[SRU trusty] LP#1758856 -- retpoline hint 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 trusty.

-apw


The following changes since commit 6dfee0a4204e66f34efb55ac4a854859424eb8c6:

  UBUNTU: Ubuntu-3.13.0-144.193 (2018-03-15 17:13:36 +0100)

are available in the Git repository at:

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

for you to fetch changes up to a220af364c4c6f8ed6b66913a0d16aef412a005f:

  UBUNTU: [Config] retpoine -- switch to new format (2018-03-26 11:47:29 +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