Commit-ID: ec1e1b6109171d1890a437481c35b2b56d2327b8
Gitweb: https://git.kernel.org/tip/ec1e1b6109171d1890a437481c35b2b56d2327b8
Author: Josh Poimboeuf <jpoim...@redhat.com>
AuthorDate: Fri, 3 Nov 2017 17:19:41 -0500
Committer: Ingo Molnar <mi...@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...@intel.com>
Signed-off-by: Josh Poimboeuf <jpoim...@redhat.com>
Cc: Andy Lutomirski <l...@kernel.org>
Cc: Borislav Petkov <b...@suse.de>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: kbuild-...@01.org
Cc: tipbu...@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 <mi...@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" \
