Re: meaning of vmalloc shortcut comment in fault.c

[Brian Gerst]

Bjorn Wesen wrote:
> 
> Can someone elaborate on why it's bad to refer to tsk directly below (this
> is a 2.4.5 change in x86) and why it's needed on x86 and not other archs..
> 
> What should I do for an arch that does not have a "cr3" machine register
> to check with ?

%cr3 is the page table pointer on the x86.  Changing the page table
pointer and changing the stack pointer (from which tsk is derived) is
not done atomically during a task switch.  If an interrupt happens in
between and causes a page fault on a vmalloced area, using tsk may refer
to the wrong page tables.  %cr3 by definition always has the current
page table pointer.

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				Brian Gerst