FYI, we noticed the following commit (built with gcc-8):

commit: e483b0208784146864a2c195e316230647e9d297 ("proc: test /proc/*/maps, smaps, smaps_rollup, statm")
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master

in testcase: kernel_selftests
with following parameters:

	group: kselftests-02

test-description: The kernel contains a set of "self tests" under the tools/testing/selftests/ directory. These are intended to be small unit tests to exercise individual code paths in the kernel.
test-url: https://www.kernel.org/doc/Documentation/kselftest.txt


on test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 4G

caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):




KERNEL SELFTESTS: linux_headers_dir is /usr/src/linux-headers-x86_64-rhel-7.6-e483b0208784146864a2c195e316230647e9d297
2019-03-08 13:51:08 ln -sf /usr/bin/clang-7 /usr/bin/clang
2019-03-08 13:51:08 ln -sf /usr/bin/llc-7 /usr/bin/llc

2019-03-08 13:56:30 make run_tests -C proc
make: Entering directory '/usr/src/perf_selftests-x86_64-rhel-7.6-e483b0208784146864a2c195e316230647e9d297/tools/testing/selftests/proc'
gcc -Wall -O2 -Wno-unused-function -D_GNU_SOURCE    fd-001-lookup.c  -o /usr/src/perf_selftests-x86_64-rhel-7.6-e483b0208784146864a2c195e316230647e9d297/tools/testing/selftests/proc/fd-001-lookup
gcc -Wall -O2 -Wno-unused-function -D_GNU_SOURCE    fd-002-posix-eq.c  -o /usr/src/perf_selftests-x86_64-rhel-7.6-e483b0208784146864a2c195e316230647e9d297/tools/testing/selftests/proc/fd-002-posix-eq
gcc -Wall -O2 -Wno-unused-function -D_GNU_SOURCE    fd-003-kthread.c  -o /usr/src/perf_selftests-x86_64-rhel-7.6-e483b0208784146864a2c195e316230647e9d297/tools/testing/selftests/proc/fd-003-kthread
gcc -Wall -O2 -Wno-unused-function -D_GNU_SOURCE    proc-loadavg-001.c  -o /usr/src/perf_selftests-x86_64-rhel-7.6-e483b0208784146864a2c195e316230647e9d297/tools/testing/selftests/proc/proc-loadavg-001
proc-loadavg-001.c:17:0: warning: "_GNU_SOURCE" redefined
 #define _GNU_SOURCE
 
<command-line>:0:0: note: this is the location of the previous definition
gcc -Wall -O2 -Wno-unused-function -D_GNU_SOURCE    proc-pid-vm.c  -o /usr/src/perf_selftests-x86_64-rhel-7.6-e483b0208784146864a2c195e316230647e9d297/tools/testing/selftests/proc/proc-pid-vm
gcc -Wall -O2 -Wno-unused-function -D_GNU_SOURCE    proc-self-map-files-001.c  -o /usr/src/perf_selftests-x86_64-rhel-7.6-e483b0208784146864a2c195e316230647e9d297/tools/testing/selftests/proc/proc-self-map-files-001
gcc -Wall -O2 -Wno-unused-function -D_GNU_SOURCE    proc-self-map-files-002.c  -o /usr/src/perf_selftests-x86_64-rhel-7.6-e483b0208784146864a2c195e316230647e9d297/tools/testing/selftests/proc/proc-self-map-files-002
gcc -Wall -O2 -Wno-unused-function -D_GNU_SOURCE    proc-self-syscall.c  -o /usr/src/perf_selftests-x86_64-rhel-7.6-e483b0208784146864a2c195e316230647e9d297/tools/testing/selftests/proc/proc-self-syscall
proc-self-syscall.c:16:0: warning: "_GNU_SOURCE" redefined
 #define _GNU_SOURCE
 
<command-line>:0:0: note: this is the location of the previous definition
gcc -Wall -O2 -Wno-unused-function -D_GNU_SOURCE    proc-self-wchan.c  -o /usr/src/perf_selftests-x86_64-rhel-7.6-e483b0208784146864a2c195e316230647e9d297/tools/testing/selftests/proc/proc-self-wchan
gcc -Wall -O2 -Wno-unused-function -D_GNU_SOURCE    proc-uptime-001.c  -o /usr/src/perf_selftests-x86_64-rhel-7.6-e483b0208784146864a2c195e316230647e9d297/tools/testing/selftests/proc/proc-uptime-001
gcc -Wall -O2 -Wno-unused-function -D_GNU_SOURCE    proc-uptime-002.c  -o /usr/src/perf_selftests-x86_64-rhel-7.6-e483b0208784146864a2c195e316230647e9d297/tools/testing/selftests/proc/proc-uptime-002
proc-uptime-002.c:18:0: warning: "_GNU_SOURCE" redefined
 #define _GNU_SOURCE
 
<command-line>:0:0: note: this is the location of the previous definition
gcc -Wall -O2 -Wno-unused-function -D_GNU_SOURCE    read.c  -o /usr/src/perf_selftests-x86_64-rhel-7.6-e483b0208784146864a2c195e316230647e9d297/tools/testing/selftests/proc/read
gcc -Wall -O2 -Wno-unused-function -D_GNU_SOURCE    self.c  -o /usr/src/perf_selftests-x86_64-rhel-7.6-e483b0208784146864a2c195e316230647e9d297/tools/testing/selftests/proc/self
gcc -Wall -O2 -Wno-unused-function -D_GNU_SOURCE    setns-dcache.c  -o /usr/src/perf_selftests-x86_64-rhel-7.6-e483b0208784146864a2c195e316230647e9d297/tools/testing/selftests/proc/setns-dcache
gcc -Wall -O2 -Wno-unused-function -D_GNU_SOURCE    thread-self.c  -o /usr/src/perf_selftests-x86_64-rhel-7.6-e483b0208784146864a2c195e316230647e9d297/tools/testing/selftests/proc/thread-self
TAP version 13
selftests: proc: fd-001-lookup
========================================
ok 1..1 selftests: proc: fd-001-lookup [PASS]
selftests: proc: fd-002-posix-eq
========================================
ok 1..2 selftests: proc: fd-002-posix-eq [PASS]
selftests: proc: fd-003-kthread
========================================
ok 1..3 selftests: proc: fd-003-kthread [PASS]
selftests: proc: proc-loadavg-001
========================================
ok 1..4 selftests: proc: proc-loadavg-001 [PASS]
selftests: proc: proc-pid-vm
========================================
proc-pid-vm: proc-pid-vm.c:277: main: Assertion `rv == strlen(buf0)' failed.
Aborted
not ok 1..5 selftests: proc: proc-pid-vm [FAIL]
selftests: proc: proc-self-map-files-001
========================================
ok 1..6 selftests: proc: proc-self-map-files-001 [PASS]
selftests: proc: proc-self-map-files-002
========================================
ok 1..7 selftests: proc: proc-self-map-files-002 [PASS]
selftests: proc: proc-self-syscall
========================================
ok 1..8 selftests: proc: proc-self-syscall [PASS]
selftests: proc: proc-self-wchan
========================================
ok 1..9 selftests: proc: proc-self-wchan [PASS]
selftests: proc: proc-uptime-001
========================================
ok 1..10 selftests: proc: proc-uptime-001 [PASS]
selftests: proc: proc-uptime-002
========================================
ok 1..11 selftests: proc: proc-uptime-002 [PASS]
selftests: proc: read
========================================
ok 1..12 selftests: proc: read [PASS]
selftests: proc: self
========================================
ok 1..13 selftests: proc: self [PASS]
selftests: proc: setns-dcache
========================================
ok 1..14 selftests: proc: setns-dcache [PASS]
selftests: proc: thread-self
========================================
ok 1..15 selftests: proc: thread-self [PASS]
make: Leaving directory '/usr/src/perf_selftests-x86_64-rhel-7.6-e483b0208784146864a2c195e316230647e9d297/tools/testing/selftests/proc'



To reproduce:

        # build kernel
	cd linux
	cp config-5.0.0-03428-ge483b02 .config
	make HOSTCC=gcc-8 CC=gcc-8 ARCH=x86_64 olddefconfig
	make HOSTCC=gcc-8 CC=gcc-8 ARCH=x86_64 prepare
	make HOSTCC=gcc-8 CC=gcc-8 ARCH=x86_64 modules_prepare
	make HOSTCC=gcc-8 CC=gcc-8 ARCH=x86_64 SHELL=/bin/bash
	make HOSTCC=gcc-8 CC=gcc-8 ARCH=x86_64 bzImage


        git clone https://github.com/intel/lkp-tests.git
        cd lkp-tests
        bin/lkp qemu -k <bzImage> job-script # job-script is attached in this email



Thanks,
Rong Chen