On Wed, Sep 11, 2019 at 07:31:31PM +0200, Heinrich Schuchardt wrote:
On 9/11/19 8:16 AM, AKASHI Takahiro wrote:
Heinrich,
On Fri, Aug 23, 2019 at 09:04:21AM +0900, AKASHI Takahiro wrote:
On Thu, Aug 22, 2019 at 12:52:41PM +0200, Heinrich Schuchardt wrote:
On 8/22/19 11:11 AM, Mark Kettenis wrote:
From: AKASHI Takahiro takahiro.akashi@linaro.org Date: Thu, 22 Aug 2019 17:06:25 +0900
Currently, a whole disk without any partitions is not associated with EFI_SIMPLE_FILE_SYSTEM_PROTOCOL. So even if it houses FAT file system, there is a chance that we may not be able to access it, particularly, when accesses are to be attempted after searching that protocol against a device handle.
With this patch, EFI_SIMPLE_FILE_SYSTEM_PROTOCOL is installed to such a disk if part_get_info() shows there is not partition table installed on it.
Do other UEFI implementations support this?
What use cases exist that come without partition table?
I didn't find any *explicit* description in UEFI specification that mandates that any block device should have a partition table. It may be mandatory for boot(able) disks, but for others?
You can create an MBR with partition table that is a valid start of a file system.
Obviously we can do that, but if this is not a mandatory requirement, we'd better support no-partitioned cases.
I did not mean this as a requirement but as a source of errors.
My idea is that could have an MBR which by chance looks like the start of a file system. When you now expose this non-existent file system the UEFI client may create havoc.
See below.
Any further comments?
-Takahiro Akashi
So you should first check if a partition table exists. Only if none exists you can test for a possible file system.
I don't get your point. Are you saying that we should support a file system for a disk only if it has a file system? This is not true even for existing partitions as FILE_SYSTEM PROTOCOL is always installed to every partition whether or not it really houses a file system under the current implementation.
That sounds like a bug. If a partition isn't formatted we would not even know whether to call the FAT or the EXT4 driver.
Yes, the issue does exist in the current implementation. So a good approach is 1. Check if a partition table is installed or not 2. If yes, 2-1 If a partition has a file system, install FILE_SYSTEM_PROTOCOL to *that* partition. 2-2 not install FILE_SYSTEM_PROTOCOL to a whole disk 3. If no, and only if a file system exists, install FILE_SYSTEM_PROTOCOL to a whole disk
(2.1) and additional check at (3) should be added.
-Takahiro Akashi
Regards
Heinrich
Thanks, -Takahiro Akashi
Best regards
Heinrich
Signed-off-by: AKASHI Takahiro takahiro.akashi@linaro.org
lib/efi_loader/efi_disk.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/lib/efi_loader/efi_disk.c b/lib/efi_loader/efi_disk.c index 7a6b06821a47..548fe667e6f8 100644 --- a/lib/efi_loader/efi_disk.c +++ b/lib/efi_loader/efi_disk.c @@ -239,6 +239,7 @@ static efi_status_t efi_disk_add_dev( struct efi_disk_obj **disk) { struct efi_disk_obj *diskobj;
disk_partition_t info; efi_status_t ret;
/* Don't add empty devices */
@@ -270,7 +271,8 @@ static efi_status_t efi_disk_add_dev( diskobj->dp); if (ret != EFI_SUCCESS) return ret;
- if (part >= 1) {
- /* partitions or whole disk without partitions */
- if (part >= 1 || part_get_info(desc, part, &info)) { diskobj->volume = efi_simple_file_system(desc, part, diskobj->dp); ret = efi_add_protocol(&diskobj->header,
-- 2.21.0
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