Re: [OE-Core][PATCH 1/1] wic: extend empty plugin with options to write zeros to partiton

[Alexandre Belloni <alexandre.belloni@bootlin.com>]

Hello Lukas,

On 14/11/2023 09:13:32+0100, Lukas Funke wrote:
> From: Malte Schmidt <malte.schmidt@weidmueller.com>
> 
> Adds features to explicitly write zeros to the start of the
> partition. This is useful to overwrite old content like
> filesystem signatures which may be re-recognized otherwise.
> 
> The new features can be enabled with
> '--soucreparams="[fill|size=<N>[S|s|K|k|M|G]][,][bs=<N>[S|s|K|k|M|G]]"'
> Conflicting or missing options throw errors.
> 
> The features are:
> - fill
>   Fill the entire partition with zeros. Requires '--fixed-size' option
>   to be set.
> - size=<N>[S|s|K|k|M|G]
>   Set the first N bytes of the partition to zero. Default unit is 'K'.
> - bs=<N>[S|s|K|k|M|G]
>   Write at most N bytes at a time during source file creation.
>   Defaults to '1M'. Default unit is 'K'.
> 
> Signed-off-by: Malte Schmidt <malte.schmidt@weidmueller.com>

We need your SoB here

> ---
>  scripts/lib/wic/plugins/source/empty.py | 57 ++++++++++++++++++++++++-
>  1 file changed, 56 insertions(+), 1 deletion(-)
> 
> diff --git a/scripts/lib/wic/plugins/source/empty.py b/scripts/lib/wic/plugins/source/empty.py
> index 041617d648..f7581a0298 100644
> --- a/scripts/lib/wic/plugins/source/empty.py
> +++ b/scripts/lib/wic/plugins/source/empty.py
> @@ -7,9 +7,19 @@
>  # To use it you must pass "empty" as argument for the "--source" parameter in
>  # the wks file. For example:
>  # part foo --source empty --ondisk sda --size="1024" --align 1024
> +#
> +# The plugin supports writing zeros to the start of the
> +# partition. This is useful to overwrite old content like
> +# filesystem signatures which may be re-recognized otherwise.
> +# This feature can be enabled with
> +# '--soucreparams="[fill|size=<N>[S|s|K|k|M|G]][,][bs=<N>[S|s|K|k|M|G]]"'
> +# Conflicting or missing options throw errors.
>  
>  import logging
> +import os
>  
> +from wic import WicError
> +from wic.ksparser import sizetype
>  from wic.pluginbase import SourcePlugin
>  
>  logger = logging.getLogger('wic')
> @@ -17,6 +27,16 @@ logger = logging.getLogger('wic')
>  class EmptyPartitionPlugin(SourcePlugin):
>      """
>      Populate unformatted empty partition.
> +
> +    The following sourceparams are supported:
> +    - fill
> +      Fill the entire partition with zeros. Requires '--fixed-size' option
> +      to be set.
> +    - size=<N>[S|s|K|k|M|G]
> +      Set the first N bytes of the partition to zero. Default unit is 'K'.
> +    - bs=<N>[S|s|K|k|M|G]
> +      Write at most N bytes at a time during source file creation.
> +      Defaults to '1M'. Default unit is 'K'.
>      """
>  
>      name = 'empty'
> @@ -29,4 +49,39 @@ class EmptyPartitionPlugin(SourcePlugin):
>          Called to do the actual content population for a partition i.e. it
>          'prepares' the partition to be incorporated into the image.
>          """
> -        return
> +        get_byte_count = sizetype('K', True)
> +        size = 0
> +
> +        if 'fill' in source_params and 'size' in source_params:
> +            raise WicError("Conflicting source parameters 'fill' and 'size' specified, exiting.")
> +
> +        # Set the size of the zeros to be written to the partition
> +        if 'fill' in source_params:
> +            if part.fixed_size == 0:
> +                raise WicError("Source parameter 'fill' only works with the '--fixed-size' option, exiting.")
> +            size = part.fixed_size
> +        elif 'size' in source_params:
> +            size = get_byte_count(source_params['size'])
> +
> +        if size == 0:
> +            # Nothing to do, create empty partition
> +            return
> +
> +        if 'bs' in source_params:
> +            bs = get_byte_count(source_params['bs'])
> +        else:
> +            bs = get_byte_count('1M')
> +
> +        # Create a binary file of the requested size filled with zeros
> +        source_file = os.path.join(cr_workdir, 'empty-plugin-zeros%s.bin' % part.lineno)
> +        if not os.path.exists(os.path.dirname(source_file)):
> +            os.makedirs(os.path.dirname(source_file))
> +
> +        quotient, remainder = divmod(size, bs)
> +        with open(source_file, 'wb') as file:
> +            for _ in range(quotient):
> +                file.write(bytearray(bs))
> +            file.write(bytearray(remainder))
> +
> +        part.size = (size + 1024 - 1) // 1024  # size in KB rounded up
> +        part.source_file = source_file
> -- 
> 2.30.2
> 

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-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com