src/lib/storage/fs_management/cpp/mount.cc

// Copyright 2016 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <errno.h>
#include <fcntl.h>
#include <fidl/fuchsia.hardware.block/cpp/wire.h>
#include <fidl/fuchsia.io.admin/cpp/wire.h>
#include <fidl/fuchsia.io/cpp/wire.h>
#include <lib/fdio/cpp/caller.h>
#include <lib/fdio/directory.h>
#include <lib/fdio/fd.h>
#include <lib/fdio/fdio.h>
#include <lib/fdio/limits.h>
#include <lib/fdio/namespace.h>
#include <lib/fdio/vfs.h>
#include <lib/zx/channel.h>
#include <string.h>
#include <unistd.h>
#include <zircon/compiler.h>
#include <zircon/device/block.h>
#include <zircon/device/vfs.h>
#include <zircon/processargs.h>
#include <zircon/syscalls.h>

#include <utility>

#include <fbl/algorithm.h>
#include <fbl/alloc_checker.h>
#include <fbl/unique_fd.h>
#include <fbl/vector.h>
#include <fs-management/mount.h>
#include <pretty/hexdump.h>

#include "admin.h"
#include "src/lib/storage/vfs/cpp/fuchsia_vfs.h"

namespace fblock = fuchsia_hardware_block;
namespace fio = fuchsia_io;

namespace fs_management {
namespace {

zx_status_t MakeDirAndRemoteMount(const char* path, zx::channel root) {
  // Open the parent path as O_ADMIN, and sent the mkdir+mount command
  // to that directory.
  char parent_path[PATH_MAX];
  const char* name;
  strcpy(parent_path, path);
  char* last_slash = strrchr(parent_path, '/');
  if (last_slash == NULL) {
    strcpy(parent_path, ".");
    name = path;
  } else {
    *last_slash = '\0';
    name = last_slash + 1;
    if (*name == '\0') {
      return ZX_ERR_INVALID_ARGS;
    }
  }

  zx_status_t status;
  zx::channel parent, parent_server;
  if ((status = zx::channel::create(0, &parent, &parent_server)) != ZX_OK) {
    return status;
  }
  uint32_t flags = fio::wire::kOpenRightReadable | fio::wire::kOpenRightWritable |
                   fio::wire::kOpenFlagDirectory | fio::wire::kOpenRightAdmin;
  if ((status = fdio_open(parent_path, flags, parent_server.release())) != ZX_OK) {
    return status;
  }
  fidl::WireSyncClient<fuchsia_io_admin::DirectoryAdmin> parent_client(std::move(parent));
  auto resp =
      parent_client->MountAndCreate(std::move(root), fidl::StringView::FromExternal(name), 0);
  if (!resp.ok()) {
    return resp.status();
  }
  return resp.value().s;
}

zx_status_t StartFilesystem(fbl::unique_fd device_fd, disk_format_t df, const MountOptions& options,
                            LaunchCallback cb, OutgoingDirectory outgoing_directory,
                            zx::channel* out_data_root, zx::channel crypt_client) {
  // get the device handle from the device_fd
  zx_status_t status;
  zx::channel device;
  status = fdio_get_service_handle(device_fd.release(), device.reset_and_get_address());
  if (status != ZX_OK) {
    return status;
  }

  // convert mount options to init options
  InitOptions init_options = {
      .readonly = options.readonly,
      .verbose_mount = options.verbose_mount,
      .collect_metrics = options.collect_metrics,
      .wait_until_ready = options.wait_until_ready,
      .write_compression_algorithm = options.write_compression_algorithm,
      // TODO(jfsulliv): This is currently only used in tests. Plumb through mount options if
      // needed.
      .write_compression_level = -1,
      .cache_eviction_policy = options.cache_eviction_policy,
      .fsck_after_every_transaction = options.fsck_after_every_transaction,
      .sandbox_decompression = options.sandbox_decompression,
      .callback = cb,
  };

  // launch the filesystem process
  zx::unowned_channel export_root(outgoing_directory.client);
  status = FsInit(std::move(device), df, init_options, std::move(outgoing_directory),
                  std::move(crypt_client))
               .status_value();
  if (status != ZX_OK) {
    return status;
  }

  // Extract the handle to the root of the filesystem from the export root. The POSIX flags will
  // cause the writable and executable rights to be inherited (if present).
  uint32_t flags = fio::wire::kOpenRightReadable | fio::wire::kOpenFlagPosixWritable |
                   fio::wire::kOpenFlagPosixExecutable;
  if (options.admin)
    flags |= fio::wire::kOpenRightAdmin;
  auto handle_or = GetFsRootHandle(zx::unowned_channel(export_root), flags);
  if (handle_or.is_error()) {
    return handle_or.status_value();
  }
  *out_data_root = std::move(handle_or).value();
  return ZX_OK;
}

}  // namespace
}  // namespace fs_management

enum DiskFormatLogVerbosity {
  Silent,
  Verbose,
};

disk_format_t detect_disk_format_impl(int fd, DiskFormatLogVerbosity verbosity) {
  if (lseek(fd, 0, SEEK_SET) != 0) {
    fprintf(stderr, "detect_disk_format: Cannot seek to start of device.\n");
    return DISK_FORMAT_UNKNOWN;
  }

  fdio_cpp::UnownedFdioCaller caller(fd);
  auto resp = fidl::WireCall<fblock::Block>(caller.channel())->GetInfo();
  if (!resp.ok() || resp.value().status != ZX_OK) {
    fprintf(stderr, "detect_disk_format: Could not acquire block device info\n");
    return DISK_FORMAT_UNKNOWN;
  }

  if (!resp.value().info->block_size) {
    fprintf(stderr, "detect_disk_format: Expected a block size of > 0\n");
    return DISK_FORMAT_UNKNOWN;
  }

  // We need to read at least two blocks, because the GPT magic is located inside the second block
  // of the disk.
  size_t header_size =
      (HEADER_SIZE > (2 * resp->info->block_size)) ? HEADER_SIZE : (2 * resp->info->block_size);
  // check if the partition is big enough to hold the header in the first place
  if (header_size > resp.value().info->block_size * resp.value().info->block_count) {
    return DISK_FORMAT_UNKNOWN;
  }

  // We expect to read HEADER_SIZE bytes, but we may need to read
  // extra to read a multiple of the underlying block size.
  const size_t buffer_size =
      fbl::round_up(header_size, static_cast<size_t>(resp.value().info->block_size));

  ZX_DEBUG_ASSERT_MSG(buffer_size > 0, "Expected buffer_size to be greater than 0\n");

  uint8_t data[buffer_size];
  if (read(fd, data, buffer_size) != static_cast<ssize_t>(buffer_size)) {
    fprintf(stderr, "detect_disk_format: Error reading block device.\n");
    return DISK_FORMAT_UNKNOWN;
  }

  if (!memcmp(data, fvm_magic, sizeof(fvm_magic))) {
    return DISK_FORMAT_FVM;
  }

  if (!memcmp(data, zxcrypt_magic, sizeof(zxcrypt_magic))) {
    return DISK_FORMAT_ZXCRYPT;
  }

  if (!memcmp(data, block_verity_magic, sizeof(block_verity_magic))) {
    return DISK_FORMAT_BLOCK_VERITY;
  }

  if (!memcmp(data + resp->info->block_size, gpt_magic, sizeof(gpt_magic))) {
    return DISK_FORMAT_GPT;
  }

  if (!memcmp(data, minfs_magic, sizeof(minfs_magic))) {
    return DISK_FORMAT_MINFS;
  }

  if (!memcmp(data, blobfs_magic, sizeof(blobfs_magic))) {
    return DISK_FORMAT_BLOBFS;
  }

  if (!memcmp(data, factoryfs_magic, sizeof(factoryfs_magic))) {
    return DISK_FORMAT_FACTORYFS;
  }

  if (!memcmp(data, vbmeta_magic, sizeof(vbmeta_magic))) {
    return DISK_FORMAT_VBMETA;
  }

  if ((data[510] == 0x55 && data[511] == 0xAA)) {
    if ((data[38] == 0x29 || data[66] == 0x29)) {
      // 0x55AA are always placed at offset 510 and 511 for FAT filesystems.
      // 0x29 is the Boot Signature, but it is placed at either offset 38 or
      // 66 (depending on FAT type).
      return DISK_FORMAT_FAT;
    }
    return DISK_FORMAT_MBR;
  }

  if (!memcmp(&data[1024], f2fs_magic, sizeof(f2fs_magic))) {
    return DISK_FORMAT_F2FS;
  }

  if (!memcmp(data, fxfs_magic, sizeof(fxfs_magic))) {
    return DISK_FORMAT_FXFS;
  }

  if (verbosity == DiskFormatLogVerbosity::Verbose) {
    // Log a hexdump of the bytes we looked at and didn't find any magic in.
    fprintf(stderr, "detect_disk_format: did not recognize format.  Looked at:\n");
    // fvm, zxcrypt, minfs, and blobfs have their magic bytes at the start
    // of the block.
    hexdump_very_ex(data, 16, 0, hexdump_stdio_printf, stderr);
    // MBR is two bytes at offset 0x1fe, but print 16 just for consistency
    hexdump_very_ex(data + 0x1f0, 16, 0x1f0, hexdump_stdio_printf, stderr);
    // GPT magic is stored one block in, so it can coexist with MBR.
    hexdump_very_ex(data + resp->info->block_size, 16, resp->info->block_size, hexdump_stdio_printf,
                    stderr);
  }

  return DISK_FORMAT_UNKNOWN;
}

__EXPORT
disk_format_t detect_disk_format(int fd) {
  return detect_disk_format_impl(fd, DiskFormatLogVerbosity::Silent);
}

__EXPORT
disk_format_t detect_disk_format_log_unknown(int fd) {
  return detect_disk_format_impl(fd, DiskFormatLogVerbosity::Verbose);
}

__EXPORT
zx_status_t fmount(int dev_fd, int mount_fd, disk_format_t df, const MountOptions& options,
                   LaunchCallback cb) {
  zx::channel crypt_client(options.crypt_client);
  if (options.bind_to_namespace) {
    return ZX_ERR_NOT_SUPPORTED;
  }

  zx_status_t status;
  zx::channel data_root;
  fbl::unique_fd device_fd(dev_fd);

  fs_management::OutgoingDirectory handles{zx::unowned_channel(options.outgoing_directory.client),
                                           zx::channel(options.outgoing_directory.server)};
  zx::channel client;
  if (!*handles.client) {
    zx_status_t status = zx::channel::create(0, &client, &handles.server);
    if (status != ZX_OK)
      return status;
    handles.client = zx::unowned_channel(client);
  }

  if ((status =
           fs_management::StartFilesystem(std::move(device_fd), df, options, cb, std::move(handles),
                                          &data_root, std::move(crypt_client))) != ZX_OK) {
    return status;
  }

  fdio_cpp::FdioCaller caller{fbl::unique_fd(mount_fd)};
  auto resp = fidl::WireCall<fuchsia_io_admin::DirectoryAdmin>(caller.channel())
                  ->Mount(std::move(data_root));
  caller.release().release();
  if (!resp.ok()) {
    return resp.status();
  }
  return resp.value().s;
}

__EXPORT
zx_status_t mount_root_handle(zx_handle_t root_handle, const char* mount_path) {
  zx_status_t status;
  zx::channel mount_point, mount_point_server;
  if ((status = zx::channel::create(0, &mount_point, &mount_point_server)) != ZX_OK) {
    return status;
  }
  if ((status = fdio_open(mount_path, O_RDONLY | O_DIRECTORY | O_ADMIN,
                          mount_point_server.release())) != ZX_OK) {
    return status;
  }
  fidl::WireSyncClient<fuchsia_io_admin::DirectoryAdmin> mount_client(std::move(mount_point));
  auto resp = mount_client->Mount(zx::channel(root_handle));
  if (!resp.ok()) {
    return resp.status();
  }
  return resp.value().s;
}

__EXPORT
zx_status_t mount(int dev_fd, const char* mount_path, disk_format_t df, const MountOptions& options,
                  LaunchCallback cb) {
  zx::channel crypt_client(options.crypt_client);
  zx_status_t status;
  zx::channel data_root;
  fbl::unique_fd device_fd(dev_fd);

  fs_management::OutgoingDirectory handles{zx::unowned_channel(options.outgoing_directory.client),
                                           zx::channel(options.outgoing_directory.server)};
  zx::channel client;
  if (!*handles.client) {
    zx_status_t status = zx::channel::create(0, &client, &handles.server);
    if (status != ZX_OK)
      return status;
    handles.client = zx::unowned_channel(client);
  }

  if ((status =
           fs_management::StartFilesystem(std::move(device_fd), df, options, cb, std::move(handles),
                                          &data_root, std::move(crypt_client))) != ZX_OK) {
    return status;
  }

  // If no mount point is provided, just return success; the caller can get whatever they want from
  // the export root.
  if (mount_path == nullptr)
    return ZX_OK;

  if (options.bind_to_namespace) {
    fdio_ns_t* ns;
    if ((status = fdio_ns_get_installed(&ns)) != ZX_OK) {
      return status;
    }
    return fdio_ns_bind(ns, mount_path, data_root.release());
  } else {
    // mount the channel in the requested location
    if (options.create_mountpoint) {
      return fs_management::MakeDirAndRemoteMount(mount_path, std::move(data_root));
    }
    return mount_root_handle(data_root.release(), mount_path);
  }
}

__EXPORT
zx_status_t fumount(int mount_fd) {
  fdio_cpp::FdioCaller caller{fbl::unique_fd(mount_fd)};
  auto resp = fidl::WireCall<fuchsia_io_admin::DirectoryAdmin>(caller.channel())->UnmountNode();
  caller.release().release();
  if (!resp.ok()) {
    return resp.status();
  }
  if (resp.value().s != ZX_OK) {
    return resp.value().s;
  }
  // Note: we are unsafely converting from a client end of the
  // |fuchsia.io/Directory| protocol into a client end of the
  // |fuchsia.io/DirectoryAdmin| protocol.
  // This method will only work if |mount_fd| is backed by a connection
  // that actually speaks the |DirectoryAdmin| protocol.
  fidl::ClientEnd<fuchsia_io_admin::DirectoryAdmin> directory_admin_client(
      std::move(resp.value().remote.channel()));
  return fs::FuchsiaVfs::UnmountHandle(std::move(directory_admin_client), zx::time::infinite());
}

__EXPORT
zx_status_t umount(const char* mount_path) {
  fprintf(stderr, "Unmounting %s\n", mount_path);
  fbl::unique_fd fd(open(mount_path, O_DIRECTORY | O_NOREMOTE | O_ADMIN));
  if (!fd) {
    fprintf(stderr, "Could not open directory: %s\n", strerror(errno));
    return ZX_ERR_BAD_STATE;
  }
  zx_status_t status = fumount(fd.get());
  return status;
}