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git.proxmox.com Git - mirror_ubuntu-bionic-kernel.git/blob - samples/hw_breakpoint/data_breakpoint.c
2 * data_breakpoint.c - Sample HW Breakpoint file to watch kernel data address
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.
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.
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.
18 * usage: insmod data_breakpoint.ko ksym=<ksym_name>
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
25 * Copyright (C) IBM Corporation, 2009
27 * Author: K.Prasad <prasad@linux.vnet.ibm.com>
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 */
32 #include <linux/kallsyms.h>
34 #include <linux/perf_event.h>
35 #include <linux/hw_breakpoint.h>
37 struct perf_event
* __percpu
*sample_hbp
;
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");
44 static void sample_hbp_handler(struct perf_event
*bp
, int nmi
,
45 struct perf_sample_data
*data
,
48 printk(KERN_INFO
"%s value is changed\n", ksym_name
);
50 printk(KERN_INFO
"Dump stack from sample_hbp_handler\n");
53 static int __init
hw_break_module_init(void)
56 struct perf_event_attr attr
;
58 hw_breakpoint_init(&attr
);
59 attr
.bp_addr
= kallsyms_lookup_name(ksym_name
);
60 attr
.bp_len
= HW_BREAKPOINT_LEN_4
;
61 attr
.bp_type
= HW_BREAKPOINT_W
| HW_BREAKPOINT_R
;
63 sample_hbp
= register_wide_hw_breakpoint(&attr
, sample_hbp_handler
);
64 if (IS_ERR((void __force
*)sample_hbp
)) {
65 ret
= PTR_ERR((void __force
*)sample_hbp
);
69 printk(KERN_INFO
"HW Breakpoint for %s write installed\n", ksym_name
);
74 printk(KERN_INFO
"Breakpoint registration failed\n");
79 static void __exit
hw_break_module_exit(void)
81 unregister_wide_hw_breakpoint(sample_hbp
);
82 printk(KERN_INFO
"HW Breakpoint for %s write uninstalled\n", ksym_name
);
85 module_init(hw_break_module_init
);
86 module_exit(hw_break_module_exit
);
88 MODULE_LICENSE("GPL");
89 MODULE_AUTHOR("K.Prasad");
90 MODULE_DESCRIPTION("ksym breakpoint");