Package: libglx-mesa0
Followup-For: Bug #1092890
X-Debbugs-Cc: mitya57@debian.org

Dear Maintainer, Dmitry,

This is conjecture, but I wondered whether an adjustment to the meson linkage options for libgallium_dri[1] around the same time (not contained in the same commit, but chronologically nearby) could be relevant. In particular, libdri moved into link_whole, although libswdri did not.

(it may not matter at all; I've no idea why a change to that would only affect a single architecture, for example. but it's something I noticed while puzzling over possible causes, so I thought I'd mention it)

Regards,
James

[1] - https://sources.debian.org/src/mesa/24.3.4-2/src/gallium/targets/dri/meson.build/?hl=60#L60

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Hi James!

On Wed, Jan 29, 2025 at 01:43:31AM +0000, James Addison wrote:

Dear Maintainer, Dmitry,

This is conjecture, but I wondered whether an adjustment to the meson linkage options for libgallium_dri[1] around the same time (not contained in the same commit, but chronologically nearby) could be relevant. In particular, libdri moved into link_whole, although libswdri did not.

I tried moving libswdri to link_whole as well, but it did not change anything unfortunately. And reverting 212d57f7e6701a4f307c2c049a0e3eccfce58965 is not possible, because there are conflicts in all three files.

In other news, I tried to use different linkers and linker options. With all linkers, it crashes, but in a bit different ways:

- bfd (default): jump happens to stderr().

- gold: jump happens to some incorrect place in libgallium-24.3.4.so:
https://paste.debian.net/1347044/
https://paste.debian.net/1347045/

- lld: jump happens to 0x0.

- bfd with -Wl,-z,now: *** stack smashing detected *** but in the same
location, when attempting to do driSwapBuffers(pdraw->dri_drawable).

Also I tried a different compiler (clang), and did not notice any difference compared to gcc.

In case someone else wants to take a look at this, here is how I test it:

1. Clone upstream repo and enter the directory:
$ git clone --depth 1 https://gitlab.freedesktop.org/mesa/mesa.git -b 24.3
$ cd mesa

2. Configure mesa (see [1] on details how to pass a different compiler or options):
$ meson setup build

3. Build mesa (pass -v to see full command lines):
$ ninja -C build

4. Install mesa locally:
$ meson install -C build --destdir=~/mesa-install

5. Get qtlocation package source:
$ cd ~
$ dget -ux https://deb.debian.org/debian/pool/main/q/qtlocation-opensource-src/qtlocation-opensource-src_5.15.15+dfsg-3.dsc

6. Run the build until it fails:
$ cd qtlocation-opensource-src-5.15.15+dfsg
$ dpkg-buildpackage -jauto

7. Enter the test directory:
$ cd tests/auto/declarative_ui

8. Set LD_LIBRARY_PATH environment variable:
$ export LD_LIBRARY_PATH=~/qtlocation-opensource-src-5.15.15+dfsg/lib:~/mesa-install/usr/local/lib/powerpc64le-linux-gnu

9. Enter Xvfb environment:
$ xvfb-run -a -s "-screen 0 1024x768x24 +extension RANDR +extension RENDER +extension GLX" bash

10. Run the test:
$ ./tst_declarative_ui -import ~/qtlocation-opensource-src-5.15.15+dfsg/qml

Steps 5 and 6 can be done once, no need to repeat them between tests.

[1]: https://docs.mesa3d.org/meson.html#compiler-options

--
Dmitry Shachnev

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On Wed, Jan 29, 2025 at 11:54:34PM +0300, Dmitry Shachnev wrote:

In other news, I tried to use different linkers and linker options. With all linkers, it crashes, but in a bit different ways:

- bfd (default): jump happens to stderr().

- gold: jump happens to some incorrect place in libgallium-24.3.4.so:
https://paste.debian.net/1347044/
https://paste.debian.net/1347045/

- lld: jump happens to 0x0.

- bfd with -Wl,-z,now: *** stack smashing detected *** but in the same
location, when attempting to do driSwapBuffers(pdraw->dri_drawable).

Also I tried a different compiler (clang), and did not notice any difference compared to gcc.

In case someone else wants to take a look at this, here is how I test it: [...]

First, I found an easier way to reproduce this issue. Installing mesa-utils package and running "xvfb-run -a glxgears" is enough to trigger it.

Second, I noticed that building without -DUSE_PPC64LE_ASM makes the issue
go away. Maybe there is some problem with the assembly (entry_ppc64le_tls.h) but I can’t say what exactly. Anyway, I submitted a merge request to disable assembly for now: https://salsa.debian.org/xorg-team/lib/mesa/-/merge_requests/52

Dear Debian powerpc porters, if someone has an idea what happens here and whether it can be fixed in a better way, any help would be welcome! Please see my previous comments on this bug for more details.

--
Dmitry Shachnev

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