Messages in this thread | | | Date | Sat, 26 Apr 2008 10:15:33 -0700 (PDT) | From | Linus Torvalds <> | Subject | RE: [git pull] x86 PAT changes |
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On Sat, 26 Apr 2008, Pallipadi, Venkatesh wrote: > > Agreed that NONPROMISC_DEVMEM is not really needed for read/write. But, > we will still need it for /dev/mem.
If so, just disable it unconditionally for mmap.
As mentioned, that's really just a return to original Linux /dev/mmap semantics: long ago (well, not _that_ long ago) we never used to be able to mmap() normal kernel memory, because the page counts would get screwed up on pages that weren't marked PG_Reserved.
So the traditional Linux behavior for mmap() on /dev/mem was always to only allow it on memory that either had no "struct page *" backing at all, or that was marked PG_Reserved (ie the ISA hole ay 640k-1M and things like the BIOS tables etc).
Going back to that doesn't sound horrible.
Linus
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