[sanitizer] Add 'strip_env' flag to enable/disable removing sanitizer dylib from DYLD_INSERT_LIBRARIES

kubamracek · kubamracek · commit ceea5466eb02 · 2017-11-29T21:42:48.000Z
On macOS, we usually don't require launching the target with DYLD_INSERT_LIBRARIES anymore. However, it is still necessary when running a target that is not instrumented (and e.g. dlopen's an instrument library later). In any case, ASan and TSan currently remove themselves from the DYLD_INSERT_LIBRARIES environment variable to avoid passing it onto children. This works well e.g. when instrumenting a shell. A problem arises when the target is a non-instrumented shim (e.g. "xcrun") that either re-execs or launches a child that is supposed to get DYLD_INSERT_LIBRARIES propagated. To support this mode, this patch introduces 'strip_env' flag that can be used to keep DYLD_INSERT_LIBRARIES untouched. Differential Revision: https://reviews.llvm.org/D39991 llvm-svn: 319365
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_flags.inc b/compiler-rt/lib/sanitizer_common/sanitizer_flags.inc
@@ -62,6 +62,9 @@ COMMON_FLAG(
 COMMON_FLAG(
     int, verbosity, 0,
     "Verbosity level (0 - silent, 1 - a bit of output, 2+ - more output).")
+COMMON_FLAG(bool, strip_env, 1,
+            "Whether to remove the sanitizer from DYLD_INSERT_LIBRARIES to "
+            "avoid passing it to children. Default is true.")
 COMMON_FLAG(bool, detect_leaks, !SANITIZER_MAC, "Enable memory leak detection.")
 COMMON_FLAG(
     bool, leak_check_at_exit, true,
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_mac.cc b/compiler-rt/lib/sanitizer_common/sanitizer_mac.cc
@@ -741,6 +741,9 @@ void MaybeReexec() {
   if (!lib_is_in_env)
     return;
 
+  if (!common_flags()->strip_env)
+    return;
+
   // DYLD_INSERT_LIBRARIES is set and contains the runtime library. Let's remove
   // the dylib from the environment variable, because interceptors are installed
   // and we don't want our children to inherit the variable.
diff --git a/compiler-rt/test/asan/TestCases/Darwin/dyld_insert_libraries_remove.cc b/compiler-rt/test/asan/TestCases/Darwin/dyld_insert_libraries_remove.cc
@@ -20,6 +20,11 @@
 // RUN:   DYLD_INSERT_LIBRARIES=libclang_rt.asan_osx_dynamic.dylib:dummy-so.dylib \
 // RUN:   %run ./a.out 2>&1 ) | FileCheck %s || exit 1
 
+// RUN: ( cd %t && \
+// RUN:   %env_asan_opts=strip_env=0 \
+// RUN:   DYLD_INSERT_LIBRARIES=libclang_rt.asan_osx_dynamic.dylib:dummy-so.dylib \
+// RUN:   %run ./a.out 2>&1 ) | FileCheck %s --check-prefix=CHECK-KEEP || exit 1
+
 // RUN: ( cd %t && \
 // RUN:   DYLD_INSERT_LIBRARIES=%t/libclang_rt.asan_osx_dynamic.dylib:dummy-so.dylib \
 // RUN:   %run ./a.out 2>&1 ) | FileCheck %s || exit 1
@@ -32,6 +37,7 @@ int main() {
   const char kEnvName[] = "DYLD_INSERT_LIBRARIES";
   printf("%s=%s\n", kEnvName, getenv(kEnvName));
   // CHECK: {{DYLD_INSERT_LIBRARIES=dummy-so.dylib}}
+  // CHECK-KEEP: {{DYLD_INSERT_LIBRARIES=libclang_rt.asan_osx_dynamic.dylib:dummy-so.dylib}}
   return 0;
 }
 #else  // SHARED_LIB
