Add x64 version of getcontext.

Add x64 version of getcontext.

Assembly code is derived in part from code in libunwind.
Code tested on desktop linux (Android testing pending emulation
support).

BUG=346626

[Lei Zhang (chromium)]

Make sure using libunwind is ok.

lgtm, with nits.

https://breakpad.appspot.com/1454002/diff/1/common/android/breakpad_getcontext.S
File common/android/breakpad_getcontext.S (right):

https://breakpad.appspot.com/1454002/diff/1/common/android/breakpad_getcontex...
common/android/breakpad_getcontext.S:333: WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.  */
nit: add a newline separator.

https://breakpad.appspot.com/1454002/diff/1/common/android/breakpad_getcontex...
common/android/breakpad_getcontext.S:352: restores them, so don't restore
garbage).  */
nit: weird indentation, same belo on line 362.

https://breakpad.appspot.com/1454002/diff/1/common/android/include/sys/uconte...
File common/android/include/sys/ucontext.h (right):

https://breakpad.appspot.com/1454002/diff/1/common/android/include/sys/uconte...
common/android/include/sys/ucontext.h:221: uint32_t padding[24]; //  96 bytes
nit: 2 spaces before comments.

https://breakpad.appspot.com/1454002/diff/1/common/android/include/sys/user.h
File common/android/include/sys/user.h (right):

https://breakpad.appspot.com/1454002/diff/1/common/android/include/sys/user.h...
common/android/include/sys/user.h:155: __u16            cwd;
nit: collapse the spacing.

https://breakpad.appspot.com/1454002/diff/1/common/android/ucontext_constants.h
File common/android/ucontext_constants.h (right):

https://breakpad.appspot.com/1454002/diff/1/common/android/ucontext_constants...
common/android/ucontext_constants.h:111: #define MCONTEXT_GREGS_OFFSET     0x28
nit: Use decimal instead of hexidecimal like the rest of the file.

[anton]

https://breakpad.appspot.com/1454002/diff/1/common/android/breakpad_getcontext.S
File common/android/breakpad_getcontext.S (right):

https://breakpad.appspot.com/1454002/diff/1/common/android/breakpad_getcontex...
common/android/breakpad_getcontext.S:333: WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.  */
On 2014/04/09 19:57:04, Lei Zhang (chromium) wrote:
> nit: add a newline separator.

Done.

https://breakpad.appspot.com/1454002/diff/1/common/android/breakpad_getcontex...
common/android/breakpad_getcontext.S:352: restores them, so don't restore
garbage).  */
On 2014/04/09 19:57:04, Lei Zhang (chromium) wrote:
> nit: weird indentation, same belo on line 362.

Done.

https://breakpad.appspot.com/1454002/diff/1/common/android/include/sys/uconte...
File common/android/include/sys/ucontext.h (right):

https://breakpad.appspot.com/1454002/diff/1/common/android/include/sys/uconte...
common/android/include/sys/ucontext.h:221: uint32_t padding[24]; //  96 bytes
On 2014/04/09 19:57:04, Lei Zhang (chromium) wrote:
> nit: 2 spaces before comments.

Done.

https://breakpad.appspot.com/1454002/diff/1/common/android/include/sys/user.h
File common/android/include/sys/user.h (right):

https://breakpad.appspot.com/1454002/diff/1/common/android/include/sys/user.h...
common/android/include/sys/user.h:155: __u16            cwd;
On 2014/04/09 19:57:04, Lei Zhang (chromium) wrote:
> nit: collapse the spacing.

Done.

https://breakpad.appspot.com/1454002/diff/1/common/android/ucontext_constants.h
File common/android/ucontext_constants.h (right):

https://breakpad.appspot.com/1454002/diff/1/common/android/ucontext_constants...
common/android/ucontext_constants.h:111: #define MCONTEXT_GREGS_OFFSET     0x28
On 2014/04/09 19:57:04, Lei Zhang (chromium) wrote:
> nit: Use decimal instead of hexidecimal like the rest of the file.

Done.

[dannyb]

lgtm

[rmcilroy]

On 2014/04/11 15:14:14, dannyb wrote:
> lgtm

I will land this for anton.

[anton]

On 2014/04/11 16:12:29, rmcilroy wrote:
> On 2014/04/11 15:14:14, dannyb wrote:
> > lgtm
> 
> I will land this for anton.

Thanks Ross for landing. Will close issue.