#40 android: build the Xwayland glamor stack from upstream Mesa 26.2.6

Moves the Xwayland glamor Mesa stack off the old fork base (Mesa 25.0.0-devel, build-xwayland @ 81f599c0d7) onto upstream mesa-26.2.6, the newest 26.x stable tag. The base branch upstream-26.2.6 is the plain upstream tag, so the diff here is only our commits. The idea is that this replaces build-xwayland as the source of the glamor stage in the gamescope payload.

Why

Under gamescope on kernels older than 6.0 (Retroid Flip 2 / SD865 on 4.19, Thor / 8 Gen 2 on 5.15), Xwayland leaks one dma-buf fd per image barrier. The 25.0-devel zink_screen_export_dmabuf_semaphore() returns without close(fd) when DMA_BUF_IOCTL_EXPORT_SYNC_FILE fails with ENOTTY. After roughly 50 s Xwayland hits EMFILE: logcat fills with MESA: Unable to get a valid memory fd, then zink: couldn't allocate memory and Error getting buffer, and the picture freezes while the game keeps running. Upstream fixed this in de4224a57cc. 26.2.6 has it: the fd is closed right after the ioctl, so no cherry-pick is needed.

What moved

• android: minimal LLVM-free glamor Mesa stack with gndrm support (Joshua's commit, re-ported):
  • android/ build recipe, overlays and README: unchanged.
  • gbm.c: gbm_create_device() accepts the gndrm socket fd when DRM_IOCTL_VERSION says "gamenative". Unchanged.
  • loader.c: the gndrm fd counts as render capable and defaults to zink. Unchanged.
  • backend.c: the GBM backend dir is resolved at runtime as the gbm/ sibling of libgbm. Unchanged.
  • src/meson.build: dril is built for GBM-only builds. Re-applied on 26.2's condition, which no longer has with_platform_xcb.
  • pipe-loader part: dropped. Upstream removed the dynamic pipe-loader (PIPE_SEARCH_DIR and gallium-pipe no longer exist), so there was nothing left to apply it to.
• android: build the glamor Mesa stack with ELF TLS: clean cherry-pick.
• android: build the glamor stack on 26.2 from Linux or macOS:
  • Drops the meson options 26.2 removed (gallium-vdpau, gallium-xa, gallium-opencl, gallium-nine, osmesa, install-intel-clc).
  • Picks the NDK prebuilt dir from uname -s and takes bison/flex from PATH (macOS /usr/bin/bison is 2.3).
  • Uses wc -c instead of GNU du -b.
• zink: name command buffers only when tracing or capturing: new, a workaround.
  • Since 82656de0297b, zink labels its batch command buffers with vkSetDebugUtilsObjectNameEXT.
  • Under gamescope, Xwayland reaches the container's adrenotools Turnip through gn-vkshim's proxy. The proxy returns its own wrapper objects as VkCommandBuffer handles and passes vkSetDebugUtilsObjectNameEXT straight through. Turnip then reads the wrapper as a vk_object_base.
  • Tombstone on the Tab S7: SEGV at 0x58 in Turnip v26.2.0 R4/libvulkan_freedreno.so, reached via create_batch_state → zink_start_batch → zink_context_create → eglCreateContext. Xwayland never comes up.
  • The commit sets the names only when zink_tracing or RenderDoc is active, the same conditions zink already uses for its other debug labels.
  • It can be dropped once the shim unwraps the handle in vkSetDebugUtilsObjectNameEXT.

Stage

Built on macOS with NDK r27d against the termux-on-gha build-20260218 prefix (only include/, libdrm and the glvnd libs are needed). Output:

• lib/libgallium-26.2.6.so
• lib/libEGL_mesa.so.0
• lib/libgbm.so.1
• lib/gbm/dri_gbm.so
• lib/dri/libdril_dri.so
• share/glvnd/egl_vendor.d/50_mesa.json

Notes on the output:

• No emulated TLS, 16 KB LOAD alignment, no libandroid, no build-host paths.
• There is no libglapi.so.0 any more: glapi has lived in libgallium since 25.1, and the TLS symbol is now _mesa_glapi_tls_Context.
• libgallium now links the system libz.so instead of termux libz.so.1.
• When this ships, package-gamescope.sh needs MESA_STAGE_SONAMES updated: libgallium-26.2.6.so, and no libglapi.so.0.

Testing

Galaxy Tab S7 (Adreno 650, Android 11, kernel 4.19) on BrowserStack App Live, Legacy testbed build, wrappertest gl/ with WT_GL_HOLD_SEC=300 under gamescope. The test payloads are the shipped gamescope-gamenative-20261028.4 with only the glamor Mesa files swapped.

payload	workload	result	Unable to get a valid memory fd / couldn't allocate memory / Error getting buffer
shipped 20261028.4	gl/ hold 300 s	PASS 12/0, about 27 fps	0 / 0 / 0
shipped 20261028.4	TestD3D (DXVK) 300 s	rendered, 59.7 fps, exit 0	0 / 0 / 0
browserstack/gamescope-glamor-upstream-4afc4a1-base20261028.4.tzst (without the zink commit)	gl/	Xwayland SEGV at start-up	n/a
browserstack/gamescope-glamor-upstream-af7b88f-base20261028.4.tzst	gl/ hold 300 s	PASS 12/0, 27.5 fps, window visible and still updating at the end	0 / 0 / 0
same	TestD3D (DXVK) 300 s	rendered, 59.8 fps, exit 0	0 / 0 / 0

On the Tab S7 the leak does not reproduce with these workloads, even on the shipped payload. So this run shows the 26.2.6 stack works there with no regression; it does not prove the leak is gone. That still needs a run on an affected device (Flip 2 or Thor with a GL/sprite game, where the freeze showed after about 50 s). The fd count could not be read on App Live, because its shell does not allow ps or /proc.

Test payload: https://downloads.gamenative.app/browserstack/gamescope-glamor-upstream-af7b88f-base20261028.4.tzst, 14371338 bytes, sha256 c505e63cd1b714c07964a10d4ccea111e6030252c966096fb4a05b78d762c0d2.