tree: https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git lkdtm/undefined-instruction head: c00c18c5cd880f0d015d997a92675d30a5706714 commit: c00c18c5cd880f0d015d997a92675d30a5706714 [3/3] x86: implement undefined_instruction() config: x86_64-rhel-8.3-kselftests compiler: gcc-11 (Debian 11.3.0-3) 11.3.0 reproduce (this is a W=1 build): # https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/commit/?id=c00c18c5cd880f0d015d997a92675d30a5706714 git remote add mark https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git git fetch --no-tags mark lkdtm/undefined-instruction git checkout c00c18c5cd880f0d015d997a92675d30a5706714 # save the config file mkdir build_dir && cp config build_dir/.config make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash drivers/misc/ If you fix the issue, kindly add following tag where applicable Reported-by: kernel test robot All warnings (new ones prefixed by >>): >> drivers/misc/lkdtm/bugs.o: warning: objtool: lkdtm_UNDEFINED_INSTRUCTION+0x7: unreachable instruction objdump-func vmlinux.o lkdtm_UNDEFINED_INSTRUCTION: 0000 0000000001813900 : 0000 1813900: e8 00 00 00 00 call 1813905 1813901: R_X86_64_PLT32 __fentry__-0x4 0005 1813905: 0f 0b ud2 0007 1813907: 48 c7 c7 00 00 00 00 mov $0x0,%rdi 181390a: R_X86_64_32S .rodata+0x35dcc0 000e 181390e: e9 00 00 00 00 jmp 1813913 181390f: R_X86_64_PLT32 _printk-0x4 0013 1813913: 66 66 2e 0f 1f 84 00 00 00 00 00 data16 cs nopw 0x0(%rax,%rax,1) 001e 181391e: 66 66 2e 0f 1f 84 00 00 00 00 00 data16 cs nopw 0x0(%rax,%rax,1) 0029 1813929: 66 66 2e 0f 1f 84 00 00 00 00 00 data16 cs nopw 0x0(%rax,%rax,1) 0034 1813934: 66 66 2e 0f 1f 84 00 00 00 00 00 data16 cs nopw 0x0(%rax,%rax,1) 003f 181393f: 90 nop -- 0-DAY CI Kernel Test Service https://01.org/lkp