git://bbs.cooldavid.org / net-next-2.6.git / blame
| 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 | |
| 26 | */ | |
| 27 | #include <linux/module.h> /* Needed by all modules */ | |
| 28 | #include <linux/kernel.h> /* Needed for KERN_INFO */ | |
| 29 | #include <linux/init.h> /* Needed for the macros */ | |
| 30 | ||
| 31 | #include <asm/hw_breakpoint.h> | |
| 32 | ||
| 33 | struct hw_breakpoint sample_hbp; | |
| 34 | ||
| 35 | static char ksym_name[KSYM_NAME_LEN] = "pid_max"; | |
| 36 | module_param_string(ksym, ksym_name, KSYM_NAME_LEN, S_IRUGO); | |
| 37 | MODULE_PARM_DESC(ksym, "Kernel symbol to monitor; this module will report any" | |
| 38 | " write operations on the kernel symbol"); | |
| 39 | ||
| 40 | void sample_hbp_handler(struct hw_breakpoint *temp, struct pt_regs | |
| 41 | *temp_regs) | |
| 42 | { | |
| 43 | printk(KERN_INFO "%s value is changed\n", ksym_name); | |
| 44 | dump_stack(); | |
| 45 | printk(KERN_INFO "Dump stack from sample_hbp_handler\n"); | |
| 46 | } | |
| 47 | ||
| 48 | static int __init hw_break_module_init(void) | |
| 49 | { | |
| 50 | int ret; | |
| 51 | ||
| 52 | #ifdef CONFIG_X86 | |
| 53 | sample_hbp.info.name = ksym_name; | |
| 54 | sample_hbp.info.type = HW_BREAKPOINT_WRITE; | |
| 55 | sample_hbp.info.len = HW_BREAKPOINT_LEN_4; | |
| 56 | #endif /* CONFIG_X86 */ | |
| 57 | ||
| 58 | sample_hbp.triggered = (void *)sample_hbp_handler; | |
| 59 | ||
| 60 | ret = register_kernel_hw_breakpoint(&sample_hbp); | |
| 61 | ||
| 62 | if (ret < 0) { | |
| 63 | printk(KERN_INFO "Breakpoint registration failed\n"); | |
| 64 | return ret; | |
| 65 | } else | |
| 66 | printk(KERN_INFO "HW Breakpoint for %s write installed\n", | |
| 67 | ksym_name); | |
| 68 | ||
| 69 | return 0; | |
| 70 | } | |
| 71 | ||
| 72 | static void __exit hw_break_module_exit(void) | |
| 73 | { | |
| 74 | unregister_kernel_hw_breakpoint(&sample_hbp); | |
| 75 | printk(KERN_INFO "HW Breakpoint for %s write uninstalled\n", ksym_name); | |
| 76 | } | |
| 77 | ||
| 78 | module_init(hw_break_module_init); | |
| 79 | module_exit(hw_break_module_exit); | |
| 80 | ||
| 81 | MODULE_LICENSE("GPL"); | |
| 82 | MODULE_AUTHOR("K.Prasad"); | |
| 83 | MODULE_DESCRIPTION("ksym breakpoint"); |