Re: [PATCH] kern/fs: honour file->read_hook in grub_fs_blocklist_read()

[Rasmus Villemoes via Grub-devel <grub-devel@gnu.org>]

"Vladimir 'phcoder' Serbinenko" <phcoder@gmail.com> writes:

> Reviewed-by: phcoder@gmail.com
>

Thanks. Can this be picked up, please?

Rasmus


> Le jeu. 29 août 2024, 14:07, Rasmus Villemoes via Grub-devel <
> grub-devel@gnu.org> a écrit :
>
>> Unlike files accessed via a normal file system, the file->read_hook is
>> not honoured when using blocklist notation.
>>
>> This means that when trying to use a dedicated, 1KiB, raw partition
>> for the environment block and hence does something like
>>
>>   save_env --file=(hd0,gpt9)0+2 X Y Z
>>
>> this fails with "sparse file not allowed", which is rather unexpected,
>> as I've explicitly said exactly which blocks should be used. Adding a
>> little debugging reveals that grub_file_size (file) is 1024 as
>> expected, but total_length is 0, simply because the callback was never
>> invoked, so blocklists is an empty list.
>>
>> Fix that by honouring the ->read_hook set by the caller, also when a
>> "file" is specified with blocklist notation.
>>
>> Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
>> ---
>> I've tried to keep the patch at a minimum, but since the
>> disk->read_hook needs to be cleared on all return paths, it seemed a
>> little easier to drop the 'return -1' and instead set ret and break.
>>
>> For readability, it seemed best to introduce the disk local variable to
>> hold file->device->disk, and then there's no point in not also using
>> that in the grub_disk_read() call.
>>
>>  grub-core/kern/fs.c | 11 +++++++++--
>>  1 file changed, 9 insertions(+), 2 deletions(-)
>>
>> diff --git a/grub-core/kern/fs.c b/grub-core/kern/fs.c
>> index 7ad0aaf4e..79f1a797c 100644
>> --- a/grub-core/kern/fs.c
>> +++ b/grub-core/kern/fs.c
>> @@ -215,12 +215,15 @@ grub_fs_blocklist_read (grub_file_t file, char *buf,
>> grub_size_t len)
>>    grub_disk_addr_t sector;
>>    grub_off_t offset;
>>    grub_ssize_t ret = 0;
>> +  grub_disk_t disk = file->device->disk;
>>
>>    if (len > file->size - file->offset)
>>      len = file->size - file->offset;
>>
>>    sector = (file->offset >> GRUB_DISK_SECTOR_BITS);
>>    offset = (file->offset & (GRUB_DISK_SECTOR_SIZE - 1));
>> +  disk->read_hook = file->read_hook;
>> +  disk->read_hook_data = file->read_hook_data;
>>    for (p = file->data; p->length && len > 0; p++)
>>      {
>>        if (sector < p->length)
>> @@ -232,9 +235,12 @@ grub_fs_blocklist_read (grub_file_t file, char *buf,
>> grub_size_t len)
>>                >> GRUB_DISK_SECTOR_BITS) > p->length - sector)
>>             size = ((p->length - sector) << GRUB_DISK_SECTOR_BITS) -
>> offset;
>>
>> -         if (grub_disk_read (file->device->disk, p->offset + sector,
>> offset,
>> +         if (grub_disk_read (disk, p->offset + sector, offset,
>>                               size, buf) != GRUB_ERR_NONE)
>> -           return -1;
>> +           {
>> +             ret = -1;
>> +             break;
>> +           }
>>
>>           ret += size;
>>           len -= size;
>> @@ -244,6 +250,7 @@ grub_fs_blocklist_read (grub_file_t file, char *buf,
>> grub_size_t len)
>>        else
>>         sector -= p->length;
>>      }
>> +  disk->read_hook = 0;
>>
>>    return ret;
>>  }
>> --
>> 2.46.0
>>
>>
>> _______________________________________________
>> Grub-devel mailing list
>> Grub-devel@gnu.org
>> https://lists.gnu.org/mailman/listinfo/grub-devel
>>

_______________________________________________
Grub-devel mailing list
Grub-devel@gnu.org
https://lists.gnu.org/mailman/listinfo/grub-devel