Bug 167400 – Always crashed with youtube/tv on ARM platfrom

• Component: JavaScriptCore
• Status: NEW

[Mark Wang]

When loading www.youtube.com/tv, the crash always happens if playing anyone of videos. My runing environment is:
1/ ARM platfrom.
2/ webkitgtk-2.12.2
3/ JIT is disabled.

It can't be reproduced on other platforms, like mips.

[Mark Wang]

The crash is caused by DataView.getFloat32(). On ARM platform, DataView.getFloat32() requires an aligned address, otherwise, it causes crash.

[Mark Wang]

Created attachment 299661 [details]
the patch to fix this issue.

the patch is verified on ARM platform. It can fix the crash issue.

[Alexey Proskuryakov]

Do you observe the crash when compiling with gcc?

[Mark Wang]

(In reply to comment #3)
> Do you observe the crash when compiling with gcc?

When compiling JSDataViewPrototype.cpp, no any error or warninngs is outputed in the console. 

In fact, DataView.getFloat32() could read a float from the buffer with any offset. The compiler can't know the offset for the alignment.

[Keith Miller]

This fix looks reasonable but we should just skip the #ifs and just use the memcpy version on all platforms. The compiler should convert the memcpy into a load on platforms where they are equivalent anyway. I would just add a comment saying that the load may not be aligned so we use memcpy to implement the load.

[Mark Lam]

(In reply to comment #5)
> This fix looks reasonable but we should just skip the #ifs and just use the
> memcpy version on all platforms. The compiler should convert the memcpy into
> a load on platforms where they are equivalent anyway. I would just add a
> comment saying that the load may not be aligned so we use memcpy to
> implement the load.

Also, please add a ChangeLog.  See https://webkit.org/contributing-code/ for more details.