[PATCH -next] arm64: alternatives: Use vdso/bits.h instead of linux/bits.h

From: Nathan Chancellor
Date: Mon Oct 03 2022 - 15:38:21 EST

When building with CONFIG_LTO after commit ba00c2a04fa5 ("arm64: fix the
build with binutils 2.27"), the following build error occurs:

In file included from arch/arm64/kernel/module-plts.c:6:
In file included from include/linux/elf.h:6:
In file included from arch/arm64/include/asm/elf.h:8:
In file included from arch/arm64/include/asm/hwcap.h:9:
In file included from arch/arm64/include/asm/cpufeature.h:9:
In file included from arch/arm64/include/asm/alternative-macros.h:5:
In file included from include/linux/bits.h:22:
In file included from include/linux/build_bug.h:5:
In file included from include/linux/compiler.h:248:
In file included from arch/arm64/include/asm/rwonce.h:71:
include/asm-generic/rwonce.h:67:9: error: expected string literal in 'asm'
return __READ_ONCE(*(unsigned long *)addr);
arch/arm64/include/asm/rwonce.h:43:16: note: expanded from macro '__READ_ONCE'
asm volatile(__LOAD_RCPC(b, %w0, %1) \
arch/arm64/include/asm/rwonce.h:17:2: note: expanded from macro '__LOAD_RCPC'

Similar to the issue resolved by commit 0072dc1b53c3 ("arm64: avoid
BUILD_BUG_ON() in alternative-macros"), there is a circular include
dependency through <linux/bits.h> when CONFIG_LTO is enabled due to
<asm/rwonce.h> appearing in the include chain before the contents of
<asm/alternative-macros.h>, which results in ALTERNATIVE() not getting
expanded properly because it has not been defined yet.

Avoid this issue by including <vdso/bits.h>, which includes the
definition of the BIT() macro, instead of <linux/bits.h>, as BIT() is the
only macro from bits.h that is relevant to this header.

Fixes: ba00c2a04fa5 ("arm64: fix the build with binutils 2.27")
Link: https://github.com/ClangBuiltLinux/linux/issues/1728
Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx>
arch/arm64/include/asm/alternative-macros.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/alternative-macros.h b/arch/arm64/include/asm/alternative-macros.h
index b5ac0b85c9bb..3622e9f4fb44 100644
--- a/arch/arm64/include/asm/alternative-macros.h
+++ b/arch/arm64/include/asm/alternative-macros.h
@@ -2,8 +2,8 @@

-#include <linux/bits.h>
#include <linux/const.h>
+#include <vdso/bits.h>

#include <asm/cpucaps.h>
#include <asm/insn-def.h>

base-commit: ba00c2a04fa5431d204a4183062b30372c062aa7