arch/x86/include/asm/jump_label.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _ASM_X86_JUMP_LABEL_H
   3 #define _ASM_X86_JUMP_LABEL_H
   4
   5 #ifndef HAVE_JUMP_LABEL
   6 /*
   7  * For better or for worse, if jump labels (the gcc extension) are missing,
   8  * then the entire static branch patching infrastructure is compiled out.
   9  * If that happens, the code in here will malfunction.  Raise a compiler
  10  * error instead.
  11  *
  12  * In theory, jump labels and the static branch patching infrastructure
  13  * could be decoupled to fix this.
  14  */
  15 #error asm/jump_label.h included on a non-jump-label kernel
  16 #endif
  17
  18 #define JUMP_LABEL_NOP_SIZE 5
  19
  20 #ifdef CONFIG_X86_64
  21 # define STATIC_KEY_INIT_NOP P6_NOP5_ATOMIC
  22 #else
  23 # define STATIC_KEY_INIT_NOP GENERIC_NOP5_ATOMIC
  24 #endif
  25
  26 #include <asm/asm.h>
  27 #include <asm/nops.h>
  28
  29 #ifndef __ASSEMBLY__
  30
  31 #include <linux/stringify.h>
  32 #include <linux/types.h>
  33
  34 static __always_inline bool arch_static_branch(struct static_key *key, bool branch)
  35 {
  36         asm_volatile_goto("1:"
  37                 ".byte " __stringify(STATIC_KEY_INIT_NOP) "\n\t"
  38                 ".pushsection __jump_table,  \"aw\" \n\t"
  39                 _ASM_ALIGN "\n\t"
  40                 _ASM_PTR "1b, %l[l_yes], %c0 + %c1 \n\t"
  41                 ".popsection \n\t"
  42                 : :  "i" (key), "i" (branch) : : l_yes);
  43
  44         return false;
  45 l_yes:
  46         return true;
  47 }
  48
  49 static __always_inline bool arch_static_branch_jump(struct static_key *key, bool branch)
  50 {
  51         asm_volatile_goto("1:"
  52                 ".byte 0xe9\n\t .long %l[l_yes] - 2f\n\t"
  53                 "2:\n\t"
  54                 ".pushsection __jump_table,  \"aw\" \n\t"
  55                 _ASM_ALIGN "\n\t"
  56                 _ASM_PTR "1b, %l[l_yes], %c0 + %c1 \n\t"
  57                 ".popsection \n\t"
  58                 : :  "i" (key), "i" (branch) : : l_yes);
  59
  60         return false;
  61 l_yes:
  62         return true;
  63 }
  64
  65 #ifdef CONFIG_X86_64
  66 typedef u64 jump_label_t;
  67 #else
  68 typedef u32 jump_label_t;
  69 #endif
  70
  71 struct jump_entry {
  72         jump_label_t code;
  73         jump_label_t target;
  74         jump_label_t key;
  75 };
  76
  77 #else   /* __ASSEMBLY__ */
  78
  79 .macro STATIC_JUMP_IF_TRUE target, key, def
  80 .Lstatic_jump_\@:
  81         .if \def
  82         /* Equivalent to "jmp.d32 \target" */
  83         .byte           0xe9
  84         .long           \target - .Lstatic_jump_after_\@
  85 .Lstatic_jump_after_\@:
  86         .else
  87         .byte           STATIC_KEY_INIT_NOP
  88         .endif
  89         .pushsection __jump_table, "aw"
  90         _ASM_ALIGN
  91         _ASM_PTR        .Lstatic_jump_\@, \target, \key
  92         .popsection
  93 .endm
  94
  95 .macro STATIC_JUMP_IF_FALSE target, key, def
  96 .Lstatic_jump_\@:
  97         .if \def
  98         .byte           STATIC_KEY_INIT_NOP
  99         .else
 100         /* Equivalent to "jmp.d32 \target" */
 101         .byte           0xe9
 102         .long           \target - .Lstatic_jump_after_\@
 103 .Lstatic_jump_after_\@:
 104         .endif
 105         .pushsection __jump_table, "aw"
 106         _ASM_ALIGN
 107         _ASM_PTR        .Lstatic_jump_\@, \target, \key + 1
 108         .popsection
 109 .endm
 110
 111 #endif  /* __ASSEMBLY__ */
 112
 113 #endif