Re: [Valgrind-developers] Handling Restartable Sequences (RSEQ) in Dynamic Instrumentation Frameworks

[Derek B. <bru...@go...>]

On Mon, Feb 11, 2019 at 12:01 PM 'Kevin Malachowski' via DynamoRIO Devs <
dyn...@go...> wrote:

> Last year a commit was made to the linux
> kernel introducing “Restartable Sequences” (aka rseq), a low-level
> synchronization primitive for doing lockless per-CPU work.

... assuming it affects more than us, we figured we could try and come up
> with a
> solution that works well for everyone.
>

DynamoRIO has implemented a "run twice" solution to support this rseq
kernel feature.  It is a thorny problem to solve and we have documented the
problems and our solutions at
 https://github.com/DynamoRIO/dynamorio/wiki/Restartable-Sequences
<https://github.com/DynamoRIO/dynamorio/wiki/Restartable-Sequences>.  We
had to rely on application conventions (also being pushed by the rseq
library writers) and limit the scope of what is supported in order to
arrive at a workable solution. When Valgrind tackles this problem we would
be interested in hearing about it, including any alternative solutions.

- Derek