include/asm-i386/alternative.h

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