Messages in this thread | | | Date | Mon, 16 Feb 1998 13:19:55 -0800 (PST) | From | Linus Torvalds <> | Subject | Re: How to read-protect a vm_area? |
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On Mon, 16 Feb 1998, Linus Torvalds wrote: > > Anyway, I haven't even tried compiling this, but this very small patch > (I'd call it trivial if it wasn't so subtle) MAY work. Would somebody like > to test it?
At least part of it is bogus: if you do decide to test it, you should undo the change to _PAGE_CHG_MASK:
> --- v2.1.86/linux/include/asm-i386/pgtable.h Fri Feb 6 15:32:54 1998 > +++ linux/include/asm-i386/pgtable.h Mon Feb 16 12:37:25 1998 > @@ -211,9 +212,9 @@ > > #define _PAGE_TABLE (_PAGE_PRESENT | _PAGE_RW | _PAGE_USER | _PAGE_ACCESSED | _PAGE_DIRTY) > #define _KERNPG_TABLE (_PAGE_PRESENT | _PAGE_RW | _PAGE_ACCESSED | _PAGE_DIRTY) > -#define _PAGE_CHG_MASK (PAGE_MASK | _PAGE_ACCESSED | _PAGE_DIRTY) > +#define _PAGE_CHG_MASK (PAGE_MASK | _PAGE_ACCESSED | _PAGE_DIRTY | _PAGE_PRESENT)
The correct _PAGE_CHG_MASK is the same old mask that it used to be: _PAGE_PRESENT should not be part of the mask (just a thinko on my part, the semantics of _PAGE_CHG_MASK is not which bits you should be able to change, but which bits are carried over a change in protection).
Linus
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