objtool: Fix gcov check for older versions of GCC
authorJosh Poimboeuf <jpoimboe@redhat.com>
Mon, 24 Jul 2017 23:34:14 +0000 (18:34 -0500)
committerIngo Molnar <mingo@kernel.org>
Tue, 25 Jul 2017 09:12:45 +0000 (11:12 +0200)
commit867ac9d737094e46a6c33213f16dd1ec9e8bd5d5
tree708c868a63e86271f0572ea7120a406bfe7e88a1
parent9683a64fc3cb67e663859a6bb2e0db5dcee9ed32
objtool: Fix gcov check for older versions of GCC

Objtool tries to silence 'unreachable instruction' warnings when it
detects gcov is enabled, because gcov produces a lot of unreachable
instructions and they don't really matter.

However, the 0-day bot is still reporting some unreachable instruction
warnings with CONFIG_GCOV_KERNEL=y on GCC 4.6.4.

As it turns out, objtool's gcov detection doesn't work with older
versions of GCC because they don't create a bunch of symbols with the
'gcov.' prefix like newer versions of GCC do.

Move the gcov check out of objtool and instead just create a new
'--no-unreachable' flag which can be passed in by the kernel Makefile
when CONFIG_GCOV_KERNEL is defined.

Also rename the 'nofp' variable to 'no_fp' for consistency with the new
'no_unreachable' variable.

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: 9cfffb116887 ("objtool: Skip all "unreachable instruction" warnings for gcov kernels")
Link: http://lkml.kernel.org/r/c243dc78eb2ffdabb6e927844dea39b6033cd395.1500939244.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
scripts/Makefile.build
tools/objtool/builtin-check.c
tools/objtool/builtin-orc.c
tools/objtool/check.c
tools/objtool/check.h