[PATCH] kprobe handler: discard user space trap

Currently kprobe handler traps only happen in kernel space, so function
kprobe_exceptions_notify should skip traps which happen in user space.
This patch modifies this, and it is based on 2.6.16-rc4.

Signed-off-by: bibo mao <bibo.mao@intel.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: "Keshavamurthy, Anil S" <anil.s.keshavamurthy@intel.com>
Cc: <hiramatu@sdl.hitachi.co.jp>
Signed-off-by: Prasanna S Panchamukhi <prasanna@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/i386/kernel/kprobes.c

@@ -203,31 +203,21 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
 {
 	struct kprobe *p;
 	int ret = 0;
-	kprobe_opcode_t *addr = NULL;
-	unsigned long *lp;
+	kprobe_opcode_t *addr;
 	struct kprobe_ctlblk *kcb;
 #ifdef CONFIG_PREEMPT
 	unsigned pre_preempt_count = preempt_count();
 #endif /* CONFIG_PREEMPT */
 
+	addr = (kprobe_opcode_t *)(regs->eip - sizeof(kprobe_opcode_t));
+
 	/*
 	 * We don't want to be preempted for the entire
 	 * duration of kprobe processing
 	 */
 	preempt_disable();
 	kcb = get_kprobe_ctlblk();
 
-	/* Check if the application is using LDT entry for its code segment and
-	 * calculate the address by reading the base address from the LDT entry.
-	 */
-	if ((regs->xcs & 4) && (current->mm)) {
-		lp = (unsigned long *) ((unsigned long)((regs->xcs >> 3) * 8)
-					+ (char *) current->mm->context.ldt);
-		addr = (kprobe_opcode_t *) (get_desc_base(lp) + regs->eip -
-						sizeof(kprobe_opcode_t));
-	} else {
-		addr = (kprobe_opcode_t *)(regs->eip - sizeof(kprobe_opcode_t));
-	}
 	/* Check we're not actually recursing */
 	if (kprobe_running()) {
 		p = get_kprobe(addr);
@@ -579,6 +569,9 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 	struct die_args *args = (struct die_args *)data;
 	int ret = NOTIFY_DONE;
 
+	if (args->regs && user_mode(args->regs))
+		return ret;
+
 	switch (val) {
 	case DIE_INT3:
 		if (kprobe_handler(args->regs))

arch/ia64/kernel/kprobes.c

@@ -740,6 +740,9 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 	struct die_args *args = (struct die_args *)data;
 	int ret = NOTIFY_DONE;
 
+	if (args->regs && user_mode(args->regs))
+		return ret;
+
 	switch(val) {
 	case DIE_BREAK:
 		/* err is break number from ia64_bad_break() */

arch/powerpc/kernel/kprobes.c

@@ -396,6 +396,9 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 	struct die_args *args = (struct die_args *)data;
 	int ret = NOTIFY_DONE;
 
+	if (args->regs && user_mode(args->regs))
+		return ret;
+
 	switch (val) {
 	case DIE_BPT:
 		if (kprobe_handler(args->regs))

arch/sparc64/kernel/kprobes.c

@@ -324,6 +324,9 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 	struct die_args *args = (struct die_args *)data;
 	int ret = NOTIFY_DONE;
 
+	if (args->regs && user_mode(args->regs))
+		return ret;
+
 	switch (val) {
 	case DIE_DEBUG:
 		if (kprobe_handler(args->regs))

arch/x86_64/kernel/kprobes.c

@@ -601,6 +601,9 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 	struct die_args *args = (struct die_args *)data;
 	int ret = NOTIFY_DONE;
 
+	if (args->regs && user_mode(args->regs))
+		return ret;
+
 	switch (val) {
 	case DIE_INT3:
 		if (kprobe_handler(args->regs))