GUI renders but is completely unresponsive on Asahi Linux (aarch64 16K page kernel) — JavaScriptCore JIT crash

[CR0CKER]

Environment

• OS: Fedora / Asahi Linux (Apple Silicon)
• Kernel: 6.18.15-400.asahi.fc43.aarch64+16k (16K page size)
• Display: GNOME 49, Wayland
• Installation: Flatpak (Flathub) ink.whis.Whis v0.7.2
• Architecture: aarch64

Symptom

The app launches and the UI renders correctly (all buttons and layout visible), but is completely unresponsive — clicks and keyboard input have no effect. The app also cannot be quit via the window close button or tray menu (since the quit mechanism delegates to the frozen WebView via window-close-requested).

Steps to Reproduce

1. Install Whis via Flatpak on Asahi Linux (Apple Silicon Mac running Asahi/Fedora)
2. Launch the app
3. Observe: UI appears fully rendered but no interaction is possible

Root Cause

The WebKitWebProcess crashes with SIGSEGV immediately after rendering the initial UI, confirmed via coredumpctl:

$ coredumpctl list WebKitWebProces
SIGSEGV  /usr/libexec/webkit2gtk-4.1/WebKitWebProcess

Backtrace shows the crash occurs inside JIT-compiled code in anonymous mmap regions, within libjavascriptcoregtk-4.1.so:

#0  libjavascriptcoregtk-4.1.so.0 + 0xb52efc
#1  libjavascriptcoregtk-4.1.so.0 + 0xb52ebc
#2  n/a + 0x0   ← JIT-compiled anonymous memory
#3  n/a + 0x0
#4  n/a + 0x0

The GNOME Platform 49 Flatpak runtime bundles a libjavascriptcoregtk that was compiled for systems with a 4K page size. Asahi Linux uses a 16K page kernel (getconf PAGESIZE → 16384). JavaScriptCore's JIT compiler uses mmap for executable code regions with alignment and size assumptions tied to 4K pages — on 16K systems these are invalid, causing SIGSEGV on first JIT code execution.

The sequence is:

1. App starts, WebKit renders the initial Vue/HTML (no JIT needed yet)
2. JS event system initialises → JIT kicks in → WebKitWebProcess crashes
3. UI is visible (last rendered frame) but all event handlers are dead

Workaround

See follow-up comment.

Related

• Error 71 (Protocol error) dispatching to Wayland display. #43 (Wayland protocol error — different issue, different distro)
• This affects all Flatpak GTK/WebKit apps on Asahi Linux until the GNOME Platform runtime ships a 16K-page-aware WebKit build.

Note that the investigation of this issue and the workaround were done with Claude Code.

[CR0CKER]

Workaround (confirmed working)

Disable the JavaScriptCore JIT compiler at runtime using flatpak override. This forces JSC to use its interpreter instead, which has no page-size assumptions:

flatpak override --user \
  --env=JSC_useJIT=false \
  --env=WEBKIT_DISABLE_DMABUF_RENDERER=1 \
  ink.whis.Whis

• JSC_useJIT=false — disables the JIT, the WebKitWebProcess no longer crashes
• WEBKIT_DISABLE_DMABUF_RENDERER=1 — prevents a secondary crash in the DMABuf GPU compositor on Asahi's Mesa driver

Verify the overrides are applied:

flatpak override --user --show ink.whis.Whis
# [Environment]
# WEBKIT_DISABLE_DMABUF_RENDERER=1
# JSC_useJIT=false

After this, the app is fully functional. The UI responds to input and the window can be closed normally.

Note: The JIT-less interpreter is slower for heavy JS workloads, but for a transcription app UI it is imperceptible. The long-term fix is for the GNOME Platform Flatpak runtime to ship a WebKit build compiled with 16K page support — this is not specific to Whis.

Diagnosing the crash

If you hit this issue and want to confirm it's the same root cause:

# Check for WebKitWebProcess crash dumps
coredumpctl list WebKitWebProces

# Inspect backtrace — crash in anonymous mmap = JIT code
coredumpctl debug <PID> --debugger-arguments="-batch -ex 'bt 20' -ex 'quit'"

# Confirm 16K pages
getconf PAGESIZE   # → 16384 on Asahi

Note that the investigation of this issue and the workaround were done with Claude Code.