LCOV - code coverage report
Current view: top level - arch/x86/include/asm - alternative.h (source / functions) Hit Total Coverage
Test: coverage.info Lines: 1 1 100.0 %
Date: 2017-01-25 Functions: 0 0 -

          Line data    Source code
       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 \
      32             :                 ".section .smp_locks,\"a\"\n"       \
      33             :                 _ASM_ALIGN "\n"                       \
      34             :                 _ASM_PTR "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  pad1;
      52             : #ifdef CONFIG_X86_64
      53             :         u32 pad2;
      54             : #endif
      55             : };
      56             : 
      57             : extern void alternative_instructions(void);
      58             : extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
      59           1 : 
      60             : struct module;
      61             : 
      62             : #ifdef CONFIG_SMP
      63             : extern void alternatives_smp_module_add(struct module *mod, char *name,
      64             :                                         void *locks, void *locks_end,
      65             :                                         void *text, void *text_end);
      66             : extern void alternatives_smp_module_del(struct module *mod);
      67             : extern void alternatives_smp_switch(int smp);
      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             : #endif  /* CONFIG_SMP */
      75             : 
      76             : /* alternative assembly primitive: */
      77             : #define ALTERNATIVE(oldinstr, newinstr, feature)                        \
      78             :                                                                         \
      79             :       "661:\n\t" oldinstr "\n662:\n"                                        \
      80             :       ".section .altinstructions,\"a\"\n"                           \
      81             :       _ASM_ALIGN "\n"                                                 \
      82             :       _ASM_PTR "661b\n"                               /* label           */   \
      83             :       _ASM_PTR "663f\n"                               /* new instruction */   \
      84             :       "     .byte " __stringify(feature) "\n"       /* feature bit     */   \
      85             :       "     .byte 662b-661b\n"                        /* sourcelen       */   \
      86             :       "     .byte 664f-663f\n"                        /* replacementlen  */   \
      87             :       "     .byte 0xff + (664f-663f) - (662b-661b)\n" /* rlen <= slen */   \
      88             :       ".previous\n"                                                   \
      89             :       ".section .altinstr_replacement, \"ax\"\n"                    \
      90             :       "663:\n\t" newinstr "\n664:\n"                /* replacement     */   \
      91             :       ".previous"
      92             : 
      93             : /*
      94             :  * Alternative instructions for different CPU types or capabilities.
      95             :  *
      96             :  * This allows to use optimized instructions even on generic binary
      97             :  * kernels.
      98             :  *
      99             :  * length of oldinstr must be longer or equal the length of newinstr
     100             :  * It can be padded with nops as needed.
     101             :  *
     102             :  * For non barrier like inlines please define new variants
     103             :  * without volatile and memory clobber.
     104             :  */
     105             : #define alternative(oldinstr, newinstr, feature)                        \
     106             :         asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory")
     107             : 
     108             : /*
     109             :  * Alternative inline assembly with input.
     110             :  *
     111             :  * Pecularities:
     112             :  * No memory clobber here.
     113             :  * Argument numbers start with 1.
     114             :  * Best is to use constraints that are fixed size (like (%1) ... "r")
     115             :  * If you use variable sized constraints like "m" or "g" in the
     116             :  * replacement make sure to pad to the worst case length.
     117             :  * Leaving an unused argument 0 to keep API compatibility.
     118             :  */
     119             : #define alternative_input(oldinstr, newinstr, feature, input...)        \
     120             :         asm volatile (ALTERNATIVE(oldinstr, newinstr, feature)          \
     121             :                 : : "i" (0), ## input)
     122             : 
     123             : /* Like alternative_input, but with a single output argument */
     124             : #define alternative_io(oldinstr, newinstr, feature, output, input...)   \
     125             :         asm volatile (ALTERNATIVE(oldinstr, newinstr, feature)          \
     126             :                 : output : "i" (0), ## input)
     127             : 
     128             : /*
     129             :  * use this macro(s) if you need more than one output parameter
     130             :  * in alternative_io
     131             :  */
     132             : #define ASM_OUTPUT2(a, b) a, b
     133             : 
     134             : struct paravirt_patch_site;
     135             : #ifdef CONFIG_PARAVIRT
     136             : void apply_paravirt(struct paravirt_patch_site *start,
     137             :                     struct paravirt_patch_site *end);
     138             : #else
     139             : static inline void apply_paravirt(struct paravirt_patch_site *start,
     140             :                                   struct paravirt_patch_site *end)
     141             : {}
     142             : #define __parainstructions      NULL
     143             : #define __parainstructions_end  NULL
     144             : #endif
     145             : 
     146             : /*
     147             :  * Clear and restore the kernel write-protection flag on the local CPU.
     148             :  * Allows the kernel to edit read-only pages.
     149             :  * Side-effect: any interrupt handler running between save and restore will have
     150             :  * the ability to write to read-only pages.
     151             :  *
     152             :  * Warning:
     153             :  * Code patching in the UP case is safe if NMIs and MCE handlers are stopped and
     154             :  * no thread can be preempted in the instructions being modified (no iret to an
     155             :  * invalid instruction possible) or if the instructions are changed from a
     156             :  * consistent state to another consistent state atomically.
     157             :  * More care must be taken when modifying code in the SMP case because of
     158             :  * Intel's errata.
     159             :  * On the local CPU you need to be protected again NMI or MCE handlers seeing an
     160             :  * inconsistent instruction while you patch.
     161             :  */
     162             : extern void *text_poke(void *addr, const void *opcode, size_t len);
     163             : 
     164             : #endif /* _ASM_X86_ALTERNATIVE_H */

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