On Thu, Jun 03, 2021 at 11:17:56AM +0900, Masami Hiramatsu wrote:
> Because UEFI specification v2.9, 13.3 File System Format said "The
> file system supported by the Extensible Firmware Interface is based
> on the FAT file system.", the simple file system protocol might be
> better to support only FAT filesystem.
If I remember correctly, Heinrich rejected the idea a long time ago.
When I posted the commit 867400677cda ("efi_loader: disk: install
FILE_SYSTEM_PROTOCOL only if available"), he insisted that the UEFI
specification does require FAT support but that it doesn't deny
any support for other file systems.
So I had to change the code, allowing FS_TYPE_ANY.
-Takahiro Akashi
> There must be no problem from UEFI application to access only FAT
> because ESP must be formatted by FAT32 and the removable media is
> FAT12 or FAT16, according to the UEFI spec.
>
> Reported-by: Kazuhiko Sakamoto <sakamoto.kazuh...@socionext.com>
> Signed-off-by: Masami Hiramatsu <masami.hirama...@linaro.org>
> ---
> lib/efi_loader/efi_disk.c | 18 ++++++++++++------
> 1 file changed, 12 insertions(+), 6 deletions(-)
>
> diff --git a/lib/efi_loader/efi_disk.c b/lib/efi_loader/efi_disk.c
> index 307d5d759b..f69ae6587f 100644
> --- a/lib/efi_loader/efi_disk.c
> +++ b/lib/efi_loader/efi_disk.c
> @@ -318,19 +318,25 @@ efi_fs_from_path(struct efi_device_path *full_path)
> }
>
> /**
> - * efi_fs_exists() - check if a partition bears a file system
> + * efi_supported_fs_exists() - check if a partition bears a supported file
> system
> *
> * @desc: block device descriptor
> * @part: partition number
> - * Return: 1 if a file system exists on the partition
> + * Return: 1 if a supported file system exists on the partition
> * 0 otherwise
> */
> -static int efi_fs_exists(struct blk_desc *desc, int part)
> +static int efi_supported_fs_exists(struct blk_desc *desc, int part)
> {
> if (fs_set_blk_dev_with_part(desc, part))
> return 0;
>
> - if (fs_get_type() == FS_TYPE_ANY)
> + /*
> + * Because UEFI specification v2.9, 13.3 File System Format said
> + * "The file system supported by the Extensible Firmware Interface
> + * is based on the FAT file system.", the simple file system protocol
> + * should support only FAT filesystem.
> + */
> + if (fs_get_type() != FS_TYPE_FAT)
> return 0;
>
> fs_close();
> @@ -428,10 +434,10 @@ static efi_status_t efi_disk_add_dev(
>
> /*
> * On partitions or whole disks without partitions install the
> - * simple file system protocol if a file system is available.
> + * simple file system protocol if a supported file system exists.
> */
> if ((part || desc->part_type == PART_TYPE_UNKNOWN) &&
> - efi_fs_exists(desc, part)) {
> + efi_supported_fs_exists(desc, part)) {
> diskobj->volume = efi_simple_file_system(desc, part,
> diskobj->dp);
> ret = efi_add_protocol(&diskobj->header,
>
