linux-trace-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Hari Bathini <hbathini@linux.ibm.com>
To: linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
	bpf@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
	linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: Michael Ellerman <mpe@ellerman.id.au>,
	"Naveen N. Rao" <naveen@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Nicholas Piggin <npiggin@gmail.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Andrii Nakryiko <andrii@kernel.org>,
	Christophe Leroy <christophe.leroy@csgroup.eu>,
	Vishal Chourasia <vishalc@linux.ibm.com>,
	Mahesh J Salgaonkar <mahesh@linux.ibm.com>
Subject: [PATCH v6 13/17] powerpc64/ftrace: Support .text larger than 32MB with out-of-line stubs
Date: Fri, 18 Oct 2024 23:06:28 +0530	[thread overview]
Message-ID: <20241018173632.277333-14-hbathini@linux.ibm.com> (raw)
In-Reply-To: <20241018173632.277333-1-hbathini@linux.ibm.com>

From: Naveen N Rao <naveen@kernel.org>

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>
Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
---

Changes in v6:
* Updated with Masahiro's suggestions at
  https://lore.kernel.org/all/CAK7LNAREkj5OQ_HA2H=iV_32qdOcaguCOBKV1j+dJW0YaQh3UA@mail.gmail.com/


 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                |  3 ++-
 arch/powerpc/tools/ftrace-gen-ool-stubs.sh | 19 +++++++++++++------
 6 files changed, 56 insertions(+), 13 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 26e3060e44f4..2e347f682c15 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -573,6 +573,18 @@ config PPC_FTRACE_OUT_OF_LINE
 	def_bool PPC64 && ARCH_USING_PATCHABLE_FUNCTION_ENTRY
 	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"
+	depends on PPC_FTRACE_OUT_OF_LINE
+	default 32768
+	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 bdbafc668b20..28f3590ca780 100644
--- a/arch/powerpc/include/asm/ftrace.h
+++ b/arch/powerpc/include/asm/ftrace.h
@@ -138,8 +138,10 @@ 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 1fee074388cc..bee2c54a8c04 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 5b2fc6483dce..a6bf7f841040 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 d2e7ecd5f46f..e1f7afcd9fdf 100644
--- a/arch/powerpc/tools/Makefile
+++ b/arch/powerpc/tools/Makefile
@@ -1,7 +1,8 @@
 # SPDX-License-Identifier: GPL-2.0-or-later
 
 quiet_cmd_gen_ftrace_ool_stubs = GEN     $@
-      cmd_gen_ftrace_ool_stubs = $< "$(CONFIG_64BIT)" "$(OBJDUMP)" vmlinux.o $@
+	cmd_gen_ftrace_ool_stubs = $< "$(CONFIG_PPC_FTRACE_OUT_OF_LINE_NUM_RESERVE)" "$(CONFIG_64BIT)" \
+				   "$(OBJDUMP)" vmlinux.o $@
 
 $(obj)/vmlinux.arch.S: $(src)/ftrace-gen-ool-stubs.sh vmlinux.o FORCE
 	$(call if_changed,gen_ftrace_ool_stubs)
diff --git a/arch/powerpc/tools/ftrace-gen-ool-stubs.sh b/arch/powerpc/tools/ftrace-gen-ool-stubs.sh
index 96e1ca5803e4..3ea0f23f2501 100755
--- a/arch/powerpc/tools/ftrace-gen-ool-stubs.sh
+++ b/arch/powerpc/tools/ftrace-gen-ool-stubs.sh
@@ -4,10 +4,11 @@
 # Error out on error
 set -e
 
-is_64bit="$1"
-objdump="$2"
-vmlinux_o="$3"
-arch_vmlinux_S="$4"
+num_ool_stubs_text_builtin="$1"
+is_64bit="$2"
+objdump="$3"
+vmlinux_o="$4"
+arch_vmlinux_S="$5"
 
 RELOCATION=R_PPC64_ADDR64
 if [ -z "$is_64bit" ]; then
@@ -19,15 +20,21 @@ num_ool_stubs_text=$($objdump -r -j __patchable_function_entries "$vmlinux_o" |
 num_ool_stubs_inittext=$($objdump -r -j __patchable_function_entries "$vmlinux_o" |
 			 grep ".init.text" | grep -c "$RELOCATION")
 
+if [ "$num_ool_stubs_text" -gt "$num_ool_stubs_text_builtin" ]; then
+	num_ool_stubs_text_end=$((num_ool_stubs_text - num_ool_stubs_text_builtin))
+else
+	num_ool_stubs_text_end=0
+fi
+
 cat > "$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
 
-- 
2.47.0


  parent reply	other threads:[~2024-10-18 17:38 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-10-18 17:36 [PATCH v6 00/17] powerpc: Core ftrace rework, support for ftrace direct and bpf trampolines Hari Bathini
2024-10-18 17:36 ` [PATCH v6 01/17] powerpc/trace: Account for -fpatchable-function-entry support by toolchain Hari Bathini
2024-10-18 17:36 ` [PATCH v6 02/17] powerpc/kprobes: Use ftrace to determine if a probe is at function entry Hari Bathini
2024-10-18 17:36 ` [PATCH v6 03/17] powerpc64/ftrace: Nop out additional 'std' instruction emitted by gcc v5.x Hari Bathini
2024-10-18 17:36 ` [PATCH v6 04/17] powerpc32/ftrace: Unify 32-bit and 64-bit ftrace entry code Hari Bathini
2024-10-18 17:36 ` [PATCH v6 05/17] powerpc/module_64: Convert #ifdef to IS_ENABLED() Hari Bathini
2024-10-18 17:36 ` [PATCH v6 06/17] powerpc/ftrace: Remove pointer to struct module from dyn_arch_ftrace Hari Bathini
2024-10-18 17:36 ` [PATCH v6 07/17] powerpc/ftrace: Skip instruction patching if the instructions are the same Hari Bathini
2024-10-18 17:36 ` [PATCH v6 08/17] powerpc/ftrace: Move ftrace stub used for init text before _einittext Hari Bathini
2024-10-18 17:36 ` [PATCH v6 09/17] powerpc64/bpf: Fold bpf_jit_emit_func_call_hlp() into bpf_jit_emit_func_call_rel() Hari Bathini
2024-10-18 17:36 ` [PATCH v6 10/17] powerpc/ftrace: Add a postlink script to validate function tracer Hari Bathini
2024-10-18 17:36 ` [PATCH v6 11/17] kbuild: Add generic hook for architectures to use before the final vmlinux link Hari Bathini
2024-10-27  9:14   ` Masahiro Yamada
2024-10-18 17:36 ` [PATCH v6 12/17] powerpc64/ftrace: Move ftrace sequence out of line Hari Bathini
2024-10-27  9:21   ` Masahiro Yamada
2024-10-18 17:36 ` Hari Bathini [this message]
2024-10-27  9:17   ` [PATCH v6 13/17] powerpc64/ftrace: Support .text larger than 32MB with out-of-line stubs Masahiro Yamada
2024-10-18 17:36 ` [PATCH v6 14/17] powerpc/ftrace: Add support for DYNAMIC_FTRACE_WITH_CALL_OPS Hari Bathini
2024-10-18 17:36 ` [PATCH v6 15/17] powerpc/ftrace: Add support for DYNAMIC_FTRACE_WITH_DIRECT_CALLS Hari Bathini
2024-10-18 17:36 ` [PATCH v6 16/17] samples/ftrace: Add support for ftrace direct samples on powerpc Hari Bathini
2024-10-18 17:36 ` [PATCH v6 17/17] powerpc64/bpf: Add support for bpf trampolines Hari Bathini
2024-10-28  2:23   ` Michael Ellerman
2024-10-29  6:44     ` Hari Bathini

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20241018173632.277333-14-hbathini@linux.ibm.com \
    --to=hbathini@linux.ibm.com \
    --cc=andrii@kernel.org \
    --cc=ast@kernel.org \
    --cc=bpf@vger.kernel.org \
    --cc=christophe.leroy@csgroup.eu \
    --cc=daniel@iogearbox.net \
    --cc=linux-kbuild@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-trace-kernel@vger.kernel.org \
    --cc=linuxppc-dev@lists.ozlabs.org \
    --cc=mahesh@linux.ibm.com \
    --cc=mark.rutland@arm.com \
    --cc=masahiroy@kernel.org \
    --cc=mhiramat@kernel.org \
    --cc=mpe@ellerman.id.au \
    --cc=naveen@kernel.org \
    --cc=npiggin@gmail.com \
    --cc=rostedt@goodmis.org \
    --cc=vishalc@linux.ibm.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).