From 158c3f3acba667f99c4e7b38b1f4e764a412ccae Mon Sep 17 00:00:00 2001
From: Vasiliy Ulyanov <v.ulyanov@samsung.com>
Date: Wed, 27 Feb 2013 11:53:00 +0400
Subject: [PATCH] Fix user space retprobe disarming

For functions which do not push return address on stack
---
 kprobe/arch/asm-arm/dbi_kprobes.h |  5 +++++
 kprobe/arch/asm-x86/dbi_kprobes.h |  5 +++++
 kprobe/dbi_uprobes.c              | 19 +++++++++++++++----
 3 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/kprobe/arch/asm-arm/dbi_kprobes.h b/kprobe/arch/asm-arm/dbi_kprobes.h
index 250f823..ff7dd5f 100644
--- a/kprobe/arch/asm-arm/dbi_kprobes.h
+++ b/kprobe/arch/asm-arm/dbi_kprobes.h
@@ -101,6 +101,11 @@ static inline unsigned long dbi_get_ret_addr(struct pt_regs *regs)
 	return regs->ARM_lr;
 }
 
+static inline void dbi_set_ret_addr(struct pt_regs *regs, unsigned long val)
+{
+	regs->ARM_lr = val;
+}
+
 static inline unsigned long dbi_get_arg(struct pt_regs *regs, int num)
 {
 	return regs->uregs[num];
diff --git a/kprobe/arch/asm-x86/dbi_kprobes.h b/kprobe/arch/asm-x86/dbi_kprobes.h
index 75193f8..c3b1741 100644
--- a/kprobe/arch/asm-x86/dbi_kprobes.h
+++ b/kprobe/arch/asm-x86/dbi_kprobes.h
@@ -128,6 +128,11 @@ static inline unsigned long dbi_get_ret_addr(struct pt_regs *regs)
 	return addr;
 }
 
+static inline void dbi_set_ret_addr(struct pt_regs *regs, unsigned long val)
+{
+	write_proc_vm_atomic(current, regs->EREG(sp), &val, sizeof(val));
+}
+
 static inline unsigned long dbi_get_arg(struct pt_regs *regs, int num)
 {
 	unsigned long arg = 0;
diff --git a/kprobe/dbi_uprobes.c b/kprobe/dbi_uprobes.c
index 1f3209a..3e6d394 100644
--- a/kprobe/dbi_uprobes.c
+++ b/kprobe/dbi_uprobes.c
@@ -299,7 +299,8 @@ int dbi_disarm_urp_inst(struct kretprobe_instance *ri, struct task_struct *rm_ta
 	if (found) {
 		printk("---> %s (%d/%d): trampoline found at %08lx (%08lx /%+d) - %p\n",
 				task->comm, task->tgid, task->pid,
-				(unsigned long)found, (unsigned long)ri->sp, found - ri->sp, ri->rp->kp.addr);
+				(unsigned long)found, (unsigned long)ri->sp,
+				found - ri->sp, ri->rp->kp.addr);
 		retval = write_proc_vm_atomic(task, (unsigned long)found, &ri->ret_addr,
 				sizeof(ri->ret_addr));
 		if (retval != sizeof(ri->ret_addr)) {
@@ -310,9 +311,19 @@ int dbi_disarm_urp_inst(struct kretprobe_instance *ri, struct task_struct *rm_ta
 			retval = 0;
 		}
 	} else {
-		printk("---> %s (%d/%d): trampoline NOT found at sp = %08lx - %p\n",
-				task->comm, task->tgid, task->pid, (unsigned long)ri->sp, ri->rp->kp.addr);
-		retval = -ENOENT;
+		struct pt_regs *uregs = task_pt_regs(ri->task);
+		unsigned long ra = dbi_get_ret_addr(uregs);
+		if (ra == (unsigned long)tramp) {
+			printk("---> %s (%d/%d): trampoline found at lr = %08lx - %p\n",
+					task->comm, task->tgid, task->pid, ra, ri->rp->kp.addr);
+			dbi_set_ret_addr(uregs, (unsigned long)tramp);
+			retval = 0;
+		} else {
+			printk("---> %s (%d/%d): trampoline NOT found at sp = %08lx, lr = %08lx - %p\n",
+					task->comm, task->tgid, task->pid,
+					(unsigned long)ri->sp, ra, ri->rp->kp.addr);
+			retval = -ENOENT;
+		}
 	}
 
 out:
-- 
2.7.4