Messages in this thread | | | Date | Sun, 31 May 2009 09:14:03 +0300 | Subject | Re: [patch 0/5] Support for sanitization flag in low-level page allocator | From | Pekka Enberg <> |
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Hi Alan,
On Sun, May 31, 2009 at 2:10 AM, Alan Cox <alan@lxorguk.ukuu.org.uk> wrote: >> It's pretty damn obvious that Larry's patches have a much bigger >> performance impact than using kzfree() for selected parts of the >> kernel. So yes, I do expect him to benchmark and demonstrate that >> kzfree() has _performance problems_ before we can look into merging >> his patches. > > We seem to be muddling up multiple things here which is not helpful.
Yup.
On Sun, May 31, 2009 at 2:10 AM, Alan Cox <alan@lxorguk.ukuu.org.uk> wrote: > There are three things going on > > #1 Is ksize() buggy ?
No, there's nothing wrong with ksize() I am aware of. Yes, Larry has been saying it is but hasn't provided any evidence so far.
On Sun, May 31, 2009 at 2:10 AM, Alan Cox <alan@lxorguk.ukuu.org.uk> wrote: > #2 Using kzfree() to clear specific bits of memory (and I question the > kzfree implementation as it seems ksize can return numbers much much > bigger than the allocated space you need to clear - correct but oversize) > or using other flags. I'd favour kzfree personally (and fixing it to work > properly)
Well, yes, that's what kzfree() needs to do given the current API. I am not sure why you think it's a problem, though. Adding a size argument to the function will make it more error prone.
On Sun, May 31, 2009 at 2:10 AM, Alan Cox <alan@lxorguk.ukuu.org.uk> wrote: > #3 People wanting to be able to select for more security *irrespective* > of performance cost. Which is no different to SELinux for example.
Yeah, as I said before, I really don't have any objections to this. I just think nobody is going to enable it so memset() or kzfree() in relevant places is probably a good idea.
Pekka
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