From 57f0f512b273f60d52568b8c6b77e17f5636edc0 Mon Sep 17 00:00:00 2001
From: André Fabian Silva Delgado <emulatorman@parabola.nu>
Date: Wed, 5 Aug 2015 17:04:01 -0300
Subject: Initial import

---
 samples/kprobes/jprobe_example.c | 67 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)
 create mode 100644 samples/kprobes/jprobe_example.c

(limited to 'samples/kprobes/jprobe_example.c')

diff --git a/samples/kprobes/jprobe_example.c b/samples/kprobes/jprobe_example.c
new file mode 100644
index 000000000..9119ac6a8
--- /dev/null
+++ b/samples/kprobes/jprobe_example.c
@@ -0,0 +1,67 @@
+/*
+ * Here's a sample kernel module showing the use of jprobes to dump
+ * the arguments of do_fork().
+ *
+ * For more information on theory of operation of jprobes, 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 do_fork() is invoked to create a new process.
+ * (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>
+
+/*
+ * 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 */
+static long jdo_fork(unsigned long clone_flags, unsigned long stack_start,
+	      unsigned long stack_size, int __user *parent_tidptr,
+	      int __user *child_tidptr)
+{
+	pr_info("jprobe: clone_flags = 0x%lx, stack_start = 0x%lx "
+		"stack_size = 0x%lx\n", clone_flags, stack_start, stack_size);
+
+	/* Always end with a call to jprobe_return(). */
+	jprobe_return();
+	return 0;
+}
+
+static struct jprobe my_jprobe = {
+	.entry			= jdo_fork,
+	.kp = {
+		.symbol_name	= "do_fork",
+	},
+};
+
+static int __init jprobe_init(void)
+{
+	int ret;
+
+	ret = register_jprobe(&my_jprobe);
+	if (ret < 0) {
+		printk(KERN_INFO "register_jprobe failed, returned %d\n", ret);
+		return -1;
+	}
+	printk(KERN_INFO "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(KERN_INFO "jprobe at %p unregistered\n", my_jprobe.kp.addr);
+}
+
+module_init(jprobe_init)
+module_exit(jprobe_exit)
+MODULE_LICENSE("GPL");
-- 
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