Merge tag 'char-misc-4.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh...

[cascardo/linux.git] / arch / arm64 / include / asm / alternative.h

diff --git a/arch/arm64/include/asm/alternative.h b/arch/arm64/include/asm/alternative.h
index 8746ff6..55101bd 100644 (file)
--- a/arch/arm64/include/asm/alternative.h
+++ b/arch/arm64/include/asm/alternative.h
@@ -2,6 +2,7 @@
 #define __ASM_ALTERNATIVE_H
 
 #include <asm/cpufeature.h>
+#include <asm/insn.h>
 
 #ifndef __ASSEMBLY__
 
@@ -90,34 +91,55 @@ void apply_alternatives(void *start, size_t length);
 .endm
 
 /*
- * Begin an alternative code sequence.
+ * Alternative sequences
+ *
+ * The code for the case where the capability is not present will be
+ * assembled and linked as normal. There are no restrictions on this
+ * code.
+ *
+ * The code for the case where the capability is present will be
+ * assembled into a special section to be used for dynamic patching.
+ * Code for that case must:
+ *
+ * 1. Be exactly the same length (in bytes) as the default code
+ *    sequence.
  *
- * The code that follows this macro will be assembled and linked as
- * normal. There are no restrictions on this code.
+ * 2. Not contain a branch target that is used outside of the
+ *    alternative sequence it is defined in (branches into an
+ *    alternative sequence are not fixed up).
+ */
+
+/*
+ * Begin an alternative code sequence.
  */
 .macro alternative_if_not cap
+       .set .Lasm_alt_mode, 0
        .pushsection .altinstructions, "a"
        altinstruction_entry 661f, 663f, \cap, 662f-661f, 664f-663f
        .popsection
 661:
 .endm
 
+.macro alternative_if cap
+       .set .Lasm_alt_mode, 1
+       .pushsection .altinstructions, "a"
+       altinstruction_entry 663f, 661f, \cap, 664f-663f, 662f-661f
+       .popsection
+       .pushsection .altinstr_replacement, "ax"
+       .align 2        /* So GAS knows label 661 is suitably aligned */
+661:
+.endm
+
 /*
- * Provide the alternative code sequence.
- *
- * The code that follows this macro is assembled into a special
- * section to be used for dynamic patching. Code that follows this
- * macro must:
- *
- * 1. Be exactly the same length (in bytes) as the default code
- *    sequence.
- *
- * 2. Not contain a branch target that is used outside of the
- *    alternative sequence it is defined in (branches into an
- *    alternative sequence are not fixed up).
+ * Provide the other half of the alternative code sequence.
  */
 .macro alternative_else
-662:   .pushsection .altinstr_replacement, "ax"
+662:
+       .if .Lasm_alt_mode==0
+       .pushsection .altinstr_replacement, "ax"
+       .else
+       .popsection
+       .endif
 663:
 .endm
 
@@ -125,11 +147,25 @@ void apply_alternatives(void *start, size_t length);
  * Complete an alternative code sequence.
  */
 .macro alternative_endif
-664:   .popsection
+664:
+       .if .Lasm_alt_mode==0
+       .popsection
+       .endif
        .org    . - (664b-663b) + (662b-661b)
        .org    . - (662b-661b) + (664b-663b)
 .endm
 
+/*
+ * Provides a trivial alternative or default sequence consisting solely
+ * of NOPs. The number of NOPs is chosen automatically to match the
+ * previous case.
+ */
+.macro alternative_else_nop_endif
+alternative_else
+       nops    (662b-661b) / AARCH64_INSN_SIZE
+alternative_endif
+.endm
+
 #define _ALTERNATIVE_CFG(insn1, insn2, cap, cfg, ...)  \
        alternative_insn insn1, insn2, cap, IS_ENABLED(cfg)