Commit-ID: ec1e1b6109171d1890a437481c35b2b56d2327b8 Gitweb: https://git.kernel.org/tip/ec1e1b6109171d1890a437481c35b2b56d2327b8 Author: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> AuthorDate: Fri, 3 Nov 2017 17:19:41 -0500 Committer: Ingo Molnar <mingo@xxxxxxxxxx> 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@xxxxxxxxx> Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: kbuild-all@xxxxxx Cc: tipbuild@xxxxxxxxx Fixes: 3d1e236022cc ("objtool: Prevent GCC from merging annotate_unreachable()") Link: http://lkml.kernel.org/r/20171103221941.cajpwszir7ujxyc4@treble Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- 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" \ -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html