cregit-Linux how code gets into the kernel

Release 4.16 samples/hw_breakpoint/data_breakpoint.c

/*
 * 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"); }

Contributors

PersonTokensPropCommitsCommitProp
K.Prasad2771.05%133.33%
Frédéric Weisbecker1128.95%266.67%
Total38100.00%3100.00%


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; }

Contributors

PersonTokensPropCommitsCommitProp
Frédéric Weisbecker5752.78%350.00%
K.Prasad3936.11%116.67%
Tejun Heo109.26%116.67%
Avi Kivity21.85%116.67%
Total108100.00%6100.00%


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); }

Contributors

PersonTokensPropCommitsCommitProp
K.Prasad2195.45%150.00%
Frédéric Weisbecker14.55%150.00%
Total22100.00%2100.00%

module_init(hw_break_module_init); module_exit(hw_break_module_exit); MODULE_LICENSE("GPL"); MODULE_AUTHOR("K.Prasad"); MODULE_DESCRIPTION("ksym breakpoint");

Overall Contributors

PersonTokensPropCommitsCommitProp
K.Prasad15762.80%114.29%
Frédéric Weisbecker7931.60%342.86%
Tejun Heo114.40%114.29%
Avi Kivity20.80%114.29%
Lucas De Marchi10.40%114.29%
Peter Zijlstra0.00%00.00%
Total250100.00%7100.00%
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