src/context: add support for systemd.verity_root_data= in the kernel …

…cmdline

Both systemd[1] and systemd-veritysetup-generator[2] define and use the
specific systemd kernel parameter systemd.verity_root_data= to setup the
integrity protected for the root file-system.

This looks for the kernel parameter systemd.verity_root_data= to guess
the booted slot name if root= is not unset.

[1]: https://www.freedesktop.org/software/systemd/man/kernel-command-line.html#roothash=
[2]: https://www.freedesktop.org/software/systemd/man/systemd-veritysetup-generator.html#systemd.verity_root_data=

Signed-off-by: Arnaud Rebillout <[email protected]>
Signed-off-by: Gaël PORTAY <[email protected]>

src/context.c

@@ -53,6 +53,9 @@ static const gchar* get_cmdline_bootname(void)
 	}
 
 	bootname = regex_match("root=(\\S+)", contents);
+	if (!bootname)
+		bootname = regex_match("systemd\\.verity_root_data=(\\S+)", contents);
+
 	if (!bootname)
 		return NULL;