kprobes.c

/*
 *  Kernel Probes (KProbes)
 *  kernel/kprobes.c
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * Copyright (C) IBM Corporation, 2002, 2004
 *
 * 2002-Oct	Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
 *		Probes initial implementation (includes suggestions from
 *		Rusty Russell).
 * 2004-Aug	Updated by Prasanna S Panchamukhi <prasanna@in.ibm.com> with
 *		hlists and exceptions notifier as suggested by Andi Kleen.
 * 2004-July	Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
 *		interface to access function arguments.
 * 2004-Sep	Prasanna S Panchamukhi <prasanna@in.ibm.com> Changed Kprobes
 *		exceptions notifier to be first on the priority list.
 */
#include <linux/kprobes.h>
#include <linux/spinlock.h>
#include <linux/hash.h>
#include <linux/init.h>
#include <linux/module.h>
#include <asm/cacheflush.h>
#include <asm/errno.h>
#include <asm/kdebug.h>

#define KPROBE_HASH_BITS 6
#define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS)

static struct hlist_head kprobe_table[KPROBE_TABLE_SIZE];

unsigned int kprobe_cpu = NR_CPUS;
static DEFINE_SPINLOCK(kprobe_lock);

/* Locks kprobe: irqs must be disabled */
void lock_kprobes(void)
{
	spin_lock(&kprobe_lock);
	kprobe_cpu = smp_processor_id();
}

void unlock_kprobes(void)
{
	kprobe_cpu = NR_CPUS;
	spin_unlock(&kprobe_lock);
}

/* You have to be holding the kprobe_lock */
struct kprobe *get_kprobe(void *addr)
{
	struct hlist_head *head;
	struct hlist_node *node;

	head = &kprobe_table[hash_ptr(addr, KPROBE_HASH_BITS)];
	hlist_for_each(node, head) {
		struct kprobe *p = hlist_entry(node, struct kprobe, hlist);
		if (p->addr == addr)
			return p;
	}
	return NULL;
}

int register_kprobe(struct kprobe *p)
{
	int ret = 0;
	unsigned long flags = 0;

	if ((ret = arch_prepare_kprobe(p)) != 0) {
		goto rm_kprobe;
	}
	spin_lock_irqsave(&kprobe_lock, flags);
	INIT_HLIST_NODE(&p->hlist);
	if (get_kprobe(p->addr)) {
		ret = -EEXIST;
		goto out;
	}
	arch_copy_kprobe(p);

	hlist_add_head(&p->hlist,
		       &kprobe_table[hash_ptr(p->addr, KPROBE_HASH_BITS)]);

	p->opcode = *p->addr;
	*p->addr = BREAKPOINT_INSTRUCTION;
	flush_icache_range((unsigned long) p->addr,
			   (unsigned long) p->addr + sizeof(kprobe_opcode_t));
out:
	spin_unlock_irqrestore(&kprobe_lock, flags);
rm_kprobe:
	if (ret == -EEXIST)
		arch_remove_kprobe(p);
	return ret;
}

void unregister_kprobe(struct kprobe *p)
{
	unsigned long flags;
	spin_lock_irqsave(&kprobe_lock, flags);
	if (!get_kprobe(p->addr)) {
		spin_unlock_irqrestore(&kprobe_lock, flags);
		return;
	}
	*p->addr = p->opcode;
	hlist_del(&p->hlist);
	flush_icache_range((unsigned long) p->addr,
			   (unsigned long) p->addr + sizeof(kprobe_opcode_t));
	spin_unlock_irqrestore(&kprobe_lock, flags);
	arch_remove_kprobe(p);
}

static struct notifier_block kprobe_exceptions_nb = {
	.notifier_call = kprobe_exceptions_notify,
	.priority = 0x7fffffff /* we need to notified first */
};

int register_jprobe(struct jprobe *jp)
{
	/* Todo: Verify probepoint is a function entry point */
	jp->kp.pre_handler = setjmp_pre_handler;
	jp->kp.break_handler = longjmp_break_handler;

	return register_kprobe(&jp->kp);
}

void unregister_jprobe(struct jprobe *jp)
{
	unregister_kprobe(&jp->kp);
}

static int __init init_kprobes(void)
{
	int i, err = 0;

	/* FIXME allocate the probe table, currently defined statically */
	/* initialize all list heads */
	for (i = 0; i < KPROBE_TABLE_SIZE; i++)
		INIT_HLIST_HEAD(&kprobe_table[i]);

	err = register_die_notifier(&kprobe_exceptions_nb);
	return err;
}

__initcall(init_kprobes);

EXPORT_SYMBOL_GPL(register_kprobe);
EXPORT_SYMBOL_GPL(unregister_kprobe);
EXPORT_SYMBOL_GPL(register_jprobe);
EXPORT_SYMBOL_GPL(unregister_jprobe);
EXPORT_SYMBOL_GPL(jprobe_return);