linux-kernel - [PATCH 4.19 051/346] arm64: lse: Fix LSE atomics with LLVM

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Message-Id: <20201228124922.260235014@linuxfoundation.org>
Date:   Mon, 28 Dec 2020 13:46:10 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Amit Kachhap <Amit.Kachhap@....com>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: [PATCH 4.19 051/346] arm64: lse: Fix LSE atomics with LLVM

From: Vincenzo Frascino <vincenzo.frascino@....com>

commit dd1f6308b28edf0452dd5dc7877992903ec61e69 upstream.

Commit e0d5896bd356 ("arm64: lse: fix LSE atomics with LLVM's integrated
assembler") broke the build when clang is used in connjunction with the
binutils assembler ("-no-integrated-as"). This happens because
__LSE_PREAMBLE is defined as ".arch armv8-a+lse", which overrides the
version of the CPU architecture passed via the "-march" paramter to gas:

$ aarch64-none-linux-gnu-as -EL -I ./arch/arm64/include
                                -I ./arch/arm64/include/generated
                                -I ./include -I ./include
                                -I ./arch/arm64/include/uapi
                                -I ./arch/arm64/include/generated/uapi
                                -I ./include/uapi -I ./include/generated/uapi
                                -I ./init -I ./init
                                -march=armv8.3-a -o init/do_mounts.o
                                /tmp/do_mounts-d7992a.s
/tmp/do_mounts-d7992a.s: Assembler messages:
/tmp/do_mounts-d7992a.s:1959: Error: selected processor does not support `autiasp'
/tmp/do_mounts-d7992a.s:2021: Error: selected processor does not support `paciasp'
/tmp/do_mounts-d7992a.s:2157: Error: selected processor does not support `autiasp'
/tmp/do_mounts-d7992a.s:2175: Error: selected processor does not support `paciasp'
/tmp/do_mounts-d7992a.s:2494: Error: selected processor does not support `autiasp'

Fix the issue by replacing ".arch armv8-a+lse" with ".arch_extension lse".
Sami confirms that the clang integrated assembler does now support the
'.arch_extension' directive, so this change will be fine even for LTO
builds in future.

Fixes: e0d5896bd356cd ("arm64: lse: fix LSE atomics with LLVM's integrated assembler")
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will@...nel.org>
Reported-by: Amit Kachhap <Amit.Kachhap@....com>
Tested-by: Sami Tolvanen <samitolvanen@...gle.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@....com>
Signed-off-by: Will Deacon <will@...nel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/arm64/include/asm/lse.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/arm64/include/asm/lse.h
+++ b/arch/arm64/include/asm/lse.h
@@ -4,7 +4,7 @@
 
 #if defined(CONFIG_AS_LSE) && defined(CONFIG_ARM64_LSE_ATOMICS)
 
-#define __LSE_PREAMBLE	".arch armv8-a+lse\n"
+#define __LSE_PREAMBLE	".arch_extension lse\n"
 
 #include <linux/compiler_types.h>
 #include <linux/export.h>