include/asm-i386/alternative.h

   1 #ifndef _I386_ALTERNATIVE_H
   2 #define _I386_ALTERNATIVE_H
   3
   4 #ifdef __KERNEL__
   5
   6 #include <asm/types.h>
   7
   8 struct alt_instr {
   9         u8 *instr;              /* original instruction */
  10         u8 *replacement;
  11         u8  cpuid;              /* cpuid bit set for replacement */
  12         u8  instrlen;           /* length of original instruction */
  13         u8  replacementlen;     /* length of new instruction, <= instrlen */
  14         u8  pad;
  15 };
  16
  17 extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
  18
  19 struct module;
  20 extern void alternatives_smp_module_add(struct module *mod, char *name,
  21                                         void *locks, void *locks_end,
  22                                         void *text, void *text_end);
  23 extern void alternatives_smp_module_del(struct module *mod);
  24 extern void alternatives_smp_switch(int smp);
  25
  26 #endif
  27
  28 /*
  29  * Alternative instructions for different CPU types or capabilities.
  30  *
  31  * This allows to use optimized instructions even on generic binary
  32  * kernels.
  33  *
  34  * length of oldinstr must be longer or equal the length of newinstr
  35  * It can be padded with nops as needed.
  36  *
  37  * For non barrier like inlines please define new variants
  38  * without volatile and memory clobber.
  39  */
  40 #define alternative(oldinstr, newinstr, feature)                        \
  41         asm volatile ("661:\n\t" oldinstr "\n662:\n"                    \
  42                       ".section .altinstructions,\"a\"\n"               \
  43                       "  .align 4\n"                                    \
  44                       "  .long 661b\n"            /* label */           \
  45                       "  .long 663f\n"            /* new instruction */ \
  46                       "  .byte %c0\n"             /* feature bit */     \
  47                       "  .byte 662b-661b\n"       /* sourcelen */       \
  48                       "  .byte 664f-663f\n"       /* replacementlen */  \
  49                       ".previous\n"                                     \
  50                       ".section .altinstr_replacement,\"ax\"\n"         \
  51                       "663:\n\t" newinstr "\n664:\n"   /* replacement */\
  52                       ".previous" :: "i" (feature) : "memory")
  53
  54 /*
  55  * Alternative inline assembly with input.
  56  *
  57  * Pecularities:
  58  * No memory clobber here.
  59  * Argument numbers start with 1.
  60  * Best is to use constraints that are fixed size (like (%1) ... "r")
  61  * If you use variable sized constraints like "m" or "g" in the
  62  * replacement maake sure to pad to the worst case length.
  63  */
  64 #define alternative_input(oldinstr, newinstr, feature, input...)        \
  65         asm volatile ("661:\n\t" oldinstr "\n662:\n"                    \
  66                       ".section .altinstructions,\"a\"\n"               \
  67                       "  .align 4\n"                                    \
  68                       "  .long 661b\n"            /* label */           \
  69                       "  .long 663f\n"            /* new instruction */ \
  70                       "  .byte %c0\n"             /* feature bit */     \
  71                       "  .byte 662b-661b\n"       /* sourcelen */       \
  72                       "  .byte 664f-663f\n"       /* replacementlen */  \
  73                       ".previous\n"                                     \
  74                       ".section .altinstr_replacement,\"ax\"\n"         \
  75                       "663:\n\t" newinstr "\n664:\n"   /* replacement */\
  76                       ".previous" :: "i" (feature), ##input)
  77
  78 /*
  79  * Alternative inline assembly for SMP.
  80  *
  81  * alternative_smp() takes two versions (SMP first, UP second) and is
  82  * for more complex stuff such as spinlocks.
  83  *
  84  * The LOCK_PREFIX macro defined here replaces the LOCK and
  85  * LOCK_PREFIX macros used everywhere in the source tree.
  86  *
  87  * SMP alternatives use the same data structures as the other
  88  * alternatives and the X86_FEATURE_UP flag to indicate the case of a
  89  * UP system running a SMP kernel.  The existing apply_alternatives()
  90  * works fine for patching a SMP kernel for UP.
  91  *
  92  * The SMP alternative tables can be kept after boot and contain both
  93  * UP and SMP versions of the instructions to allow switching back to
  94  * SMP at runtime, when hotplugging in a new CPU, which is especially
  95  * useful in virtualized environments.
  96  *
  97  * The very common lock prefix is handled as special case in a
  98  * separate table which is a pure address list without replacement ptr
  99  * and size information.  That keeps the table sizes small.
 100  */
 101
 102 #ifdef CONFIG_SMP
 103 #define alternative_smp(smpinstr, upinstr, args...)                     \
 104         asm volatile ("661:\n\t" smpinstr "\n662:\n"                    \
 105                       ".section .smp_altinstructions,\"a\"\n"           \
 106                       "  .align 4\n"                                    \
 107                       "  .long 661b\n"            /* label */           \
 108                       "  .long 663f\n"            /* new instruction */ \
 109                       "  .byte 0x68\n"            /* X86_FEATURE_UP */  \
 110                       "  .byte 662b-661b\n"       /* sourcelen */       \
 111                       "  .byte 664f-663f\n"       /* replacementlen */  \
 112                       ".previous\n"                                     \
 113                       ".section .smp_altinstr_replacement,\"awx\"\n"    \
 114                       "663:\n\t" upinstr "\n"     /* replacement */     \
 115                       "664:\n\t.fill 662b-661b,1,0x42\n" /* space for original */ \
 116                       ".previous" : args)
 117
 118 #define LOCK_PREFIX \
 119                 ".section .smp_locks,\"a\"\n"   \
 120                 "  .align 4\n"                  \
 121                 "  .long 661f\n" /* address */  \
 122                 ".previous\n"                   \
 123                 "661:\n\tlock; "
 124
 125 #else /* ! CONFIG_SMP */
 126 #define alternative_smp(smpinstr, upinstr, args...) \
 127         asm volatile (upinstr : args)
 128 #define LOCK_PREFIX ""
 129 #endif
 130
 131 #endif /* _I386_ALTERNATIVE_H */