arch/arm64/include/asm/alternative.h

   1 #ifndef __ASM_ALTERNATIVE_H
   2 #define __ASM_ALTERNATIVE_H
   3
   4 #ifndef __ASSEMBLY__
   5
   6 #include <linux/types.h>
   7 #include <linux/stddef.h>
   8 #include <linux/stringify.h>
   9
  10 struct alt_instr {
  11         s32 orig_offset;        /* offset to original instruction */
  12         s32 alt_offset;         /* offset to replacement instruction */
  13         u16 cpufeature;         /* cpufeature bit set for replacement */
  14         u8  orig_len;           /* size of original instruction(s) */
  15         u8  alt_len;            /* size of new instruction(s), <= orig_len */
  16 };
  17
  18 void apply_alternatives_all(void);
  19 void apply_alternatives(void *start, size_t length);
  20 void free_alternatives_memory(void);
  21
  22 #define ALTINSTR_ENTRY(feature)                                               \
  23         " .word 661b - .\n"                             /* label           */ \
  24         " .word 663f - .\n"                             /* new instruction */ \
  25         " .hword " __stringify(feature) "\n"            /* feature bit     */ \
  26         " .byte 662b-661b\n"                            /* source len      */ \
  27         " .byte 664f-663f\n"                            /* replacement len */
  28
  29 /* alternative assembly primitive: */
  30 #define ALTERNATIVE(oldinstr, newinstr, feature)                        \
  31         "661:\n\t"                                                      \
  32         oldinstr "\n"                                                   \
  33         "662:\n"                                                        \
  34         ".pushsection .altinstructions,\"a\"\n"                         \
  35         ALTINSTR_ENTRY(feature)                                         \
  36         ".popsection\n"                                                 \
  37         ".pushsection .altinstr_replacement, \"a\"\n"                   \
  38         "663:\n\t"                                                      \
  39         newinstr "\n"                                                   \
  40         "664:\n\t"                                                      \
  41         ".popsection\n\t"                                               \
  42         ".if ((664b-663b) != (662b-661b))\n\t"                          \
  43         "       .error \"Alternatives instruction length mismatch\"\n\t"\
  44         ".endif\n"
  45
  46 #else
  47
  48 .macro altinstruction_entry orig_offset alt_offset feature orig_len alt_len
  49         .word \orig_offset - .
  50         .word \alt_offset - .
  51         .hword \feature
  52         .byte \orig_len
  53         .byte \alt_len
  54 .endm
  55
  56 .macro alternative_insn insn1 insn2 cap
  57 661:    \insn1
  58 662:    .pushsection .altinstructions, "a"
  59         altinstruction_entry 661b, 663f, \cap, 662b-661b, 664f-663f
  60         .popsection
  61         .pushsection .altinstr_replacement, "ax"
  62 663:    \insn2
  63 664:    .popsection
  64         .if ((664b-663b) != (662b-661b))
  65                 .error "Alternatives instruction length mismatch"
  66         .endif
  67 .endm
  68
  69 #endif  /*  __ASSEMBLY__  */
  70
  71 #endif /* __ASM_ALTERNATIVE_H */