Kprobes: move kprobe examples to samples/
Move kprobes examples from Documentation/kprobes.txt to under samples/. Patch originally by Randy Dunlap. o Updated the patch to apply on 2.6.25-rc3 o Modified examples code to build on multiple architectures. Currently, the kprobe and jprobe examples code works for x86 and powerpc o Cleaned up unneeded #includes o Cleaned up Kconfig per Sam Ravnborg's suggestions to fix build break on archs that don't have kretprobes o Implemented suggestions by Mathieu Desnoyers on CONFIG_KRETPROBES o Included Andrew Morton's cleanup based on x86-git o Modified kretprobe_example to act as a arch-agnostic module to determine routine execution times: Use 'modprobe kretprobe_example func=<func_name>' to determine execution time of func_name in nanoseconds. Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com> Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Acked-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>wifi-calibration
Ananth N Mavinakayanahalli
Linus Torvalds
parent
9edddaa200
commit
804defea1c
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@ -192,7 +192,8 @@ code mapping.
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The Kprobes API includes a "register" function and an "unregister"
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function for each type of probe. Here are terse, mini-man-page
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specifications for these functions and the associated probe handlers
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that you'll write. See the latter half of this document for examples.
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that you'll write. See the files in the samples/kprobes/ sub-directory
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for examples.
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4.1 register_kprobe
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@ -420,249 +421,15 @@ e. Watchpoint probes (which fire on data references).
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8. Kprobes Example
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Here's a sample kernel module showing the use of kprobes to dump a
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stack trace and selected i386 registers when do_fork() is called.
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----- cut here -----
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/*kprobe_example.c*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/kprobes.h>
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#include <linux/sched.h>
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/*For each probe you need to allocate a kprobe structure*/
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static struct kprobe kp;
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/*kprobe pre_handler: called just before the probed instruction is executed*/
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int handler_pre(struct kprobe *p, struct pt_regs *regs)
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{
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printk("pre_handler: p->addr=0x%p, eip=%lx, eflags=0x%lx\n",
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p->addr, regs->eip, regs->eflags);
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dump_stack();
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return 0;
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}
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/*kprobe post_handler: called after the probed instruction is executed*/
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void handler_post(struct kprobe *p, struct pt_regs *regs, unsigned long flags)
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{
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printk("post_handler: p->addr=0x%p, eflags=0x%lx\n",
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p->addr, regs->eflags);
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}
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/* fault_handler: this is called if an exception is generated for any
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* instruction within the pre- or post-handler, or when Kprobes
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* single-steps the probed instruction.
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*/
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int handler_fault(struct kprobe *p, struct pt_regs *regs, int trapnr)
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{
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printk("fault_handler: p->addr=0x%p, trap #%dn",
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p->addr, trapnr);
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/* Return 0 because we don't handle the fault. */
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return 0;
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}
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static int __init kprobe_init(void)
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{
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int ret;
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kp.pre_handler = handler_pre;
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kp.post_handler = handler_post;
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kp.fault_handler = handler_fault;
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kp.symbol_name = "do_fork";
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ret = register_kprobe(&kp);
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if (ret < 0) {
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printk("register_kprobe failed, returned %d\n", ret);
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return ret;
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}
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printk("kprobe registered\n");
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return 0;
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}
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static void __exit kprobe_exit(void)
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{
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unregister_kprobe(&kp);
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printk("kprobe unregistered\n");
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}
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module_init(kprobe_init)
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module_exit(kprobe_exit)
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MODULE_LICENSE("GPL");
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----- cut here -----
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You can build the kernel module, kprobe-example.ko, using the following
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Makefile:
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----- cut here -----
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obj-m := kprobe-example.o
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KDIR := /lib/modules/$(shell uname -r)/build
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PWD := $(shell pwd)
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default:
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$(MAKE) -C $(KDIR) SUBDIRS=$(PWD) modules
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clean:
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rm -f *.mod.c *.ko *.o
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----- cut here -----
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$ make
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$ su -
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...
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# insmod kprobe-example.ko
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You will see the trace data in /var/log/messages and on the console
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whenever do_fork() is invoked to create a new process.
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See samples/kprobes/kprobe_example.c
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9. Jprobes Example
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Here's a sample kernel module showing the use of jprobes to dump
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the arguments of do_fork().
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----- cut here -----
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/*jprobe-example.c */
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/fs.h>
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#include <linux/uio.h>
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#include <linux/kprobes.h>
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/*
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* Jumper probe for do_fork.
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* Mirror principle enables access to arguments of the probed routine
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* from the probe handler.
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*/
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/* Proxy routine having the same arguments as actual do_fork() routine */
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long jdo_fork(unsigned long clone_flags, unsigned long stack_start,
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struct pt_regs *regs, unsigned long stack_size,
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int __user * parent_tidptr, int __user * child_tidptr)
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{
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printk("jprobe: clone_flags=0x%lx, stack_size=0x%lx, regs=0x%p\n",
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clone_flags, stack_size, regs);
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/* Always end with a call to jprobe_return(). */
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jprobe_return();
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/*NOTREACHED*/
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return 0;
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}
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static struct jprobe my_jprobe = {
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.entry = jdo_fork
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};
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static int __init jprobe_init(void)
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{
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int ret;
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my_jprobe.kp.symbol_name = "do_fork";
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if ((ret = register_jprobe(&my_jprobe)) <0) {
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printk("register_jprobe failed, returned %d\n", ret);
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return -1;
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}
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printk("Planted jprobe at %p, handler addr %p\n",
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my_jprobe.kp.addr, my_jprobe.entry);
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return 0;
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}
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static void __exit jprobe_exit(void)
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{
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unregister_jprobe(&my_jprobe);
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printk("jprobe unregistered\n");
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}
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module_init(jprobe_init)
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module_exit(jprobe_exit)
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MODULE_LICENSE("GPL");
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----- cut here -----
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Build and insert the kernel module as shown in the above kprobe
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example. You will see the trace data in /var/log/messages and on
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the console whenever do_fork() is invoked to create a new process.
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(Some messages may be suppressed if syslogd is configured to
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eliminate duplicate messages.)
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See samples/kprobes/jprobe_example.c
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10. Kretprobes Example
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Here's a sample kernel module showing the use of return probes to
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report failed calls to sys_open().
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----- cut here -----
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/*kretprobe-example.c*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/kprobes.h>
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#include <linux/ktime.h>
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/* per-instance private data */
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struct my_data {
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ktime_t entry_stamp;
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};
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static const char *probed_func = "sys_open";
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/* Timestamp function entry. */
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static int entry_handler(struct kretprobe_instance *ri, struct pt_regs *regs)
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{
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struct my_data *data;
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if(!current->mm)
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return 1; /* skip kernel threads */
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data = (struct my_data *)ri->data;
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data->entry_stamp = ktime_get();
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return 0;
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}
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/* If the probed function failed, log the return value and duration.
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* Duration may turn out to be zero consistently, depending upon the
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* granularity of time accounting on the platform. */
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static int return_handler(struct kretprobe_instance *ri, struct pt_regs *regs)
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{
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int retval = regs_return_value(regs);
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struct my_data *data = (struct my_data *)ri->data;
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s64 delta;
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ktime_t now;
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if (retval < 0) {
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now = ktime_get();
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delta = ktime_to_ns(ktime_sub(now, data->entry_stamp));
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printk("%s: return val = %d (duration = %lld ns)\n",
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probed_func, retval, delta);
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}
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return 0;
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}
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static struct kretprobe my_kretprobe = {
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.handler = return_handler,
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.entry_handler = entry_handler,
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.data_size = sizeof(struct my_data),
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.maxactive = 20, /* probe up to 20 instances concurrently */
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};
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static int __init kretprobe_init(void)
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{
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int ret;
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my_kretprobe.kp.symbol_name = (char *)probed_func;
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if ((ret = register_kretprobe(&my_kretprobe)) < 0) {
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printk("register_kretprobe failed, returned %d\n", ret);
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return -1;
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}
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printk("Kretprobe active on %s\n", my_kretprobe.kp.symbol_name);
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return 0;
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}
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static void __exit kretprobe_exit(void)
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{
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unregister_kretprobe(&my_kretprobe);
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printk("kretprobe unregistered\n");
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/* nmissed > 0 suggests that maxactive was set too low. */
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printk("Missed probing %d instances of %s\n",
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my_kretprobe.nmissed, probed_func);
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}
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module_init(kretprobe_init)
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module_exit(kretprobe_exit)
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MODULE_LICENSE("GPL");
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----- cut here -----
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Build and insert the kernel module as shown in the above kprobe
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example. You will see the trace data in /var/log/messages and on the
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console whenever sys_open() returns a negative value. (Some messages
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may be suppressed if syslogd is configured to eliminate duplicate
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messages.)
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See samples/kprobes/kretprobe_example.c
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For additional information on Kprobes, refer to the following URLs:
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http://www-106.ibm.com/developerworks/library/l-kprobes.html?ca=dgr-lnxw42Kprobe
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@ -22,5 +22,16 @@ config SAMPLE_KOBJECT
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If in doubt, say "N" here.
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config SAMPLE_KPROBES
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tristate "Build kprobes examples -- loadable modules only"
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depends on KPROBES && m
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help
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This build several kprobes example modules.
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config SAMPLE_KRETPROBES
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tristate "Build kretprobes example -- loadable modules only"
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default m
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depends on SAMPLE_KPROBES && KRETPROBES
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endif # SAMPLES
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@ -1,3 +1,3 @@
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# Makefile for Linux samples code
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obj-$(CONFIG_SAMPLES) += markers/ kobject/
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obj-$(CONFIG_SAMPLES) += markers/ kobject/ kprobes/
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@ -0,0 +1,5 @@
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# builds the kprobes example kernel modules;
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# then to use one (as root): insmod <module_name.ko>
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obj-$(CONFIG_SAMPLE_KPROBES) += kprobe_example.o jprobe_example.o
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obj-$(CONFIG_SAMPLE_KRETPROBES) += kretprobe_example.o
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@ -0,0 +1,68 @@
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/*
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* Here's a sample kernel module showing the use of jprobes to dump
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* the arguments of do_fork().
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*
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* For more information on theory of operation of jprobes, see
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* Documentation/kprobes.txt
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*
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* Build and insert the kernel module as done in the kprobe example.
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* You will see the trace data in /var/log/messages and on the
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* console whenever do_fork() is invoked to create a new process.
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* (Some messages may be suppressed if syslogd is configured to
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* eliminate duplicate messages.)
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/kprobes.h>
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/*
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* Jumper probe for do_fork.
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* Mirror principle enables access to arguments of the probed routine
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* from the probe handler.
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*/
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/* Proxy routine having the same arguments as actual do_fork() routine */
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static long jdo_fork(unsigned long clone_flags, unsigned long stack_start,
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struct pt_regs *regs, unsigned long stack_size,
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int __user *parent_tidptr, int __user *child_tidptr)
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{
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printk(KERN_INFO "jprobe: clone_flags = 0x%lx, stack_size = 0x%lx,"
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" regs = 0x%p\n",
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clone_flags, stack_size, regs);
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/* Always end with a call to jprobe_return(). */
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jprobe_return();
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return 0;
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}
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static struct jprobe my_jprobe = {
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.entry = jdo_fork,
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.kp = {
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.symbol_name = "do_fork",
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},
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};
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static int __init jprobe_init(void)
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{
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int ret;
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ret = register_jprobe(&my_jprobe);
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if (ret < 0) {
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printk(KERN_INFO "register_jprobe failed, returned %d\n", ret);
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return -1;
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}
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printk(KERN_INFO "Planted jprobe at %p, handler addr %p\n",
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my_jprobe.kp.addr, my_jprobe.entry);
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return 0;
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}
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static void __exit jprobe_exit(void)
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{
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unregister_jprobe(&my_jprobe);
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printk(KERN_INFO "jprobe at %p unregistered\n", my_jprobe.kp.addr);
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}
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module_init(jprobe_init)
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module_exit(jprobe_exit)
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MODULE_LICENSE("GPL");
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@ -0,0 +1,91 @@
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/*
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* NOTE: This example is works on x86 and powerpc.
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* Here's a sample kernel module showing the use of kprobes to dump a
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* stack trace and selected registers when do_fork() is called.
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*
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* For more information on theory of operation of kprobes, see
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* Documentation/kprobes.txt
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*
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* You will see the trace data in /var/log/messages and on the console
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* whenever do_fork() is invoked to create a new process.
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/kprobes.h>
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/* For each probe you need to allocate a kprobe structure */
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static struct kprobe kp = {
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.symbol_name = "do_fork",
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};
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/* kprobe pre_handler: called just before the probed instruction is executed */
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static int handler_pre(struct kprobe *p, struct pt_regs *regs)
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{
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#ifdef CONFIG_X86
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printk(KERN_INFO "pre_handler: p->addr = 0x%p, ip = %lx,"
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" flags = 0x%lx\n",
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p->addr, regs->ip, regs->flags);
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#endif
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#ifdef CONFIG_PPC
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printk(KERN_INFO "pre_handler: p->addr = 0x%p, nip = 0x%lx,"
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" msr = 0x%lx\n",
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p->addr, regs->nip, regs->msr);
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#endif
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/* A dump_stack() here will give a stack backtrace */
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return 0;
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}
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/* kprobe post_handler: called after the probed instruction is executed */
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static void handler_post(struct kprobe *p, struct pt_regs *regs,
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unsigned long flags)
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{
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#ifdef CONFIG_X86
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printk(KERN_INFO "post_handler: p->addr = 0x%p, flags = 0x%lx\n",
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p->addr, regs->flags);
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#endif
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#ifdef CONFIG_PPC
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printk(KERN_INFO "post_handler: p->addr = 0x%p, msr = 0x%lx\n",
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p->addr, regs->msr);
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#endif
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}
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/*
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* fault_handler: this is called if an exception is generated for any
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* instruction within the pre- or post-handler, or when Kprobes
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* single-steps the probed instruction.
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*/
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static int handler_fault(struct kprobe *p, struct pt_regs *regs, int trapnr)
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{
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printk(KERN_INFO "fault_handler: p->addr = 0x%p, trap #%dn",
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p->addr, trapnr);
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/* Return 0 because we don't handle the fault. */
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return 0;
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}
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static int __init kprobe_init(void)
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{
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int ret;
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kp.pre_handler = handler_pre;
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kp.post_handler = handler_post;
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kp.fault_handler = handler_fault;
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ret = register_kprobe(&kp);
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if (ret < 0) {
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printk(KERN_INFO "register_kprobe failed, returned %d\n", ret);
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return ret;
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}
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printk(KERN_INFO "Planted kprobe at %p\n", kp.addr);
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return 0;
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}
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static void __exit kprobe_exit(void)
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{
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unregister_kprobe(&kp);
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printk(KERN_INFO "kprobe at %p unregistered\n", kp.addr);
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}
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module_init(kprobe_init)
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module_exit(kprobe_exit)
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MODULE_LICENSE("GPL");
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@ -0,0 +1,106 @@
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/*
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* kretprobe_example.c
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*
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* Here's a sample kernel module showing the use of return probes to
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* report the return value and total time taken for probed function
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* to run.
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*
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* usage: insmod kretprobe_example.ko func=<func_name>
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*
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* If no func_name is specified, do_fork is instrumented
|
||||
*
|
||||
* For more information on theory of operation of kretprobes, see
|
||||
* Documentation/kprobes.txt
|
||||
*
|
||||
* Build and insert the kernel module as done in the kprobe example.
|
||||
* You will see the trace data in /var/log/messages and on the console
|
||||
* whenever the probed function returns. (Some messages may be suppressed
|
||||
* if syslogd is configured to eliminate duplicate messages.)
|
||||
*/
|
||||
|
||||
#include <linux/kernel.h>
|
||||
#include <linux/module.h>
|
||||
#include <linux/kprobes.h>
|
||||
#include <linux/ktime.h>
|
||||
#include <linux/limits.h>
|
||||
|
||||
static char func_name[NAME_MAX] = "do_fork";
|
||||
module_param_string(func, func_name, NAME_MAX, S_IRUGO);
|
||||
MODULE_PARM_DESC(func, "Function to kretprobe; this module will report the"
|
||||
" function's execution time");
|
||||
|
||||
/* per-instance private data */
|
||||
struct my_data {
|
||||
ktime_t entry_stamp;
|
||||
};
|
||||
|
||||
/* Here we use the entry_hanlder to timestamp function entry */
|
||||
static int entry_handler(struct kretprobe_instance *ri, struct pt_regs *regs)
|
||||
{
|
||||
struct my_data *data;
|
||||
|
||||
if (!current->mm)
|
||||
return 1; /* Skip kernel threads */
|
||||
|
||||
data = (struct my_data *)ri->data;
|
||||
data->entry_stamp = ktime_get();
|
||||
return 0;
|
||||
}
|
||||
|
||||
/*
|
||||
* Return-probe handler: Log the return value and duration. Duration may turn
|
||||
* out to be zero consistently, depending upon the granularity of time
|
||||
* accounting on the platform.
|
||||
*/
|
||||
static int ret_handler(struct kretprobe_instance *ri, struct pt_regs *regs)
|
||||
{
|
||||
int retval = regs_return_value(regs);
|
||||
struct my_data *data = (struct my_data *)ri->data;
|
||||
s64 delta;
|
||||
ktime_t now;
|
||||
|
||||
now = ktime_get();
|
||||
delta = ktime_to_ns(ktime_sub(now, data->entry_stamp));
|
||||
printk(KERN_INFO "%s returned %d and took %lld ns to execute\n",
|
||||
func_name, retval, (long long)delta);
|
||||
return 0;
|
||||
}
|
||||
|
||||
static struct kretprobe my_kretprobe = {
|
||||
.handler = ret_handler,
|
||||
.entry_handler = entry_handler,
|
||||
.data_size = sizeof(struct my_data),
|
||||
/* Probe up to 20 instances concurrently. */
|
||||
.maxactive = 20,
|
||||
};
|
||||
|
||||
static int __init kretprobe_init(void)
|
||||
{
|
||||
int ret;
|
||||
|
||||
my_kretprobe.kp.symbol_name = func_name;
|
||||
ret = register_kretprobe(&my_kretprobe);
|
||||
if (ret < 0) {
|
||||
printk(KERN_INFO "register_kretprobe failed, returned %d\n",
|
||||
ret);
|
||||
return -1;
|
||||
}
|
||||
printk(KERN_INFO "Planted return probe at %s: %p\n",
|
||||
my_kretprobe.kp.symbol_name, my_kretprobe.kp.addr);
|
||||
return 0;
|
||||
}
|
||||
|
||||
static void __exit kretprobe_exit(void)
|
||||
{
|
||||
unregister_kretprobe(&my_kretprobe);
|
||||
printk(KERN_INFO "kretprobe at %p unregistered\n",
|
||||
my_kretprobe.kp.addr);
|
||||
|
||||
/* nmissed > 0 suggests that maxactive was set too low. */
|
||||
printk(KERN_INFO "Missed probing %d instances of %s\n",
|
||||
my_kretprobe.nmissed, my_kretprobe.kp.symbol_name);
|
||||
}
|
||||
|
||||
module_init(kretprobe_init)
|
||||
module_exit(kretprobe_exit)
|
||||
MODULE_LICENSE("GPL");
|
||||
Loading…
Reference in New Issue