Re: test_vsyscall.c:500:22: warning: '__builtin_memcmp_eq' specified bound 4096 exceeds source size 0

From: Naresh Kamboju
Date: Thu Jan 06 2022 - 04:50:15 EST


On Thu, 6 Jan 2022 at 15:02, Greg Kroah-Hartman
<gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On Thu, Jan 06, 2022 at 02:55:53PM +0530, Naresh Kamboju wrote:
> > While building selftests the following warnings were noticed for x86_64
> > architecture on Linux stable v5.15.13 kernel.
> >
> > metadata:
> > git repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
> > git commit: 734eb1fd2073f503f5c6b44f1c0d453ca6986b84
> > git describe: v5.15.13
> > toolchain": gcc-11
> > kernel-config: https://builds.tuxbuild.com/23HFo8abXIL6i4FFfSYiJlqAYMW/config
> >
> > x86_64-linux-gnu-gcc -m64 -o \
> > /home/tuxbuild/.cache/tuxmake/builds/current/kselftest/x86/test_vsyscall_64 \
> > -O2 -g -std=gnu99 -pthread -Wall -no-pie \
> > -DCAN_BUILD_64 test_vsyscall.c helpers.h -lrt -ldl
> >
> > test_vsyscall.c: In function 'test_process_vm_readv':
> > test_vsyscall.c:500:22: warning: '__builtin_memcmp_eq' specified bound
> > 4096 exceeds source size 0 [-Wstringop-overread]
> > 500 | if (!memcmp(buf, (const void
> > *)0xffffffffff600000, 4096)) {
> > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
> > Reported-by: Linux Kernel Functional Testing <lkft@xxxxxxxxxx>
> >
> > Build link:
> > https://builds.tuxbuild.com/23HFo8abXIL6i4FFfSYiJlqAYMW/
> >
> > # To install tuxmake on your system globally:
> > # sudo pip3 install -U tuxmake
> >
> > tuxmake --runtime podman --target-arch x86_64 --toolchain gcc-11 \
> > --kconfig https://builds.tuxbuild.com/23HFo8abXIL6i4FFfSYiJlqAYMW/config \
> > cpupower headers kernel kselftest kselftest-merge modules
>
> Is this a new regression from 5.15.0? Is it also present on Linus's tree?

This build warning is not present in Linus's tree.
Following patch to be backported to 5.15.x

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