cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
Log | Files | Refs | README | LICENSE | sfeed.txt

data_breakpoint.c (2321B)

      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
     24struct perf_event * __percpu *sample_hbp;
     25
     26static char ksym_name[KSYM_NAME_LEN] = "jiffies";
     27module_param_string(ksym, ksym_name, KSYM_NAME_LEN, S_IRUGO);
     28MODULE_PARM_DESC(ksym, "Kernel symbol to monitor; this module will report any"
     29			" write operations on the kernel symbol");
     30
     31static 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
     40static 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((void __force *)sample_hbp)) {
     56		ret = PTR_ERR((void __force *)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
     64fail:
     65	printk(KERN_INFO "Breakpoint registration failed\n");
     66
     67	return ret;
     68}
     69
     70static void __exit hw_break_module_exit(void)
     71{
     72	unregister_wide_hw_breakpoint(sample_hbp);
     73	symbol_put(ksym_name);
     74	printk(KERN_INFO "HW Breakpoint for %s write uninstalled\n", ksym_name);
     75}
     76
     77module_init(hw_break_module_init);
     78module_exit(hw_break_module_exit);
     79
     80MODULE_LICENSE("GPL");
     81MODULE_AUTHOR("K.Prasad");
     82MODULE_DESCRIPTION("ksym breakpoint");