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authorJosh Poimboeuf <jpoimboe@redhat.com>2017-02-25 07:31:02 +0300
committerIngo Molnar <mingo@kernel.org>2017-02-25 12:11:23 +0300
commit3d1e236022cc1426b0834565995ddee2ca231cee (patch)
tree224cba29138fcf172228a983d47f0113657e0e24 /include/linux/compiler-gcc.h
parentd1091c7fa3d52ebce4dd3f15d04155b3469b2f90 (diff)
downloadlinux-3d1e236022cc1426b0834565995ddee2ca231cee.tar.xz
objtool: Prevent GCC from merging annotate_unreachable()
0-day bot reported some new objtool warnings which were caused by the new annotate_unreachable() macro: fs/afs/flock.o: warning: objtool: afs_do_unlk()+0x0: duplicate frame pointer save fs/afs/flock.o: warning: objtool: afs_do_unlk()+0x0: frame pointer state mismatch fs/btrfs/delayed-inode.o: warning: objtool: btrfs_delete_delayed_dir_index()+0x0: duplicate frame pointer save fs/btrfs/delayed-inode.o: warning: objtool: btrfs_delete_delayed_dir_index()+0x0: frame pointer state mismatch fs/dlm/lock.o: warning: objtool: _grant_lock()+0x0: duplicate frame pointer save fs/dlm/lock.o: warning: objtool: _grant_lock()+0x0: frame pointer state mismatch fs/ocfs2/alloc.o: warning: objtool: ocfs2_mv_path()+0x0: duplicate frame pointer save fs/ocfs2/alloc.o: warning: objtool: ocfs2_mv_path()+0x0: frame pointer state mismatch It turns out that, for older versions of GCC, if a function has multiple BUG() incantations, GCC will sometimes merge the corresponding annotate_unreachable() inline asm statements into a single block. That has the undesirable effect of removing one of the entries in the __unreachable section, confusing objtool greatly. A workaround for this issue is to ensure that each instance of the inline asm statement uses a different label, so that GCC sees the statements are unique and leaves them alone. The inline asm ‘%=’ token could be used for that, but unfortunately older versions of GCC don't support it. So I implemented a poor man's version of it with the __LINE__ macro. Reported-by: kbuild test robot <fengguang.wu@intel.com> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Fixes: d1091c7fa3d5 ("objtool: Improve detection of BUG() and other dead ends") Link: http://lkml.kernel.org/r/0c14b00baf9f68d1b0221ddb6c88b925181c8be8.1487997036.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include/linux/compiler-gcc.h')
-rw-r--r--include/linux/compiler-gcc.h6
1 files changed, 3 insertions, 3 deletions
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 8ea159fc489d..de471346b365 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -197,10 +197,10 @@
#ifdef CONFIG_STACK_VALIDATION
#define annotate_unreachable() ({ \
- asm("1:\t\n" \
+ asm("%c0:\t\n" \
".pushsection __unreachable, \"a\"\t\n" \
- ".long 1b\t\n" \
- ".popsection\t\n"); \
+ ".long %c0b\t\n" \
+ ".popsection\t\n" : : "i" (__LINE__)); \
})
#else
#define annotate_unreachable()