[all-commits] [llvm/llvm-project] 9ef6fa: [scudo][standalone] Fork support

[Kostya Kortchinsky via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 9ef6faf49670e18eb1ba04105a7c70b450cdaa71
      https://github.com/llvm/llvm-project/commit/9ef6faf49670e18eb1ba04105a7c70b450cdaa71
  Author: Kostya Kortchinsky <kostyak at google.com>
  Date:   2020-01-14 (Tue, 14 Jan 2020)

  Changed paths:
    M compiler-rt/lib/scudo/standalone/CMakeLists.txt
    M compiler-rt/lib/scudo/standalone/bytemap.h
    M compiler-rt/lib/scudo/standalone/combined.h
    M compiler-rt/lib/scudo/standalone/primary32.h
    M compiler-rt/lib/scudo/standalone/primary64.h
    M compiler-rt/lib/scudo/standalone/quarantine.h
    M compiler-rt/lib/scudo/standalone/stats.h
    M compiler-rt/lib/scudo/standalone/tests/CMakeLists.txt
    M compiler-rt/lib/scudo/standalone/tests/tsd_test.cpp
    M compiler-rt/lib/scudo/standalone/tests/wrappers_c_test.cpp
    M compiler-rt/lib/scudo/standalone/tests/wrappers_cpp_test.cpp
    M compiler-rt/lib/scudo/standalone/tsd.h
    M compiler-rt/lib/scudo/standalone/tsd_exclusive.h
    M compiler-rt/lib/scudo/standalone/tsd_shared.h
    M compiler-rt/lib/scudo/standalone/wrappers_c.cpp
    M compiler-rt/lib/scudo/standalone/wrappers_c.inc
    M compiler-rt/lib/scudo/standalone/wrappers_c_bionic.cpp
    M compiler-rt/lib/scudo/standalone/wrappers_cpp.cpp

  Log Message:
  -----------
  [scudo][standalone] Fork support

Summary:
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.

Subscribers: jfb, #sanitizers, llvm-commits

Tags: #sanitizers, #llvm

Differential Revision: https://reviews.llvm.org/D72470