1/* 2 * Here's a sample kernel module showing the use of jprobes to dump 3 * the arguments of do_fork(). 4 * 5 * For more information on theory of operation of jprobes, see 6 * Documentation/kprobes.txt 7 * 8 * Build and insert the kernel module as done in the kprobe example. 9 * You will see the trace data in /var/log/messages and on the 10 * console whenever do_fork() is invoked to create a new process. 11 * (Some messages may be suppressed if syslogd is configured to 12 * eliminate duplicate messages.) 13 */ 14 15#include <linux/kernel.h> 16#include <linux/module.h> 17#include <linux/kprobes.h> 18 19/* 20 * Jumper probe for do_fork. 21 * Mirror principle enables access to arguments of the probed routine 22 * from the probe handler. 23 */ 24 25/* Proxy routine having the same arguments as actual do_fork() routine */ 26static long jdo_fork(unsigned long clone_flags, unsigned long stack_start, 27 unsigned long stack_size, int __user *parent_tidptr, 28 int __user *child_tidptr) 29{ 30 pr_info("jprobe: clone_flags = 0x%lx, stack_start = 0x%lx " 31 "stack_size = 0x%lx\n", clone_flags, stack_start, stack_size); 32 33 /* Always end with a call to jprobe_return(). */ 34 jprobe_return(); 35 return 0; 36} 37 38static struct jprobe my_jprobe = { 39 .entry = jdo_fork, 40 .kp = { 41 .symbol_name = "do_fork", 42 }, 43}; 44 45static int __init jprobe_init(void) 46{ 47 int ret; 48 49 ret = register_jprobe(&my_jprobe); 50 if (ret < 0) { 51 printk(KERN_INFO "register_jprobe failed, returned %d\n", ret); 52 return -1; 53 } 54 printk(KERN_INFO "Planted jprobe at %p, handler addr %p\n", 55 my_jprobe.kp.addr, my_jprobe.entry); 56 return 0; 57} 58 59static void __exit jprobe_exit(void) 60{ 61 unregister_jprobe(&my_jprobe); 62 printk(KERN_INFO "jprobe at %p unregistered\n", my_jprobe.kp.addr); 63} 64 65module_init(jprobe_init) 66module_exit(jprobe_exit) 67MODULE_LICENSE("GPL"); 68