Lion x86 compatibility for mach_override

Lion x86 compatibility for mach_override.

This enables makeIslandExecutable for x86. Main executables linked and run on
Mac OS X 10.7 ("Lion") have non-executable heap pages by default.

BUG=79642
TEST=Build and run on Lion. Renderers should not crash instantly.
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=93690

[Mark Mentovai, 2011-07-22 16:12:52]

I’ll send this upstream once committed to our repository.

Robert, could you verify that this works on Lion?

[Nico, 2011-07-22 16:14:32]

LGTM

:-/

[Mark Mentovai, 2011-07-22 16:15:20]

Why the angly face, thakis?

[Nico, 2011-07-22 16:18:09]

'cause I broke renderers on lion

On Fri, Jul 22, 2011 at 9:15 AM,  <mark@chromium.org> wrote:
> Why the angly face, thakis?
>
> http://codereview.chromium.org/7492012/
>

[Nico, 2011-07-22 16:18:29]

I'M SOWWY

On Fri, Jul 22, 2011 at 9:18 AM, Nico Weber <thakis@chromium.org> wrote:
> 'cause I broke renderers on lion
>
> On Fri, Jul 22, 2011 at 9:15 AM,  <mark@chromium.org> wrote:
>> Why the angly face, thakis?
>>
>> http://codereview.chromium.org/7492012/
>>
>

[Mark Mentovai, 2011-07-22 16:23:24]

Not for everyone, only for those suffering through doing builds on Lion.
Basically just Robert, I guess.

[Robert Sesek, 2011-07-22 16:26:41]

Getting this:

[5566:1031:76645417214358:FATAL:renderer_main.cc(63)] Check failed:
(mach_error_t)0 == err (0 vs. -134217727)
Backtrace:
	0   Chromium Framework                  0x0136d92e
base::debug::StackTrace::StackTrace() + 60
	1   Chromium Framework                  0x0139a36b
logging::LogMessage::~LogMessage() + 69
	2   Chromium Framework                  0x04ab219b (anonymous
namespace)::InstallFrameworkHacks() + 201
	3   Chromium Framework                  0x04ab222b
RendererMain(MainFunctionParams const&) + 115
	4   Chromium Framework                  0x00008a06 (anonymous
namespace)::RunNamedProcessTypeMain(std::string const&, MainFunctionParams
const&) + 126
	5   Chromium Framework                  0x000086bc ChromeMain + 4154
	6   Chromium Helper                     0x00001f84 main + 58
	7   Chromium Helper                     0x00001f0d start + 53

[Robert Sesek, 2011-07-22 16:27:03]

Also, is it safe to enable this for i386 binaries on OS<Lion?

[Mark Mentovai, 2011-07-22 16:32:48]

I’ll fix this.

Yes, this is safe to enable pre-10.7. Those pages were already marked in the
hardware page table the same way that this function requests them to be marked
now. Skipping it on x86 was just a tiny optimization that makes sense when the
pages are known to be executable.

Strictly speaking, we need to do this on pre-10.7 as well, because the same
behavior that is now the default on Lion can be triggered on pre-Lion if someone
changes the value of the vm.allow_data_exec sysctl (to 0, for example).

[Mark Mentovai, 2011-07-22 18:51:41]

The CHECK failure Robert saw was because this was trying to mprotect an unmapped
page (NULL). Since we’re calling mach_override_ptr with a NULL third argument,
there is no reentry island.

I fixed a couple of other bugs while I was working on this one. Details in
README.chromium. I’ll still upstream this all.

Robert, another try?

[Robert Sesek, 2011-07-22 19:06:28]

Works for me -> LGTM