On 18/05/14 22:07, Omega Weapon wrote:
On 17/05/14 22:35, Omega Weapon wrote:
After many hours I have finally been able to break into X. The problem
so far is an attempt to open /dev/dri/card1, which doesnt exist -
/dev/dri/card0 is sitting there as normal. So I assume the issue is in
xf86drm.c:drmOpenByBusid somehow breaking when trying card0, and then
moving to card1. I'll look further into this tomorrow.
So far I have demonstrated drmSetInterfaceVersion failing in
drmOpenByBusId due to drmIoctl failing with EACCES - so looks like
someones screwed up the permissions with /dev/dri/card0.
Courtesy of LordVan on #radeon, there is a discrepancy with non-standard
ACL (ls -al indicates non-standard ACL stuff with a + at the end):
=======================================================
# getfacl /dev/dri/card0
getfacl: Removing leading '/' from absolute path names
# file: dev/dri/card0
# owner: root
# group: video
user::rw-
group::rw-
mask::rw-
other::---
=======================================================
On my working laptop, there is an extra 'user:omega:rw-' entry (that is
my username), however I'd like to think the general user line does this.
I added these permissions in with setfacl, but X was still broken.
I'm currently reading into kernel documentation to understand the
DRM_IOCTL_SET_VERSION ioctl in an attempt to show exactly what thinks I
don't have the access.
I'd appreciate someone with a clue helping here, as it is taking a long
time to build up some for myself.
Michel Dänzer of radeon fame has solved it - radeontop held
/dev/dri/card0 open, and from what I understand only one thing can open
this at a time. So basically radeontop held X hostage for 3 days.
For anyone facing a similar problem, here is the check to see what is
using the dri device and my actual example:
=====================================================================
# sudo lsof /dev/dri/card0
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
radeontop 4300 root 5u CHR 226,0 0t0 10510 /dev/dri/card0
Xorg 6086 root 10u CHR 226,0 0t0 10510 /dev/dri/card0
=====================================================================
As soon as I killed radeontop and sudo service lightdm start, I could
get back at my desktop.
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