arm64: alternative: fix build with clang integrated assembler

commit 6f5459da2b8736720afdbd67c4bd2d1edba7d0e3 upstream.

Building an arm64 defconfig with clang's integrated assembler, this error
occurs:
    <instantiation>:2:2: error: unrecognized instruction mnemonic
     _ASM_EXTABLE 9999b, 9f
     ^
    arch/arm64/mm/cache.S:50:1: note: while in macro instantiation
    user_alt 9f, "dc cvau, x4", "dc civac, x4", 0
    ^

While GNU as seems fine with case-sensitive macro instantiations, clang
doesn't, so use the actual macro name (_asm_extable) as in the rest of
the file.

Also checked that the generated assembly matches the GCC output.

Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Fixes: 290622efc76e ("arm64: fix "dc cvau" cache operation on errata-affected core")
Link: https://github.com/ClangBuiltLinux/linux/issues/924
Signed-off-by: Ilie Halip <ilie.halip@gmail.com>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/include/asm/alternative.h b/arch/arm64/include/asm/alternative.h
index 324e7d5ab37edca2f17334b9734bcffc5d813da8..5e5dc05d63a06473050a1a55c7b0763484d73ebb 100644 (file)
--- a/arch/arm64/include/asm/alternative.h
+++ b/arch/arm64/include/asm/alternative.h
@@ -221,7 +221,7 @@ alternative_endif
 
 .macro user_alt, label, oldinstr, newinstr, cond
 9999:  alternative_insn "\oldinstr", "\newinstr", \cond
-       _ASM_EXTABLE 9999b, \label
+       _asm_extable 9999b, \label
 .endm
 
 /*