On Tue, Oct 23, 2012 at 12:44:24PM +1100, Benjamin Herrenschmidt wrote: > On Mon, 2012-10-22 at 17:53 +0200, Michael Kerrisk (man-pages) wrote: > > > This is all seems to make an awful muck of the API... > > .../... > > > There seems to be a reasonable argument here for an mmap3() with a > > 64-bit flags argument... > > I tend to agree. There's a similar issue happening when we try to shovel Could you comment on the expect range of page sizes on PPC? I looked at this again and I don't think we have anywhere near true 28 flags so far. The man page currently only lists 16 (including MAP_UNUS^INITIALIZED) So I don't see why I can't have 6 bits from that. I have no idea why the MAP_UNINITIALIZED flag was put into this strange location anyways instead of directly after the existing flags or just into one of the unused slots. I suppose I could put my bits before it, there's plenty of space. Existing flags on x86: #define MAP_SHARED 0x01 /* Share changes */ #define MAP_PRIVATE 0x02 /* Changes are private */ 4 unused 8 unused #define MAP_FIXED 0x10 /* Interpret addr exactly */ #define MAP_ANONYMOUS 0x20 /* don't use a file */ 0x40 unused #define MAP_GROWSDOWN 0x0100 /* stack-like segment */ 0x200 unused 0x400 unused #define MAP_DENYWRITE 0x0800 /* ETXTBSY */ #define MAP_EXECUTABLE 0x1000 /* mark it as an executable */ #define MAP_LOCKED 0x2000 /* pages are locked */ #define MAP_NORESERVE 0x4000 /* don't check for reservations */ #define MAP_POPULATE 0x8000 /* populate (prefault) pagetables */ #define MAP_NONBLOCK 0x10000 /* do not block on IO */ #define MAP_STACK 0x20000 /* give out an address that is best suited for process/thread stacks */ #define MAP_HUGETLB 0x40000 /* create a huge page mapping */ /* all free here: 6 bits for me? 0x80000..0x1000000 */ # define MAP_UNINITIALIZED 0x4000000 /* For anonymous mmap, memory could be uninitialized */ /* more free bits. */ Overall it seems there's no real shortage of bits. > things into protection bits, like we do with SAO (strong access > ordering) and want to do with per-page endian on embedded. mprotect already does this. Unless someone finds a good reason why this can't work I'll just move the range to 0x80000..0x1000000. -Andi -- ak@xxxxxxxxxxxxxxx -- Speaking for myself only -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>