[bionic] LP#1758856 -- retpoline hinting support

[Andy Whitcroft]

We have been having horrible problems with the retpoline information as
recorded in the ABI changing on every update.  The below pull-request
brings in some new support utilising the upstream retpoline annotations.
As well as bringing in some new annotations where needed.

This should in time bring us to the situation where the retpoline
information for every branch is empty.  Where unannotated entries remain
they are in review and will be coverered off in later updates.  These
are not regressions.

Proposing for bionic.

-apw


The following changes since commit 280c11a2a93bb05d799367f104f2db29a7e5f346:

  UBUNTU: Config: Set TRANSPARENT_HUGEPAGE_ALWAYS=y on ppc64el (2018-03-21 13:40:49 -0300)

are available in the Git repository at:

  git://git.launchpad.net/~apw/ubuntu/+source/linux/+git/review retpoline-hints/bionic

for you to fetch changes up to 7404320080e8eba3e8b4086d732762f24e33c5fa:

  UBUNTU: [Config] retpoine -- switch to new format (2018-03-26 11:48:57 +0100)

----------------------------------------------------------------
  * retpoline hints: primary infrastructure and initial hints (LP: #1758856)
    - [Packaging] retpoline -- add safe usage hint support
    - [Packaging] retpoline-check -- only report additions
    - [Packaging] retpoline -- widen indirect call/jmp detection
    - [Packaging] retpoline -- elide %rip relative indirections
    - [Packaging] retpoline -- clear hint information from packages
    - SAUCE: apm -- annotate indirect calls within
      firmware_restrict_branch_speculation_{start,end}
    - SAUCE: EFI -- annotate indirect calls within
      firmware_restrict_branch_speculation_{start,end}
    - SAUCE: early/late -- annotate indirect calls in early/late initialisation
      code
    - SAUCE: vga_set_mode -- avoid jump tables
    - [Config] retpoine -- switch to new format