linux-kernel - [PATCH] x86/Makefile: make -stack-alignment conditional on LLD

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Message-ID: <214134496.67043.1623317284090@office.mailbox.org>
Date:   Thu, 10 Jun 2021 11:28:04 +0200 (CEST)
From:   torvic9@...lbox.org
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "nathan@...nel.org" <nathan@...nel.org>,
        "ndesaulniers@...gle.com" <ndesaulniers@...gle.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>
Cc:     "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "clang-built-linux@...glegroups.com" 
        <clang-built-linux@...glegroups.com>,
        "x86@...nel.org" <x86@...nel.org>
Subject: [PATCH] x86/Makefile: make -stack-alignment conditional 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.

This is for linux-stable 5.12.
Another patch will be submitted for 5.13 shortly (unless there are objections).

Discussion: 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@...lbox.org>
---
 arch/x86/Makefile | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 1f2e5bf..2855a1a 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -192,8 +192,9 @@ 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