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