arm64: alternatives: Use vdso/bits.h instead of linux/bits.h

When building with CONFIG_LTO after commit ba00c2a ("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'
          ALTERNATIVE(                                                    \
          ^

Similar to the issue resolved by commit 0072dc1 ("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: ba00c2a ("arm64: fix the build with binutils 2.27")
Link: ClangBuiltLinux#1728
Signed-off-by: Nathan Chancellor <[email protected]>
Tested-by: Will Deacon <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Catalin Marinas <[email protected]>

Author: nathanchance

arch/arm64/include/asm/alternative-macros.h

@@ -2,8 +2,8 @@
 #ifndef __ASM_ALTERNATIVE_MACROS_H
 #define __ASM_ALTERNATIVE_MACROS_H
 
-#include <linux/bits.h>
 #include <linux/const.h>
+#include <vdso/bits.h>
 
 #include <asm/cpucaps.h>
 #include <asm/insn-def.h>