Merge master.kernel.org:/pub/scm/linux/kernel/git/steve/gfs2-2.6-nmw

[pandora-kernel.git] / Documentation / kprobes.txt

diff --git a/Documentation/kprobes.txt b/Documentation/kprobes.txt
index 2c3b1ea..d71faff 100644 (file)
--- a/Documentation/kprobes.txt
+++ b/Documentation/kprobes.txt
@@ -151,9 +151,9 @@ So that you can load and unload Kprobes-based instrumentation modules,
 make sure "Loadable module support" (CONFIG_MODULES) and "Module
 unloading" (CONFIG_MODULE_UNLOAD) are set to "y".
 
 make sure "Loadable module support" (CONFIG_MODULES) and "Module
 unloading" (CONFIG_MODULE_UNLOAD) are set to "y".
 

-You may also want to ensure that CONFIG_KALLSYMS and perhaps even
-CONFIG_KALLSYMS_ALL are set to "y", since kallsyms_lookup_name()
-is a handy, version-independent way to find a function's address.
+Also make sure that CONFIG_KALLSYMS and perhaps even CONFIG_KALLSYMS_ALL
+are set to "y", since kallsyms_lookup_name() is used by the in-kernel
+kprobe address resolution code.

 
 If you need to insert a probe in the middle of a function, you may find
 it useful to "Compile the kernel with debug info" (CONFIG_DEBUG_INFO),
 
 If you need to insert a probe in the middle of a function, you may find
 it useful to "Compile the kernel with debug info" (CONFIG_DEBUG_INFO),


@@ -179,6 +179,27 @@ occurs during execution of kp->pre_handler or kp->post_handler,
 or during single-stepping of the probed instruction, Kprobes calls
 kp->fault_handler.  Any or all handlers can be NULL.
 
 or during single-stepping of the probed instruction, Kprobes calls
 kp->fault_handler.  Any or all handlers can be NULL.
 

+NOTE:
+1. With the introduction of the "symbol_name" field to struct kprobe,
+the probepoint address resolution will now be taken care of by the kernel.
+The following will now work:
+
+       kp.symbol_name = "symbol_name";
+
+(64-bit powerpc intricacies such as function descriptors are handled
+transparently)
+
+2. Use the "offset" field of struct kprobe if the offset into the symbol
+to install a probepoint is known. This field is used to calculate the
+probepoint.
+
+3. Specify either the kprobe "symbol_name" OR the "addr". If both are
+specified, kprobe registration will fail with -EINVAL.
+
+4. With CISC architectures (such as i386 and x86_64), the kprobes code
+does not validate if the kprobe.addr is at an instruction boundary.
+Use "offset" with caution.
+

 register_kprobe() returns 0 on success, or a negative errno otherwise.
 
 User's pre-handler (kp->pre_handler):
 register_kprobe() returns 0 on success, or a negative errno otherwise.
 
 User's pre-handler (kp->pre_handler):


@@ -225,6 +246,12 @@ 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.
 
 fastcall, or anything else that affects how args are passed, the
 handler's declaration must match.
 

+NOTE: A macro JPROBE_ENTRY is provided to handle architecture-specific
+aliasing of jp->entry. In the interest of portability, it is advised
+to use:
+
+       jp->entry = JPROBE_ENTRY(handler);
+

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


@@ -251,6 +278,11 @@ of interest:
 - ret_addr: the return address
 - rp: points to the corresponding kretprobe object
 - task: points to the corresponding task struct
 - ret_addr: the return address
 - rp: points to the corresponding kretprobe object
 - task: points to the corresponding task struct

+
+The regs_return_value(regs) macro provides a simple abstraction to
+extract the return value from the appropriate register as defined by
+the architecture's ABI.
+

 The handler's return value is currently ignored.
 
 4.4 unregister_*probe
 The handler's return value is currently ignored.
 
 4.4 unregister_*probe


@@ -369,7 +401,6 @@ stack trace and selected i386 registers when do_fork() is called.
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/kprobes.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/kprobes.h>

-#include <linux/kallsyms.h>

 #include <linux/sched.h>
 
 /*For each probe you need to allocate a kprobe structure*/
 #include <linux/sched.h>
 
 /*For each probe you need to allocate a kprobe structure*/


@@ -403,32 +434,31 @@ int handler_fault(struct kprobe *p, struct pt_regs *regs, int trapnr)
        return 0;
 }
 
        return 0;
 }
 

-int init_module(void)
+static int __init kprobe_init(void)

 {
        int ret;
        kp.pre_handler = handler_pre;
        kp.post_handler = handler_post;
        kp.fault_handler = handler_fault;
 {
        int ret;
        kp.pre_handler = handler_pre;
        kp.post_handler = handler_post;
        kp.fault_handler = handler_fault;

-       kp.addr = (kprobe_opcode_t*) kallsyms_lookup_name("do_fork");
-       /* register the kprobe now */
-       if (!kp.addr) {
-               printk("Couldn't find %s to plant kprobe\n", "do_fork");
-               return -1;
-       }
-       if ((ret = register_kprobe(&kp) < 0)) {
+       kp.symbol_name = "do_fork";
+
+       ret = register_kprobe(&kp);
+       if (ret < 0) {

                printk("register_kprobe failed, returned %d\n", ret);
                printk("register_kprobe failed, returned %d\n", ret);

-               return -1;
+               return ret;

        }
        printk("kprobe registered\n");
        return 0;
 }
 
        }
        printk("kprobe registered\n");
        return 0;
 }
 

-void cleanup_module(void)
+static void __exit kprobe_exit(void)

 {
        unregister_kprobe(&kp);
        printk("kprobe unregistered\n");
 }
 
 {
        unregister_kprobe(&kp);
        printk("kprobe unregistered\n");
 }
 

+module_init(kprobe_init)
+module_exit(kprobe_exit)

 MODULE_LICENSE("GPL");
 ----- cut here -----
 
 MODULE_LICENSE("GPL");
 ----- cut here -----
 


@@ -463,7 +493,6 @@ the arguments of do_fork().
 #include <linux/fs.h>
 #include <linux/uio.h>
 #include <linux/kprobes.h>
 #include <linux/fs.h>
 #include <linux/uio.h>
 #include <linux/kprobes.h>

-#include <linux/kallsyms.h>

 
 /*
  * Jumper probe for do_fork.
 
 /*
  * Jumper probe for do_fork.


@@ -485,17 +514,13 @@ long jdo_fork(unsigned long clone_flags, unsigned long stack_start,
 }
 
 static struct jprobe my_jprobe = {
 }
 
 static struct jprobe my_jprobe = {

-       .entry = (kprobe_opcode_t *) jdo_fork
+       .entry = JPROBE_ENTRY(jdo_fork)

 };
 
 };
 

-int init_module(void)
+static int __init jprobe_init(void)

 {
        int ret;
 {
        int ret;

-       my_jprobe.kp.addr = (kprobe_opcode_t *) kallsyms_lookup_name("do_fork");
-       if (!my_jprobe.kp.addr) {
-               printk("Couldn't find %s to plant jprobe\n", "do_fork");
-               return -1;
-       }
+       my_jprobe.kp.symbol_name = "do_fork";

 
        if ((ret = register_jprobe(&my_jprobe)) <0) {
                printk("register_jprobe failed, returned %d\n", ret);
 
        if ((ret = register_jprobe(&my_jprobe)) <0) {
                printk("register_jprobe failed, returned %d\n", ret);


@@ -506,12 +531,14 @@ int init_module(void)
        return 0;
 }
 
        return 0;
 }
 

-void cleanup_module(void)
+static void __exit jprobe_exit(void)

 {
        unregister_jprobe(&my_jprobe);
        printk("jprobe unregistered\n");
 }
 
 {
        unregister_jprobe(&my_jprobe);
        printk("jprobe unregistered\n");
 }
 

+module_init(jprobe_init)
+module_exit(jprobe_exit)

 MODULE_LICENSE("GPL");
 ----- cut here -----
 
 MODULE_LICENSE("GPL");
 ----- cut here -----
 


@@ -530,16 +557,13 @@ report failed calls to sys_open().
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/kprobes.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/kprobes.h>

-#include <linux/kallsyms.h>

 
 static const char *probed_func = "sys_open";
 
 /* Return-probe handler: If the probed function fails, log the return value. */
 static int ret_handler(struct kretprobe_instance *ri, struct pt_regs *regs)
 {
 
 static const char *probed_func = "sys_open";
 
 /* Return-probe handler: If the probed function fails, log the return value. */
 static int ret_handler(struct kretprobe_instance *ri, struct pt_regs *regs)
 {

-       // Substitute the appropriate register name for your architecture --
-       // e.g., regs->rax for x86_64, regs->gpr[3] for ppc64.
-       int retval = (int) regs->eax;
+       int retval = regs_return_value(regs);

        if (retval < 0) {
                printk("%s returns %d\n", probed_func, retval);
        }
        if (retval < 0) {
                printk("%s returns %d\n", probed_func, retval);
        }


@@ -552,15 +576,11 @@ static struct kretprobe my_kretprobe = {
        .maxactive = 20
 };
 
        .maxactive = 20
 };
 

-int init_module(void)
+static int __init kretprobe_init(void)

 {
        int ret;
 {
        int ret;

-       my_kretprobe.kp.addr =
-               (kprobe_opcode_t *) kallsyms_lookup_name(probed_func);
-       if (!my_kretprobe.kp.addr) {
-               printk("Couldn't find %s to plant return probe\n", probed_func);
-               return -1;
-       }
+       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;
        if ((ret = register_kretprobe(&my_kretprobe)) < 0) {
                printk("register_kretprobe failed, returned %d\n", ret);
                return -1;


@@ -569,7 +589,7 @@ int init_module(void)
        return 0;
 }
 
        return 0;
 }
 

-void cleanup_module(void)
+static void __exit kretprobe_exit(void)

 {
        unregister_kretprobe(&my_kretprobe);
        printk("kretprobe unregistered\n");
 {
        unregister_kretprobe(&my_kretprobe);
        printk("kretprobe unregistered\n");


@@ -578,6 +598,8 @@ void cleanup_module(void)
                my_kretprobe.nmissed, probed_func);
 }
 
                my_kretprobe.nmissed, probed_func);
 }
 

+module_init(kretprobe_init)
+module_exit(kretprobe_exit)

 MODULE_LICENSE("GPL");
 ----- cut here -----
 
 MODULE_LICENSE("GPL");
 ----- cut here -----
 


@@ -590,3 +612,5 @@ messages.)
 For additional information on Kprobes, refer to the following URLs:
 http://www-106.ibm.com/developerworks/library/l-kprobes.html?ca=dgr-lnxw42Kprobe
 http://www.redhat.com/magazine/005mar05/features/kprobes/
 For additional information on Kprobes, refer to the following URLs:
 http://www-106.ibm.com/developerworks/library/l-kprobes.html?ca=dgr-lnxw42Kprobe
 http://www.redhat.com/magazine/005mar05/features/kprobes/

+http://www-users.cs.umn.edu/~boutcher/kprobes/
+http://www.linuxsymposium.org/2006/linuxsymposium_procv2.pdf (pages 101-115)