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authorAnanth N Mavinakayanahalli <ananth@in.ibm.com>2008-03-04 14:28:38 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-03-04 16:35:11 -0800
commit804defea1c020d5c52985685e56986f1a399acde (patch)
treedd91b81d272522ec8e5e482408734dd290fed152 /Documentation
parent9edddaa200df18e08fe0cf21036e8ae467b1363c (diff)
downloadlinux-804defea1c020d5c52985685e56986f1a399acde.tar.gz
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>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/kprobes.txt243
1 files changed, 5 insertions, 238 deletions
diff --git a/Documentation/kprobes.txt b/Documentation/kprobes.txt
index 83f515c2905..be89f393274 100644
--- a/Documentation/kprobes.txt
+++ b/Documentation/kprobes.txt
@@ -192,7 +192,8 @@ code mapping.
The Kprobes API includes a "register" function and an "unregister"
function for each type of probe. Here are terse, mini-man-page
specifications for these functions and the associated probe handlers
-that you'll write. See the latter half of this document for examples.
+that you'll write. See the files in the samples/kprobes/ sub-directory
+for examples.
4.1 register_kprobe
@@ -420,249 +421,15 @@ e. Watchpoint probes (which fire on data references).
8. Kprobes Example
-Here's a sample kernel module showing the use of kprobes to dump a
-stack trace and selected i386 registers when do_fork() is called.
------ cut here -----
-/*kprobe_example.c*/
-#include <linux/kernel.h>
-#include <linux/module.h>
-#include <linux/kprobes.h>
-#include <linux/sched.h>
-
-/*For each probe you need to allocate a kprobe structure*/
-static struct kprobe kp;
-
-/*kprobe pre_handler: called just before the probed instruction is executed*/
-int handler_pre(struct kprobe *p, struct pt_regs *regs)
-{
- printk("pre_handler: p->addr=0x%p, eip=%lx, eflags=0x%lx\n",
- p->addr, regs->eip, regs->eflags);
- dump_stack();
- return 0;
-}
-
-/*kprobe post_handler: called after the probed instruction is executed*/
-void handler_post(struct kprobe *p, struct pt_regs *regs, unsigned long flags)
-{
- printk("post_handler: p->addr=0x%p, eflags=0x%lx\n",
- p->addr, regs->eflags);
-}
-
-/* fault_handler: this is called if an exception is generated for any
- * instruction within the pre- or post-handler, or when Kprobes
- * single-steps the probed instruction.
- */
-int handler_fault(struct kprobe *p, struct pt_regs *regs, int trapnr)
-{
- printk("fault_handler: p->addr=0x%p, trap #%dn",
- p->addr, trapnr);
- /* Return 0 because we don't handle the fault. */
- return 0;
-}
-
-static int __init kprobe_init(void)
-{
- int ret;
- kp.pre_handler = handler_pre;
- kp.post_handler = handler_post;
- kp.fault_handler = handler_fault;
- kp.symbol_name = "do_fork";
-
- ret = register_kprobe(&kp);
- if (ret < 0) {
- printk("register_kprobe failed, returned %d\n", ret);
- return ret;
- }
- printk("kprobe registered\n");
- return 0;
-}
-
-static void __exit kprobe_exit(void)
-{
- unregister_kprobe(&kp);
- printk("kprobe unregistered\n");
-}
-
-module_init(kprobe_init)
-module_exit(kprobe_exit)
-MODULE_LICENSE("GPL");
------ cut here -----
-
-You can build the kernel module, kprobe-example.ko, using the following
-Makefile:
------ cut here -----
-obj-m := kprobe-example.o
-KDIR := /lib/modules/$(shell uname -r)/build
-PWD := $(shell pwd)
-default:
- $(MAKE) -C $(KDIR) SUBDIRS=$(PWD) modules
-clean:
- rm -f *.mod.c *.ko *.o
------ cut here -----
-
-$ make
-$ su -
-...
-# insmod kprobe-example.ko
-
-You will see the trace data in /var/log/messages and on the console
-whenever do_fork() is invoked to create a new process.
+See samples/kprobes/kprobe_example.c
9. Jprobes Example
-Here's a sample kernel module showing the use of jprobes to dump
-the arguments of do_fork().
------ cut here -----
-/*jprobe-example.c */
-#include <linux/kernel.h>
-#include <linux/module.h>
-#include <linux/fs.h>
-#include <linux/uio.h>
-#include <linux/kprobes.h>
-
-/*
- * Jumper probe for do_fork.
- * Mirror principle enables access to arguments of the probed routine
- * from the probe handler.
- */
-
-/* Proxy routine having the same arguments as actual do_fork() routine */
-long jdo_fork(unsigned long clone_flags, unsigned long stack_start,
- struct pt_regs *regs, unsigned long stack_size,
- int __user * parent_tidptr, int __user * child_tidptr)
-{
- printk("jprobe: clone_flags=0x%lx, stack_size=0x%lx, regs=0x%p\n",
- clone_flags, stack_size, regs);
- /* Always end with a call to jprobe_return(). */
- jprobe_return();
- /*NOTREACHED*/
- return 0;
-}
-
-static struct jprobe my_jprobe = {
- .entry = jdo_fork
-};
-
-static int __init jprobe_init(void)
-{
- int ret;
- my_jprobe.kp.symbol_name = "do_fork";
-
- if ((ret = register_jprobe(&my_jprobe)) <0) {
- printk("register_jprobe failed, returned %d\n", ret);
- return -1;
- }
- printk("Planted jprobe at %p, handler addr %p\n",
- my_jprobe.kp.addr, my_jprobe.entry);
- return 0;
-}
-
-static void __exit jprobe_exit(void)
-{
- unregister_jprobe(&my_jprobe);
- printk("jprobe unregistered\n");
-}
-
-module_init(jprobe_init)
-module_exit(jprobe_exit)
-MODULE_LICENSE("GPL");
------ cut here -----
-
-Build and insert the kernel module as shown in the above kprobe
-example. You will see the trace data in /var/log/messages and on
-the console whenever do_fork() is invoked to create a new process.
-(Some messages may be suppressed if syslogd is configured to
-eliminate duplicate messages.)
+See samples/kprobes/jprobe_example.c
10. Kretprobes Example
-Here's a sample kernel module showing the use of return probes to
-report failed calls to sys_open().
------ cut here -----
-/*kretprobe-example.c*/
-#include <linux/kernel.h>
-#include <linux/module.h>
-#include <linux/kprobes.h>
-#include <linux/ktime.h>
-
-/* per-instance private data */
-struct my_data {
- ktime_t entry_stamp;
-};
-
-static const char *probed_func = "sys_open";
-
-/* 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;
-}
-
-/* If the probed function failed, 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 return_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;
-
- if (retval < 0) {
- now = ktime_get();
- delta = ktime_to_ns(ktime_sub(now, data->entry_stamp));
- printk("%s: return val = %d (duration = %lld ns)\n",
- probed_func, retval, delta);
- }
- return 0;
-}
-
-static struct kretprobe my_kretprobe = {
- .handler = return_handler,
- .entry_handler = entry_handler,
- .data_size = sizeof(struct my_data),
- .maxactive = 20, /* probe up to 20 instances concurrently */
-};
-
-static int __init kretprobe_init(void)
-{
- int ret;
- my_kretprobe.kp.symbol_name = (char *)probed_func;
-
- if ((ret = register_kretprobe(&my_kretprobe)) < 0) {
- printk("register_kretprobe failed, returned %d\n", ret);
- return -1;
- }
- printk("Kretprobe active on %s\n", my_kretprobe.kp.symbol_name);
- return 0;
-}
-
-static void __exit kretprobe_exit(void)
-{
- unregister_kretprobe(&my_kretprobe);
- printk("kretprobe unregistered\n");
- /* nmissed > 0 suggests that maxactive was set too low. */
- printk("Missed probing %d instances of %s\n",
- my_kretprobe.nmissed, probed_func);
-}
-
-module_init(kretprobe_init)
-module_exit(kretprobe_exit)
-MODULE_LICENSE("GPL");
------ cut here -----
-
-Build and insert the kernel module as shown in the above kprobe
-example. You will see the trace data in /var/log/messages and on the
-console whenever sys_open() returns a negative value. (Some messages
-may be suppressed if syslogd is configured to eliminate duplicate
-messages.)
+See samples/kprobes/kretprobe_example.c
For additional information on Kprobes, refer to the following URLs:
http://www-106.ibm.com/developerworks/library/l-kprobes.html?ca=dgr-lnxw42Kprobe