[PATCH] Kprobes: Print details of kretprobe on assertion failure

[Ananth N Mavinakayanahalli]

From: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>

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@xxxxxxxxxx>

---
 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(-)

Index: linux-2.6.21-rc5/arch/i386/kernel/kprobes.c
===================================================================
--- linux-2.6.21-rc5.orig/arch/i386/kernel/kprobes.c
+++ linux-2.6.21-rc5/arch/i386/kernel/kprobes.c
@@ -440,7 +440,11 @@ 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);
 
Index: linux-2.6.21-rc5/arch/ia64/kernel/kprobes.c
===================================================================
--- linux-2.6.21-rc5.orig/arch/ia64/kernel/kprobes.c
+++ linux-2.6.21-rc5/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();
Index: linux-2.6.21-rc5/arch/powerpc/kernel/kprobes.c
===================================================================
--- linux-2.6.21-rc5.orig/arch/powerpc/kernel/kprobes.c
+++ linux-2.6.21-rc5/arch/powerpc/kernel/kprobes.c
@@ -293,7 +293,12 @@ 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();
Index: linux-2.6.21-rc5/arch/x86_64/kernel/kprobes.c
===================================================================
--- linux-2.6.21-rc5.orig/arch/x86_64/kernel/kprobes.c
+++ linux-2.6.21-rc5/arch/x86_64/kernel/kprobes.c
@@ -438,7 +438,12 @@ 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();
-
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