vDSO reference parser updates and Go workaround

Patches 1 and 2 update the vDSO reference parser.

Despite the late submission, this might be 3.16 material: it's just documentation. If I'd been more on top of this, I would have done it for 3.15. It's also probably worthwhile given that there is at least one rather buggy vDSO parser in the wild.

Patches 3 and 4 make "Hello world" as built by Go stop segfaulting. It's a performance regression for Go programs: it causes them to stop finding any symbols in the vDSO, but that's a lot better than segfaulting.

Changes from v1:
- Improve portability of the vdso parser.
- Add an explicit ELFCLASS check in the vdso parser (why not?).
- Fix x32 build.
- Add a comment describing what the hack works around, why, and where the Go bug was introduced.

Changes from v2: Re-add patch 1. Whoops.

Andy Lutomirski (4):
doc,vdso: Rename vdso_test.c to vdso_standalone_test_x86.c doc,vdso: Make vDSO examples more portable x86,vdso: Add PUT_LE to store little-endian values x86,vdso: Hack to keep 64-bit Go programs working

 Documentation/vDSO/parse_vdso.c               |  67 ++++++++------
 Documentation/vDSO/vdso_standalone_test_x86.c | 128 ++++++++++++++++++++++++++
 Documentation/vDSO/vdso_test.c                | 107 +++++----------------
 arch/x86/vdso/Makefile                        |  18 ++--
 arch/x86/vdso/vdso-fakesections.c             |  32 +++++++
 arch/x86/vdso/vdso2c.c                        |  19 +++-
 arch/x86/vdso/vdso2c.h                        |  23 ++++-
 7 files changed, 268 insertions(+), 126 deletions(-)
 create mode 100644 Documentation/vDSO/vdso_standalone_test_x86.c
 create mode 100644 arch/x86/vdso/vdso-fakesections.c

1.9.3