I built Xorg from source so I could get debugging symbols. The crash is in xf86VGAarbiterInit(), when it calls pci_device_vgaarb_init(). This function can read /dev/vga_arbiter which ordinary users cannot.
# head -1 < /dev/vga_arbiter count:1,PCI:0000:65:00.0,decodes=io+mem,owns=none,locks=none(0:0) pci_sys->devices is null. The problem appears to be a bad scan format in line 160 of linux_sysfs.c sscanf(devices[i]->d_name, "%04x:%02x:%02x.%1u", ls /sys/bus/pci/devices shows devices with a BUS > 0xffff taking 5 digits. ls /sys/bus/pci/devices 0000:00:00.0 0000:00:1f.2 0000:16:0e.4 0000:64:09.0 0000:64:0d.1 0000:00:04.0 0000:00:1f.3 0000:16:0e.5 0000:64:0a.0 0000:64:0d.2 0000:00:04.1 0000:00:1f.4 0000:16:0e.6 0000:64:0a.1 0000:64:0d.3 0000:00:04.2 0000:00:1f.6 0000:16:0e.7 0000:64:0a.2 0000:65:00.0 0000:00:04.3 0000:02:00.0 0000:16:0f.0 0000:64:0a.3 0000:65:00.1 0000:00:04.4 0000:16:05.0 0000:16:0f.1 0000:64:0a.4 0000:b2:05.0 0000:00:04.5 0000:16:05.2 0000:16:1d.0 0000:64:0a.5 0000:b2:05.2 0000:00:04.6 0000:16:05.4 0000:16:1d.1 0000:64:0a.6 0000:b2:05.4 0000:00:04.7 0000:16:08.0 0000:16:1d.2 0000:64:0a.7 0000:b2:05.5 0000:00:05.0 0000:16:08.1 0000:16:1d.3 0000:64:0b.0 0000:b2:12.0 0000:00:05.2 0000:16:08.2 0000:16:1e.0 0000:64:0b.1 0000:b2:12.1 0000:00:05.4 0000:16:08.3 0000:16:1e.1 0000:64:0b.2 0000:b2:12.2 0000:00:08.0 0000:16:08.4 0000:16:1e.2 0000:64:0b.3 0000:b2:15.0 0000:00:08.1 0000:16:08.5 0000:16:1e.3 0000:64:0c.0 0000:b2:16.0 0000:00:08.2 0000:16:08.6 0000:16:1e.4 0000:64:0c.1 0000:b2:16.4 0000:00:14.0 0000:16:08.7 0000:16:1e.5 0000:64:0c.2 0000:b2:17.0 0000:00:14.2 0000:16:09.0 0000:16:1e.6 0000:64:0c.3 10000:00:02.0 0000:00:16.0 0000:16:09.1 0000:64:00.0 0000:64:0c.4 10000:00:03.0 0000:00:17.0 0000:16:0e.0 0000:64:05.0 0000:64:0c.5 10000:01:00.0 0000:00:1c.0 0000:16:0e.1 0000:64:05.2 0000:64:0c.6 0000:00:1c.6 0000:16:0e.2 0000:64:05.4 0000:64:0c.7 0000:00:1f.0 0000:16:0e.3 0000:64:08.0 0000:64:0d.0 -- Dr Peter Chubb Tel: +61 2 9490 5852 http://ts.data61.csiro.au/ Trustworthy Systems Group Data61 (formerly NICTA)