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LoongArch: Pass annotate-tablejump option if LTO is enabled

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When compiling with LLVM and CONFIG_LTO_CLANG is set, there exist many
objtool warnings "sibling call from callable instruction with modified
stack frame".

For this special case, the related object file shows that there is no
generated relocation section '.rela.discard.tablejump_annotate' for the
table jump instruction jirl, thus objtool can not know that what is the
actual destination address.

It needs to do something on the LLVM side to make sure that there is the
relocation section '.rela.discard.tablejump_annotate' if LTO is enabled,
but in order to maintain compatibility for the current LLVM compiler,
this can be done in the kernel Makefile for now. Ensure it is aware of
linker with LTO, '--loongarch-annotate-tablejump' needs to be passed via
'-mllvm' to ld.lld.

Note that it should also pass the compiler option -mannotate-tablejump
rather than only pass '-mllvm --loongarch-annotate-tablejump' to ld.lld
if LTO is enabled, otherwise there are no jump info for some table jump
instructions.

Fixes: e20ab7d454 ("LoongArch: Enable jump table for objtool")
Closes: https://lore.kernel.org/loongarch/20250731175655.GA1455142@ax162/
Reported-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Co-developed-by: WANG Rui <wangrui@loongson.cn>
Signed-off-by: WANG Rui <wangrui@loongson.cn>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
This commit is contained in:
Tiezhu Yang
2025-08-20 22:23:15 +08:00
committed by Huacai Chen
parent a47bc954cf
commit 5dfea6644d
1 changed files with 6 additions and 0 deletions
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6
arch/loongarch/Makefile
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@@ -102,7 +102,13 @@ KBUILD_CFLAGS += $(call cc-option,-mthin-add-sub) $(call cc-option,-Wa$(comma)
ifdef CONFIG_OBJTOOL
ifdef CONFIG_CC_HAS_ANNOTATE_TABLEJUMP
# The annotate-tablejump option can not be passed to LLVM backend when LTO is enabled.
# Ensure it is aware of linker with LTO, '--loongarch-annotate-tablejump' also needs to
# be passed via '-mllvm' to ld.lld.
KBUILD_CFLAGS += -mannotate-tablejump
ifdef CONFIG_LTO_CLANG
KBUILD_LDFLAGS += -mllvm --loongarch-annotate-tablejump
endif
else
KBUILD_CFLAGS += -fno-jump-tables # keep compatibility with older compilers
endif