[dart:io] Namespaces for file IO

runtime/bin/process_linux.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
 #if defined(HOST_OS_LINUX)
 
 #include "bin/process.h"
 
 #include <errno.h>         // NOLINT
 #include <fcntl.h>         // NOLINT
 #include <poll.h>          // NOLINT
 #include <stdio.h>         // NOLINT
 #include <stdlib.h>        // NOLINT
 #include <string.h>        // NOLINT
 #include <sys/resource.h>  // NOLINT
 #include <sys/wait.h>      // NOLINT
 #include <unistd.h>        // NOLINT
 
 #include "bin/dartutils.h"
+#include "bin/directory.h"
 #include "bin/fdutils.h"
 #include "bin/file.h"
 #include "bin/lockers.h"
 #include "bin/log.h"
 #include "bin/reference_counting.h"
 #include "bin/thread.h"
 
 #include "platform/signal_blocker.h"
 #include "platform/utils.h"
 
@@ skipping 205 matching lines @@
   DISALLOW_IMPLICIT_CONSTRUCTORS(ExitCodeHandler);
 };
 
 bool ExitCodeHandler::running_ = false;
 int ExitCodeHandler::process_count_ = 0;
 bool ExitCodeHandler::terminate_done_ = false;
 Monitor* ExitCodeHandler::monitor_ = new Monitor();
 
 class ProcessStarter {
  public:
-  ProcessStarter(const char* path,
+  ProcessStarter(Namespace* namespc,
+                 const char* path,
                  char* arguments[],
                  intptr_t arguments_length,
                  const char* working_directory,
                  char* environment[],
                  intptr_t environment_length,
                  ProcessStartMode mode,
                  intptr_t* in,
                  intptr_t* out,
                  intptr_t* err,
                  intptr_t* id,
                  intptr_t* exit_event,
                  char** os_error_message)
-      : path_(path),
+      : namespc_(namespc),
+        path_(path),
         working_directory_(working_directory),
         mode_(mode),
         in_(in),
         out_(out),
         err_(err),
         id_(id),
         exit_event_(exit_event),
         os_error_message_(os_error_message) {
     read_in_[0] = -1;
     read_in_[1] = -1;
@@ skipping 155 matching lines @@
       perror("Failed receiving notification message");
       exit(1);
     }
     if (mode_ == kNormal) {
       ExecProcess();
     } else {
       ExecDetachedProcess();
     }
   }
 
+  // If fexecve() should be used to launch the program, returns the fd to use
+  // in fd and returns true. If execvp should be used, returns false. If there
+  // was an error that should be reported to the caller, sets fd to -1 and
+  // returns true.
+  bool ShouldUseFexecve(int* pathfd) {
+    ASSERT(pathfd != NULL);
+    NamespaceScope ns(namespc_, path_);
+    const intptr_t fd =
+        TEMP_FAILURE_RETRY(openat64(ns.fd(), ns.path(), O_RDONLY));
+    if ((fd == -1) && (errno == ENOENT)) {
+      if (strchr(path_, '/') == NULL) {
+        // There wasn't in the namespace and contained no '/'. Punt to execvp.
+        return false;
+      }
+    }
+    *pathfd = fd;
+    return true;
+  }
+
   void ExecProcess() {
     if (TEMP_FAILURE_RETRY(dup2(write_out_[0], STDIN_FILENO)) == -1) {
       ReportChildError();
     }
 
     if (TEMP_FAILURE_RETRY(dup2(read_in_[1], STDOUT_FILENO)) == -1) {
       ReportChildError();
     }
 
     if (TEMP_FAILURE_RETRY(dup2(read_err_[1], STDERR_FILENO)) == -1) {
       ReportChildError();
     }
 
     if (working_directory_ != NULL &&
-        TEMP_FAILURE_RETRY(chdir(working_directory_)) == -1) {
+        !Directory::SetCurrent(namespc_, working_directory_)) {
       ReportChildError();
     }
 
     if (program_environment_ != NULL) {
       environ = program_environment_;
     }
 
-    VOID_TEMP_FAILURE_RETRY(
-        execvp(path_, const_cast<char* const*>(program_arguments_)));
+    int pathfd;
+    if (ShouldUseFexecve(&pathfd)) {
+      if (pathfd == -1) {
+        ReportChildError();
+      }
+      VOID_TEMP_FAILURE_RETRY(fexecve(
+          pathfd, const_cast<char* const*>(program_arguments_), environ));
+    } else {
+      VOID_TEMP_FAILURE_RETRY(
+          execvp(path_, const_cast<char* const*>(program_arguments_)));
+    }
 
     ReportChildError();
   }
 
   void ExecDetachedProcess() {
     if (mode_ == kDetached) {
       ASSERT(write_out_[0] == -1);
       ASSERT(write_out_[1] == -1);
       ASSERT(read_err_[0] == -1);
       ASSERT(read_err_[1] == -1);
@@ skipping 21 matching lines @@
         if (pid < 0) {
           ReportChildError();
         } else if (pid == 0) {
           if (mode_ == kDetached) {
             SetupDetached();
           } else {
             SetupDetachedWithStdio();
           }
 
           if ((working_directory_ != NULL) &&
-              (TEMP_FAILURE_RETRY(chdir(working_directory_)) == -1)) {
+              !Directory::SetCurrent(namespc_, working_directory_)) {
             ReportChildError();
           }
 
           // Report the final PID and do the exec.
           ReportPid(getpid());  // getpid cannot fail.
-          VOID_TEMP_FAILURE_RETRY(
-              execvp(path_, const_cast<char* const*>(program_arguments_)));
+          int pathfd;
+          if (ShouldUseFexecve(&pathfd)) {
+            if (pathfd == -1) {
+              ReportChildError();
+            }
+            VOID_TEMP_FAILURE_RETRY(fexecve(
+                pathfd, const_cast<char* const*>(program_arguments_), environ));
+          } else {
+            VOID_TEMP_FAILURE_RETRY(
+                execvp(path_, const_cast<char* const*>(program_arguments_)));
+          }
           ReportChildError();
         } else {
-          // Exit the intermeiate process.
+          // Exit the intermediate process.
           exit(0);
         }
       }
     } else {
-      // Exit the intermeiate process.
+      // Exit the intermediate process.
       exit(0);
     }
   }
 
   int RegisterProcess(pid_t pid) {
     int result;
     int event_fds[2];
     result = TEMP_FAILURE_RETRY(pipe2(event_fds, O_CLOEXEC));
     if (result < 0) {
       return CleanupAndReturnError();
@@ skipping 184 matching lines @@
   }
 
   int read_in_[2];       // Pipe for stdout to child process.
   int read_err_[2];      // Pipe for stderr to child process.
   int write_out_[2];     // Pipe for stdin to child process.
   int exec_control_[2];  // Pipe to get the result from exec.
 
   char** program_arguments_;
   char** program_environment_;
 
+  Namespace* namespc_;
   const char* path_;
   const char* working_directory_;
   ProcessStartMode mode_;
   intptr_t* in_;
   intptr_t* out_;
   intptr_t* err_;
   intptr_t* id_;
   intptr_t* exit_event_;
   char** os_error_message_;
 
   DISALLOW_ALLOCATION();
   DISALLOW_IMPLICIT_CONSTRUCTORS(ProcessStarter);
 };
 
-int Process::Start(const char* path,
+int Process::Start(Namespace* namespc,
+                   const char* path,
                    char* arguments[],
                    intptr_t arguments_length,
                    const char* working_directory,
                    char* environment[],
                    intptr_t environment_length,
                    ProcessStartMode mode,
                    intptr_t* in,
                    intptr_t* out,
                    intptr_t* err,
                    intptr_t* id,
                    intptr_t* exit_event,
                    char** os_error_message) {
-  ProcessStarter starter(path, arguments, arguments_length, working_directory,
-                         environment, environment_length, mode, in, out, err,
-                         id, exit_event, os_error_message);
+  ProcessStarter starter(namespc, path, arguments, arguments_length,
+                         working_directory, environment, environment_length,
+                         mode, in, out, err, id, exit_event, os_error_message);
   return starter.Start();
 }
 
 static bool CloseProcessBuffers(struct pollfd fds[3]) {
   int e = errno;
   VOID_TEMP_FAILURE_RETRY(close(fds[0].fd));
   VOID_TEMP_FAILURE_RETRY(close(fds[1].fd));
   VOID_TEMP_FAILURE_RETRY(close(fds[2].fd));
   errno = e;
   return false;
@@ skipping 235 matching lines @@
     bzero(&act, sizeof(act));
     act.sa_handler = SIG_DFL;
     sigaction(signal, &act, NULL);
   }
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(HOST_OS_LINUX)