Patch "x86/oprofile: Fix bogus GCC-8 warning in nmi_setup()" has been added to the 4.4-stable tree
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This is a note to let you know that I've just added the patch titled
x86/oprofile: Fix bogus GCC-8 warning in nmi_setup()
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-oprofile-fix-bogus-gcc-8-warning-in-nmi_setup.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.
Quoted 1 line
From
85c615eb52222bc5fab6c7190d146bc59fac289eMon Sep 17 00:00:00 2001
From: Arnd Bergmann <[email protected]>
Date: Tue, 20 Feb 2018 21:58:21 +0100
Subject: x86/oprofile: Fix bogus GCC-8 warning in nmi_setup()
From: Arnd Bergmann <[email protected]>
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.
--- arch/x86/oprofile/nmi_int.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
arch/x86/oprofile/nmi_int.c +1 -1
@@ -471,7 +471,7 @@ 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,
Patches currently in stable-queue which might be from [email protected] are
queue-4.4/x86-oprofile-fix-bogus-gcc-8-warning-in-nmi_setup.patch queue-4.4/cfg80211-fix-cfg80211_beacon_dup.patch