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arm64: fix alternatives with LLVM's integrated assembler

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[ Upstream commit c54f90c2627cc316d365e3073614731e17dbc631 ]

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.

Link: https://github.com/ClangBuiltLinux/linux/issues/472
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Sami Tolvanen 2019-10-31 12:46:52 -07:00 committed by Greg Kroah-Hartman
parent 4b57abe52d
commit 3d0850ae2e
1 changed files with 21 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

32
arch/arm64/include/asm/alternative.h
View File

@ -29,13 +29,16 @@ typedef void (*alternative_cb_t)(struct alt_instr *alt,
void __init apply_alternatives_all(void);
void apply_alternatives(void *start, size_t length);
#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 */
@ -56,15 +59,14 @@ void apply_alternatives(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" \
@ -72,17 +74,25 @@ void apply_alternatives(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>