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Date: Tue, 29 Mar 2005 14:29:36 -0800
From: Hien Nguyen <hien@us.ibm.com>
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To: linux-kernel@vger.kernel.org
Subject: [PATCH 2.6.12-rc1-mm3] [2/2] kprobes += function-return probes -
 example: probing arbitrary functions
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Also include here is a test module

The testrprobe.ko is a generic test module. One could use this module to 
insert an exit probe to any function in the kernel.
For example :
insmod test_rprobe.ko <entryaddr=address for func entry>
or use the included loadtestrprobe.sh script
./loadtestrprobe.sh <function name>

One good example is to see what kind of page fault is encountered
./loadtestrprobe.sh handle_mm_fault

Signed-off-by: hien Nguyen <hien@us.ibm.com>

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#include <linux/module.h>
#include <linux/kprobes.h>

static unsigned long entryaddr;
module_param(entryaddr, ulong, 0);
MODULE_PARM_DESC(addr,
		 "\nfunction entry address.\n");

int inst_test_erprobe (void)
{
	jprobe_return();
	return 0;
}


int rp_handler(struct retprobe_instance *ri, struct pt_regs *regs)
{
	printk("rprobe handler: p->addr=0x%p, ret=0x%lx\n", ri->rp->kprobe->addr, regs->eax);
	return 0;
}
	
static struct jprobe jp = {
	.entry = (kprobe_opcode_t *) inst_test_erprobe,
};


static struct retprobe rp = {
	.handler = rp_handler,
	.maxactive = 1,
	.nmissed = 0
};


static int init_testrp(void)
{
  if (entryaddr == 0 ) {
    printk("Need to input an function entry address as parameter.\n");
    return -EINVAL;
  }
  jp.kp.addr = (kprobe_opcode_t *) entryaddr;

  register_jretprobe(&jp, &rp);
  printk("exit probe init: instrumentation is enabled...\n");
  return 0;
}

static void cleanup_testrp(void)
{
  unregister_jprobe(&jp);
  printk("exit probe cleanup.\n");
}

module_init(init_testrp);
module_exit(cleanup_testrp);
MODULE_LICENSE("GPL");


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