Re: [PATCH] disk/efi: skip iPXE dummy block devices

[Andrei Borzenkov]

14.03.2017 06:03, Michael Chang пишет:
> On Mon, Mar 13, 2017 at 06:45:02AM +0300, Andrei Borzenkov wrote:
>> iPXE adds Simple File System Protocol to loaded image handle, as side
>> effect it also adds Block IO protocol (according to comments, to work
>> around some bugs in EDK2). GRUB assumes that every device with Block IO
>> is disk and skips network initialization entirely. But iPXE Block IO
>> implementation is just a stub which always fails for every operation
>> so cannot be used. Attempt to detect and skip such devices.
>>
>> We are using media ID which iPXE sets to "iPXE" and block IO size in
>> hope that no real device would announce 1B block ...
>>
>> Closes: 50518
>>
>> @Vladimir, @Daniel - this is probably 2.02 material. We cannot use
>> any device that advertises block size less than 512B anyway, so it
>> should not cause regression for disk boot.
>>
>> It is my fault, I have seen it earlier but was busy with another problem
>> so just worked around it to continue testing.
>>
>> ---
>>  grub-core/disk/efi/efidisk.c | 9 +++++++++
>>  1 file changed, 9 insertions(+)
>>
>> diff --git a/grub-core/disk/efi/efidisk.c b/grub-core/disk/efi/efidisk.c
>> index 3b79f7b..47a4e99 100644
>> --- a/grub-core/disk/efi/efidisk.c
>> +++ b/grub-core/disk/efi/efidisk.c
>> @@ -80,6 +80,15 @@ make_devices (void)
>>      /* This should not happen... Why?  */
>>      continue;
>>  
>> +      /* iPXE adds stub Block IO protocol to loaded image device handle. It 
>> is
>> +         completely non-functional and simply returns an error for every 
>> method.
>> +     So attempt to detect and skip it. Magic number is literal "iPXE" and
>> +     check block size as well */
>> +      /* FIXME: shoud we close it? We do not do it elsewhere */
>> +      if (bio->media && bio->media->media_id == 0x69505845U &&
> 
> It seems that BE to LE conversion is required here as it tests for 'EXPi' on 
> LE
> systems. 
> 

iPXE sets it to this literal number:

#define EFI_MEDIA_ID_MAGIC 0x69505845

/** Dummy block I/O media */
static EFI_BLOCK_IO_MEDIA efi_block_io_media = {
        .MediaId = EFI_MEDIA_ID_MAGIC,
        .MediaPresent = TRUE,
        .ReadOnly = TRUE,
        .BlockSize = 1,
};


> Thanks,
> Michael
> 
>> +      bio->media->block_size == 1)
>> +      continue;
>> +
>>        d = grub_malloc (sizeof (*d));
>>        if (! d)
>>      {
>> -- 
>> tg: (bcf3c55..) bug/50518 (depends on: master)
>>
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> 
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