[compiler-rt] db07e08 - [TSan] Omit vfork interceptor iOS simulator runtime

[Julian Lettner via llvm-commits]

Author: Julian Lettner
Date: 2022-01-21T17:36:12-08:00
New Revision: db07e082abafb1494ba674047645e6113316673c

URL: https://github.com/llvm/llvm-project/commit/db07e082abafb1494ba674047645e6113316673c
DIFF: https://github.com/llvm/llvm-project/commit/db07e082abafb1494ba674047645e6113316673c.diff

LOG: [TSan] Omit vfork interceptor iOS simulator runtime

`_vfork` moved from libsystem_kernel.dylib to libsystem_c.dylib as part
of the below changes.  The iOS simulator does not actually have
libsystem_kernel.dylib of its own, it only has the host Mac's.  The
umbrella-nature of Libsystem makes this movement transparent to
everyone; except the simulator! So when we "back deploy", i.e., use the
current version of TSan with an older simulator runtime then this symbol
is now missing, when we run on the latest OS (but an older simulator
runtime).

Note we use `SANITIZER_IOS` because usage of vfork is forbidden on iOS
and the API is completely unavailable on watchOS and tvOS, even if this
problem is specific to the iOS simulator.

Caused by:
rdar://74818691 (Shim vfork() to fork syscall on iOS)
rdar://76762076 (Shim vfork() to fork syscall on macOS)

Radar-Id: rdar://8634734

Added: 
    

Modified: 
    compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp

Removed: 
    


################################################################################
diff  --git a/compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp b/compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp
index c4f43d8171abb..056bd15e0907a 100644
--- a/compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp
+++ b/compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp
@@ -2204,6 +2204,7 @@ void atfork_child() {
   FdOnFork(thr, pc);
 }
 
+#if !SANITIZER_IOS
 TSAN_INTERCEPTOR(int, vfork, int fake) {
   // Some programs (e.g. openjdk) call close for all file descriptors
   // in the child process. Under tsan it leads to false positives, because
@@ -2220,6 +2221,7 @@ TSAN_INTERCEPTOR(int, vfork, int fake) {
   // Instead we simply turn vfork into fork.
   return WRAP(fork)(fake);
 }
+#endif
 
 #if SANITIZER_LINUX
 TSAN_INTERCEPTOR(int, clone, int (*fn)(void *), void *stack, int flags,