Bug 18304

Created attachment 19959 [details] [review]
proposed patch

The problem is that linux kernel introduced restrictions on /dev/mem access (ie. 2.6.27 with CONFIG_STRICT_DEVMEM turned on).

Driver sis tries to do:
    if(SISPTR(pScrn)->Primary) {
       base = xf86MapVidMem(pScrn->scrnIndex, VIDMEM_MMIO, 0, 0x2000);
       if(!base) {
          SISErrorLog(pScrn, "(Could not map BIOS scratch area)\n");
          return ret;
       }

unfortunately xf86MapVidMem() implementation for linux does bad things like:

    if (base == MAP_FAILED) {
        FatalError("xf86MapVidMem: Could not mmap framebuffer"
                   " (0x%08lx,0x%lx) (%s)\n", Base, Size,
                   strerror(errno));
    }

On linux with the restriction xservers ends its life with:

xf86MapVidMem: Could not mmap framebuffer (0x00000000,0x2000) (Operation not permitted)

while driver is fully prepared to handle case where xf86MapVidMem fails.

Proposed patch attached.