arch/x86/kernel/jump_label.c

   1 /*
   2  * jump label x86 support
   3  *
   4  * Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
   5  *
   6  */
   7 #include <linux/jump_label.h>
   8 #include <linux/memory.h>
   9 #include <linux/uaccess.h>
  10 #include <linux/module.h>
  11 #include <linux/list.h>
  12 #include <linux/jhash.h>
  13 #include <linux/cpu.h>
  14 #include <asm/kprobes.h>
  15 #include <asm/alternative.h>
  16
  17 #ifdef HAVE_JUMP_LABEL
  18
  19 union jump_code_union {
  20         char code[JUMP_LABEL_NOP_SIZE];
  21         struct {
  22                 char jump;
  23                 int offset;
  24         } __attribute__((packed));
  25 };
  26
  27 static void __jump_label_transform(struct jump_entry *entry,
  28                                    enum jump_label_type type,
  29                                    void *(*poker)(void *, const void *, size_t))
  30 {
  31         union jump_code_union code;
  32
  33         if (type == JUMP_LABEL_ENABLE) {
  34                 code.jump = 0xe9;
  35                 code.offset = entry->target -
  36                                 (entry->code + JUMP_LABEL_NOP_SIZE);
  37         } else
  38                 memcpy(&code, ideal_nops[NOP_ATOMIC5], JUMP_LABEL_NOP_SIZE);
  39
  40         (*poker)((void *)entry->code, &code, JUMP_LABEL_NOP_SIZE);
  41 }
  42
  43 void arch_jump_label_transform(struct jump_entry *entry,
  44                                enum jump_label_type type)
  45 {
  46         get_online_cpus();
  47         mutex_lock(&text_mutex);
  48         __jump_label_transform(entry, type, text_poke_smp);
  49         mutex_unlock(&text_mutex);
  50         put_online_cpus();
  51 }
  52
  53 __init_or_module void arch_jump_label_transform_static(struct jump_entry *entry,
  54                                       enum jump_label_type type)
  55 {
  56         __jump_label_transform(entry, type, text_poke_early);
  57 }
  58
  59 #endif