kernel/arch/arm64/include/asm/alternative.h

   1 #ifndef __ASM_ALTERNATIVE_H
   2 #define __ASM_ALTERNATIVE_H
   3
   4 #include <linux/types.h>
   5 #include <linux/stddef.h>
   6 #include <linux/stringify.h>
   7
   8 struct alt_instr {
   9         s32 orig_offset;        /* offset to original instruction */
  10         s32 alt_offset;         /* offset to replacement instruction */
  11         u16 cpufeature;         /* cpufeature bit set for replacement */
  12         u8  orig_len;           /* size of original instruction(s) */
  13         u8  alt_len;            /* size of new instruction(s), <= orig_len */
  14 };
  15
  16 void apply_alternatives_all(void);
  17 void apply_alternatives(void *start, size_t length);
  18 void free_alternatives_memory(void);
  19
  20 #define ALTINSTR_ENTRY(feature)                                               \
  21         " .word 661b - .\n"                             /* label           */ \
  22         " .word 663f - .\n"                             /* new instruction */ \
  23         " .hword " __stringify(feature) "\n"            /* feature bit     */ \
  24         " .byte 662b-661b\n"                            /* source len      */ \
  25         " .byte 664f-663f\n"                            /* replacement len */
  26
  27 /* alternative assembly primitive: */
  28 #define ALTERNATIVE(oldinstr, newinstr, feature)                        \
  29         "661:\n\t"                                                      \
  30         oldinstr "\n"                                                   \
  31         "662:\n"                                                        \
  32         ".pushsection .altinstructions,\"a\"\n"                         \
  33         ALTINSTR_ENTRY(feature)                                         \
  34         ".popsection\n"                                                 \
  35         ".pushsection .altinstr_replacement, \"a\"\n"                   \
  36         "663:\n\t"                                                      \
  37         newinstr "\n"                                                   \
  38         "664:\n\t"                                                      \
  39         ".popsection\n\t"                                               \
  40         ".if ((664b-663b) != (662b-661b))\n\t"                          \
  41         "       .error \"Alternatives instruction length mismatch\"\n\t"\
  42         ".endif\n"
  43
  44 #endif /* __ASM_ALTERNATIVE_H */