From d966a1be7abfa0d4421464ff151fc10fc4c1f292 Mon Sep 17 00:00:00 2001
From: Maneesh Soni <manesoni@cisco.com>
Date: Tue, 8 Nov 2011 17:05:35 +0530
Subject: [PATCH] --- yaml --- r: 284771 b: refs/heads/master c:
 9233c1ee71bdd3c8a918c8e17026cf3f7d99c90b h: refs/heads/master i:   284769:
 35ac05a56abc3250bf7459c511ae432134bc5dc4   284767:
 8bd1b11895d5703caa470cdc53aaafb587548ea9 v: v3

---
 [refs]                           |  2 +-
 trunk/arch/mips/kernel/kprobes.c | 31 +++++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index 64acc6a78f34..7811de58fd7a 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 41dde781f50c39cddc8032fc04d6a7d538237737
+refs/heads/master: 9233c1ee71bdd3c8a918c8e17026cf3f7d99c90b
diff --git a/trunk/arch/mips/kernel/kprobes.c b/trunk/arch/mips/kernel/kprobes.c
index 9fb1876cb0bd..0ab1a5ff1049 100644
--- a/trunk/arch/mips/kernel/kprobes.c
+++ b/trunk/arch/mips/kernel/kprobes.c
@@ -113,6 +113,30 @@ static int __kprobes insn_has_delayslot(union mips_instruction insn)
 	return 0;
 }
 
+/*
+ * insn_has_ll_or_sc function checks whether instruction is ll or sc
+ * one; putting breakpoint on top of atomic ll/sc pair is bad idea;
+ * so we need to prevent it and refuse kprobes insertion for such
+ * instructions; cannot do much about breakpoint in the middle of
+ * ll/sc pair; it is upto user to avoid those places
+ */
+static int __kprobes insn_has_ll_or_sc(union mips_instruction insn)
+{
+	int ret = 0;
+
+	switch (insn.i_format.opcode) {
+	case ll_op:
+	case lld_op:
+	case sc_op:
+	case scd_op:
+		ret = 1;
+		break;
+	default:
+		break;
+	}
+	return ret;
+}
+
 int __kprobes arch_prepare_kprobe(struct kprobe *p)
 {
 	union mips_instruction insn;
@@ -121,6 +145,13 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
 
 	insn = p->addr[0];
 
+	if (insn_has_ll_or_sc(insn)) {
+		pr_notice("Kprobes for ll and sc instructions are not"
+			  "supported\n");
+		ret = -EINVAL;
+		goto out;
+	}
+
 	if (insn_has_delayslot(insn)) {
 		pr_notice("Kprobes for branch and jump instructions are not"
 			  "supported\n");