[sanitizer_common] Fuchsia OS support code

[vitalybuka]

I looked sanitizer_fuchsia.cc very briefly.
The rest LGTM

lib/sanitizer_common/sanitizer_printf.cc

260

I guess you would like to enabled as many as possible compiler-rt tests in future
So maybe better to avoid diverging if this is not critical?

[mcgrathr]

lib/sanitizer_common/sanitizer_printf.cc

260

I will be getting the tests going at some point.
The logging story is very different on Fuchsia, so there will be a bunch more work in getting the tests right.
We absolutely do not want the sanitizer logging to do this kind of tagging for Fuchsia.

[mcgrathr]

This is rebased and ready to land after D36029 lands.
Please land it for me!

Thanks,
Roland

CMakeLists.txt

if (SANITIZER_USE_COMPILER_RT)
   find_compiler_rt_library(builtins COMPILER_RT_BUILTINS_LIBRARY)
   list(APPEND SANITIZER_COMMON_LINK_LIBS ${COMPILER_RT_BUILTINS_LIBRARY})
 else()
   append_list_if(COMPILER_RT_HAS_GCC_S_LIB gcc_s SANITIZER_COMMON_LINK_LIBS)
 endif()
 
 append_list_if(COMPILER_RT_HAS_LIBC c SANITIZER_COMMON_LINK_LIBS)
 
+if("${CMAKE_SYSTEM_NAME}" STREQUAL "Fuchsia")
+  list(APPEND SANITIZER_COMMON_LINK_FLAGS -Wl,-z,defs,-z,now,-z,relro)
+  list(APPEND SANITIZER_COMMON_LINK_LIBS magenta)
+endif()
+
 # Warnings to turn off for all libraries, not just sanitizers.
 append_string_if(COMPILER_RT_HAS_WUNUSED_PARAMETER_FLAG -Wno-unused-parameter CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
 
 if (CMAKE_LINKER MATCHES "link.exe$")
   # Silence MSVC linker warnings caused by empty object files. The
   # sanitizer libraries intentionally use ifdefs that result in empty
   # files, rather than skipping these files in the build system.
   # Ideally, we would pass this flag only for the libraries that need

cmake/config-ix.cmake

 endif()
 
 set(ALL_SANITIZERS asan;dfsan;msan;tsan;safestack;cfi;esan;scudo)
 set(COMPILER_RT_SANITIZERS_TO_BUILD ${ALL_SANITIZERS} CACHE STRING
     "sanitizers to build if supported on the target (all;${ALL_SANITIZERS})")
 list_replace(COMPILER_RT_SANITIZERS_TO_BUILD all "${ALL_SANITIZERS}")
 
 if (SANITIZER_COMMON_SUPPORTED_ARCH AND NOT LLVM_USE_SANITIZER AND
-    (OS_NAME MATCHES "Android|Darwin|Linux|FreeBSD" OR
+    (OS_NAME MATCHES "Android|Darwin|Linux|FreeBSD|Fuchsia" OR
     (OS_NAME MATCHES "Windows" AND (NOT MINGW AND NOT CYGWIN))))
   set(COMPILER_RT_HAS_SANITIZER_COMMON TRUE)
 else()
   set(COMPILER_RT_HAS_SANITIZER_COMMON FALSE)
 endif()
 
 if (COMPILER_RT_HAS_SANITIZER_COMMON)
   set(COMPILER_RT_HAS_INTERCEPTION TRUE)

lib/sanitizer_common/CMakeLists.txt

 # Build system for the common Sanitizer runtime support library components.
 # These components are shared between AddressSanitizer and ThreadSanitizer.
 
 set(SANITIZER_SOURCES_NOTERMINATION
   sanitizer_allocator.cc
   sanitizer_common.cc
   sanitizer_deadlock_detector1.cc
   sanitizer_deadlock_detector2.cc
   sanitizer_errno.cc
   sanitizer_file.cc
   sanitizer_flags.cc
   sanitizer_flag_parser.cc
+  sanitizer_fuchsia.cc
   sanitizer_libc.cc
   sanitizer_libignore.cc
   sanitizer_linux.cc
   sanitizer_linux_s390.cc
   sanitizer_mac.cc
   sanitizer_persistent_allocator.cc
   sanitizer_platform_limits_linux.cc
   sanitizer_platform_limits_posix.cc
set(SANITIZER_HEADERS
   sanitizer_deadlock_detector.h
   sanitizer_deadlock_detector_interface.h
   sanitizer_errno.h
   sanitizer_errno_codes.h
   sanitizer_file.h
   sanitizer_flag_parser.h
   sanitizer_flags.h
   sanitizer_flags.inc
+  sanitizer_fuchsia.h
   sanitizer_interface_internal.h
   sanitizer_internal_defs.h
   sanitizer_lfstack.h
   sanitizer_libc.h
   sanitizer_libignore.h
   sanitizer_linux.h
   sanitizer_list.h
   sanitizer_mac.h

lib/sanitizer_common/sanitizer_fuchsia.h

+//===-- sanitizer_fuchsia.h ------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===---------------------------------------------------------------------===//
+//
+// Fuchsia-specific sanitizer support.
+//
+//===---------------------------------------------------------------------===//
+#ifndef SANITIZER_FUCHSIA_H
+#define SANITIZER_FUCHSIA_H
+
+#include "sanitizer_platform.h"
+#if SANITIZER_FUCHSIA
+
+#include "sanitizer_common.h"
+
+#include <magenta/sanitizer.h>
+
+namespace __sanitizer {
+
+extern uptr MainThreadStackBase, MainThreadStackSize;
+extern sanitizer_shadow_bounds_t ShadowBounds;
+
+}  // namespace __sanitizer
+
+#endif  // SANITIZER_FUCHSIA
+#endif  // SANITIZER_FUCHSIA_H

lib/sanitizer_common/sanitizer_fuchsia.cc

+//===-- sanitizer_fuchsia.cc ---------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===---------------------------------------------------------------------===//
+//
+// This file is shared between AddressSanitizer and other sanitizer
+// run-time libraries and implements Fuchsia-specific functions from
+// sanitizer_common.h.
+//===---------------------------------------------------------------------===//
+
+#include "sanitizer_fuchsia.h"
+#if SANITIZER_FUCHSIA
+
+#include "sanitizer_common.h"
+#include "sanitizer_libc.h"
+#include "sanitizer_mutex.h"
+#include "sanitizer_procmaps.h"
+#include "sanitizer_stacktrace.h"
+
+#include <limits.h>
+#include <magenta/errors.h>
+#include <magenta/process.h>
+#include <magenta/syscalls.h>
+#include <pthread.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <unwind.h>
+
+namespace __sanitizer {
+
+void NORETURN internal__exit(int exitcode) {
+  _mx_process_exit(exitcode);
+}
+
+uptr internal_sched_yield() {
+  mx_status_t status = _mx_nanosleep(0);
+  CHECK_EQ(status, MX_OK);
+  return 0;  // Why doesn't this return void?
+}
+
+static void internal_nanosleep(mx_time_t ns) {
+  mx_status_t status = _mx_nanosleep(_mx_deadline_after(ns));
+  CHECK_EQ(status, MX_OK);
+}
+
+unsigned int internal_sleep(unsigned int seconds) {
+  internal_nanosleep(MX_SEC(seconds));
+  return 0;
+}
+
+u64 NanoTime() {
+  return _mx_time_get(MX_CLOCK_UTC);
+}
+
+uptr internal_getpid() {
+  mx_info_handle_basic_t info;
+  mx_status_t status = _mx_object_get_info(_mx_process_self(),
+                                           MX_INFO_HANDLE_BASIC,
+                                           &info, sizeof(info), NULL, NULL);
+  CHECK_EQ(status, MX_OK);
+  uptr pid = static_cast<uptr>(info.koid);
+  CHECK_EQ(pid, info.koid);
+  return pid;
+}
+
+uptr GetThreadSelf() {
+  return reinterpret_cast<uptr>(thrd_current());
+}
+
+uptr GetTid() {
+  return GetThreadSelf();
+}
+
+void Abort() {
+  abort();
+}
+
+int Atexit(void (*function)(void)) {
+  return atexit(function);
+}
+
+void SleepForSeconds(int seconds) {
+  internal_sleep(seconds);
+}
+
+void SleepForMillis(int millis) {
+  internal_nanosleep(MX_MSEC(millis));
+}
+
+void GetThreadStackTopAndBottom(bool, uptr *stack_top, uptr *stack_bottom) {
+  pthread_attr_t attr;
+  CHECK_EQ(pthread_getattr_np(pthread_self(), &attr), 0);
+  void *base;
+  size_t size;
+  CHECK_EQ(pthread_attr_getstack(&attr, &base, &size), 0);
+  CHECK_EQ(pthread_attr_destroy(&attr), 0);
+
+  *stack_bottom = reinterpret_cast<uptr>(base);
+  *stack_top = *stack_bottom + size;
+}
+
+void MaybeReexec() {}
+void PrepareForSandboxing(__sanitizer_sandbox_arguments *args) {}
+void DisableCoreDumperIfNecessary() {}
+void InstallDeadlySignalHandlers(SignalHandlerType handler) {}
+void SetAlternateSignalStack() {}
+void UnsetAlternateSignalStack() {}
+void InitTlsSize() {}
+
+void PrintModuleMap() {}
+
+struct UnwindTraceArg {
+  BufferedStackTrace *stack;
+  u32 max_depth;
+};
+
+_Unwind_Reason_Code Unwind_Trace(struct _Unwind_Context *ctx, void *param) {
+  UnwindTraceArg *arg = static_cast<UnwindTraceArg*>(param);
+  CHECK_LT(arg->stack->size, arg->max_depth);
+  uptr pc = _Unwind_GetIP(ctx);
+  if (pc < PAGE_SIZE)
+    return _URC_NORMAL_STOP;
+  arg->stack->trace_buffer[arg->stack->size++] = pc;
+  return (arg->stack->size == arg->max_depth ?
+          _URC_NORMAL_STOP : _URC_NO_REASON);
+}
+
+void BufferedStackTrace::SlowUnwindStack(uptr pc, u32 max_depth) {
+  CHECK_GE(max_depth, 2);
+  size = 0;
+  UnwindTraceArg arg = {this, Min(max_depth + 1, kStackTraceMax)};
+  _Unwind_Backtrace(Unwind_Trace, &arg);
+  CHECK_GT(size, 0);
+  // We need to pop a few frames so that pc is on top.
+  uptr to_pop = LocatePcInTrace(pc);
+  // trace_buffer[0] belongs to the current function so we always pop it,
+  // unless there is only 1 frame in the stack trace (1 frame is always better
+  // than 0!).
+  PopStackFrames(Min(to_pop, static_cast<uptr>(1)));
+  trace_buffer[0] = pc;
+}
+
+void BufferedStackTrace::SlowUnwindStackWithContext(uptr pc, void *context,
+                                                    u32 max_depth) {
+  CHECK_NE(context, nullptr);
+  UNREACHABLE("signal context doesn't exist");
+}
+
+enum MutexState : int {
+  MtxUnlocked = 0,
+  MtxLocked = 1,
+  MtxSleeping = 2
+};
+
+BlockingMutex::BlockingMutex() {
+  // NOTE!  It's important that this use internal_memset, because plain
+  // memset might be intercepted (e.g., actually be __asan_memset).
+  // Defining this so the compiler initializes each field, e.g.:
+  //   BlockingMutex::BlockingMutex() : BlockingMutex(LINKER_INITIALIZED) {}
+  // might result in the compiler generating a call to memset, which would
+  // have the same problem.
+  internal_memset(this, 0, sizeof(*this));
+}
+
+void BlockingMutex::Lock() {
+  CHECK_EQ(owner_, 0);
+  atomic_uint32_t *m = reinterpret_cast<atomic_uint32_t *>(&opaque_storage_);
+  if (atomic_exchange(m, MtxLocked, memory_order_acquire) == MtxUnlocked)
+    return;
+  while (atomic_exchange(m, MtxSleeping, memory_order_acquire) != MtxUnlocked) {
+    mx_status_t status = _mx_futex_wait(reinterpret_cast<mx_futex_t *>(m),
+                                        MtxSleeping, MX_TIME_INFINITE);
+    if (status != MX_ERR_BAD_STATE) // Normal race.
+      CHECK_EQ(status, MX_OK);
+  }
+}
+
+void BlockingMutex::Unlock() {
+  atomic_uint32_t *m = reinterpret_cast<atomic_uint32_t *>(&opaque_storage_);
+  u32 v = atomic_exchange(m, MtxUnlocked, memory_order_release);
+  CHECK_NE(v, MtxUnlocked);
+  if (v == MtxSleeping) {
+    mx_status_t status = _mx_futex_wake(reinterpret_cast<mx_futex_t *>(m), 1);
+    CHECK_EQ(status, MX_OK);
+  }
+}
+
+void BlockingMutex::CheckLocked() {
+  atomic_uint32_t *m = reinterpret_cast<atomic_uint32_t *>(&opaque_storage_);
+  CHECK_NE(MtxUnlocked, atomic_load(m, memory_order_relaxed));
+}
+
+uptr GetPageSize() {
+  return PAGE_SIZE;
+}
+
+uptr GetMmapGranularity() {
+  return PAGE_SIZE;
+}
+
+sanitizer_shadow_bounds_t ShadowBounds;
+
+uptr GetMaxVirtualAddress() {
+  ShadowBounds = __sanitizer_shadow_bounds();
+  return ShadowBounds.memory_limit - 1;
+}
+
+static void *DoAnonymousMmapOrDie(uptr size, const char *mem_type,
+                                  bool raw_report, bool die_for_nomem) {
+  size = RoundUpTo(size, PAGE_SIZE);
+
+  mx_handle_t vmo;
+  mx_status_t status = _mx_vmo_create(size, 0, &vmo);
+  if (status != MX_OK) {
+    if (status != MX_ERR_NO_MEMORY || die_for_nomem)
+      ReportMmapFailureAndDie(size, mem_type, "mx_vmo_create",
+                              status, raw_report);
+    return nullptr;
+  }
+  _mx_object_set_property(vmo, MX_PROP_NAME,
+                          mem_type, internal_strlen(mem_type));
+
+  // TODO(mcgrathr): Maybe allocate a VMAR for all sanitizer heap and use that?
+  uintptr_t addr;
+  status = _mx_vmar_map(_mx_vmar_root_self(), 0, vmo, 0, size,
+                        MX_VM_FLAG_PERM_READ | MX_VM_FLAG_PERM_WRITE, &addr);
+  _mx_handle_close(vmo);
+
+  if (status != MX_OK) {
+    if (status != MX_ERR_NO_MEMORY || die_for_nomem)
+      ReportMmapFailureAndDie(size, mem_type, "mx_vmar_map",
+                              status, raw_report);
+    return nullptr;
+  }
+
+  IncreaseTotalMmap(size);
+
+  return reinterpret_cast<void *>(addr);
+}
+
+void *MmapOrDie(uptr size, const char *mem_type, bool raw_report) {
+  return DoAnonymousMmapOrDie(size, mem_type, raw_report, true);
+}
+
+void *MmapNoReserveOrDie(uptr size, const char *mem_type) {
+  return MmapOrDie(size, mem_type);
+}
+
+void *MmapOrDieOnFatalError(uptr size, const char *mem_type) {
+  return DoAnonymousMmapOrDie(size, mem_type, false, false);
+}
+
+// MmapNoAccess and MmapFixedOrDie are used only by sanitizer_allocator.
+// Instead of doing exactly what they say, we make MmapNoAccess actually
+// just allocate a VMAR to reserve the address space.  Then MmapFixedOrDie
+// uses that VMAR instead of the root.
+
+mx_handle_t allocator_vmar = MX_HANDLE_INVALID;
+uintptr_t allocator_vmar_base;
+size_t allocator_vmar_size;
+
+void *MmapNoAccess(uptr size) {
+  size = RoundUpTo(size, PAGE_SIZE);
+  CHECK_EQ(allocator_vmar, MX_HANDLE_INVALID);
+  uintptr_t base;
+  mx_status_t status = _mx_vmar_allocate(_mx_vmar_root_self(), 0, size,
+                                         MX_VM_FLAG_CAN_MAP_READ |
+                                         MX_VM_FLAG_CAN_MAP_WRITE |
+                                         MX_VM_FLAG_CAN_MAP_SPECIFIC,
+                                         &allocator_vmar, &base);
+  if (status != MX_OK)
+    ReportMmapFailureAndDie(size, "sanitizer allocator address space",
+                            "mx_vmar_allocate", status);
+
+  allocator_vmar_base = base;
+  allocator_vmar_size = size;
+  return reinterpret_cast<void *>(base);
+}
+
+constexpr const char kAllocatorVmoName[] = "sanitizer_allocator";
+
+static void *DoMmapFixedOrDie(uptr fixed_addr, uptr size, bool die_for_nomem) {
+  size = RoundUpTo(size, PAGE_SIZE);
+
+  mx_handle_t vmo;
+  mx_status_t status = _mx_vmo_create(size, 0, &vmo);
+  if (status != MX_OK) {
+    if (status != MX_ERR_NO_MEMORY || die_for_nomem)
+      ReportMmapFailureAndDie(size, kAllocatorVmoName,
+                              "mx_vmo_create", status);
+    return nullptr;
+  }
+  _mx_object_set_property(vmo, MX_PROP_NAME,
+                          kAllocatorVmoName, sizeof(kAllocatorVmoName) - 1);
+
+  DCHECK_GE(fixed_addr, allocator_vmar_base);
+  uintptr_t offset = fixed_addr - allocator_vmar_base;
+  DCHECK_LE(size, allocator_vmar_size);
+  DCHECK_GE(allocator_vmar_size - offset, size);
+
+  uintptr_t addr;
+  status = _mx_vmar_map(allocator_vmar, offset, vmo, 0, size,
+                        MX_VM_FLAG_PERM_READ | MX_VM_FLAG_PERM_WRITE |
+                        MX_VM_FLAG_SPECIFIC,
+                        &addr);
+  _mx_handle_close(vmo);
+  if (status != MX_OK) {
+    if (status != MX_ERR_NO_MEMORY || die_for_nomem)
+      ReportMmapFailureAndDie(size, kAllocatorVmoName, "mx_vmar_map", status);
+    return nullptr;
+  }
+
+  IncreaseTotalMmap(size);
+
+  return reinterpret_cast<void *>(addr);
+}
+
+void *MmapFixedOrDie(uptr fixed_addr, uptr size) {
+  return DoMmapFixedOrDie(fixed_addr, size, true);
+}
+
+void *MmapFixedOrDieOnFatalError(uptr fixed_addr, uptr size) {
+  return DoMmapFixedOrDie(fixed_addr, size, false);
+}
+
+// This should never be called.
+void *MmapFixedNoAccess(uptr fixed_addr, uptr size, const char *name) {
+  UNIMPLEMENTED();
+}
+
+void *MmapAlignedOrDieOnFatalError(uptr size, uptr alignment,
+                                   const char *mem_type) {
+  CHECK_GE(size, PAGE_SIZE);
+  CHECK(IsPowerOfTwo(size));
+  CHECK(IsPowerOfTwo(alignment));
+
+  mx_handle_t vmo;
+  mx_status_t status = _mx_vmo_create(size, 0, &vmo);
+  if (status != MX_OK) {
+    if (status != MX_ERR_NO_MEMORY)
+      ReportMmapFailureAndDie(size, mem_type, "mx_vmo_create", status, false);
+    return nullptr;
+  }
+  _mx_object_set_property(vmo, MX_PROP_NAME,
+                          mem_type, internal_strlen(mem_type));
+
+  // TODO(mcgrathr): Maybe allocate a VMAR for all sanitizer heap and use that?
+
+  // Map a larger size to get a chunk of address space big enough that
+  // it surely contains an aligned region of the requested size.  Then
+  // overwrite the aligned middle portion with a mapping from the
+  // beginning of the VMO, and unmap the excess before and after.
+  size_t map_size = size + alignment;
+  uintptr_t addr;
+  status = _mx_vmar_map(_mx_vmar_root_self(), 0, vmo, 0, map_size,
+                        MX_VM_FLAG_PERM_READ | MX_VM_FLAG_PERM_WRITE, &addr);
+  if (status == MX_OK) {
+    uintptr_t map_addr = addr;
+    uintptr_t map_end = map_addr + map_size;
+    addr = RoundUpTo(map_addr, alignment);
+    uintptr_t end = addr + size;
+    if (addr != map_addr) {
+      mx_info_vmar_t info;
+      status = _mx_object_get_info(_mx_vmar_root_self(), MX_INFO_VMAR,
+                                   &info, sizeof(info), NULL, NULL);
+      if (status == MX_OK) {
+        uintptr_t new_addr;
+        status = _mx_vmar_map(_mx_vmar_root_self(), addr - info.base,
+                              vmo, 0, size,
+                              MX_VM_FLAG_PERM_READ | MX_VM_FLAG_PERM_WRITE |
+                              MX_VM_FLAG_SPECIFIC_OVERWRITE,
+                              &new_addr);
+        if (status == MX_OK)
+          CHECK_EQ(new_addr, addr);
+      }
+    }
+    if (status == MX_OK && addr != map_addr)
+      status = _mx_vmar_unmap(_mx_vmar_root_self(), map_addr, addr - map_addr);
+    if (status == MX_OK && end != map_end)
+      status = _mx_vmar_unmap(_mx_vmar_root_self(), end, map_end - end);
+  }
+  _mx_handle_close(vmo);
+
+  if (status != MX_OK) {
+    if (status != MX_ERR_NO_MEMORY)
+      ReportMmapFailureAndDie(size, mem_type, "mx_vmar_map", status, false);
+    return nullptr;
+  }
+
+  IncreaseTotalMmap(size);
+
+  return reinterpret_cast<void *>(addr);
+}
+
+void UnmapOrDie(void *addr, uptr size) {
+  if (!addr || !size) return;
+  size = RoundUpTo(size, PAGE_SIZE);
+
+  mx_status_t status = _mx_vmar_unmap(_mx_vmar_root_self(),
+                                      reinterpret_cast<uintptr_t>(addr), size);
+  if (status != MX_OK) {
+    Report("ERROR: %s failed to deallocate 0x%zx (%zd) bytes at address %p\n",
+           SanitizerToolName, size, size, addr);
+    CHECK("unable to unmap" && 0);
+  }
+
+  DecreaseTotalMmap(size);
+}
+
+// This is used on the shadow mapping, which cannot be changed.
+// Magenta doesn't have anything like MADV_DONTNEED.
+void ReleaseMemoryPagesToOS(uptr beg, uptr end) {
+}
+
+void DumpProcessMap() {
+  UNIMPLEMENTED(); // TODO(mcgrathr): write it
+}
+
+bool IsAccessibleMemoryRange(uptr beg, uptr size) {
+  // TODO(mcgrathr): Figure out a better way.
+  mx_handle_t vmo;
+  mx_status_t status = _mx_vmo_create(size, 0, &vmo);
+  if (status == MX_OK) {
+    while (size > 0) {
+      size_t wrote;
+      status = _mx_vmo_write(vmo, reinterpret_cast<const void *>(beg), 0, size,
+                             &wrote);
+      if (status != MX_OK)
+        break;
+      CHECK_GT(wrote, 0);
+      CHECK_LE(wrote, size);
+      beg += wrote;
+      size -= wrote;
+    }
+    _mx_handle_close(vmo);
+  }
+  return status == MX_OK;
+}
+
+// FIXME implement on this platform.
+void GetMemoryProfile(fill_profile_f cb, uptr *stats, uptr stats_size) { }
+
+bool ReadFileToBuffer(const char *file_name, char **buff, uptr *buff_size,
+                      uptr *read_len, uptr max_len, error_t *errno_p) {
+  mx_handle_t vmo;
+  mx_status_t status = __sanitizer_get_configuration(file_name, &vmo);
+  if (status == MX_OK) {
+    uint64_t vmo_size;
+    status = _mx_vmo_get_size(vmo, &vmo_size);
+    if (status == MX_OK) {
+      if (vmo_size < max_len)
+        max_len = vmo_size;
+      size_t map_size = RoundUpTo(max_len, PAGE_SIZE);
+      uintptr_t addr;
+      status = _mx_vmar_map(_mx_vmar_root_self(), 0, vmo, 0, map_size,
+                            MX_VM_FLAG_PERM_READ, &addr);
+      if (status == MX_OK) {
+        *buff = reinterpret_cast<char *>(addr);
+        *buff_size = map_size;
+        *read_len = max_len;
+      }
+    }
+    _mx_handle_close(vmo);
+  }
+  if (status != MX_OK && errno_p)
+    *errno_p = status;
+  return status == MX_OK;
+}
+
+void RawWrite(const char *buffer) {
+  __sanitizer_log_write(buffer, internal_strlen(buffer));
+}
+
+void CatastrophicErrorWrite(const char *buffer, uptr length) {
+  __sanitizer_log_write(buffer, length);
+}
+
+char **StoredArgv;
+char **StoredEnviron;
+
+char** GetArgv() {
+  return StoredArgv;
+}
+
+const char *GetEnv(const char *name) {
+  if (StoredEnviron) {
+    uptr NameLen = internal_strlen(name);
+    for (char **Env = StoredEnviron; *Env != 0; Env++) {
+      if (internal_strncmp(*Env, name, NameLen) == 0 && (*Env)[NameLen] == '=')
+        return (*Env) + NameLen + 1;
+    }
+  }
+  return nullptr;
+}
+
+uptr ReadBinaryName(/*out*/char *buf, uptr buf_len) {
+  const char *argv0 = StoredArgv[0];
+  if (!argv0)
+    argv0 = "<UNKNOWN>";
+  internal_strncpy(buf, argv0, buf_len);
+  return internal_strlen(buf);
+}
+
+uptr ReadLongProcessName(/*out*/ char *buf, uptr buf_len) {
+  return ReadBinaryName(buf, buf_len);
+}
+
+uptr MainThreadStackBase, MainThreadStackSize;
+
+}  // namespace __sanitizer
+
+using namespace __sanitizer;  // NOLINT
+
+extern "C" {
+void __sanitizer_startup_hook(int argc, char** argv, char** envp,
+                              void* stack_base, size_t stack_size) {
+  __sanitizer::StoredArgv = argv;
+  __sanitizer::StoredEnviron = envp;
+  __sanitizer::MainThreadStackBase = reinterpret_cast<uintptr_t>(stack_base);
+  __sanitizer::MainThreadStackSize = stack_size;
+}
+
+void __sanitizer_set_report_path(const char *path) {
+  // Handle the initialization code in each sanitizer, but no other calls.
+  // This setting is never consulted on Fuchsia.
+  DCHECK_EQ(path, common_flags()->log_path);
+}
+
+void __sanitizer_set_report_fd(void *fd) {
+  UNREACHABLE("not available on Fuchsia");
+}
+} // extern "C"
+
+#endif // SANITIZER_FUCHSIA

lib/sanitizer_common/sanitizer_printf.cc

for (int use_mmap = 0; use_mmap < 2; use_mmap++) {
     needed_length = 0;
     // Check that data fits into the current buffer.
 #   define CHECK_NEEDED_LENGTH \
       if (needed_length >= buffer_size) { \
         if (!use_mmap) continue; \
         RAW_CHECK_MSG(needed_length < kLen, \
                       "Buffer in Report is too short!\n"); \
       }
-    if (append_pid) {
+    // Fuchsia's logging infrastructure always keeps track of the logging
+    // process, thread, and timestamp, so never prepend such information.
+    if (!SANITIZER_FUCHSIA && append_pid) {
       int pid = internal_getpid();
       const char *exe_name = GetProcessName();
       if (common_flags()->log_exe_name && exe_name) {
         needed_length += internal_snprintf(buffer, buffer_size,
                                            "==%s", exe_name);
         CHECK_NEEDED_LENGTH
       }
       needed_length += internal_snprintf(