From: Chuck Ebbert <76306.1226@compuserve.com>
Date: Tue, 26 Sep 2006 08:52:32 +0000 (+0200)
Subject: [PATCH] fix is_at_popf() for compat tasks
X-Git-Tag: v2.6.19-rc1~1077^2~143
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a752d7194c4fb5a3e767c95542d04fc5decb1d52;p=linux-2.6

[PATCH] fix is_at_popf() for compat tasks

When testing for the REX instruction prefix, first check
for 32-bit mode because in compat mode the REX prefix is an
increment instruction.

Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com>
Signed-off-by: Andi Kleen <ak@suse.de>
---

diff --git a/arch/x86_64/kernel/ptrace.c b/arch/x86_64/kernel/ptrace.c
index d35ec1bc69..3a52c7bcfd 100644
--- a/arch/x86_64/kernel/ptrace.c
+++ b/arch/x86_64/kernel/ptrace.c
@@ -141,8 +141,11 @@ static int is_at_popf(struct task_struct *child, struct pt_regs *regs)
 		case 0xf0: case 0xf2: case 0xf3:
 			continue;
 
-		/* REX prefixes */
 		case 0x40 ... 0x4f:
+			if (regs->cs != __USER_CS)
+				/* 32-bit mode: register increment */
+				return 0;
+			/* 64-bit mode: REX prefix */
 			continue;
 
 			/* CHECKME: f0, f2, f3 */