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82 lines
2.3 KiB
82 lines
2.3 KiB
// SPDX-License-Identifier: GPL-2.0-or-later |
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/* |
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* data_breakpoint.c - Sample HW Breakpoint file to watch kernel data address |
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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 every time 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 <[email protected]> |
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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] = "jiffies"; |
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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, |
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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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void *addr = __symbol_get(ksym_name); |
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if (!addr) |
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return -ENXIO; |
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hw_breakpoint_init(&attr); |
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attr.bp_addr = (unsigned long)addr; |
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attr.bp_len = HW_BREAKPOINT_LEN_4; |
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attr.bp_type = HW_BREAKPOINT_W; |
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sample_hbp = register_wide_hw_breakpoint(&attr, sample_hbp_handler, NULL); |
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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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symbol_put(ksym_name); |
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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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