Support for late resume

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.
@@ -15,23 +16,48 @@ def handle_resume(self) -> None:
     Distinguising between a fresh boot and missing/borked hibernation image is not possible at run time.
     """
     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
+        # Check resume support
+        '[ -n "$1" ] || (ewarn "No device?" ; return 1)',
+        '[ -w /sys/power/resume ] || (ewarn "Kernel does not support resume!" ; return 1)',
+        '[[ ! "$(cat /sys/power/resume)" == "0:0" ]] || ewarn "/sys/power/resume not empty, resume has already been attempted!"',
+
+        # Safety checks
+        'if ! [ -z $(lsblk -Q MOUNTPOINT)] ; then',
+        r'    eerror "Cannot safely resume with mounted block devices:\n$(lsblk -Q MOUNTPOINT -no PATH)"',
+        '    return 1',
+        'fi',
+
+        '[ -b "$1" ] || (ewarn "\'$1\' is not a valid block device!" ; return 1)',
+
+        'einfo "Attempting resume from: $1"',
+        'echo -n "$1" > /sys/power/resume',
+        'einfo "No image on $resume"',
+        'return 0',
+    ]
+
+def handle_early_resume(self) -> None:
+    return [
+        'resumeval=$(readvar resume)',
+        'if ! check_var noresume && [ -n "$resumeval" ] ; then',
+        '    if echo "$resumeval" | grep -qE "^PARTUUID=|^UUID="; then',
         '        resume=$(blkid -t "$resumeval" -o device)',
-        "    else",
-        "        resume=$resumeval",
-        "    fi",
-        '    if [ -e "$resume" ]; then',  # Check if the resume device exists
-        '        einfo "Resuming from: $resume"',
-        '        echo -n "$resume" > /sys/power/resume',  # Attempt to resume
-        '        ewarn "Failed to resume from: $resume"',
-        "    else",
-        '        ewarn "Resume device not found: $resume)"',  # Warn if the resume device does not exist
-        r'        eerror "Block devices:\n$(blkid)"',
-        '        eerror "If you wish to continue booting, remove the resume= kernel parameter."',
-        '''        eerror " or run 'setvar noresume 1' from the recovery shell to skip resuming."''',
-        '        rd_fail "Failed to resume from $(readvar resume)."',
-        "    fi",
-        "fi",
+        '    else',
+        '        resume="$resumeval"',
+        '    fi',
+
+        '    if ! [ -z $resume ] ; then',
+        '        if ! resume "$resume" ; then',
+        '            eerror "If you wish to continue booting, remove the resume= kernel parameter."',
+        '''             eerror " or run 'setvar noresume 1' from the recovery shell to skip resuming."''',
+        '            rd_fail "Failed to resume from $(readvar resume)."',
+        '        fi',
+        '    else',
+        '        einfo "Resume device \'$resumeval\' not found"',
+        '    fi',
+        'fi',
     ]
+
+@contains('late_resume')
+def handle_late_resume(self) -> None:
+    self.logger.warning("[late_resume] enabled, this can result in data loss if filesystems are modified before resuming. Read the docs for more info.")
+    return handle_early_resume(self)  # At the moment it's the same code but delayed, will change when more features are added

src/ugrd/fs/resume.toml

@@ -1,4 +1,15 @@
 cmdline_strings = [ "resume" ]
 
+binaries = [ 'lsblk' ]
+
 [imports.init_early] 
-"ugrd.fs.resume" = [ "handle_resume" ]
+"ugrd.fs.resume" = [ "handle_early_resume" ]
+
+[imports.init_premount]
+"ugrd.fs.resume" = [ "handle_late_resume"]
+
+[imports.functions]
+"ugrd.fs.resume" = ["resume"]
+
+[custom_parameters]
+late_resume = "bool"