port-i386/59821: Segfault when trying to utilize Mesa DRI, on older Intel GPUs

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>Number:         59821
>Category:       port-i386
>Synopsis:       Segfault when trying to utilize Mesa DRI, on older Intel GPUs
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-i386-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Dec 07 18:50:00 +0000 2025
>Originator:     James Wandersee
>Release:        NetBSD 10.1 and Pkgsrc2025Q3
>Organization:
N/A
>Environment:
NetBSD 10.1 (GENERIC) #0: mkrepo%mkrepo.NetBSD.org@localhost:/usr/src/sys/arch/i386/compile/GENERIC i386
>Description:
When the DRI module is symlinked to /usr/X11R7/lib/modules/dri/mesa_dri_drivers.so(.o) attempting to utilize mesa "hardware" accelerated DRI results in segfault. This might only be affecting older Intel (I tested i915 and i945) GPUs, as I have not tested any others (outside of the Ironlake Mobile "i965"). The Ironlake did not segfault, but did run glxgears with distortion. I did not test the Ironlake against the Mesa Amber Branch, but I imagine it would run fine with it. However, please note, the Ironlake GPU (i965) did not segfault.
>How-To-Repeat:
This can be tested/repeated against the usual MesaDemo, glxgears.
>Fix:
The best fix, outside of fixing mesa_dri_drivers.so, is to install the Mesa Amber Branch, from Pkgsrc. However, either mesa_dri_drivers.so needs to be fixed to utilize the Amber Branch "if present"; or the post package installation notes should suggest that you change your dri modules symlink, to the correct DRI module provided by the package.

The included Gallium driver can be tested, by directly linking to gallium_dri.so(.0), instead of mesa_dri_drivers.so(.0). For the i915 and Ironlake Mobile (i965), glxgears ran slightly distorted. I haven't tested the my i945 with Gallium, but imagine the results would be the same.

I have not examined the (detection?) code, of mesa_dri_drives.so. I do not have a fix for it.