| From 85c615eb52222bc5fab6c7190d146bc59fac289e Mon Sep 17 00:00:00 2001 |
| From: Arnd Bergmann <arnd@arndb.de> |
| Date: Tue, 20 Feb 2018 21:58:21 +0100 |
| Subject: x86/oprofile: Fix bogus GCC-8 warning in nmi_setup() |
| |
| From: Arnd Bergmann <arnd@arndb.de> |
| |
| 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> |
| |
| --- |
| arch/x86/oprofile/nmi_int.c | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| --- a/arch/x86/oprofile/nmi_int.c |
| +++ b/arch/x86/oprofile/nmi_int.c |
| @@ -472,7 +472,7 @@ static int nmi_setup(void) |
| goto fail; |
| |
| for_each_possible_cpu(cpu) { |
| - if (!cpu) |
| + if (!IS_ENABLED(CONFIG_SMP) || !cpu) |
| continue; |
| |
| memcpy(per_cpu(cpu_msrs, cpu).counters, |