[llvm-dev] RFC: Speculative Load Hardening (a Spectre variant #1 mitigation)

[Friedman, Eli via llvm-dev]

On 7/11/2018 4:02 AM, Chandler Carruth via llvm-dev wrote:
>
>     I believe this approach has the advantage that:
>     a) it makes it possible to only insert a mitigation in specific
>     locations if
>        the programmer is capable of inserting intrinsics manually.
>
>
> This is definitely an area of great interest long-term.

Annotating specific loads that need to be protected seems like a trap to 
me.  See https://reviews.llvm.org/D41761#989799 .  (And Bounds Check 
Bypass Store variants open up other possibilities, like overwriting a 
spill slot.)

Maybe we can come up with some workable approach to "whitelist" certain 
pointers: a pointer could be marked "speculatively-dereferenceable(N)" 
if it points to N bytes of non-secret data.  (We could apply this as 
load metadata, like !dereferenceable, or it could be explicitly applied 
using an intrinsic.)

-Eli

-- 
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project

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