[SRU xenial] 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 SRU to xenial.

-apw


The following changes since commit fc74a5c4a98418105b4b246b935e3be90d6a635c:

  UBUNTU: Ubuntu-4.4.0-117.141 (2018-03-13 11:57:37 +0100)

are available in the Git repository at:

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

for you to fetch changes up to 91dbb39acb847daedd4de4f34308e674ce8e3f4b:

  UBUNTU: [Config] retpoine -- switch to new format (2018-03-26 11:48:04 +0100)

----------------------------------------------------------------
  * retpoline hints: primary infrastructure and initial hints (LP: #1758856)
    - [Packaging] retpoline-extract: flag *0xNNN(%reg) branches
    - x86/speculation, objtool: Annotate indirect calls/jumps for objtool
    - x86/speculation, objtool: Annotate indirect calls/jumps for objtool on 32bit
    - x86/paravirt, objtool: Annotate indirect calls
    - x86/asm: Stop depending on ptrace.h in alternative.h
    - [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: modpost: add discard to non-allocatable whitelist
    - KVM: x86: Make indirect calls in emulator speculation safe
    - KVM: VMX: Make indirect call speculation safe
    - x86/boot, objtool: Annotate indirect jump in secondary_startup_64()
    - SAUCE: early/late -- annotate indirect calls in early/late initialisation
      code
    - SAUCE: vga_set_mode -- avoid jump tables
    - [Config] retpoine -- switch to new format

  * retpoline: ignore %cs:0xNNN constant indirections (LP: #1752655)
    - [Packaging] retpoline -- elide %cs:0xNNNN constants on i386