85 lines
2.3 KiB
C
85 lines
2.3 KiB
C
// 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 <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] = "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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#ifdef CONFIG_MODULE_UNLOAD
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__symbol_put(ksym_name);
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#endif
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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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