1499487 - [Mac] Failed to get Metal shader cache main folder: failed to lookup DARWIN_USER_CACHE_DIR err:5

Status: NEW

(Core :: Security: Process Sandboxing, defect, P2)

Description

[Haik Aftandilian [:haik]]

Running Nightly 64.0a1 (2018-10-16) on macOS Mojave 10.14 on a MacBook Pro (15-inch, 2018), with security.sandbox.logging.enabled=true set in about:config (requires restart), the following message is logged in the console.

Failed to get Metal shader cache main folder: failed to lookup DARWIN_USER_CACHE_DIR err:5

In some debugging done on bug 1431441, I've found that confstr(3) is used in macOS Metal code to get the cache dir and that confstr fails without read access to the symlink /var and access to the service "com.apple.system.opendirectoryd.membership".

I also tested on 10.11 and did not see the message being logged there.

We should investigate this to see if we are losing performance due to content processes not having access to the shader cache directories.