Messages in this thread Patch in this message | | | Date | Mon, 31 Jul 2006 12:59:16 -0400 | From | Chuck Ebbert <> | Subject | Re: [patch] x86_64: fix is_at_popf() for compat tasks |
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In-Reply-To: <200607311054.38585.ak@suse.de>
On Mon, 31 Jul 2006 10:54:38 +0200, Andi Kleen wrote: > > > When testing for the REX instruction prefix, first check > > for a 32-bit task because in compat mode the REX prefix is an > > increment instruction. > > is_compat_task doesn't actually say that a task is in compat mode > (it refers to the Linux compat layer, not x86-64 compat mode) > > A better test would be regs->cs == __USER32_CS, but in theory > there could be other code segments in LDT. I guess that can > be ignored though.
How about checking for regs->cs != __USER_CS instead? In 64-bit mode a program shouldn't have any other value there while in 32-bit mode it could be using LDT segments.
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>
--- 2.6.18-rc2-64.orig/arch/x86_64/kernel/ptrace.c +++ 2.6.18-rc2-64/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 */ -- Chuck - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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