Bug#910846: X server "Segmentation fault at address 0x0" when using about:support in Firefox-based browsers.

[Gong S.]

Package: xserver-xorg-video-radeon
Version: 1:18.1.0-1

I am using a standalone AMD HD 7670. "firmware-amd-graphics" is installed and loaded during boot.
It seems that whenever I tries to query information about hardware acceleration, X segfaults.
"dmesg" does not show any error or warning after segfault.
Sometimes other programs or games trigger it as well, with the same problem described in the file Xorg.0.log.

[Michel Dänzer]

Post by Gong S.
Package: xserver-xorg-video-radeon
Version: 1:18.1.0-1
I am using a standalone AMD HD 7670. "firmware-amd-graphics" is installed and loaded during boot.
It seems that whenever I tries to query information about hardware acceleration, X segfaults.
"dmesg" does not show any error or warning after segfault.
Sometimes other programs or games trigger it as well, with the same problem described in the file Xorg.0.log.

[...]

Post by Gong S.
[ 324.505] (EE) 0: /usr/lib/xorg/Xorg (OsLookupColor+0x139) [0x562764468de9]
[ 324.505] (EE) 1: /lib/x86_64-linux-gnu/libpthread.so.0 (funlockfile+0x50) [0x7f100883292f]
[ 324.506] (EE) 2: /usr/lib/xorg/modules/drivers/radeon_drv.so (_init+0x1592) [0x7f10073d4b24]
[ 324.506] (EE) 3: /usr/lib/xorg/Xorg (dri3_send_open_reply+0x55d) [0x562764438b4d]
[ 324.506] (EE) 4: /usr/lib/xorg/Xorg (drm_format_for_depth+0x93b) [0x56276443827b]
[ 324.506] (EE) 5: /usr/lib/xorg/Xorg (SendErrorToClient+0x35e) [0x56276430a97e]
[ 324.506] (EE) 6: /usr/lib/xorg/Xorg (InitFonts+0x3b6) [0x56276430e906]
[ 324.506] (EE) 7: /lib/x86_64-linux-gnu/libc.so.6 (__libc_start_main+0xe7) [0x7f1008683b17]
[ 324.506] (EE) 8: /usr/lib/xorg/Xorg (_start+0x2a) [0x5627642f867a]
[ 324.506] (EE)
[ 324.506] (EE) Segmentation fault at address 0x0

Please make sure the xserver-xorg-video-radeon-dbgsym and
xserver-xorg-core-dbgsym packages are installed, and either get a
backtrace with gdb or another log file.


Does the problem also happen without Option "AccelMethod" "EXA"? That's
the default and recommended configuration for your GPU.

[Gong S.]

There is no "xserver-xorg-video-radeon-dbgsym" or "xserver-xorg-core-dbgsym" in the repo.

[Michel Dänzer]

Post by Gong S.
There is no "xserver-xorg-video-radeon-dbgsym" or
"xserver-xorg-core-dbgsym" in the repo.

They're in a separate repository:

deb https://deb.debian.org/debian-debug/ <suite>-debug main contrib non-free

Replace <suite> with the name of the suite you're using in your main
repository entry.

[Gong S.]

Here is the output of GDB.
I am no developer, thus I do not know whether this is what you want.

[Gong S.]

Sorry, I have found the problem. If I remove this line from "/etc/X11/xorg.conf", X would not crash:
Option "DRI" "3"
So it is my fault. Sorry.

[Michel Dänzer]

Post by Gong S.
Option "DRI" "3"

If removing

Option "AccelMethod" "EXA"

as well also works, that would be the best solution for you.

Post by Gong S.
So it is my fault. Sorry.

The crash is still a bug, even though EXA & DRI3 isn't recommended,
because it can't work correctly in some cases.

Any chance you can test if the attached patch fixes the crash?

[Gong S.]

Using "glamor" instead of "EXA" works. However, the manpage says "EXA (for pre-TAHITI GPUs) and glamor (for R300 or higher)". TURKS GPUs are pre-TAHITI ones.
I cannot test the patch for you. I have said, I am no developer, and I do not want to mess up my OS by recompiling an important package.

[Michel Dänzer]

Post by Gong S.
Using "glamor" instead of "EXA" works. However, the manpage says "EXA
(for pre-TAHITI GPUs) and glamor (for R300 or higher)". TURKS GPUs
are pre-TAHITI ones.

They're also post-R300. :) The next sentence (with side note which
doesn't apply here elided) in the manpage is:

The default is glamor with R600 or newer [...], otherwise EXA.

Post by Gong S.
I cannot test the patch for you.

No problem. I'll send out the patch for review anyway, it's pretty
likely it'll fix the crash.