Messages in this thread Patch in this message | | | Date | Sat, 4 Nov 2017 15:31:28 -0700 | From | tip-bot for Josh Poimboeuf <> | Subject | [tip:core/urgent] objtool: Prevent GCC from merging annotate_unreachable(), take 2 |
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Commit-ID: ec1e1b6109171d1890a437481c35b2b56d2327b8 Gitweb: https://git.kernel.org/tip/ec1e1b6109171d1890a437481c35b2b56d2327b8 Author: Josh Poimboeuf <jpoimboe@redhat.com> AuthorDate: Fri, 3 Nov 2017 17:19:41 -0500 Committer: Ingo Molnar <mingo@kernel.org> CommitDate: Sat, 4 Nov 2017 15:03:39 +0100
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> --- include/linux/compiler.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/include/linux/compiler.h b/include/linux/compiler.h index fd8697a..2027104 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" \
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