[PATCH for review] [83/145] x86_64: fix is_at_popf() for compat tasks

Andi Kleen
2006-08-10T20:06:40Z

r

From: Chuck Ebbert <76306.1226@compuserve.com>

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>

---
arch/x86_64/kernel/ptrace.c | 5 ++++-
1 files changed, 4 insertions(+), 1 deletion(-)

Index: linux/arch/x86_64/kernel/ptrace.c
===================================================================
--- linux.orig/arch/x86_64/kernel/ptrace.c
+++ linux/arch/x86_64/kernel/ptrace.c
@@ -141,8 +141,11 @@ static int is_at_popf(struct task_struct
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 */