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

From: Luca Barbieri (
Date: Tue Aug 20 2002 - 09:06:58 EST

> > Something like this:
> > ENTRY(debug)
> > testl $0x3, 4(%esp)
> > jz handle_kernel_mode_debug
> >
> This check is insufficient, it can go the wrong way if the interrupted
> taks is in vm 86 mode (and open a big security hole, I believe).
This test from ret_from_intr could be used instead:

push %es
push %ds
push %eax
movl 8(%esp), %eax
movb 4(%esp), %al
testl $(VM_MASK | 3), %eax
jz handle_kernel_mode

There is however a potential register stall for the eax read after the
al write.

BTW, vm86 has the VM flag set so the comment in ret_from_intr is wrong.
The code seems to be right though.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

This archive was generated by hypermail 2b29 : Fri Aug 23 2002 - 22:00:20 EST