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List:       grub-devel
Subject:    Re: [PATCH] grub2: add read_hook to blocklists
From:       Daniel Kiper <dkiper () net-space ! pl>
Date:       2019-05-28 10:09:50
Message-ID: 20190528100950.hz6ditrajhtceoo2 () tomti ! i ! net-space ! pl
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CC-ing Vladimir.

On Mon, May 27, 2019 at 10:07:27AM +0200, Michael Grzeschik wrote:
> This is needed to make grubenv be stored in
> raw disk images. We now can run
>
> save_env -f (ata0)1024+2 VARIABLE

Why do we need/want this patch? What is the usage case for it?
Could you explain why you have to change grub_fs_blocklist_read()
just to read grubenv? Could not we do that in less intrusive way?

Daniel

> Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
> ---
>  grub-core/kern/fs.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/grub-core/kern/fs.c b/grub-core/kern/fs.c
> index 2b85f4950..d50d519d2 100644
> --- a/grub-core/kern/fs.c
> +++ b/grub-core/kern/fs.c
> @@ -208,6 +208,11 @@ grub_fs_blocklist_read (grub_file_t file, char *buf, grub_size_t len)
>    grub_off_t offset;
>    grub_ssize_t ret = 0;
>
> +  if (file->read_hook)
> +	  file->device->disk->read_hook = file->read_hook;
> +  if (file->read_hook_data)
> +	  file->device->disk->read_hook_data = file->read_hook_data;
> +
>    if (len > file->size - file->offset)
>      len = file->size - file->offset;
>
> @@ -236,6 +241,7 @@ grub_fs_blocklist_read (grub_file_t file, char *buf, grub_size_t len)
>        else
>  	sector -= p->length;
>      }
> +  file->device->disk->read_hook = 0;
>
>    return ret;
>  }
> --
> 2.20.1

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