kprobes: kretprobe user entry-handler

Provide support to add an optional user defined callback to be run at
function entry of a kretprobe'd function.  Also modify the kprobe smoke
tests to include an entry-handler during the kretprobe sanity test.

Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com>
Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Acked-by: Jim Keniston <jkenisto@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 14 insertions, 2 deletions

diff --git a/kernel/test_kprobes.c b/kernel/test_kprobes.c
index 88cdb10..06b6395 100644
--- a/kernel/test_kprobes.c
+++ b/kernel/test_kprobes.c
@@ -135,6 +135,12 @@ static int test_jprobe(void)
 #ifdef CONFIG_KRETPROBES
 static u32 krph_val;
 
+static int entry_handler(struct kretprobe_instance *ri, struct pt_regs *regs)
+{
+	krph_val = (rand1 / div_factor);
+	return 0;
+}
+
 static int return_handler(struct kretprobe_instance *ri, struct pt_regs *regs)
 {
 	unsigned long ret = regs_return_value(regs);
@@ -144,13 +150,19 @@ static int return_handler(struct kretprobe_instance *ri, struct pt_regs *regs)
 		printk(KERN_ERR "Kprobe smoke test failed: "
 				"incorrect value in kretprobe handler\n");
 	}
+	if (krph_val == 0) {
+		handler_errors++;
+		printk(KERN_ERR "Kprobe smoke test failed: "
+				"call to kretprobe entry handler failed\n");
+	}
 
-	krph_val = (rand1 / div_factor);
+	krph_val = rand1;
 	return 0;
 }
 
 static struct kretprobe rp = {
 	.handler	= return_handler,
+	.entry_handler  = entry_handler,
 	.kp.symbol_name = "kprobe_target"
 };
 
@@ -167,7 +179,7 @@ static int test_kretprobe(void)
 
 	ret = kprobe_target(rand1);
 	unregister_kretprobe(&rp);
-	if (krph_val == 0) {
+	if (krph_val != rand1) {
 		printk(KERN_ERR "Kprobe smoke test failed: "
 				"kretprobe handler not called\n");
 		handler_errors++;