Transform ProcessLauncherLinux to ProcessLauncherPosixFork

[krytarowski]

Summary

Use ProcessLauncherPosixFork in Linux and NetBSD.

Changes to ProcessLauncherLinux:

• Limit personality.h and ASLR code to Linux.
• Reuse portable ptrace(2) PT_TRACE_ME operation available on Linux and BSDs.
• Limit ETXTBSY error path from execve(2) to Linux.
• In LaunchProcess declaration change virtual to override.

This code should be readily available for FreeBSD.

Sponsored by <The NetBSD Foundation>

[labath]

This is also copying a lot of code only to make tiny changes to it. Please put the Linux process launcher into the posix folder (I suggest naming it ProcessLauncherPosixFork). Ifdef out the linux-specific parts (ASLR, personality) and you're done. :)

For bonus points, you can put the ASLR code into a separate function, and then ifdef-out only that - should make main code flow better.

[krytarowski]

This patch was already open in a discussion with @labath, I'm pushing it here to point the appropriate solution during review.

[krytarowski]

In D29347#662145, @labath wrote:

This is also copying a lot of code only to make tiny changes to it. Please put the Linux process launcher into the posix folder (I suggest naming it ProcessLauncherPosixFork). Ifdef out the linux-specific parts (ASLR, personality) and you're done. :)

For bonus points, you can put the ASLR code into a separate function, and then ifdef-out only that - should make main code flow better.

I will do it. Thank you for quick reply.

[krytarowski]

Transform ProcessLauncherLinux to ProcessLauncherPosixFork and attach to Linux and NetBSD.

[krytarowski]

Fix typo.

[labath]

Perfect. Thank you.

include/lldb/Host/posix/ProcessLauncherPosixFork.h

20

s/virtual/override/. (I know you just copied it, but still.. )

[labath]

@emaste: I'd suggest switching freebsd over to this process launcher as well. I think it's the last user of the ProcessLauncherPosix, and it would enable us to get rid of it.

[krytarowski]

virtual -> override

[emaste]

In D29347#662503, @labath wrote:

@emaste: I'd suggest switching freebsd over to this process launcher as well. I think it's the last user of the ProcessLauncherPosix, and it would enable us to get rid of it.

Indeed. I won't be able to look at it until next week, but will try to switch it over as soon as possible.

include/lldb/Host/linux/ProcessLauncherLinux.h

-//===-- ProcessLauncherAndroid.h --------------------------------*- C++ -*-===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef lldb_Host_android_ProcessLauncherAndroid_h_
-#define lldb_Host_android_ProcessLauncherAndroid_h_
-
-#include "lldb/Host/ProcessLauncher.h"
-
-namespace lldb_private {
-
-class ProcessLauncherLinux : public ProcessLauncher {
-public:
-  virtual HostProcess LaunchProcess(const ProcessLaunchInfo &launch_info,
-                                    Error &error);
-};
-
-} // end of namespace lldb_private
-
-#endif

include/lldb/Host/posix/ProcessLauncherPosixFork.h

+//===-- ProcessLauncherPosixFork.h ------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef lldb_Host_posix_ProcessLauncherPosixFork_h_
+#define lldb_Host_posix_ProcessLauncherPosixFork_h_
+
+#include "lldb/Host/ProcessLauncher.h"
+
+namespace lldb_private {
+
+class ProcessLauncherPosixFork : public ProcessLauncher {
+public:
+  HostProcess LaunchProcess(const ProcessLaunchInfo &launch_info,
+                            Error &error) override;
+};
+
+} // end of namespace lldb_private
+
+#endif

source/Host/CMakeLists.txt

add_host_subdirectory(posix
     posix/DomainSocket.cpp
     posix/FileSystem.cpp
     posix/HostInfoPosix.cpp
     posix/HostProcessPosix.cpp
     posix/HostThreadPosix.cpp
     posix/LockFilePosix.cpp
     posix/MainLoopPosix.cpp
     posix/PipePosix.cpp
+    posix/ProcessLauncherPosixFork.cpp
     )
 
   if (NOT (CMAKE_SYSTEM_NAME MATCHES "Android"))
     add_host_subdirectory(posix
       posix/ProcessLauncherPosix.cpp
       )
   endif()
 
else()
 
   elseif (CMAKE_SYSTEM_NAME MATCHES "Linux|Android")
     add_host_subdirectory(linux
       linux/AbstractSocket.cpp
       linux/Host.cpp
       linux/HostInfoLinux.cpp
       linux/HostThreadLinux.cpp
       linux/LibcGlue.cpp
-      linux/ProcessLauncherLinux.cpp
       linux/ThisThread.cpp
       )
     list(APPEND LLDB_PLUGINS lldbPluginProcessLinux)
     if (CMAKE_SYSTEM_NAME MATCHES "Android")
       add_host_subdirectory(android
         android/HostInfoAndroid.cpp
         android/LibcGlue.cpp
         )

source/Host/common/Host.cpp

 #include "lldb/Target/UnixSignals.h"
 #include "lldb/Utility/CleanUp.h"
 #include "lldb/lldb-private-forward.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/Support/FileSystem.h"
 
 #if defined(_WIN32)
 #include "lldb/Host/windows/ProcessLauncherWindows.h"
-#elif defined(__linux__)
-#include "lldb/Host/linux/ProcessLauncherLinux.h"
+#elif defined(__linux__) || defined(__NetBSD__)
+#include "lldb/Host/posix/ProcessLauncherPosixFork.h"
 #else
 #include "lldb/Host/posix/ProcessLauncherPosix.h"
 #endif
 
 #if defined(__APPLE__)
 #ifndef _POSIX_SPAWN_DISABLE_ASLR
 #define _POSIX_SPAWN_DISABLE_ASLR 0x0100
 #endif
#if defined(__linux__) || defined(__FreeBSD__) || defined(__GLIBC__) ||        \
     defined(__NetBSD__) || defined(_WIN32)
 // The functions below implement process launching via posix_spawn() for Linux,
 // FreeBSD and NetBSD.
 
 Error Host::LaunchProcess(ProcessLaunchInfo &launch_info) {
   std::unique_ptr<ProcessLauncher> delegate_launcher;
 #if defined(_WIN32)
   delegate_launcher.reset(new ProcessLauncherWindows());
-#elif defined(__linux__)
-  delegate_launcher.reset(new ProcessLauncherLinux());
+#elif defined(__linux__) || defined(__NetBSD__)
+  delegate_launcher.reset(new ProcessLauncherPosixFork());
 #else
   delegate_launcher.reset(new ProcessLauncherPosix());
 #endif
   MonitoringProcessLauncher launcher(std::move(delegate_launcher));
 
   Error error;
   HostProcess process = launcher.LaunchProcess(launch_info, error);
 

source/Host/linux/ProcessLauncherLinux.cpp

-//===-- ProcessLauncherLinux.cpp --------------------------------*- C++ -*-===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-
-#include "lldb/Host/linux/ProcessLauncherLinux.h"
-#include "lldb/Core/Log.h"
-#include "lldb/Host/FileSpec.h"
-#include "lldb/Host/Host.h"
-#include "lldb/Host/HostProcess.h"
-#include "lldb/Host/Pipe.h"
-#include "lldb/Target/ProcessLaunchInfo.h"
-
-#include <limits.h>
-#include <sys/ptrace.h>
-#include <sys/wait.h>
-
-#include <sstream>
-
-#ifdef __ANDROID__
-#include <android/api-level.h>
-#endif
-
-#if defined(__ANDROID_API__) && __ANDROID_API__ < 21
-#include <linux/personality.h>
-#else
-#include <sys/personality.h>
-#endif
-
-using namespace lldb;
-using namespace lldb_private;
-
-static void FixupEnvironment(Args &env) {
-#ifdef __ANDROID__
-  // If there is no PATH variable specified inside the environment then set the
-  // path to /system/bin. It is required because the default path used by
-  // execve() is wrong on android.
-  static const char *path = "PATH=";
-  for (auto &entry : env.entries()) {
-    if (entry.ref.startswith(path))
-      return;
-  }
-  env.AppendArgument(llvm::StringRef("PATH=/system/bin"));
-#endif
-}
-
-static void LLVM_ATTRIBUTE_NORETURN ExitWithError(int error_fd,
-                                                  const char *operation) {
-  std::ostringstream os;
-  os << operation << " failed: " << strerror(errno);
-  write(error_fd, os.str().data(), os.str().size());
-  close(error_fd);
-  _exit(1);
-}
-
-static void DupDescriptor(int error_fd, const FileSpec &file_spec, int fd,
-                          int flags) {
-  int target_fd = ::open(file_spec.GetCString(), flags, 0666);
-
-  if (target_fd == -1)
-    ExitWithError(error_fd, "DupDescriptor-open");
-
-  if (target_fd == fd)
-    return;
-
-  if (::dup2(target_fd, fd) == -1)
-    ExitWithError(error_fd, "DupDescriptor-dup2");
-
-  ::close(target_fd);
-  return;
-}
-
-static void LLVM_ATTRIBUTE_NORETURN ChildFunc(int error_fd,
-                                              const ProcessLaunchInfo &info) {
-  // First, make sure we disable all logging. If we are logging to stdout, our
-  // logs can be
-  // mistaken for inferior output.
-  Log::DisableAllLogChannels(nullptr);
-
-  // Do not inherit setgid powers.
-  if (setgid(getgid()) != 0)
-    ExitWithError(error_fd, "setgid");
-
-  if (info.GetFlags().Test(eLaunchFlagLaunchInSeparateProcessGroup)) {
-    if (setpgid(0, 0) != 0)
-      ExitWithError(error_fd, "setpgid");
-  }
-
-  for (size_t i = 0; i < info.GetNumFileActions(); ++i) {
-    const FileAction &action = *info.GetFileActionAtIndex(i);
-    switch (action.GetAction()) {
-    case FileAction::eFileActionClose:
-      if (close(action.GetFD()) != 0)
-        ExitWithError(error_fd, "close");
-      break;
-    case FileAction::eFileActionDuplicate:
-      if (dup2(action.GetFD(), action.GetActionArgument()) == -1)
-        ExitWithError(error_fd, "dup2");
-      break;
-    case FileAction::eFileActionOpen:
-      DupDescriptor(error_fd, action.GetFileSpec(), action.GetFD(),
-                    action.GetActionArgument());
-      break;
-    case FileAction::eFileActionNone:
-      break;
-    }
-  }
-
-  const char **argv = info.GetArguments().GetConstArgumentVector();
-
-  // Change working directory
-  if (info.GetWorkingDirectory() &&
-      0 != ::chdir(info.GetWorkingDirectory().GetCString()))
-    ExitWithError(error_fd, "chdir");
-
-  // Disable ASLR if requested.
-  if (info.GetFlags().Test(lldb::eLaunchFlagDisableASLR)) {
-    const unsigned long personality_get_current = 0xffffffff;
-    int value = personality(personality_get_current);
-    if (value == -1)
-      ExitWithError(error_fd, "personality get");
-
-    value = personality(ADDR_NO_RANDOMIZE | value);
-    if (value == -1)
-      ExitWithError(error_fd, "personality set");
-  }
-
-  Args env = info.GetEnvironmentEntries();
-  FixupEnvironment(env);
-  const char **envp = env.GetConstArgumentVector();
-
-  // Clear the signal mask to prevent the child from being affected by
-  // any masking done by the parent.
-  sigset_t set;
-  if (sigemptyset(&set) != 0 ||
-      pthread_sigmask(SIG_SETMASK, &set, nullptr) != 0)
-    ExitWithError(error_fd, "pthread_sigmask");
-
-  if (info.GetFlags().Test(eLaunchFlagDebug)) {
-    // HACK:
-    // Close everything besides stdin, stdout, and stderr that has no file
-    // action to avoid leaking. Only do this when debugging, as elsewhere we
-    // actually rely on
-    // passing open descriptors to child processes.
-    for (int fd = 3; fd < sysconf(_SC_OPEN_MAX); ++fd)
-      if (!info.GetFileActionForFD(fd) && fd != error_fd)
-        close(fd);
-
-    // Start tracing this child that is about to exec.
-    if (ptrace(PTRACE_TRACEME, 0, nullptr, nullptr) == -1)
-      ExitWithError(error_fd, "ptrace");
-  }
-
-  // Execute.  We should never return...
-  execve(argv[0], const_cast<char *const *>(argv),
-         const_cast<char *const *>(envp));
-
-  if (errno == ETXTBSY) {
-    // On android M and earlier we can get this error because the adb deamon can
-    // hold a write
-    // handle on the executable even after it has finished uploading it. This
-    // state lasts
-    // only a short time and happens only when there are many concurrent adb
-    // commands being
-    // issued, such as when running the test suite. (The file remains open when
-    // someone does
-    // an "adb shell" command in the fork() child before it has had a chance to
-    // exec.) Since
-    // this state should clear up quickly, wait a while and then give it one
-    // more go.
-    usleep(50000);
-    execve(argv[0], const_cast<char *const *>(argv),
-           const_cast<char *const *>(envp));
-  }
-
-  // ...unless exec fails.  In which case we definitely need to end the child
-  // here.
-  ExitWithError(error_fd, "execve");
-}
-
-HostProcess
-ProcessLauncherLinux::LaunchProcess(const ProcessLaunchInfo &launch_info,
-                                    Error &error) {
-  char exe_path[PATH_MAX];
-  launch_info.GetExecutableFile().GetPath(exe_path, sizeof(exe_path));
-
-  // A pipe used by the child process to report errors.
-  PipePosix pipe;
-  const bool child_processes_inherit = false;
-  error = pipe.CreateNew(child_processes_inherit);
-  if (error.Fail())
-    return HostProcess();
-
-  ::pid_t pid = ::fork();
-  if (pid == -1) {
-    // Fork failed
-    error.SetErrorStringWithFormat("Fork failed with error message: %s",
-                                   strerror(errno));
-    return HostProcess(LLDB_INVALID_PROCESS_ID);
-  }
-  if (pid == 0) {
-    // child process
-    pipe.CloseReadFileDescriptor();
-    ChildFunc(pipe.ReleaseWriteFileDescriptor(), launch_info);
-  }
-
-  // parent process
-
-  pipe.CloseWriteFileDescriptor();
-  char buf[1000];
-  int r = read(pipe.GetReadFileDescriptor(), buf, sizeof buf);
-
-  if (r == 0)
-    return HostProcess(pid); // No error. We're done.
-
-  error.SetErrorString(buf);
-
-  waitpid(pid, nullptr, 0);
-
-  return HostProcess();
-}

source/Host/posix/ProcessLauncherPosixFork.cpp

+//===-- ProcessLauncherLinux.cpp --------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "lldb/Host/posix/ProcessLauncherPosixFork.h"
+#include "lldb/Core/Log.h"
+#include "lldb/Host/FileSpec.h"
+#include "lldb/Host/Host.h"
+#include "lldb/Host/HostProcess.h"
+#include "lldb/Host/Pipe.h"
+#include "lldb/Target/ProcessLaunchInfo.h"
+
+#include <limits.h>
+#include <sys/ptrace.h>
+#include <sys/wait.h>
+
+#include <sstream>
+
+#ifdef __ANDROID__
+#include <android/api-level.h>
+#endif
+
+#if defined(__ANDROID_API__) && __ANDROID_API__ < 21
+#include <linux/personality.h>
+#elif defined(__linux__)
+#include <sys/personality.h>
+#endif
+
+using namespace lldb;
+using namespace lldb_private;
+
+static void FixupEnvironment(Args &env) {
+#ifdef __ANDROID__
+  // If there is no PATH variable specified inside the environment then set the
+  // path to /system/bin. It is required because the default path used by
+  // execve() is wrong on android.
+  static const char *path = "PATH=";
+  for (auto &entry : env.entries()) {
+    if (entry.ref.startswith(path))
+      return;
+  }
+  env.AppendArgument(llvm::StringRef("PATH=/system/bin"));
+#endif
+}
+
+static void LLVM_ATTRIBUTE_NORETURN ExitWithError(int error_fd,
+                                                  const char *operation) {
+  std::ostringstream os;
+  os << operation << " failed: " << strerror(errno);
+  write(error_fd, os.str().data(), os.str().size());
+  close(error_fd);
+  _exit(1);
+}
+
+static void DisableASLRIfRequested(int error_fd, const ProcessLaunchInfo &info) {
+#if defined(__linux__)
+  if (info.GetFlags().Test(lldb::eLaunchFlagDisableASLR)) {
+    const unsigned long personality_get_current = 0xffffffff;
+    int value = personality(personality_get_current);
+    if (value == -1)
+      ExitWithError(error_fd, "personality get");
+
+    value = personality(ADDR_NO_RANDOMIZE | value);
+    if (value == -1)
+      ExitWithError(error_fd, "personality set");
+  }
+#endif
+}
+
+static void DupDescriptor(int error_fd, const FileSpec &file_spec, int fd,
+                          int flags) {
+  int target_fd = ::open(file_spec.GetCString(), flags, 0666);
+
+  if (target_fd == -1)
+    ExitWithError(error_fd, "DupDescriptor-open");
+
+  if (target_fd == fd)
+    return;
+
+  if (::dup2(target_fd, fd) == -1)
+    ExitWithError(error_fd, "DupDescriptor-dup2");
+
+  ::close(target_fd);
+  return;
+}
+
+static void LLVM_ATTRIBUTE_NORETURN ChildFunc(int error_fd,
+                                              const ProcessLaunchInfo &info) {
+  // First, make sure we disable all logging. If we are logging to stdout, our
+  // logs can be
+  // mistaken for inferior output.
+  Log::DisableAllLogChannels(nullptr);
+
+  // Do not inherit setgid powers.
+  if (setgid(getgid()) != 0)
+    ExitWithError(error_fd, "setgid");
+
+  if (info.GetFlags().Test(eLaunchFlagLaunchInSeparateProcessGroup)) {
+    if (setpgid(0, 0) != 0)
+      ExitWithError(error_fd, "setpgid");
+  }
+
+  for (size_t i = 0; i < info.GetNumFileActions(); ++i) {
+    const FileAction &action = *info.GetFileActionAtIndex(i);
+    switch (action.GetAction()) {
+    case FileAction::eFileActionClose:
+      if (close(action.GetFD()) != 0)
+        ExitWithError(error_fd, "close");
+      break;
+    case FileAction::eFileActionDuplicate:
+      if (dup2(action.GetFD(), action.GetActionArgument()) == -1)
+        ExitWithError(error_fd, "dup2");
+      break;
+    case FileAction::eFileActionOpen:
+      DupDescriptor(error_fd, action.GetFileSpec(), action.GetFD(),
+                    action.GetActionArgument());
+      break;
+    case FileAction::eFileActionNone:
+      break;
+    }
+  }
+
+  const char **argv = info.GetArguments().GetConstArgumentVector();
+
+  // Change working directory
+  if (info.GetWorkingDirectory() &&
+      0 != ::chdir(info.GetWorkingDirectory().GetCString()))
+    ExitWithError(error_fd, "chdir");
+
+  DisableASLRIfRequested(error_fd, info);
+  Args env = info.GetEnvironmentEntries();
+  FixupEnvironment(env);
+  const char **envp = env.GetConstArgumentVector();
+
+  // Clear the signal mask to prevent the child from being affected by
+  // any masking done by the parent.
+  sigset_t set;
+  if (sigemptyset(&set) != 0 ||
+      pthread_sigmask(SIG_SETMASK, &set, nullptr) != 0)
+    ExitWithError(error_fd, "pthread_sigmask");
+
+  if (info.GetFlags().Test(eLaunchFlagDebug)) {
+    // HACK:
+    // Close everything besides stdin, stdout, and stderr that has no file
+    // action to avoid leaking. Only do this when debugging, as elsewhere we
+    // actually rely on
+    // passing open descriptors to child processes.
+    for (int fd = 3; fd < sysconf(_SC_OPEN_MAX); ++fd)
+      if (!info.GetFileActionForFD(fd) && fd != error_fd)
+        close(fd);
+
+    // Start tracing this child that is about to exec.
+    if (ptrace(PT_TRACE_ME, 0, nullptr, 0) == -1)
+      ExitWithError(error_fd, "ptrace");
+  }
+
+  // Execute.  We should never return...
+  execve(argv[0], const_cast<char *const *>(argv),
+         const_cast<char *const *>(envp));
+
+#if defined(__linux__)
+  if (errno == ETXTBSY) {
+    // On android M and earlier we can get this error because the adb deamon can
+    // hold a write
+    // handle on the executable even after it has finished uploading it. This
+    // state lasts
+    // only a short time and happens only when there are many concurrent adb
+    // commands being
+    // issued, such as when running the test suite. (The file remains open when
+    // someone does
+    // an "adb shell" command in the fork() child before it has had a chance to
+    // exec.) Since
+    // this state should clear up quickly, wait a while and then give it one
+    // more go.
+    usleep(50000);
+    execve(argv[0], const_cast<char *const *>(argv),
+           const_cast<char *const *>(envp));
+  }
+#endif
+
+  // ...unless exec fails.  In which case we definitely need to end the child
+  // here.
+  ExitWithError(error_fd, "execve");
+}
+
+HostProcess
+ProcessLauncherPosixFork::LaunchProcess(const ProcessLaunchInfo &launch_info,
+                                        Error &error) {
+  char exe_path[PATH_MAX];
+  launch_info.GetExecutableFile().GetPath(exe_path, sizeof(exe_path));
+
+  // A pipe used by the child process to report errors.
+  PipePosix pipe;
+  const bool child_processes_inherit = false;
+  error = pipe.CreateNew(child_processes_inherit);
+  if (error.Fail())
+    return HostProcess();
+
+  ::pid_t pid = ::fork();
+  if (pid == -1) {
+    // Fork failed
+    error.SetErrorStringWithFormat("Fork failed with error message: %s",
+                                   strerror(errno));
+    return HostProcess(LLDB_INVALID_PROCESS_ID);
+  }
+  if (pid == 0) {
+    // child process
+    pipe.CloseReadFileDescriptor();
+    ChildFunc(pipe.ReleaseWriteFileDescriptor(), launch_info);
+  }
+
+  // parent process
+
+  pipe.CloseWriteFileDescriptor();
+  char buf[1000];
+  int r = read(pipe.GetReadFileDescriptor(), buf, sizeof buf);
+
+  if (r == 0)
+    return HostProcess(pid); // No error. We're done.
+
+  error.SetErrorString(buf);
+
+  waitpid(pid, nullptr, 0);
+
+  return HostProcess();
+}

source/Plugins/Process/Linux/NativeProcessLinux.cpp

 #include "lldb/Core/ModuleSpec.h"
 #include "lldb/Core/RegisterValue.h"
 #include "lldb/Core/State.h"
 #include "lldb/Host/Host.h"
 #include "lldb/Host/HostProcess.h"
 #include "lldb/Host/ThreadLauncher.h"
 #include "lldb/Host/common/NativeBreakpoint.h"
 #include "lldb/Host/common/NativeRegisterContext.h"
-#include "lldb/Host/linux/ProcessLauncherLinux.h"
+#include "lldb/Host/posix/ProcessLauncherPosixFork.h"
 #include "lldb/Symbol/ObjectFile.h"
 #include "lldb/Target/Process.h"
 #include "lldb/Target/ProcessLaunchInfo.h"
 #include "lldb/Target/Target.h"
 #include "lldb/Utility/LLDBAssert.h"
 #include "lldb/Utility/PseudoTerminal.h"
 #include "lldb/Utility/StringExtractor.h"
 
Error NativeProcessLinux::LaunchInferior(MainLoop &mainloop,
   if (!m_sigchld_handle)
     return error;
 
   SetState(eStateLaunching);
 
   MaybeLogLaunchInfo(launch_info);
 
   ::pid_t pid =
-      ProcessLauncherLinux().LaunchProcess(launch_info, error).GetProcessId();
+      ProcessLauncherPosixFork().LaunchProcess(launch_info, error).GetProcessId();
   if (error.Fail())
     return error;
 
   Log *log(ProcessPOSIXLog::GetLogIfAllCategoriesSet(POSIX_LOG_PROCESS));
 
   // Wait for the child process to trap on its call to execve.
   ::pid_t wpid;
   int status;