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Commit b39dbed4 authored by Sami Tolvanen's avatar Sami Tolvanen Committed by Alistair Delva
Browse files

FROMLIST: arm64: fix alternatives with LLVM's integrated assembler 

LLVM's integrated assembler fails with the following error when
building KVM:

  <inline asm>:12:6: error: expected absolute expression
   .if kvm_update_va_mask == 0
       ^
  <inline asm>:21:6: error: expected absolute expression
   .if kvm_update_va_mask == 0
       ^
  <inline asm>:24:2: error: unrecognized instruction mnemonic
          NOT_AN_INSTRUCTION
          ^
  LLVM ERROR: Error parsing inline asm

These errors come from ALTERNATIVE_CB and __ALTERNATIVE_CFG,
which test for the existence of the callback parameter in inline
assembly using the following expression:

  " .if " __stringify(cb) " == 0\n"

This works with GNU as, but isn't supported by LLVM. This change
splits __ALTERNATIVE_CFG and ALTINSTR_ENTRY into separate macros
to fix the LLVM build.

Bug: 145210207
Change-Id: I62dd786277bcaf3c730a7489c4b5a2b437f722ce
(am from https://lore.kernel.org/patchwork/patch/1136803/)
Link: https://github.com/ClangBuiltLinux/linux/issues/472


Signed-off-by: default avatarSami Tolvanen <samitolvanen@google.com>
parent 1092197c

arch/arm64/include/asm/alternative.h

+21 −11
Original line number Diff line number Diff line
@@ -35,13 +35,16 @@ void apply_alternatives_module(void *start, size_t length); 
static inline void apply_alternatives_module(void *start, size_t length) { }

#endif



#define ALTINSTR_ENTRY(feature,cb)					      \

#define ALTINSTR_ENTRY(feature)					              \

	" .word 661b - .\n"				/* label           */ \

	" .if " __stringify(cb) " == 0\n"				      \

	" .word 663f - .\n"				/* new instruction */ \

	" .else\n"							      \

	" .hword " __stringify(feature) "\n"		/* feature bit     */ \

	" .byte 662b-661b\n"				/* source len      */ \

	" .byte 664f-663f\n"				/* replacement len */



#define ALTINSTR_ENTRY_CB(feature,cb)					      \

	" .word 661b - .\n"				/* label           */ \

	" .word " __stringify(cb) "- .\n"		/* callback */	      \

	" .endif\n"							      \

	" .hword " __stringify(feature) "\n"		/* feature bit     */ \

	" .byte 662b-661b\n"				/* source len      */ \

	" .byte 664f-663f\n"				/* replacement len */
@@ -62,15 +65,14 @@ static inline void apply_alternatives_module(void *start, size_t length) { } 
 *

 * Alternatives with callbacks do not generate replacement instructions.

 */

#define __ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg_enabled, cb)	\

#define __ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg_enabled)	\

	".if "__stringify(cfg_enabled)" == 1\n"				\

	"661:\n\t"							\

	oldinstr "\n"							\

	"662:\n"							\

	".pushsection .altinstructions,\"a\"\n"				\

	ALTINSTR_ENTRY(feature,cb)					\

	ALTINSTR_ENTRY(feature)						\

	".popsection\n"							\

	" .if " __stringify(cb) " == 0\n"				\

	".pushsection .altinstr_replacement, \"a\"\n"			\

	"663:\n\t"							\

	newinstr "\n"							\
@@ -78,17 +80,25 @@ static inline void apply_alternatives_module(void *start, size_t length) { } 
	".popsection\n\t"						\

	".org	. - (664b-663b) + (662b-661b)\n\t"			\

	".org	. - (662b-661b) + (664b-663b)\n"			\

	".else\n\t"							\

	".endif\n"



#define __ALTERNATIVE_CFG_CB(oldinstr, feature, cfg_enabled, cb)	\

	".if "__stringify(cfg_enabled)" == 1\n"				\

	"661:\n\t"							\

	oldinstr "\n"							\

	"662:\n"							\

	".pushsection .altinstructions,\"a\"\n"				\

	ALTINSTR_ENTRY_CB(feature,cb)					\

	".popsection\n"							\

	"663:\n\t"							\

	"664:\n\t"							\

	".endif\n"							\

	".endif\n"



#define _ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg, ...)	\

	__ALTERNATIVE_CFG(oldinstr, newinstr, feature, IS_ENABLED(cfg), 0)

	__ALTERNATIVE_CFG(oldinstr, newinstr, feature, IS_ENABLED(cfg))



#define ALTERNATIVE_CB(oldinstr, cb) \

	__ALTERNATIVE_CFG(oldinstr, "NOT_AN_INSTRUCTION", ARM64_CB_PATCH, 1, cb)

	__ALTERNATIVE_CFG_CB(oldinstr, ARM64_CB_PATCH, 1, cb)

#else



#include <asm/assembler.h>