Prepare clean Sargo images and validated storage inventories

Keep internal documents out of system images while retaining license notices and package versions. Generate boot mappings from a bounded storage inventory, and allow long SSH diagnostics. Hardware boot qualification remains pending.

tundra/tools/storage_layout.py

@@ -0,0 +1,32 @@
+# SPDX-License-Identifier: MPL-2.0
+"""Validate an inventoried, single-extent Sargo userdata mapping."""
+import re
+
+
+def mount_table(layout):
+    device = layout.get('device')
+    if device != '/dev/mmcblk0p72':
+        raise ValueError('Expected Sargo userdata, not another partition')
+    if not re.fullmatch(r'[0-9a-f]{64}', layout.get('firstMiBSha256', '')):
+        raise ValueError('Missing userdata identity checksum')
+    match = re.fullmatch(r'0 ([0-9]+) linear ([0-9]+:[0-9]+) ([0-9]+)',
+                         layout.get('table', ''))
+    if not match:
+        raise ValueError('Only a single linear extent is supported')
+    sectors, backing, offset = int(match[1]), match[2], int(match[3])
+    size = int(layout['size'])
+    if size <= 0 or size % 512 or sectors <= 0 or offset < 2048:
+        raise ValueError('Invalid userdata extent geometry')
+    if (sectors + offset) * 512 > size:
+        raise ValueError('Extent exceeds userdata')
+    if layout.get('schema') == 2:
+        if (layout.get('partitionLabel') != 'userdata' or
+                layout.get('filesystem') != 'ext4' or
+                layout.get('backingDevice') != backing):
+            raise ValueError('Mapping must be ext4 on the inventoried userdata device')
+    elif not (layout['table'] == '0 104448000 linear 259:40 329728'
+              and size == 53648801280):
+        raise ValueError('A new layout requires a schema 2 inventory')
+    # Kernel major/minor numbers can change between boots. The partition path
+    # is stable with this Sargo kernel, and its first MiB is checked before use.
+    return f'0 {sectors} linear {device} {offset}'