91 lines
2.9 KiB
C
91 lines
2.9 KiB
C
/*
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* data_breakpoint.c - Sample HW Breakpoint file to watch kernel data address
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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* usage: insmod data_breakpoint.ko ksym=<ksym_name>
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*
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* This file is a kernel module that places a breakpoint over ksym_name kernel
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* variable using Hardware Breakpoint register. The corresponding handler which
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* prints a backtrace is invoked everytime a write operation is performed on
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* that variable.
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*
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* Copyright (C) IBM Corporation, 2009
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*
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* Author: K.Prasad <prasad@linux.vnet.ibm.com>
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*/
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#include <linux/module.h> /* Needed by all modules */
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#include <linux/kernel.h> /* Needed for KERN_INFO */
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#include <linux/init.h> /* Needed for the macros */
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#include <linux/kallsyms.h>
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#include <linux/perf_event.h>
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#include <linux/hw_breakpoint.h>
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struct perf_event * __percpu *sample_hbp;
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static char ksym_name[KSYM_NAME_LEN] = "pid_max";
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module_param_string(ksym, ksym_name, KSYM_NAME_LEN, S_IRUGO);
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MODULE_PARM_DESC(ksym, "Kernel symbol to monitor; this module will report any"
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" write operations on the kernel symbol");
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static void sample_hbp_handler(struct perf_event *bp, int nmi,
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struct perf_sample_data *data,
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struct pt_regs *regs)
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{
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printk(KERN_INFO "%s value is changed\n", ksym_name);
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dump_stack();
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printk(KERN_INFO "Dump stack from sample_hbp_handler\n");
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}
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static int __init hw_break_module_init(void)
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{
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int ret;
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struct perf_event_attr attr;
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hw_breakpoint_init(&attr);
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attr.bp_addr = kallsyms_lookup_name(ksym_name);
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attr.bp_len = HW_BREAKPOINT_LEN_4;
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attr.bp_type = HW_BREAKPOINT_W | HW_BREAKPOINT_R;
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sample_hbp = register_wide_hw_breakpoint(&attr, sample_hbp_handler);
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if (IS_ERR((void __force *)sample_hbp)) {
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ret = PTR_ERR((void __force *)sample_hbp);
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goto fail;
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}
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printk(KERN_INFO "HW Breakpoint for %s write installed\n", ksym_name);
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return 0;
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fail:
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printk(KERN_INFO "Breakpoint registration failed\n");
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return ret;
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}
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static void __exit hw_break_module_exit(void)
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{
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unregister_wide_hw_breakpoint(sample_hbp);
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printk(KERN_INFO "HW Breakpoint for %s write uninstalled\n", ksym_name);
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}
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module_init(hw_break_module_init);
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module_exit(hw_break_module_exit);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("K.Prasad");
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MODULE_DESCRIPTION("ksym breakpoint");
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