[PATCH] D72470: [scudo][standalone] Fork support

[Kostya Kortchinsky via Phabricator via llvm-commits]

cryptoad created this revision.
Herald added subscribers: llvm-commits, Sanitizers, jfb.
Herald added projects: Sanitizers, LLVM.

fork() wasn't well (or at all) supported in Scudo. This materialized
in deadlocks in children.

In order to properly support fork, we will lock the allocator pre-fork
and unlock it post-fork in parent and child. This is done via a
`pthread_atfork` call installing the necessary handlers.

A couple of things suck here: this function allocates - so this has to
be done post initialization as our init path is not reentrance, and it
doesn't allow for an extra pointer - so we can't pass the allocator we
are currently working with.

In order to work around this, I added a post-init template parameter
that gets executed once the allocator is initialized for the current
thread. Its job for the C wrappers is to install the atfork handlers.

I reorganized a bit the impacted area and added some tests, courtesy
of cferris@ that were deadlocking prior to this fix.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D72470

Files:
  compiler-rt/lib/scudo/standalone/combined.h
  compiler-rt/lib/scudo/standalone/tests/tsd_test.cpp
  compiler-rt/lib/scudo/standalone/tests/wrappers_c_test.cpp
  compiler-rt/lib/scudo/standalone/tests/wrappers_cpp_test.cpp
  compiler-rt/lib/scudo/standalone/tsd_exclusive.h
  compiler-rt/lib/scudo/standalone/tsd_shared.h
  compiler-rt/lib/scudo/standalone/wrappers_c.cpp
  compiler-rt/lib/scudo/standalone/wrappers_c.inc
  compiler-rt/lib/scudo/standalone/wrappers_c_bionic.cpp
  compiler-rt/lib/scudo/standalone/wrappers_cpp.cpp

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