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   1 #ifndef _X86_64_ALTERNATIVE_H
   2 #define _X86_64_ALTERNATIVE_H
   3
   4 #ifdef __KERNEL__
   5
   6 #include <linux/types.h>
   7
   8 struct alt_instr {
   9         u8 *instr;              /* original instruction */
  10         u8 *replacement;
  11         u8  cpuid;              /* cpuid bit set for replacement */
  12         u8  instrlen;           /* length of original instruction */
  13         u8  replacementlen;     /* length of new instruction, <= instrlen */
  14         u8  pad[5];
  15 };
  16
  17 extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
  18
  19 struct module;
  20
  21 #ifdef CONFIG_SMP
  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 #else
  28 static inline void alternatives_smp_module_add(struct module *mod, char *name,
  29                                         void *locks, void *locks_end,
  30                                         void *text, void *text_end) {}
  31 static inline void alternatives_smp_module_del(struct module *mod) {}
  32 static inline void alternatives_smp_switch(int smp) {}
  33 #endif
  34
  35 #endif
  36
  37 /*
  38  * Alternative instructions for different CPU types or capabilities.
  39  *
  40  * This allows to use optimized instructions even on generic binary
  41  * kernels.
  42  *
  43  * length of oldinstr must be longer or equal the length of newinstr
  44  * It can be padded with nops as needed.
  45  *
  46  * For non barrier like inlines please define new variants
  47  * without volatile and memory clobber.
  48  */
  49 #define alternative(oldinstr, newinstr, feature)        \
  50         asm volatile ("661:\n\t" oldinstr "\n662:\n"                 \
  51                       ".section .altinstructions,\"a\"\n"            \
  52                       "  .align 8\n"                                   \
  53                       "  .quad 661b\n"            /* label */          \
  54                       "  .quad 663f\n"            /* new instruction */ \
  55                       "  .byte %c0\n"             /* feature bit */    \
  56                       "  .byte 662b-661b\n"       /* sourcelen */      \
  57                       "  .byte 664f-663f\n"       /* replacementlen */ \
  58                       ".previous\n"                                     \
  59                       ".section .altinstr_replacement,\"ax\"\n"         \
  60                       "663:\n\t" newinstr "\n664:\n"   /* replacement */ \
  61                       ".previous" :: "i" (feature) : "memory")
  62
  63 /*
  64  * Alternative inline assembly with input.
  65  *
  66  * Pecularities:
  67  * No memory clobber here.
  68  * Argument numbers start with 1.
  69  * Best is to use constraints that are fixed size (like (%1) ... "r")
  70  * If you use variable sized constraints like "m" or "g" in the
  71  * replacement make sure to pad to the worst case length.
  72  */
  73 #define alternative_input(oldinstr, newinstr, feature, input...)        \
  74         asm volatile ("661:\n\t" oldinstr "\n662:\n"                    \
  75                       ".section .altinstructions,\"a\"\n"               \
  76                       "  .align 8\n"                                    \
  77                       "  .quad 661b\n"            /* label */           \
  78                       "  .quad 663f\n"            /* new instruction */ \
  79                       "  .byte %c0\n"             /* feature bit */     \
  80                       "  .byte 662b-661b\n"       /* sourcelen */       \
  81                       "  .byte 664f-663f\n"       /* replacementlen */  \
  82                       ".previous\n"                                     \
  83                       ".section .altinstr_replacement,\"ax\"\n"         \
  84                       "663:\n\t" newinstr "\n664:\n"   /* replacement */ \
  85                       ".previous" :: "i" (feature), ##input)
  86
  87 /* Like alternative_input, but with a single output argument */
  88 #define alternative_io(oldinstr, newinstr, feature, output, input...) \
  89         asm volatile ("661:\n\t" oldinstr "\n662:\n"                    \
  90                       ".section .altinstructions,\"a\"\n"               \
  91                       "  .align 8\n"                                    \
  92                       "  .quad 661b\n"            /* label */           \
  93                       "  .quad 663f\n"            /* new instruction */ \
  94                       "  .byte %c[feat]\n"        /* feature bit */     \
  95                       "  .byte 662b-661b\n"       /* sourcelen */       \
  96                       "  .byte 664f-663f\n"       /* replacementlen */  \
  97                       ".previous\n"                                     \
  98                       ".section .altinstr_replacement,\"ax\"\n"         \
  99                       "663:\n\t" newinstr "\n664:\n"   /* replacement */ \
 100                       ".previous" : output : [feat] "i" (feature), ##input)
 101
 102 /*
 103  * Alternative inline assembly for SMP.
 104  *
 105  * alternative_smp() takes two versions (SMP first, UP second) and is
 106  * for more complex stuff such as spinlocks.
 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 alternative_smp(smpinstr, upinstr, args...)                     \
 128         asm volatile ("661:\n\t" smpinstr "\n662:\n"                    \
 129                       ".section .smp_altinstructions,\"a\"\n"           \
 130                       "  .align 8\n"                                    \
 131                       "  .quad 661b\n"            /* label */           \
 132                       "  .quad 663f\n"            /* new instruction */ \
 133                       "  .byte 0x66\n"            /* X86_FEATURE_UP */  \
 134                       "  .byte 662b-661b\n"       /* sourcelen */       \
 135                       "  .byte 664f-663f\n"       /* replacementlen */  \
 136                       ".previous\n"                                     \
 137                       ".section .smp_altinstr_replacement,\"awx\"\n"    \
 138                       "663:\n\t" upinstr "\n"     /* replacement */     \
 139                       "664:\n\t.fill 662b-661b,1,0x42\n" /* space for original */ \
 140                       ".previous" : args)
 141
 142 #define LOCK_PREFIX \
 143                 ".section .smp_locks,\"a\"\n"   \
 144                 "  .align 8\n"                  \
 145                 "  .quad 661f\n" /* address */  \
 146                 ".previous\n"                   \
 147                 "661:\n\tlock; "
 148
 149 #else /* ! CONFIG_SMP */
 150 #define alternative_smp(smpinstr, upinstr, args...) \
 151         asm volatile (upinstr : args)
 152 #define LOCK_PREFIX ""
 153 #endif
 154
 155 #endif /* _X86_64_ALTERNATIVE_H */