[PATCH] D41723: Introduce the "retpoline" x86 mitigation technique for variant #2 of the speculative execution vulnerabilities disclosed today, specifically identified by CVE-2017-5715, "Branch Target Injection", and is one of the two halves to Spectre..

[Roger via Phabricator via llvm-commits]

royger added a comment.

In https://reviews.llvm.org/D41723#967987, @chandlerc wrote:

> Add support for externally provided thunks. This is an independent feature;
>  when combined with the overall retpoline feature it suppresses the thunk
>  emission and rotates the names to be distinct names that an external build
>  system for the kernel (for example) can provide.
>
> I've added some minimal documentation about the semantic requirements of these
>  thunks to the commit log, although it is fairly obvious. More comprehensive
>  documentation will be part of the large follow-up effort around docs.


Thanks! I'm however not seeing the updated commit message that contains the usage documentation of the new option in the differential revision.

AFAICT from the code, the new option is going to be named "mretpoline_external_thunk", could we have a more generic name that could be used by all options, like:

-mindirect-thunk={retpoline,external}

This should also allow clang to implement new techniques as they become available, without having to add new options for each one of them.


https://reviews.llvm.org/D41723