| | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
| | 2 | /* |
| | 3 | * data_breakpoint.c - Sample HW Breakpoint file to watch kernel data address |
| | 4 | * |
| | 5 | * usage: insmod data_breakpoint.ko ksym=<ksym_name> |
| | 6 | * |
| | 7 | * This file is a kernel module that places a breakpoint over ksym_name kernel |
| | 8 | * variable using Hardware Breakpoint register. The corresponding handler which |
| | 9 | * prints a backtrace is invoked every time a write operation is performed on |
| | 10 | * that variable. |
| | 11 | * |
| | 12 | * Copyright (C) IBM Corporation, 2009 |
| | 13 | * |
| | 14 | * Author: K.Prasad <prasad@linux.vnet.ibm.com> |
| | 15 | */ |
| | 16 | #include <linux/module.h> /* Needed by all modules */ |
| | 17 | #include <linux/kernel.h> /* Needed for KERN_INFO */ |
| | 18 | #include <linux/init.h> /* Needed for the macros */ |
| | 19 | #include <linux/kallsyms.h> |
| | 20 | |
| | 21 | #include <linux/perf_event.h> |
| | 22 | #include <linux/hw_breakpoint.h> |
| | 23 | |
| | 24 | static struct perf_event * __percpu *sample_hbp; |
| | 25 | |
| | 26 | static char ksym_name[KSYM_NAME_LEN] = "jiffies"; |
| | 27 | module_param_string(ksym, ksym_name, KSYM_NAME_LEN, S_IRUGO); |
| | 28 | MODULE_PARM_DESC(ksym, "Kernel symbol to monitor; this module will report any" |
| | 29 | " write operations on the kernel symbol"); |
| | 30 | |
| | 31 | static void sample_hbp_handler(struct perf_event *bp, |
| | 32 | struct perf_sample_data *data, |
| | 33 | struct pt_regs *regs) |
| | 34 | { |
| | 35 | printk(KERN_INFO "%s value is changed\n", ksym_name); |
| | 36 | dump_stack(); |
| | 37 | printk(KERN_INFO "Dump stack from sample_hbp_handler\n"); |
| | 38 | } |
| | 39 | |
| | 40 | static int __init hw_break_module_init(void) |
| | 41 | { |
| | 42 | int ret; |
| | 43 | struct perf_event_attr attr; |
| | 44 | void *addr = __symbol_get(ksym_name); |
| | 45 | |
| | 46 | if (!addr) |
| | 47 | return -ENXIO; |
| | 48 | |
| | 49 | hw_breakpoint_init(&attr); |
| | 50 | attr.bp_addr = (unsigned long)addr; |
| | 51 | attr.bp_len = HW_BREAKPOINT_LEN_4; |
| | 52 | attr.bp_type = HW_BREAKPOINT_W; |
| | 53 | |
| | 54 | sample_hbp = register_wide_hw_breakpoint(&attr, sample_hbp_handler, NULL); |
| | 55 | if (IS_ERR_PCPU(sample_hbp)) { |
| | 56 | ret = PTR_ERR_PCPU(sample_hbp); |
| | 57 | goto fail; |
| | 58 | } |
| | 59 | |
| | 60 | printk(KERN_INFO "HW Breakpoint for %s write installed\n", ksym_name); |
| | 61 | |
| | 62 | return 0; |
| | 63 | |
| | 64 | fail: |
| | 65 | printk(KERN_INFO "Breakpoint registration failed\n"); |
| | 66 | |
| | 67 | return ret; |
| | 68 | } |
| | 69 | |
| | 70 | static void __exit hw_break_module_exit(void) |
| | 71 | { |
| | 72 | unregister_wide_hw_breakpoint(sample_hbp); |
| | 73 | #ifdef CONFIG_MODULE_UNLOAD |
| | 74 | __symbol_put(ksym_name); |
| | 75 | #endif |
| | 76 | printk(KERN_INFO "HW Breakpoint for %s write uninstalled\n", ksym_name); |
| | 77 | } |
| | 78 | |
| | 79 | module_init(hw_break_module_init); |
| | 80 | module_exit(hw_break_module_exit); |
| | 81 | |
| | 82 | MODULE_LICENSE("GPL"); |
| | 83 | MODULE_AUTHOR("K.Prasad"); |
| | 84 | MODULE_DESCRIPTION("ksym breakpoint"); |
projects / linux-2.6-block.git / blame_incremental