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Diffstat (limited to 'arch/arm64/include/asm/alternative.h')
-rw-r--r--arch/arm64/include/asm/alternative.h46
1 files changed, 42 insertions, 4 deletions
diff --git a/arch/arm64/include/asm/alternative.h b/arch/arm64/include/asm/alternative.h
index d261f01e2bae..c385a0c4057f 100644
--- a/arch/arm64/include/asm/alternative.h
+++ b/arch/arm64/include/asm/alternative.h
@@ -1,6 +1,8 @@
#ifndef __ASM_ALTERNATIVE_H
#define __ASM_ALTERNATIVE_H
+#ifndef __ASSEMBLY__
+
#include <linux/types.h>
#include <linux/stddef.h>
#include <linux/stringify.h>
@@ -24,7 +26,20 @@ void free_alternatives_memory(void);
" .byte 662b-661b\n" /* source len */ \
" .byte 664f-663f\n" /* replacement len */
-/* alternative assembly primitive: */
+/*
+ * alternative assembly primitive:
+ *
+ * If any of these .org directive fail, it means that insn1 and insn2
+ * don't have the same length. This used to be written as
+ *
+ * .if ((664b-663b) != (662b-661b))
+ * .error "Alternatives instruction length mismatch"
+ * .endif
+ *
+ * but most assemblers die if insn1 or insn2 have a .inst. This should
+ * be fixed in a binutils release posterior to 2.25.51.0.2 (anything
+ * containing commit 4e4d08cf7399b606 or c1baaddf8861).
+ */
#define ALTERNATIVE(oldinstr, newinstr, feature) \
"661:\n\t" \
oldinstr "\n" \
@@ -37,8 +52,31 @@ void free_alternatives_memory(void);
newinstr "\n" \
"664:\n\t" \
".popsection\n\t" \
- ".if ((664b-663b) != (662b-661b))\n\t" \
- " .error \"Alternatives instruction length mismatch\"\n\t"\
- ".endif\n"
+ ".org . - (664b-663b) + (662b-661b)\n\t" \
+ ".org . - (662b-661b) + (664b-663b)\n"
+
+#else
+
+.macro altinstruction_entry orig_offset alt_offset feature orig_len alt_len
+ .word \orig_offset - .
+ .word \alt_offset - .
+ .hword \feature
+ .byte \orig_len
+ .byte \alt_len
+.endm
+
+.macro alternative_insn insn1 insn2 cap
+661: \insn1
+662: .pushsection .altinstructions, "a"
+ altinstruction_entry 661b, 663f, \cap, 662b-661b, 664f-663f
+ .popsection
+ .pushsection .altinstr_replacement, "ax"
+663: \insn2
+664: .popsection
+ .org . - (664b-663b) + (662b-661b)
+ .org . - (662b-661b) + (664b-663b)
+.endm
+
+#endif /* __ASSEMBLY__ */
#endif /* __ASM_ALTERNATIVE_H */