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From:   Tor Vic <torvic9@mailbox.org>
Subject: [PATCH v2 1/1] x86/Makefile: make -stack-alignment conditional on LLD
 < 13.0.0
To:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Nathan Chancellor <nathan@kernel.org>,
        "ndesaulniers@google.com" <ndesaulniers@google.com>,
        "tglx@linutronix.de" <tglx@linutronix.de>,
        "mingo@redhat.com" <mingo@redhat.com>
Cc:     "clang-built-linux@googlegroups.com" 
        <clang-built-linux@googlegroups.com>,
        "x86@kernel.org" <x86@kernel.org>
Message-ID: <f2c018ee-5999-741e-58d4-e482d5246067@mailbox.org>
Date:   Thu, 10 Jun 2021 20:58:06 +0000
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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.

Changes from v1:
- based on mainline
- provide more information about the flags (Nick)
- use correct tags

Cc: stable@vger.kernel.org
Link: https://github.com/ClangBuiltLinux/linux/issues/1377
[1]: https://reviews.llvm.org/D103048
[2]: https://reviews.llvm.org/D52322
Signed-off-by: Tor Vic <torvic9@mailbox.org>
---
 arch/x86/Makefile | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 307529417021..cb5e8d39cac1 100644
--- 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
-- 
2.32.0