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Message-ID: <20250703154916.48e3ada7@gandalf.local.home>
Date: Thu, 3 Jul 2025 15:49:16 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: LKML <linux-kernel@...r.kernel.org>, Linux trace kernel
<linux-trace-kernel@...r.kernel.org>, Masami Hiramatsu
<mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Mark Rutland <mark.rutland@....com>, Alexandre Ghiti <alex@...ti.fr>,
ChenMiao <chenmiao.ku@...il.com>, linux-arch@...r.kernel.org
Subject: Re: [RFC][PATCH] ftrace: Make DYNAMIC_FTRACE always enabled for
architectures that support it
On Thu, 3 Jul 2025 15:26:43 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:
> I should look to see what hasn't been ported to every architecture that
> supports ftrace and remove the configs that are now universal.
HAVE_FTRACE_MCUONT_RECORD looks like a candidate for removal:
$ git grep -e HAVE_FTRACE_MCOUNT -e HAVE_FUNCTION_TRACER arch
arch/arm/Kconfig: select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL
arch/arm/Kconfig: select HAVE_FUNCTION_TRACER if !XIP_KERNEL
arch/arm64/Kconfig: select HAVE_FTRACE_MCOUNT_RECORD
arch/arm64/Kconfig: select HAVE_FUNCTION_TRACER
arch/csky/Kconfig: select HAVE_FUNCTION_TRACER
arch/csky/Kconfig: select HAVE_FTRACE_MCOUNT_RECORD
arch/loongarch/Kconfig: select HAVE_FTRACE_MCOUNT_RECORD
arch/loongarch/Kconfig: select HAVE_FUNCTION_TRACER
arch/microblaze/Kconfig: select HAVE_FTRACE_MCOUNT_RECORD
arch/microblaze/Kconfig: select HAVE_FUNCTION_TRACER
arch/mips/Kconfig: select HAVE_FTRACE_MCOUNT_RECORD
arch/mips/Kconfig: select HAVE_FUNCTION_TRACER
arch/parisc/Kconfig: select HAVE_FUNCTION_TRACER
arch/parisc/Kconfig: select HAVE_FTRACE_MCOUNT_RECORD if HAVE_DYNAMIC_FTRACE
arch/powerpc/Kconfig: select HAVE_FTRACE_MCOUNT_RECORD
arch/powerpc/Kconfig: select HAVE_FUNCTION_TRACER if !COMPILE_TEST && (PPC64 || (PPC32 && CC_IS_GCC))
arch/riscv/Kconfig: select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL
arch/riscv/Kconfig: select HAVE_FUNCTION_TRACER if !XIP_KERNEL
arch/s390/Kconfig: select HAVE_FTRACE_MCOUNT_RECORD
arch/s390/Kconfig: select HAVE_FUNCTION_TRACER
arch/sh/Kconfig: select HAVE_FUNCTION_TRACER
arch/sh/Kconfig: select HAVE_FTRACE_MCOUNT_RECORD
arch/sparc/Kconfig: select HAVE_FUNCTION_TRACER
arch/sparc/Kconfig: select HAVE_FTRACE_MCOUNT_RECORD
arch/x86/Kconfig: select HAVE_FTRACE_MCOUNT_RECORD
arch/x86/Kconfig: select HAVE_FUNCTION_TRACER
arch/xtensa/Kconfig: select HAVE_FUNCTION_TRACER
HAVE_FTRACE_MCOUNT_RECORD only means something if HAVE_FUNCTION_TRACER is
set. Arm and riscv have the same dependencies for both.
It is also only meaningful for HAVE_DYNAMIC_FTRACE, so parisc is fine.
But it appears that xtensa is the only one that doesn't select it. But it
is also the only arch that doesn't support DYNAMIC_FTRACE either so that's
fine. The HAVE_FTRACE_MCOUNT_RECORD can be replaced by HAVE_DYNAMIC_FTRACE,
as MCOUNT_RECORD is what is used to create the sections needed for
DYNAMIC_FTRACE.
In fact the config has:
config FTRACE_MCOUNT_RECORD
def_bool y
depends on DYNAMIC_FTRACE
depends on HAVE_FTRACE_MCOUNT_RECORD
Now this config is only used for adding a section in vmlinux.lds. Thus, we
can remove the MCOUNT_RECORD configs and just use CONFIG_DYNAMIC_FTRACE
instead.
Something like below. I haven tested it. I would need to compile every
arch. But I think this would work.
-- Steve
diff --git a/Documentation/trace/ftrace-design.rst b/Documentation/trace/ftrace-design.rst
index dc82d64b3a44..8f4fab3f9324 100644
--- a/Documentation/trace/ftrace-design.rst
+++ b/Documentation/trace/ftrace-design.rst
@@ -238,19 +238,15 @@ You need very few things to get the syscalls tracing in an arch.
- Tag this arch as HAVE_SYSCALL_TRACEPOINTS.
-HAVE_FTRACE_MCOUNT_RECORD
--------------------------
+HAVE_DYNAMIC_FTRACE
+-------------------
See scripts/recordmcount.pl for more info. Just fill in the arch-specific
details for how to locate the addresses of mcount call sites via objdump.
This option doesn't make much sense without also implementing dynamic ftrace.
-
-HAVE_DYNAMIC_FTRACE
--------------------
-
-You will first need HAVE_FTRACE_MCOUNT_RECORD and HAVE_FUNCTION_TRACER, so
-scroll your reader back up if you got over eager.
+You will first need HAVE_FUNCTION_TRACER, so scroll your reader back up if you
+got over eager.
Once those are out of the way, you will need to implement:
- asm/ftrace.h:
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 3072731fe09c..33cc9dbb7f68 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -107,7 +107,6 @@ config ARM
select HAVE_EFFICIENT_UNALIGNED_ACCESS if (CPU_V6 || CPU_V6K || CPU_V7) && MMU
select HAVE_EXIT_THREAD
select HAVE_GUP_FAST if ARM_LPAE
- select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL
select HAVE_FUNCTION_ERROR_INJECTION
select HAVE_FUNCTION_GRAPH_TRACER
select HAVE_FUNCTION_TRACER if !XIP_KERNEL
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 55fc331af337..f943a07db139 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -223,7 +223,6 @@ config ARM64
select HAVE_EFFICIENT_UNALIGNED_ACCESS
select HAVE_GUP_FAST
select HAVE_FTRACE_GRAPH_FUNC
- select HAVE_FTRACE_MCOUNT_RECORD
select HAVE_FUNCTION_TRACER
select HAVE_FUNCTION_ERROR_INJECTION
select HAVE_FUNCTION_GRAPH_FREGS
diff --git a/arch/csky/Kconfig b/arch/csky/Kconfig
index acc431c331b0..4331313a42ff 100644
--- a/arch/csky/Kconfig
+++ b/arch/csky/Kconfig
@@ -80,7 +80,6 @@ config CSKY
select HAVE_FUNCTION_TRACER
select HAVE_FUNCTION_GRAPH_TRACER
select HAVE_FUNCTION_ERROR_INJECTION
- select HAVE_FTRACE_MCOUNT_RECORD
select HAVE_KERNEL_GZIP
select HAVE_KERNEL_LZO
select HAVE_KERNEL_LZMA
diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 4b19f93379a1..bead8266dc5c 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -144,7 +144,6 @@ config LOONGARCH
select HAVE_EXIT_THREAD
select HAVE_GUP_FAST
select HAVE_FTRACE_GRAPH_FUNC
- select HAVE_FTRACE_MCOUNT_RECORD
select HAVE_FUNCTION_ARG_ACCESS_API
select HAVE_FUNCTION_ERROR_INJECTION
select HAVE_FUNCTION_GRAPH_FREGS
diff --git a/arch/microblaze/Kconfig b/arch/microblaze/Kconfig
index f18ec02ddeb2..484ebb3baedf 100644
--- a/arch/microblaze/Kconfig
+++ b/arch/microblaze/Kconfig
@@ -28,7 +28,6 @@ config MICROBLAZE
select HAVE_DEBUG_KMEMLEAK
select HAVE_DMA_CONTIGUOUS
select HAVE_DYNAMIC_FTRACE
- select HAVE_FTRACE_MCOUNT_RECORD
select HAVE_FUNCTION_GRAPH_TRACER
select HAVE_FUNCTION_TRACER
select HAVE_PAGE_SIZE_4KB
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 1e48184ecf1e..268730824f75 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -73,7 +73,6 @@ config MIPS
select HAVE_EBPF_JIT if !CPU_MICROMIPS
select HAVE_EXIT_THREAD
select HAVE_GUP_FAST
- select HAVE_FTRACE_MCOUNT_RECORD
select HAVE_FUNCTION_GRAPH_TRACER
select HAVE_FUNCTION_TRACER
select HAVE_GCC_PLUGINS
diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
index fcc5973f7519..2efa4b08b7b8 100644
--- a/arch/parisc/Kconfig
+++ b/arch/parisc/Kconfig
@@ -81,7 +81,6 @@ config PARISC
select HAVE_KPROBES
select HAVE_KRETPROBES
select HAVE_DYNAMIC_FTRACE if $(cc-option,-fpatchable-function-entry=1,1)
- select HAVE_FTRACE_MCOUNT_RECORD if HAVE_DYNAMIC_FTRACE
select FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY if DYNAMIC_FTRACE
select HAVE_KPROBES_ON_FTRACE
select HAVE_DYNAMIC_FTRACE_WITH_REGS
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index c3e0cc83f120..cb4fb8d73300 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -246,7 +246,6 @@ config PPC
select HAVE_EFFICIENT_UNALIGNED_ACCESS
select HAVE_GUP_FAST
select HAVE_FTRACE_GRAPH_FUNC
- select HAVE_FTRACE_MCOUNT_RECORD
select HAVE_FUNCTION_ARG_ACCESS_API
select HAVE_FUNCTION_DESCRIPTORS if PPC64_ELF_ABI_V1
select HAVE_FUNCTION_ERROR_INJECTION
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 36061f4732b7..cd1cec255015 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -158,7 +158,6 @@ config RISCV
select HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS if (DYNAMIC_FTRACE_WITH_ARGS && !CFI_CLANG)
select HAVE_DYNAMIC_FTRACE_WITH_ARGS if HAVE_DYNAMIC_FTRACE
select HAVE_FTRACE_GRAPH_FUNC
- select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL
select HAVE_FUNCTION_GRAPH_TRACER if HAVE_DYNAMIC_FTRACE_WITH_ARGS
select HAVE_FUNCTION_GRAPH_FREGS
select HAVE_FUNCTION_TRACER if !XIP_KERNEL
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 0c16dc443e2f..d956e85f0465 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -199,7 +199,6 @@ config S390
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
select HAVE_FUNCTION_GRAPH_FREGS
diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
index 89185af7bcc9..d5795067befa 100644
--- a/arch/sh/Kconfig
+++ b/arch/sh/Kconfig
@@ -40,7 +40,6 @@ config SUPERH
select HAVE_GUP_FAST if MMU
select HAVE_FUNCTION_GRAPH_TRACER
select HAVE_FUNCTION_TRACER
- select HAVE_FTRACE_MCOUNT_RECORD
select HAVE_HW_BREAKPOINT
select HAVE_IOREMAP_PROT if MMU && !X2TLB
select HAVE_KERNEL_BZIP2
diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
index 0f88123925a4..f307e730446c 100644
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -78,7 +78,6 @@ config SPARC64
select MMU_GATHER_NO_FLUSH_CACHE
select HAVE_ARCH_TRANSPARENT_HUGEPAGE
select HAVE_DYNAMIC_FTRACE
- select HAVE_FTRACE_MCOUNT_RECORD
select HAVE_PAGE_SIZE_8KB
select HAVE_SYSCALL_TRACEPOINTS
select HAVE_CONTEXT_TRACKING_USER
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 5862433c81e1..2fc0d54ce634 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -244,7 +244,6 @@ config X86
select HAVE_GUP_FAST
select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
select HAVE_FTRACE_GRAPH_FUNC if HAVE_FUNCTION_GRAPH_TRACER
- select HAVE_FTRACE_MCOUNT_RECORD
select HAVE_FUNCTION_GRAPH_FREGS if HAVE_FUNCTION_GRAPH_TRACER
select HAVE_FUNCTION_GRAPH_TRACER if X86_32 || (X86_64 && DYNAMIC_FTRACE)
select HAVE_FUNCTION_TRACER
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index fa5f19b8d53a..ae2d2359b79e 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -167,7 +167,7 @@ defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG)
#define FTRACE_STUB_HACK
#endif
-#ifdef CONFIG_FTRACE_MCOUNT_RECORD
+#ifdef CONFIG_DYNAMIC_FTRACE
/*
* The ftrace call sites are logged to a section whose name depends on the
* compiler option used. A given kernel image will only use one, AKA
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index b672ca15f265..7ded7df6e9b5 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -1108,7 +1108,7 @@ static __always_inline unsigned long get_lock_parent_ip(void)
# define trace_preempt_off(a0, a1) do { } while (0)
#endif
-#ifdef CONFIG_FTRACE_MCOUNT_RECORD
+#ifdef CONFIG_DYNAMIC_FTRACE
extern void ftrace_init(void);
#ifdef CC_USING_PATCHABLE_FUNCTION_ENTRY
#define FTRACE_CALLSITE_SECTION "__patchable_function_entries"
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 1cce1f6410a9..989315dabb86 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -373,9 +373,9 @@ ftrace_vprintk(const char *fmt, va_list ap)
static inline void ftrace_dump(enum ftrace_dump_mode oops_dump_mode) { }
#endif /* CONFIG_TRACING */
-/* Rebuild everything on CONFIG_FTRACE_MCOUNT_RECORD */
-#ifdef CONFIG_FTRACE_MCOUNT_RECORD
-# define REBUILD_DUE_TO_FTRACE_MCOUNT_RECORD
+/* Rebuild everything on CONFIG_DYNAMIC_FTRACE */
+#ifdef CONFIG_DYNAMIC_FTRACE
+# define REBUILD_DUE_TO_DYNAMIC_FTRACE
#endif
/* Permissions on a sysfs file: you didn't miss the 0 prefix did you? */
diff --git a/include/linux/module.h b/include/linux/module.h
index 5faa1fb1f4b4..800e6fde9bf7 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -539,7 +539,7 @@ struct module {
struct trace_eval_map **trace_evals;
unsigned int num_trace_evals;
#endif
-#ifdef CONFIG_FTRACE_MCOUNT_RECORD
+#ifdef CONFIG_DYNAMIC_FTRACE
unsigned int num_ftrace_callsites;
unsigned long *ftrace_callsites;
#endif
diff --git a/include/linux/unwind_deferred.h b/include/linux/unwind_deferred.h
index 515d2995672d..14efd8c027aa 100644
--- a/include/linux/unwind_deferred.h
+++ b/include/linux/unwind_deferred.h
@@ -28,8 +28,8 @@ void unwind_deferred_cancel(struct unwind_work *work);
static __always_inline void unwind_reset_info(void)
{
- if (unlikely(current->unwind_info.id))
- current->unwind_info.id = 0;
+ if (unlikely(current->unwind_info.id.id))
+ current->unwind_info.id.id = 0;
/*
* As unwind_user_faultable() can be called directly and
* depends on nr_entries being cleared on exit to user,
diff --git a/kernel/module/main.c b/kernel/module/main.c
index 413ac6ea3702..58d36f8cef0d 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -2639,7 +2639,7 @@ static int find_module_sections(struct module *mod, struct load_info *info)
sizeof(*mod->trace_bprintk_fmt_start),
&mod->num_trace_bprintk_fmt);
#endif
-#ifdef CONFIG_FTRACE_MCOUNT_RECORD
+#ifdef CONFIG_DYNAMIC_FTRACE
/* sechdrs[0].sh_size is always zero */
mod->ftrace_callsites = section_objs(info, FTRACE_CALLSITE_SECTION,
sizeof(*mod->ftrace_callsites),
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index a3f35c7d83b6..c2ce834313a9 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -74,11 +74,6 @@ config HAVE_DYNAMIC_FTRACE_NO_PATCHABLE
If the architecture generates __patchable_function_entries sections
but does not want them included in the ftrace locations.
-config HAVE_FTRACE_MCOUNT_RECORD
- bool
- help
- See Documentation/trace/ftrace-design.rst
-
config HAVE_SYSCALL_TRACEPOINTS
bool
help
@@ -803,27 +798,22 @@ config BPF_KPROBE_OVERRIDE
Allows BPF to override the execution of a probed function and
set a different return value. This is used for error injection.
-config FTRACE_MCOUNT_RECORD
- def_bool y
- depends on DYNAMIC_FTRACE
- depends on HAVE_FTRACE_MCOUNT_RECORD
-
config FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY
bool
- depends on FTRACE_MCOUNT_RECORD
+ depends on DYNAMIC_FTRACE
config FTRACE_MCOUNT_USE_CC
def_bool y
depends on $(cc-option,-mrecord-mcount)
depends on !FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY
- depends on FTRACE_MCOUNT_RECORD
+ depends on DYNAMIC_FTRACE
config FTRACE_MCOUNT_USE_OBJTOOL
def_bool y
depends on HAVE_OBJTOOL_MCOUNT
depends on !FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY
depends on !FTRACE_MCOUNT_USE_CC
- depends on FTRACE_MCOUNT_RECORD
+ depends on DYNAMIC_FTRACE
select OBJTOOL
config FTRACE_MCOUNT_USE_RECORDMCOUNT
@@ -831,7 +821,7 @@ config FTRACE_MCOUNT_USE_RECORDMCOUNT
depends on !FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY
depends on !FTRACE_MCOUNT_USE_CC
depends on !FTRACE_MCOUNT_USE_OBJTOOL
- depends on FTRACE_MCOUNT_RECORD
+ depends on DYNAMIC_FTRACE
config TRACING_MAP
bool
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 4203fad56b6c..00b76d450a89 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1042,10 +1042,6 @@ static struct ftrace_ops *removed_ops;
*/
static bool update_all_ops;
-#ifndef CONFIG_FTRACE_MCOUNT_RECORD
-# error Dynamic ftrace depends on MCOUNT_RECORD
-#endif
-
struct ftrace_func_probe {
struct ftrace_probe_ops *probe_ops;
struct ftrace_ops ops;
diff --git a/scripts/recordmcount.pl b/scripts/recordmcount.pl
index 0871b2e92584..861b56dda64e 100755
--- a/scripts/recordmcount.pl
+++ b/scripts/recordmcount.pl
@@ -359,7 +359,7 @@ if ($arch eq "x86_64") {
$mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_CKCORE_PCREL_JSR_IMM26BY2\\s+_mcount\$";
$alignment = 2;
} else {
- die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD";
+ die "Arch $arch is not supported with CONFIG_DYNAMIC_FTRACE";
}
my $text_found = 0;
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