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
   9 /*
  10  * Alternative inline assembly for SMP.
  11  *
  12  * The LOCK_PREFIX macro defined here replaces the LOCK and
  13  * LOCK_PREFIX macros used everywhere in the source tree.
  14  *
  15  * SMP alternatives use the same data structures as the other
  16  * alternatives and the X86_FEATURE_UP flag to indicate the case of a
  17  * UP system running a SMP kernel.  The existing apply_alternatives()
  18  * works fine for patching a SMP kernel for UP.
  19  *
  20  * The SMP alternative tables can be kept after boot and contain both
  21  * UP and SMP versions of the instructions to allow switching back to
  22  * SMP at runtime, when hotplugging in a new CPU, which is especially
  23  * useful in virtualized environments.
  24  *
  25  * The very common lock prefix is handled as special case in a
  26  * separate table which is a pure address list without replacement ptr
  27  * and size information.  That keeps the table sizes small.
  28  */
  29
  30 #ifdef CONFIG_SMP
  31 #define LOCK_PREFIX \
  32                 ".section .smp_locks,\"a\"\n"   \
  33                 "  .align 8\n"                  \
  34                 "  .quad 661f\n" /* address */  \
  35                 ".previous\n"                   \
  36                 "661:\n\tlock; "
  37
  38 #else /* ! CONFIG_SMP */
  39 #define LOCK_PREFIX ""
  40 #endif
  41
  42 /* This must be included *after* the definition of LOCK_PREFIX */
  43 #include <asm/cpufeature.h>
  44
  45 struct alt_instr {
  46         u8 *instr;              /* original instruction */
  47         u8 *replacement;
  48         u8  cpuid;              /* cpuid bit set for replacement */
  49         u8  instrlen;           /* length of original instruction */
  50         u8  replacementlen;     /* length of new instruction, <= instrlen */
  51         u8  pad[5];
  52 };
  53
  54 extern void alternative_instructions(void);
  55 extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
  56
  57 struct module;
  58
  59 #ifdef CONFIG_SMP
  60 extern void alternatives_smp_module_add(struct module *mod, char *name,
  61                                         void *locks, void *locks_end,
  62                                         void *text, void *text_end);
  63 extern void alternatives_smp_module_del(struct module *mod);
  64 extern void alternatives_smp_switch(int smp);
  65 #else
  66 static inline void alternatives_smp_module_add(struct module *mod, char *name,
  67                                         void *locks, void *locks_end,
  68                                         void *text, void *text_end) {}
  69 static inline void alternatives_smp_module_del(struct module *mod) {}
  70 static inline void alternatives_smp_switch(int smp) {}
  71 #endif
  72
  73 #endif
  74
  75 /*
  76  * Alternative instructions for different CPU types or capabilities.
  77  *
  78  * This allows to use optimized instructions even on generic binary
  79  * kernels.
  80  *
  81  * length of oldinstr must be longer or equal the length of newinstr
  82  * It can be padded with nops as needed.
  83  *
  84  * For non barrier like inlines please define new variants
  85  * without volatile and memory clobber.
  86  */
  87 #define alternative(oldinstr, newinstr, feature)        \
  88         asm volatile ("661:\n\t" oldinstr "\n662:\n"                 \
  89                       ".section .altinstructions,\"a\"\n"            \
  90                       "  .align 8\n"                                   \
  91                       "  .quad 661b\n"            /* label */          \
  92                       "  .quad 663f\n"            /* new instruction */ \
  93                       "  .byte %c0\n"             /* feature bit */    \
  94                       "  .byte 662b-661b\n"       /* sourcelen */      \
  95                       "  .byte 664f-663f\n"       /* replacementlen */ \
  96                       ".previous\n"                                     \
  97                       ".section .altinstr_replacement,\"ax\"\n"         \
  98                       "663:\n\t" newinstr "\n664:\n"   /* replacement */ \
  99                       ".previous" :: "i" (feature) : "memory")
 100
 101 /*
 102  * Alternative inline assembly with input.
 103  *
 104  * Pecularities:
 105  * No memory clobber here.
 106  * Argument numbers start with 1.
 107  * Best is to use constraints that are fixed size (like (%1) ... "r")
 108  * If you use variable sized constraints like "m" or "g" in the
 109  * replacement make sure to pad to the worst case length.
 110  */
 111 #define alternative_input(oldinstr, newinstr, feature, input...)        \
 112         asm volatile ("661:\n\t" oldinstr "\n662:\n"                    \
 113                       ".section .altinstructions,\"a\"\n"               \
 114                       "  .align 8\n"                                    \
 115                       "  .quad 661b\n"            /* label */           \
 116                       "  .quad 663f\n"            /* new instruction */ \
 117                       "  .byte %c0\n"             /* feature bit */     \
 118                       "  .byte 662b-661b\n"       /* sourcelen */       \
 119                       "  .byte 664f-663f\n"       /* replacementlen */  \
 120                       ".previous\n"                                     \
 121                       ".section .altinstr_replacement,\"ax\"\n"         \
 122                       "663:\n\t" newinstr "\n664:\n"   /* replacement */ \
 123                       ".previous" :: "i" (feature), ##input)
 124
 125 /* Like alternative_input, but with a single output argument */
 126 #define alternative_io(oldinstr, newinstr, feature, output, input...) \
 127         asm volatile ("661:\n\t" oldinstr "\n662:\n"                    \
 128                       ".section .altinstructions,\"a\"\n"               \
 129                       "  .align 8\n"                                    \
 130                       "  .quad 661b\n"            /* label */           \
 131                       "  .quad 663f\n"            /* new instruction */ \
 132                       "  .byte %c[feat]\n"        /* feature bit */     \
 133                       "  .byte 662b-661b\n"       /* sourcelen */       \
 134                       "  .byte 664f-663f\n"       /* replacementlen */  \
 135                       ".previous\n"                                     \
 136                       ".section .altinstr_replacement,\"ax\"\n"         \
 137                       "663:\n\t" newinstr "\n664:\n"   /* replacement */ \
 138                       ".previous" : output : [feat] "i" (feature), ##input)
 139
 140 /*
 141  * use this macro(s) if you need more than one output parameter
 142  * in alternative_io
 143  */
 144 #define ASM_OUTPUT2(a, b) a, b
 145
 146 struct paravirt_patch;
 147 #ifdef CONFIG_PARAVIRT
 148 void apply_paravirt(struct paravirt_patch *start, struct paravirt_patch *end);
 149 #else
 150 static inline void
 151 apply_paravirt(struct paravirt_patch *start, struct paravirt_patch *end)
 152 {}
 153 #define __parainstructions NULL
 154 #define __parainstructions_end NULL
 155 #endif
 156
 157 extern void text_poke(void *addr, unsigned char *opcode, int len);
 158
 159 #endif /* _X86_64_ALTERNATIVE_H */