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-rw-r--r--samples/kprobes/jprobe_example.c68
1 files changed, 68 insertions, 0 deletions
diff --git a/samples/kprobes/jprobe_example.c b/samples/kprobes/jprobe_example.c
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+/*
+ * 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,
+ struct pt_regs *regs, unsigned long stack_size,
+ int __user *parent_tidptr, int __user *child_tidptr)
+{
+ printk(KERN_INFO "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();
+ 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");