linux/tools/objtool
Josh Poimboeuf 9cfffb1168 objtool: Skip all "unreachable instruction" warnings for gcov kernels
Recently objtool has started reporting a few "unreachable instruction"
warnings when CONFIG_GCOV is enabled for newer versions of GCC.  Usually
this warning means there's some new control flow that objtool doesn't
understand.  But in this case, objtool is correct and the instructions
really are inaccessible.  It's an annoying quirk of gcov, but it's
harmless, so it's ok to just silence the warnings.

With older versions of GCC, it was relatively easy to detect
gcov-specific instructions and to skip any unreachable warnings produced
by them.  But GCC 6 has gotten craftier.

Instead of continuing to play whack-a-mole with gcov, just use a bigger,
more permanent hammer and disable unreachable warnings for the whole
file when gcov is enabled.  This is fine to do because a) unreachable
warnings are usually of questionable value; and b) gcov isn't used for
production kernels and we can relax the checks a bit there.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/38d5c87d61d9cd46486dd2c86f46603dff0df86f.1476393584.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-10-16 09:12:36 +02:00
..
arch/x86 objtool: Support '-mtune=atom' stack frame setup instruction 2016-10-11 10:35:45 +02:00
Documentation objtool: Detect falling through to the next function 2016-04-16 11:14:17 +02:00
.gitignore objtool: Add 'fixdep' to objtool/.gitignore 2016-07-27 11:07:11 +02:00
arch.h objtool: Add tool to perform compile-time stack metadata validation 2016-02-29 08:35:12 +01:00
Build tools build: Fix objtool build with ARCH=x86_64 2016-07-22 16:37:44 -03:00
builtin-check.c objtool: Skip all "unreachable instruction" warnings for gcov kernels 2016-10-16 09:12:36 +02:00
builtin.h objtool: Add tool to perform compile-time stack metadata validation 2016-02-29 08:35:12 +01:00
elf.c objtool: Add fallback from ELF_C_READ_MMAP to ELF_C_READ 2016-07-13 15:38:50 -03:00
elf.h objtool: Allow building with older libelf 2016-05-17 10:42:46 +02:00
Makefile objtool: Un-capitalize "Warning" for out-of-sync instruction decoder 2016-07-29 16:57:16 +02:00
objtool.c objtool: Add tool to perform compile-time stack metadata validation 2016-02-29 08:35:12 +01:00
special.c objtool: Add tool to perform compile-time stack metadata validation 2016-02-29 08:35:12 +01:00
special.h objtool: Add tool to perform compile-time stack metadata validation 2016-02-29 08:35:12 +01:00
warn.h objtool: Add tool to perform compile-time stack metadata validation 2016-02-29 08:35:12 +01:00