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 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
  28 #endif
  29
  30 /*
  31  * Alternative instructions for different CPU types or capabilities.
  32  *
  33  * This allows to use optimized instructions even on generic binary
  34  * kernels.
  35  *
  36  * length of oldinstr must be longer or equal the length of newinstr
  37  * It can be padded with nops as needed.
  38  *
  39  * For non barrier like inlines please define new variants
  40  * without volatile and memory clobber.
  41  */
  42 #define alternative(oldinstr, newinstr, feature)                        \
  43         asm volatile ("661:\n\t" oldinstr "\n662:\n"                    \
  44                       ".section .altinstructions,\"a\"\n"               \
  45                       "  .align 4\n"                                    \
  46                       "  .long 661b\n"            /* label */           \
  47                       "  .long 663f\n"            /* new instruction */ \
  48                       "  .byte %c0\n"             /* feature bit */     \
  49                       "  .byte 662b-661b\n"       /* sourcelen */       \
  50                       "  .byte 664f-663f\n"       /* replacementlen */  \
  51                       ".previous\n"                                     \
  52                       ".section .altinstr_replacement,\"ax\"\n"         \
  53                       "663:\n\t" newinstr "\n664:\n"   /* replacement */\
  54                       ".previous" :: "i" (feature) : "memory")
  55
  56 /*
  57  * Alternative inline assembly with input.
  58  *
  59  * Pecularities:
  60  * No memory clobber here.
  61  * Argument numbers start with 1.
  62  * Best is to use constraints that are fixed size (like (%1) ... "r")
  63  * If you use variable sized constraints like "m" or "g" in the
  64  * replacement maake sure to pad to the worst case length.
  65  */
  66 #define alternative_input(oldinstr, newinstr, feature, input...)        \
  67         asm volatile ("661:\n\t" oldinstr "\n662:\n"                    \
  68                       ".section .altinstructions,\"a\"\n"               \
  69                       "  .align 4\n"                                    \
  70                       "  .long 661b\n"            /* label */           \
  71                       "  .long 663f\n"            /* new instruction */ \
  72                       "  .byte %c0\n"             /* feature bit */     \
  73                       "  .byte 662b-661b\n"       /* sourcelen */       \
  74                       "  .byte 664f-663f\n"       /* replacementlen */  \
  75                       ".previous\n"                                     \
  76                       ".section .altinstr_replacement,\"ax\"\n"         \
  77                       "663:\n\t" newinstr "\n664:\n"   /* replacement */\
  78                       ".previous" :: "i" (feature), ##input)
  79
  80 /*
  81  * Alternative inline assembly for SMP.
  82  *
  83  * alternative_smp() takes two versions (SMP first, UP second) and is
  84  * for more complex stuff such as spinlocks.
  85  *
  86  * The LOCK_PREFIX macro defined here replaces the LOCK and
  87  * LOCK_PREFIX macros used everywhere in the source tree.
  88  *
  89  * SMP alternatives use the same data structures as the other
  90  * alternatives and the X86_FEATURE_UP flag to indicate the case of a
  91  * UP system running a SMP kernel.  The existing apply_alternatives()
  92  * works fine for patching a SMP kernel for UP.
  93  *
  94  * The SMP alternative tables can be kept after boot and contain both
  95  * UP and SMP versions of the instructions to allow switching back to
  96  * SMP at runtime, when hotplugging in a new CPU, which is especially
  97  * useful in virtualized environments.
  98  *
  99  * The very common lock prefix is handled as special case in a
 100  * separate table which is a pure address list without replacement ptr
 101  * and size information.  That keeps the table sizes small.
 102  */
 103
 104 #ifdef CONFIG_SMP
 105 #define alternative_smp(smpinstr, upinstr, args...)                     \
 106         asm volatile ("661:\n\t" smpinstr "\n662:\n"                    \
 107                       ".section .smp_altinstructions,\"a\"\n"           \
 108                       "  .align 4\n"                                    \
 109                       "  .long 661b\n"            /* label */           \
 110                       "  .long 663f\n"            /* new instruction */ \
 111                       "  .byte 0x68\n"            /* X86_FEATURE_UP */  \
 112                       "  .byte 662b-661b\n"       /* sourcelen */       \
 113                       "  .byte 664f-663f\n"       /* replacementlen */  \
 114                       ".previous\n"                                     \
 115                       ".section .smp_altinstr_replacement,\"awx\"\n"    \
 116                       "663:\n\t" upinstr "\n"     /* replacement */     \
 117                       "664:\n\t.fill 662b-661b,1,0x42\n" /* space for original */ \
 118                       ".previous" : args)
 119
 120 #define LOCK_PREFIX \
 121                 ".section .smp_locks,\"a\"\n"   \
 122                 "  .align 4\n"                  \
 123                 "  .long 661f\n" /* address */  \
 124                 ".previous\n"                   \
 125                 "661:\n\tlock; "
 126
 127 #else /* ! CONFIG_SMP */
 128 #define alternative_smp(smpinstr, upinstr, args...) \
 129         asm volatile (upinstr : args)
 130 #define LOCK_PREFIX ""
 131 #endif
 132
 133 #endif /* _I386_ALTERNATIVE_H */