jump_label.c

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/*
 * jump label x86 support
 *
 * Copyright (C) 2009 Jason Baron <[email protected]>
 *
 */
#include <linux/jump_label.h>
#include <linux/memory.h>
#include <linux/uaccess.h>
#include <linux/module.h>
#include <linux/list.h>
#include <linux/jhash.h>
#include <linux/cpu.h>
#include <asm/kprobes.h>
#include <asm/alternative.h>

#ifdef HAVE_JUMP_LABEL

union jump_code_union {
    char code[JUMP_LABEL_NOP_SIZE];
    struct {
        char jump;
        int offset;
    } __attribute__((packed));
};

static void __jump_label_transform(struct jump_entry *entry,
                   enum jump_label_type type,
                   void *(*poker)(void *, const void *, size_t))
{
    union jump_code_union code;

    if (type == JUMP_LABEL_ENABLE) {
        code.jump = 0xe9;
        code.offset = entry->target -
                (entry->code + JUMP_LABEL_NOP_SIZE);
    } else
        memcpy(&code, ideal_nops[NOP_ATOMIC5], JUMP_LABEL_NOP_SIZE);

    (*poker)((void *)entry->code, &code, JUMP_LABEL_NOP_SIZE);
}

void arch_jump_label_transform(struct jump_entry *entry,
                   enum jump_label_type type)
{
    get_online_cpus();
    mutex_lock(&text_mutex);
    __jump_label_transform(entry, type, text_poke_smp);
    mutex_unlock(&text_mutex);
    put_online_cpus();
}

__init_or_module void arch_jump_label_transform_static(struct jump_entry *entry,
                      enum jump_label_type type)
{
    __jump_label_transform(entry, type, text_poke_early);
}

#endif