x86, lto: Pass -stack-alignment only on LLD < 13.0.0

Since LLVM commit 3787ee4, the '-stack-alignment' flag has been dropped
[1], leading to the following error message when building a LTO kernel
with Clang-13 and LLD-13:

    ld.lld: error: -plugin-opt=-: ld.lld: Unknown command line argument
    '-stack-alignment=8'.  Try 'ld.lld --help'
    ld.lld: Did you mean '--stackrealign=8'?

It also appears that the '-code-model' flag is not necessary anymore
starting with LLVM-9 [2].

Drop '-code-model' and make '-stack-alignment' conditional on LLD < 13.0.0.

These flags were necessary because these flags were not encoded in the
IR properly, so the link would restart optimizations without them. Now
there are properly encoded in the IR, and these flags exposing
implementation details are no longer necessary.

[1] https://reviews.llvm.org/D103048
[2] https://reviews.llvm.org/D52322

Cc: [email protected]
Link: https://github.com/ClangBuiltLinux/linux/issues/1377
Signed-off-by: Tor Vic <[email protected]>
Reviewed-by: Nathan Chancellor <[email protected]>
Tested-by: Nathan Chancellor <[email protected]>
Signed-off-by: Kees Cook <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 307529417021a77bcb5d7f80d774967edf7f1b2c..cb5e8d39cac156421b32fbd37e8a7c437e0c8e26 100644 (file)
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -200,8 +200,9 @@ endif
 KBUILD_LDFLAGS += -m elf_$(UTS_MACHINE)
 
 ifdef CONFIG_LTO_CLANG
-KBUILD_LDFLAGS += -plugin-opt=-code-model=kernel \
-                  -plugin-opt=-stack-alignment=$(if $(CONFIG_X86_32),4,8)
+ifeq ($(shell test $(CONFIG_LLD_VERSION) -lt 130000; echo $$?),0)
+KBUILD_LDFLAGS += -plugin-opt=-stack-alignment=$(if $(CONFIG_X86_32),4,8)
+endif
 endif
 
 ifdef CONFIG_X86_NEED_RELOCS