Re: [PATCH] (re-xmit): kprobes for i386

From: Linus Torvalds (
Date: Tue Aug 20 2002 - 14:29:48 EST

On 20 Aug 2002, Luca Barbieri wrote:
> How about checking %cs in assembly and branching off for the kernel-mode
> case?
> Something like this:
> ENTRY(debug)
> testl $0x3, 4(%esp)
> jz handle_kernel_mode_debug

That's not correct, you can have the low bits of CS clear even from user
mode if the thing is in vm86 mode.

See the full test at the top of "ret_from_intr" (the "mix EFLAGS and CS"
thing - it's a bit funky).


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