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Kprobes: Print details of kretprobe on assertion failure

PATCH In review Ananth N Mavinakayanahalli 2 participants 3 messages Apr 2, 2007 – Apr 3, 2007

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Ananth N Mavinakayanahalli

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#0 lore raw

PATCH 1/1 Kprobes: Print details of kretprobe on assertion failure

From: Ananth N Mavinakayanahalli <[email protected]>

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 <[email protected]>
---
 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(-)
arch/i386/kernel/kprobes.c +5 -1
Index: 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);
arch/ia64/kernel/kprobes.c +6 -1
Index: 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();
arch/powerpc/kernel/kprobes.c +6 -1
Index: 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();
arch/x86_64/kernel/kprobes.c +6 -1
Index: 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();
#1 lore raw
Quoted 79 lines · On Mon, 2 Apr 2007 14:56:36 +0530 Ananth N Mavinakayanahalli…

From: Ananth N Mavinakayanahalli <[email protected]>

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 <[email protected]>
---
 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
===================================================================

arch/i386/kernel/kprobes.c +5 -1
@@ -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
===================================================================

arch/ia64/kernel/kprobes.c +6 -1
@@ -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
===================================================================

arch/powerpc/kernel/kprobes.c +6 -1
@@ -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
===================================================================

arch/x86_64/kernel/kprobes.c +0 -0
@@ -438,7 +438,12 @@ int __kprobes trampoline_probe_handler(s
 			break;
 	}

arch/x86_64/kernel/kprobes.c int __kprobes trampoline_probe_handler(s · line 448

Quoted 10 lines
arch/x86_64/kernel/kprobes.c +6 -1
 
-	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;

A lot of copying-and-pasting there. Would it be better if this assertion was performed in a library function in kernel/kprobes.c?

author
#2 lore raw
Quoted 83 lines · Andrew Morton
Quoted 80 lines · On Mon, 2 Apr 2007 14:56:36 +0530 Ananth N Mavinakayanahalli…

From: Ananth N Mavinakayanahalli <[email protected]>

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 <[email protected]>
---
 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
===================================================================

arch/i386/kernel/kprobes.c +5 -1
@@ -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
===================================================================

arch/ia64/kernel/kprobes.c +6 -1
@@ -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
===================================================================

arch/powerpc/kernel/kprobes.c +6 -1
@@ -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
===================================================================

arch/x86_64/kernel/kprobes.c +0 -0
@@ -438,7 +438,12 @@ int __kprobes trampoline_probe_handler(s
 			break;
 	}
Quoted 12 lines

arch/x86_64/kernel/kprobes.c int __kprobes trampoline_probe_handler(s · line 448

Quoted 9 lines
arch/x86_64/kernel/kprobes.c +6 -1
-	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;

A lot of copying-and-pasting there. Would it be better if this assertion was performed in a library function in kernel/kprobes.c?

Indeed. Here is the updated patch...

From: Ananth N Mavinakayanahalli <[email protected]>

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 <[email protected]>
---
 arch/i386/kernel/kprobes.c    |    3 +--
 arch/ia64/kernel/kprobes.c    |    3 ++-
 arch/powerpc/kernel/kprobes.c |    2 +-
 arch/x86_64/kernel/kprobes.c  |    2 +-
 include/linux/kprobes.h       |   10 ++++++++++
 5 files changed, 15 insertions(+), 5 deletions(-)
arch/i386/kernel/kprobes.c +1 -2
Index: linux-2.6.21-rc5/arch/i386/kernel/kprobes.c
===================================================================
@@ -440,8 +440,7 @@ fastcall void *__kprobes trampoline_hand
 			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) {
arch/ia64/kernel/kprobes.c +2 -1
Index: linux-2.6.21-rc5/arch/ia64/kernel/kprobes.c
===================================================================
@@ -444,7 +444,8 @@ int __kprobes trampoline_probe_handler(s
 			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();
arch/powerpc/kernel/kprobes.c +1 -1
Index: linux-2.6.21-rc5/arch/powerpc/kernel/kprobes.c
===================================================================
@@ -293,7 +293,7 @@ int __kprobes trampoline_probe_handler(s
 			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();
arch/x86_64/kernel/kprobes.c +1 -1
Index: linux-2.6.21-rc5/arch/x86_64/kernel/kprobes.c
===================================================================
@@ -438,7 +438,7 @@ int __kprobes trampoline_probe_handler(s
 			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();
include/linux/kprobes.h +10 -0
Index: linux-2.6.21-rc5/include/linux/kprobes.h
===================================================================
@@ -158,6 +158,16 @@ 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);