From: Nathan Chancellor natechancellor@gmail.com
[ Upstream commit aa69fb62bea15126e744af2e02acc0d6cf3ed4da ]
After r363059 and r363928 in LLVM, a build using ld.lld as the linker with CONFIG_RANDOMIZE_BASE enabled fails like so:
ld.lld: error: relocation R_AARCH64_ABS32 cannot be used against symbol __efistub_stext_offset; recompile with -fPIC
Fangrui and Peter figured out that ld.lld is incorrectly considering __efistub_stext_offset as a relative symbol because of the order in which symbols are evaluated. _text is treated as an absolute symbol and stext is a relative symbol, making __efistub_stext_offset a relative symbol.
Adding ABSOLUTE will force ld.lld to evalute this expression in the right context and does not change ld.bfd's behavior. ld.lld will need to be fixed but the developers do not see a quick or simple fix without some research (see the linked issue for further explanation). Add this simple workaround so that ld.lld can continue to link kernels.
Link: https://github.com/ClangBuiltLinux/linux/issues/561 Link: https://github.com/llvm/llvm-project/commit/025a815d75d2356f2944136269aa5874... Link: https://github.com/llvm/llvm-project/commit/249fde85832c33f8b06c6b4ac65d1c4b... Acked-by: Ard Biesheuvel ard.biesheuvel@linaro.org Debugged-by: Fangrui Song maskray@google.com Debugged-by: Peter Smith peter.smith@linaro.org Suggested-by: Fangrui Song maskray@google.com Signed-off-by: Nathan Chancellor natechancellor@gmail.com [will: add comment] Signed-off-by: Will Deacon will@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm64/kernel/image.h | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/kernel/image.h b/arch/arm64/kernel/image.h index 33f14e484040..b22e8ad071b1 100644 --- a/arch/arm64/kernel/image.h +++ b/arch/arm64/kernel/image.h @@ -78,7 +78,11 @@
#ifdef CONFIG_EFI
-__efistub_stext_offset = stext - _text; +/* + * Use ABSOLUTE() to avoid ld.lld treating this as a relative symbol: + * https://github.com/ClangBuiltLinux/linux/issues/561 + */ +__efistub_stext_offset = ABSOLUTE(stext - _text);
/* * The EFI stub has its own symbol namespace prefixed by __efistub_, to