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

[Michael Chang]

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. 

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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