jump_label.c

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/*
 * Jump label s390 support
 *
 * Copyright IBM Corp. 2011
 * Author(s): Jan Glauber <[email protected]>
 */
#include <linux/module.h>
#include <linux/uaccess.h>
#include <linux/stop_machine.h>
#include <linux/jump_label.h>
#include <asm/ipl.h>

#ifdef HAVE_JUMP_LABEL

struct insn {
    u16 opcode;
    s32 offset;
} __packed;

struct insn_args {
    struct jump_entry *entry;
    enum jump_label_type type;
};

static void __jump_label_transform(struct jump_entry *entry,
                   enum jump_label_type type)
{
    struct insn insn;
    int rc;

    if (type == JUMP_LABEL_ENABLE) {
        /* brcl 15,offset */
        insn.opcode = 0xc0f4;
        insn.offset = (entry->target - entry->code) >> 1;
    } else {
        /* brcl 0,0 */
        insn.opcode = 0xc004;
        insn.offset = 0;
    }

    rc = probe_kernel_write((void *)entry->code, &insn, JUMP_LABEL_NOP_SIZE);
    WARN_ON_ONCE(rc < 0);
}

static int __sm_arch_jump_label_transform(void *data)
{
    struct insn_args *args = data;

    __jump_label_transform(args->entry, args->type);
    return 0;
}

void arch_jump_label_transform(struct jump_entry *entry,
                   enum jump_label_type type)
{
    struct insn_args args;

    args.entry = entry;
    args.type = type;

    stop_machine(__sm_arch_jump_label_transform, &args, NULL);
}

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

#endif