Arnd found a randconfig that produces the warning: arch/x86/entry/thunk_64.o: warning: objtool: missing symbol for insn at offset 0x3e
when building with LLVM_IAS=1 (use Clang's integrated assembler). Josh notes: With the LLVM assembler stripping the .text section symbol, objtool has no way to reference this code when it generates ORC unwinder entries, because this code is outside of any ELF function. This behavior was implemented as an optimization in LLVM 5 years ago, but it's not the first time this has caused issues for objtool. A patch has been authored against LLVM to revert the behavior, which may or may not be accepted. Until then use a global symbol for the thunk that way objtool can generate proper unwind info here with LLVM_IAS=1. Cc: Fangrui Song <[email protected]> Reported-by: Arnd Bergmann <[email protected]> Suggested-by: Josh Poimboeuf <[email protected]> Link: https://github.com/ClangBuiltLinux/linux/issues/1209 Link: https://reviews.llvm.org/D93783 Signed-off-by: Nick Desaulniers <[email protected]> --- arch/x86/entry/thunk_64.S | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/arch/x86/entry/thunk_64.S b/arch/x86/entry/thunk_64.S index ccd32877a3c4..878816034a73 100644 --- a/arch/x86/entry/thunk_64.S +++ b/arch/x86/entry/thunk_64.S @@ -31,7 +31,7 @@ SYM_FUNC_START_NOALIGN(\name) .endif call \func - jmp .L_restore + jmp __thunk_restore SYM_FUNC_END(\name) _ASM_NOKPROBE(\name) .endm @@ -44,7 +44,7 @@ SYM_FUNC_END(\name) #endif #ifdef CONFIG_PREEMPTION -SYM_CODE_START_LOCAL_NOALIGN(.L_restore) +SYM_CODE_START_NOALIGN(__thunk_restore) popq %r11 popq %r10 popq %r9 @@ -56,6 +56,6 @@ SYM_CODE_START_LOCAL_NOALIGN(.L_restore) popq %rdi popq %rbp ret - _ASM_NOKPROBE(.L_restore) -SYM_CODE_END(.L_restore) + _ASM_NOKPROBE(__thunk_restore) +SYM_CODE_END(__thunk_restore) #endif -- 2.29.2.729.g45daf8777d-goog
