diff options
| author | Josh Poimboeuf <jpoimboe@kernel.org> | 2025-03-21 12:53:32 -0700 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2025-03-22 09:49:26 +0100 |
| commit | 2cbb20b008dba39893f0e296dc8ca312f40a9a0e (patch) | |
| tree | f079da8bb91aecf528cb081d899e70dbaffb4028 /lib | |
| parent | 73070466ed3b5e4620e03c159ee12a570b171d08 (diff) | |
tracing: Disable branch profiling in noinstr code
CONFIG_TRACE_BRANCH_PROFILING inserts a call to ftrace_likely_update()
for each use of likely() or unlikely(). That breaks noinstr rules if
the affected function is annotated as noinstr.
Disable branch profiling for files with noinstr functions. In addition
to some individual files, this also includes the entire arch/x86
subtree, as well as the kernel/entry, drivers/cpuidle, and drivers/idle
directories, all of which are noinstr-heavy.
Due to the nature of how sched binaries are built by combining multiple
.c files into one, branch profiling is disabled more broadly across the
sched code than would otherwise be needed.
This fixes many warnings like the following:
vmlinux.o: warning: objtool: do_syscall_64+0x40: call to ftrace_likely_update() leaves .noinstr.text section
vmlinux.o: warning: objtool: __rdgsbase_inactive+0x33: call to ftrace_likely_update() leaves .noinstr.text section
vmlinux.o: warning: objtool: handle_bug.isra.0+0x198: call to ftrace_likely_update() leaves .noinstr.text section
...
Reported-by: Ingo Molnar <mingo@kernel.org>
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/fb94fc9303d48a5ed370498f54500cc4c338eb6d.1742586676.git.jpoimboe@kernel.org
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/Makefile | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/lib/Makefile b/lib/Makefile index d5cfc7afbbb8..4f3d00a2fd65 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -5,6 +5,11 @@ ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE) +# Branch profiling isn't noinstr-safe +ifdef CONFIG_TRACE_BRANCH_PROFILING +CFLAGS_smp_processor_id.o += -DDISABLE_BRANCH_PROFILING +endif + # These files are disabled because they produce lots of non-interesting and/or # flaky coverage that is not a function of syscall inputs. For example, # rbtree can be global and individual rotations don't correlate with inputs. |