct ftrace_ool_stub *)stub;
+
+	/* reserve stubs */
+	for (i = 0; i < num_stubs; i++)
+		if (patch_u32((void *)&stub->funcdata, PPC_RAW_NOP()))
+			return -1;
+#endif
+
+	return 0;
+}
+
 int module_finalize_ftrace(struct module *mod, const Elf_Shdr *sechdrs)
 {
 	mod->arch.tramp = stub_for_addr(sechdrs,
@@ -1097,6 +1148,9 @@ int module_finalize_ftrace(struct module *mod, const Elf_Shdr *sechdrs)
 	if (!mod->arch.tramp)
 		return -ENOENT;
 
+	if (setup_ftrace_ool_stubs(sechdrs, mod->arch.tramp, mod))
+		return -ENOENT;
+
 	return 0;
 }
 #endif
diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
index 719517265d39..c03336301bad 100644
--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/arch/powerpc/kernel/trace/ftrace.c
@@ -37,7 +37,8 @@ unsigned long ftrace_call_adjust(unsigned long addr)
 	if (addr >= (unsigned long)__exittext_begin && addr < (unsigned long)__exittext_end)
 		return 0;
 
-	if (IS_ENABLED(CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY))
+	if (IS_ENABLED(CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY) &&
+	    !IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE))
 		addr += MCOUNT_INSN_SIZE;
 
 	return addr;
@@ -127,11 +128,25 @@ static unsigned long ftrace_lookup_module_stub(unsigned long ip, unsigned long a
 }
 #endif
 
+static unsigned long ftrace_get_ool_stub(struct dyn_ftrace *rec)
+{
+#ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
+	return rec->arch.ool_stub;
+#else
+	BUILD_BUG();
+#endif
+}
+
 static int ftrace_get_call_inst(struct dyn_ftrace *rec, unsigned long addr, ppc_inst_t *call_inst)
 {
-	unsigned long ip = rec->ip;
+	unsigned long ip;
 	unsigned long stub;
 
+	if (IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE))
+		ip = ftrace_get_ool_stub(rec) + MCOUNT_INSN_SIZE; /* second instruction in stub */
+	else
+		ip = rec->ip;
+
 	if (is_offset_in_branch_range(addr - ip))
 		/* Within range */
 		stub = addr;
@@ -142,7 +157,7 @@ static int ftrace_get_call_inst(struct dyn_ftrace *rec, unsigned long addr, ppc_
 		stub = ftrace_lookup_module_stub(ip, addr);
 
 	if (!stub) {
-		pr_err("0x%lx: No ftrace stubs reachable\n", ip);
+		pr_err("0x%lx (0x%lx): No ftrace stubs reachable\n", ip, rec->ip);
 		return -EINVAL;
 	}
 
@@ -150,6 +165,87 @@ static int ftrace_get_call_inst(struct dyn_ftrace *rec, unsigned long addr, ppc_
 	return 0;
 }
 
+static int ftrace_init_ool_stub(struct module *mod, struct dyn_ftrace *rec)
+{
+#ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
+	static int ool_stub_text_end_index, ool_stub_inittext_index;
+	int ret = 0, ool_stub_count, *ool_stub_index;
+	ppc_inst_t inst;
+	/*
+	 * See ftrace_entry.S if changing the below instruction sequence, as we rely on
+	 * decoding the last branch instruction here to recover the correct function ip.
+	 */
+	struct ftrace_ool_stub *ool_stub, ool_stub_template = {
+		.insn = {
+			PPC_RAW_MFLR(_R0),
+			PPC_RAW_NOP(),		/* bl ftrace_caller */
+			PPC_RAW_MTLR(_R0),
+			PPC_RAW_NOP()		/* b rec->ip + 4 */
+		}
+	};
+
+	WARN_ON(rec->arch.ool_stub);
+
+	if (is_kernel_inittext(rec->ip)) {
+		ool_stub = ftrace_ool_stub_inittext;
+		ool_stub_index = &ool_stub_inittext_index;
+		ool_stub_count = ftrace_ool_stub_inittext_count;
+	} else if (is_kernel_text(rec->ip)) {
+		ool_stub = ftrace_ool_stub_text_end;
+		ool_stub_index = &ool_stub_text_end_index;
+		ool_stub_count = ftrace_ool_stub_text_end_count;
+#ifdef CONFIG_MODULES
+	} else if (mod) {
+		ool_stub = mod->arch.ool_stubs;
+		ool_stub_index = &mod->arch.ool_stub_index;
+		ool_stub_count = mod->arch.ool_stub_count;
+#endif
+	} else {
+		return -EINVAL;
+	}
+
+	ool_stub += (*ool_stub_index)++;
+
+	if (WARN_ON(*ool_stub_index > ool_stub_count))
+		return -EINVAL;
+
+	if (!is_offset_in_branch_range((long)rec->ip - (long)&ool_stub->insn[0]) ||
+	    !is_offset_in_branch_range((long)(rec->ip + MCOUNT_INSN_SIZE) - (long)&ool_stub->insn[3])) {
+		pr_err("%s: ftrace ool stub out of range (%p -> %p).\n",
+					__func__, (void *)rec->ip, (void *)&ool_stub->insn[0]);
+		return -EINVAL;
+	}
+
+	rec->arch.ool_stub = (unsigned long)&ool_stub->insn[0];
+
+	/* bl ftrace_caller */
+	if (mod)
+		/*
+		 * We can't use ftrace_get_call_inst() since that uses __module_text_address(rec->ip)
+		 * to look up the module. But, since the module is not fully formed at this stage,
+		 * the lookup fails. We know the target though, so generate the branch inst directly.
+		 */
+		inst = ftrace_create_branch_inst(ftrace_get_ool_stub(rec) + MCOUNT_INSN_SIZE,
+						 mod->arch.tramp, 1);
+	else
+		ret = ftrace_get_call_inst(rec, (unsigned long)ftrace_caller, &inst);
+	ool_stub_template.insn[1] = ppc_inst_val(inst);
+
+	/* b rec->ip + 4 */
+	if (!ret && create_branch(&inst, &ool_stub->insn[3], rec->ip + MCOUNT_INSN_SIZE, 0))
+		return -EINVAL;
+	ool_stub_template.insn[3] = ppc_inst_val(inst);
+
+	if (!ret)
+		ret = patch_instructions((u32 *)ool_stub, (u32 *)&ool_stub_template,
+					 sizeof(ool_stub_template), false);
+
+	return ret;
+#else /* !CONFIG_PPC_FTRACE_OUT_OF_LINE */
+	BUILD_BUG();
+#endif
+}
+
 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
 int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, unsigned long addr)
 {
@@ -162,18 +258,29 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, unsigned
 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 {
 	ppc_inst_t old, new;
-	int ret;
+	unsigned long ip = rec->ip;
+	int ret = 0;
 
 	/* This can only ever be called during module load */
-	if (WARN_ON(!IS_ENABLED(CONFIG_MODULES) || core_kernel_text(rec->ip)))
+	if (WARN_ON(!IS_ENABLED(CONFIG_MODULES) || core_kernel_text(ip)))
 		return -EINVAL;
 
 	old = ppc_inst(PPC_RAW_NOP());
-	ret = ftrace_get_call_inst(rec, addr, &new);
-	if (ret)
-		return ret;
+	if (IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE)) {
+		ip = ftrace_get_ool_stub(rec) + MCOUNT_INSN_SIZE; /* second instruction in stub */
+		ret = ftrace_get_call_inst(rec, (unsigned long)ftrace_caller, &old);
+	}
 
-	return ftrace_modify_code(rec->ip, old, new);
+	ret |= ftrace_get_call_inst(rec, addr, &new);
+
+	if (!ret)
+		ret = ftrace_modify_code(ip, old, new);
+
+	if (!ret && IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE))
+		ret = ftrace_modify_code(rec->ip, ppc_inst(PPC_RAW_NOP()),
+			 ppc_inst(PPC_RAW_BRANCH((long)ftrace_get_ool_stub(rec) - (long)rec->ip)));
+
+	return ret;
 }
 
 int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr)
@@ -206,6 +313,13 @@ void ftrace_replace_code(int enable)
 		new_addr = ftrace_get_addr_new(rec);
 		update = ftrace_update_record(rec, enable);
 
+		if (IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE) && update != FTRACE_UPDATE_IGNORE) {
+			ip = ftrace_get_ool_stub(rec) + MCOUNT_INSN_SIZE;
+			ret = ftrace_get_call_inst(rec, (unsigned long)ftrace_caller, &nop_inst);
+			if (ret)
+				goto out;
+		}
+
 		switch (update) {
 		case FTRACE_UPDATE_IGNORE:
 		default:
@@ -230,6 +344,24 @@ void ftrace_replace_code(int enable)
 
 		if (!ret)
 			ret = ftrace_modify_code(ip, old, new);
+
+		if (!ret && IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE) &&
+		    (update == FTRACE_UPDATE_MAKE_NOP || update == FTRACE_UPDATE_MAKE_CALL)) {
+			/* Update the actual ftrace location */
+			call_inst = ppc_inst(PPC_RAW_BRANCH((long)ftrace_get_ool_stub(rec) -
+							    (long)rec->ip));
+			nop_inst = ppc_inst(PPC_RAW_NOP());
+			ip = rec->ip;
+
+			if (update == FTRACE_UPDATE_MAKE_NOP)
+				ret = ftrace_modify_code(ip, call_inst, nop_inst);
+			else
+				ret = ftrace_modify_code(ip, nop_inst, call_inst);
+
+			if (ret)
+				goto out;
+		}
+
 		if (ret)
 			goto out;
 	}
@@ -249,7 +381,8 @@ int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
 	/* Verify instructions surrounding the ftrace location */
 	if (IS_ENABLED(CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY)) {
 		/* Expect nops */
-		ret = ftrace_validate_inst(ip - 4, ppc_inst(PPC_RAW_NOP()));
+		if (!IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE))
+			ret = ftrace_validate_inst(ip - 4, ppc_inst(PPC_RAW_NOP()));
 		if (!ret)
 			ret = ftrace_validate_inst(ip, ppc_inst(PPC_RAW_NOP()));
 	} else if (IS_ENABLED(CONFIG_PPC32)) {
@@ -277,6 +410,10 @@ int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
 	if (ret)
 		return ret;
 
+	/* Set up out-of-line stub */
+	if (IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE))
+		return ftrace_init_ool_stub(mod, rec);
+
 	/* Nop-out the ftrace location */
 	new = ppc_inst(PPC_RAW_NOP());
 	addr = MCOUNT_ADDR;
diff --git a/arch/powerpc/kernel/trace/ftrace_entry.S b/arch/powerpc/kernel/trace/ftrace_entry.S
index 244a1c7bb1e8..71f6a63cd861 100644
--- a/arch/powerpc/kernel/trace/ftrace_entry.S
+++ b/arch/powerpc/kernel/trace/ftrace_entry.S
@@ -56,7 +56,7 @@
 	SAVE_GPR(2, r1)
 	SAVE_GPRS(11, 31, r1)
 	.else
-#ifdef CONFIG_LIVEPATCH_64
+#if defined(CONFIG_LIVEPATCH_64) || defined(CONFIG_PPC_FTRACE_OUT_OF_LINE)
 	SAVE_GPR(14, r1)
 #endif
 	.endif
@@ -78,10 +78,6 @@
 
 	/* Get the _mcount() call site out of LR */
 	mflr	r7
-	/* Save it as pt_regs->nip */
-	PPC_STL	r7, _NIP(r1)
-	/* Also save it in B's stackframe header for proper unwind */
-	PPC_STL	r7, LRSAVE+SWITCH_FRAME_SIZE(r1)
 	/* Save the read LR in pt_regs->link */
 	PPC_STL	r0, _LINK(r1)
 
@@ -96,16 +92,6 @@
 	lwz	r5,function_trace_op@l(r3)
 #endif
 
-#ifdef CONFIG_LIVEPATCH_64
-	mr	r14, r7		/* remember old NIP */
-#endif
-
-	/* Calculate ip from nip-4 into r3 for call below */
-	subi    r3, r7, MCOUNT_INSN_SIZE
-
-	/* Put the original return address in r4 as parent_ip */
-	mr	r4, r0
-
 	/* Save special regs */
 	PPC_STL	r8, _MSR(r1)
 	.if \allregs == 1
@@ -114,17 +100,69 @@
 	PPC_STL	r11, _CCR(r1)
 	.endif
 
+#ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
+	/* Save our real return address in nvr for return */
+	.if \allregs == 0
+	SAVE_GPR(15, r1)
+	.endif
+	mr	r15, r7
+	/*
+	 * We want the ftrace location in the function, but our lr (in r7)
+	 * points at the 'mtlr r0' instruction in the out of line stub.  To
+	 * recover the ftrace location, we read the branch instruction in the
+	 * stub, and adjust our lr by the branch offset.
+	 *
+	 * See ftrace_init_ool_stub() for the profile sequence.
+	 */
+	lwz	r8, MCOUNT_INSN_SIZE(r7)
+	slwi	r8, r8, 6
+	srawi	r8, r8, 6
+	add	r3, r7, r8
+	/*
+	 * Override our nip to point past the branch in the original function.
+	 * This allows reliable stack trace and the ftrace stack tracer to work as-is.
+	 */
+	add	r7, r3, MCOUNT_INSN_SIZE
+#else
+	/* Calculate ip from nip-4 into r3 for call below */
+	subi    r3, r7, MCOUNT_INSN_SIZE
+#endif
+
+	/* Save NIP as pt_regs->nip */
+	PPC_STL	r7, _NIP(r1)
+	/* Also save it in B's stackframe header for proper unwind */
+	PPC_STL	r7, LRSAVE+SWITCH_FRAME_SIZE(r1)
+#if defined(CONFIG_LIVEPATCH_64) || defined(CONFIG_PPC_FTRACE_OUT_OF_LINE)
+	mr	r14, r7		/* remember old NIP */
+#endif
+
+	/* Put the original return address in r4 as parent_ip */
+	mr	r4, r0
+
 	/* Load &pt_regs in r6 for call below */
 	addi    r6, r1, STACK_INT_FRAME_REGS
 .endm
 
 .macro	ftrace_regs_exit allregs
+#ifndef CONFIG_PPC_FTRACE_OUT_OF_LINE
 	/* Load ctr with the possibly modified NIP */
 	PPC_LL	r3, _NIP(r1)
 	mtctr	r3
 
 #ifdef CONFIG_LIVEPATCH_64
 	cmpd	r14, r3		/* has NIP been altered? */
+#endif
+#else /* !CONFIG_PPC_FTRACE_OUT_OF_LINE */
+	/* Load LR with the possibly modified NIP */
+	PPC_LL	r3, _NIP(r1)
+	cmpd	r14, r3		/* has NIP been altered? */
+	bne-	1f
+
+	mr	r3, r15
+	.if \allregs == 0
+	REST_GPR(15, r1)
+	.endif
+1:	mtlr	r3
 #endif
 
 	/* Restore gprs */
@@ -132,14 +170,16 @@
 	REST_GPRS(2, 31, r1)
 	.else
 	REST_GPRS(3, 10, r1)
-#ifdef CONFIG_LIVEPATCH_64
+#if defined(CONFIG_LIVEPATCH_64) || defined(CONFIG_PPC_FTRACE_OUT_OF_LINE)
 	REST_GPR(14, r1)
 #endif
 	.endif
 
 	/* Restore possibly modified LR */
 	PPC_LL	r0, _LINK(r1)
+#ifndef CONFIG_PPC_FTRACE_OUT_OF_LINE
 	mtlr	r0
+#endif
 
 #ifdef CONFIG_PPC64
 	/* Restore callee's TOC */
@@ -153,7 +193,16 @@
         /* Based on the cmpd above, if the NIP was altered handle livepatch */
 	bne-	livepatch_handler
 #endif
-	bctr			/* jump after _mcount site */
+	/* jump after _mcount site */
+#ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
+	/*
+	 * Return with blr to keep the link stack balanced. The function profiling sequence
+	 * uses 'mtlr r0' to restore LR.
+	 */
+	blr
+#else
+	bctr
+#endif
 .endm
 
 _GLOBAL(ftrace_regs_caller)
@@ -177,6 +226,11 @@ _GLOBAL(ftrace_stub)
 
 #ifdef CONFIG_PPC64
 ftrace_no_trace:
+#ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
+	REST_GPR(3, r1)
+	addi	r1, r1, SWITCH_FRAME_SIZE+STACK_FRAME_MIN_SIZE
+	blr
+#else
 	mflr	r3
 	mtctr	r3
 	REST_GPR(3, r1)
@@ -184,6 +238,7 @@ ftrace_no_trace:
 	mtlr	r0
 	bctr
 #endif
+#endif
 
 #ifdef CONFIG_LIVEPATCH_64
 	/*
@@ -194,11 +249,17 @@ ftrace_no_trace:
 	 * We get here when a function A, calls another function B, but B has
 	 * been live patched with a new function C.
 	 *
-	 * On entry:
-	 *  - we have no stack frame and can not allocate one
+	 * On entry, we have no stack frame and can not allocate one.
+	 *
+	 * With PPC_FTRACE_OUT_OF_LINE=n, on entry:
 	 *  - LR points back to the original caller (in A)
 	 *  - CTR holds the new NIP in C
 	 *  - r0, r11 & r12 are free
+	 *
+	 * With PPC_FTRACE_OUT_OF_LINE=y, on entry:
+	 *  - r0 points back to the original caller (in A)
+	 *  - LR holds the new NIP in C
+	 *  - r11 & r12 are free
 	 */
 livepatch_handler:
 	ld	r12, PACA_THREAD_INFO(r13)
@@ -208,18 +269,23 @@ livepatch_handler:
 	addi	r11, r11, 24
 	std	r11, TI_livepatch_sp(r12)
 
-	/* Save toc & real LR on livepatch stack */
-	std	r2,  -24(r11)
-	mflr	r12
-	std	r12, -16(r11)
-
 	/* Store stack end marker */
 	lis     r12, STACK_END_MAGIC@h
 	ori     r12, r12, STACK_END_MAGIC@l
 	std	r12, -8(r11)
 
-	/* Put ctr in r12 for global entry and branch there */
+	/* Save toc & real LR on livepatch stack */
+	std	r2,  -24(r11)
+#ifndef CONFIG_PPC_FTRACE_OUT_OF_LINE
+	mflr	r12
+	std	r12, -16(r11)
 	mfctr	r12
+#else
+	std	r0, -16(r11)
+	mflr	r12
+	/* Put ctr in r12 for global entry and branch there */
+	mtctr	r12
+#endif
 	bctrl
 
 	/*
diff --git a/arch/powerpc/tools/Makefile b/arch/powerpc/tools/Makefile
new file mode 100644
index 000000000000..31dd3151c272
--- /dev/null
+++ b/arch/powerpc/tools/Makefile
@@ -0,0 +1,10 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+quiet_cmd_gen_ftrace_ool_stubs = FTRACE  $@
+      cmd_gen_ftrace_ool_stubs = $< $(objtree)/vmlinux.o $@
+
+targets += .arch.vmlinux.o
+.arch.vmlinux.o: $(srctree)/arch/powerpc/tools/ftrace-gen-ool-stubs.sh $(objtree)/vmlinux.o FORCE
+	$(call if_changed,gen_ftrace_ool_stubs)
+
+clean-files += $(objtree)/.arch.vmlinux.S $(objtree)/.arch.vmlinux.o
diff --git a/arch/powerpc/tools/ftrace-gen-ool-stubs.sh b/arch/powerpc/tools/ftrace-gen-ool-stubs.sh
new file mode 100755
index 000000000000..0b85cd5262ff
--- /dev/null
+++ b/arch/powerpc/tools/ftrace-gen-ool-stubs.sh
@@ -0,0 +1,48 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+# Error out on error
+set -e
+
+is_enabled() {
+	grep -q "^$1=y" include/config/auto.conf
+}
+
+vmlinux_o=${1}
+arch_vmlinux_o=${2}
+arch_vmlinux_S=$(dirname ${arch_vmlinux_o})/$(basename ${arch_vmlinux_o} .o).S
+
+RELOCATION=R_PPC64_ADDR64
+if is_enabled CONFIG_PPC32; then
+	RELOCATION=R_PPC_ADDR32
+fi
+
+num_ool_stubs_text=$(${CROSS_COMPILE}objdump -r -j __patchable_function_entries ${vmlinux_o} |
+		     grep -v ".init.text" | grep "${RELOCATION}" | wc -l)
+num_ool_stubs_inittext=$(${CROSS_COMPILE}objdump -r -j __patchable_function_entries ${vmlinux_o} |
+			 grep ".init.text" | grep "${RELOCATION}" | wc -l)
+
+cat > ${arch_vmlinux_S} <<EOF
+#include <asm/asm-offsets.h>
+#include <linux/linkage.h>
+
+.pushsection .tramp.ftrace.text,"aw"
+SYM_DATA(ftrace_ool_stub_text_end_count, .long ${num_ool_stubs_text})
+
+SYM_CODE_START(ftrace_ool_stub_text_end)
+	.space ${num_ool_stubs_text} * FTRACE_OOL_STUB_SIZE
+SYM_CODE_END(ftrace_ool_stub_text_end)
+.popsection
+
+.pushsection .tramp.ftrace.init,"aw"
+SYM_DATA(ftrace_ool_stub_inittext_count, .long ${num_ool_stubs_inittext})
+
+SYM_CODE_START(ftrace_ool_stub_inittext)
+	.space ${num_ool_stubs_inittext} * FTRACE_OOL_STUB_SIZE
+SYM_CODE_END(ftrace_ool_stub_inittext)
+.popsection
+EOF
+
+${CC} ${NOSTDINC_FLAGS} ${LINUXINCLUDE} ${KBUILD_CPPFLAGS} \
+      ${KBUILD_AFLAGS} ${KBUILD_AFLAGS_KERNEL} \
+      -c -o ${arch_vmlinux_o} ${arch_vmlinux_S}
-- 
2.45.2

Re: [RFC PATCH v4 12/17] powerpc64/ftrace: Move ftrace sequence out of line

[Nicholas Piggin]

On Sun Jul 14, 2024 at 6:27 PM AEST, Naveen N Rao wrote:
> Function profile sequence on powerpc includes two instructions at the
> beginning of each function:
> 	mflr	r0
> 	bl	ftrace_caller
>
> The call to ftrace_caller() gets nop'ed out during kernel boot and is
> patched in when ftrace is enabled.
>
> Given the sequence, we cannot return from ftrace_caller with 'blr' as we
> need to keep LR and r0 intact. This results in link stack (return
> address predictor) imbalance when ftrace is enabled. To address that, we
> would like to use a three instruction sequence:
> 	mflr	r0
> 	bl	ftrace_caller
> 	mtlr	r0
>
> Further more, to support DYNAMIC_FTRACE_WITH_CALL_OPS, we need to
> reserve two instruction slots before the function. This results in a
> total of five instruction slots to be reserved for ftrace use on each
> function that is traced.
>
> Move the function profile sequence out-of-line to minimize its impact.
> To do this, we reserve a single nop at function entry using
> -fpatchable-function-entry=1 and add a pass on vmlinux.o to determine
> the total number of functions that can be traced. This is then used to
> generate a .S file reserving the appropriate amount of space for use as
> ftrace stubs, which is built and linked into vmlinux.

These are all going into .tramp.ftrace.text AFAIKS? Should that be
moved after some of the other text in the linker script then if it
could get quite large? sched and lock and other things should be
closer to the rest of text and hot code.

Thanks,
Nick

RE: [RFC PATCH v4 12/17] powerpc64/ftrace: Move ftrace sequence out of line

[David Laight]

From: Nicholas Piggin
> Sent: 15 July 2024 09:25
> 
> On Sun Jul 14, 2024 at 6:27 PM AEST, Naveen N Rao wrote:
> > Function profile sequence on powerpc includes two instructions at the
> > beginning of each function:
> > 	mflr	r0
> > 	bl	ftrace_caller
> >
> > The call to ftrace_caller() gets nop'ed out during kernel boot and is
> > patched in when ftrace is enabled.
> >
> > Given the sequence, we cannot return from ftrace_caller with 'blr' as we
> > need to keep LR and r0 intact. This results in link stack (return
> > address predictor) imbalance when ftrace is enabled. To address that, we
> > would like to use a three instruction sequence:
> > 	mflr	r0
> > 	bl	ftrace_caller
> > 	mtlr	r0
> >
> > Further more, to support DYNAMIC_FTRACE_WITH_CALL_OPS, we need to
> > reserve two instruction slots before the function. This results in a
> > total of five instruction slots to be reserved for ftrace use on each
> > function that is traced.
> >
> > Move the function profile sequence out-of-line to minimize its impact.
> > To do this, we reserve a single nop at function entry using
> > -fpatchable-function-entry=1 and add a pass on vmlinux.o to determine
> > the total number of functions that can be traced. This is then used to
> > generate a .S file reserving the appropriate amount of space for use as
> > ftrace stubs, which is built and linked into vmlinux.
> 
> These are all going into .tramp.ftrace.text AFAIKS? Should that be
> moved after some of the other text in the linker script then if it
> could get quite large? sched and lock and other things should be
> closer to the rest of text and hot code.

Can't you allocate the space for the 'function profile sequence'
at run-time when (if) ftrace is enabled?
When ftrace gets disabled it is likely possible to save the trampoline
number in the nop - so the same memory can be used next time.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

Re: [RFC PATCH v4 12/17] powerpc64/ftrace: Move ftrace sequence out of line

[Masahiro Yamada]

On Sun, Jul 14, 2024 at 5:29 PM Naveen N Rao <naveen@kernel.org> wrote:
>
> Function profile sequence on powerpc includes two instructions at the
> beginning of each function:
>         mflr    r0
>         bl      ftrace_caller
>
> The call to ftrace_caller() gets nop'ed out during kernel boot and is
> patched in when ftrace is enabled.
>
> Given the sequence, we cannot return from ftrace_caller with 'blr' as we
> need to keep LR and r0 intact. This results in link stack (return
> address predictor) imbalance when ftrace is enabled. To address that, we
> would like to use a three instruction sequence:
>         mflr    r0
>         bl      ftrace_caller
>         mtlr    r0
>
> Further more, to support DYNAMIC_FTRACE_WITH_CALL_OPS, we need to
> reserve two instruction slots before the function. This results in a
> total of five instruction slots to be reserved for ftrace use on each
> function that is traced.
>
> Move the function profile sequence out-of-line to minimize its impact.
> To do this, we reserve a single nop at function entry using
> -fpatchable-function-entry=1 and add a pass on vmlinux.o to determine
> the total number of functions that can be traced. This is then used to
> generate a .S file reserving the appropriate amount of space for use as
> ftrace stubs, which is built and linked into vmlinux.
>
> On bootup, the stub space is split into separate stubs per function and
> populated with the proper instruction sequence. A pointer to the
> associated stub is maintained in dyn_arch_ftrace.
>
> For modules, space for ftrace stubs is reserved from the generic module
> stub space.
>
> This is restricted to and enabled by default only on 64-bit powerpc,
> though there are some changes to accommodate 32-bit powerpc. This is
> done so that 32-bit powerpc could choose to opt into this based on
> further tests and benchmarks.
>
> As an example, after this patch, kernel functions will have a single nop
> at function entry:
> <kernel_clone>:
>         addis   r2,r12,467
>         addi    r2,r2,-16028
>         nop
>         mfocrf  r11,8
>         ...
>
> When ftrace is enabled, the nop is converted to an unconditional branch
> to the stub associated with that function:
> <kernel_clone>:
>         addis   r2,r12,467
>         addi    r2,r2,-16028
>         b       ftrace_ool_stub_text_end+0x11b28
>         mfocrf  r11,8
>         ...
>
> The associated stub:
> <ftrace_ool_stub_text_end+0x11b28>:
>         mflr    r0
>         bl      ftrace_caller
>         mtlr    r0
>         b       kernel_clone+0xc
>         ...
>
> Signed-off-by: Naveen N Rao <naveen@kernel.org>



> diff --git a/arch/powerpc/tools/Makefile b/arch/powerpc/tools/Makefile
> new file mode 100644
> index 000000000000..31dd3151c272
> --- /dev/null
> +++ b/arch/powerpc/tools/Makefile
> @@ -0,0 +1,10 @@
> +# SPDX-License-Identifier: GPL-2.0-or-later
> +
> +quiet_cmd_gen_ftrace_ool_stubs = FTRACE  $@


This is not "FTRACE".

"GEN" or something like that.



> +      cmd_gen_ftrace_ool_stubs = $< $(objtree)/vmlinux.o $@
> +
> +targets += .arch.vmlinux.o
> +.arch.vmlinux.o: $(srctree)/arch/powerpc/tools/ftrace-gen-ool-stubs.sh $(objtree)/vmlinux.o FORCE
> +       $(call if_changed,gen_ftrace_ool_stubs)
> +
> +clean-files += $(objtree)/.arch.vmlinux.S $(objtree)/.arch.vmlinux.o



This is wrong. $(objtree) is always '.'

It will attempt to clean up:

arch/powerpc/tools/.arch.vmlinux.S
arch/powerpc/tools/.arch.vmlinux.o



You must not create the intermediate file,
.arch.vmlinux.S at the top directory because
this build step is pretty much PowerPC-specific.


Rather, I'd recommend to create *.S and *.o in
arch/powerpc/tools/:

arch/powerpc/tools/vmlinux.S
arch/powerpc/tools/vmlinux.o




When you submit the next version, please run 'make clean'
and confirm that any powerpc-specific build artifacts
not being left-over.






> diff --git a/arch/powerpc/tools/ftrace-gen-ool-stubs.sh b/arch/powerpc/tools/ftrace-gen-ool-stubs.sh
> new file mode 100755
> index 000000000000..0b85cd5262ff
> --- /dev/null
> +++ b/arch/powerpc/tools/ftrace-gen-ool-stubs.sh
> @@ -0,0 +1,48 @@
> +#!/bin/sh
> +# SPDX-License-Identifier: GPL-2.0-or-later
> +
> +# Error out on error
> +set -e
> +
> +is_enabled() {
> +       grep -q "^$1=y" include/config/auto.conf
> +}
> +
> +vmlinux_o=${1}
> +arch_vmlinux_o=${2}
> +arch_vmlinux_S=$(dirname ${arch_vmlinux_o})/$(basename ${arch_vmlinux_o} .o).S
> +
> +RELOCATION=R_PPC64_ADDR64
> +if is_enabled CONFIG_PPC32; then
> +       RELOCATION=R_PPC_ADDR32
> +fi
> +
> +num_ool_stubs_text=$(${CROSS_COMPILE}objdump -r -j __patchable_function_entries ${vmlinux_o} |
> +                    grep -v ".init.text" | grep "${RELOCATION}" | wc -l)
> +num_ool_stubs_inittext=$(${CROSS_COMPILE}objdump -r -j __patchable_function_entries ${vmlinux_o} |
> +                        grep ".init.text" | grep "${RELOCATION}" | wc -l)
> +
> +cat > ${arch_vmlinux_S} <<EOF
> +#include <asm/asm-offsets.h>
> +#include <linux/linkage.h>
> +
> +.pushsection .tramp.ftrace.text,"aw"
> +SYM_DATA(ftrace_ool_stub_text_end_count, .long ${num_ool_stubs_text})
> +
> +SYM_CODE_START(ftrace_ool_stub_text_end)
> +       .space ${num_ool_stubs_text} * FTRACE_OOL_STUB_SIZE
> +SYM_CODE_END(ftrace_ool_stub_text_end)
> +.popsection
> +
> +.pushsection .tramp.ftrace.init,"aw"
> +SYM_DATA(ftrace_ool_stub_inittext_count, .long ${num_ool_stubs_inittext})
> +
> +SYM_CODE_START(ftrace_ool_stub_inittext)
> +       .space ${num_ool_stubs_inittext} * FTRACE_OOL_STUB_SIZE
> +SYM_CODE_END(ftrace_ool_stub_inittext)
> +.popsection
> +EOF
> +
> +${CC} ${NOSTDINC_FLAGS} ${LINUXINCLUDE} ${KBUILD_CPPFLAGS} \
> +      ${KBUILD_AFLAGS} ${KBUILD_AFLAGS_KERNEL} \
> +      -c -o ${arch_vmlinux_o} ${arch_vmlinux_S}


Please do not compile this within a shell script.

scripts/Makefile.build provides rule_as_o_S to do this.




[1] vmlinux.o --> arch/powerpc/tools/vmlinux.S

[2] arch/powerpc/tools/vmlinux.S --> arch/powerpc/tools/vmlinux.o


Please split these in separate build rules.





> --
> 2.45.2
>


--
Best Regards
Masahiro Yamada

[RFC PATCH v4 13/17] powerpc64/ftrace: Support .text larger than 32MB with out-of-line stubs

[Naveen N Rao]

We are restricted to a .text size of ~32MB when using out-of-line
function profile sequence. Allow this to be extended up to the previous
limit of ~64MB by reserving space in the middle of .text.

A new config option CONFIG_PPC_FTRACE_OUT_OF_LINE_NUM_RESERVE is
introduced to specify the number of function stubs that are reserved in
.text. On boot, ftrace utilizes stubs from this area first before using
the stub area at the end of .text.

A ppc64le defconfig has ~44k functions that can be traced. A more
conservative value of 32k functions is chosen as the default value of
PPC_FTRACE_OUT_OF_LINE_NUM_RESERVE so that we do not allot more space
than necessary by default. If building a kernel that only has 32k
trace-able functions, we won't allot any more space at the end of .text
during the pass on vmlinux.o. Otherwise, only the remaining functions
get space for stubs at the end of .text. This default value should help
cover a .text size of ~48MB in total (including space reserved at the
end of .text which can cover up to 32MB), which should be sufficient for
most common builds. For a very small kernel build, this can be set to 0.
Or, this can be bumped up to a larger value to support vmlinux .text
size up to ~64MB.

Signed-off-by: Naveen N Rao <naveen@kernel.org>
---
 arch/powerpc/Kconfig                       | 12 ++++++++++++
 arch/powerpc/include/asm/ftrace.h          |  6 ++++--
 arch/powerpc/kernel/trace/ftrace.c         | 21 +++++++++++++++++----
 arch/powerpc/kernel/trace/ftrace_entry.S   |  8 ++++++++
 arch/powerpc/tools/Makefile                |  2 +-
 arch/powerpc/tools/ftrace-gen-ool-stubs.sh | 11 +++++++----
 6 files changed, 49 insertions(+), 11 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index f50cfd15bb73..a4dff8624510 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -573,6 +573,18 @@ config PPC_FTRACE_OUT_OF_LINE
 	depends on PPC64
 	select ARCH_WANTS_PRE_LINK_VMLINUX
 
+config PPC_FTRACE_OUT_OF_LINE_NUM_RESERVE
+	int "Number of ftrace out-of-line stubs to reserve within .text"
+	default 32768 if PPC_FTRACE_OUT_OF_LINE
+	default 0
+	help
+	  Number of stubs to reserve for use by ftrace. This space is
+	  reserved within .text, and is distinct from any additional space
+	  added at the end of .text before the final vmlinux link. Set to
+	  zero to have stubs only be generated at the end of vmlinux (only
+	  if the size of vmlinux is less than 32MB). Set to a higher value
+	  if building vmlinux larger than 48MB.
+
 config HOTPLUG_CPU
 	bool "Support for enabling/disabling CPUs"
 	depends on SMP && (PPC_PSERIES || \
diff --git a/arch/powerpc/include/asm/ftrace.h b/arch/powerpc/include/asm/ftrace.h
index 0589bb252de7..dc870824359c 100644
--- a/arch/powerpc/include/asm/ftrace.h
+++ b/arch/powerpc/include/asm/ftrace.h
@@ -140,8 +140,10 @@ extern unsigned int ftrace_tramp_text[], ftrace_tramp_init[];
 struct ftrace_ool_stub {
 	u32	insn[4];
 };
-extern struct ftrace_ool_stub ftrace_ool_stub_text_end[], ftrace_ool_stub_inittext[];
-extern unsigned int ftrace_ool_stub_text_end_count, ftrace_ool_stub_inittext_count;
+extern struct ftrace_ool_stub ftrace_ool_stub_text_end[], ftrace_ool_stub_text[],
+			      ftrace_ool_stub_inittext[];
+extern unsigned int ftrace_ool_stub_text_end_count, ftrace_ool_stub_text_count,
+		    ftrace_ool_stub_inittext_count;
 #endif
 void ftrace_free_init_tramp(void);
 unsigned long ftrace_call_adjust(unsigned long addr);
diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
index c03336301bad..b4de8b8cbe3a 100644
--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/arch/powerpc/kernel/trace/ftrace.c
@@ -168,7 +168,7 @@ static int ftrace_get_call_inst(struct dyn_ftrace *rec, unsigned long addr, ppc_
 static int ftrace_init_ool_stub(struct module *mod, struct dyn_ftrace *rec)
 {
 #ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
-	static int ool_stub_text_end_index, ool_stub_inittext_index;
+	static int ool_stub_text_index, ool_stub_text_end_index, ool_stub_inittext_index;
 	int ret = 0, ool_stub_count, *ool_stub_index;
 	ppc_inst_t inst;
 	/*
@@ -191,9 +191,22 @@ static int ftrace_init_ool_stub(struct module *mod, struct dyn_ftrace *rec)
 		ool_stub_index = &ool_stub_inittext_index;
 		ool_stub_count = ftrace_ool_stub_inittext_count;
 	} else if (is_kernel_text(rec->ip)) {
-		ool_stub = ftrace_ool_stub_text_end;
-		ool_stub_index = &ool_stub_text_end_index;
-		ool_stub_count = ftrace_ool_stub_text_end_count;
+		/*
+		 * ftrace records are sorted, so we first use up the stub area within .text
+		 * (ftrace_ool_stub_text) before using the area at the end of .text
+		 * (ftrace_ool_stub_text_end), unless the stub is out of range of the record.
+		 */
+		if (ool_stub_text_index >= ftrace_ool_stub_text_count ||
+		    !is_offset_in_branch_range((long)rec->ip -
+					       (long)&ftrace_ool_stub_text[ool_stub_text_index])) {
+			ool_stub = ftrace_ool_stub_text_end;
+			ool_stub_index = &ool_stub_text_end_index;
+			ool_stub_count = ftrace_ool_stub_text_end_count;
+		} else {
+			ool_stub = ftrace_ool_stub_text;
+			ool_stub_index = &ool_stub_text_index;
+			ool_stub_count = ftrace_ool_stub_text_count;
+		}
 #ifdef CONFIG_MODULES
 	} else if (mod) {
 		ool_stub = mod->arch.ool_stubs;
diff --git a/arch/powerpc/kernel/trace/ftrace_entry.S b/arch/powerpc/kernel/trace/ftrace_entry.S
index 71f6a63cd861..86dbaa87532a 100644
--- a/arch/powerpc/kernel/trace/ftrace_entry.S
+++ b/arch/powerpc/kernel/trace/ftrace_entry.S
@@ -374,6 +374,14 @@ _GLOBAL(return_to_handler)
 	blr
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
 
+#ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
+SYM_DATA(ftrace_ool_stub_text_count, .long CONFIG_PPC_FTRACE_OUT_OF_LINE_NUM_RESERVE)
+
+SYM_CODE_START(ftrace_ool_stub_text)
+	.space CONFIG_PPC_FTRACE_OUT_OF_LINE_NUM_RESERVE * FTRACE_OOL_STUB_SIZE
+SYM_CODE_END(ftrace_ool_stub_text)
+#endif
+
 .pushsection ".tramp.ftrace.text","aw",@progbits;
 .globl ftrace_tramp_text
 ftrace_tramp_text:
diff --git a/arch/powerpc/tools/Makefile b/arch/powerpc/tools/Makefile
index 31dd3151c272..0ade63981aea 100644
--- a/arch/powerpc/tools/Makefile
+++ b/arch/powerpc/tools/Makefile
@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0-or-later
 
 quiet_cmd_gen_ftrace_ool_stubs = FTRACE  $@
-      cmd_gen_ftrace_ool_stubs = $< $(objtree)/vmlinux.o $@
+      cmd_gen_ftrace_ool_stubs = $< $(CONFIG_PPC_FTRACE_OUT_OF_LINE_NUM_RESERVE) $(objtree)/vmlinux.o $@
 
 targets += .arch.vmlinux.o
 .arch.vmlinux.o: $(srctree)/arch/powerpc/tools/ftrace-gen-ool-stubs.sh $(objtree)/vmlinux.o FORCE
diff --git a/arch/powerpc/tools/ftrace-gen-ool-stubs.sh b/arch/powerpc/tools/ftrace-gen-ool-stubs.sh
index 0b85cd5262ff..0d83adce4f23 100755
--- a/arch/powerpc/tools/ftrace-gen-ool-stubs.sh
+++ b/arch/powerpc/tools/ftrace-gen-ool-stubs.sh
@@ -8,8 +8,8 @@ is_enabled() {
 	grep -q "^$1=y" include/config/auto.conf
 }
 
-vmlinux_o=${1}
-arch_vmlinux_o=${2}
+vmlinux_o=${2}
+arch_vmlinux_o=${3}
 arch_vmlinux_S=$(dirname ${arch_vmlinux_o})/$(basename ${arch_vmlinux_o} .o).S
 
 RELOCATION=R_PPC64_ADDR64
@@ -22,15 +22,18 @@ num_ool_stubs_text=$(${CROSS_COMPILE}objdump -r -j __patchable_function_entries
 num_ool_stubs_inittext=$(${CROSS_COMPILE}objdump -r -j __patchable_function_entries ${vmlinux_o} |
 			 grep ".init.text" | grep "${RELOCATION}" | wc -l)
 
+num_ool_stubs_text_builtin=${1}
+num_ool_stubs_text_end=$(expr ${num_ool_stubs_text} - ${num_ool_stubs_text_builtin})
+
 cat > ${arch_vmlinux_S} <<EOF
 #include <asm/asm-offsets.h>
 #include <linux/linkage.h>
 
 .pushsection .tramp.ftrace.text,"aw"
-SYM_DATA(ftrace_ool_stub_text_end_count, .long ${num_ool_stubs_text})
+SYM_DATA(ftrace_ool_stub_text_end_count, .long ${num_ool_stubs_text_end})
 
 SYM_CODE_START(ftrace_ool_stub_text_end)
-	.space ${num_ool_stubs_text} * FTRACE_OOL_STUB_SIZE
+	.space ${num_ool_stubs_text_end} * FTRACE_OOL_STUB_SIZE
 SYM_CODE_END(ftrace_ool_stub_text_end)
 .popsection
 
-- 
2.45.2

Re: [RFC PATCH v4 13/17] powerpc64/ftrace: Support .text larger than 32MB with out-of-line stubs

[Nicholas Piggin]

On Sun Jul 14, 2024 at 6:27 PM AEST, Naveen N Rao wrote:
> We are restricted to a .text size of ~32MB when using out-of-line
> function profile sequence. Allow this to be extended up to the previous
> limit of ~64MB by reserving space in the middle of .text.
>
> A new config option CONFIG_PPC_FTRACE_OUT_OF_LINE_NUM_RESERVE is
> introduced to specify the number of function stubs that are reserved in
> .text. On boot, ftrace utilizes stubs from this area first before using
> the stub area at the end of .text.

[snip]

> diff --git a/arch/powerpc/kernel/trace/ftrace_entry.S b/arch/powerpc/kernel/trace/ftrace_entry.S
> index 71f6a63cd861..86dbaa87532a 100644
> --- a/arch/powerpc/kernel/trace/ftrace_entry.S
> +++ b/arch/powerpc/kernel/trace/ftrace_entry.S
> @@ -374,6 +374,14 @@ _GLOBAL(return_to_handler)
>  	blr
>  #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
>  
> +#ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
> +SYM_DATA(ftrace_ool_stub_text_count, .long CONFIG_PPC_FTRACE_OUT_OF_LINE_NUM_RESERVE)
> +
> +SYM_CODE_START(ftrace_ool_stub_text)
> +	.space CONFIG_PPC_FTRACE_OUT_OF_LINE_NUM_RESERVE * FTRACE_OOL_STUB_SIZE
> +SYM_CODE_END(ftrace_ool_stub_text)
> +#endif
> +
>  .pushsection ".tramp.ftrace.text","aw",@progbits;
>  .globl ftrace_tramp_text
>  ftrace_tramp_text:

How are you ensuring these new stubs get to the middle of kernel text? I
guess you just put it in regular .text and hope the linker puts it
in a good place?

Thanks,
Nick

[RFC PATCH v4 14/17] powerpc/ftrace: Add support for DYNAMIC_FTRACE_WITH_CALL_OPS

[Naveen N Rao]

Implement support for DYNAMIC_FTRACE_WITH_CALL_OPS similar to the
arm64 implementation.

This works by patching-in a pointer to an associated ftrace_ops
structure before each traceable function. If multiple ftrace_ops are
associated with a call site, then a special ftrace_list_ops is used to
enable iterating over all the registered ftrace_ops. If no ftrace_ops
are associated with a call site, then a special ftrace_nop_ops structure
is used to render the ftrace call as a no-op. ftrace trampoline can then
read the associated ftrace_ops for a call site by loading from an offset
from the LR, and branch directly to the associated function.

The primary advantage with this approach is that we don't have to
iterate over all the registered ftrace_ops for call sites that have a
single ftrace_ops registered. This is the equivalent of implementing
support for dynamic ftrace trampolines, which set up a special ftrace
trampoline for each registered ftrace_ops and have individual call sites
branch into those directly.

A secondary advantage is that this gives us a way to add support for
direct ftrace callers without having to resort to using stubs. The
address of the direct call trampoline can be loaded from the ftrace_ops
structure.

To support this, we reserve a nop before each function on 32-bit
powerpc. For 64-bit powerpc, two nops are reserved before each
out-of-line stub. During ftrace activation, we update this location with
the associated ftrace_ops pointer. Then, on ftrace entry, we load from
this location and call into ftrace_ops->func().

For 64-bit powerpc, we ensure that the out-of-line stub area is
doubleword aligned so that ftrace_ops address can be updated atomically.

Signed-off-by: Naveen N Rao <naveen@kernel.org>
---
 arch/powerpc/Kconfig                       |  1 +
 arch/powerpc/Makefile                      |  4 ++
 arch/powerpc/include/asm/ftrace.h          |  5 +-
 arch/powerpc/kernel/asm-offsets.c          |  4 ++
 arch/powerpc/kernel/trace/ftrace.c         | 59 +++++++++++++++++++++-
 arch/powerpc/kernel/trace/ftrace_entry.S   | 36 ++++++++++---
 arch/powerpc/tools/ftrace-gen-ool-stubs.sh |  5 +-
 7 files changed, 102 insertions(+), 12 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index a4dff8624510..cb6031d86dc9 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -235,6 +235,7 @@ config PPC
 	select HAVE_DEBUG_STACKOVERFLOW
 	select HAVE_DYNAMIC_FTRACE
 	select HAVE_DYNAMIC_FTRACE_WITH_ARGS	if ARCH_USING_PATCHABLE_FUNCTION_ENTRY || MPROFILE_KERNEL || PPC32
+	select HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS if PPC_FTRACE_OUT_OF_LINE || (PPC32 && ARCH_USING_PATCHABLE_FUNCTION_ENTRY)
 	select HAVE_DYNAMIC_FTRACE_WITH_REGS	if ARCH_USING_PATCHABLE_FUNCTION_ENTRY || MPROFILE_KERNEL || PPC32
 	select HAVE_EBPF_JIT
 	select HAVE_EFFICIENT_UNALIGNED_ACCESS
diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index c973e6cd1ae8..7dede0ec0163 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -158,8 +158,12 @@ KBUILD_CPPFLAGS	+= -DCC_USING_PATCHABLE_FUNCTION_ENTRY
 ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
 CC_FLAGS_FTRACE := -fpatchable-function-entry=1
 else
+ifdef CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS # PPC32 only
+CC_FLAGS_FTRACE := -fpatchable-function-entry=3,1
+else
 CC_FLAGS_FTRACE := -fpatchable-function-entry=2
 endif
+endif
 else
 CC_FLAGS_FTRACE := -pg
 ifdef CONFIG_MPROFILE_KERNEL
diff --git a/arch/powerpc/include/asm/ftrace.h b/arch/powerpc/include/asm/ftrace.h
index dc870824359c..267bd52fef21 100644
--- a/arch/powerpc/include/asm/ftrace.h
+++ b/arch/powerpc/include/asm/ftrace.h
@@ -138,8 +138,11 @@ static inline u8 this_cpu_get_ftrace_enabled(void) { return 1; }
 extern unsigned int ftrace_tramp_text[], ftrace_tramp_init[];
 #ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
 struct ftrace_ool_stub {
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS
+	struct ftrace_ops *ftrace_op;
+#endif
 	u32	insn[4];
-};
+} __aligned(sizeof(unsigned long));
 extern struct ftrace_ool_stub ftrace_ool_stub_text_end[], ftrace_ool_stub_text[],
 			      ftrace_ool_stub_inittext[];
 extern unsigned int ftrace_ool_stub_text_end_count, ftrace_ool_stub_text_count,
diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index 6854547d3164..60d1e388c2ba 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -678,5 +678,9 @@ int main(void)
 	DEFINE(FTRACE_OOL_STUB_SIZE, sizeof(struct ftrace_ool_stub));
 #endif
 
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS
+	OFFSET(FTRACE_OPS_FUNC, ftrace_ops, func);
+#endif
+
 	return 0;
 }
diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
index b4de8b8cbe3a..291c6c3d3a78 100644
--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/arch/powerpc/kernel/trace/ftrace.c
@@ -38,8 +38,11 @@ unsigned long ftrace_call_adjust(unsigned long addr)
 		return 0;
 
 	if (IS_ENABLED(CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY) &&
-	    !IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE))
+	    !IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE)) {
 		addr += MCOUNT_INSN_SIZE;
+		if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS))
+			addr += MCOUNT_INSN_SIZE;
+	}
 
 	return addr;
 }
@@ -259,6 +262,46 @@ static int ftrace_init_ool_stub(struct module *mod, struct dyn_ftrace *rec)
 #endif
 }
 
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS
+static const struct ftrace_ops *powerpc_rec_get_ops(struct dyn_ftrace *rec)
+{
+	const struct ftrace_ops *ops = NULL;
+
+	if (rec->flags & FTRACE_FL_CALL_OPS_EN) {
+		ops = ftrace_find_unique_ops(rec);
+		WARN_ON_ONCE(!ops);
+	}
+
+	if (!ops)
+		ops = &ftrace_list_ops;
+
+	return ops;
+}
+
+static int ftrace_rec_set_ops(struct dyn_ftrace *rec, const struct ftrace_ops *ops)
+{
+	if (IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE))
+		return patch_ulong((void *)(ftrace_get_ool_stub(rec) - sizeof(unsigned long)),
+				   (unsigned long)ops);
+	else
+		return patch_ulong((void *)(rec->ip - MCOUNT_INSN_SIZE - sizeof(unsigned long)),
+				   (unsigned long)ops);
+}
+
+static int ftrace_rec_set_nop_ops(struct dyn_ftrace *rec)
+{
+	return ftrace_rec_set_ops(rec, &ftrace_nop_ops);
+}
+
+static int ftrace_rec_update_ops(struct dyn_ftrace *rec)
+{
+	return ftrace_rec_set_ops(rec, powerpc_rec_get_ops(rec));
+}
+#else
+static int ftrace_rec_set_nop_ops(struct dyn_ftrace *rec) { return 0; }
+static int ftrace_rec_update_ops(struct dyn_ftrace *rec) { return 0; }
+#endif
+
 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
 int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, unsigned long addr)
 {
@@ -289,6 +332,10 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 	if (!ret)
 		ret = ftrace_modify_code(ip, old, new);
 
+	ret = ftrace_rec_update_ops(rec);
+	if (ret)
+		return ret;
+
 	if (!ret && IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE))
 		ret = ftrace_modify_code(rec->ip, ppc_inst(PPC_RAW_NOP()),
 			 ppc_inst(PPC_RAW_BRANCH((long)ftrace_get_ool_stub(rec) - (long)rec->ip)));
@@ -340,16 +387,19 @@ void ftrace_replace_code(int enable)
 		case FTRACE_UPDATE_MODIFY_CALL:
 			ret = ftrace_get_call_inst(rec, new_addr, &new_call_inst);
 			ret |= ftrace_get_call_inst(rec, addr, &call_inst);
+			ret |= ftrace_rec_update_ops(rec);
 			old = call_inst;
 			new = new_call_inst;
 			break;
 		case FTRACE_UPDATE_MAKE_NOP:
 			ret = ftrace_get_call_inst(rec, addr, &call_inst);
+			ret |= ftrace_rec_set_nop_ops(rec);
 			old = call_inst;
 			new = nop_inst;
 			break;
 		case FTRACE_UPDATE_MAKE_CALL:
 			ret = ftrace_get_call_inst(rec, new_addr, &call_inst);
+			ret |= ftrace_rec_update_ops(rec);
 			old = nop_inst;
 			new = call_inst;
 			break;
@@ -465,6 +515,13 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
 	ppc_inst_t old, new;
 	int ret;
 
+	/*
+	 * When using CALL_OPS, the function to call is associated with the
+	 * call site, and we don't have a global function pointer to update.
+	 */
+	if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS))
+		return 0;
+
 	old = ppc_inst_read((u32 *)&ftrace_call);
 	new = ftrace_create_branch_inst(ip, ppc_function_entry(func), 1);
 	ret = ftrace_modify_code(ip, old, new);
diff --git a/arch/powerpc/kernel/trace/ftrace_entry.S b/arch/powerpc/kernel/trace/ftrace_entry.S
index 86dbaa87532a..c019380bdd6a 100644
--- a/arch/powerpc/kernel/trace/ftrace_entry.S
+++ b/arch/powerpc/kernel/trace/ftrace_entry.S
@@ -85,11 +85,21 @@
 	/* Save callee's TOC in the ABI compliant location */
 	std	r2, STK_GOT(r1)
 	LOAD_PACA_TOC()		/* get kernel TOC in r2 */
+#endif
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS
+	/* r7 points to the instruction following the call to ftrace */
+	PPC_LL	r5, -(MCOUNT_INSN_SIZE*2 + SZL)(r7)
+	PPC_LL	r12, FTRACE_OPS_FUNC(r5)
+	mtctr	r12
+#else /* !CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS */
+#ifdef CONFIG_PPC64
 	LOAD_REG_ADDR(r3, function_trace_op)
 	ld	r5,0(r3)
 #else
 	lis	r3,function_trace_op@ha
 	lwz	r5,function_trace_op@l(r3)
+#endif
 #endif
 
 	/* Save special regs */
@@ -205,20 +215,30 @@
 #endif
 .endm
 
-_GLOBAL(ftrace_regs_caller)
-	ftrace_regs_entry 1
-	/* ftrace_call(r3, r4, r5, r6) */
+.macro ftrace_regs_func allregs
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS
+	bctrl
+#else
+	.if \allregs == 1
 .globl ftrace_regs_call
 ftrace_regs_call:
+	.else
+.globl ftrace_call
+ftrace_call:
+	.endif
+	/* ftrace_call(r3, r4, r5, r6) */
 	bl	ftrace_stub
+#endif
+.endm
+
+_GLOBAL(ftrace_regs_caller)
+	ftrace_regs_entry 1
+	ftrace_regs_func 1
 	ftrace_regs_exit 1
 
 _GLOBAL(ftrace_caller)
 	ftrace_regs_entry 0
-	/* ftrace_call(r3, r4, r5, r6) */
-.globl ftrace_call
-ftrace_call:
-	bl	ftrace_stub
+	ftrace_regs_func 0
 	ftrace_regs_exit 0
 
 _GLOBAL(ftrace_stub)
@@ -377,7 +397,7 @@ _GLOBAL(return_to_handler)
 #ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
 SYM_DATA(ftrace_ool_stub_text_count, .long CONFIG_PPC_FTRACE_OUT_OF_LINE_NUM_RESERVE)
 
-SYM_CODE_START(ftrace_ool_stub_text)
+SYM_START(ftrace_ool_stub_text, SYM_L_GLOBAL, .balign SZL)
 	.space CONFIG_PPC_FTRACE_OUT_OF_LINE_NUM_RESERVE * FTRACE_OOL_STUB_SIZE
 SYM_CODE_END(ftrace_ool_stub_text)
 #endif
diff --git a/arch/powerpc/tools/ftrace-gen-ool-stubs.sh b/arch/powerpc/tools/ftrace-gen-ool-stubs.sh
index 0d83adce4f23..a8dc26e10e66 100755
--- a/arch/powerpc/tools/ftrace-gen-ool-stubs.sh
+++ b/arch/powerpc/tools/ftrace-gen-ool-stubs.sh
@@ -27,12 +27,13 @@ num_ool_stubs_text_end=$(expr ${num_ool_stubs_text} - ${num_ool_stubs_text_built
 
 cat > ${arch_vmlinux_S} <<EOF
 #include <asm/asm-offsets.h>
+#include <asm/ppc_asm.h>
 #include <linux/linkage.h>
 
 .pushsection .tramp.ftrace.text,"aw"
 SYM_DATA(ftrace_ool_stub_text_end_count, .long ${num_ool_stubs_text_end})
 
-SYM_CODE_START(ftrace_ool_stub_text_end)
+SYM_START(ftrace_ool_stub_text_end, SYM_L_GLOBAL, .balign SZL)
 	.space ${num_ool_stubs_text_end} * FTRACE_OOL_STUB_SIZE
 SYM_CODE_END(ftrace_ool_stub_text_end)
 .popsection
@@ -40,7 +41,7 @@ SYM_CODE_END(ftrace_ool_stub_text_end)
 .pushsection .tramp.ftrace.init,"aw"
 SYM_DATA(ftrace_ool_stub_inittext_count, .long ${num_ool_stubs_inittext})
 
-SYM_CODE_START(ftrace_ool_stub_inittext)
+SYM_START(ftrace_ool_stub_inittext, SYM_L_GLOBAL, .balign SZL)
 	.space ${num_ool_stubs_inittext} * FTRACE_OOL_STUB_SIZE
 SYM_CODE_END(ftrace_ool_stub_inittext)
 .popsection
-- 
2.45.2

[RFC PATCH v4 15/17] powerpc/ftrace: Add support for DYNAMIC_FTRACE_WITH_DIRECT_CALLS

[Naveen N Rao]

Add support for DYNAMIC_FTRACE_WITH_DIRECT_CALLS similar to the arm64
implementation.

ftrace direct calls allow custom trampolines to be called into directly
from function ftrace call sites, bypassing the ftrace trampoline
completely. This functionality is currently utilized by BPF trampolines
to hook into kernel function entries.

Since we have limited relative branch range, we support ftrace direct
calls through support for DYNAMIC_FTRACE_WITH_CALL_OPS. In this
approach, ftrace trampoline is not entirely bypassed. Rather, it is
re-purposed into a stub that reads direct_call field from the associated
ftrace_ops structure and branches into that, if it is not NULL. For
this, it is sufficient if we can ensure that the ftrace trampoline is
reachable from all traceable functions.

When multiple ftrace_ops are associated with a call site, we utilize a
call back to set pt_regs->orig_gpr3 that can then be tested on the
return path from the ftrace trampoline to branch into the direct caller.

Signed-off-by: Naveen N Rao <naveen@kernel.org>
---
 arch/powerpc/Kconfig                     |   1 +
 arch/powerpc/include/asm/ftrace.h        |  15 +++
 arch/powerpc/kernel/asm-offsets.c        |   3 +
 arch/powerpc/kernel/trace/ftrace.c       |   9 ++
 arch/powerpc/kernel/trace/ftrace_entry.S | 114 +++++++++++++++++------
 5 files changed, 113 insertions(+), 29 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index cb6031d86dc9..29aab3770415 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -236,6 +236,7 @@ config PPC
 	select HAVE_DYNAMIC_FTRACE
 	select HAVE_DYNAMIC_FTRACE_WITH_ARGS	if ARCH_USING_PATCHABLE_FUNCTION_ENTRY || MPROFILE_KERNEL || PPC32
 	select HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS if PPC_FTRACE_OUT_OF_LINE || (PPC32 && ARCH_USING_PATCHABLE_FUNCTION_ENTRY)
+	select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS if HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS
 	select HAVE_DYNAMIC_FTRACE_WITH_REGS	if ARCH_USING_PATCHABLE_FUNCTION_ENTRY || MPROFILE_KERNEL || PPC32
 	select HAVE_EBPF_JIT
 	select HAVE_EFFICIENT_UNALIGNED_ACCESS
diff --git a/arch/powerpc/include/asm/ftrace.h b/arch/powerpc/include/asm/ftrace.h
index 267bd52fef21..2f1a6d25838d 100644
--- a/arch/powerpc/include/asm/ftrace.h
+++ b/arch/powerpc/include/asm/ftrace.h
@@ -150,6 +150,21 @@ extern unsigned int ftrace_ool_stub_text_end_count, ftrace_ool_stub_text_count,
 #endif
 void ftrace_free_init_tramp(void);
 unsigned long ftrace_call_adjust(unsigned long addr);
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
+/*
+ * When an ftrace registered caller is tracing a function that is also set by a
+ * register_ftrace_direct() call, it needs to be differentiated in the
+ * ftrace_caller trampoline so that the direct call can be invoked after the
+ * other ftrace ops. To do this, place the direct caller in the orig_gpr3 field
+ * of pt_regs. This tells ftrace_caller that there's a direct caller.
+ */
+static inline void arch_ftrace_set_direct_caller(struct ftrace_regs *fregs, unsigned long addr)
+{
+	struct pt_regs *regs = &fregs->regs;
+	regs->orig_gpr3 = addr;
+}
+#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
 #else
 static inline void ftrace_free_init_tramp(void) { }
 static inline unsigned long ftrace_call_adjust(unsigned long addr) { return addr; }
diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index 60d1e388c2ba..dbd56264a8bc 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -680,6 +680,9 @@ int main(void)
 
 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS
 	OFFSET(FTRACE_OPS_FUNC, ftrace_ops, func);
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
+	OFFSET(FTRACE_OPS_DIRECT_CALL, ftrace_ops, direct_call);
+#endif
 #endif
 
 	return 0;
diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
index 291c6c3d3a78..4316a7cfbdb8 100644
--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/arch/powerpc/kernel/trace/ftrace.c
@@ -150,6 +150,15 @@ static int ftrace_get_call_inst(struct dyn_ftrace *rec, unsigned long addr, ppc_
 	else
 		ip = rec->ip;
 
+	if (!is_offset_in_branch_range(addr - ip) && addr != FTRACE_ADDR && addr != FTRACE_REGS_ADDR) {
+		/* This can only happen with ftrace direct */
+		if (!IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS)) {
+			pr_err("0x%lx (0x%lx): Unexpected target address 0x%lx\n", ip, rec->ip, addr);
+			return -EINVAL;
+		}
+		addr = FTRACE_ADDR;
+	}
+
 	if (is_offset_in_branch_range(addr - ip))
 		/* Within range */
 		stub = addr;
diff --git a/arch/powerpc/kernel/trace/ftrace_entry.S b/arch/powerpc/kernel/trace/ftrace_entry.S
index c019380bdd6a..eea4cb3737a8 100644
--- a/arch/powerpc/kernel/trace/ftrace_entry.S
+++ b/arch/powerpc/kernel/trace/ftrace_entry.S
@@ -33,14 +33,38 @@
  * and then arrange for the ftrace function to be called.
  */
 .macro	ftrace_regs_entry allregs
-	/* Save the original return address in A's stack frame */
-	PPC_STL		r0, LRSAVE(r1)
 	/* Create a minimal stack frame for representing B */
 	PPC_STLU	r1, -STACK_FRAME_MIN_SIZE(r1)
 
 	/* Create our stack frame + pt_regs */
 	PPC_STLU	r1,-SWITCH_FRAME_SIZE(r1)
 
+	.if \allregs == 1
+	SAVE_GPRS(11, 12, r1)
+	.endif
+
+	/* Get the _mcount() call site out of LR */
+	mflr	r11
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
+	/* Load the ftrace_op */
+	PPC_LL	r12, -(MCOUNT_INSN_SIZE*2 + SZL)(r11)
+
+	/* Load direct_call from the ftrace_op */
+	PPC_LL	r12, FTRACE_OPS_DIRECT_CALL(r12)
+	PPC_LCMPI r12, 0
+	.if \allregs == 1
+	bne	.Lftrace_direct_call_regs
+	.else
+	bne	.Lftrace_direct_call
+	.endif
+#endif
+
+	/* Save the previous LR in pt_regs->link */
+	PPC_STL	r0, _LINK(r1)
+	/* Also save it in A's stack frame */
+	PPC_STL	r0, SWITCH_FRAME_SIZE+STACK_FRAME_MIN_SIZE+LRSAVE(r1)
+
 	/* Save all gprs to pt_regs */
 	SAVE_GPR(0, r1)
 	SAVE_GPRS(3, 10, r1)
@@ -54,7 +78,7 @@
 
 	.if \allregs == 1
 	SAVE_GPR(2, r1)
-	SAVE_GPRS(11, 31, r1)
+	SAVE_GPRS(13, 31, r1)
 	.else
 #if defined(CONFIG_LIVEPATCH_64) || defined(CONFIG_PPC_FTRACE_OUT_OF_LINE)
 	SAVE_GPR(14, r1)
@@ -67,20 +91,15 @@
 
 	.if \allregs == 1
 	/* Load special regs for save below */
+	mfcr	r7
 	mfmsr   r8
 	mfctr   r9
 	mfxer   r10
-	mfcr	r11
 	.else
 	/* Clear MSR to flag as ftrace_caller versus frace_regs_caller */
 	li	r8, 0
 	.endif
 
-	/* Get the _mcount() call site out of LR */
-	mflr	r7
-	/* Save the read LR in pt_regs->link */
-	PPC_STL	r0, _LINK(r1)
-
 #ifdef CONFIG_PPC64
 	/* Save callee's TOC in the ABI compliant location */
 	std	r2, STK_GOT(r1)
@@ -88,8 +107,8 @@
 #endif
 
 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS
-	/* r7 points to the instruction following the call to ftrace */
-	PPC_LL	r5, -(MCOUNT_INSN_SIZE*2 + SZL)(r7)
+	/* r11 points to the instruction following the call to ftrace */
+	PPC_LL	r5, -(MCOUNT_INSN_SIZE*2 + SZL)(r11)
 	PPC_LL	r12, FTRACE_OPS_FUNC(r5)
 	mtctr	r12
 #else /* !CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS */
@@ -105,45 +124,51 @@
 	/* Save special regs */
 	PPC_STL	r8, _MSR(r1)
 	.if \allregs == 1
+	PPC_STL	r7, _CCR(r1)
 	PPC_STL	r9, _CTR(r1)
 	PPC_STL	r10, _XER(r1)
-	PPC_STL	r11, _CCR(r1)
 	.endif
 
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
+	/* Clear orig_gpr3 to later detect ftrace_direct call */
+	li	r7, 0
+	PPC_STL	r7, ORIG_GPR3(r1)
+#endif
+
 #ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
 	/* Save our real return address in nvr for return */
 	.if \allregs == 0
 	SAVE_GPR(15, r1)
 	.endif
-	mr	r15, r7
+	mr	r15, r11
 	/*
-	 * We want the ftrace location in the function, but our lr (in r7)
+	 * We want the ftrace location in the function, but our lr (in r11)
 	 * points at the 'mtlr r0' instruction in the out of line stub.  To
 	 * recover the ftrace location, we read the branch instruction in the
 	 * stub, and adjust our lr by the branch offset.
 	 *
 	 * See ftrace_init_ool_stub() for the profile sequence.
 	 */
-	lwz	r8, MCOUNT_INSN_SIZE(r7)
+	lwz	r8, MCOUNT_INSN_SIZE(r11)
 	slwi	r8, r8, 6
 	srawi	r8, r8, 6
-	add	r3, r7, r8
+	add	r3, r11, r8
 	/*
 	 * Override our nip to point past the branch in the original function.
 	 * This allows reliable stack trace and the ftrace stack tracer to work as-is.
 	 */
-	add	r7, r3, MCOUNT_INSN_SIZE
+	add	r11, r3, MCOUNT_INSN_SIZE
 #else
 	/* Calculate ip from nip-4 into r3 for call below */
-	subi    r3, r7, MCOUNT_INSN_SIZE
+	subi    r3, r11, MCOUNT_INSN_SIZE
 #endif
 
 	/* Save NIP as pt_regs->nip */
-	PPC_STL	r7, _NIP(r1)
+	PPC_STL	r11, _NIP(r1)
 	/* Also save it in B's stackframe header for proper unwind */
-	PPC_STL	r7, LRSAVE+SWITCH_FRAME_SIZE(r1)
+	PPC_STL	r11, LRSAVE+SWITCH_FRAME_SIZE(r1)
 #if defined(CONFIG_LIVEPATCH_64) || defined(CONFIG_PPC_FTRACE_OUT_OF_LINE)
-	mr	r14, r7		/* remember old NIP */
+	mr	r14, r11	/* remember old NIP */
 #endif
 
 	/* Put the original return address in r4 as parent_ip */
@@ -154,14 +179,32 @@
 .endm
 
 .macro	ftrace_regs_exit allregs
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
+	/* Check orig_gpr3 to detect ftrace_direct call */
+	PPC_LL	r3, ORIG_GPR3(r1)
+	PPC_LCMPI cr1, r3, 0
+	mtctr	r3
+#endif
+
+	/* Restore possibly modified LR */
+	PPC_LL	r0, _LINK(r1)
+
 #ifndef CONFIG_PPC_FTRACE_OUT_OF_LINE
 	/* Load ctr with the possibly modified NIP */
 	PPC_LL	r3, _NIP(r1)
-	mtctr	r3
-
 #ifdef CONFIG_LIVEPATCH_64
 	cmpd	r14, r3		/* has NIP been altered? */
 #endif
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
+	beq	cr1,2f
+	mtlr	r3
+	b	3f
+#endif
+2:	mtctr	r3
+	mtlr	r0
+3:
+
 #else /* !CONFIG_PPC_FTRACE_OUT_OF_LINE */
 	/* Load LR with the possibly modified NIP */
 	PPC_LL	r3, _NIP(r1)
@@ -185,12 +228,6 @@
 #endif
 	.endif
 
-	/* Restore possibly modified LR */
-	PPC_LL	r0, _LINK(r1)
-#ifndef CONFIG_PPC_FTRACE_OUT_OF_LINE
-	mtlr	r0
-#endif
-
 #ifdef CONFIG_PPC64
 	/* Restore callee's TOC */
 	ld	r2, STK_GOT(r1)
@@ -203,8 +240,12 @@
         /* Based on the cmpd above, if the NIP was altered handle livepatch */
 	bne-	livepatch_handler
 #endif
+
 	/* jump after _mcount site */
 #ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
+	bnectr	cr1
+#endif
 	/*
 	 * Return with blr to keep the link stack balanced. The function profiling sequence
 	 * uses 'mtlr r0' to restore LR.
@@ -260,6 +301,21 @@ ftrace_no_trace:
 #endif
 #endif
 
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
+.Lftrace_direct_call_regs:
+	mtctr	r12
+	REST_GPRS(11, 12, r1)
+	addi	r1, r1, SWITCH_FRAME_SIZE+STACK_FRAME_MIN_SIZE
+	bctr
+.Lftrace_direct_call:
+	mtctr	r12
+	addi	r1, r1, SWITCH_FRAME_SIZE+STACK_FRAME_MIN_SIZE
+	bctr
+SYM_FUNC_START(ftrace_stub_direct_tramp)
+	blr
+SYM_FUNC_END(ftrace_stub_direct_tramp)
+#endif
+
 #ifdef CONFIG_LIVEPATCH_64
 	/*
 	 * This function runs in the mcount context, between two functions. As
-- 
2.45.2

[RFC PATCH v4 16/17] samples/ftrace: Add support for ftrace direct samples on powerpc

[Naveen N Rao]

Add powerpc 32-bit and 64-bit samples for ftrace direct. This serves to
show the sample instruction sequence to be used by ftrace direct calls
to adhere to the ftrace ABI.

On 64-bit powerpc, TOC setup requires some additional work.

Signed-off-by: Naveen N Rao <naveen@kernel.org>
---
 arch/powerpc/Kconfig                        |   2 +
 samples/ftrace/ftrace-direct-modify.c       |  85 +++++++++++++++-
 samples/ftrace/ftrace-direct-multi-modify.c | 101 +++++++++++++++++++-
 samples/ftrace/ftrace-direct-multi.c        |  79 ++++++++++++++-
 samples/ftrace/ftrace-direct-too.c          |  83 +++++++++++++++-
 samples/ftrace/ftrace-direct.c              |  69 ++++++++++++-
 6 files changed, 414 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 29aab3770415..f6ff44acf112 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -275,6 +275,8 @@ config PPC
 	select HAVE_REGS_AND_STACK_ACCESS_API
 	select HAVE_RELIABLE_STACKTRACE
 	select HAVE_RSEQ
+	select HAVE_SAMPLE_FTRACE_DIRECT	if HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
+	select HAVE_SAMPLE_FTRACE_DIRECT_MULTI	if HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
 	select HAVE_SETUP_PER_CPU_AREA		if PPC64
 	select HAVE_SOFTIRQ_ON_OWN_STACK
 	select HAVE_STACKPROTECTOR		if PPC32 && $(cc-option,-mstack-protector-guard=tls -mstack-protector-guard-reg=r2)
diff --git a/samples/ftrace/ftrace-direct-modify.c b/samples/ftrace/ftrace-direct-modify.c
index 81220390851a..cfea7a38befb 100644
--- a/samples/ftrace/ftrace-direct-modify.c
+++ b/samples/ftrace/ftrace-direct-modify.c
@@ -2,7 +2,7 @@
 #include <linux/module.h>
 #include <linux/kthread.h>
 #include <linux/ftrace.h>
-#ifndef CONFIG_ARM64
+#if !defined(CONFIG_ARM64) && !defined(CONFIG_PPC32)
 #include <asm/asm-offsets.h>
 #endif
 
@@ -199,6 +199,89 @@ asm (
 
 #endif /* CONFIG_LOONGARCH */
 
+#ifdef CONFIG_PPC
+#include <asm/ppc_asm.h>
+
+#ifdef CONFIG_PPC64
+#define STACK_FRAME_SIZE 48
+#else
+#define STACK_FRAME_SIZE 24
+#endif
+
+#if defined(CONFIG_PPC64_ELF_ABI_V2) && !defined(CONFIG_PPC_KERNEL_PCREL)
+#define PPC64_TOC_SAVE_AND_UPDATE			\
+"	std		2, 24(1)\n"			\
+"	bcl		20, 31, 1f\n"			\
+"   1:	mflr		12\n"				\
+"	ld		2, (99f - 1b)(12)\n"
+#define PPC64_TOC_RESTORE				\
+"	ld		2, 24(1)\n"
+#define PPC64_TOC					\
+"   99:	.quad		.TOC.@tocbase\n"
+#else
+#define PPC64_TOC_SAVE_AND_UPDATE ""
+#define PPC64_TOC_RESTORE ""
+#define PPC64_TOC ""
+#endif
+
+#ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
+#define PPC_FTRACE_RESTORE_LR				\
+	PPC_LL"		0, "__stringify(PPC_LR_STKOFF)"(1)\n"	\
+"	mtlr		0\n"
+#define PPC_FTRACE_RET					\
+"	blr\n"
+#else
+#define PPC_FTRACE_RESTORE_LR				\
+	PPC_LL"		0, "__stringify(PPC_LR_STKOFF)"(1)\n"	\
+"	mtctr		0\n"
+#define PPC_FTRACE_RET					\
+"	mtlr		0\n"				\
+"	bctr\n"
+#endif
+
+asm (
+"	.pushsection	.text, \"ax\", @progbits\n"
+"	.type		my_tramp1, @function\n"
+"	.globl		my_tramp1\n"
+"   my_tramp1:\n"
+	PPC_STL"	0, "__stringify(PPC_LR_STKOFF)"(1)\n"
+	PPC_STLU"	1, -"__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
+"	mflr		0\n"
+	PPC_STL"	0, "__stringify(PPC_LR_STKOFF)"(1)\n"
+	PPC_STLU"	1, -"__stringify(STACK_FRAME_SIZE)"(1)\n"
+	PPC64_TOC_SAVE_AND_UPDATE
+"	bl		my_direct_func1\n"
+	PPC64_TOC_RESTORE
+"	addi		1, 1, "__stringify(STACK_FRAME_SIZE)"\n"
+	PPC_FTRACE_RESTORE_LR
+"	addi		1, 1, "__stringify(STACK_FRAME_MIN_SIZE)"\n"
+	PPC_LL"		0, "__stringify(PPC_LR_STKOFF)"(1)\n"
+	PPC_FTRACE_RET
+"	.size		my_tramp1, .-my_tramp1\n"
+
+"	.type		my_tramp2, @function\n"
+"	.globl		my_tramp2\n"
+"   my_tramp2:\n"
+	PPC_STL"	0, "__stringify(PPC_LR_STKOFF)"(1)\n"
+	PPC_STLU"	1, -"__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
+"	mflr		0\n"
+	PPC_STL"	0, "__stringify(PPC_LR_STKOFF)"(1)\n"
+	PPC_STLU"	1, -"__stringify(STACK_FRAME_SIZE)"(1)\n"
+	PPC64_TOC_SAVE_AND_UPDATE
+"	bl		my_direct_func2\n"
+	PPC64_TOC_RESTORE
+"	addi		1, 1, "__stringify(STACK_FRAME_SIZE)"\n"
+	PPC_FTRACE_RESTORE_LR
+"	addi		1, 1, "__stringify(STACK_FRAME_MIN_SIZE)"\n"
+	PPC_LL"		0, "__stringify(PPC_LR_STKOFF)"(1)\n"
+	PPC_FTRACE_RET
+	PPC64_TOC
+"	.size		my_tramp2, .-my_tramp2\n"
+"	.popsection\n"
+);
+
+#endif /* CONFIG_PPC */
+
 static struct ftrace_ops direct;
 
 static unsigned long my_tramp = (unsigned long)my_tramp1;
diff --git a/samples/ftrace/ftrace-direct-multi-modify.c b/samples/ftrace/ftrace-direct-multi-modify.c
index f943e40d57fd..8f7986d698d8 100644
--- a/samples/ftrace/ftrace-direct-multi-modify.c
+++ b/samples/ftrace/ftrace-direct-multi-modify.c
@@ -2,7 +2,7 @@
 #include <linux/module.h>
 #include <linux/kthread.h>
 #include <linux/ftrace.h>
-#ifndef CONFIG_ARM64
+#if !defined(CONFIG_ARM64) && !defined(CONFIG_PPC32)
 #include <asm/asm-offsets.h>
 #endif
 
@@ -225,6 +225,105 @@ asm (
 
 #endif /* CONFIG_LOONGARCH */
 
+#ifdef CONFIG_PPC
+#include <asm/ppc_asm.h>
+
+#ifdef CONFIG_PPC64
+#define STACK_FRAME_SIZE 48
+#else
+#define STACK_FRAME_SIZE 24
+#endif
+
+#if defined(CONFIG_PPC64_ELF_ABI_V2) && !defined(CONFIG_PPC_KERNEL_PCREL)
+#define PPC64_TOC_SAVE_AND_UPDATE			\
+"	std		2, 24(1)\n"			\
+"	bcl		20, 31, 1f\n"			\
+"   1:	mflr		12\n"				\
+"	ld		2, (99f - 1b)(12)\n"
+#define PPC64_TOC_RESTORE				\
+"	ld		2, 24(1)\n"
+#define PPC64_TOC					\
+"   99:	.quad		.TOC.@tocbase\n"
+#else
+#define PPC64_TOC_SAVE_AND_UPDATE ""
+#define PPC64_TOC_RESTORE ""
+#define PPC64_TOC ""
+#endif
+
+#ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
+#define PPC_FTRACE_RESTORE_LR				\
+	PPC_LL"		0, "__stringify(PPC_LR_STKOFF)"(1)\n"	\
+"	mtlr		0\n"
+#define PPC_FTRACE_RET					\
+"	blr\n"
+#define PPC_FTRACE_RECOVER_IP				\
+"	lwz		8, 4(3)\n"			\
+"	li		9, 6\n"				\
+"	slw		8, 8, 9\n"			\
+"	sraw		8, 8, 9\n"			\
+"	add		3, 3, 8\n"			\
+"	addi		3, 3, 4\n"
+#else
+#define PPC_FTRACE_RESTORE_LR				\
+	PPC_LL"		0, "__stringify(PPC_LR_STKOFF)"(1)\n"	\
+"	mtctr		0\n"
+#define PPC_FTRACE_RET					\
+"	mtlr		0\n"				\
+"	bctr\n"
+#define PPC_FTRACE_RECOVER_IP ""
+#endif
+
+asm (
+"	.pushsection	.text, \"ax\", @progbits\n"
+"	.type		my_tramp1, @function\n"
+"	.globl		my_tramp1\n"
+"   my_tramp1:\n"
+	PPC_STL"	0, "__stringify(PPC_LR_STKOFF)"(1)\n"
+	PPC_STLU"	1, -"__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
+"	mflr		0\n"
+	PPC_STL"	0, "__stringify(PPC_LR_STKOFF)"(1)\n"
+	PPC_STLU"	1, -"__stringify(STACK_FRAME_SIZE)"(1)\n"
+	PPC64_TOC_SAVE_AND_UPDATE
+	PPC_STL"	3, "__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
+"	mr		3, 0\n"
+	PPC_FTRACE_RECOVER_IP
+"	bl		my_direct_func1\n"
+	PPC_LL"		3, "__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
+	PPC64_TOC_RESTORE
+"	addi		1, 1, "__stringify(STACK_FRAME_SIZE)"\n"
+	PPC_FTRACE_RESTORE_LR
+"	addi		1, 1, "__stringify(STACK_FRAME_MIN_SIZE)"\n"
+	PPC_LL"		0, "__stringify(PPC_LR_STKOFF)"(1)\n"
+	PPC_FTRACE_RET
+"	.size		my_tramp1, .-my_tramp1\n"
+
+"	.type		my_tramp2, @function\n"
+"	.globl		my_tramp2\n"
+"   my_tramp2:\n"
+	PPC_STL"	0, "__stringify(PPC_LR_STKOFF)"(1)\n"
+	PPC_STLU"	1, -"__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
+"	mflr		0\n"
+	PPC_STL"	0, "__stringify(PPC_LR_STKOFF)"(1)\n"
+	PPC_STLU"	1, -"__stringify(STACK_FRAME_SIZE)"(1)\n"
+	PPC64_TOC_SAVE_AND_UPDATE
+	PPC_STL"	3, "__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
+"	mr		3, 0\n"
+	PPC_FTRACE_RECOVER_IP
+"	bl		my_direct_func2\n"
+	PPC_LL"		3, "__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
+	PPC64_TOC_RESTORE
+"	addi		1, 1, "__stringify(STACK_FRAME_SIZE)"\n"
+	PPC_FTRACE_RESTORE_LR
+"	addi		1, 1, "__stringify(STACK_FRAME_MIN_SIZE)"\n"
+	PPC_LL"		0, "__stringify(PPC_LR_STKOFF)"(1)\n"
+	PPC_FTRACE_RET
+	PPC64_TOC
+	"	.size		my_tramp2, .-my_tramp2\n"
+"	.popsection\n"
+);
+
+#endif /* CONFIG_PPC */
+
 static unsigned long my_tramp = (unsigned long)my_tramp1;
 static unsigned long tramps[2] = {
 	(unsigned long)my_tramp1,
diff --git a/samples/ftrace/ftrace-direct-multi.c b/samples/ftrace/ftrace-direct-multi.c
index aed6df2927ce..db326c81a27d 100644
--- a/samples/ftrace/ftrace-direct-multi.c
+++ b/samples/ftrace/ftrace-direct-multi.c
@@ -4,7 +4,7 @@
 #include <linux/mm.h> /* for handle_mm_fault() */
 #include <linux/ftrace.h>
 #include <linux/sched/stat.h>
-#ifndef CONFIG_ARM64
+#if !defined(CONFIG_ARM64) && !defined(CONFIG_PPC32)
 #include <asm/asm-offsets.h>
 #endif
 
@@ -141,6 +141,83 @@ asm (
 
 #endif /* CONFIG_LOONGARCH */
 
+#ifdef CONFIG_PPC
+#include <asm/ppc_asm.h>
+
+#ifdef CONFIG_PPC64
+#define STACK_FRAME_SIZE 48
+#else
+#define STACK_FRAME_SIZE 24
+#endif
+
+#if defined(CONFIG_PPC64_ELF_ABI_V2) && !defined(CONFIG_PPC_KERNEL_PCREL)
+#define PPC64_TOC_SAVE_AND_UPDATE			\
+"	std		2, 24(1)\n"			\
+"	bcl		20, 31, 1f\n"			\
+"   1:	mflr		12\n"				\
+"	ld		2, (99f - 1b)(12)\n"
+#define PPC64_TOC_RESTORE				\
+"	ld		2, 24(1)\n"
+#define PPC64_TOC					\
+"   99:	.quad		.TOC.@tocbase\n"
+#else
+#define PPC64_TOC_SAVE_AND_UPDATE ""
+#define PPC64_TOC_RESTORE ""
+#define PPC64_TOC ""
+#endif
+
+#ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
+#define PPC_FTRACE_RESTORE_LR				\
+	PPC_LL"		0, "__stringify(PPC_LR_STKOFF)"(1)\n"	\
+"	mtlr		0\n"
+#define PPC_FTRACE_RET					\
+"	blr\n"
+#define PPC_FTRACE_RECOVER_IP				\
+"	lwz		8, 4(3)\n"			\
+"	li		9, 6\n"				\
+"	slw		8, 8, 9\n"			\
+"	sraw		8, 8, 9\n"			\
+"	add		3, 3, 8\n"			\
+"	addi		3, 3, 4\n"
+#else
+#define PPC_FTRACE_RESTORE_LR				\
+	PPC_LL"		0, "__stringify(PPC_LR_STKOFF)"(1)\n"	\
+"	mtctr		0\n"
+#define PPC_FTRACE_RET					\
+"	mtlr		0\n"				\
+"	bctr\n"
+#define PPC_FTRACE_RECOVER_IP ""
+#endif
+
+asm (
+"	.pushsection	.text, \"ax\", @progbits\n"
+"	.type		my_tramp, @function\n"
+"	.globl		my_tramp\n"
+"   my_tramp:\n"
+	PPC_STL"	0, "__stringify(PPC_LR_STKOFF)"(1)\n"
+	PPC_STLU"	1, -"__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
+"	mflr		0\n"
+	PPC_STL"	0, "__stringify(PPC_LR_STKOFF)"(1)\n"
+	PPC_STLU"	1, -"__stringify(STACK_FRAME_SIZE)"(1)\n"
+	PPC64_TOC_SAVE_AND_UPDATE
+	PPC_STL"	3, "__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
+"	mr		3, 0\n"
+	PPC_FTRACE_RECOVER_IP
+"	bl		my_direct_func\n"
+	PPC_LL"		3, "__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
+	PPC64_TOC_RESTORE
+"	addi		1, 1, "__stringify(STACK_FRAME_SIZE)"\n"
+	PPC_FTRACE_RESTORE_LR
+"	addi		1, 1, "__stringify(STACK_FRAME_MIN_SIZE)"\n"
+	PPC_LL"		0, "__stringify(PPC_LR_STKOFF)"(1)\n"
+	PPC_FTRACE_RET
+	PPC64_TOC
+"	.size		my_tramp, .-my_tramp\n"
+"	.popsection\n"
+);
+
+#endif /* CONFIG_PPC */
+
 static struct ftrace_ops direct;
 
 static int __init ftrace_direct_multi_init(void)
diff --git a/samples/ftrace/ftrace-direct-too.c b/samples/ftrace/ftrace-direct-too.c
index 6ff546a5d7eb..3d0fa260332d 100644
--- a/samples/ftrace/ftrace-direct-too.c
+++ b/samples/ftrace/ftrace-direct-too.c
@@ -3,7 +3,7 @@
 
 #include <linux/mm.h> /* for handle_mm_fault() */
 #include <linux/ftrace.h>
-#ifndef CONFIG_ARM64
+#if !defined(CONFIG_ARM64) && !defined(CONFIG_PPC32)
 #include <asm/asm-offsets.h>
 #endif
 
@@ -153,6 +153,87 @@ asm (
 
 #endif /* CONFIG_LOONGARCH */
 
+#ifdef CONFIG_PPC
+#include <asm/ppc_asm.h>
+
+#ifdef CONFIG_PPC64
+#define STACK_FRAME_SIZE 64
+#define STACK_FRAME_ARG1 32
+#define STACK_FRAME_ARG2 40
+#define STACK_FRAME_ARG3 48
+#define STACK_FRAME_ARG4 56
+#else
+#define STACK_FRAME_SIZE 32
+#define STACK_FRAME_ARG1 16
+#define STACK_FRAME_ARG2 20
+#define STACK_FRAME_ARG3 24
+#define STACK_FRAME_ARG4 28
+#endif
+
+#if defined(CONFIG_PPC64_ELF_ABI_V2) && !defined(CONFIG_PPC_KERNEL_PCREL)
+#define PPC64_TOC_SAVE_AND_UPDATE			\
+"	std		2, 24(1)\n"			\
+"	bcl		20, 31, 1f\n"			\
+"   1:	mflr		12\n"				\
+"	ld		2, (99f - 1b)(12)\n"
+#define PPC64_TOC_RESTORE				\
+"	ld		2, 24(1)\n"
+#define PPC64_TOC					\
+"   99:	.quad		.TOC.@tocbase\n"
+#else
+#define PPC64_TOC_SAVE_AND_UPDATE ""
+#define PPC64_TOC_RESTORE ""
+#define PPC64_TOC ""
+#endif
+
+#ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
+#define PPC_FTRACE_RESTORE_LR				\
+	PPC_LL"		0, "__stringify(PPC_LR_STKOFF)"(1)\n"	\
+"	mtlr		0\n"
+#define PPC_FTRACE_RET					\
+"	blr\n"
+#else
+#define PPC_FTRACE_RESTORE_LR				\
+	PPC_LL"		0, "__stringify(PPC_LR_STKOFF)"(1)\n"	\
+"	mtctr		0\n"
+#define PPC_FTRACE_RET					\
+"	mtlr		0\n"				\
+"	bctr\n"
+#endif
+
+asm (
+"	.pushsection	.text, \"ax\", @progbits\n"
+"	.type		my_tramp, @function\n"
+"	.globl		my_tramp\n"
+"   my_tramp:\n"
+	PPC_STL"	0, "__stringify(PPC_LR_STKOFF)"(1)\n"
+	PPC_STLU"	1, -"__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
+"	mflr		0\n"
+	PPC_STL"	0, "__stringify(PPC_LR_STKOFF)"(1)\n"
+	PPC_STLU"	1, -"__stringify(STACK_FRAME_SIZE)"(1)\n"
+	PPC64_TOC_SAVE_AND_UPDATE
+	PPC_STL"	3, "__stringify(STACK_FRAME_ARG1)"(1)\n"
+	PPC_STL"	4, "__stringify(STACK_FRAME_ARG2)"(1)\n"
+	PPC_STL"	5, "__stringify(STACK_FRAME_ARG3)"(1)\n"
+	PPC_STL"	6, "__stringify(STACK_FRAME_ARG4)"(1)\n"
+"	bl		my_direct_func\n"
+	PPC_LL"		6, "__stringify(STACK_FRAME_ARG4)"(1)\n"
+	PPC_LL"		5, "__stringify(STACK_FRAME_ARG3)"(1)\n"
+	PPC_LL"		4, "__stringify(STACK_FRAME_ARG2)"(1)\n"
+	PPC_LL"		3, "__stringify(STACK_FRAME_ARG1)"(1)\n"
+	PPC64_TOC_RESTORE
+"	addi		1, 1, "__stringify(STACK_FRAME_SIZE)"\n"
+	PPC_FTRACE_RESTORE_LR
+"	addi		1, 1, "__stringify(STACK_FRAME_MIN_SIZE)"\n"
+	PPC_LL"		0, "__stringify(PPC_LR_STKOFF)"(1)\n"
+	PPC_FTRACE_RET
+	PPC64_TOC
+"	.size		my_tramp, .-my_tramp\n"
+"	.popsection\n"
+);
+
+#endif /* CONFIG_PPC */
+
 static struct ftrace_ops direct;
 
 static int __init ftrace_direct_init(void)
diff --git a/samples/ftrace/ftrace-direct.c b/samples/ftrace/ftrace-direct.c
index ef0945670e1e..956834b0d19a 100644
--- a/samples/ftrace/ftrace-direct.c
+++ b/samples/ftrace/ftrace-direct.c
@@ -3,7 +3,7 @@
 
 #include <linux/sched.h> /* for wake_up_process() */
 #include <linux/ftrace.h>
-#ifndef CONFIG_ARM64
+#if !defined(CONFIG_ARM64) && !defined(CONFIG_PPC32)
 #include <asm/asm-offsets.h>
 #endif
 
@@ -134,6 +134,73 @@ asm (
 
 #endif /* CONFIG_LOONGARCH */
 
+#ifdef CONFIG_PPC
+#include <asm/ppc_asm.h>
+
+#ifdef CONFIG_PPC64
+#define STACK_FRAME_SIZE 48
+#else
+#define STACK_FRAME_SIZE 24
+#endif
+
+#if defined(CONFIG_PPC64_ELF_ABI_V2) && !defined(CONFIG_PPC_KERNEL_PCREL)
+#define PPC64_TOC_SAVE_AND_UPDATE			\
+"	std		2, 24(1)\n"			\
+"	bcl		20, 31, 1f\n"			\
+"   1:	mflr		12\n"				\
+"	ld		2, (99f - 1b)(12)\n"
+#define PPC64_TOC_RESTORE				\
+"	ld		2, 24(1)\n"
+#define PPC64_TOC					\
+"   99:	.quad		.TOC.@tocbase\n"
+#else
+#define PPC64_TOC_SAVE_AND_UPDATE ""
+#define PPC64_TOC_RESTORE ""
+#define PPC64_TOC ""
+#endif
+
+#ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
+#define PPC_FTRACE_RESTORE_LR				\
+	PPC_LL"		0, "__stringify(PPC_LR_STKOFF)"(1)\n"	\
+"	mtlr		0\n"
+#define PPC_FTRACE_RET					\
+"	blr\n"
+#else
+#define PPC_FTRACE_RESTORE_LR				\
+	PPC_LL"		0, "__stringify(PPC_LR_STKOFF)"(1)\n"	\
+"	mtctr		0\n"
+#define PPC_FTRACE_RET					\
+"	mtlr		0\n"				\
+"	bctr\n"
+#endif
+
+asm (
+"	.pushsection	.text, \"ax\", @progbits\n"
+"	.type		my_tramp, @function\n"
+"	.globl		my_tramp\n"
+"   my_tramp:\n"
+	PPC_STL"	0, "__stringify(PPC_LR_STKOFF)"(1)\n"
+	PPC_STLU"	1, -"__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
+"	mflr		0\n"
+	PPC_STL"	0, "__stringify(PPC_LR_STKOFF)"(1)\n"
+	PPC_STLU"	1, -"__stringify(STACK_FRAME_SIZE)"(1)\n"
+	PPC64_TOC_SAVE_AND_UPDATE
+	PPC_STL"	3, "__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
+"	bl		my_direct_func\n"
+	PPC_LL"		3, "__stringify(STACK_FRAME_MIN_SIZE)"(1)\n"
+	PPC64_TOC_RESTORE
+"	addi		1, 1, "__stringify(STACK_FRAME_SIZE)"\n"
+	PPC_FTRACE_RESTORE_LR
+"	addi		1, 1, "__stringify(STACK_FRAME_MIN_SIZE)"\n"
+	PPC_LL"		0, "__stringify(PPC_LR_STKOFF)"(1)\n"
+	PPC_FTRACE_RET
+	PPC64_TOC
+"	.size		my_tramp, .-my_tramp\n"
+"	.popsection\n"
+);
+
+#endif /* CONFIG_PPC */
+
 static struct ftrace_ops direct;
 
 static int __init ftrace_direct_init(void)
-- 
2.45.2

[RFC PATCH v4 17/17] powerpc64/bpf: Add support for bpf trampolines

[Naveen N Rao]

Add support for bpf_arch_text_poke() and arch_prepare_bpf_trampoline()
for 64-bit powerpc. While the code is generic, BPF trampolines are only
enabled on 64-bit powerpc. 32-bit powerpc will need testing and some
updates.

BPF Trampolines adhere to the existing ftrace ABI utilizing a
two-instruction profiling sequence, as well as the newer ABI utilizing a
three-instruction profiling sequence enabling return with a 'blr'. The
trampoline code itself closely follows x86 implementation.

BPF prog JIT is extended to mimic 64-bit powerpc approach for ftrace
having a single nop at function entry, followed by the function
profiling sequence out-of-line and a separate long branch stub for calls
to trampolines that are out of range. A dummy_tramp is provided to
simplify synchronization similar to arm64.

When attaching a bpf trampoline to a bpf prog, we can patch up to three
things:
- the nop at bpf prog entry to go to the out-of-line stub
- the instruction in the out-of-line stub to either call the bpf trampoline
directly, or to branch to the long_branch stub.
- the trampoline address before the long_branch stub.

We do not need any synchronization here since we always have a valid
branch target regardless of the order in which the above stores are
seen. dummy_tramp ensures that the long_branch stub goes to a valid
destination on other cpus, even when the branch to the long_branch stub
is seen before the updated trampoline address.

However, when detaching a bpf trampoline from a bpf prog, or if changing
the bpf trampoline address, we need synchronization to ensure that other
cpus can no longer branch into the older trampoline so that it can be
safely freed. bpf_tramp_image_put() uses rcu_tasks to ensure all cpus
make forward progress, but we still need to ensure that other cpus
execute isync (or some CSI) so that they don't go back into the
trampoline again.

Signed-off-by: Naveen N Rao <naveen@kernel.org>
---
 arch/powerpc/include/asm/ppc-opcode.h |  14 +
 arch/powerpc/net/bpf_jit.h            |  12 +
 arch/powerpc/net/bpf_jit_comp.c       | 842 +++++++++++++++++++++++++-
 arch/powerpc/net/bpf_jit_comp32.c     |   7 +-
 arch/powerpc/net/bpf_jit_comp64.c     |   7 +-
 5 files changed, 879 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/include/asm/ppc-opcode.h b/arch/powerpc/include/asm/ppc-opcode.h
index b98a9e982c03..4312bcb913a4 100644
--- a/arch/powerpc/include/asm/ppc-opcode.h
+++ b/arch/powerpc/include/asm/ppc-opcode.h
@@ -587,12 +587,26 @@
 #define PPC_RAW_MTSPR(spr, d)		(0x7c0003a6 | ___PPC_RS(d) | __PPC_SPR(spr))
 #define PPC_RAW_EIEIO()			(0x7c0006ac)
 
+/* bcl 20,31,$+4 */
+#define PPC_RAW_BCL4()			(0x429f0005)
 #define PPC_RAW_BRANCH(offset)		(0x48000000 | PPC_LI(offset))
 #define PPC_RAW_BL(offset)		(0x48000001 | PPC_LI(offset))
 #define PPC_RAW_TW(t0, a, b)		(0x7c000008 | ___PPC_RS(t0) | ___PPC_RA(a) | ___PPC_RB(b))
 #define PPC_RAW_TRAP()			PPC_RAW_TW(31, 0, 0)
 #define PPC_RAW_SETB(t, bfa)		(0x7c000100 | ___PPC_RT(t) | ___PPC_RA((bfa) << 2))
 
+#ifdef CONFIG_PPC32
+#define PPC_RAW_STL		PPC_RAW_STW
+#define PPC_RAW_STLU		PPC_RAW_STWU
+#define PPC_RAW_LL		PPC_RAW_LWZ
+#define PPC_RAW_CMPLI		PPC_RAW_CMPWI
+#else
+#define PPC_RAW_STL		PPC_RAW_STD
+#define PPC_RAW_STLU		PPC_RAW_STDU
+#define PPC_RAW_LL		PPC_RAW_LD
+#define PPC_RAW_CMPLI		PPC_RAW_CMPDI
+#endif
+
 /* Deal with instructions that older assemblers aren't aware of */
 #define	PPC_BCCTR_FLUSH		stringify_in_c(.long PPC_INST_BCCTR_FLUSH)
 #define	PPC_CP_ABORT		stringify_in_c(.long PPC_RAW_CP_ABORT)
diff --git a/arch/powerpc/net/bpf_jit.h b/arch/powerpc/net/bpf_jit.h
index cdea5dccaefe..2d04ce5a23da 100644
--- a/arch/powerpc/net/bpf_jit.h
+++ b/arch/powerpc/net/bpf_jit.h
@@ -12,6 +12,7 @@
 
 #include <asm/types.h>
 #include <asm/ppc-opcode.h>
+#include <linux/build_bug.h>
 
 #ifdef CONFIG_PPC64_ELF_ABI_V1
 #define FUNCTION_DESCR_SIZE	24
@@ -21,6 +22,9 @@
 
 #define CTX_NIA(ctx) ((unsigned long)ctx->idx * 4)
 
+#define SZL			sizeof(unsigned long)
+#define BPF_INSN_SAFETY		64
+
 #define PLANT_INSTR(d, idx, instr)					      \
 	do { if (d) { (d)[idx] = instr; } idx++; } while (0)
 #define EMIT(instr)		PLANT_INSTR(image, ctx->idx, instr)
@@ -81,6 +85,13 @@
 				EMIT(PPC_RAW_ORI(d, d, (uintptr_t)(i) &       \
 							0xffff));             \
 		} } while (0)
+#define PPC_LI_ADDR	PPC_LI64
+#define PPC64_LOAD_PACA()						      \
+	EMIT(PPC_RAW_LD(_R2, _R13, offsetof(struct paca_struct, kernel_toc)))
+#else
+#define PPC_LI64(d, i)	BUILD_BUG()
+#define PPC_LI_ADDR	PPC_LI32
+#define PPC64_LOAD_PACA() BUILD_BUG()
 #endif
 
 /*
@@ -165,6 +176,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, u32 *fimage, struct code
 		       u32 *addrs, int pass, bool extra_pass);
 void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx);
 void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx);
+void bpf_jit_build_fentry_stubs(u32 *image, struct codegen_context *ctx);
 void bpf_jit_realloc_regs(struct codegen_context *ctx);
 int bpf_jit_emit_exit_insn(u32 *image, struct codegen_context *ctx, int tmp_reg, long exit_addr);
 
diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
index 984655419da5..bed1d26e7069 100644
--- a/arch/powerpc/net/bpf_jit_comp.c
+++ b/arch/powerpc/net/bpf_jit_comp.c
@@ -22,11 +22,81 @@
 
 #include "bpf_jit.h"
 
+/* These offsets are from bpf prog end and stay the same across progs */
+static int bpf_jit_ool_stub, bpf_jit_long_branch_stub;
+
 static void bpf_jit_fill_ill_insns(void *area, unsigned int size)
 {
 	memset32(area, BREAKPOINT_INSTRUCTION, size / 4);
 }
 
+void dummy_tramp(void);
+
+asm (
+"	.pushsection .text, \"ax\", @progbits	;"
+"	.global dummy_tramp			;"
+"	.type dummy_tramp, @function		;"
+"dummy_tramp:					;"
+#ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
+"	blr					;"
+#else
+/* LR is always in r11, so we don't need a 'mflr r11' here */
+"	mtctr	11				;"
+"	mtlr	0				;"
+"	bctr					;"
+#endif
+"	.size dummy_tramp, .-dummy_tramp	;"
+"	.popsection				;"
+);
+
+void bpf_jit_build_fentry_stubs(u32 *image, struct codegen_context *ctx)
+{
+	int ool_stub_idx, long_branch_stub_idx;
+
+	/*
+	 * Out-of-line stub:
+	 *	mflr	r0
+	 *	[b|bl]	tramp
+	 *	mtlr	r0 // only with CONFIG_PPC_FTRACE_OUT_OF_LINE
+	 *	b	bpf_func + 4
+	 */
+	ool_stub_idx = ctx->idx;
+	EMIT(PPC_RAW_MFLR(_R0));
+	EMIT(PPC_RAW_NOP());
+	if (IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE))
+		EMIT(PPC_RAW_MTLR(_R0));
+	WARN_ON_ONCE(!is_offset_in_branch_range(4 - (long)ctx->idx * 4));
+	EMIT(PPC_RAW_BRANCH(4 - (long)ctx->idx * 4));
+
+	/*
+	 * Long branch stub:
+	 *	.long	<dummy_tramp_addr>
+	 *	mflr	r11
+	 *	bcl	20,31,$+4
+	 *	mflr	r12
+	 *	ld	r12, -8-SZL(r12)
+	 *	mtctr	r12
+	 *	mtlr	r11 // needed to retain ftrace ABI
+	 *	bctr
+	 */
+	if (image)
+		*((unsigned long *)&image[ctx->idx]) = (unsigned long)dummy_tramp;
+	ctx->idx += SZL / 4;
+	long_branch_stub_idx = ctx->idx;
+	EMIT(PPC_RAW_MFLR(_R11));
+	EMIT(PPC_RAW_BCL4());
+	EMIT(PPC_RAW_MFLR(_R12));
+	EMIT(PPC_RAW_LL(_R12, _R12, -8-SZL));
+	EMIT(PPC_RAW_MTCTR(_R12));
+	EMIT(PPC_RAW_MTLR(_R11));
+	EMIT(PPC_RAW_BCTR());
+
+	if (!bpf_jit_ool_stub) {
+		bpf_jit_ool_stub = (ctx->idx - ool_stub_idx) * 4;
+		bpf_jit_long_branch_stub = (ctx->idx - long_branch_stub_idx) * 4;
+	}
+}
+
 int bpf_jit_emit_exit_insn(u32 *image, struct codegen_context *ctx, int tmp_reg, long exit_addr)
 {
 	if (!exit_addr || is_offset_in_branch_range(exit_addr - (ctx->idx * 4))) {
@@ -222,7 +292,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
 
 	fp->bpf_func = (void *)fimage;
 	fp->jited = 1;
-	fp->jited_len = proglen + FUNCTION_DESCR_SIZE;
+	fp->jited_len = cgctx.idx * 4 + FUNCTION_DESCR_SIZE;
 
 	if (!fp->is_func || extra_pass) {
 		if (bpf_jit_binary_pack_finalize(fp, fhdr, hdr)) {
@@ -369,3 +439,773 @@ bool bpf_jit_supports_far_kfunc_call(void)
 {
 	return IS_ENABLED(CONFIG_PPC64);
 }
+
+void *arch_alloc_bpf_trampoline(unsigned int size)
+{
+	return bpf_prog_pack_alloc(size, bpf_jit_fill_ill_insns);
+}
+
+void arch_free_bpf_trampoline(void *image, unsigned int size)
+{
+	bpf_prog_pack_free(image, size);
+}
+
+int arch_protect_bpf_trampoline(void *image, unsigned int size)
+{
+	return 0;
+}
+
+static int invoke_bpf_prog(u32 *image, u32 *ro_image, struct codegen_context *ctx,
+			   struct bpf_tramp_link *l, int regs_off, int retval_off,
+			   int run_ctx_off, bool save_ret)
+{
+	struct bpf_prog *p = l->link.prog;
+	ppc_inst_t branch_insn;
+	u32 jmp_idx;
+	int ret = 0;
+
+	/* Save cookie */
+	if (IS_ENABLED(CONFIG_PPC64)) {
+		PPC_LI64(_R3, l->cookie);
+		EMIT(PPC_RAW_STD(_R3, _R1, run_ctx_off + offsetof(struct bpf_tramp_run_ctx,
+				 bpf_cookie)));
+	} else {
+		PPC_LI32(_R3, l->cookie >> 32);
+		PPC_LI32(_R4, l->cookie);
+		EMIT(PPC_RAW_STW(_R3, _R1,
+				 run_ctx_off + offsetof(struct bpf_tramp_run_ctx, bpf_cookie)));
+		EMIT(PPC_RAW_STW(_R4, _R1,
+				 run_ctx_off + offsetof(struct bpf_tramp_run_ctx, bpf_cookie) + 4));
+	}
+
+	/* __bpf_prog_enter(p, &bpf_tramp_run_ctx) */
+	PPC_LI_ADDR(_R3, p);
+	EMIT(PPC_RAW_MR(_R25, _R3));
+	EMIT(PPC_RAW_ADDI(_R4, _R1, run_ctx_off));
+	ret = bpf_jit_emit_func_call_rel(image, ro_image, ctx, (unsigned long)bpf_trampoline_enter(p));
+	if (ret)
+		return ret;
+
+	/* Remember prog start time returned by __bpf_prog_enter */
+	EMIT(PPC_RAW_MR(_R26, _R3));
+
+	/*
+	 * if (__bpf_prog_enter(p) == 0)
+	 *	goto skip_exec_of_prog;
+	 *
+	 * Emit a nop to be later patched with conditional branch, once offset is known
+	 */
+	EMIT(PPC_RAW_CMPLI(_R3, 0));
+	jmp_idx = ctx->idx;
+	EMIT(PPC_RAW_NOP());
+
+	/* p->bpf_func(ctx) */
+	EMIT(PPC_RAW_ADDI(_R3, _R1, regs_off));
+	if (!p->jited)
+		PPC_LI_ADDR(_R4, (unsigned long)p->insnsi);
+	if (!create_branch(&branch_insn, (u32 *)&ro_image[ctx->idx], (unsigned long)p->bpf_func,
+			   BRANCH_SET_LINK)) {
+		if (image)
+			image[ctx->idx] = ppc_inst_val(branch_insn);
+		ctx->idx++;
+	} else {
+		EMIT(PPC_RAW_LL(_R12, _R25, offsetof(struct bpf_prog, bpf_func)));
+		EMIT(PPC_RAW_MTCTR(_R12));
+		EMIT(PPC_RAW_BCTRL());
+	}
+
+	if (save_ret)
+		EMIT(PPC_RAW_STL(_R3, _R1, retval_off));
+
+	/* Fix up branch */
+	if (image) {
+		if (create_cond_branch(&branch_insn, &image[jmp_idx],
+				       (unsigned long)&image[ctx->idx], COND_EQ << 16))
+			return -EINVAL;
+		image[jmp_idx] = ppc_inst_val(branch_insn);
+	}
+
+	/* __bpf_prog_exit(p, start_time, &bpf_tramp_run_ctx) */
+	EMIT(PPC_RAW_MR(_R3, _R25));
+	EMIT(PPC_RAW_MR(_R4, _R26));
+	EMIT(PPC_RAW_ADDI(_R5, _R1, run_ctx_off));
+	ret = bpf_jit_emit_func_call_rel(image, ro_image, ctx, (unsigned long)bpf_trampoline_exit(p));
+
+	return ret;
+}
+
+static int invoke_bpf_mod_ret(u32 *image, u32 *ro_image, struct codegen_context *ctx,
+			      struct bpf_tramp_links *tl, int regs_off, int retval_off,
+			      int run_ctx_off, u32 *branches)
+{
+	int i;
+
+	/*
+	 * The first fmod_ret program will receive a garbage return value.
+	 * Set this to 0 to avoid confusing the program.
+	 */
+	EMIT(PPC_RAW_LI(_R3, 0));
+	EMIT(PPC_RAW_STL(_R3, _R1, retval_off));
+	for (i = 0; i < tl->nr_links; i++) {
+		if (invoke_bpf_prog(image, ro_image, ctx, tl->links[i], regs_off, retval_off,
+				    run_ctx_off, true))
+			return -EINVAL;
+
+		/*
+		 * mod_ret prog stored return value after prog ctx. Emit:
+		 * if (*(u64 *)(ret_val) !=  0)
+		 *	goto do_fexit;
+		 */
+		EMIT(PPC_RAW_LL(_R3, _R1, retval_off));
+		EMIT(PPC_RAW_CMPLI(_R3, 0));
+
+		/*
+		 * Save the location of the branch and generate a nop, which is
+		 * replaced with a conditional jump once do_fexit (i.e. the
+		 * start of the fexit invocation) is finalized.
+		 */
+		branches[i] = ctx->idx;
+		EMIT(PPC_RAW_NOP());
+	}
+
+	return 0;
+}
+
+static void bpf_trampoline_setup_tail_call_cnt(u32 *image, struct codegen_context *ctx,
+					       int func_frame_offset, int r4_off)
+{
+	if (IS_ENABLED(CONFIG_PPC64)) {
+		/* See bpf_jit_stack_tailcallcnt() */
+		int tailcallcnt_offset = 6 * 8;
+
+		EMIT(PPC_RAW_LL(_R3, _R1, func_frame_offset - tailcallcnt_offset));
+		EMIT(PPC_RAW_STL(_R3, _R1, -tailcallcnt_offset));
+	} else {
+		/* See bpf_jit_stack_offsetof() and BPF_PPC_TC */
+		EMIT(PPC_RAW_LL(_R4, _R1, r4_off));
+	}
+}
+
+static void bpf_trampoline_restore_tail_call_cnt(u32 *image, struct codegen_context *ctx,
+						 int func_frame_offset, int r4_off)
+{
+	if (IS_ENABLED(CONFIG_PPC64)) {
+		/* See bpf_jit_stack_tailcallcnt() */
+		int tailcallcnt_offset = 6 * 8;
+
+		EMIT(PPC_RAW_LL(_R3, _R1, -tailcallcnt_offset));
+		EMIT(PPC_RAW_STL(_R3, _R1, func_frame_offset - tailcallcnt_offset));
+	} else {
+		/* See bpf_jit_stack_offsetof() and BPF_PPC_TC */
+		EMIT(PPC_RAW_STL(_R4, _R1, r4_off));
+	}
+}
+
+static void bpf_trampoline_save_args(u32 *image, struct codegen_context *ctx, int func_frame_offset,
+				     int nr_regs, int regs_off)
+{
+	int param_save_area_offset;
+
+	param_save_area_offset = func_frame_offset; /* the two frames we alloted */
+	param_save_area_offset += STACK_FRAME_MIN_SIZE; /* param save area is past the frame header */
+
+	for (int i = 0; i < nr_regs; i++) {
+		if (i < 8) {
+			EMIT(PPC_RAW_STL(_R3 + i, _R1, regs_off + i * SZL));
+		} else {
+			EMIT(PPC_RAW_LL(_R3, _R1, param_save_area_offset + i * SZL));
+			EMIT(PPC_RAW_STL(_R3, _R1, regs_off + i * SZL));
+		}
+	}
+}
+
+/* Used when restoring just the register parameters when returning back */
+static void bpf_trampoline_restore_args_regs(u32 *image, struct codegen_context *ctx,
+					     int nr_regs, int regs_off)
+{
+	for (int i = 0; i < nr_regs && i < 8; i++)
+		EMIT(PPC_RAW_LL(_R3 + i, _R1, regs_off + i * SZL));
+}
+
+/* Used when we call into the traced function. Replicate parameter save area */
+static void bpf_trampoline_restore_args_stack(u32 *image, struct codegen_context *ctx,
+					      int func_frame_offset, int nr_regs, int regs_off)
+{
+	int param_save_area_offset;
+
+	param_save_area_offset = func_frame_offset; /* the two frames we alloted */
+	param_save_area_offset += STACK_FRAME_MIN_SIZE; /* param save area is past the frame header */
+
+	for (int i = 8; i < nr_regs; i++) {
+		EMIT(PPC_RAW_LL(_R3, _R1, param_save_area_offset + i * SZL));
+		EMIT(PPC_RAW_STL(_R3, _R1, STACK_FRAME_MIN_SIZE + i * SZL));
+	}
+	bpf_trampoline_restore_args_regs(image, ctx, nr_regs, regs_off);
+}
+
+static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *rw_image,
+					 void *rw_image_end, void *ro_image,
+					 const struct btf_func_model *m, u32 flags,
+					 struct bpf_tramp_links *tlinks,
+					 void *func_addr)
+{
+	int regs_off, nregs_off, ip_off, run_ctx_off, retval_off, nvr_off, alt_lr_off, r4_off;
+	int i, ret, nr_regs, bpf_frame_size = 0, bpf_dummy_frame_size = 0, func_frame_offset;
+	struct bpf_tramp_links *fmod_ret = &tlinks[BPF_TRAMP_MODIFY_RETURN];
+	struct bpf_tramp_links *fentry = &tlinks[BPF_TRAMP_FENTRY];
+	struct bpf_tramp_links *fexit = &tlinks[BPF_TRAMP_FEXIT];
+	struct codegen_context codegen_ctx, *ctx;
+	u32 *image = (u32 *)rw_image;
+	ppc_inst_t branch_insn;
+	u32 *branches = NULL;
+	bool save_ret;
+
+	if (IS_ENABLED(CONFIG_PPC32))
+		return -ENOTSUPP;
+
+	nr_regs = m->nr_args;
+	/* Extra registers for struct arguments */
+	for (i = 0; i < m->nr_args; i++)
+		if (m->arg_size[i] > SZL)
+			nr_regs += round_up(m->arg_size[i], SZL) / SZL - 1;
+
+	if (nr_regs > MAX_BPF_FUNC_ARGS)
+		return -ENOTSUPP;
+
+	ctx = &codegen_ctx;
+	memset(ctx, 0, sizeof(*ctx));
+
+	/*
+	 * Generated stack layout:
+	 *
+	 * func prev back chain         [ back chain        ]
+	 *                              [                   ]
+	 * bpf prog redzone/tailcallcnt [ ...               ] 64 bytes (64-bit powerpc)
+	 *                              [                   ] --
+	 * LR save area                 [ r0 save (64-bit)  ]   | header
+	 *                              [ r0 save (32-bit)  ]   |
+	 * dummy frame for unwind       [ back chain 1      ] --
+	 *                              [ padding           ] align stack frame
+	 *       r4_off                 [ r4 (tailcallcnt)  ] optional - 32-bit powerpc
+	 *       alt_lr_off             [ real lr (ool stub)] optional - actual lr
+	 *                              [ r26               ]
+	 *       nvr_off                [ r25               ] nvr save area
+	 *       retval_off             [ return value      ]
+	 *                              [ reg argN          ]
+	 *                              [ ...               ]
+	 *       regs_off               [ reg_arg1          ] prog ctx context
+	 *       nregs_off              [ args count        ]
+	 *       ip_off                 [ traced function   ]
+	 *                              [ ...               ]
+	 *       run_ctx_off            [ bpf_tramp_run_ctx ]
+	 *                              [ reg argN          ]
+	 *                              [ ...               ]
+	 *       param_save_area        [ reg_arg1          ] min 8 doublewords, per ABI
+	 *                              [ TOC save (64-bit) ] --
+	 *                              [ LR save (64-bit)  ]   | header
+	 *                              [ LR save (32-bit)  ]   |
+	 * bpf trampoline frame	        [ back chain 2      ] --
+	 *
+	 */
+
+	/* Minimum stack frame header */
+	bpf_frame_size = STACK_FRAME_MIN_SIZE;
+
+	/*
+	 * Room for parameter save area.
+	 *
+	 * Per the ABI, this is required if we call into the traced function (BPF_TRAMP_F_CALL_ORIG):
+	 * - if the function takes more than 8 arguments for the rest to spill onto the stack
+	 * - or, if the function has variadic arguments
+	 * - or, if this functions's prototype was not available to the caller
+	 *
+	 * Reserve space for at least 8 registers for now. This can be optimized later.
+	 */
+	bpf_frame_size += (nr_regs > 8 ? nr_regs : 8) * SZL;
+
+	/* Room for struct bpf_tramp_run_ctx */
+	run_ctx_off = bpf_frame_size;
+	bpf_frame_size += round_up(sizeof(struct bpf_tramp_run_ctx), SZL);
+
+	/* Room for IP address argument */
+	ip_off = bpf_frame_size;
+	if (flags & BPF_TRAMP_F_IP_ARG)
+		bpf_frame_size += SZL;
+
+	/* Room for args count */
+	nregs_off = bpf_frame_size;
+	bpf_frame_size += SZL;
+
+	/* Room for args */
+	regs_off = bpf_frame_size;
+	bpf_frame_size += nr_regs * SZL;
+
+	/* Room for return value of func_addr or fentry prog */
+	retval_off = bpf_frame_size;
+	save_ret = flags & (BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_RET_FENTRY_RET);
+	if (save_ret)
+		bpf_frame_size += SZL;
+
+	/* Room for nvr save area */
+	nvr_off = bpf_frame_size;
+	bpf_frame_size += 2 * SZL;
+
+	/* Optional save area for actual LR in case of ool ftrace */
+	if (IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE)) {
+		alt_lr_off = bpf_frame_size;
+		bpf_frame_size += SZL;
+	}
+
+	if (IS_ENABLED(CONFIG_PPC32)) {
+		if (nr_regs < 2) {
+			r4_off = bpf_frame_size;
+			bpf_frame_size += SZL;
+		} else {
+			r4_off = regs_off + SZL;
+		}
+	}
+
+	/* Padding to align stack frame, if any */
+	bpf_frame_size = round_up(bpf_frame_size, SZL * 2);
+
+	/* Dummy frame size for proper unwind - includes 64-bytes red zone for 64-bit powerpc */
+	bpf_dummy_frame_size = STACK_FRAME_MIN_SIZE + 64;
+
+	/* Offset to the traced function's stack frame */
+	func_frame_offset = bpf_dummy_frame_size + bpf_frame_size;
+
+	/* Create dummy frame for unwind, store original return value */
+	EMIT(PPC_RAW_STL(_R0, _R1, PPC_LR_STKOFF));
+	/* Protect red zone where tail call count goes */
+	EMIT(PPC_RAW_STLU(_R1, _R1, -bpf_dummy_frame_size));
+
+	/* Create our stack frame */
+	EMIT(PPC_RAW_STLU(_R1, _R1, -bpf_frame_size));
+
+	/* 64-bit: Save TOC and load kernel TOC */
+	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && !IS_ENABLED(CONFIG_PPC_KERNEL_PCREL)) {
+		EMIT(PPC_RAW_STD(_R2, _R1, 24));
+		PPC64_LOAD_PACA();
+	}
+
+	/* 32-bit: save tail call count in r4 */
+	if (IS_ENABLED(CONFIG_PPC32) && nr_regs < 2)
+		EMIT(PPC_RAW_STL(_R4, _R1, r4_off));
+
+	bpf_trampoline_save_args(image, ctx, func_frame_offset, nr_regs, regs_off);
+
+	/* Save our return address */
+	EMIT(PPC_RAW_MFLR(_R3));
+	if (IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE))
+		EMIT(PPC_RAW_STL(_R3, _R1, alt_lr_off));
+	else
+		EMIT(PPC_RAW_STL(_R3, _R1, bpf_frame_size + PPC_LR_STKOFF));
+
+	/*
+	 * Save ip address of the traced function.
+	 * We could recover this from LR, but we will need to address for OOL trampoline,
+	 * and optional GEP area.
+	 */
+	if (IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE) || flags & BPF_TRAMP_F_IP_ARG) {
+		EMIT(PPC_RAW_LWZ(_R4, _R3, 4));
+		EMIT(PPC_RAW_SLWI(_R4, _R4, 6));
+		EMIT(PPC_RAW_SRAWI(_R4, _R4, 6));
+		EMIT(PPC_RAW_ADD(_R3, _R3, _R4));
+		EMIT(PPC_RAW_ADDI(_R3, _R3, 4));
+	}
+
+	if (flags & BPF_TRAMP_F_IP_ARG)
+		EMIT(PPC_RAW_STL(_R3, _R1, ip_off));
+
+	if (IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE))
+		/* Fake our LR for unwind */
+		EMIT(PPC_RAW_STL(_R3, _R1, bpf_frame_size + PPC_LR_STKOFF));
+
+	/* Save function arg count -- see bpf_get_func_arg_cnt() */
+	EMIT(PPC_RAW_LI(_R3, nr_regs));
+	EMIT(PPC_RAW_STL(_R3, _R1, nregs_off));
+
+	/* Save nv regs */
+	EMIT(PPC_RAW_STL(_R25, _R1, nvr_off));
+	EMIT(PPC_RAW_STL(_R26, _R1, nvr_off + SZL));
+
+	if (flags & BPF_TRAMP_F_CALL_ORIG) {
+		PPC_LI_ADDR(_R3, (unsigned long)im);
+		ret = bpf_jit_emit_func_call_rel(image, ro_image, ctx, (unsigned long)__bpf_tramp_enter);
+		if (ret)
+			return ret;
+	}
+
+	for (i = 0; i < fentry->nr_links; i++)
+		if (invoke_bpf_prog(image, ro_image, ctx, fentry->links[i], regs_off, retval_off,
+				    run_ctx_off, flags & BPF_TRAMP_F_RET_FENTRY_RET))
+			return -EINVAL;
+
+	if (fmod_ret->nr_links) {
+		branches = kcalloc(fmod_ret->nr_links, sizeof(u32), GFP_KERNEL);
+		if (!branches)
+			return -ENOMEM;
+
+		if (invoke_bpf_mod_ret(image, ro_image, ctx, fmod_ret, regs_off, retval_off,
+				       run_ctx_off, branches)) {
+			ret = -EINVAL;
+			goto cleanup;
+		}
+	}
+
+	/* Call the traced function */
+	if (flags & BPF_TRAMP_F_CALL_ORIG) {
+		/*
+		 * The address in LR save area points to the correct point in the original function
+		 * with both PPC_FTRACE_OUT_OF_LINE as well as with traditional ftrace instruction
+		 * sequence
+		 */
+		EMIT(PPC_RAW_LL(_R3, _R1, bpf_frame_size + PPC_LR_STKOFF));
+		EMIT(PPC_RAW_MTCTR(_R3));
+
+		/* Replicate tail_call_cnt before calling the original BPF prog */
+		if (flags & BPF_TRAMP_F_TAIL_CALL_CTX)
+			bpf_trampoline_setup_tail_call_cnt(image, ctx, func_frame_offset, r4_off);
+
+		/* Restore args */
+		bpf_trampoline_restore_args_stack(image, ctx, func_frame_offset, nr_regs, regs_off);
+
+		/* Restore TOC for 64-bit */
+		if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && !IS_ENABLED(CONFIG_PPC_KERNEL_PCREL))
+			EMIT(PPC_RAW_LD(_R2, _R1, 24));
+		EMIT(PPC_RAW_BCTRL());
+		if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && !IS_ENABLED(CONFIG_PPC_KERNEL_PCREL))
+			PPC64_LOAD_PACA();
+
+		/* Store return value for bpf prog to access */
+		EMIT(PPC_RAW_STL(_R3, _R1, retval_off));
+
+		/* Restore updated tail_call_cnt */
+		if (flags & BPF_TRAMP_F_TAIL_CALL_CTX)
+			bpf_trampoline_restore_tail_call_cnt(image, ctx, func_frame_offset, r4_off);
+
+		/* Reserve space to patch branch instruction to skip fexit progs */
+		im->ip_after_call = &((u32 *)ro_image)[ctx->idx];
+		EMIT(PPC_RAW_NOP());
+	}
+
+	/* Update branches saved in invoke_bpf_mod_ret with address of do_fexit */
+	for (i = 0; i < fmod_ret->nr_links && image; i++) {
+		if (create_cond_branch(&branch_insn, &image[branches[i]],
+				       (unsigned long)&image[ctx->idx], COND_NE << 16)) {
+			ret = -EINVAL;
+			goto cleanup;
+		}
+
+		image[branches[i]] = ppc_inst_val(branch_insn);
+	}
+
+	for (i = 0; i < fexit->nr_links; i++)
+		if (invoke_bpf_prog(image, ro_image, ctx, fexit->links[i], regs_off, retval_off,
+				    run_ctx_off, false)) {
+			ret = -EINVAL;
+			goto cleanup;
+		}
+
+	if (flags & BPF_TRAMP_F_CALL_ORIG) {
+		im->ip_epilogue = &((u32 *)ro_image)[ctx->idx];
+		PPC_LI_ADDR(_R3, im);
+		ret = bpf_jit_emit_func_call_rel(image, ro_image, ctx, (unsigned long)__bpf_tramp_exit);
+		if (ret)
+			goto cleanup;
+	}
+
+	if (flags & BPF_TRAMP_F_RESTORE_REGS)
+		bpf_trampoline_restore_args_regs(image, ctx, nr_regs, regs_off);
+
+	/* Restore return value of func_addr or fentry prog */
+	if (save_ret)
+		EMIT(PPC_RAW_LL(_R3, _R1, retval_off));
+
+	/* Restore nv regs */
+	EMIT(PPC_RAW_LL(_R26, _R1, nvr_off + SZL));
+	EMIT(PPC_RAW_LL(_R25, _R1, nvr_off));
+
+	/* Epilogue */
+	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && !IS_ENABLED(CONFIG_PPC_KERNEL_PCREL))
+		EMIT(PPC_RAW_LD(_R2, _R1, 24));
+	if (flags & BPF_TRAMP_F_SKIP_FRAME) {
+		/* Skip the traced function and return to parent */
+		EMIT(PPC_RAW_ADDI(_R1, _R1, func_frame_offset));
+		EMIT(PPC_RAW_LL(_R0, _R1, PPC_LR_STKOFF));
+		EMIT(PPC_RAW_MTLR(_R0));
+		EMIT(PPC_RAW_BLR());
+	} else {
+		if (IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE)) {
+			EMIT(PPC_RAW_LL(_R0, _R1, alt_lr_off));
+			EMIT(PPC_RAW_MTLR(_R0));
+			EMIT(PPC_RAW_ADDI(_R1, _R1, func_frame_offset));
+			EMIT(PPC_RAW_LL(_R0, _R1, PPC_LR_STKOFF));
+			EMIT(PPC_RAW_BLR());
+		} else {
+			EMIT(PPC_RAW_LL(_R0, _R1, bpf_frame_size + PPC_LR_STKOFF));
+			EMIT(PPC_RAW_MTCTR(_R0));
+			EMIT(PPC_RAW_ADDI(_R1, _R1, func_frame_offset));
+			EMIT(PPC_RAW_LL(_R0, _R1, PPC_LR_STKOFF));
+			EMIT(PPC_RAW_MTLR(_R0));
+			EMIT(PPC_RAW_BCTR());
+		}
+	}
+
+	/* Make sure the trampoline generation logic doesn't overflow */
+	if (image && WARN_ON_ONCE(&image[ctx->idx] > (u32 *)rw_image_end - BPF_INSN_SAFETY)) {
+		ret = -EFAULT;
+		goto cleanup;
+	}
+	ret = ctx->idx * 4 + BPF_INSN_SAFETY * 4;
+
+cleanup:
+	kfree(branches);
+	return ret;
+}
+
+int arch_bpf_trampoline_size(const struct btf_func_model *m, u32 flags,
+			     struct bpf_tramp_links *tlinks, void *func_addr)
+{
+	struct bpf_tramp_image im;
+	void *image;
+	int ret;
+
+	/*
+	 * Allocate a temporary buffer for __arch_prepare_bpf_trampoline().
+	 * This will NOT cause fragmentation in direct map, as we do not
+	 * call set_memory_*() on this buffer.
+	 *
+	 * We cannot use kvmalloc here, because we need image to be in
+	 * module memory range.
+	 */
+	image = bpf_jit_alloc_exec(PAGE_SIZE);
+	if (!image)
+		return -ENOMEM;
+
+	ret = __arch_prepare_bpf_trampoline(&im, image, image + PAGE_SIZE, image,
+					    m, flags, tlinks, func_addr);
+	bpf_jit_free_exec(image);
+
+	return ret;
+}
+
+int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *image_end,
+				const struct btf_func_model *m, u32 flags,
+				struct bpf_tramp_links *tlinks,
+				void *func_addr)
+{
+	u32 size = image_end - image;
+	void *rw_image, *tmp;
+	int ret;
+
+	/*
+	 * rw_image doesn't need to be in module memory range, so we can
+	 * use kvmalloc.
+	 */
+	rw_image = kvmalloc(size, GFP_KERNEL);
+	if (!rw_image)
+		return -ENOMEM;
+
+	ret = __arch_prepare_bpf_trampoline(im, rw_image, rw_image + size, image, m,
+					    flags, tlinks, func_addr);
+	if (ret < 0)
+		goto out;
+
+	if (bpf_jit_enable > 1)
+		bpf_jit_dump(1, ret - BPF_INSN_SAFETY * 4, 1, rw_image);
+
+	tmp = bpf_arch_text_copy(image, rw_image, size);
+	if (IS_ERR(tmp))
+		ret = PTR_ERR(tmp);
+
+out:
+	kvfree(rw_image);
+	return ret;
+}
+
+static int bpf_modify_inst(void *ip, ppc_inst_t old_inst, ppc_inst_t new_inst)
+{
+	ppc_inst_t org_inst;
+
+	if (copy_inst_from_kernel_nofault(&org_inst, ip)) {
+		pr_err("0x%lx: fetching instruction failed\n", (unsigned long)ip);
+		return -EFAULT;
+	}
+
+	if (!ppc_inst_equal(org_inst, old_inst)) {
+		pr_err("0x%lx: expected (%08lx) != found (%08lx)\n",
+		       (unsigned long)ip, ppc_inst_as_ulong(old_inst), ppc_inst_as_ulong(org_inst));
+		return -EINVAL;
+	}
+
+	if (ppc_inst_equal(old_inst, new_inst))
+		return 0;
+
+	return patch_instruction(ip, new_inst);
+}
+
+static void do_isync(void *info __maybe_unused)
+{
+	isync();
+}
+
+/*
+ * A 3-step process for bpf prog entry:
+ * 1. At bpf prog entry, a single nop/b:
+ * bpf_func:
+ *	[nop|b]	ool_stub
+ * 2. Out-of-line stub:
+ * ool_stub:
+ *	mflr	r0
+ *	[b|bl]	<bpf_prog>/<long_branch_stub>
+ *	mtlr	r0 // CONFIG_PPC_FTRACE_OUT_OF_LINE only
+ *	b	bpf_func + 4
+ * 3. Long branch stub:
+ * long_branch_stub:
+ *	.long	<branch_addr>/<dummy_tramp>
+ *	mflr	r11
+ *	bcl	20,31,$+4
+ *	mflr	r12
+ *	ld	r12, -16(r12)
+ *	mtctr	r12
+ *	mtlr	r11 // needed to retain ftrace ABI
+ *	bctr
+ *
+ * dummy_tramp is used to reduce synchronization requirements.
+ *
+ * When attaching a bpf trampoline to a bpf prog, we do not need any
+ * synchronization here since we always have a valid branch target regardless
+ * of the order in which the above stores are seen. dummy_tramp ensures that
+ * the long_branch stub goes to a valid destination on other cpus, even when
+ * the branch to the long_branch stub is seen before the updated trampoline
+ * address.
+ *
+ * However, when detaching a bpf trampoline from a bpf prog, or if changing
+ * the bpf trampoline address, we need synchronization to ensure that other
+ * cpus can no longer branch into the older trampoline so that it can be
+ * safely freed. bpf_tramp_image_put() uses rcu_tasks to ensure all cpus
+ * make forward progress, but we still need to ensure that other cpus
+ * execute isync (or some CSI) so that they don't go back into the
+ * trampoline again.
+ */
+int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type poke_type,
+		       void *old_addr, void *new_addr)
+{
+	unsigned long bpf_func, bpf_func_end, size, offset;
+	ppc_inst_t old_inst, new_inst;
+	int ret = 0, branch_flags;
+	char name[KSYM_NAME_LEN];
+
+	if (IS_ENABLED(CONFIG_PPC32))
+		return -ENOTSUPP;
+
+	bpf_func = (unsigned long)ip;
+	branch_flags = poke_type == BPF_MOD_CALL ? BRANCH_SET_LINK : 0;
+
+	/* We currently only support poking bpf programs */
+	if (!__bpf_address_lookup(bpf_func, &size, &offset, name)) {
+		pr_err("%s (0x%lx): kernel/modules are not supported\n", __func__, bpf_func);
+		return -ENOTSUPP;
+	}
+
+	/*
+	 * If we are not poking at bpf prog entry, then we are simply patching in/out
+	 * an unconditional branch instruction at im->ip_after_call
+	 */
+	if (offset) {
+		if (poke_type != BPF_MOD_JUMP) {
+			pr_err("%s (0x%lx): calls are not supported in bpf prog body\n", __func__,
+			       bpf_func);
+			return -ENOTSUPP;
+		}
+		old_inst = ppc_inst(PPC_RAW_NOP());
+		if (old_addr)
+			if (create_branch(&old_inst, ip, (unsigned long)old_addr, 0))
+				return -ERANGE;
+		new_inst = ppc_inst(PPC_RAW_NOP());
+		if (new_addr)
+			if (create_branch(&new_inst, ip, (unsigned long)new_addr, 0))
+				return -ERANGE;
+		mutex_lock(&text_mutex);
+		ret = bpf_modify_inst(ip, old_inst, new_inst);
+		mutex_unlock(&text_mutex);
+
+		/* Make sure all cpus see the new instruction */
+		smp_call_function(do_isync, NULL, 1);
+		return ret;
+	}
+
+	bpf_func_end = bpf_func + size;
+
+	/* Address of the jmp/call instruction in the out-of-line stub */
+	ip = (void *)(bpf_func_end - bpf_jit_ool_stub + 4);
+
+	if (!is_offset_in_branch_range((long)ip - 4 - bpf_func)) {
+		pr_err("%s (0x%lx): bpf prog too large, ool stub out of branch range\n", __func__,
+		       bpf_func);
+		return -ERANGE;
+	}
+
+	old_inst = ppc_inst(PPC_RAW_NOP());
+	if (old_addr) {
+		if (is_offset_in_branch_range(ip - old_addr))
+			create_branch(&old_inst, ip, (unsigned long)old_addr, branch_flags);
+		else
+			create_branch(&old_inst, ip, bpf_func_end - bpf_jit_long_branch_stub,
+				      branch_flags);
+	}
+	new_inst = ppc_inst(PPC_RAW_NOP());
+	if (new_addr) {
+		if (is_offset_in_branch_range(ip - new_addr))
+			create_branch(&new_inst, ip, (unsigned long)new_addr, branch_flags);
+		else
+			create_branch(&new_inst, ip, bpf_func_end - bpf_jit_long_branch_stub,
+				      branch_flags);
+	}
+
+	mutex_lock(&text_mutex);
+
+	/*
+	 * 1. Update the address in the long branch stub:
+	 * If new_addr is out of range, we will have to use the long branch stub, so patch new_addr
+	 * here. Otherwise, revert to dummy_tramp, but only if we had patched old_addr here.
+	 */
+	if ((new_addr && !is_offset_in_branch_range(new_addr - ip)) ||
+	    (old_addr && !is_offset_in_branch_range(old_addr - ip)))
+		ret = patch_ulong((void *)(bpf_func_end - bpf_jit_long_branch_stub - SZL),
+				  (new_addr && !is_offset_in_branch_range(new_addr - ip)) ?
+				  (unsigned long)new_addr : (unsigned long)dummy_tramp);
+	if (ret)
+		goto out;
+
+	/* 2. Update the branch/call in the out-of-line stub */
+	ret = bpf_modify_inst(ip, old_inst, new_inst);
+	if (ret)
+		goto out;
+
+	/* 3. Update instruction at bpf prog entry */
+	ip = (void *)bpf_func;
+	if (!old_addr || !new_addr) {
+		if (!old_addr) {
+			old_inst = ppc_inst(PPC_RAW_NOP());
+			create_branch(&new_inst, ip, bpf_func_end - bpf_jit_ool_stub, 0);
+		} else {
+			new_inst = ppc_inst(PPC_RAW_NOP());
+			create_branch(&old_inst, ip, bpf_func_end - bpf_jit_ool_stub, 0);
+		}
+		ret = bpf_modify_inst(ip, old_inst, new_inst);
+	}
+
+out:
+	mutex_unlock(&text_mutex);
+
+	/*
+	 * Sync only if we are not attaching a trampoline to a bpf prog so the older
+	 * trampoline can be freed safely.
+	 */
+	if (old_addr)
+		smp_call_function(do_isync, NULL, 1);
+
+	return ret;
+}
diff --git a/arch/powerpc/net/bpf_jit_comp32.c b/arch/powerpc/net/bpf_jit_comp32.c
index a0c4f1bde83e..c4db278dae36 100644
--- a/arch/powerpc/net/bpf_jit_comp32.c
+++ b/arch/powerpc/net/bpf_jit_comp32.c
@@ -127,13 +127,16 @@ void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx)
 {
 	int i;
 
+	/* Instruction for trampoline attach */
+	EMIT(PPC_RAW_NOP());
+
 	/* Initialize tail_call_cnt, to be skipped if we do tail calls. */
 	if (ctx->seen & SEEN_TAILCALL)
 		EMIT(PPC_RAW_LI(_R4, 0));
 	else
 		EMIT(PPC_RAW_NOP());
 
-#define BPF_TAILCALL_PROLOGUE_SIZE	4
+#define BPF_TAILCALL_PROLOGUE_SIZE	8
 
 	if (bpf_has_stack_frame(ctx))
 		EMIT(PPC_RAW_STWU(_R1, _R1, -BPF_PPC_STACKFRAME(ctx)));
@@ -198,6 +201,8 @@ void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx)
 	bpf_jit_emit_common_epilogue(image, ctx);
 
 	EMIT(PPC_RAW_BLR());
+
+	bpf_jit_build_fentry_stubs(image, ctx);
 }
 
 /* Relative offset needs to be calculated based on final image location */
diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
index f3be024fc685..dcf339788e58 100644
--- a/arch/powerpc/net/bpf_jit_comp64.c
+++ b/arch/powerpc/net/bpf_jit_comp64.c
@@ -126,6 +126,9 @@ void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx)
 {
 	int i;
 
+	/* Instruction for trampoline attach */
+	EMIT(PPC_RAW_NOP());
+
 #ifndef CONFIG_PPC_KERNEL_PCREL
 	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2))
 		EMIT(PPC_RAW_LD(_R2, _R13, offsetof(struct paca_struct, kernel_toc)));
@@ -200,6 +203,8 @@ void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx)
 	EMIT(PPC_RAW_MR(_R3, bpf_to_ppc(BPF_REG_0)));
 
 	EMIT(PPC_RAW_BLR());
+
+	bpf_jit_build_fentry_stubs(image, ctx);
 }
 
 int bpf_jit_emit_func_call_rel(u32 *image, u32 *fimage, struct codegen_context *ctx, u64 func)
@@ -303,7 +308,7 @@ static int bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32 o
 	 */
 	int b2p_bpf_array = bpf_to_ppc(BPF_REG_2);
 	int b2p_index = bpf_to_ppc(BPF_REG_3);
-	int bpf_tailcall_prologue_size = 8;
+	int bpf_tailcall_prologue_size = 12;
 
 	if (!IS_ENABLED(CONFIG_PPC_KERNEL_PCREL) && IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2))
 		bpf_tailcall_prologue_size += 4; /* skip past the toc load */
-- 
2.45.2