[net-next-2.6.git] / samples / hw_breakpoint / data_breakpoint.c

/*
 * data_breakpoint.c - Sample HW Breakpoint file to watch kernel data address
 *
 * 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.
 *
 * usage: insmod data_breakpoint.ko ksym=<ksym_name>
 *
 * This file is a kernel module that places a breakpoint over ksym_name kernel
 * variable using Hardware Breakpoint register. The corresponding handler which
 * prints a backtrace is invoked everytime a write operation is performed on
 * that variable.
 *
 * Copyright (C) IBM Corporation, 2009
 *
 * Author: K.Prasad <prasad@linux.vnet.ibm.com>
 */
#include <linux/module.h>	/* Needed by all modules */
#include <linux/kernel.h>	/* Needed for KERN_INFO */
#include <linux/init.h>		/* Needed for the macros */
#include <linux/kallsyms.h>

#include <linux/perf_event.h>
#include <linux/hw_breakpoint.h>

struct perf_event **sample_hbp;

static char ksym_name[KSYM_NAME_LEN] = "pid_max";
module_param_string(ksym, ksym_name, KSYM_NAME_LEN, S_IRUGO);
MODULE_PARM_DESC(ksym, "Kernel symbol to monitor; this module will report any"
			" write operations on the kernel symbol");

static void sample_hbp_handler(struct perf_event *temp, void *data)
{
	printk(KERN_INFO "%s value is changed\n", ksym_name);
	dump_stack();
	printk(KERN_INFO "Dump stack from sample_hbp_handler\n");
}

static int __init hw_break_module_init(void)
{
	int ret;
	unsigned long addr;

	addr = kallsyms_lookup_name(ksym_name);

	sample_hbp = register_wide_hw_breakpoint(addr, HW_BREAKPOINT_LEN_4,
						 HW_BREAKPOINT_W | HW_BREAKPOINT_R,
						 sample_hbp_handler, true);
	if (IS_ERR(sample_hbp)) {
		ret = PTR_ERR(sample_hbp);
		goto fail;
	} else if (!sample_hbp) {
		ret = -EINVAL;
		goto fail;
	}

	printk(KERN_INFO "HW Breakpoint for %s write installed\n", ksym_name);

	return 0;

fail:
	printk(KERN_INFO "Breakpoint registration failed\n");

	return ret;
}

static void __exit hw_break_module_exit(void)
{
	unregister_wide_hw_breakpoint(sample_hbp);
	printk(KERN_INFO "HW Breakpoint for %s write uninstalled\n", ksym_name);
}

module_init(hw_break_module_init);
module_exit(hw_break_module_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("K.Prasad");
MODULE_DESCRIPTION("ksym breakpoint");
Commit	Line	Data
43203993 P	1	/*
	2	* data_breakpoint.c - Sample HW Breakpoint file to watch kernel data address
	3	*
	4	* This program is free software; you can redistribute it and/or modify
	5	* it under the terms of the GNU General Public License as published by
	6	* the Free Software Foundation; either version 2 of the License, or
	7	* (at your option) any later version.
	8	*
	9	* This program is distributed in the hope that it will be useful,
	10	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	11	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	12	* GNU General Public License for more details.
	13	*
	14	* You should have received a copy of the GNU General Public License
	15	* along with this program; if not, write to the Free Software
	16	* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
	17	*
	18	* usage: insmod data_breakpoint.ko ksym=<ksym_name>
	19	*
	20	* This file is a kernel module that places a breakpoint over ksym_name kernel
	21	* variable using Hardware Breakpoint register. The corresponding handler which
	22	* prints a backtrace is invoked everytime a write operation is performed on
	23	* that variable.
	24	*
	25	* Copyright (C) IBM Corporation, 2009
ba6909b7 P	26	*
ba6909b7 P	27	* Author: K.Prasad <prasad@linux.vnet.ibm.com>
43203993 P	28	*/
	29	#include <linux/module.h> /* Needed by all modules */
	30	#include <linux/kernel.h> /* Needed for KERN_INFO */
	31	#include <linux/init.h> /* Needed for the macros */
f60d24d2	32	#include <linux/kallsyms.h>
43203993	33
f60d24d2 FW	34	#include <linux/perf_event.h>
f60d24d2 FW	35	#include <linux/hw_breakpoint.h>
43203993	36
f60d24d2	37	struct perf_event **sample_hbp;
43203993 P	38
	39	static char ksym_name[KSYM_NAME_LEN] = "pid_max";
	40	module_param_string(ksym, ksym_name, KSYM_NAME_LEN, S_IRUGO);
	41	MODULE_PARM_DESC(ksym, "Kernel symbol to monitor; this module will report any"
	42	" write operations on the kernel symbol");
	43
f60d24d2	44	static void sample_hbp_handler(struct perf_event temp, void data)
43203993 P	45	{
	46	printk(KERN_INFO "%s value is changed\n", ksym_name);
	47	dump_stack();
	48	printk(KERN_INFO "Dump stack from sample_hbp_handler\n");
	49	}
	50
	51	static int __init hw_break_module_init(void)
	52	{
	53	int ret;
f60d24d2	54	unsigned long addr;
43203993	55
f60d24d2	56	addr = kallsyms_lookup_name(ksym_name);
43203993	57
f60d24d2 FW	58	sample_hbp = register_wide_hw_breakpoint(addr, HW_BREAKPOINT_LEN_4,
	59	HW_BREAKPOINT_W \| HW_BREAKPOINT_R,
	60	sample_hbp_handler, true);
	61	if (IS_ERR(sample_hbp)) {
	62	ret = PTR_ERR(sample_hbp);
	63	goto fail;
	64	} else if (!sample_hbp) {
	65	ret = -EINVAL;
	66	goto fail;
	67	}
43203993	68
f60d24d2	69	printk(KERN_INFO "HW Breakpoint for %s write installed\n", ksym_name);
43203993 P	70
43203993 P	71	return 0;
f60d24d2 FW	72
	73	fail:
	74	printk(KERN_INFO "Breakpoint registration failed\n");
	75
	76	return ret;
43203993 P	77	}
	78
	79	static void __exit hw_break_module_exit(void)
	80	{
f60d24d2	81	unregister_wide_hw_breakpoint(sample_hbp);
43203993 P	82	printk(KERN_INFO "HW Breakpoint for %s write uninstalled\n", ksym_name);
	83	}
	84
	85	module_init(hw_break_module_init);
	86	module_exit(hw_break_module_exit);
	87
	88	MODULE_LICENSE("GPL");
	89	MODULE_AUTHOR("K.Prasad");
	90	MODULE_DESCRIPTION("ksym breakpoint");