release/src-rt-6.x.4708/linux/linux-2.6.36/arch/x86/include/asm/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 <linux/stringify.h>
   7 #include <asm/asm.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_HERE \
  32                 ".section .smp_locks,\"a\"\n"   \
  33                 ".balign 4\n"                   \
  34                 ".long 671f - .\n" /* offset */ \
  35                 ".previous\n"                   \
  36                 "671:"
  37
  38 #define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock; "
  39
  40 #else /* ! CONFIG_SMP */
  41 #define LOCK_PREFIX_HERE ""
  42 #define LOCK_PREFIX ""
  43 #endif
  44
  45 struct alt_instr {
  46         u8 *instr;              /* original instruction */
  47         u8 *replacement;
  48         u16 cpuid;              /* cpuid bit set for replacement */
  49         u8  instrlen;           /* length of original instruction */
  50         u8  replacementlen;     /* length of new instruction, <= instrlen */
  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 extern int alternatives_text_reserved(void *start, void *end);
  68 #else
  69 static inline void alternatives_smp_module_add(struct module *mod, char *name,
  70                                                void *locks, void *locks_end,
  71                                                void *text, void *text_end) {}
  72 static inline void alternatives_smp_module_del(struct module *mod) {}
  73 static inline void alternatives_smp_switch(int smp) {}
  74 static inline int alternatives_text_reserved(void *start, void *end)
  75 {
  76         return 0;
  77 }
  78 #endif  /* CONFIG_SMP */
  79
  80 /* alternative assembly primitive: */
  81 #define ALTERNATIVE(oldinstr, newinstr, feature)                        \
  82                                                                         \
  83       "661:\n\t" oldinstr "\n662:\n"                                    \
  84       ".section .altinstructions,\"a\"\n"                               \
  85       _ASM_ALIGN "\n"                                                   \
  86       _ASM_PTR "661b\n"                         /* label           */   \
  87       _ASM_PTR "663f\n"                         /* new instruction */   \
  88       "  .word " __stringify(feature) "\n"      /* feature bit     */   \
  89       "  .byte 662b-661b\n"                     /* sourcelen       */   \
  90       "  .byte 664f-663f\n"                     /* replacementlen  */   \
  91       ".previous\n"                                                     \
  92       ".section .discard,\"aw\",@progbits\n"                            \
  93       "  .byte 0xff + (664f-663f) - (662b-661b)\n" /* rlen <= slen */   \
  94       ".previous\n"                                                     \
  95       ".section .altinstr_replacement, \"ax\"\n"                        \
  96       "663:\n\t" newinstr "\n664:\n"            /* replacement     */   \
  97       ".previous"
  98
  99 /*
 100  * This must be included *after* the definition of ALTERNATIVE due to
 101  * <asm/arch_hweight.h>
 102  */
 103 #include <asm/cpufeature.h>
 104
 105 /*
 106  * Alternative instructions for different CPU types or capabilities.
 107  *
 108  * This allows to use optimized instructions even on generic binary
 109  * kernels.
 110  *
 111  * length of oldinstr must be longer or equal the length of newinstr
 112  * It can be padded with nops as needed.
 113  *
 114  * For non barrier like inlines please define new variants
 115  * without volatile and memory clobber.
 116  */
 117 #define alternative(oldinstr, newinstr, feature)                        \
 118         asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory")
 119
 120 /*
 121  * Alternative inline assembly with input.
 122  *
 123  * Pecularities:
 124  * No memory clobber here.
 125  * Argument numbers start with 1.
 126  * Best is to use constraints that are fixed size (like (%1) ... "r")
 127  * If you use variable sized constraints like "m" or "g" in the
 128  * replacement make sure to pad to the worst case length.
 129  * Leaving an unused argument 0 to keep API compatibility.
 130  */
 131 #define alternative_input(oldinstr, newinstr, feature, input...)        \
 132         asm volatile (ALTERNATIVE(oldinstr, newinstr, feature)          \
 133                 : : "i" (0), ## input)
 134
 135 /* Like alternative_input, but with a single output argument */
 136 #define alternative_io(oldinstr, newinstr, feature, output, input...)   \
 137         asm volatile (ALTERNATIVE(oldinstr, newinstr, feature)          \
 138                 : output : "i" (0), ## input)
 139
 140 /* Like alternative_io, but for replacing a direct call with another one. */
 141 #define alternative_call(oldfunc, newfunc, feature, output, input...)   \
 142         asm volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \
 143                 : output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)
 144
 145 /*
 146  * use this macro(s) if you need more than one output parameter
 147  * in alternative_io
 148  */
 149 #define ASM_OUTPUT2(a...) a
 150
 151 struct paravirt_patch_site;
 152 #ifdef CONFIG_PARAVIRT
 153 void apply_paravirt(struct paravirt_patch_site *start,
 154                     struct paravirt_patch_site *end);
 155 #else
 156 static inline void apply_paravirt(struct paravirt_patch_site *start,
 157                                   struct paravirt_patch_site *end)
 158 {}
 159 #define __parainstructions      NULL
 160 #define __parainstructions_end  NULL
 161 #endif
 162
 163 /*
 164  * Clear and restore the kernel write-protection flag on the local CPU.
 165  * Allows the kernel to edit read-only pages.
 166  * Side-effect: any interrupt handler running between save and restore will have
 167  * the ability to write to read-only pages.
 168  *
 169  * Warning:
 170  * Code patching in the UP case is safe if NMIs and MCE handlers are stopped and
 171  * no thread can be preempted in the instructions being modified (no iret to an
 172  * invalid instruction possible) or if the instructions are changed from a
 173  * consistent state to another consistent state atomically.
 174  * More care must be taken when modifying code in the SMP case because of
 175  * Intel's errata. text_poke_smp() takes care that errata, but still
 176  * doesn't support NMI/MCE handler code modifying.
 177  * On the local CPU you need to be protected again NMI or MCE handlers seeing an
 178  * inconsistent instruction while you patch.
 179  */
 180 extern void *text_poke(void *addr, const void *opcode, size_t len);
 181 extern void *text_poke_smp(void *addr, const void *opcode, size_t len);
 182
 183 #endif /* _ASM_X86_ALTERNATIVE_H */