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objtool: Fix gcov check for older versions of GCC

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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: 9cfffb1168 ("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>
This commit is contained in:
Josh Poimboeuf
2017-07-24 18:34:14 -05:00
committed by Ingo Molnar
parent 9683a64fc3
commit 867ac9d737
5 changed files with 17 additions and 35 deletions
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2
tools/objtool/check.h
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@@ -61,7 +61,7 @@ struct objtool_file {
bool ignore_unreachables, c_file, hints;
};
int check(const char *objname, bool nofp, bool orc);
int check(const char *objname, bool no_fp, bool no_unreachable, bool orc);
struct instruction *find_insn(struct objtool_file *file,
struct section *sec, unsigned long offset);