[dart:io] Namespaces for file IO

runtime/bin/file_android.cc

Index: runtime/bin/file_android.cc
diff --git a/runtime/bin/file_android.cc b/runtime/bin/file_android.cc
index 139ac7ff6fe281d4728f528cc0a60e10059653e7..36a27cfed58e9b19df29bd8b4adeb76df8d6ddc1 100644
--- a/runtime/bin/file_android.cc
+++ b/runtime/bin/file_android.cc
@@ -13,6 +13,7 @@
 #include <sys/mman.h>      // NOLINT
 #include <sys/sendfile.h>  // NOLINT
 #include <sys/stat.h>      // NOLINT
+#include <sys/syscall.h>   // NOLINT
 #include <sys/types.h>     // NOLINT
 #include <unistd.h>        // NOLINT
 #include <utime.h>         // NOLINT
@@ -20,6 +21,7 @@
 #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"
 
@@ -40,7 +42,8 @@ class FileHandle {
 };
 
 File::~File() {
-  if (!IsClosed()) {
+  if (!IsClosed() && (handle_->fd() != STDOUT_FILENO) &&
+      (handle_->fd() != STDERR_FILENO)) {
     Close();
   }
   delete handle_;
@@ -58,9 +61,8 @@ void File::Close() {
     int err = TEMP_FAILURE_RETRY(close(handle_->fd()));
     if (err != 0) {
       const int kBufferSize = 1024;
-      char error_message[kBufferSize];
-      Utils::StrError(errno, error_message, kBufferSize);
-      Log::PrintErr("%s\n", error_message);
+      char error_buf[kBufferSize];
+      Log::PrintErr("%s\n", Utils::StrError(errno, error_buf, kBufferSize));
     }
   }
   handle_->set_fd(kClosedFd);
@@ -196,11 +198,13 @@ File* File::FileOpenW(const wchar_t* system_name, FileOpenMode mode) {
   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 stat st;
-  if (NO_RETRY_EXPECTED(stat(name, &st)) == 0) {
-    if (!S_ISREG(st.st_mode)) {
+  if (TEMP_FAILURE_RETRY(fstatat(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;
     }
@@ -218,13 +222,13 @@ File* File::Open(const char* name, FileOpenMode mode) {
     flags = flags | O_TRUNC;
   }
   flags |= O_CLOEXEC;
-  int fd = TEMP_FAILURE_RETRY(open(name, flags, 0666));
+  const int fd = TEMP_FAILURE_RETRY(openat(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 = lseek64(fd, 0, SEEK_END);
+    int64_t position = NO_RETRY_EXPECTED(lseek(fd, 0, SEEK_END));
     if (position < 0) {
       return NULL;
     }
@@ -236,9 +240,10 @@ 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 stat st;
-  if (NO_RETRY_EXPECTED(stat(name, &st)) == 0) {
+  if (TEMP_FAILURE_RETRY(fstatat(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 {
@@ -246,8 +251,10 @@ bool File::Exists(const char* name) {
   }
 }
 
-bool File::Create(const char* name) {
-  int fd = TEMP_FAILURE_RETRY(open(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(
+      openat(ns.fd(), ns.path(), O_RDONLY | O_CREAT | O_CLOEXEC, 0666));
   if (fd < 0) {
     return false;
   }
@@ -256,7 +263,7 @@ bool File::Create(const char* name) {
   // an entity at the same path that is a directory or a link.
   bool is_file = true;
   struct stat st;
-  if (NO_RETRY_EXPECTED(fstat(fd, &st)) == 0) {
+  if (TEMP_FAILURE_RETRY(fstat(fd, &st)) == 0) {
     if (S_ISDIR(st.st_mode)) {
       errno = EISDIR;
       is_file = false;
@@ -269,18 +276,30 @@ bool File::Create(const char* name) {
   return is_file;
 }
 
-bool File::CreateLink(const char* name, const char* target) {
-  int status = NO_RETRY_EXPECTED(symlink(target, name));
-  return (status == 0);
+// symlinkat is added to Android libc in android-21.
+static int SymlinkAt(const char* oldpath, int newdirfd, const char* newpath) {
+  return syscall(__NR_symlinkat, oldpath, newdirfd, newpath);
 }
 
-File::Type File::GetType(const char* pathname, bool follow_links) {
+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(Namespace* namespc,
+                         const char* name,
+                         bool follow_links) {
+  NamespaceScope ns(namespc, name);
   struct stat entry_info;
   int stat_success;
   if (follow_links) {
-    stat_success = NO_RETRY_EXPECTED(stat(pathname, &entry_info));
+    stat_success =
+        TEMP_FAILURE_RETRY(fstatat(ns.fd(), ns.path(), &entry_info, 0));
   } else {
-    stat_success = NO_RETRY_EXPECTED(lstat(pathname, &entry_info));
+    stat_success = TEMP_FAILURE_RETRY(
+        fstatat(ns.fd(), ns.path(), &entry_info, AT_SYMLINK_NOFOLLOW));
   }
   if (stat_success == -1) {
     return File::kDoesNotExist;
@@ -297,10 +316,11 @@ File::Type File::GetType(const char* pathname, bool follow_links) {
   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;
   }
@@ -318,46 +338,64 @@ static bool CheckTypeAndSetErrno(const char* name,
   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 stat st;
-  if (NO_RETRY_EXPECTED(stat(old_path, &st)) != 0) {
+  if (TEMP_FAILURE_RETRY(fstatat(oldns.fd(), oldns.path(), &st, 0)) != 0) {
     return false;
   }
-  int old_fd = TEMP_FAILURE_RETRY(open(old_path, O_RDONLY | O_CLOEXEC));
+  const int old_fd = TEMP_FAILURE_RETRY(
+      openat(oldns.fd(), oldns.path(), O_RDONLY | O_CLOEXEC));
   if (old_fd < 0) {
     return false;
   }
-  int new_fd = TEMP_FAILURE_RETRY(
-      open(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(
+      openat(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;
   }
   off_t offset = 0;
-  int result = 1;
+  intptr_t result = 1;
   while (result > 0) {
     // Loop to ensure we copy everything, and not only up to 2GB.
     result = NO_RETRY_EXPECTED(sendfile(new_fd, old_fd, &offset, kMaxUint32));
@@ -381,15 +419,16 @@ bool File::Copy(const char* old_path, const char* new_path) {
   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 stat* st) {
-  if (NO_RETRY_EXPECTED(stat(name, st)) != 0) {
+static bool StatHelper(Namespace* namespc, const char* name, struct stat* st) {
+  NamespaceScope ns(namespc, name);
+  if (TEMP_FAILURE_RETRY(fstatat(ns.fd(), ns.path(), st, 0)) != 0) {
     return false;
   }
   // Signal an error if it's a directory.
@@ -401,17 +440,24 @@ static bool StatHelper(const char* name, struct stat* st) {
   return true;
 }
 
-int64_t File::LengthFromPath(const char* name) {
+int64_t File::LengthFromPath(Namespace* namespc, const char* name) {
   struct stat st;
-  if (!StatHelper(name, &st)) {
+  if (!StatHelper(namespc, name, &st)) {
     return -1;
   }
   return st.st_size;
 }
 
-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 stat st;
-  if (NO_RETRY_EXPECTED(stat(name, &st)) == 0) {
+  if (TEMP_FAILURE_RETRY(fstatat(ns.fd(), ns.path(), &st, 0)) == 0) {
     if (S_ISREG(st.st_mode)) {
       data[kType] = kIsFile;
     } else if (S_ISDIR(st.st_mode)) {
@@ -431,66 +477,89 @@ void File::Stat(const char* name, int64_t* data) {
   }
 }
 
-time_t File::LastModified(const char* name) {
+time_t File::LastModified(Namespace* namespc, const char* name) {
   struct stat 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 stat 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 stat st;
-  if (!StatHelper(name, &st)) {
+  struct stat64 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]);
+  MillisecondsToTimespec(static_cast<int64_t>(st.st_mtime) * 1000, &times[1]);
+  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 stat st;
-  if (!StatHelper(name, &st)) {
+  struct stat64 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];
+  MillisecondsToTimespec(static_cast<int64_t>(st.st_atime) * 1000, &times[0]);
+  MillisecondsToTimespec(millis, &times[1]);
+  return utimensat(ns.fd(), ns.path(), times, 0) == 0;
+}
+
+// readlinkat is added to Android libc in android-21.
+static int ReadLinkAt(int dirfd,
+                      const char* pathname,
+                      char* buf,
+                      size_t bufsize) {
+  return syscall(__NR_readlinkat, dirfd, pathname, buf, bufsize);
 }
 
-const char* File::LinkTarget(const char* pathname) {
+const char* File::LinkTarget(Namespace* namespc, const char* name) {
+  NamespaceScope ns(namespc, name);
   struct stat link_stats;
-  if (lstat(pathname, &link_stats) != 0) {
+  const int status = TEMP_FAILURE_RETRY(
+      fstatat(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;
   }
-  size_t target_size = link_stats.st_size;
-  char* target_name = DartUtils::ScopedCString(target_size + 1);
-  ASSERT(target_name != NULL);
-  size_t read_size = readlink(pathname, target_name, target_size + 1);
-  if (read_size != target_size) {
+  // 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];
+  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;
 }
@@ -499,17 +568,52 @@ bool File::IsAbsolutePath(const char* pathname) {
   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 stat link_stats;
+  if (TEMP_FAILURE_RETRY(lstat(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;
 }
 
@@ -543,11 +647,21 @@ File::StdioHandleType File::GetStdioHandleType(int fd) {
   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 stat file_1_info;
   struct stat file_2_info;
-  if ((NO_RETRY_EXPECTED(lstat(file_1, &file_1_info)) == -1) ||
-      (NO_RETRY_EXPECTED(lstat(file_2, &file_2_info)) == -1)) {
+  int status = TEMP_FAILURE_RETRY(
+      fstatat(ns1.fd(), ns1.path(), &file_1_info, AT_SYMLINK_NOFOLLOW));
+  if (status == -1) {
+    return File::kError;
+  }
+  status = TEMP_FAILURE_RETRY(
+      fstatat(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) &&