diff options
| author | Josh Poimboeuf <[email protected]> | 2017-02-24 22:31:02 -0600 |
|---|---|---|
| committer | Ingo Molnar <[email protected]> | 2017-02-25 10:11:23 +0100 |
| commit | 3d1e236022cc1426b0834565995ddee2ca231cee (patch) | |
| tree | 224cba29138fcf172228a983d47f0113657e0e24 | |
| parent | d1091c7fa3d52ebce4dd3f15d04155b3469b2f90 (diff) | |
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 <[email protected]>
Signed-off-by: Josh Poimboeuf <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
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 <[email protected]>
| -rw-r--r-- | include/linux/compiler-gcc.h | 6 |
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() |