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From
SubjectRe: [PATCH] 2.4.0 i386 watchpoint problems
Date
Followup to:  <Pine.LNX.4.10.10009211031370.1348-100000@penguin.transmeta.com>
By author: Linus Torvalds <torvalds@transmeta.com>
In newsgroup: linux.dev.kernel
> Actually, even simpler approach:
>
> - always clear db7 after sending signal - don't test for pending or for
> kernel mode at all at that point.
> - re-load %db7 at the top of the for(;;) loop in do_signal().
>
> That should mean that you will actually get a debug signal for ALL
> triggers of the debug registers, except you'll only get one for kernel
> mode.
>
> (For extra credit, make the patch use "eip=-1" in the siginfo structure if
> the trap happened in kernel mode, so that we don't leak kernel addresses
> to user space. Not that it would be much of a security issue, but it's a
> beauty wart that could easily be cleared up).
>

It could be (and so would even giving the signals in kernel
mode)... remember that silly case of passwords crossing page
boundaries?

-hpa
--
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."
http://www.zytor.com/~hpa/puzzle.txt
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