Refactor and cleanup VirtualMemory.

Refactor and cleanup VirtualMemory.

Remove a lot of platform duplication, and simplify the virtual
memory implementation. Also improve readability by avoiding bool
parameters for executability (use a dedicated Executability type
instead).

Get rid of the Isolate::UncheckedCurrent() call in the platform
code, as part of the Isolate TLS cleanup.

Use a dedicated random number generator for the address
randomization, instead of messing with the per-isolate random
number generators.

TEST=cctest/test-virtual-memory
R=verwaest@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=16637

[Benedikt Meurer, 2013-09-10 13:34:38]

Hey Toon,
Here's the VirtualMemory refactoring, as promised. :-)
Mostly mechanical, PTAL.
-- Benedikt

[Toon Verwaest, 2013-09-10 15:11:40]

lgtm with nits

https://codereview.chromium.org/23641009/diff/4001/src/platform/virtual-memor...
File src/platform/virtual-memory.cc (right):

https://codereview.chromium.org/23641009/diff/4001/src/platform/virtual-memor...
src/platform/virtual-memory.cc:171: // After three attempts give up and let the
kernel find and address.
find an address

https://codereview.chromium.org/23641009/diff/4001/src/platform/virtual-memor...
src/platform/virtual-memory.cc:454: bool VirtualMemory::ProtectRegion(void*
address, size_t size) {
I'd prefer a more descriptive name here. Maybe WriteProtectRegion? And if it's
called that way, could we mask out the write-bit rather than making whatever you
call this with executable?

https://codereview.chromium.org/23641009/diff/4001/src/platform/virtual-memory.h
File src/platform/virtual-memory.h (right):

https://codereview.chromium.org/23641009/diff/4001/src/platform/virtual-memor...
src/platform/virtual-memory.h:42: // object by assignment or copy-contructing.
This removes the reserved memory
constructing

https://codereview.chromium.org/23641009/diff/4001/src/platform/virtual-memor...
src/platform/virtual-memory.h:127: // to them will cause a processor exception
then.
remove "then" at the end. Reindent.

[Benedikt Meurer, 2013-09-11 08:47:42]

Committed patchset #3 manually as r16637 (presubmit successful).

[Benedikt Meurer, 2013-09-11 09:38:08]

https://codereview.chromium.org/23641009/diff/4001/src/platform/virtual-memor...
File src/platform/virtual-memory.cc (right):

https://codereview.chromium.org/23641009/diff/4001/src/platform/virtual-memor...
src/platform/virtual-memory.cc:171: // After three attempts give up and let the
kernel find and address.
On 2013/09/10 15:11:41, Toon Verwaest wrote:
> find an address

Done.

https://codereview.chromium.org/23641009/diff/4001/src/platform/virtual-memor...
src/platform/virtual-memory.cc:454: bool VirtualMemory::ProtectRegion(void*
address, size_t size) {
On 2013/09/10 15:11:41, Toon Verwaest wrote:
> I'd prefer a more descriptive name here. Maybe WriteProtectRegion? And if it's
> called that way, could we mask out the write-bit rather than making whatever
you
> call this with executable?

Done. I think we will replace this method with a better alternative once we can
write protect the code areas in the heap. Until then we'll stick to
WriteProtectRegion().

https://codereview.chromium.org/23641009/diff/4001/src/platform/virtual-memory.h
File src/platform/virtual-memory.h (right):

https://codereview.chromium.org/23641009/diff/4001/src/platform/virtual-memor...
src/platform/virtual-memory.h:42: // object by assignment or copy-contructing.
This removes the reserved memory
On 2013/09/10 15:11:41, Toon Verwaest wrote:
> constructing

Done.

https://codereview.chromium.org/23641009/diff/4001/src/platform/virtual-memor...
src/platform/virtual-memory.h:127: // to them will cause a processor exception
then.
On 2013/09/10 15:11:41, Toon Verwaest wrote:
> remove "then" at the end. Reindent.

Done.