Re: Generic page fault (Was: libsigsegv ....)

[Linus Torvalds <torvalds@linux-foundation.org>]

On Sat, Feb 28, 2015 at 3:02 PM, Benjamin Herrenschmidt
<benh@kernel.crashing.org> wrote:
>
> Anyway, here's the current patch:

Ok, I think I like this approach better.

Your FAULT_FLAG_EXEC handling is wrong, though. It shouldn't check
VM_WRITE, it should check VM_EXEC. A bit too much copy-paste ;)

Btw, it's quite possible that we could just do all the PF_PROT
handling at the x86 level, before even calling the generic fault
handler. It's not like we even need the vma or the mm semaphore: if
it's a non-write protection fault, we always SIGSEGV. So why even
bother getting the locks and looking up the page tables etc?

Now, that PF_PROT handling isn't exactly performance-critical, but it
might help to remove the odd x86 special case from the generic code.

                      Linus

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