From 804defea1c020d5c52985685e56986f1a399acde Mon Sep 17 00:00:00 2001 From: Ananth N Mavinakayanahalli Date: Tue, 4 Mar 2008 14:28:38 -0800 Subject: 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=' to determine execution time of func_name in nanoseconds. Signed-off-by: Randy Dunlap Signed-off-by: Ananth N Mavinakayanahalli Acked-by: Mathieu Desnoyers Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- samples/kprobes/kretprobe_example.c | 106 ++++++++++++++++++++++++++++++++++++ 1 file changed, 106 insertions(+) create mode 100644 samples/kprobes/kretprobe_example.c (limited to 'samples/kprobes/kretprobe_example.c') diff --git a/samples/kprobes/kretprobe_example.c b/samples/kprobes/kretprobe_example.c new file mode 100644 index 000000000000..4e764b317d61 --- /dev/null +++ b/samples/kprobes/kretprobe_example.c @@ -0,0 +1,106 @@ +/* + * kretprobe_example.c + * + * Here's a sample kernel module showing the use of return probes to + * report the return value and total time taken for probed function + * to run. + * + * usage: insmod kretprobe_example.ko func= + * + * If no func_name is specified, do_fork is instrumented + * + * For more information on theory of operation of kretprobes, 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 the probed function returns. (Some messages may be suppressed + * if syslogd is configured to eliminate duplicate messages.) + */ + +#include +#include +#include +#include +#include + +static char func_name[NAME_MAX] = "do_fork"; +module_param_string(func, func_name, NAME_MAX, S_IRUGO); +MODULE_PARM_DESC(func, "Function to kretprobe; this module will report the" + " function's execution time"); + +/* per-instance private data */ +struct my_data { + ktime_t entry_stamp; +}; + +/* Here we use the entry_hanlder to 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; +} + +/* + * Return-probe handler: 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 ret_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; + + now = ktime_get(); + delta = ktime_to_ns(ktime_sub(now, data->entry_stamp)); + printk(KERN_INFO "%s returned %d and took %lld ns to execute\n", + func_name, retval, (long long)delta); + return 0; +} + +static struct kretprobe my_kretprobe = { + .handler = ret_handler, + .entry_handler = entry_handler, + .data_size = sizeof(struct my_data), + /* Probe up to 20 instances concurrently. */ + .maxactive = 20, +}; + +static int __init kretprobe_init(void) +{ + int ret; + + my_kretprobe.kp.symbol_name = func_name; + ret = register_kretprobe(&my_kretprobe); + if (ret < 0) { + printk(KERN_INFO "register_kretprobe failed, returned %d\n", + ret); + return -1; + } + printk(KERN_INFO "Planted return probe at %s: %p\n", + my_kretprobe.kp.symbol_name, my_kretprobe.kp.addr); + return 0; +} + +static void __exit kretprobe_exit(void) +{ + unregister_kretprobe(&my_kretprobe); + printk(KERN_INFO "kretprobe at %p unregistered\n", + my_kretprobe.kp.addr); + + /* nmissed > 0 suggests that maxactive was set too low. */ + printk(KERN_INFO "Missed probing %d instances of %s\n", + my_kretprobe.nmissed, my_kretprobe.kp.symbol_name); +} + +module_init(kretprobe_init) +module_exit(kretprobe_exit) +MODULE_LICENSE("GPL"); -- cgit v1.2.3