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 /*
  30  * alternative assembly primitive:
  31  *
  32  * If any of these .org directive fail, it means that insn1 and insn2
  33  * don't have the same length. This used to be written as
  34  *
  35  * .if ((664b-663b) != (662b-661b))
  36  *      .error "Alternatives instruction length mismatch"
  37  * .endif
  38  *
  39  * but most assemblers die if insn1 or insn2 have a .inst. This should
  40  * be fixed in a binutils release posterior to 2.25.51.0.2 (anything
  41  * containing commit 4e4d08cf7399b606 or c1baaddf8861).
  42  */
  43 #define ALTERNATIVE(oldinstr, newinstr, feature)                        \
  44         "661:\n\t"                                                      \
  45         oldinstr "\n"                                                   \
  46         "662:\n"                                                        \
  47         ".pushsection .altinstructions,\"a\"\n"                         \
  48         ALTINSTR_ENTRY(feature)                                         \
  49         ".popsection\n"                                                 \
  50         ".pushsection .altinstr_replacement, \"a\"\n"                   \
  51         "663:\n\t"                                                      \
  52         newinstr "\n"                                                   \
  53         "664:\n\t"                                                      \
  54         ".popsection\n\t"                                               \
  55         ".org   . - (664b-663b) + (662b-661b)\n\t"                      \
  56         ".org   . - (662b-661b) + (664b-663b)\n"
  57
  58 #else
  59
  60 .macro altinstruction_entry orig_offset alt_offset feature orig_len alt_len
  61         .word \orig_offset - .
  62         .word \alt_offset - .
  63         .hword \feature
  64         .byte \orig_len
  65         .byte \alt_len
  66 .endm
  67
  68 .macro alternative_insn insn1 insn2 cap
  69 661:    \insn1
  70 662:    .pushsection .altinstructions, "a"
  71         altinstruction_entry 661b, 663f, \cap, 662b-661b, 664f-663f
  72         .popsection
  73         .pushsection .altinstr_replacement, "ax"
  74 663:    \insn2
  75 664:    .popsection
  76         .org    . - (664b-663b) + (662b-661b)
  77         .org    . - (662b-661b) + (664b-663b)
  78 .endm
  79
  80 #endif  /*  __ASSEMBLY__  */
  81
  82 #endif /* __ASM_ALTERNATIVE_H */