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