lkml.org 
[lkml]   [2007]   [Sep]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [PATCH/RFC] samples/: move kprobes sources to samples
On Tue, Sep 25, 2007 at 09:57:11AM +0100, Christoph Hellwig wrote:
> On Tue, Sep 25, 2007 at 02:13:33PM +0530, Ananth N Mavinakayanahalli wrote:
> > +++ linux-2.6.23-rc7/samples/kprobes/jprobe_example.c
> > @@ -0,0 +1,69 @@
> > +/*jprobe-example.c */
>
> I don't think we should have this type of comment in any of the files.
>
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/fs.h>
> > +#include <linux/uio.h>
>
> I don't think you'll need uio,h here.

Fixed. Actually, we don't need the fs.h either... I've audited and
cleaned up the other examples also.

> > + * Jumper probe for do_fork.
> > + * Mirror principle enables access to arguments of the probed routine
> > + * from the probe handler.
> > + */
> > +static const char *probed_func = "do_fork";
> > +
>
> > + /* Always end with a call to jprobe_return(). */
> > + jprobe_return();
> > +
> > + /*NOTREACHED*/
> > + return 0;
>
> I'd rather write this as:
>
> /* Always end with a call to jprobe_return(). */
> jprobe_return();
> return 0;
> }

Fixed

> Also a a note not to these example but general kprobes code I've
> bee wondering whether jprobe_return() should just include the return.
> Yes, macros including a return are ugly, but in this case jprobe_return
> actually handles the return anyway through deep magic.

Right; but the issue here is that in jprobe_return() we don't know what
the jprobed function would return. Also, we've left this the way it
is just so the compiler is happy. (And jprobe_return() is a function
with each arch doing its own magic :-))

> > +static struct jprobe my_jprobe = {
> > + .entry = jdo_fork
> > +};
> > +
> > +static int __init jprobe_init(void)
> > +{
> > + int ret;
> > + my_jprobe.kp.symbol_name = (char *)probed_func;
>
> Shouldn't this be simply done in the static initialization, ala:
>
> static struct jprobe my_jprobe = {
> .entry = jdo_fork,
> .kp = {
> .symbol_name = "do_fork",
> },
> };
>
> (same for the other examples)

Agreed. Fixed.

> > +static int handler_pre(struct kprobe *p, struct pt_regs *regs)
> > +{
> > +#ifdef CONFIG_X86_32
> > + printk("pre_handler: p->addr = 0x%p, eip = %lx, eflags = 0x%lx\n",
> > + p->addr, regs->eip, regs->eflags);
> > +#endif
> > +#ifdef CONFIG_X86_64
> > + printk("pre_handler: p->addr = 0x%p, rip = %lx, eflags = 0x%lx\n",
> > + p->addr, regs->rip, regs->eflags);
> > +#endif
> > +#ifdef CONFIG_PPC
> > + printk("pre_handler: p->addr = 0x%p, nip = 0x%lx, msr = 0x%lx\n",
> > + p->addr, regs->nip, regs->msr);
> > +#endif
>
> Now this is really ugly. We should really have macros for the interesting
> registers (instruction pointer, frame pointer, stack pointer) in kdebug.h.
> systemtap runtime already has them for supported architectures, any care
> to port them over?
>
> (note that this is not an objection to the patch as-is, but rather a
> suggestion for later improvement of the whole thing)

Agreed

> Thanks a lot for moving this in the right place!

Updated patch...

Thanks Randy for kicking this off. I've updated kprobe_example.c to work
on powerpc also. In addition I have:

o Removed samples/Kbuild so the build goes on fine
o Modified examples slightly to display output better (cosmetic)
o Changed the kretprobe_example.c to probe do_fork and log the new pid
o Fixed code per roel's nitpicks
o Renamed kretprobe-example.c to kretprobe_example.c for consistancy
o Made changes suggested by Christoph
o Cleaned up unneeded #includes


Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
---
Documentation/kprobes.txt | 214 ------------------------------------
samples/Kbuild | 2
samples/Kconfig | 5
samples/Makefile | 3
samples/kprobes/Makefile | 5
samples/kprobes/jprobe_example.c | 64 ++++++++++
samples/kprobes/kprobe_example.c | 89 ++++++++++++++
samples/kprobes/kretprobe_example.c | 59 +++++++++
8 files changed, 230 insertions(+), 211 deletions(-)
Index: linux-2.6.23-rc7/samples/kprobes/Makefile
===================================================================
--- /dev/null
+++ linux-2.6.23-rc7/samples/kprobes/Makefile
@@ -0,0 +1,5 @@
+# builds the kprobes example kernel modules;
+# then to use one (as root): insmod <module_name.ko>
+
+obj-$(CONFIG_SAMPLE_KPROBES) += kprobe_example.o jprobe_example.o \
+ kretprobe_example.o
Index: linux-2.6.23-rc7/samples/Kconfig
===================================================================
--- linux-2.6.23-rc7.orig/samples/Kconfig
+++ linux-2.6.23-rc7/samples/Kconfig
@@ -7,5 +7,10 @@ menuconfig SAMPLES

if SAMPLES

+config SAMPLE_KPROBES
+ tristate "Build kprobes examples -- loadable modules only"
+ depends on KPROBES && m
+ help
+ This builds several kprobes example modules.

endif # SAMPLES
Index: linux-2.6.23-rc7/samples/kprobes/jprobe_example.c
===================================================================
--- /dev/null
+++ linux-2.6.23-rc7/samples/kprobes/jprobe_example.c
@@ -0,0 +1,64 @@
+/*
+ * Here's a sample kernel module showing the use of jprobes to dump
+ * the arguments of do_fork().
+ *
+ * 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("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("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 at %p unregistered\n", my_jprobe.kp.addr);
+}
+
+module_init(jprobe_init)
+module_exit(jprobe_exit)
+MODULE_LICENSE("GPL");
Index: linux-2.6.23-rc7/samples/kprobes/kprobe_example.c
===================================================================
--- /dev/null
+++ linux-2.6.23-rc7/samples/kprobes/kprobe_example.c
@@ -0,0 +1,89 @@
+/*
+ * 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.
+ *
+ * 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_32
+ printk("pre_handler: p->addr = 0x%p, eip = %lx, eflags = 0x%lx\n",
+ p->addr, regs->eip, regs->eflags);
+#endif
+#ifdef CONFIG_X86_64
+ printk("pre_handler: p->addr = 0x%p, rip = %lx, eflags = 0x%lx\n",
+ p->addr, regs->rip, regs->eflags);
+#endif
+#ifdef CONFIG_PPC
+ printk("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)
+{
+#if defined(CONFIG_X86_32) || defined(CONFIG_X86_64)
+ printk("post_handler: p->addr = 0x%p, eflags = 0x%lx\n",
+ p->addr, regs->eflags);
+#endif
+#ifdef CONFIG_PPC
+ printk("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("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("register_kprobe failed, returned %d\n", ret);
+ return ret;
+ }
+ printk("Planted kprobe at %p\n", kp.addr);
+ return 0;
+}
+
+static void __exit kprobe_exit(void)
+{
+ unregister_kprobe(&kp);
+ printk("kprobe at %p unregistered\n", kp.addr);
+}
+
+module_init(kprobe_init)
+module_exit(kprobe_exit)
+MODULE_LICENSE("GPL");
Index: linux-2.6.23-rc7/samples/kprobes/kretprobe_example.c
===================================================================
--- /dev/null
+++ linux-2.6.23-rc7/samples/kprobes/kretprobe_example.c
@@ -0,0 +1,59 @@
+/*
+ * Here's a sample kernel module showing the use of return probes to
+ * report the return value from do_fork().
+ *
+ * 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 sys_open() returns a negative value. (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>
+
+/* Return-probe handler: If the probed function fails, log the return value. */
+static int ret_handler(struct kretprobe_instance *ri, struct pt_regs *regs)
+{
+ int retval = regs_return_value(regs);
+
+ printk("do_fork returns %d\n", retval);
+ return 0;
+}
+
+static struct kretprobe my_kretprobe = {
+ .handler = ret_handler,
+ .kp = {
+ .symbol_name = "do_fork",
+ },
+ /* Probe up to 20 instances concurrently. */
+ .maxactive = 20,
+};
+
+static int __init kretprobe_init(void)
+{
+ int ret;
+
+ ret = register_kretprobe(&my_kretprobe);
+ if (ret < 0) {
+ printk("register_kretprobe failed, returned %d\n", ret);
+ return -1;
+ }
+ printk("Planted return probe at %p\n", my_kretprobe.kp.addr);
+ return 0;
+}
+
+static void __exit kretprobe_exit(void)
+{
+ unregister_kretprobe(&my_kretprobe);
+ printk("kretprobe at %p unregistered\n", my_kretprobe.kp.addr);
+
+ /* nmissed > 0 suggests that maxactive was set too low. */
+ printk("Missed probing %d instances of do_fork()\n",
+ my_kretprobe.nmissed);
+}
+
+module_init(kretprobe_init)
+module_exit(kretprobe_exit)
+MODULE_LICENSE("GPL");
Index: linux-2.6.23-rc7/Documentation/kprobes.txt
===================================================================
--- linux-2.6.23-rc7.orig/Documentation/kprobes.txt
+++ linux-2.6.23-rc7/Documentation/kprobes.txt
@@ -166,7 +166,8 @@ 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
-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

@@ -392,220 +393,15 @@ e. Watchpoint probes (which fire on data

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

-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

-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>
-
-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)
-{
- int retval = regs_return_value(regs);
- if (retval < 0) {
- printk("%s returns %d\n", probed_func, retval);
- }
- return 0;
-}
-
-static struct kretprobe my_kretprobe = {
- .handler = ret_handler,
- /* Probe up to 20 instances concurrently. */
- .maxactive = 20
-};
-
-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("Planted return probe at %p\n", my_kretprobe.kp.addr);
- 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
Index: linux-2.6.23-rc7/samples/Makefile
===================================================================
--- /dev/null
+++ linux-2.6.23-rc7/samples/Makefile
@@ -0,0 +1,3 @@
+# Makefile for Linux samples code
+
+obj-$(CONFIG_SAMPLES) += kprobes/
Index: linux-2.6.23-rc7/samples/Kbuild
===================================================================
--- linux-2.6.23-rc7.orig/samples/Kbuild
+++ /dev/null
@@ -1,2 +0,0 @@
-# Makefile for Linux samples code
-
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
\
 
 \ /
  Last update: 2007-09-25 12:03    [from the cache]
©2003-2014 Jasper Spaans. Advertise on this site