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| author | Josh Poimboeuf <jpoimboe@redhat.com> | 2017-11-03 17:19:41 -0500 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-11-04 15:03:39 +0100 |
| commit | ec1e1b6109171d1890a437481c35b2b56d2327b8 (patch) | |
| tree | 80189a47f0bb8debeaee467436c92debf81468bf /include | |
| parent | da0db32bbe816085d7f7f9cebfc825e55eff811f (diff) | |
| download | lwn-ec1e1b6109171d1890a437481c35b2b56d2327b8.tar.gz lwn-ec1e1b6109171d1890a437481c35b2b56d2327b8.zip | |
objtool: Prevent GCC from merging annotate_unreachable(), take 2
This fixes the following warning with GCC 4.6:
mm/migrate.o: warning: objtool: migrate_misplaced_transhuge_page()+0x71: unreachable instruction
The problem is that the compiler merged identical annotate_unreachable()
inline asm blocks, resulting in a missing 'unreachable' annotation.
This problem happened before, and was partially fixed with:
3d1e236022cc ("objtool: Prevent GCC from merging annotate_unreachable()")
That commit tried to ensure that each instance of the
annotate_unreachable() inline asm statement has a unique label. It used
the __LINE__ macro to generate the label number. However, even the line
number isn't necessarily unique when used in an inline function with
multiple callers (in this case, __alloc_pages_node()'s use of
VM_BUG_ON).
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kbuild-all@01.org
Cc: tipbuild@zytor.com
Fixes: 3d1e236022cc ("objtool: Prevent GCC from merging annotate_unreachable()")
Link: http://lkml.kernel.org/r/20171103221941.cajpwszir7ujxyc4@treble
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/compiler.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/include/linux/compiler.h b/include/linux/compiler.h index fd8697aa4f73..202710420d6d 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -191,13 +191,13 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, asm("%c0:\n\t" \ ".pushsection .discard.reachable\n\t" \ ".long %c0b - .\n\t" \ - ".popsection\n\t" : : "i" (__LINE__)); \ + ".popsection\n\t" : : "i" (__COUNTER__)); \ }) #define annotate_unreachable() ({ \ asm("%c0:\n\t" \ ".pushsection .discard.unreachable\n\t" \ ".long %c0b - .\n\t" \ - ".popsection\n\t" : : "i" (__LINE__)); \ + ".popsection\n\t" : : "i" (__COUNTER__)); \ }) #define ASM_UNREACHABLE \ "999:\n\t" \ |