Add basic infrastructure for protecting V8's heap when leaving the VM...

Add basic infrastructure for protecting V8's heap when leaving the VM
and unprotecting it when (re)entering.  The functionality is enabled
by the flag --protect-heap and requires V8 to be built with
ENABLE_HEAP_PROTECTION and ENABLE_LOGGING_AND_PROFILING defined.

Implemented on Linux and Windows but not yet for other platforms.


Committed: http://code.google.com/p/v8/source/detail?r=1595

[Kevin Millikin (Chromium), 2009-03-24 09:25:56]

This is a first step.  Transitioning into or out of state EXTERNAL triggers heap
protection/unprotection.

There is no code in V8 yet that causes that state transition.  The next step is
to identify the places in the API and runtime (eg, callbacks) where we need to
go into the EXTERNAL state.

[Erik Corry, 2009-03-24 10:02:36]

LGTM

http://codereview.chromium.org/53004/diff/28/1011
File src/heap.h (right):

http://codereview.chromium.org/53004/diff/28/1011#newcode276
Line 276: #ifdef ENABLE_LOGGING_AND_PROFILING
I'd like to hide behind a different ifdef for performance reasons.  This one is
on in released Chrome.

http://codereview.chromium.org/53004/diff/28/1008
File src/platform-linux.cc (right):

http://codereview.chromium.org/53004/diff/28/1008#newcode263
Line 263: void OS::Protect(void* address, size_t size) {
This could call VirtualMemory::Protect or vice versa.

http://codereview.chromium.org/53004/diff/28/1008#newcode464
Line 464: void VirtualMemory::Protect(void* address, size_t size) {
Perhaps assert that we are aligned with page boundaries?

http://codereview.chromium.org/53004/diff/28/1009
File src/platform-macos.cc (right):

http://codereview.chromium.org/53004/diff/28/1009#newcode255
Line 255: 
not yet implemented?

[Kevin Millikin (Chromium), 2009-03-24 11:42:43]

http://codereview.chromium.org/53004/diff/31/1022
File src/spaces.h (right):

http://codereview.chromium.org/53004/diff/31/1022#newcode1641
Line 1641: #ifdef ENABLE_LOGGING_AND_PROFILING
Ooops.  Fixed.

[Søren Thygesen Gjesse, 2009-03-24 11:43:55]

LGTM

I also like the cleanup of parameter names etc.

http://codereview.chromium.org/53004/diff/31/1028
File src/log.cc (right):

http://codereview.chromium.org/53004/diff/31/1028#newcode1128
Line 1128: // Are we leaving V8?
ASSERT that previous state was not EXTERNAL and likewise for the other state
changes to/from EXTERNAL.

http://codereview.chromium.org/53004/diff/31/1026
File src/platform-linux.cc (right):

http://codereview.chromium.org/53004/diff/31/1026#newcode256
Line 256: // TODO(1240712): munmap has a return value which is ignored here.
Move this issue to code.google.com/p/v8.

[Erik Corry, 2009-03-24 12:32:31]

LGTM