[PATCH v21 12/20] s390/tracing: Enable HAVE_FTRACE_GRAPH_FUNC

Masami Hiramatsu (Google)
2024-12-10T02:11:28Z

From: Sven Schnelle <svens@linux.ibm.com>

Add ftrace_graph_func() which is required for fprobe to access registers.
This also eliminates the need for calling prepare_ftrace_return() from
ftrace_caller().

Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
---
Changes in v19:
- Newly added.
---
arch/s390/Kconfig | 1 +
arch/s390/include/asm/ftrace.h | 5 ++++
arch/s390/kernel/entry.h | 1 -
arch/s390/kernel/ftrace.c | 48 ++++++++++++----------------------------
arch/s390/kernel/mcount.S | 11 ---------
5 files changed, 20 insertions(+), 46 deletions(-)

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index d8eee56c10b6..622ea2e9a87e 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -190,6 +190,7 @@ config S390
select HAVE_EFFICIENT_UNALIGNED_ACCESS
select HAVE_GUP_FAST
select HAVE_FENTRY
+ select HAVE_FTRACE_GRAPH_FUNC
select HAVE_FTRACE_MCOUNT_RECORD
select HAVE_FUNCTION_ARG_ACCESS_API
select HAVE_FUNCTION_ERROR_INJECTION
diff --git a/arch/s390/include/asm/ftrace.h b/arch/s390/include/asm/ftrace.h
index 5b7cb49c41ee..fd3f0fe9f7b3 100644
--- a/arch/s390/include/asm/ftrace.h
+++ b/arch/s390/include/asm/ftrace.h
@@ -39,6 +39,7 @@ struct dyn_arch_ftrace { };

struct module;
struct dyn_ftrace;
+struct ftrace_ops;

bool ftrace_need_init_nop(void);
#define ftrace_need_init_nop ftrace_need_init_nop
@@ -122,6 +123,10 @@ static inline bool arch_syscall_match_sym_name(const char *sym,
return !strcmp(sym + 7, name) || !strcmp(sym + 8, name);
}

+void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
+ struct ftrace_ops *op, struct ftrace_regs *fregs);
+#define ftrace_graph_func ftrace_graph_func
+
#endif /* __ASSEMBLY__ */

#ifdef CONFIG_FUNCTION_TRACER
diff --git a/arch/s390/kernel/entry.h b/arch/s390/kernel/entry.h
index 21969520f947..a1f28879c87e 100644
--- a/arch/s390/kernel/entry.h
+++ b/arch/s390/kernel/entry.h
@@ -41,7 +41,6 @@ void do_restart(void *arg);
void __init startup_init(void);
void die(struct pt_regs *regs, const char *str);
int setup_profiling_timer(unsigned int multiplier);
-unsigned long prepare_ftrace_return(unsigned long parent, unsigned long sp, unsigned long ip);

struct s390_mmap_arg_struct;
struct fadvise64_64_args;
diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c
index 51439a71e392..c0b2c97efefb 100644
--- a/arch/s390/kernel/ftrace.c
+++ b/arch/s390/kernel/ftrace.c
@@ -261,43 +261,23 @@ void ftrace_arch_code_modify_post_process(void)
}

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
-/*
- * Hook the return address and push it in the stack of return addresses
- * in current thread info.
- */
-unsigned long prepare_ftrace_return(unsigned long ra, unsigned long sp,
- unsigned long ip)
-{
- if (unlikely(ftrace_graph_is_dead()))
- goto out;
- if (unlikely(atomic_read(&current->tracing_graph_pause)))
- goto out;
- ip -= MCOUNT_INSN_SIZE;
- if (!function_graph_enter(ra, ip, 0, (void *) sp))
- ra = (unsigned long) return_to_handler;
-out:
- return ra;
-}
-NOKPROBE_SYMBOL(prepare_ftrace_return);

-/*
- * Patch the kernel code at ftrace_graph_caller location. The instruction
- * there is branch relative on condition. To enable the ftrace graph code
- * block, we simply patch the mask field of the instruction to zero and
- * turn the instruction into a nop.
- * To disable the ftrace graph code the mask field will be patched to
- * all ones, which turns the instruction into an unconditional branch.
- */
-int ftrace_enable_ftrace_graph_caller(void)
+void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
+ struct ftrace_ops *op, struct ftrace_regs *fregs)
{
- /* Expect brc 0xf,... */
- return ftrace_patch_branch_mask(ftrace_graph_caller, 0xa7f4, false);
-}
+ unsigned long *parent = &arch_ftrace_regs(fregs)->regs.gprs[14];
+ int bit;

-int ftrace_disable_ftrace_graph_caller(void)
-{
- /* Expect brc 0x0,... */
- return ftrace_patch_branch_mask(ftrace_graph_caller, 0xa704, true);
+ if (unlikely(ftrace_graph_is_dead()))
+ return;
+ if (unlikely(atomic_read(&current->tracing_graph_pause)))
+ return;
+ bit = ftrace_test_recursion_trylock(ip, *parent);
+ if (bit < 0)
+ return;
+ if (!function_graph_enter_regs(*parent, ip, 0, parent, fregs))
+ *parent = (unsigned long)&return_to_handler;
+ ftrace_test_recursion_unlock(bit);
}

#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
diff --git a/arch/s390/kernel/mcount.S b/arch/s390/kernel/mcount.S
index 2b628aa3d809..1fec370fecf4 100644
--- a/arch/s390/kernel/mcount.S
+++ b/arch/s390/kernel/mcount.S
@@ -104,17 +104,6 @@ SYM_CODE_START(ftrace_common)
lgr %r3,%r14
la %r5,STACK_FREGS(%r15)
BASR_EX %r14,%r1
-#ifdef CONFIG_FUNCTION_GRAPH_TRACER
-# The j instruction gets runtime patched to a nop instruction.
-# See ftrace_enable_ftrace_graph_caller.
-SYM_INNER_LABEL(ftrace_graph_caller, SYM_L_GLOBAL)
- j .Lftrace_graph_caller_end
- lmg %r2,%r3,(STACK_FREGS_PTREGS_GPRS+14*8)(%r15)
- lg %r4,(STACK_FREGS_PTREGS_PSW+8)(%r15)
- brasl %r14,prepare_ftrace_return
- stg %r2,(STACK_FREGS_PTREGS_GPRS+14*8)(%r15)
-.Lftrace_graph_caller_end:
-#endif
lg %r0,(STACK_FREGS_PTREGS_PSW+8)(%r15)
#ifdef MARCH_HAS_Z196_FEATURES
ltg %r1,STACK_FREGS_PTREGS_ORIG_GPR2(%r15)