Browse Source
This patch introduces a sample kernel module to demonstrate the use of Hardware Breakpoint feature. It places a breakpoint over the kernel variable 'pid_max' to monitor all write operations and emits a function-backtrace when done. Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>master


4 changed files with 92 additions and 1 deletions
@ -1,3 +1,4 @@
|
||||
# Makefile for Linux samples code
|
||||
|
||||
obj-$(CONFIG_SAMPLES) += markers/ kobject/ kprobes/ tracepoints/ trace_events/
|
||||
obj-$(CONFIG_SAMPLES) += markers/ kobject/ kprobes/ tracepoints/ \
|
||||
trace_events/ hw_breakpoint/
|
||||
|
@ -0,0 +1 @@
|
||||
obj-$(CONFIG_SAMPLE_HW_BREAKPOINT) += data_breakpoint.o
|
@ -0,0 +1,83 @@
|
||||
/*
|
||||
* 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 |
||||
*/ |
||||
#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 <asm/hw_breakpoint.h> |
||||
|
||||
struct hw_breakpoint 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"); |
||||
|
||||
void sample_hbp_handler(struct hw_breakpoint *temp, struct pt_regs |
||||
*temp_regs) |
||||
{ |
||||
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; |
||||
|
||||
#ifdef CONFIG_X86 |
||||
sample_hbp.info.name = ksym_name; |
||||
sample_hbp.info.type = HW_BREAKPOINT_WRITE; |
||||
sample_hbp.info.len = HW_BREAKPOINT_LEN_4; |
||||
#endif /* CONFIG_X86 */ |
||||
|
||||
sample_hbp.triggered = (void *)sample_hbp_handler; |
||||
|
||||
ret = register_kernel_hw_breakpoint(&sample_hbp); |
||||
|
||||
if (ret < 0) { |
||||
printk(KERN_INFO "Breakpoint registration failed\n"); |
||||
return ret; |
||||
} else |
||||
printk(KERN_INFO "HW Breakpoint for %s write installed\n", |
||||
ksym_name); |
||||
|
||||
return 0; |
||||
} |
||||
|
||||
static void __exit hw_break_module_exit(void) |
||||
{ |
||||
unregister_kernel_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"); |
Loading…
Reference in new issue