[PATCH 4/4] bootm: introduce bootm.root_arg variable

[Fabian Pflug]

The bootm.root_arg variable will be responsible for the root= part of
the kernel commandline if bootm.appendroot is set and a root device has
been selected.
root_arg allows to replace the root=/dev/... with verity=/dev/..., which
is useful in a verified boot context, where you pass the root file
system to the initramfs, but do not want the kernel to be able to parse
and mount the rootfs. With renaming the root= to something different,
you make sure, that the kernel does not mount the rootfs.

Signed-off-by: Fabian Pflug <f.pflug at pengutronix.de>
---
 common/bootm.c  | 8 ++++++--
 include/bootm.h | 1 +
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/common/bootm.c b/common/bootm.c
index 5d7dc00e3e..a1aba06f0e 100644
--- a/common/bootm.c
+++ b/common/bootm.c
@@ -69,6 +69,7 @@ void bootm_data_init_defaults(struct bootm_data *data)
 		data->initrd_file = getenv_nonempty("global.bootm.initrd");
 	}
 	data->root_dev = getenv_nonempty("global.bootm.root_dev");
+	data->root_arg = getenv_nonempty("global.bootm.root_arg");
 	data->verify = bootm_get_verify_mode();
 	data->appendroot = bootm_appendroot;
 	data->provide_machine_id = bootm_provide_machine_id;
@@ -88,6 +89,7 @@ void bootm_data_restore_defaults(const struct bootm_data *data)
 		globalvar_set("bootm.initrd", data->initrd_file);
 	}
 	globalvar_set("bootm.root_dev", data->root_dev);
+	globalvar_set("bootm.root_arg", data->root_arg);
 	bootm_set_verify_mode(data->verify);
 	bootm_appendroot = data->appendroot;
 	bootm_provide_machine_id = data->provide_machine_id;
@@ -868,10 +870,10 @@ int bootm_boot(struct bootm_data *bootm_data)
 		} else {
 			char *rootarg;
 			if(rootopts) {
-				rootarg = xasprintf("root=%s %s", root, rootopts);
+				rootarg = xasprintf("%s=%s %s", bootm_data->root_arg, root, rootopts);
 				free(rootopts);
 			} else {
-				rootarg = xasprintf("root=%s", root);
+				rootarg = xasprintf("%s=%s", bootm_data->root_arg, root);
 			}
 			free(root);
 			pr_info("Adding \"%s\" to Kernel commandline\n", rootarg);
@@ -1116,6 +1118,7 @@ static int bootm_init(void)
 	globalvar_add_simple("bootm.image.loadaddr", NULL);
 	globalvar_add_simple("bootm.oftree", NULL);
 	globalvar_add_simple("bootm.root_dev", NULL);
+	globalvar_add_simple("bootm.root_arg", "root");
 	globalvar_add_simple("bootm.tee", NULL);
 	globalvar_add_simple_bool("bootm.appendroot", &bootm_appendroot);
 	globalvar_add_simple_bool("bootm.earlycon", &bootm_earlycon);
@@ -1173,5 +1176,6 @@ BAREBOX_MAGICVAR(global.bootm.verbose, "bootm default verbosity level (0=quiet)"
 BAREBOX_MAGICVAR(global.bootm.earlycon, "Add earlycon option to Kernel for early log output");
 BAREBOX_MAGICVAR(global.bootm.appendroot, "Add root= option to Kernel to mount rootfs from the device the Kernel comes from (default, device can be overridden via global.bootm.root_dev)");
 BAREBOX_MAGICVAR(global.bootm.root_dev, "bootm default root device (overrides default device in global.bootm.appendroot)");
+BAREBOX_MAGICVAR(global.bootm.root_arg, "bootm default name arg for the root partition (normally 'root' for root=/dev/...)");
 BAREBOX_MAGICVAR(global.bootm.provide_machine_id, "If true, append systemd.machine_id=$global.machine_id to Kernel command line");
 BAREBOX_MAGICVAR(global.bootm.provide_hostname, "If true, append systemd.hostname=$global.hostname to Kernel command line");
diff --git a/include/bootm.h b/include/bootm.h
index b35deb25bf..43f4258885 100644
--- a/include/bootm.h
+++ b/include/bootm.h
@@ -19,6 +19,7 @@ struct bootm_data {
 	const char *oftree_file;
 	const char *tee_file;
 	const char *root_dev;
+	const char *root_arg;
 	int verbose;
 	enum bootm_verify verify;
 	bool force;
-- 
2.47.3