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authorJosh Poimboeuf <jpoimboe@redhat.com>2017-11-03 23:19:41 +0100
committerIngo Molnar <mingo@kernel.org>2017-11-04 15:03:39 +0100
commitec1e1b6109171d1890a437481c35b2b56d2327b8 (patch)
tree80189a47f0bb8debeaee467436c92debf81468bf /include/linux/compiler.h
parentobjtool: Resync objtool's instruction decoder source code copy with the kerne... (diff)
downloadlinux-ec1e1b6109171d1890a437481c35b2b56d2327b8.tar.xz
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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 '')
-rw-r--r--include/linux/compiler.h4
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" \