From: Ananth N Mavinakayanahalli <ananth@in.ibm.com>

In certain cases like when the real return address can't be found or when
the number of tracked calls to a kretprobed function is less than the
number of returns, we may not be able to find the correct return address
after processing a kretprobe.  Currently we just do a BUG_ON, but no
information is provided about the actual failing kretprobe.

Print out details of the kretprobe before calling BUG().

Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com>
Cc: Jim Keniston <jkenisto@us.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: Maneesh Soni <maneesh@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 arch/i386/kernel/kprobes.c    |    6 +++++-
 arch/ia64/kernel/kprobes.c    |    7 ++++++-
 arch/powerpc/kernel/kprobes.c |    7 ++++++-
 arch/x86_64/kernel/kprobes.c  |    7 ++++++-
 4 files changed, 23 insertions(+), 4 deletions(-)

diff -puN arch/i386/kernel/kprobes.c~kprobes-print-details-of-kretprobe-on-assertion-failure arch/i386/kernel/kprobes.c
--- a/arch/i386/kernel/kprobes.c~kprobes-print-details-of-kretprobe-on-assertion-failure
+++ a/arch/i386/kernel/kprobes.c
@@ -449,7 +449,11 @@ fastcall void *__kprobes trampoline_hand
 			break;
 	}
 
-	BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address));
+	if (!orig_ret_address || (orig_ret_address == trampoline_address)) {
+		printk("kretprobe BUG!: Processing kretprobe %p @ %p\n",
+				ri->rp, ri->rp->kp.addr);
+		BUG();
+	}
 
 	spin_unlock_irqrestore(&kretprobe_lock, flags);
 
diff -puN arch/ia64/kernel/kprobes.c~kprobes-print-details-of-kretprobe-on-assertion-failure arch/ia64/kernel/kprobes.c
--- a/arch/ia64/kernel/kprobes.c~kprobes-print-details-of-kretprobe-on-assertion-failure
+++ a/arch/ia64/kernel/kprobes.c
@@ -444,7 +444,12 @@ int __kprobes trampoline_probe_handler(s
 			break;
 	}
 
-	BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address));
+	if (!orig_ret_address || (orig_ret_address == trampoline_address)) {
+		printk("kretprobe BUG!: Processing kretprobe %p @ %p\n",
+				ri->rp, ri->rp->kp.addr);
+		BUG();
+	}
+
 	regs->cr_iip = orig_ret_address;
 
 	reset_current_kprobe();
diff -puN arch/powerpc/kernel/kprobes.c~kprobes-print-details-of-kretprobe-on-assertion-failure arch/powerpc/kernel/kprobes.c
--- a/arch/powerpc/kernel/kprobes.c~kprobes-print-details-of-kretprobe-on-assertion-failure
+++ a/arch/powerpc/kernel/kprobes.c
@@ -302,7 +302,12 @@ int __kprobes trampoline_probe_handler(s
 			break;
 	}
 
-	BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address));
+	if (!orig_ret_address || (orig_ret_address == trampoline_address)) {
+		printk("kretprobe BUG!: Processing kretprobe %p @ %p\n",
+				ri->rp, ri->rp->kp.addr);
+		BUG();
+	}
+
 	regs->nip = orig_ret_address;
 
 	reset_current_kprobe();
diff -puN arch/x86_64/kernel/kprobes.c~kprobes-print-details-of-kretprobe-on-assertion-failure arch/x86_64/kernel/kprobes.c
--- a/arch/x86_64/kernel/kprobes.c~kprobes-print-details-of-kretprobe-on-assertion-failure
+++ a/arch/x86_64/kernel/kprobes.c
@@ -447,7 +447,12 @@ int __kprobes trampoline_probe_handler(s
 			break;
 	}
 
-	BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address));
+	if (!orig_ret_address || (orig_ret_address == trampoline_address)) {
+		printk("kretprobe BUG!: Processing kretprobe %p @ %p\n",
+				ri->rp, ri->rp->kp.addr);
+		BUG();
+	}
+
 	regs->rip = orig_ret_address;
 
 	reset_current_kprobe();
_