Index: compiler-rt/lib/asan/asan_linux.cc
===================================================================
--- compiler-rt/lib/asan/asan_linux.cc
+++ compiler-rt/lib/asan/asan_linux.cc
@@ -210,6 +210,8 @@
     }
   } else {
     if (__asan_rt_version == ASAN_RT_VERSION_UNDEFINED) {
+      if (!MemoryMappingLayout::IsAvailable(/*cache_enabled*/true))
+        return;
       // Ensure that dynamic runtime is not present. We should detect it
       // as early as possible, otherwise ASan interceptors could bind to
       // the functions in dynamic ASan runtime instead of the functions in
Index: compiler-rt/lib/asan/asan_thread.cc
===================================================================
--- compiler-rt/lib/asan/asan_thread.cc
+++ compiler-rt/lib/asan/asan_thread.cc
@@ -18,6 +18,7 @@
 #include "asan_thread.h"
 #include "asan_mapping.h"
 #include "sanitizer_common/sanitizer_common.h"
+#include "sanitizer_common/sanitizer_file.h"
 #include "sanitizer_common/sanitizer_placement_new.h"
 #include "sanitizer_common/sanitizer_stackdepot.h"
 #include "sanitizer_common/sanitizer_tls_get_addr.h"
@@ -223,9 +224,11 @@
   atomic_store(&stack_switching_, false, memory_order_release);
   CHECK_EQ(this->stack_size(), 0U);
   SetThreadStackAndTls(options);
-  CHECK_GT(this->stack_size(), 0U);
-  CHECK(AddrIsInMem(stack_bottom_));
-  CHECK(AddrIsInMem(stack_top_ - 1));
+  if (stack_top_ != stack_bottom_) {
+    CHECK_GT(this->stack_size(), 0U);
+    CHECK(AddrIsInMem(stack_bottom_));
+    CHECK(AddrIsInMem(stack_top_ - 1));
+  }
   ClearShadowForThreadStackAndTLS();
   fake_stack_ = nullptr;
   if (__asan_option_detect_stack_use_after_return)
@@ -287,22 +290,30 @@
 // OS-specific implementations that need more information passed through.
 void AsanThread::SetThreadStackAndTls(const InitOptions *options) {
   DCHECK_EQ(options, nullptr);
-  uptr tls_size = 0;
-  uptr stack_size = 0;
-  GetThreadStackAndTls(tid() == 0, &stack_bottom_, &stack_size, &tls_begin_,
-                       &tls_size);
-  stack_top_ = stack_bottom_ + stack_size;
-  tls_end_ = tls_begin_ + tls_size;
-  dtls_ = DTLS_Get();
-
-  int local;
-  CHECK(AddrIsInStack((uptr)&local));
+  // If this process is "init" (pid 1), /proc may not be mounted yet.
+  if (!start_routine_ &&
+      !MemoryMappingLayout::IsAvailable(/*cache_enabled*/ true)) {
+    stack_top_ = stack_bottom_ = 0;
+    tls_begin_ = tls_end_ = 0;
+  } else {
+    uptr tls_size = 0;
+    uptr stack_size = 0;
+    GetThreadStackAndTls(tid() == 0, &stack_bottom_, &stack_size, &tls_begin_,
+                         &tls_size);
+    stack_top_ = stack_bottom_ + stack_size;
+    tls_end_ = tls_begin_ + tls_size;
+    dtls_ = DTLS_Get();
+
+    int local;
+    CHECK(AddrIsInStack((uptr)&local));
+  }
 }
 
 #endif  // !SANITIZER_FUCHSIA && !SANITIZER_RTEMS
 
 void AsanThread::ClearShadowForThreadStackAndTLS() {
-  PoisonShadow(stack_bottom_, stack_top_ - stack_bottom_, 0);
+  if (stack_top_ != stack_bottom_)
+    PoisonShadow(stack_bottom_, stack_top_ - stack_bottom_, 0);
   if (tls_begin_ != tls_end_) {
     uptr tls_begin_aligned = RoundDownTo(tls_begin_, SHADOW_GRANULARITY);
     uptr tls_end_aligned = RoundUpTo(tls_end_, SHADOW_GRANULARITY);
@@ -314,6 +325,9 @@
 
 bool AsanThread::GetStackFrameAccessByAddr(uptr addr,
                                            StackFrameAccess *access) {
+  if (stack_top_ == stack_bottom_)
+    return false;
+
   uptr bottom = 0;
   if (AddrIsInStack(addr)) {
     bottom = stack_bottom();
Index: compiler-rt/lib/hwasan/hwasan_thread.cc
===================================================================
--- compiler-rt/lib/hwasan/hwasan_thread.cc
+++ compiler-rt/lib/hwasan/hwasan_thread.cc
@@ -44,7 +44,8 @@
   ScopedTaggingDisabler disabler;
 
   // If this process is "init" (pid 1), /proc may not be mounted yet.
-  if (IsMainThread() && !FileExists("/proc/self/maps")) {
+  if (IsMainThread() &&
+      !MemoryMappingLayout::IsAvailable(/*cache_enabled*/ true)) {
     stack_top_ = stack_bottom_ = 0;
     tls_begin_ = tls_end_ = 0;
   } else {
Index: compiler-rt/lib/sanitizer_common/sanitizer_flags.inc
===================================================================
--- compiler-rt/lib/sanitizer_common/sanitizer_flags.inc
+++ compiler-rt/lib/sanitizer_common/sanitizer_flags.inc
@@ -243,3 +243,6 @@
 COMMON_FLAG(bool, detect_write_exec, false,
           "If true, triggers warning when writable-executable pages requests "
           "are being made")
+COMMON_FLAG(bool, test_only_emulate_no_procfs, false,
+            "TEST ONLY fail to open any files under /proc to emulate sanitized "
+            "\"init\"")
Index: compiler-rt/lib/sanitizer_common/sanitizer_linux.h
===================================================================
--- compiler-rt/lib/sanitizer_common/sanitizer_linux.h
+++ compiler-rt/lib/sanitizer_common/sanitizer_linux.h
@@ -44,6 +44,7 @@
 };
 
 void ReadProcMaps(ProcSelfMapsBuff *proc_maps);
+bool IsProcMapsAvailable();
 
 // Syscall wrappers.
 uptr internal_getdents(fd_t fd, struct linux_dirent *dirp, unsigned int count);
Index: compiler-rt/lib/sanitizer_common/sanitizer_linux.cc
===================================================================
--- compiler-rt/lib/sanitizer_common/sanitizer_linux.cc
+++ compiler-rt/lib/sanitizer_common/sanitizer_linux.cc
@@ -453,6 +453,8 @@
 
 // ----------------- sanitizer_common.h
 bool FileExists(const char *filename) {
+  if (ShouldMockFailureToOpen(filename))
+    return false;
   struct stat st;
 #if SANITIZER_USES_CANONICAL_LINUX_SYSCALLS
   if (internal_syscall(SYSCALL(newfstatat), AT_FDCWD, filename, &st, 0))
@@ -1003,6 +1005,8 @@
 // Take care of unusable kernel area in top gigabyte.
 static uptr GetKernelAreaSize() {
 #if SANITIZER_LINUX && !SANITIZER_X32
+  if (!MemoryMappingLayout::IsAvailable(/*cache_enabled*/ true))
+    return 0;
   const uptr gbyte = 1UL << 30;
 
   // Firstly check if there are writable segments
Index: compiler-rt/lib/sanitizer_common/sanitizer_mac.cc
===================================================================
--- compiler-rt/lib/sanitizer_common/sanitizer_mac.cc
+++ compiler-rt/lib/sanitizer_common/sanitizer_mac.cc
@@ -282,6 +282,8 @@
 
 // ----------------- sanitizer_common.h
 bool FileExists(const char *filename) {
+  if (ShouldMockFailureToOpen(filename))
+    return false;
   struct stat st;
   if (stat(filename, &st))
     return false;
Index: compiler-rt/lib/sanitizer_common/sanitizer_posix.h
===================================================================
--- compiler-rt/lib/sanitizer_common/sanitizer_posix.h
+++ compiler-rt/lib/sanitizer_common/sanitizer_posix.h
@@ -103,6 +103,8 @@
 // Move the fd out of {0, 1, 2} range.
 fd_t ReserveStandardFds(fd_t fd);
 
+bool ShouldMockFailureToOpen(const char *path);
+
 }  // namespace __sanitizer
 
 #endif  // SANITIZER_POSIX_H
Index: compiler-rt/lib/sanitizer_common/sanitizer_posix.cc
===================================================================
--- compiler-rt/lib/sanitizer_common/sanitizer_posix.cc
+++ compiler-rt/lib/sanitizer_common/sanitizer_posix.cc
@@ -18,6 +18,7 @@
 
 #include "sanitizer_common.h"
 #include "sanitizer_file.h"
+#include "sanitizer_flags.h"
 #include "sanitizer_libc.h"
 #include "sanitizer_posix.h"
 #include "sanitizer_procmaps.h"
@@ -157,6 +158,8 @@
 #endif
 
 fd_t OpenFile(const char *filename, FileAccessMode mode, error_t *errno_p) {
+  if (ShouldMockFailureToOpen(filename))
+    return kInvalidFd;
   int flags;
   switch (mode) {
     case RdOnly: flags = O_RDONLY; break;
@@ -229,6 +232,8 @@
 // several worker threads on Mac, which aren't expected to map big chunks of
 // memory).
 bool MemoryRangeIsAvailable(uptr range_start, uptr range_end) {
+  if (!MemoryMappingLayout::IsAvailable(/*cache_enabled*/ true))
+    return true; // hope for the best
   MemoryMappingLayout proc_maps(/*cache_enabled*/true);
   MemoryMappedSegment segment;
   while (proc_maps.Next(&segment)) {
@@ -333,6 +338,11 @@
   return fd;
 }
 
+bool ShouldMockFailureToOpen(const char *path) {
+  return common_flags()->test_only_emulate_no_procfs &&
+         internal_strncmp(path, "/proc/", 6) == 0;
+}
+
 } // namespace __sanitizer
 
 #endif // SANITIZER_POSIX
Index: compiler-rt/lib/sanitizer_common/sanitizer_procmaps.h
===================================================================
--- compiler-rt/lib/sanitizer_common/sanitizer_procmaps.h
+++ compiler-rt/lib/sanitizer_common/sanitizer_procmaps.h
@@ -75,6 +75,7 @@
   // to obtain the memory mappings. It should fall back to pre-cached data
   // instead of aborting.
   static void CacheMemoryMappings();
+  static bool IsAvailable(bool cache_enabled);
 
   // Adds all mapped objects into a vector.
   void DumpListOfModules(InternalMmapVectorNoCtor<LoadedModule> *modules);
Index: compiler-rt/lib/sanitizer_common/sanitizer_procmaps_bsd.cc
===================================================================
--- compiler-rt/lib/sanitizer_common/sanitizer_procmaps_bsd.cc
+++ compiler-rt/lib/sanitizer_common/sanitizer_procmaps_bsd.cc
@@ -45,6 +45,10 @@
 
 namespace __sanitizer {
 
+bool IsProcMapsAvailable() {
+  return true;
+}
+
 void ReadProcMaps(ProcSelfMapsBuff *proc_maps) {
   const int Mib[] = {
 #if SANITIZER_FREEBSD
Index: compiler-rt/lib/sanitizer_common/sanitizer_procmaps_common.cc
===================================================================
--- compiler-rt/lib/sanitizer_common/sanitizer_procmaps_common.cc
+++ compiler-rt/lib/sanitizer_common/sanitizer_procmaps_common.cc
@@ -144,6 +144,12 @@
   }
 }
 
+bool MemoryMappingLayout::IsAvailable(bool cache_enabled) {
+  if (cache_enabled && cached_proc_self_maps.data)
+    return true;
+  return IsProcMapsAvailable();
+}
+
 void GetMemoryProfile(fill_profile_f cb, uptr *stats, uptr stats_size) {
   char *smaps = nullptr;
   uptr smaps_cap = 0;
Index: compiler-rt/lib/sanitizer_common/sanitizer_procmaps_linux.cc
===================================================================
--- compiler-rt/lib/sanitizer_common/sanitizer_procmaps_linux.cc
+++ compiler-rt/lib/sanitizer_common/sanitizer_procmaps_linux.cc
@@ -13,10 +13,15 @@
 #include "sanitizer_platform.h"
 #if SANITIZER_LINUX
 #include "sanitizer_common.h"
+#include "sanitizer_file.h"
 #include "sanitizer_procmaps.h"
 
 namespace __sanitizer {
 
+bool IsProcMapsAvailable() {
+  return FileExists("/proc/self/maps");
+}
+
 void ReadProcMaps(ProcSelfMapsBuff *proc_maps) {
   if (!ReadFileToBuffer("/proc/self/maps", &proc_maps->data,
                         &proc_maps->mmaped_size, &proc_maps->len)) {
Index: compiler-rt/lib/sanitizer_common/sanitizer_procmaps_solaris.cc
===================================================================
--- compiler-rt/lib/sanitizer_common/sanitizer_procmaps_solaris.cc
+++ compiler-rt/lib/sanitizer_common/sanitizer_procmaps_solaris.cc
@@ -20,6 +20,10 @@
 
 namespace __sanitizer {
 
+bool IsProcMapsAvailable() {
+  return FileExists("/proc/self/xmap");
+}
+
 void ReadProcMaps(ProcSelfMapsBuff *proc_maps) {
   ReadFileToBuffer("/proc/self/xmap", &proc_maps->data, &proc_maps->mmaped_size,
                    &proc_maps->len);
Index: compiler-rt/test/asan/TestCases/Posix/no-fd.cc
===================================================================
--- compiler-rt/test/asan/TestCases/Posix/no-fd.cc
+++ compiler-rt/test/asan/TestCases/Posix/no-fd.cc
@@ -9,6 +9,10 @@
 #include <stdlib.h>
 #include <unistd.h>
 
+extern "C" const char *__asan_default_options() {
+  return "test_only_emulate_no_procfs=1";
+}
+
 void parent(int argc, char **argv) {
   fprintf(stderr, "hello\n");
   // CHECK: hello