/**
* ot_gfile_atomic_symlink_swap:
* @path: Replace the contents of this symbolic link
* @target: New symbolic link target
* @cancellable:
* @error
*
* Create a new temporary symbolic link, then use the Unix rename()
* function to atomically replace @path with the new symbolic link.
* Do not use this function inside directories such as /tmp as it uses
* a predicatable file name.
*/
gboolean
ot_gfile_atomic_symlink_swap (GFile *path,
const char *target,
GCancellable *cancellable,
GError **error)
{
gboolean ret = FALSE;
g_autoptr(GFile) parent = g_file_get_parent (path);
g_autofree char *tmpname = g_strconcat (gs_file_get_basename_cached (path), ".tmp", NULL);
g_autoptr(GFile) tmppath = g_file_get_child (parent, tmpname);
int parent_dfd = -1;
if (!ot_gfile_ensure_unlinked (tmppath, cancellable, error))
goto out;
if (!g_file_make_symbolic_link (tmppath, target, cancellable, error))
goto out;
if (!gs_file_open_dir_fd (parent, &parent_dfd, cancellable, error))
goto out;
/* Ensure the link has hit disk */
if (fsync (parent_dfd) != 0)
{
gs_set_error_from_errno (error, errno);
goto out;
}
if (!gs_file_rename (tmppath, path, cancellable, error))
goto out;
/* And sync again for good measure */
if (fsync (parent_dfd) != 0)
{
gs_set_error_from_errno (error, errno);
goto out;
}
ret = TRUE;
out:
if (parent_dfd != -1) (void) close (parent_dfd);
return ret;
}
static gboolean
_ostree_bootloader_grub2_write_config (OstreeBootloader *bootloader,
int bootversion,
GCancellable *cancellable,
GError **error)
{
OstreeBootloaderGrub2 *self = OSTREE_BOOTLOADER_GRUB2 (bootloader);
gboolean ret = FALSE;
gs_unref_object GFile *efi_new_config_temp = NULL;
gs_unref_object GFile *efi_orig_config = NULL;
gs_unref_object GFile *new_config_path = NULL;
gs_unref_object GSSubprocessContext *procctx = NULL;
gs_unref_object GSSubprocess *proc = NULL;
gs_strfreev char **child_env = g_get_environ ();
gs_free char *bootversion_str = g_strdup_printf ("%u", (guint)bootversion);
gs_unref_object GFile *config_path_efi_dir = NULL;
if (self->is_efi)
{
config_path_efi_dir = g_file_get_parent (self->config_path_efi);
new_config_path = g_file_get_child (config_path_efi_dir, "grub.cfg.new");
/* We use grub2-mkconfig to write to a temporary file first */
if (!ot_gfile_ensure_unlinked (new_config_path, cancellable, error))
goto out;
}
else
{
new_config_path = ot_gfile_resolve_path_printf (self->sysroot->path, "boot/loader.%d/grub.cfg",
bootversion);
}
procctx = gs_subprocess_context_newv ("grub2-mkconfig", "-o",
gs_file_get_path_cached (new_config_path),
NULL);
child_env = g_environ_setenv (child_env, "_OSTREE_GRUB2_BOOTVERSION", bootversion_str, TRUE);
/* We have to pass our state to the child */
if (self->is_efi)
child_env = g_environ_setenv (child_env, "_OSTREE_GRUB2_IS_EFI", "1", TRUE);
gs_subprocess_context_set_environment (procctx, child_env);
gs_subprocess_context_set_stdout_disposition (procctx, GS_SUBPROCESS_STREAM_DISPOSITION_NULL);
if (g_getenv ("OSTREE_DEBUG_GRUB2"))
gs_subprocess_context_set_stderr_disposition (procctx, GS_SUBPROCESS_STREAM_DISPOSITION_INHERIT);
else
gs_subprocess_context_set_stderr_disposition (procctx, GS_SUBPROCESS_STREAM_DISPOSITION_NULL);
/* In the current Fedora grub2 package, this script doesn't even try
to be atomic; it just does:
cat ${grub_cfg}.new > ${grub_cfg}
rm -f ${grub_cfg}.new
Upstream is fixed though.
*/
proc = gs_subprocess_new (procctx, cancellable, error);
if (!proc)
goto out;
if (!gs_subprocess_wait_sync_check (proc, cancellable, error))
goto out;
/* Now let's fdatasync() for the new file */
if (!gs_file_sync_data (new_config_path, cancellable, error))
goto out;
if (self->is_efi)
{
gs_unref_object GFile *config_path_efi_old = g_file_get_child (config_path_efi_dir, "grub.cfg.old");
/* copy current to old */
if (!ot_gfile_ensure_unlinked (config_path_efi_old, cancellable, error))
goto out;
if (!g_file_copy (self->config_path_efi, config_path_efi_old,
G_FILE_COPY_OVERWRITE, cancellable, NULL, NULL, error))
goto out;
if (!ot_gfile_ensure_unlinked (config_path_efi_old, cancellable, error))
goto out;
/* NOTE: NON-ATOMIC REPLACEMENT; WE can't do anything else on FAT;
* see https://bugzilla.gnome.org/show_bug.cgi?id=724246
*/
if (!ot_gfile_ensure_unlinked (self->config_path_efi, cancellable, error))
goto out;
if (!gs_file_rename (new_config_path, self->config_path_efi,
cancellable, error))
goto out;
}
ret = TRUE;
out:
return ret;
}
