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authorArnd Bergmann <arnd@arndb.de>2018-02-20 21:58:21 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-02-28 10:19:41 +0100
commit7a14562d6e2c48068616e260a7d76b2ae8b8ee30 (patch)
parent0b82d316fa5b199125a22559fd457cf3100c34fc (diff)
x86/oprofile: Fix bogus GCC-8 warning in nmi_setup()
commit 85c615eb52222bc5fab6c7190d146bc59fac289e upstream. GCC-8 shows a warning for the x86 oprofile code that copies per-CPU data from CPU 0 to all other CPUs, which when building a non-SMP kernel turns into a memcpy() with identical source and destination pointers: arch/x86/oprofile/nmi_int.c: In function 'mux_clone': arch/x86/oprofile/nmi_int.c:285:2: error: 'memcpy' source argument is the same as destination [-Werror=restrict] memcpy(per_cpu(cpu_msrs, cpu).multiplex, ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ per_cpu(cpu_msrs, 0).multiplex, ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ sizeof(struct op_msr) * model->num_virt_counters); ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ arch/x86/oprofile/nmi_int.c: In function 'nmi_setup': arch/x86/oprofile/nmi_int.c:466:3: error: 'memcpy' source argument is the same as destination [-Werror=restrict] arch/x86/oprofile/nmi_int.c:470:3: error: 'memcpy' source argument is the same as destination [-Werror=restrict] I have analyzed a number of such warnings now: some are valid and the GCC warning is welcome. Others turned out to be false-positives, and GCC was changed to not warn about those any more. This is a corner case that is a false-positive but the GCC developers feel it's better to keep warning about it. In this case, it seems best to work around it by telling GCC a little more clearly that this code path is never hit with an IS_ENABLED() configuration check. Cc:stable as we also want old kernels to build cleanly with GCC-8. Signed-off-by: Arnd Bergmann <arnd@arndb.de> Cc: Jessica Yu <jeyu@kernel.org> Cc: Kees Cook <keescook@chromium.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Martin Sebor <msebor@gcc.gnu.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Robert Richter <rric@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: oprofile-list@lists.sf.net Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/20180220205826.2008875-1-arnd@arndb.de Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84095 Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/oprofile/nmi_int.c b/arch/x86/oprofile/nmi_int.c
index ffdbc4836b4f..abff76bda9e6 100644
--- a/arch/x86/oprofile/nmi_int.c
+++ b/arch/x86/oprofile/nmi_int.c
@@ -460,7 +460,7 @@ static int nmi_setup(void)
goto fail;
for_each_possible_cpu(cpu) {
- if (!cpu)
+ if (!IS_ENABLED(CONFIG_SMP) || !cpu)
memcpy(per_cpu(cpu_msrs, cpu).counters,