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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 /samples/kprobes/kprobe_example.c
parent9edddaa200df18e08fe0cf21036e8ae467b1363c (diff)
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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 'samples/kprobes/kprobe_example.c')
-rw-r--r--samples/kprobes/kprobe_example.c91
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 00000000000..a681998a871
--- /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");