Messages in this thread | | | Subject | Re: [linux-stable-rc:linux-5.10.y 6996/7120] arch/x86/kernel/ftrace_64.o: warning: objtool: ftrace_epilogue()+0x10: unreachable instruction | From | Ben Hutchings <> | Date | Thu, 14 Jul 2022 01:41:58 +0200 |
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On Wed, 2022-07-13 at 03:57 +0800, kernel test robot wrote: > tree: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git linux-5.10.y > head: ba398a0e54049bb6a1c102245ae84103f103ff2c > commit: 8ca9dceaa17983afec1cc8e1a6e76d6bd142447a [6996/7120] objtool: Assume only ELF functions do sibling calls > config: x86_64-rhel-8.3-syz (https://download.01.org/0day-ci/archive/20220713/202207130344.dwXyDmTk-lkp@intel.com/config) > 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/stable/linux-stable-rc.git/commit/?id=8ca9dceaa17983afec1cc8e1a6e76d6bd142447a > git remote add linux-stable-rc https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git > git fetch --no-tags linux-stable-rc linux-5.10.y > git checkout 8ca9dceaa17983afec1cc8e1a6e76d6bd142447a > # save the config file > mkdir build_dir && cp config build_dir/.config > make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash arch/x86/ > > If you fix the issue, kindly add following tag where applicable > Reported-by: kernel test robot <lkp@intel.com> > > All warnings (new ones prefixed by >>): > > > > arch/x86/kernel/ftrace_64.o: warning: objtool: ftrace_epilogue()+0x10: unreachable instruction > > > objdump-func vmlinux.o ftrace_epilogue: > 0000 000000000008ca70 <ftrace_epilogue>: > 0000 8ca70: e9 00 00 00 00 jmp 8ca75 <ftrace_epilogue+0x5> 8ca71: R_X86_64_PLT32 ftrace_stub-0x4 > 0005 8ca75: 66 66 2e 0f 1f 84 00 00 00 00 00 data16 cs nopw 0x0(%rax,%rax,1) >
I don't know what's going on here. There's a jump to a ret (now potentialy a rethunk), and nothing obviously unreachable. ftrace_epilogue got simplified by commit 0c0593b45c9b "x86/ftrace: Make function graph use ftrace directly" which maybe avoids the warning in the mainline.
Ben.
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