adds support for late resume

controlled by the 'late_resume' parameter, will move the trigger point
for resume to after devices have been decrypted or discovered
allows resume from encrypted swap or devices requiring extra handling be visible to the kernel

docs/configuration.md

@@ -276,6 +276,10 @@ Importing this module will run `btrfs device scan` and pull btrfs modules.
 
 When enabled, attempts to resume after hibernation if resume= is passed on the kernel command line.
 
+> Please use the following option with **CAUTION** as it can be unstable in certain configurations! Any writes to disks that occur pre-resume run the risk of causing system instability! For more information have a read of the warnings in the [kernel docs](https://www.kernel.org/doc/html/latest/power/swsusp.html).
+
+* `late_resume` (true) When enabled will attempt to resume from hibernation after decryption and device mapping, allowing resume from encrypted or otherwise hidden swap devices.
+
 ### Cryptographic modules
 
 Several cryptographic modules are provided, mostly to assist in mounting encrypted volumes and handling keyfiles.

src/ugrd/fs/resume.py

@@ -1,7 +1,8 @@
 __version__ = "0.4.0"
 
+from zenlib.util import contains, unset
 
-def handle_resume(self) -> None:
+def _resume(self) -> None:
     """Returns a bash script handling resume from hibernation.
     Checks that /sys/power/resume is writable, resume= is set, and noresume is not set, if so,
     checks if PARTUUID= is in the resume var, and tries to use blkid to find the resume device.
@@ -17,7 +18,7 @@ def handle_resume(self) -> None:
     return [
         "resumeval=$(readvar resume)",  # read the cmdline resume var
         'if ! check_var noresume && [ -n "$resumeval" ] && [ -w /sys/power/resume ]; then',
-        '    if echo "$resumeval" | grep -q "PARTUUID="; then',  # resolve partuuid to device
+        '    if echo "$resumeval" | grep -q -E "^PARTUUID=|^UUID="; then',  # resolve partuuid to device
         '        resume=$(blkid -t "$resumeval" -o device)',
         "    else",
         "        resume=$resumeval",
@@ -35,3 +36,12 @@ def handle_resume(self) -> None:
         "    fi",
         "fi",
     ]
+
+@unset('late_resume')
+def handle_resume(self) -> None:
+    return _resume(self)
+
+@contains('late_resume')
+def handle_late_resume(self) -> None:
+    self.logger.warning("WARNING: Late resume enabled, can cause instability if not used with caution. Highly recommended to read configuration documentation before use.")
+    return _resume(self)

src/ugrd/fs/resume.toml

@@ -2,3 +2,9 @@ cmdline_strings = [ "resume" ]
 
 [imports.init_early] 
 "ugrd.fs.resume" = [ "handle_resume" ]
+
+[imports.init_premount]
+"ugrd.fs.resume" = [ "handle_late_resume"]
+
+[custom_parameters]
+late_resume = "bool"