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>

1 files changed, 91 insertions, 0 deletions

diff --git a/samples/kprobes/kprobe_example.c b/samples/kprobes/kprobe_example.c
new file mode 100644
index 000000000000..a681998a871c
--- /dev/null
+++ b/samples/kprobes/kprobe_example.c
@@ -0,0 +1,91 @@
+/*
+ * NOTE: This example is works on x86 and powerpc.
+ * Here's a sample kernel module showing the use of kprobes to dump a
+ * stack trace and selected registers when do_fork() is called.
+ *
+ * For more information on theory of operation of kprobes, see
+ * Documentation/kprobes.txt
+ *
+ * You will see the trace data in /var/log/messages and on the console
+ * whenever do_fork() is invoked to create a new process.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/kprobes.h>
+
+/* For each probe you need to allocate a kprobe structure */
+static struct kprobe kp = {
+	.symbol_name	= "do_fork",
+};
+
+/* kprobe pre_handler: called just before the probed instruction is executed */
+static int handler_pre(struct kprobe *p, struct pt_regs *regs)
+{
+#ifdef CONFIG_X86
+	printk(KERN_INFO "pre_handler: p->addr = 0x%p, ip = %lx,"
+			" flags = 0x%lx\n",
+		p->addr, regs->ip, regs->flags);
+#endif
+#ifdef CONFIG_PPC
+	printk(KERN_INFO "pre_handler: p->addr = 0x%p, nip = 0x%lx,"
+			" msr = 0x%lx\n",
+		p->addr, regs->nip, regs->msr);
+#endif
+
+	/* A dump_stack() here will give a stack backtrace */
+	return 0;
+}
+
+/* kprobe post_handler: called after the probed instruction is executed */
+static void handler_post(struct kprobe *p, struct pt_regs *regs,
+				unsigned long flags)
+{
+#ifdef CONFIG_X86
+	printk(KERN_INFO "post_handler: p->addr = 0x%p, flags = 0x%lx\n",
+		p->addr, regs->flags);
+#endif
+#ifdef CONFIG_PPC
+	printk(KERN_INFO "post_handler: p->addr = 0x%p, msr = 0x%lx\n",
+		p->addr, regs->msr);
+#endif
+}
+
+/*
+ * 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.
+ */
+static int handler_fault(struct kprobe *p, struct pt_regs *regs, int trapnr)
+{
+	printk(KERN_INFO "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;
+
+	ret = register_kprobe(&kp);
+	if (ret < 0) {
+		printk(KERN_INFO "register_kprobe failed, returned %d\n", ret);
+		return ret;
+	}
+	printk(KERN_INFO "Planted kprobe at %p\n", kp.addr);
+	return 0;
+}
+
+static void __exit kprobe_exit(void)
+{
+	unregister_kprobe(&kp);
+	printk(KERN_INFO "kprobe at %p unregistered\n", kp.addr);
+}
+
+module_init(kprobe_init)
+module_exit(kprobe_exit)
+MODULE_LICENSE("GPL");