Kprobes: print details of kretprobe on assertion failure

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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

5 files changed, 15 insertions, 5 deletions

diff --git a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c
index e00f75ecf1a8..3fbef288c376 100644
--- a/arch/i386/kernel/kprobes.c
+++ b/arch/i386/kernel/kprobes.c
@@ -449,8 +449,7 @@ fastcall void *__kprobes trampoline_handler(struct pt_regs *regs)
                         break;
         }
 
-        BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address));
-
+        kretprobe_assert(ri, orig_ret_address, trampoline_address);
         spin_unlock_irqrestore(&kretprobe_lock, flags);
 
         hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
diff --git a/arch/ia64/kernel/kprobes.c b/arch/ia64/kernel/kprobes.c
index 779fe00c9025..353689edebd5 100644
--- a/arch/ia64/kernel/kprobes.c
+++ b/arch/ia64/kernel/kprobes.c
@@ -444,7 +444,8 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
                         break;
         }
 
-        BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address));
+        kretprobe_assert(ri, orig_ret_address, trampoline_address);
+
         regs->cr_iip = orig_ret_address;
 
         reset_current_kprobe();
diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index 2a2c696dcc7a..3d54ad7dd1f9 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -336,7 +336,7 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
                         break;
         }
 
-        BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address));
+        kretprobe_assert(ri, orig_ret_address, trampoline_address);
         regs->nip = orig_ret_address;
 
         reset_current_kprobe();
diff --git a/arch/x86_64/kernel/kprobes.c b/arch/x86_64/kernel/kprobes.c
index 90e7008cd899..5841ba5f479b 100644
--- a/arch/x86_64/kernel/kprobes.c
+++ b/arch/x86_64/kernel/kprobes.c
@@ -447,7 +447,7 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
                         break;
         }
 
-        BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address));
+        kretprobe_assert(ri, orig_ret_address, trampoline_address);
         regs->rip = orig_ret_address;
 
         reset_current_kprobe();
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index f26460700379..850ee871e353 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -157,6 +157,16 @@ struct kretprobe_instance {
         struct task_struct *task;
 };
 
+static inline void kretprobe_assert(struct kretprobe_instance *ri,
+        unsigned long orig_ret_address, unsigned long 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();
+        }
+}
+
 extern spinlock_t kretprobe_lock;
 extern struct mutex kprobe_mutex;
 extern int arch_prepare_kprobe(struct kprobe *p);