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

[ Upstream commit 120dd4118e58dbda2ddb1dcf55f3c56cdfe8cee0 ]

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: cb8a2ef0848c ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 54ad04dacdee94d869b2bd7d0ab92a92e60fe642..d1b94ce58f79358dfb6c32b044f5268c86a1c451 100644 (file)
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -138,7 +138,7 @@ 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
@@ -257,6 +257,9 @@ 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)
 

diff --git a/arch/loongarch/Kconfig.debug b/arch/loongarch/Kconfig.debug
index 98d60630c3d4b4771d7fe5570e15b7f5e0ab2071..8b2ce5b5d43e8f7df0af14019d2c8b28a7da1511 100644 (file)
--- a/arch/loongarch/Kconfig.debug
+++ b/arch/loongarch/Kconfig.debug
@@ -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