Greeting, FYI, we noticed the following commit (built with gcc-9): commit: 7ecfffe9bcb6657ae3a86c58f8eae2fe37b54807 ("selftests/lkdtm: Avoid needing explicit sub-shell") https://git.kernel.org/cgit/linux/kernel/git/kees/linux.git for-next/lkdtm in testcase: kernel-selftests version: kernel-selftests-x86_64-f8879e85-1_20210621 with following parameters: group: lkdtm ucode: 0xe2 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: 4 threads Intel(R) Core(TM) i5-6500 CPU @ 3.20GHz with 32G memory caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace): If you fix the issue, kindly add following tag Reported-by: kernel test robot <oliver.sang(a)intel.com&gt; [ 47.248291] kernel BUG at drivers/misc/lkdtm/bugs.c:76! [ 47.253682] invalid opcode: 0000 [#1] PREEMPT SMP PTI [ 47.258745] CPU: 0 PID: 1432 Comm: cat Not tainted 5.13.0-rc2-00001-g7ecfffe9bcb6 #1 [ 47.266509] Hardware name: Dell Inc. OptiPlex 7040/0Y7WYT, BIOS 1.8.1 12/05/2017 [ 47.273922] RIP: 0010:lkdtm_BUG (drivers/misc/lkdtm/bugs.c:76) [ 47.277856] Code: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc 0f 1f 44 00 00 <0f> 0b 66 66 2e 0f 1f 84 00 00 00 00 00 66 66 2e 0f 1f 84 00 00 00 All code ======== 0: cc int3 1: cc int3 2: cc int3 3: cc int3 4: cc int3 5: cc int3 6: cc int3 7: cc int3 8: cc int3 9: cc int3 a: cc int3 b: cc int3 c: cc int3 d: cc int3 e: cc int3 f: cc int3 10: cc int3 11: cc int3 12: cc int3 13: cc int3 14: cc int3 15: cc int3 16: cc int3 17: cc int3 18: cc int3 19: cc int3 1a: cc int3 1b: cc int3 1c: cc int3 1d: cc int3 1e: cc int3 1f: cc int3 20: cc int3 21: cc int3 22: cc int3 23: cc int3 24: cc int3 25: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1) 2a:* 0f 0b ud2 <-- trapping instruction 2c: 66 66 2e 0f 1f 84 00 data16 nopw %cs:0x0(%rax,%rax,1) 33: 00 00 00 00 37: 66 data16 38: 66 data16 39: 2e cs 3a: 0f .byte 0xf 3b: 1f (bad) 3c: 84 00 test %al,(%rax) ... Code starting with the faulting instruction =========================================== 0: 0f 0b ud2 2: 66 66 2e 0f 1f 84 00 data16 nopw %cs:0x0(%rax,%rax,1) 9: 00 00 00 00 d: 66 data16 e: 66 data16 f: 2e cs 10: 0f .byte 0xf 11: 1f (bad) 12: 84 00 test %al,(%rax) ... [ 47.296687] RSP: 0018:ffffc90001447e58 EFLAGS: 00010282 [ 47.301926] RAX: ffffffff81992280 RBX: 0000000000000001 RCX: 0000000000000000 [ 47.309079] RDX: 0000000000000000 RSI: ffffffff8122f88f RDI: ffffffff824c3f30 [ 47.316231] RBP: ffff888814b1a000 R08: 0000000000000001 R09: 0000000000000001 [ 47.323386] R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000004 [ 47.330540] R13: ffffc90001447f08 R14: ffffffff828b9198 R15: ffff888102666270 [ 47.337695] FS: 00007fb5044ea540(0000) GS:ffff88881dc00000(0000) knlGS:0000000000000000 [ 47.345806] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 47.351567] CR2: 00007fb504160000 CR3: 0000000814b30006 CR4: 00000000003706f0 [ 47.358719] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 47.365874] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 47.373028] Call Trace: [ 47.375480] direct_entry.cold (drivers/misc/lkdtm/core.c:397) [ 47.379417] full_proxy_write (fs/debugfs/file.c:234) [ 47.383262] vfs_write (fs/read_write.c:603) [ 47.386587] ksys_write (fs/read_write.c:658) [ 47.389996] do_syscall_64 (arch/x86/entry/common.c:47) [ 47.393582] entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:112) [ 47.398652] RIP: 0033:0x7fb504412504 [ 47.402241] Code: 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b3 0f 1f 80 00 00 00 00 48 8d 05 f9 61 0d 00 8b 00 85 c0 75 13 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 54 c3 0f 1f 00 41 54 49 89 d4 55 48 89 f5 53 All code ======== 0: 00 f7 add %dh,%bh 2: d8 64 89 02 fsubs 0x2(%rcx,%rcx,4) 6: 48 c7 c0 ff ff ff ff mov $0xffffffffffffffff,%rax d: eb b3 jmp 0xffffffffffffffc2 f: 0f 1f 80 00 00 00 00 nopl 0x0(%rax) 16: 48 8d 05 f9 61 0d 00 lea 0xd61f9(%rip),%rax # 0xd6216 1d: 8b 00 mov (%rax),%eax 1f: 85 c0 test %eax,%eax 21: 75 13 jne 0x36 23: b8 01 00 00 00 mov $0x1,%eax 28: 0f 05 syscall 2a:* 48 3d 00 f0 ff ff cmp $0xfffffffffffff000,%rax <-- trapping instruction 30: 77 54 ja 0x86 32: c3 retq 33: 0f 1f 00 nopl (%rax) 36: 41 54 push %r12 38: 49 89 d4 mov %rdx,%r12 3b: 55 push %rbp 3c: 48 89 f5 mov %rsi,%rbp 3f: 53 push %rbx Code starting with the faulting instruction =========================================== 0: 48 3d 00 f0 ff ff cmp $0xfffffffffffff000,%rax 6: 77 54 ja 0x5c 8: c3 retq 9: 0f 1f 00 nopl (%rax) c: 41 54 push %r12 e: 49 89 d4 mov %rdx,%r12 11: 55 push %rbp 12: 48 89 f5 mov %rsi,%rbp 15: 53 push %rbx To reproduce: git clone https://github.com/intel/lkp-tests.git cd lkp-tests bin/lkp install job.yaml # job file is attached in this email bin/lkp split-job --compatible job.yaml # generate the yaml file for lkp run bin/lkp run generated-yaml-file --- 0DAY/LKP+ Test Infrastructure Open Source Technology Center https://lists.01.org/hyperkitty/list/lkp@lists.01.org Intel Corporation Thanks, Oliver Sang