[meta-oe][PATCH v2 0/1] wic: extend empty plugin with options to write zeros to partiton

[meta-oe][PATCH v2 0/1] wic: extend empty plugin with options to write zeros to partiton

[Lukas Funke]

From: Lukas Funke <lukas.funke@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'.

Changed in v2:
 - Added SoB
---

Malte Schmidt (1):
  wic: extend empty plugin with options to write zeros to partiton

 scripts/lib/wic/plugins/source/empty.py | 57 ++++++++++++++++++++++++-
 1 file changed, 56 insertions(+), 1 deletion(-)

-- 
2.30.2

[meta-oe][PATCH v2 1/1] wic: extend empty plugin with options to write zeros to partiton

[Lukas Funke]

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>
Signed-off-by: Lukas Funke <lukas.funke@weidmueller.com>
---
 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 9c492ca206..775631b588 100644
--- a/scripts/lib/wic/plugins/source/empty.py
+++ b/scripts/lib/wic/plugins/source/empty.py
@@ -9,9 +9,19 @@
 # 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')
@@ -19,6 +29,16 @@ 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'
@@ -31,4 +51,39 @@ 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

Re: [OE-core] [meta-oe][PATCH v2 1/1] wic: extend empty plugin with options to write zeros to partiton

[Richard Purdie]

On Wed, 2023-11-22 at 11:47 +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>
> Signed-off-by: Lukas Funke <lukas.funke@weidmueller.com>
> ---
>  scripts/lib/wic/plugins/source/empty.py | 57 ++++++++++++++++++++++++-
>  1 file changed, 56 insertions(+), 1 deletion(-)

This is probably reasonable but it needs a testcase adding to wic's
testsuite please.

(run with oe-selftest -r wic)

Cheers,

Richard