include/asm-x86/alternative.h

   1 #ifndef _ASM_X86_ALTERNATIVE_H
   2 #define _ASM_X86_ALTERNATIVE_H
   3
   4 #include <linux/types.h>
   5 #include <linux/stddef.h>
   6 #include <asm/asm.h>
   7
   8 /*
   9  * Alternative inline assembly for SMP.
  10  *
  11  * The LOCK_PREFIX macro defined here replaces the LOCK and
  12  * LOCK_PREFIX macros used everywhere in the source tree.
  13  *
  14  * SMP alternatives use the same data structures as the other
  15  * alternatives and the X86_FEATURE_UP flag to indicate the case of a
  16  * UP system running a SMP kernel.  The existing apply_alternatives()
  17  * works fine for patching a SMP kernel for UP.
  18  *
  19  * The SMP alternative tables can be kept after boot and contain both
  20  * UP and SMP versions of the instructions to allow switching back to
  21  * SMP at runtime, when hotplugging in a new CPU, which is especially
  22  * useful in virtualized environments.
  23  *
  24  * The very common lock prefix is handled as special case in a
  25  * separate table which is a pure address list without replacement ptr
  26  * and size information.  That keeps the table sizes small.
  27  */
  28
  29 #ifdef CONFIG_SMP
  30 #define LOCK_PREFIX \
  31                 ".section .smp_locks,\"a\"\n"   \
  32                 _ASM_ALIGN "\n"                 \
  33                 _ASM_PTR "661f\n" /* address */ \
  34                 ".previous\n"                   \
  35                 "661:\n\tlock; "
  36
  37 #else /* ! CONFIG_SMP */
  38 #define LOCK_PREFIX ""
  39 #endif
  40
  41 /* This must be included *after* the definition of LOCK_PREFIX */
  42 #include <asm/cpufeature.h>
  43
  44 struct alt_instr {
  45         u8 *instr;              /* original instruction */
  46         u8 *replacement;
  47         u8  cpuid;              /* cpuid bit set for replacement */
  48         u8  instrlen;           /* length of original instruction */
  49         u8  replacementlen;     /* length of new instruction, <= instrlen */
  50         u8  pad1;
  51 #ifdef CONFIG_X86_64
  52         u32 pad2;
  53 #endif
  54 };
  55
  56 extern void alternative_instructions(void);
  57 extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
  58
  59 struct module;
  60
  61 #ifdef CONFIG_SMP
  62 extern void alternatives_smp_module_add(struct module *mod, char *name,
  63                                         void *locks, void *locks_end,
  64                                         void *text, void *text_end);
  65 extern void alternatives_smp_module_del(struct module *mod);
  66 extern void alternatives_smp_switch(int smp);
  67 #else
  68 static inline void alternatives_smp_module_add(struct module *mod, char *name,
  69                                         void *locks, void *locks_end,
  70                                         void *text, void *text_end) {}
  71 static inline void alternatives_smp_module_del(struct module *mod) {}
  72 static inline void alternatives_smp_switch(int smp) {}
  73 #endif  /* CONFIG_SMP */
  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                       _ASM_ALIGN "\n"                                   \
  91                       _ASM_PTR "661b\n"         /* label */             \
  92                       _ASM_PTR "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                       _ASM_ALIGN "\n"                                   \
 115                       _ASM_PTR "661b\n"         /* label */             \
 116                       _ASM_PTR "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                       _ASM_ALIGN "\n"                                   \
 130                       _ASM_PTR "661b\n"         /* label */             \
 131                       _ASM_PTR "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_site;
 147 #ifdef CONFIG_PARAVIRT
 148 void apply_paravirt(struct paravirt_patch_site *start,
 149                     struct paravirt_patch_site *end);
 150 #else
 151 static inline void
 152 apply_paravirt(struct paravirt_patch_site *start,
 153                struct paravirt_patch_site *end)
 154 {}
 155 #define __parainstructions      NULL
 156 #define __parainstructions_end  NULL
 157 #endif
 158
 159 extern void add_nops(void *insns, unsigned int len);
 160
 161 /*
 162  * Clear and restore the kernel write-protection flag on the local CPU.
 163  * Allows the kernel to edit read-only pages.
 164  * Side-effect: any interrupt handler running between save and restore will have
 165  * the ability to write to read-only pages.
 166  *
 167  * Warning:
 168  * Code patching in the UP case is safe if NMIs and MCE handlers are stopped and
 169  * no thread can be preempted in the instructions being modified (no iret to an
 170  * invalid instruction possible) or if the instructions are changed from a
 171  * consistent state to another consistent state atomically.
 172  * More care must be taken when modifying code in the SMP case because of
 173  * Intel's errata.
 174  * On the local CPU you need to be protected again NMI or MCE handlers seeing an
 175  * inconsistent instruction while you patch.
 176  * The _early version expects the memory to already be RW.
 177  */
 178
 179 extern void *text_poke(void *addr, const void *opcode, size_t len);
 180 extern void *text_poke_early(void *addr, const void *opcode, size_t len);
 181
 182 #endif /* _ASM_X86_ALTERNATIVE_H */