OSAllocatorPosix::tryReserveUncommittedAligned() should not use PROT_NONE on non-linux platforms

• Component: Platform
• Status: NEW ---

[Yoshiaki Jitsukawa]

OSAllocatorPosix::tryReserveUncommittedAligned() should not use PROT_NONE on non-linux platforms.

Only on linux PROT_NONE is used for deccommitted pages. That is, protection flags are set on commit() only on Linux. 
https://github.com/WebKit/WebKit/blob/9067a50/Source/WTF/wtf/posix/OSAllocatorPOSIX.cpp#L228

However in tryReserveUncommittedAligned() PROT_NONE is used for platforms other than
 #if PLATFORM(MAC) || USE(APPLE_INTERNAL_SDK),
which may result in protection faults because appropriate flags won't be set on commit().

[Basuke Suzuki]

(In reply to Yoshiaki Jitsukawa from comment #0)
> OSAllocatorPosix::tryReserveUncommittedAligned() should not use PROT_NONE on
> non-linux platforms.
> 
> Only on linux PROT_NONE is used for deccommitted pages. That is, protection
> flags are set on commit() only on Linux. 
> https://github.com/WebKit/WebKit/blob/9067a50/Source/WTF/wtf/posix/
> OSAllocatorPOSIX.cpp#L228
> 
> However in tryReserveUncommittedAligned() PROT_NONE is used for platforms
> other than
>  #if PLATFORM(MAC) || USE(APPLE_INTERNAL_SDK),
> which may result in protection faults because appropriate flags won't be set
> on commit().

Linux implementation is so much depends on Linux memory management way and very different from other port.

[Radar WebKit Bug Importer]

<rdar://problem/89317522>