Enable one PID namespace per process for NaCl processes.

sandbox/linux/services/namespace_sandbox.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef SANDBOX_LINUX_SERVICES_NAMESPACE_SANDBOX_H_
 #define SANDBOX_LINUX_SERVICES_NAMESPACE_SANDBOX_H_
 
 #include <sys/types.h>
 
 #include <string>
@@ skipping 19 matching lines @@
 //    not have an explicit signal handler registered.
 //    If B dies, all the processes in the namespace will die.
 //    B can fork() and the parent can assume the role of init(1), by using
 //    CreateInitProcessReaper().
 // 4. B chroots using Credentials::MoveToNewUserNS() and
 //    Credentials::DropFileSystemAccess()
 // 5. B drops capabilities gained by entering the new user namespace with
 //    Credentials::DropAllCapabilities().
 class SANDBOX_EXPORT NamespaceSandbox {
  public:
-  static const int kDefaultExitCode = 1;
-
 #if !defined(OS_NACL_NONSFI)
   // Launch a new process inside its own user/PID/network namespaces (depending
   // on kernel support). Requires at a minimum that user namespaces are
   // supported (use Credentials::CanCreateProcessInNewUserNS to check this).
   //
   // pre_exec_delegate and clone_flags fields of LaunchOptions should be nullptr
   // and 0, respectively, since this function makes a copy of options and
   // overrides them.
   static base::Process LaunchProcess(const base::CommandLine& cmdline,
                                      const base::LaunchOptions& options);
@@ skipping 12 matching lines @@
   // processes ignore such signals unless they have an explicit handler set.
   //
   // This function requries CAP_SYS_ADMIN. If |drop_capabilities_in_child| is
   // true, then capabilities are dropped in the child.
   static pid_t ForkInNewPidNamespace(bool drop_capabilities_in_child);
 
   // Installs a signal handler for:
   //
   // SIGHUP, SIGINT, SIGABRT, SIGQUIT, SIGPIPE, SIGTERM, SIGUSR1, SIGUSR2
   //
-  // that exits with kDefaultExitCode. These are signals whose default action is
-  // to terminate the program (apart from SIGILL, SIGFPE, and SIGSEGV, which
+  // that exits with SignalExitCode(sig). These are signals whose default action
+  // is to terminate the program (apart from SIGILL, SIGFPE, and SIGSEGV, which
   // will still terminate the process if e.g. an illegal instruction is
   // encountered, etc.).
   //
   // If any of these already had a signal handler installed, this function will
   // not override them.
   static void InstallDefaultTerminationSignalHandlers();
 
   // Installs a signal handler for |sig| which exits with |exit_code|. If a
   // signal handler was already present for |sig|, does nothing and returns
   // false.
   static bool InstallTerminationSignalHandler(int sig, int exit_code);
 
+  // Returns an exit code corresponding to the process being killed by sig. This
+  // is the same as exit code that NaCl's default signal handler uses.
+  static int SignalExitCode(int sig) { return -sig & 0xff; }
+
   // Returns whether the namespace sandbox created a new user, PID, and network
   // namespace. In particular, InNewUserNamespace should return true iff the
   // process was started via this class.
   static bool InNewUserNamespace();
   static bool InNewPidNamespace();
   static bool InNewNetNamespace();
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(NamespaceSandbox);
 };
 
 }  // namespace sandbox
 
 #endif  // SANDBOX_LINUX_SERVICES_NAMESPACE_SANDBOX_H_