x86: if we cannot calibrate the TSC, we panic.

[linux-2.6-omap-h63xx.git] / Documentation / kprobes.txt

diff --git a/Documentation/kprobes.txt b/Documentation/kprobes.txt
index 30c101761d0d54f532122e8a804d376de2aa61d8..be89f393274fbd086a4f14b4e56bb82c0a29c76d 100644 (file)
--- a/Documentation/kprobes.txt
+++ b/Documentation/kprobes.txt
@@ -92,9 +92,8 @@ handler has run.  Up to MAX_STACK_SIZE bytes are copied -- e.g.,
 64 bytes on i386.
 
 Note that the probed function's args may be passed on the stack
 64 bytes on i386.
 
 Note that the probed function's args may be passed on the stack

-or in registers (e.g., for x86_64 or for an i386 fastcall function).
-The jprobe will work in either case, so long as the handler's
-prototype matches that of the probed function.
+or in registers.  The jprobe will work in either case, so long as the
+handler's prototype matches that of the probed function.

 
 1.3 Return Probes
 
 
 1.3 Return Probes
 


@@ -193,7 +192,8 @@ code mapping.
 The Kprobes API includes a "register" function and an "unregister"
 function for each type of probe.  Here are terse, mini-man-page
 specifications for these functions and the associated probe handlers
 The Kprobes API includes a "register" function and an "unregister"
 function for each type of probe.  Here are terse, mini-man-page
 specifications for these functions and the associated probe handlers

-that you'll write.  See the latter half of this document for examples.
+that you'll write.  See the files in the samples/kprobes/ sub-directory
+for examples.

 
 4.1 register_kprobe
 
 
 4.1 register_kprobe
 


@@ -270,9 +270,9 @@ Kprobes runs the handler whose address is jp->entry.
 The handler should have the same arg list and return type as the probed
 function; and just before it returns, it must call jprobe_return().
 (The handler never actually returns, since jprobe_return() returns
 The handler should have the same arg list and return type as the probed
 function; and just before it returns, it must call jprobe_return().
 (The handler never actually returns, since jprobe_return() returns

-control to Kprobes.)  If the probed function is declared asmlinkage,
-fastcall, or anything else that affects how args are passed, the
-handler's declaration must match.
+control to Kprobes.)  If the probed function is declared asmlinkage
+or anything else that affects how args are passed, the handler's
+declaration must match.

 
 register_jprobe() returns 0 on success, or a negative errno otherwise.
 
 
 register_jprobe() returns 0 on success, or a negative errno otherwise.
 


@@ -421,249 +421,15 @@ e. Watchpoint probes (which fire on data references).
 
 8. Kprobes Example
 
 
 8. Kprobes Example
 

-Here's a sample kernel module showing the use of kprobes to dump a
-stack trace and selected i386 registers when do_fork() is called.
------ cut here -----
-/*kprobe_example.c*/
-#include <linux/kernel.h>
-#include <linux/module.h>
-#include <linux/kprobes.h>
-#include <linux/sched.h>
-
-/*For each probe you need to allocate a kprobe structure*/
-static struct kprobe kp;
-
-/*kprobe pre_handler: called just before the probed instruction is executed*/
-int handler_pre(struct kprobe *p, struct pt_regs *regs)
-{
-       printk("pre_handler: p->addr=0x%p, eip=%lx, eflags=0x%lx\n",
-               p->addr, regs->eip, regs->eflags);
-       dump_stack();
-       return 0;
-}
-
-/*kprobe post_handler: called after the probed instruction is executed*/
-void handler_post(struct kprobe *p, struct pt_regs *regs, unsigned long flags)
-{
-       printk("post_handler: p->addr=0x%p, eflags=0x%lx\n",
-               p->addr, regs->eflags);
-}
-
-/* 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.
- */
-int handler_fault(struct kprobe *p, struct pt_regs *regs, int trapnr)
-{
-       printk("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;
-       kp.symbol_name = "do_fork";
-
-       ret = register_kprobe(&kp);
-       if (ret < 0) {
-               printk("register_kprobe failed, returned %d\n", ret);
-               return ret;
-       }
-       printk("kprobe registered\n");
-       return 0;
-}
-
-static void __exit kprobe_exit(void)
-{
-       unregister_kprobe(&kp);
-       printk("kprobe unregistered\n");
-}
-
-module_init(kprobe_init)
-module_exit(kprobe_exit)
-MODULE_LICENSE("GPL");
------ cut here -----
-
-You can build the kernel module, kprobe-example.ko, using the following
-Makefile:
------ cut here -----
-obj-m := kprobe-example.o
-KDIR := /lib/modules/$(shell uname -r)/build
-PWD := $(shell pwd)
-default:
-       $(MAKE) -C $(KDIR) SUBDIRS=$(PWD) modules
-clean:
-       rm -f *.mod.c *.ko *.o
------ cut here -----
-
-$ make
-$ su -
-...
-# insmod kprobe-example.ko
-
-You will see the trace data in /var/log/messages and on the console
-whenever do_fork() is invoked to create a new process.
+See samples/kprobes/kprobe_example.c

 
 9. Jprobes Example
 
 
 9. Jprobes Example
 

-Here's a sample kernel module showing the use of jprobes to dump
-the arguments of do_fork().
------ cut here -----
-/*jprobe-example.c */
-#include <linux/kernel.h>
-#include <linux/module.h>
-#include <linux/fs.h>
-#include <linux/uio.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 */
-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("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();
-       /*NOTREACHED*/
-       return 0;
-}
-
-static struct jprobe my_jprobe = {
-       .entry = jdo_fork
-};
-
-static int __init jprobe_init(void)
-{
-       int ret;
-       my_jprobe.kp.symbol_name = "do_fork";
-
-       if ((ret = register_jprobe(&my_jprobe)) <0) {
-               printk("register_jprobe failed, returned %d\n", ret);
-               return -1;
-       }
-       printk("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("jprobe unregistered\n");
-}
-
-module_init(jprobe_init)
-module_exit(jprobe_exit)
-MODULE_LICENSE("GPL");
------ cut here -----
-
-Build and insert the kernel module as shown in the above 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.)
+See samples/kprobes/jprobe_example.c

 
 10. Kretprobes Example
 
 
 10. Kretprobes Example
 

-Here's a sample kernel module showing the use of return probes to
-report failed calls to sys_open().
------ cut here -----
-/*kretprobe-example.c*/
-#include <linux/kernel.h>
-#include <linux/module.h>
-#include <linux/kprobes.h>
-#include <linux/ktime.h>
-
-/* per-instance private data */
-struct my_data {
-       ktime_t entry_stamp;
-};
-
-static const char *probed_func = "sys_open";
-
-/* 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;
-}
-
-/* If the probed function failed, 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 return_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;
-
-       if (retval < 0) {
-               now = ktime_get();
-               delta = ktime_to_ns(ktime_sub(now, data->entry_stamp));
-               printk("%s: return val = %d (duration = %lld ns)\n",
-                      probed_func, retval, delta);
-       }
-       return 0;
-}
-
-static struct kretprobe my_kretprobe = {
-       .handler = return_handler,
-       .entry_handler = entry_handler,
-       .data_size = sizeof(struct my_data),
-       .maxactive = 20, /* probe up to 20 instances concurrently */
-};
-
-static int __init kretprobe_init(void)
-{
-       int ret;
-       my_kretprobe.kp.symbol_name = (char *)probed_func;
-
-       if ((ret = register_kretprobe(&my_kretprobe)) < 0) {
-               printk("register_kretprobe failed, returned %d\n", ret);
-               return -1;
-       }
-       printk("Kretprobe active on %s\n", my_kretprobe.kp.symbol_name);
-       return 0;
-}
-
-static void __exit kretprobe_exit(void)
-{
-       unregister_kretprobe(&my_kretprobe);
-       printk("kretprobe unregistered\n");
-       /* nmissed > 0 suggests that maxactive was set too low. */
-       printk("Missed probing %d instances of %s\n",
-              my_kretprobe.nmissed, probed_func);
-}
-
-module_init(kretprobe_init)
-module_exit(kretprobe_exit)
-MODULE_LICENSE("GPL");
------ cut here -----
-
-Build and insert the kernel module as shown in the above kprobe
-example.  You will see the trace data in /var/log/messages and on the
-console whenever sys_open() returns a negative value.  (Some messages
-may be suppressed if syslogd is configured to eliminate duplicate
-messages.)
+See samples/kprobes/kretprobe_example.c

 
 For additional information on Kprobes, refer to the following URLs:
 http://www-106.ibm.com/developerworks/library/l-kprobes.html?ca=dgr-lnxw42Kprobe
 
 For additional information on Kprobes, refer to the following URLs:
 http://www-106.ibm.com/developerworks/library/l-kprobes.html?ca=dgr-lnxw42Kprobe