Bug 256331

Summary:	Shuffle clobbers indirect call target in BBQ JIT
Product:	WebKit	Reporter:	David Degazio <d_degazio>
Component:	WebAssembly	Assignee:	David Degazio <d_degazio>
Status:	RESOLVED FIXED
Severity:	Normal	CC:	webkit-bug-importer
Priority:	P2	Keywords:	InRadar
Version:	WebKit Nightly Build
Hardware:	Unspecified
OS:	Unspecified

Description David Degazio 2023-05-04 13:09:02 PDT

rdar://108908936

https://bugs.webkit.org/show_bug.cgi?id=256235 removed some redundant loads and stores from the call code generation in BBQ JIT. As part of this, we now use a parallel move/shuffle to move the arguments into their intended locations per the calling convention. Shuffling can require an extra scratch register, and we currently use wasmScratchGPR.

However, the implementation of indirect calls specifically depends on the target address being kept live in wasmScratchGPR across the parameter passing. If the shuffle touches wasmScratchGPR, it will clobber this address, and likely cause a crash. We should just use a different register for shuffles in indirect calls.

Comment 1 David Degazio 2023-05-04 13:28:50 PDT

Pull request: https://github.com/WebKit/WebKit/pull/13455

Comment 2 EWS 2023-05-04 16:25:25 PDT

Committed 263697@main (c0664686f49d): <https://commits.webkit.org/263697@main>

Reviewed commits have been landed. Closing PR #13455 and removing active labels.