From c029b47407b5f2bd69d66323f133432bd0293166 Mon Sep 17 00:00:00 2001
From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Date: Tue, 29 Jun 2010 14:53:50 +0900
Subject: [PATCH] --- yaml --- r: 205295 b: refs/heads/master c:
 567a9fd86735ccdc897768ed2dacdd5e83a13509 h: refs/heads/master i:   205293:
 9782d8fa2f26ca25e083419cdc6d25635460d743   205291:
 da4373afbf7d381d7cf0e31ce3a36556c5c0d478   205287:
 06d0035616797c81780fc84ef2e32c77fbe1e4ed   205279:
 90c2a028cf2769907174144c77db2e267a341fdf v: v3

---
 [refs]                          |  2 +-
 trunk/arch/x86/kernel/kprobes.c | 33 +++++++++++++++++----------------
 2 files changed, 18 insertions(+), 17 deletions(-)

diff --git a/[refs] b/[refs]
index 4b0f3415bdc3..bc1f4bf7b236 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: a1d0ce8213e9ddf4046ef5ba95c55762d075f541
+refs/heads/master: 567a9fd86735ccdc897768ed2dacdd5e83a13509
diff --git a/trunk/arch/x86/kernel/kprobes.c b/trunk/arch/x86/kernel/kprobes.c
index 345a4b1fe144..175f85ceace3 100644
--- a/trunk/arch/x86/kernel/kprobes.c
+++ b/trunk/arch/x86/kernel/kprobes.c
@@ -126,16 +126,22 @@ static void __kprobes synthesize_reljump(void *from, void *to)
 }
 
 /*
- * Check for the REX prefix which can only exist on X86_64
- * X86_32 always returns 0
+ * Skip the prefixes of the instruction.
  */
-static int __kprobes is_REX_prefix(kprobe_opcode_t *insn)
+static kprobe_opcode_t *__kprobes skip_prefixes(kprobe_opcode_t *insn)
 {
+	insn_attr_t attr;
+
+	attr = inat_get_opcode_attribute((insn_byte_t)*insn);
+	while (inat_is_legacy_prefix(attr)) {
+		insn++;
+		attr = inat_get_opcode_attribute((insn_byte_t)*insn);
+	}
 #ifdef CONFIG_X86_64
-	if ((*insn & 0xf0) == 0x40)
-		return 1;
+	if (inat_is_rex_prefix(attr))
+		insn++;
 #endif
-	return 0;
+	return insn;
 }
 
 /*
@@ -272,6 +278,9 @@ static int __kprobes can_probe(unsigned long paddr)
  */
 static int __kprobes is_IF_modifier(kprobe_opcode_t *insn)
 {
+	/* Skip prefixes */
+	insn = skip_prefixes(insn);
+
 	switch (*insn) {
 	case 0xfa:		/* cli */
 	case 0xfb:		/* sti */
@@ -280,13 +289,6 @@ static int __kprobes is_IF_modifier(kprobe_opcode_t *insn)
 		return 1;
 	}
 
-	/*
-	 * on X86_64, 0x40-0x4f are REX prefixes so we need to look
-	 * at the next byte instead.. but of course not recurse infinitely
-	 */
-	if (is_REX_prefix(insn))
-		return is_IF_modifier(++insn);
-
 	return 0;
 }
 
@@ -803,9 +805,8 @@ static void __kprobes resume_execution(struct kprobe *p,
 	unsigned long orig_ip = (unsigned long)p->addr;
 	kprobe_opcode_t *insn = p->ainsn.insn;
 
-	/*skip the REX prefix*/
-	if (is_REX_prefix(insn))
-		insn++;
+	/* Skip prefixes */
+	insn = skip_prefixes(insn);
 
 	regs->flags &= ~X86_EFLAGS_TF;
 	switch (*insn) {