diff options
Diffstat (limited to 'samples/hw_breakpoint')
| -rw-r--r-- | samples/hw_breakpoint/Makefile | 1 | ||||
| -rw-r--r-- | samples/hw_breakpoint/data_breakpoint.c | 90 |
2 files changed, 91 insertions, 0 deletions
diff --git a/samples/hw_breakpoint/Makefile b/samples/hw_breakpoint/Makefile new file mode 100644 index 00000000..0f5c31c2 --- /dev/null +++ b/samples/hw_breakpoint/Makefile @@ -0,0 +1 @@ +obj-$(CONFIG_SAMPLE_HW_BREAKPOINT) += data_breakpoint.o diff --git a/samples/hw_breakpoint/data_breakpoint.c b/samples/hw_breakpoint/data_breakpoint.c new file mode 100644 index 00000000..ef7f3229 --- /dev/null +++ b/samples/hw_breakpoint/data_breakpoint.c @@ -0,0 +1,90 @@ +/* + * 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 every time 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 * __percpu *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 *bp, + struct perf_sample_data *data, + struct pt_regs *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; + struct perf_event_attr attr; + + hw_breakpoint_init(&attr); + attr.bp_addr = kallsyms_lookup_name(ksym_name); + attr.bp_len = HW_BREAKPOINT_LEN_4; + attr.bp_type = HW_BREAKPOINT_W | HW_BREAKPOINT_R; + + sample_hbp = register_wide_hw_breakpoint(&attr, sample_hbp_handler, NULL); + if (IS_ERR((void __force *)sample_hbp)) { + ret = PTR_ERR((void __force *)sample_hbp); + 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"); |