K.Prasad | 4320399 | 2009-06-01 23:46:20 +0530 | [diff] [blame] | 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 |
K.Prasad | ba6909b | 2009-11-23 21:17:13 +0530 | [diff] [blame] | 26 | * |
| 27 | * Author: K.Prasad <prasad@linux.vnet.ibm.com> |
K.Prasad | 4320399 | 2009-06-01 23:46:20 +0530 | [diff] [blame] | 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 */ |
Frederic Weisbecker | f60d24d | 2009-11-10 10:17:07 +0100 | [diff] [blame] | 32 | #include <linux/kallsyms.h> |
K.Prasad | 4320399 | 2009-06-01 23:46:20 +0530 | [diff] [blame] | 33 | |
Frederic Weisbecker | f60d24d | 2009-11-10 10:17:07 +0100 | [diff] [blame] | 34 | #include <linux/perf_event.h> |
| 35 | #include <linux/hw_breakpoint.h> |
K.Prasad | 4320399 | 2009-06-01 23:46:20 +0530 | [diff] [blame] | 36 | |
Frederic Weisbecker | f60d24d | 2009-11-10 10:17:07 +0100 | [diff] [blame] | 37 | struct perf_event **sample_hbp; |
K.Prasad | 4320399 | 2009-06-01 23:46:20 +0530 | [diff] [blame] | 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 | |
Frederic Weisbecker | f60d24d | 2009-11-10 10:17:07 +0100 | [diff] [blame] | 44 | static void sample_hbp_handler(struct perf_event *temp, void *data) |
K.Prasad | 4320399 | 2009-06-01 23:46:20 +0530 | [diff] [blame] | 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; |
Frederic Weisbecker | dd1853c | 2009-11-27 04:55:54 +0100 | [diff] [blame^] | 54 | DEFINE_BREAKPOINT_ATTR(attr); |
K.Prasad | 4320399 | 2009-06-01 23:46:20 +0530 | [diff] [blame] | 55 | |
Frederic Weisbecker | dd1853c | 2009-11-27 04:55:54 +0100 | [diff] [blame^] | 56 | attr.bp_addr = kallsyms_lookup_name(ksym_name); |
| 57 | attr.bp_len = HW_BREAKPOINT_LEN_4; |
| 58 | attr.bp_type = HW_BREAKPOINT_W | HW_BREAKPOINT_R; |
K.Prasad | 4320399 | 2009-06-01 23:46:20 +0530 | [diff] [blame] | 59 | |
Frederic Weisbecker | dd1853c | 2009-11-27 04:55:54 +0100 | [diff] [blame^] | 60 | sample_hbp = register_wide_hw_breakpoint(&attr, sample_hbp_handler); |
Frederic Weisbecker | f60d24d | 2009-11-10 10:17:07 +0100 | [diff] [blame] | 61 | if (IS_ERR(sample_hbp)) { |
| 62 | ret = PTR_ERR(sample_hbp); |
| 63 | goto fail; |
Frederic Weisbecker | f60d24d | 2009-11-10 10:17:07 +0100 | [diff] [blame] | 64 | } |
K.Prasad | 4320399 | 2009-06-01 23:46:20 +0530 | [diff] [blame] | 65 | |
Frederic Weisbecker | f60d24d | 2009-11-10 10:17:07 +0100 | [diff] [blame] | 66 | printk(KERN_INFO "HW Breakpoint for %s write installed\n", ksym_name); |
K.Prasad | 4320399 | 2009-06-01 23:46:20 +0530 | [diff] [blame] | 67 | |
| 68 | return 0; |
Frederic Weisbecker | f60d24d | 2009-11-10 10:17:07 +0100 | [diff] [blame] | 69 | |
| 70 | fail: |
| 71 | printk(KERN_INFO "Breakpoint registration failed\n"); |
| 72 | |
| 73 | return ret; |
K.Prasad | 4320399 | 2009-06-01 23:46:20 +0530 | [diff] [blame] | 74 | } |
| 75 | |
| 76 | static void __exit hw_break_module_exit(void) |
| 77 | { |
Frederic Weisbecker | f60d24d | 2009-11-10 10:17:07 +0100 | [diff] [blame] | 78 | unregister_wide_hw_breakpoint(sample_hbp); |
K.Prasad | 4320399 | 2009-06-01 23:46:20 +0530 | [diff] [blame] | 79 | printk(KERN_INFO "HW Breakpoint for %s write uninstalled\n", ksym_name); |
| 80 | } |
| 81 | |
| 82 | module_init(hw_break_module_init); |
| 83 | module_exit(hw_break_module_exit); |
| 84 | |
| 85 | MODULE_LICENSE("GPL"); |
| 86 | MODULE_AUTHOR("K.Prasad"); |
| 87 | MODULE_DESCRIPTION("ksym breakpoint"); |