include/asm-x86_64/alternative.h

   1 #ifndef _X86_64_ALTERNATIVE_H
   2 #define _X86_64_ALTERNATIVE_H
   3
   4 #ifdef __KERNEL__
   5
   6 #include <linux/types.h>
   7 #include <linux/stddef.h>
   8 #include <asm/cpufeature.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[5];
  17 };
  18
  19 extern void alternative_instructions(void);
  20 extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
  21
  22 struct module;
  23
  24 #ifdef CONFIG_SMP
  25 extern void alternatives_smp_module_add(struct module *mod, char *name,
  26                                         void *locks, void *locks_end,
  27                                         void *text, void *text_end);
  28 extern void alternatives_smp_module_del(struct module *mod);
  29 extern void alternatives_smp_switch(int smp);
  30 #else
  31 static inline void alternatives_smp_module_add(struct module *mod, char *name,
  32                                         void *locks, void *locks_end,
  33                                         void *text, void *text_end) {}
  34 static inline void alternatives_smp_module_del(struct module *mod) {}
  35 static inline void alternatives_smp_switch(int smp) {}
  36 #endif
  37
  38 #endif
  39
  40 /*
  41  * Alternative instructions for different CPU types or capabilities.
  42  *
  43  * This allows to use optimized instructions even on generic binary
  44  * kernels.
  45  *
  46  * length of oldinstr must be longer or equal the length of newinstr
  47  * It can be padded with nops as needed.
  48  *
  49  * For non barrier like inlines please define new variants
  50  * without volatile and memory clobber.
  51  */
  52 #define alternative(oldinstr, newinstr, feature)        \
  53         asm volatile ("661:\n\t" oldinstr "\n662:\n"                 \
  54                       ".section .altinstructions,\"a\"\n"            \
  55                       "  .align 8\n"                                   \
  56                       "  .quad 661b\n"            /* label */          \
  57                       "  .quad 663f\n"            /* new instruction */ \
  58                       "  .byte %c0\n"             /* feature bit */    \
  59                       "  .byte 662b-661b\n"       /* sourcelen */      \
  60                       "  .byte 664f-663f\n"       /* replacementlen */ \
  61                       ".previous\n"                                     \
  62                       ".section .altinstr_replacement,\"ax\"\n"         \
  63                       "663:\n\t" newinstr "\n664:\n"   /* replacement */ \
  64                       ".previous" :: "i" (feature) : "memory")
  65
  66 /*
  67  * Alternative inline assembly with input.
  68  *
  69  * Pecularities:
  70  * No memory clobber here.
  71  * Argument numbers start with 1.
  72  * Best is to use constraints that are fixed size (like (%1) ... "r")
  73  * If you use variable sized constraints like "m" or "g" in the
  74  * replacement make sure to pad to the worst case length.
  75  */
  76 #define alternative_input(oldinstr, newinstr, feature, input...)        \
  77         asm volatile ("661:\n\t" oldinstr "\n662:\n"                    \
  78                       ".section .altinstructions,\"a\"\n"               \
  79                       "  .align 8\n"                                    \
  80                       "  .quad 661b\n"            /* label */           \
  81                       "  .quad 663f\n"            /* new instruction */ \
  82                       "  .byte %c0\n"             /* feature bit */     \
  83                       "  .byte 662b-661b\n"       /* sourcelen */       \
  84                       "  .byte 664f-663f\n"       /* replacementlen */  \
  85                       ".previous\n"                                     \
  86                       ".section .altinstr_replacement,\"ax\"\n"         \
  87                       "663:\n\t" newinstr "\n664:\n"   /* replacement */ \
  88                       ".previous" :: "i" (feature), ##input)
  89
  90 /* Like alternative_input, but with a single output argument */
  91 #define alternative_io(oldinstr, newinstr, feature, output, input...) \
  92         asm volatile ("661:\n\t" oldinstr "\n662:\n"                    \
  93                       ".section .altinstructions,\"a\"\n"               \
  94                       "  .align 8\n"                                    \
  95                       "  .quad 661b\n"            /* label */           \
  96                       "  .quad 663f\n"            /* new instruction */ \
  97                       "  .byte %c[feat]\n"        /* feature bit */     \
  98                       "  .byte 662b-661b\n"       /* sourcelen */       \
  99                       "  .byte 664f-663f\n"       /* replacementlen */  \
 100                       ".previous\n"                                     \
 101                       ".section .altinstr_replacement,\"ax\"\n"         \
 102                       "663:\n\t" newinstr "\n664:\n"   /* replacement */ \
 103                       ".previous" : output : [feat] "i" (feature), ##input)
 104
 105 /*
 106  * Alternative inline assembly for SMP.
 107  *
 108  * The LOCK_PREFIX macro defined here replaces the LOCK and
 109  * LOCK_PREFIX macros used everywhere in the source tree.
 110  *
 111  * SMP alternatives use the same data structures as the other
 112  * alternatives and the X86_FEATURE_UP flag to indicate the case of a
 113  * UP system running a SMP kernel.  The existing apply_alternatives()
 114  * works fine for patching a SMP kernel for UP.
 115  *
 116  * The SMP alternative tables can be kept after boot and contain both
 117  * UP and SMP versions of the instructions to allow switching back to
 118  * SMP at runtime, when hotplugging in a new CPU, which is especially
 119  * useful in virtualized environments.
 120  *
 121  * The very common lock prefix is handled as special case in a
 122  * separate table which is a pure address list without replacement ptr
 123  * and size information.  That keeps the table sizes small.
 124  */
 125
 126 #ifdef CONFIG_SMP
 127 #define LOCK_PREFIX \
 128                 ".section .smp_locks,\"a\"\n"   \
 129                 "  .align 8\n"                  \
 130                 "  .quad 661f\n" /* address */  \
 131                 ".previous\n"                   \
 132                 "661:\n\tlock; "
 133
 134 #else /* ! CONFIG_SMP */
 135 #define LOCK_PREFIX ""
 136 #endif
 137
 138 struct paravirt_patch;
 139 #ifdef CONFIG_PARAVIRT
 140 void apply_paravirt(struct paravirt_patch *start, struct paravirt_patch *end);
 141 #else
 142 static inline void
 143 apply_paravirt(struct paravirt_patch *start, struct paravirt_patch *end)
 144 {}
 145 #define __start_parainstructions NULL
 146 #define __stop_parainstructions NULL
 147 #endif
 148
 149 #endif /* _X86_64_ALTERNATIVE_H */