Messages in this thread | | | Date | Mon, 7 May 2001 09:51:16 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: [PATCH] x86 page fault handler not interrupt safe |
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On Mon, 7 May 2001, Alan Cox wrote: > > I dont see that we will get a valid value in both cases. > > get_user > fault - set %cr2 > IRQ > vmalloc > fault > set %cr2 > fixup runs > end IRQ > cr2 is corrupt
Wrong. "%cr2" is _not_ "corrupt". It has a well-defined value.
So what happens is
get_user (or user-mode access) fault - set %cr2 to fault1 irq vmalloc fault - set %cr2 to fault2 fixup runs, iret irq runs, iret %cr2 is still %fault2 vmalloc fault - nothing to do "false fixup" runs, iret get_user (or user-mode access) fault - set %cr2 to fault1 ... get the right behaviour now ...
> There are a whole set of races with the vmalloc fixups.
As far as I can tell, there are no races anywhere. Just silly bugs that are hard to see.
Linus
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