1930384 - add missing BTI asm instruction to xpcom aarch64 stubs

Status: RESOLVED FIXED

(Core :: XPCOM, enhancement)

Description

[Landry Breuil (:gaston)]

BTI is enforced by default on OpenBSD, and on hardware that supports it firefox crashes at start. For now to have a working firefox on such hardware we need to link with BTI support disabled, thus we don't benefit from the security feature it brings. Cf https://undeadly.org/cgi?action=article;sid=20230714121907 and https://www.undeadly.org/cgi?action=article;sid=20240222183703 for the background on it.

The disasm in gdb points at the asm in https://searchfox.org/mozilla-central/source/xpcom/reflect/xptcall/md/unix/xptcstubs_aarch64.cpp#227

adding a 'bti c' asm instruction there allows the binary to make more progress, and a build with --disable-jit (support for BTI in spidermonkey/the JIT is being worked on by another OpenBSD developer) even works/is usable on the OmniBook X14 which has hardware support for the BTI instruction.

i have to recheck that it causes no fallback on aarch64 hardware that doesnt support the BTI instruction.

Comment 1

[Landry Breuil (:gaston)]

Attachment: Bug 1930384 - add missing BTI instruction in aarch64 C stubs r?nika

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/d76870072e98
add missing BTI instruction in aarch64 C stubs r=nika

Comment 3

[Norisz Fay [:noriszfay]]

https://hg.mozilla.org/mozilla-central/rev/d76870072e98