cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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fprobe_example.c (3977B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/*
      3 * Here's a sample kernel module showing the use of fprobe to dump a
      4 * stack trace and selected registers when kernel_clone() is called.
      5 *
      6 * For more information on theory of operation of kprobes, see
      7 * Documentation/trace/kprobes.rst
      8 *
      9 * You will see the trace data in /var/log/messages and on the console
     10 * whenever kernel_clone() is invoked to create a new process.
     11 */
     12
     13#define pr_fmt(fmt) "%s: " fmt, __func__
     14
     15#include <linux/kernel.h>
     16#include <linux/module.h>
     17#include <linux/fprobe.h>
     18#include <linux/sched/debug.h>
     19#include <linux/slab.h>
     20
     21#define BACKTRACE_DEPTH 16
     22#define MAX_SYMBOL_LEN 4096
     23struct fprobe sample_probe;
     24static unsigned long nhit;
     25
     26static char symbol[MAX_SYMBOL_LEN] = "kernel_clone";
     27module_param_string(symbol, symbol, sizeof(symbol), 0644);
     28MODULE_PARM_DESC(symbol, "Probed symbol(s), given by comma separated symbols or a wildcard pattern.");
     29
     30static char nosymbol[MAX_SYMBOL_LEN] = "";
     31module_param_string(nosymbol, nosymbol, sizeof(nosymbol), 0644);
     32MODULE_PARM_DESC(nosymbol, "Not-probed symbols, given by a wildcard pattern.");
     33
     34static bool stackdump = true;
     35module_param(stackdump, bool, 0644);
     36MODULE_PARM_DESC(stackdump, "Enable stackdump.");
     37
     38static bool use_trace = false;
     39module_param(use_trace, bool, 0644);
     40MODULE_PARM_DESC(use_trace, "Use trace_printk instead of printk. This is only for debugging.");
     41
     42static void show_backtrace(void)
     43{
     44	unsigned long stacks[BACKTRACE_DEPTH];
     45	unsigned int len;
     46
     47	len = stack_trace_save(stacks, BACKTRACE_DEPTH, 2);
     48	stack_trace_print(stacks, len, 24);
     49}
     50
     51static void sample_entry_handler(struct fprobe *fp, unsigned long ip, struct pt_regs *regs)
     52{
     53	if (use_trace)
     54		/*
     55		 * This is just an example, no kernel code should call
     56		 * trace_printk() except when actively debugging.
     57		 */
     58		trace_printk("Enter <%pS> ip = 0x%p\n", (void *)ip, (void *)ip);
     59	else
     60		pr_info("Enter <%pS> ip = 0x%p\n", (void *)ip, (void *)ip);
     61	nhit++;
     62	if (stackdump)
     63		show_backtrace();
     64}
     65
     66static void sample_exit_handler(struct fprobe *fp, unsigned long ip, struct pt_regs *regs)
     67{
     68	unsigned long rip = instruction_pointer(regs);
     69
     70	if (use_trace)
     71		/*
     72		 * This is just an example, no kernel code should call
     73		 * trace_printk() except when actively debugging.
     74		 */
     75		trace_printk("Return from <%pS> ip = 0x%p to rip = 0x%p (%pS)\n",
     76			(void *)ip, (void *)ip, (void *)rip, (void *)rip);
     77	else
     78		pr_info("Return from <%pS> ip = 0x%p to rip = 0x%p (%pS)\n",
     79			(void *)ip, (void *)ip, (void *)rip, (void *)rip);
     80	nhit++;
     81	if (stackdump)
     82		show_backtrace();
     83}
     84
     85static int __init fprobe_init(void)
     86{
     87	char *p, *symbuf = NULL;
     88	const char **syms;
     89	int ret, count, i;
     90
     91	sample_probe.entry_handler = sample_entry_handler;
     92	sample_probe.exit_handler = sample_exit_handler;
     93
     94	if (strchr(symbol, '*')) {
     95		/* filter based fprobe */
     96		ret = register_fprobe(&sample_probe, symbol,
     97				      nosymbol[0] == '\0' ? NULL : nosymbol);
     98		goto out;
     99	} else if (!strchr(symbol, ',')) {
    100		symbuf = symbol;
    101		ret = register_fprobe_syms(&sample_probe, (const char **)&symbuf, 1);
    102		goto out;
    103	}
    104
    105	/* Comma separated symbols */
    106	symbuf = kstrdup(symbol, GFP_KERNEL);
    107	if (!symbuf)
    108		return -ENOMEM;
    109	p = symbuf;
    110	count = 1;
    111	while ((p = strchr(++p, ',')) != NULL)
    112		count++;
    113
    114	pr_info("%d symbols found\n", count);
    115
    116	syms = kcalloc(count, sizeof(char *), GFP_KERNEL);
    117	if (!syms) {
    118		kfree(symbuf);
    119		return -ENOMEM;
    120	}
    121
    122	p = symbuf;
    123	for (i = 0; i < count; i++)
    124		syms[i] = strsep(&p, ",");
    125
    126	ret = register_fprobe_syms(&sample_probe, syms, count);
    127	kfree(syms);
    128	kfree(symbuf);
    129out:
    130	if (ret < 0)
    131		pr_err("register_fprobe failed, returned %d\n", ret);
    132	else
    133		pr_info("Planted fprobe at %s\n", symbol);
    134
    135	return ret;
    136}
    137
    138static void __exit fprobe_exit(void)
    139{
    140	unregister_fprobe(&sample_probe);
    141
    142	pr_info("fprobe at %s unregistered. %ld times hit, %ld times missed\n",
    143		symbol, nhit, sample_probe.nmissed);
    144}
    145
    146module_init(fprobe_init)
    147module_exit(fprobe_exit)
    148MODULE_LICENSE("GPL");