arch/x86/include/asm/alternative-asm.h

   1 #ifndef _ASM_X86_ALTERNATIVE_ASM_H
   2 #define _ASM_X86_ALTERNATIVE_ASM_H
   3
   4 #ifdef __ASSEMBLY__
   5
   6 #include <asm/asm.h>
   7
   8 #ifdef CONFIG_SMP
   9         .macro LOCK_PREFIX
  10 672:    lock
  11         .pushsection .smp_locks,"a"
  12         .balign 4
  13         .long 672b - .
  14         .popsection
  15         .endm
  16 #else
  17         .macro LOCK_PREFIX
  18         .endm
  19 #endif
  20
  21 /*
  22  * Issue one struct alt_instr descriptor entry (need to put it into
  23  * the section .altinstructions, see below). This entry contains
  24  * enough information for the alternatives patching code to patch an
  25  * instruction. See apply_alternatives().
  26  */
  27 .macro altinstruction_entry orig alt feature orig_len alt_len pad_len
  28         .long \orig - .
  29         .long \alt - .
  30         .word \feature
  31         .byte \orig_len
  32         .byte \alt_len
  33         .byte \pad_len
  34 .endm
  35
  36 /*
  37  * Define an alternative between two instructions. If @feature is
  38  * present, early code in apply_alternatives() replaces @oldinstr with
  39  * @newinstr. ".skip" directive takes care of proper instruction padding
  40  * in case @newinstr is longer than @oldinstr.
  41  */
  42 .macro ALTERNATIVE oldinstr, newinstr, feature
  43 140:
  44         \oldinstr
  45 141:
  46         .skip -(((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)),0x90
  47 142:
  48
  49         .pushsection .altinstructions,"a"
  50         altinstruction_entry 140b,143f,\feature,142b-140b,144f-143f,142b-141b
  51         .popsection
  52
  53         .pushsection .altinstr_replacement,"ax"
  54 143:
  55         \newinstr
  56 144:
  57         .popsection
  58 .endm
  59
  60 #define old_len                 141b-140b
  61 #define new_len1                144f-143f
  62 #define new_len2                145f-144f
  63
  64 /*
  65  * gas compatible max based on the idea from:
  66  * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
  67  *
  68  * The additional "-" is needed because gas uses a "true" value of -1.
  69  */
  70 #define alt_max_short(a, b)     ((a) ^ (((a) ^ (b)) & -(-((a) < (b)))))
  71
  72
  73 /*
  74  * Same as ALTERNATIVE macro above but for two alternatives. If CPU
  75  * has @feature1, it replaces @oldinstr with @newinstr1. If CPU has
  76  * @feature2, it replaces @oldinstr with @feature2.
  77  */
  78 .macro ALTERNATIVE_2 oldinstr, newinstr1, feature1, newinstr2, feature2
  79 140:
  80         \oldinstr
  81 141:
  82         .skip -((alt_max_short(new_len1, new_len2) - (old_len)) > 0) * \
  83                 (alt_max_short(new_len1, new_len2) - (old_len)),0x90
  84 142:
  85
  86         .pushsection .altinstructions,"a"
  87         altinstruction_entry 140b,143f,\feature1,142b-140b,144f-143f,142b-141b
  88         altinstruction_entry 140b,144f,\feature2,142b-140b,145f-144f,142b-141b
  89         .popsection
  90
  91         .pushsection .altinstr_replacement,"ax"
  92 143:
  93         \newinstr1
  94 144:
  95         \newinstr2
  96 145:
  97         .popsection
  98 .endm
  99
 100 #endif  /*  __ASSEMBLY__  */
 101
 102 #endif /* _ASM_X86_ALTERNATIVE_ASM_H */