[dart:io] Namespaces for file IO

runtime/bin/file_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/file.h"
 
 #include <errno.h>         // NOLINT
 #include <fcntl.h>         // NOLINT
 #include <libgen.h>        // NOLINT
 #include <sys/mman.h>      // NOLINT
 #include <sys/sendfile.h>  // NOLINT
 #include <sys/stat.h>      // NOLINT
 #include <sys/types.h>     // NOLINT
 #include <unistd.h>        // NOLINT
 #include <utime.h>         // NOLINT
 
 #include "bin/builtin.h"
 #include "bin/fdutils.h"
 #include "bin/log.h"
+#include "bin/namespace.h"
 #include "platform/signal_blocker.h"
 #include "platform/utils.h"
 
 namespace dart {
 namespace bin {
 
 class FileHandle {
  public:
   explicit FileHandle(int fd) : fd_(fd) {}
   ~FileHandle() {}
   int fd() const { return fd_; }
   void set_fd(int fd) { fd_ = fd; }
 
  private:
   int fd_;
 
   DISALLOW_COPY_AND_ASSIGN(FileHandle);
 };
 
 File::~File() {
-  if (!IsClosed() && handle_->fd() != STDOUT_FILENO &&
-      handle_->fd() != STDERR_FILENO) {
+  if (!IsClosed() && (handle_->fd() != STDOUT_FILENO) &&
+      (handle_->fd() != STDERR_FILENO)) {
     Close();
   }
   delete handle_;
 }
 
 void File::Close() {
   ASSERT(handle_->fd() >= 0);
   if (handle_->fd() == STDOUT_FILENO) {
     // If stdout, redirect fd to /dev/null.
     int null_fd = TEMP_FAILURE_RETRY(open("/dev/null", O_WRONLY));
@@ skipping 134 matching lines @@
     return st.st_size;
   }
   return -1;
 }
 
 File* File::FileOpenW(const wchar_t* system_name, FileOpenMode mode) {
   UNREACHABLE();
   return NULL;
 }
 
-File* File::Open(const char* name, FileOpenMode mode) {
+File* File::Open(Namespace* namespc, const char* name, FileOpenMode mode) {
+  NamespaceScope ns(namespc, name);
   // Report errors for non-regular files.
   struct stat64 st;
-  if (TEMP_FAILURE_RETRY(stat64(name, &st)) == 0) {
+  if (TEMP_FAILURE_RETRY(fstatat64(ns.fd(), ns.path(), &st, 0)) == 0) {
     // Only accept regular files, character devices, and pipes.
     if (!S_ISREG(st.st_mode) && !S_ISCHR(st.st_mode) && !S_ISFIFO(st.st_mode)) {
       errno = (S_ISDIR(st.st_mode)) ? EISDIR : ENOENT;
       return NULL;
     }
   }
   int flags = O_RDONLY;
   if ((mode & kWrite) != 0) {
     ASSERT((mode & kWriteOnly) == 0);
     flags = (O_RDWR | O_CREAT);
   }
   if ((mode & kWriteOnly) != 0) {
     ASSERT((mode & kWrite) == 0);
     flags = (O_WRONLY | O_CREAT);
   }
   if ((mode & kTruncate) != 0) {
     flags = flags | O_TRUNC;
   }
   flags |= O_CLOEXEC;
-  int fd = TEMP_FAILURE_RETRY(open64(name, flags, 0666));
+  const int fd = TEMP_FAILURE_RETRY(openat64(ns.fd(), ns.path(), flags, 0666));
   if (fd < 0) {
     return NULL;
   }
   if ((((mode & kWrite) != 0) && ((mode & kTruncate) == 0)) ||
       (((mode & kWriteOnly) != 0) && ((mode & kTruncate) == 0))) {
     int64_t position = NO_RETRY_EXPECTED(lseek64(fd, 0, SEEK_END));
     if (position < 0) {
       return NULL;
     }
   }
   return new File(new FileHandle(fd));
 }
 
 File* File::OpenStdio(int fd) {
   return ((fd < 0) || (2 < fd)) ? NULL : new File(new FileHandle(fd));
 }
 
-bool File::Exists(const char* name) {
+bool File::Exists(Namespace* namespc, const char* name) {
+  NamespaceScope ns(namespc, name);
   struct stat64 st;
-  if (TEMP_FAILURE_RETRY(stat64(name, &st)) == 0) {
+  if (TEMP_FAILURE_RETRY(fstatat64(ns.fd(), ns.path(), &st, 0)) == 0) {
     // Everything but a directory and a link is a file to Dart.
     return !S_ISDIR(st.st_mode) && !S_ISLNK(st.st_mode);
   } else {
     return false;
   }
 }
 
-bool File::Create(const char* name) {
-  int fd =
-      TEMP_FAILURE_RETRY(open64(name, O_RDONLY | O_CREAT | O_CLOEXEC, 0666));
+bool File::Create(Namespace* namespc, const char* name) {
+  NamespaceScope ns(namespc, name);
+  const int fd = TEMP_FAILURE_RETRY(
+      openat64(ns.fd(), ns.path(), O_RDONLY | O_CREAT | O_CLOEXEC, 0666));
   if (fd < 0) {
     return false;
   }
   // File.create returns a File, so we shouldn't be giving the illusion that the
   // call has created a file or that a file already exists if there is already
   // an entity at the same path that is a directory or a link.
   bool is_file = true;
   struct stat64 st;
   if (TEMP_FAILURE_RETRY(fstat64(fd, &st)) == 0) {
     if (S_ISDIR(st.st_mode)) {
       errno = EISDIR;
       is_file = false;
     } else if (S_ISLNK(st.st_mode)) {
       errno = ENOENT;
       is_file = false;
     }
   }
   FDUtils::SaveErrorAndClose(fd);
   return is_file;
 }
 
-bool File::CreateLink(const char* name, const char* target) {
-  return NO_RETRY_EXPECTED(symlink(target, name)) == 0;
+bool File::CreateLink(Namespace* namespc,
+                      const char* name,
+                      const char* target) {
+  NamespaceScope ns(namespc, name);
+  return NO_RETRY_EXPECTED(symlinkat(target, ns.fd(), ns.path())) == 0;
 }
 
-File::Type File::GetType(const char* pathname, bool follow_links) {
+File::Type File::GetType(Namespace* namespc,
+                         const char* name,
+                         bool follow_links) {
+  NamespaceScope ns(namespc, name);
   struct stat64 entry_info;
   int stat_success;
   if (follow_links) {
-    stat_success = TEMP_FAILURE_RETRY(stat64(pathname, &entry_info));
+    stat_success =
+        TEMP_FAILURE_RETRY(fstatat64(ns.fd(), ns.path(), &entry_info, 0));
   } else {
-    stat_success = TEMP_FAILURE_RETRY(lstat64(pathname, &entry_info));
+    stat_success = TEMP_FAILURE_RETRY(
+        fstatat64(ns.fd(), ns.path(), &entry_info, AT_SYMLINK_NOFOLLOW));
   }
   if (stat_success == -1) {
     return File::kDoesNotExist;
   }
   if (S_ISDIR(entry_info.st_mode)) {
     return File::kIsDirectory;
   }
   if (S_ISREG(entry_info.st_mode)) {
     return File::kIsFile;
   }
   if (S_ISLNK(entry_info.st_mode)) {
     return File::kIsLink;
   }
   return File::kDoesNotExist;
 }
 
-static bool CheckTypeAndSetErrno(const char* name,
+static bool CheckTypeAndSetErrno(Namespace* namespc,
+                                 const char* name,
                                  File::Type expected,
                                  bool follow_links) {
-  File::Type actual = File::GetType(name, follow_links);
+  File::Type actual = File::GetType(namespc, name, follow_links);
   if (actual == expected) {
     return true;
   }
   switch (actual) {
     case File::kIsDirectory:
       errno = EISDIR;
       break;
     case File::kDoesNotExist:
       errno = ENOENT;
       break;
     default:
       errno = EINVAL;
       break;
   }
   return false;
 }
 
-bool File::Delete(const char* name) {
-  return CheckTypeAndSetErrno(name, kIsFile, true) &&
-         (NO_RETRY_EXPECTED(unlink(name)) == 0);
+bool File::Delete(Namespace* namespc, const char* name) {
+  NamespaceScope ns(namespc, name);
+  return CheckTypeAndSetErrno(namespc, name, kIsFile, true) &&
+         (NO_RETRY_EXPECTED(unlinkat(ns.fd(), ns.path(), 0)) == 0);
 }
 
-bool File::DeleteLink(const char* name) {
-  return CheckTypeAndSetErrno(name, kIsLink, false) &&
-         (NO_RETRY_EXPECTED(unlink(name)) == 0);
+bool File::DeleteLink(Namespace* namespc, const char* name) {
+  NamespaceScope ns(namespc, name);
+  return CheckTypeAndSetErrno(namespc, name, kIsLink, false) &&
+         (NO_RETRY_EXPECTED(unlinkat(ns.fd(), ns.path(), 0)) == 0);
 }
 
-bool File::Rename(const char* old_path, const char* new_path) {
-  return CheckTypeAndSetErrno(old_path, kIsFile, true) &&
-         (NO_RETRY_EXPECTED(rename(old_path, new_path)) == 0);
+bool File::Rename(Namespace* namespc,
+                  const char* old_path,
+                  const char* new_path) {
+  NamespaceScope oldns(namespc, old_path);
+  NamespaceScope newns(namespc, new_path);
+  return CheckTypeAndSetErrno(namespc, old_path, kIsFile, true) &&
+         (NO_RETRY_EXPECTED(renameat(oldns.fd(), oldns.path(), newns.fd(),
+                                     newns.path())) == 0);
 }
 
-bool File::RenameLink(const char* old_path, const char* new_path) {
-  return CheckTypeAndSetErrno(old_path, kIsLink, false) &&
-         (NO_RETRY_EXPECTED(rename(old_path, new_path)) == 0);
+bool File::RenameLink(Namespace* namespc,
+                      const char* old_path,
+                      const char* new_path) {
+  NamespaceScope oldns(namespc, old_path);
+  NamespaceScope newns(namespc, new_path);
+  return CheckTypeAndSetErrno(namespc, old_path, kIsLink, false) &&
+         (NO_RETRY_EXPECTED(renameat(oldns.fd(), oldns.path(), newns.fd(),
+                                     newns.path())) == 0);
 }
 
-bool File::Copy(const char* old_path, const char* new_path) {
-  if (!CheckTypeAndSetErrno(old_path, kIsFile, true)) {
+bool File::Copy(Namespace* namespc,
+                const char* old_path,
+                const char* new_path) {
+  if (!CheckTypeAndSetErrno(namespc, old_path, kIsFile, true)) {
     return false;
   }
+  NamespaceScope oldns(namespc, old_path);
   struct stat64 st;
-  if (TEMP_FAILURE_RETRY(stat64(old_path, &st)) != 0) {
+  if (TEMP_FAILURE_RETRY(fstatat64(oldns.fd(), oldns.path(), &st, 0)) != 0) {
     return false;
   }
-  int old_fd = TEMP_FAILURE_RETRY(open64(old_path, O_RDONLY | O_CLOEXEC));
+  const int old_fd = TEMP_FAILURE_RETRY(
+      openat64(oldns.fd(), oldns.path(), O_RDONLY | O_CLOEXEC));
   if (old_fd < 0) {
     return false;
   }
-  int new_fd = TEMP_FAILURE_RETRY(
-      open64(new_path, O_WRONLY | O_TRUNC | O_CREAT | O_CLOEXEC, st.st_mode));
+  NamespaceScope newns(namespc, new_path);
+  const int new_fd = TEMP_FAILURE_RETRY(
+      openat64(newns.fd(), newns.path(),
+               O_WRONLY | O_TRUNC | O_CREAT | O_CLOEXEC, st.st_mode));
   if (new_fd < 0) {
     VOID_TEMP_FAILURE_RETRY(close(old_fd));
     return false;
   }
   int64_t offset = 0;
   intptr_t result = 1;
   while (result > 0) {
     // Loop to ensure we copy everything, and not only up to 2GB.
     result = NO_RETRY_EXPECTED(sendfile64(new_fd, old_fd, &offset, kMaxUint32));
   }
   // From sendfile man pages:
   //   Applications may wish to fall back to read(2)/write(2) in the case
   //   where sendfile() fails with EINVAL or ENOSYS.
   if ((result < 0) && ((errno == EINVAL) || (errno == ENOSYS))) {
     const intptr_t kBufferSize = 8 * KB;
     uint8_t buffer[kBufferSize];
     while ((result = TEMP_FAILURE_RETRY(read(old_fd, buffer, kBufferSize))) >
            0) {
       int wrote = TEMP_FAILURE_RETRY(write(new_fd, buffer, result));
       if (wrote != result) {
         result = -1;
         break;
       }
     }
   }
   int e = errno;
   VOID_TEMP_FAILURE_RETRY(close(old_fd));
   VOID_TEMP_FAILURE_RETRY(close(new_fd));
   if (result < 0) {
-    VOID_NO_RETRY_EXPECTED(unlink(new_path));
+    VOID_NO_RETRY_EXPECTED(unlinkat(newns.fd(), newns.path(), 0));
     errno = e;
     return false;
   }
   return true;
 }
 
-static bool StatHelper(const char* name, struct stat64* st) {
-  if (TEMP_FAILURE_RETRY(stat64(name, st)) != 0) {
+static bool StatHelper(Namespace* namespc,
+                       const char* name,
+                       struct stat64* st) {
+  NamespaceScope ns(namespc, name);
+  if (TEMP_FAILURE_RETRY(fstatat64(ns.fd(), ns.path(), st, 0)) != 0) {
     return false;
   }
   // Signal an error if it's a directory.
   if (S_ISDIR(st->st_mode)) {
     errno = EISDIR;
     return false;
   }
   // Otherwise assume the caller knows what it's doing.
   return true;
 }
 
-int64_t File::LengthFromPath(const char* name) {
+int64_t File::LengthFromPath(Namespace* namespc, const char* name) {
   struct stat64 st;
-  if (!StatHelper(name, &st)) {
+  if (!StatHelper(namespc, name, &st)) {
     return -1;
   }
   return st.st_size;
 }
 
 static int64_t TimespecToMilliseconds(const struct timespec& t) {
   return static_cast<int64_t>(t.tv_sec) * 1000L +
          static_cast<int64_t>(t.tv_nsec) / 1000000L;
 }
 
-void File::Stat(const char* name, int64_t* data) {
+static void MillisecondsToTimespec(int64_t millis, struct timespec* t) {
+  ASSERT(t != NULL);
+  t->tv_sec = millis / kMillisecondsPerSecond;
+  t->tv_nsec = (millis - (t->tv_sec * kMillisecondsPerSecond)) * 1000L;
+}
+
+void File::Stat(Namespace* namespc, const char* name, int64_t* data) {
+  NamespaceScope ns(namespc, name);
   struct stat64 st;
-  if (TEMP_FAILURE_RETRY(stat64(name, &st)) == 0) {
+  if (TEMP_FAILURE_RETRY(fstatat64(ns.fd(), ns.path(), &st, 0)) == 0) {
     if (S_ISREG(st.st_mode)) {
       data[kType] = kIsFile;
     } else if (S_ISDIR(st.st_mode)) {
       data[kType] = kIsDirectory;
     } else if (S_ISLNK(st.st_mode)) {
       data[kType] = kIsLink;
     } else {
       data[kType] = kDoesNotExist;
     }
     data[kCreatedTime] = TimespecToMilliseconds(st.st_ctim);
     data[kModifiedTime] = TimespecToMilliseconds(st.st_mtim);
     data[kAccessedTime] = TimespecToMilliseconds(st.st_atim);
     data[kMode] = st.st_mode;
     data[kSize] = st.st_size;
   } else {
     data[kType] = kDoesNotExist;
   }
 }
 
-time_t File::LastModified(const char* name) {
+time_t File::LastModified(Namespace* namespc, const char* name) {
   struct stat64 st;
-  if (!StatHelper(name, &st)) {
+  if (!StatHelper(namespc, name, &st)) {
     return -1;
   }
   return st.st_mtime;
 }
 
-time_t File::LastAccessed(const char* name) {
+time_t File::LastAccessed(Namespace* namespc, const char* name) {
   struct stat64 st;
-  if (!StatHelper(name, &st)) {
+  if (!StatHelper(namespc, name, &st)) {
     return -1;
   }
   return st.st_atime;
 }
 
-bool File::SetLastAccessed(const char* name, int64_t millis) {
+bool File::SetLastAccessed(Namespace* namespc,
+                           const char* name,
+                           int64_t millis) {
   // First get the current times.
   struct stat64 st;
-  if (!StatHelper(name, &st)) {
+  if (!StatHelper(namespc, name, &st)) {
     return false;
   }
 
   // Set the new time:
-  struct utimbuf times;
-  times.actime = millis / kMillisecondsPerSecond;
-  times.modtime = st.st_mtime;
-  return utime(name, &times) == 0;
+  NamespaceScope ns(namespc, name);
+  struct timespec times[2];
+  MillisecondsToTimespec(millis, &times[0]);
+  times[1] = st.st_mtim;
+  return utimensat(ns.fd(), ns.path(), times, 0) == 0;
 }
 
-bool File::SetLastModified(const char* name, int64_t millis) {
+bool File::SetLastModified(Namespace* namespc,
+                           const char* name,
+                           int64_t millis) {
   // First get the current times.
   struct stat64 st;
-  if (!StatHelper(name, &st)) {
+  if (!StatHelper(namespc, name, &st)) {
     return false;
   }
 
   // Set the new time:
-  struct utimbuf times;
-  times.actime = st.st_atime;
-  times.modtime = millis / kMillisecondsPerSecond;
-  return utime(name, &times) == 0;
+  NamespaceScope ns(namespc, name);
+  struct timespec times[2];
+  times[0] = st.st_atim;
+  MillisecondsToTimespec(millis, &times[1]);
+  return utimensat(ns.fd(), ns.path(), times, 0) == 0;
 }
 
-const char* File::LinkTarget(const char* pathname) {
+const char* File::LinkTarget(Namespace* namespc, const char* name) {
+  NamespaceScope ns(namespc, name);
   struct stat64 link_stats;
-  if (TEMP_FAILURE_RETRY(lstat64(pathname, &link_stats)) != 0) {
+  const int status = TEMP_FAILURE_RETRY(
+      fstatat64(ns.fd(), ns.path(), &link_stats, AT_SYMLINK_NOFOLLOW));
+  if (status != 0) {
     return NULL;
   }
   if (!S_ISLNK(link_stats.st_mode)) {
     errno = ENOENT;
     return NULL;
   }
   // Don't rely on the link_stats.st_size for the size of the link
   // target. For some filesystems, e.g. procfs, this value is always
   // 0. Also the link might have changed before the readlink call.
   const int kBufferSize = PATH_MAX + 1;
   char target[kBufferSize];
-  size_t target_size =
-      TEMP_FAILURE_RETRY(readlink(pathname, target, kBufferSize));
+  const int target_size =
+      TEMP_FAILURE_RETRY(readlinkat(ns.fd(), ns.path(), target, kBufferSize));
   if (target_size <= 0) {
     return NULL;
   }
   char* target_name = DartUtils::ScopedCString(target_size + 1);
   ASSERT(target_name != NULL);
   memmove(target_name, target, target_size);
   target_name[target_size] = '\0';
   return target_name;
 }
 
 bool File::IsAbsolutePath(const char* pathname) {
-  return (pathname != NULL && pathname[0] == '/');
+  return (pathname != NULL) && (pathname[0] == '/');
 }
 
-const char* File::GetCanonicalPath(const char* pathname) {
-  char* abs_path = NULL;
-  if (pathname != NULL) {
-    char* resolved_path = DartUtils::ScopedCString(PATH_MAX + 1);
-    ASSERT(resolved_path != NULL);
-    do {
-      abs_path = realpath(pathname, resolved_path);
-    } while (abs_path == NULL && errno == EINTR);
-    ASSERT(abs_path == NULL || IsAbsolutePath(abs_path));
-    ASSERT(abs_path == NULL || (abs_path == resolved_path));
+const char* File::ReadLink(const char* pathname) {
+  ASSERT(pathname != NULL);
+  ASSERT(IsAbsolutePath(pathname));
+  struct stat64 link_stats;
+  if (TEMP_FAILURE_RETRY(lstat64(pathname, &link_stats)) != 0) {
+    return NULL;
   }
+  if (!S_ISLNK(link_stats.st_mode)) {
+    errno = ENOENT;
+    return NULL;
+  }
+  // Don't rely on the link_stats.st_size for the size of the link
+  // target. For some filesystems, e.g. procfs, this value is always
+  // 0. Also the link might have changed before the readlink call.
+  const int kBufferSize = PATH_MAX + 1;
+  char target[kBufferSize];
+  size_t target_size =
+      TEMP_FAILURE_RETRY(readlink(pathname, target, kBufferSize));
+  if (target_size <= 0) {
+    return NULL;
+  }
+  char* target_name = DartUtils::ScopedCString(target_size + 1);
+  ASSERT(target_name != NULL);
+  memmove(target_name, target, target_size);
+  target_name[target_size] = '\0';
+  return target_name;
+}
+
+const char* File::GetCanonicalPath(Namespace* namespc, const char* name) {
+  if (name == NULL) {
+    return NULL;
+  }
+  if (!Namespace::IsDefault(namespc)) {
+    // TODO(zra): There is no realpathat(). Also chasing a symlink might result
+    // in a path to something outside of the namespace, so canonicalizing paths
+    // would have to be done carefully. For now, don't do anything.
+    return name;
+  }
+  char* abs_path;
+  char* resolved_path = DartUtils::ScopedCString(PATH_MAX + 1);
+  ASSERT(resolved_path != NULL);
+  do {
+    abs_path = realpath(name, resolved_path);
+  } while ((abs_path == NULL) && (errno == EINTR));
+  ASSERT(abs_path == NULL || IsAbsolutePath(abs_path));
+  ASSERT(abs_path == NULL || (abs_path == resolved_path));
   return abs_path;
 }
 
 const char* File::PathSeparator() {
   return "/";
 }
 
 const char* File::StringEscapedPathSeparator() {
   return "/";
 }
@@ skipping 13 matching lines @@
   }
   if (S_ISSOCK(buf.st_mode)) {
     return kSocket;
   }
   if (S_ISREG(buf.st_mode)) {
     return kFile;
   }
   return kOther;
 }
 
-File::Identical File::AreIdentical(const char* file_1, const char* file_2) {
+File::Identical File::AreIdentical(Namespace* namespc,
+                                   const char* file_1,
+                                   const char* file_2) {
+  NamespaceScope ns1(namespc, file_1);
+  NamespaceScope ns2(namespc, file_2);
   struct stat64 file_1_info;
   struct stat64 file_2_info;
-  if ((TEMP_FAILURE_RETRY(lstat64(file_1, &file_1_info)) == -1) ||
-      (TEMP_FAILURE_RETRY(lstat64(file_2, &file_2_info)) == -1)) {
+  int status = TEMP_FAILURE_RETRY(
+      fstatat64(ns1.fd(), ns1.path(), &file_1_info, AT_SYMLINK_NOFOLLOW));
+  if (status == -1) {
+    return File::kError;
+  }
+  status = TEMP_FAILURE_RETRY(
+      fstatat64(ns2.fd(), ns2.path(), &file_2_info, AT_SYMLINK_NOFOLLOW));
+  if (status == -1) {
     return File::kError;
   }
   return ((file_1_info.st_ino == file_2_info.st_ino) &&
           (file_1_info.st_dev == file_2_info.st_dev))
              ? File::kIdentical
              : File::kDifferent;
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(HOST_OS_LINUX)