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LoongArch: Only allow OBJTOOL & ORC unwinder if toolchain supports -mthin-add-sub

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GAS <= 2.41 does not support generating R_LARCH_{32,64}_PCREL for
"label - ." and it generates R_LARCH_{ADD,SUB}{32,64} pairs instead.
Objtool cannot handle R_LARCH_{ADD,SUB}{32,64} pair in __jump_table
(static key implementation) and etc. so it will produce some warnings.
This is causing the kernel CI systems to complain everywhere.

For GAS we can check if -mthin-add-sub option is available to know if
R_LARCH_{32,64}_PCREL are supported.

For Clang, we require Clang >= 18 and Clang >= 17 already supports
R_LARCH_{32,64}_PCREL. But unfortunately Clang has some other issues,
so we disable objtool for Clang at present.

Note that __jump_table here is not generated by the compiler, so
-fno-jump-table is completely irrelevant for this issue.

Fixes: cb8a2ef084 ("LoongArch: Add ORC stack unwinder support")
Closes: https://lore.kernel.org/loongarch/Zl5m1ZlVmGKitAof@yujie-X299/
Closes: https://lore.kernel.org/loongarch/ZlY1gDDPi_mNrwJ1@slm.duckdns.org/
Closes: https://lore.kernel.org/loongarch/1717478006.038663-1-hengqi@linux.alibaba.com/
Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commitdiff;h=816029e06768
Link: https://github.com/llvm/llvm-project/commit/42cb3c6346fc
Signed-off-by: Xi Ruoyao <xry111@xry111.site>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
This commit is contained in:
Xi Ruoyao 2024-06-21 10:18:40 +08:00 committed by Huacai Chen
parent 6ba59ff422
commit 120dd4118e
2 changed files with 5 additions and 1 deletions
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5
arch/loongarch/Kconfig
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@ -143,7 +143,7 @@ config LOONGARCH
select HAVE_LIVEPATCH
select HAVE_MOD_ARCH_SPECIFIC
select HAVE_NMI
select HAVE_OBJTOOL if AS_HAS_EXPLICIT_RELOCS
select HAVE_OBJTOOL if AS_HAS_EXPLICIT_RELOCS && AS_HAS_THIN_ADD_SUB && !CC_IS_CLANG
select HAVE_PCI
select HAVE_PERF_EVENTS
select HAVE_PERF_REGS
@ -261,6 +261,9 @@ config AS_HAS_EXPLICIT_RELOCS
config AS_HAS_FCSR_CLASS
def_bool $(as-instr,movfcsr2gr \$t0$(comma)\$fcsr0)
config AS_HAS_THIN_ADD_SUB
def_bool $(cc-option,-Wa$(comma)-mthin-add-sub)
config AS_HAS_LSX_EXTENSION
def_bool $(as-instr,vld \$vr0$(comma)\$a0$(comma)0)

1
arch/loongarch/Kconfig.debug
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@ -28,6 +28,7 @@ config UNWINDER_PROLOGUE
config UNWINDER_ORC
bool "ORC unwinder"
depends on HAVE_OBJTOOL
select OBJTOOL
help
This option enables the ORC (Oops Rewind Capability) unwinder for