Messages in this thread |  | | | Date | Thu, 12 Jun 2003 22:24:27 -0700 (PDT) | | From | Linus Torvalds <> | | Subject | Re: FIXMAP-related change to mm/memory.c |
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On Thu, 12 Jun 2003, David Mosberger wrote: > > Is it possible to constrain the FIXADDR range on x86/x86-64 > (FIXADDR_START-FIXADDR_TOP) such that the entire range is read-only by > user-level? If so, we could simplify the permission test like this:
Well, you could replace the uses of FIXADDR_START/FIXADDR_TOP with something like FIXADDR_USER_START/FIXADDR_USER_TOP, and then force those to cover only the _one_ user-accessible page.
Something like
#define FIXADDR_USER_START (fix_to_virt(FIX_VSYSCALL)) #define FIXADDR_USER_END (FIXADDR_USER_START + PAGE_SIZE)
should work. In that case you can drop the page table testing, since we "know" it is safe.
But I'm too lazy to test, so please send a tested patch,
Linus
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