[PATCH 5.5 21/30] arm64: alternative: fix build with clang integrated assembler

[Greg Kroah-Hartman]

From: Ilie Halip <ilie.halip@xxxxxxxxx>

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@xxxxxxxxxx>
Tested-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
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@xxxxxxxxx>
Signed-off-by: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 arch/arm64/include/asm/alternative.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- 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
 
 /*