ACK/cmnt: [SRU trusty] LP#1758856 -- retpoline hint support

[Kleber Souza]

On 03/26/18 17:08, Andy Whitcroft wrote:
> 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

This commit has hit upstream with sha1
a14bff131108faf50cc0cf864589fd71ee216c96. We can fix the commit while
applying the patch.

>     - 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

There's a typo on the commit title, which can also be fixed.

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

Changes look good to me. Compiled tested with the follow-up fixes ("[SRU
trusty/xenial/artful/bionic/unstable] LP#1758856/LP#1760876 -- retpoline
hints cleanups") on all supported architectures.

Acked-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>