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Kernel breakpoints are created using functions in which we pass breakpoint parameters as individual variables: address, length and type. Although it fits well for x86, this just does not scale across architectures that may support this api later as these may have more or different needs. Pass in a perf_event_attr structure instead because it is meant to evolve as much as possible into a generic hardware breakpoint parameter structure. Reported-by: K.Prasad <prasad@linux.vnet.ibm.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> LKML-Reference: <1259294154-5197-2-git-send-regression-fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
88 lines
2.7 KiB
C
88 lines
2.7 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 **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 *temp, void *data)
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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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DEFINE_BREAKPOINT_ATTR(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(sample_hbp)) {
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ret = PTR_ERR(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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