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  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.                 ".pushsection .smp_locks,\"a\"\n"       \
  33.                 ".balign 4\n"                           \
  34.                 ".long 671f - .\n" /* offset */         \
  35.                 ".popsection\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.         s32 instr_offset;       /* original instruction */
  47.         s32 repl_offset;        /* offset to replacement instruction */
  48.         u16 cpuid;              /* cpuid bit set for replacement */
  49.         u8  instrlen;           /* length of original instruction */
  50.         u8  replacementlen;     /* length of new instruction, <= instrlen */
  51. };
  52.  
  53. extern void alternative_instructions(void);
  54. extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
  55.  
  56. struct module;
  57.  
  58. #ifdef CONFIG_SMP
  59. extern void alternatives_smp_module_add(struct module *mod, char *name,
  60.                                         void *locks, void *locks_end,
  61.                                         void *text, void *text_end);
  62. extern void alternatives_smp_module_del(struct module *mod);
  63. extern void alternatives_enable_smp(void);
  64. extern int alternatives_text_reserved(void *start, void *end);
  65. extern bool skip_smp_alternatives;
  66. #else
  67. static inline void alternatives_smp_module_add(struct module *mod, char *name,
  68.                                                void *locks, void *locks_end,
  69.                                                void *text, void *text_end) {}
  70. static inline void alternatives_smp_module_del(struct module *mod) {}
  71. static inline void alternatives_enable_smp(void) {}
  72. static inline int alternatives_text_reserved(void *start, void *end)
  73. {
  74.         return 0;
  75. }
  76. #endif  /* CONFIG_SMP */
  77.  
  78. #define OLDINSTR(oldinstr)      "661:\n\t" oldinstr "\n662:\n"
  79.  
  80. #define b_replacement(number)   "663"#number
  81. #define e_replacement(number)   "664"#number
  82.  
  83. #define alt_slen "662b-661b"
  84. #define alt_rlen(number) e_replacement(number)"f-"b_replacement(number)"f"
  85.  
  86. #define ALTINSTR_ENTRY(feature, number)                                       \
  87.         " .long 661b - .\n"                             /* label           */ \
  88.         " .long " b_replacement(number)"f - .\n"        /* new instruction */ \
  89.         " .word " __stringify(feature) "\n"             /* feature bit     */ \
  90.         " .byte " alt_slen "\n"                         /* source len      */ \
  91.         " .byte " alt_rlen(number) "\n"                 /* replacement len */
  92.  
  93. #define DISCARD_ENTRY(number)                           /* rlen <= slen */    \
  94.         " .byte 0xff + (" alt_rlen(number) ") - (" alt_slen ")\n"
  95.  
  96. #define ALTINSTR_REPLACEMENT(newinstr, feature, number) /* replacement */     \
  97.         b_replacement(number)":\n\t" newinstr "\n" e_replacement(number) ":\n\t"
  98.  
  99. /* alternative assembly primitive: */
  100. #define ALTERNATIVE(oldinstr, newinstr, feature)                        \
  101.         OLDINSTR(oldinstr)                                              \
  102.         ".pushsection .altinstructions,\"a\"\n"                         \
  103.         ALTINSTR_ENTRY(feature, 1)                                      \
  104.         ".popsection\n"                                                 \
  105.         ".pushsection .discard,\"aw\",@progbits\n"                      \
  106.         DISCARD_ENTRY(1)                                                \
  107.         ".popsection\n"                                                 \
  108.         ".pushsection .altinstr_replacement, \"ax\"\n"                  \
  109.         ALTINSTR_REPLACEMENT(newinstr, feature, 1)                      \
  110.         ".popsection"
  111.  
  112. #define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\
  113.         OLDINSTR(oldinstr)                                              \
  114.         ".pushsection .altinstructions,\"a\"\n"                         \
  115.         ALTINSTR_ENTRY(feature1, 1)                                     \
  116.         ALTINSTR_ENTRY(feature2, 2)                                     \
  117.         ".popsection\n"                                                 \
  118.         ".pushsection .discard,\"aw\",@progbits\n"                      \
  119.         DISCARD_ENTRY(1)                                                \
  120.         DISCARD_ENTRY(2)                                                \
  121.         ".popsection\n"                                                 \
  122.         ".pushsection .altinstr_replacement, \"ax\"\n"                  \
  123.         ALTINSTR_REPLACEMENT(newinstr1, feature1, 1)                    \
  124.         ALTINSTR_REPLACEMENT(newinstr2, feature2, 2)                    \
  125.         ".popsection"
  126.  
  127. /*
  128.  * This must be included *after* the definition of ALTERNATIVE due to
  129.  * <asm/arch_hweight.h>
  130.  */
  131. #include <asm/cpufeature.h>
  132.  
  133. /*
  134.  * Alternative instructions for different CPU types or capabilities.
  135.  *
  136.  * This allows to use optimized instructions even on generic binary
  137.  * kernels.
  138.  *
  139.  * length of oldinstr must be longer or equal the length of newinstr
  140.  * It can be padded with nops as needed.
  141.  *
  142.  * For non barrier like inlines please define new variants
  143.  * without volatile and memory clobber.
  144.  */
  145. #define alternative(oldinstr, newinstr, feature)                        \
  146.         asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory")
  147.  
  148. /*
  149.  * Alternative inline assembly with input.
  150.  *
  151.  * Pecularities:
  152.  * No memory clobber here.
  153.  * Argument numbers start with 1.
  154.  * Best is to use constraints that are fixed size (like (%1) ... "r")
  155.  * If you use variable sized constraints like "m" or "g" in the
  156.  * replacement make sure to pad to the worst case length.
  157.  * Leaving an unused argument 0 to keep API compatibility.
  158.  */
  159. #define alternative_input(oldinstr, newinstr, feature, input...)        \
  160.         asm volatile (ALTERNATIVE(oldinstr, newinstr, feature)          \
  161.                 : : "i" (0), ## input)
  162.  
  163. /*
  164.  * This is similar to alternative_input. But it has two features and
  165.  * respective instructions.
  166.  *
  167.  * If CPU has feature2, newinstr2 is used.
  168.  * Otherwise, if CPU has feature1, newinstr1 is used.
  169.  * Otherwise, oldinstr is used.
  170.  */
  171. #define alternative_input_2(oldinstr, newinstr1, feature1, newinstr2,        \
  172.                            feature2, input...)                               \
  173.         asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1,            \
  174.                 newinstr2, feature2)                                         \
  175.                 : : "i" (0), ## input)
  176.  
  177. /* Like alternative_input, but with a single output argument */
  178. #define alternative_io(oldinstr, newinstr, feature, output, input...)   \
  179.         asm volatile (ALTERNATIVE(oldinstr, newinstr, feature)          \
  180.                 : output : "i" (0), ## input)
  181.  
  182. /* Like alternative_io, but for replacing a direct call with another one. */
  183. #define alternative_call(oldfunc, newfunc, feature, output, input...)   \
  184.         asm volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \
  185.                 : output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)
  186.  
  187. /*
  188.  * Like alternative_call, but there are two features and respective functions.
  189.  * If CPU has feature2, function2 is used.
  190.  * Otherwise, if CPU has feature1, function1 is used.
  191.  * Otherwise, old function is used.
  192.  */
  193. #define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2,   \
  194.                            output, input...)                                  \
  195.         asm volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\
  196.                 "call %P[new2]", feature2)                                    \
  197.                 : output : [old] "i" (oldfunc), [new1] "i" (newfunc1),        \
  198.                 [new2] "i" (newfunc2), ## input)
  199.  
  200. /*
  201.  * use this macro(s) if you need more than one output parameter
  202.  * in alternative_io
  203.  */
  204. #define ASM_OUTPUT2(a...) a
  205.  
  206. /*
  207.  * use this macro if you need clobbers but no inputs in
  208.  * alternative_{input,io,call}()
  209.  */
  210. #define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr
  211.  
  212. struct paravirt_patch_site;
  213. #ifdef CONFIG_PARAVIRT
  214. void apply_paravirt(struct paravirt_patch_site *start,
  215.                     struct paravirt_patch_site *end);
  216. #else
  217. static inline void apply_paravirt(struct paravirt_patch_site *start,
  218.                                   struct paravirt_patch_site *end)
  219. {}
  220. #define __parainstructions      NULL
  221. #define __parainstructions_end  NULL
  222. #endif
  223.  
  224. extern void *text_poke_early(void *addr, const void *opcode, size_t len);
  225.  
  226. /*
  227.  * Clear and restore the kernel write-protection flag on the local CPU.
  228.  * Allows the kernel to edit read-only pages.
  229.  * Side-effect: any interrupt handler running between save and restore will have
  230.  * the ability to write to read-only pages.
  231.  *
  232.  * Warning:
  233.  * Code patching in the UP case is safe if NMIs and MCE handlers are stopped and
  234.  * no thread can be preempted in the instructions being modified (no iret to an
  235.  * invalid instruction possible) or if the instructions are changed from a
  236.  * consistent state to another consistent state atomically.
  237.  * On the local CPU you need to be protected again NMI or MCE handlers seeing an
  238.  * inconsistent instruction while you patch.
  239.  */
  240. extern void *text_poke(void *addr, const void *opcode, size_t len);
  241. extern void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler);
  242.  
  243. #endif /* _ASM_X86_ALTERNATIVE_H */
  244.