Messages in this thread | | | Date | Mon, 11 Oct 1999 10:32:39 -0400 | From | Harald Koenig <> | Subject | Re: mmapping of page 0xfffff000 impossible ? |
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On Oct 10, nathan.zook@amd.com wrote:
> include/asm-i386/fixmap.h > > > "Leave one empty page between vmalloc'ed areas and the start of the fixmap, > and leave one page empty at the top of mem."
this reads like that's (only?) a problem for last page in _virtual_ address space, isn't it ?
I'm looking for a method to map/read the last _physical_ page (bus addresses, actually it's a graphics card's BIOS which got mapped just below 4GB by main board's PCI BIOS configuration).
do these "compile-time 'special' virtual addresses" limitations apply to bus addresses too ?
> > I would guess that you can't map the fixmap, either. > > > Nathan > > > > -----Original Message----- > > From: root [SMTP:koenig@tat.physik.uni-tuebingen.de] > > Sent: Sunday, October 10, 1999 9:53 PM > > To: linux-kernel-list > > Cc: Egbert Eich > > Subject: mmapping of page 0xfffff000 impossible ? > > > > why isn't it possible to mmap the very last page in 32bit address space ? > > > > strace output for 2.2.12 of the small sample program below: > > open("/dev/mem", O_RDWR) = 3 > > mmap(NULL, 61440, PROT_READ, MAP_SHARED, 3, 0xffff0000) = 0x4011b000 > > mmap(NULL, 61441, PROT_READ, MAP_SHARED, 3, 0xffff0000) = -1 EINVAL > > (Invalid argument) > > > > -------------------------------------------------------------------------- > > ----- > > #include <unistd.h> > > #include <sys/mman.h> > > #include <fcntl.h> > > main() > > { > > int f; > > void *p; > > > > f = open("/dev/mem", O_RDWR); > > > > /* this will work ... */ > > p = mmap(NULL, 0xf000, PROT_READ, MAP_SHARED, f, 0xffff0000); > > > > /* this one won't :-( */ > > p = mmap(NULL, 0xf001, PROT_READ, MAP_SHARED, f, 0xffff0000); > > } > > -------------------------------------------------------------------------- > > ----- > > > > > > - > > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > > the body of a message to majordomo@vger.rutgers.edu > > Please read the FAQ at http://www.tux.org/lkml/
Harald -- All SCSI disks will from now on ___ _____ be required to send an email notice 0--,| /OOOOOOO\ 24 hours prior to complete hardware failure! <_/ / /OOOOOOOOOOO\ \ \/OOOOOOOOOOOOOOO\ \ OOOOOOOOOOOOOOOOO|// Harald Koenig, \/\/\/\/\/\/\/\/\/ Inst.f.Theoret.Astrophysik // / \\ \ koenig@tat.physik.uni-tuebingen.de ^^^^^ ^^^^^
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