Re: mmap() with an offset > 32 bits on a 32-bit CPU

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On 00:10 Sat 28 Jun     , Abdul Basit wrote:
> 
> Hi Folks,
> 
>     I am trying to bring Xorg 7.x on PowerPC 440EPx Sequoia board, X is
> configured to use sisfb for video and the sisfb is loaded properly in
> kernel and registered as fb0, running X causes a machine check exception
> / BUS error by kernel.
> 
>      The reason for that is in :-
> 
> xorg/xorg-server/hw/xfree86/os-support/linux/lnx_video.c:558
> 
> X is doing the following :-
> 
> ----
> ioBase_phys = syscall(__NR_pciconfig_iobase, 2, 0, 0);
> fd = open("/dev/mem", O_RDWR);
>           if (ioBase == NULL) {
>                   ioBase = (volatile unsigned char *)mmap(0, 0x20000,
>                                   PROT_READ | PROT_WRITE, MAP_SHARED,
>                                  ioBase_phys);
> ----

Where do you pass the file descriptor to mmap?

> the pci I/O memory in my case is 36-bits but the CPU is 32-bits so the
> ioBase_phys is getting truncated as long is 32-bits and when later X try
> to write to this address causes a BUS error.
> 
> Since i know the ioBase_phys address which is 0x1E8000000, I could hard
> code it but the mmap(..) offset size is 32-bits as well, so I could not
> pass it as an offset.
> 
> How would i pass a large offset to mmap on PPC32? is there any other way
> to do it?

You can call mmap2 if the offset is a multiply of 4096. (see the manpage)
	-Michi
-- 
programing a layer 3+4 network protocol for mesh networks
see http://michaelblizek.twilightparadox.com


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