Add x86_on_x64 option, which enables x86 mixed-mode on x64. (i#49)

Reviewer: bruening@google.com
Add x86_on_x64 option, which enables x86 mixed-mode on x64. (i#49)

Add x86_on_x64 option, which enables x86 mixed-mode on x64. (i#49)

[bruening, 2012-06-29 14:36:31]

http://codereview.appspot.com/6343056/diff/1/trunk/core/win32/os.c
File trunk/core/win32/os.c (right):

http://codereview.appspot.com/6343056/diff/1/trunk/core/win32/os.c#newcode1962
trunk/core/win32/os.c:1962: * ntdll32.dll at early inject point, so thread
injection only.  PR 215423.
can you update the comment: this is only true for pre-vista (xref i#381)

http://codereview.appspot.com/6343056/diff/1/trunk/core/win32/os.c#newcode1965
trunk/core/win32/os.c:1965: (DYNAMO_OPTION(x86_on_x64) ||
!is_wow64_process(process_handle))) {
this happens to work on vista+ b/c it turns out ntdll32 is mapped in by the
kernel.  but it will fail on xp64/2003 (until have a delayed hook in place). 
need to update the option to reflect that.  and actually since it works on
vista+ maybe the default there should be early injection for wow64.  I guess I'm
wondering whether we need an option at all: just change these checks to look for
vista+.  user can always use -no_early_inject to request late injection on
vista+.

http://codereview.appspot.com/6343056/diff/1/trunk/core/win32/os.c#newcode2041
trunk/core/win32/os.c:2041: * ntdll32.dll at early inject point, so thread
injection only.  PR 215423.
can you update the comment: this is only true for pre-vista (xref i#381)

http://codereview.appspot.com/6343056/diff/1/trunk/core/win32/os.c#newcode2044
trunk/core/win32/os.c:2044: if (DYNAMO_OPTION(x86_on_x64) ||
this should be down in the !is_wow64_process sub-clause

http://codereview.appspot.com/6343056/diff/1/trunk/core/win32/os.c#newcode2049
trunk/core/win32/os.c:2049: (cxt != NULL &&
is_first_thread_in_new_process(process_handle, cxt))) {
I don't think you need the x86_on_x64 check here for Vista+ b/c cxt!=NULL at
CreateUserProcess syscall: but b/c you did add it I assume you hit a problem? 
probably it was really i#816 which I fixed where is_first_thread* was wrong.  so
in the end I don't think you need any changes here at all but I would re-arrange
the cxt==NULL logic to reflect vista not caring whether it's wow64

[bruening, 2012-06-29 16:03:56]

can you update the other comment too (see 1st set of diff suggestions)

[bruening, 2012-06-29 16:59:38]

LGTM

[bruening, 2012-06-29 16:59:54]

On 2012/06/29 16:59:38, bruening wrote:
> LGTM

Don't forget to update the commit message