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Micah Elizabeth Scott
3036bedf30
This is a change intended for 0.4.7 maintenance as well as main.
The CI builds use Debian Buster which is now end of life, and I was
experiencing inconsistent CI failures with accessing its security update
server. I wanted to update CI to a distro that isn't EOL, and Bullseye
is the current stable release of Debian.
This opened up a small can of worms that this commit also deals with.
In particular there's a docker engine bug that we work around by
removing the docker-specific apt cleanup script if it exists, and
there's a new incompatibility between tracing and sandbox support.
The tracing/sandbox incompatibility itself had two parts:
- The membarrier() syscall is used to deliver inter-processor
synchronization events, and the external "userspace-rcu"
data structure library would make assumptions that if membarrier
is available at initialization it always will be. This caused
segfaults in some cases when running trace + sandbox. Resolved this
by allowing membarrier entirely, in the sandbox.
- userspace-rcu also assumes it can block signals, and fails
hard if this can't be done. We already include a similar carveout
to allow this in the sandbox for fragile-hardening, so I extended
that to cover tracing as well.
Addresses issue #40799
Signed-off-by: Micah Elizabeth Scott <beth@torproject.org>