[PATCH 0/3] bootm: append automatic parameters after all other linux.bootargs

[PATCH 0/3] bootm: append automatic parameters after all other linux.bootargs

[Ahmad Fatoum]

bootm can be configured to determine suitable values for a number of
kernel command line options that will automatically be fixed up.

Currently, these options are concatenated into the kernel command line
interleaved with all other options in the lexicographical order of the
linux.bootargs. parameter name.

For the root= option, this means that any root= in a blspec file for
example will override barebox' own root=, because:

  global.linux.bootargs.bootm.root < global.linux.bootargs.dyn.bootentries

The other way makes more sense however, especially as there is always a
device parameter or Kconfig option to control whether the fixup should
happen at all.

With the new order, it's now possible to set global.bootm.appendroot=1
and have barebox append a new root= and have it take precedence over a
bootloader spec provided root=. To reflect that this has occurred, the
kernel command-line will continue to list two root='s, which greatly
simplifies debugging if issues happen (e.g. because there was a
rootfstype that is no longer accurate).

Ahmad Fatoum (3):
  common: fix help text reference to internal imagicvars
  Documentation: user: booting-linux: split off mtdparts fixup section
  bootm: append automatic parameters after all other linux.bootargs

 .../migration-guides/migration-master.rst     |  9 +++
 Documentation/user/booting-linux.rst          | 69 +++++++++++++------
 common/Kconfig                                |  7 +-
 common/bootm.c                                | 26 +++++--
 4 files changed, 79 insertions(+), 32 deletions(-)

-- 
2.47.3

[PATCH 1/3] common: fix help text reference to internal imagicvars

[Ahmad Fatoum]

Both ${global.linux.bootargs.bootm.appendroot} and
${global.linux.bootargs.machine_id} are magic vars internally populated
by barebox to hold the computed root= or systemd.machine_id options.

They are out of place in the help text as they are an implementation
detail and not user API. In the case of CONFIG_MMCBLKDEV_ROOTARG, it's
even incorrect as the help text is talking about what a user can do to
trigger the root= appending and that should be either
global.bootm.appendroot=1 or adding linux-appendroot to the blspec file.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 common/Kconfig | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/common/Kconfig b/common/Kconfig
index fd422714d560..28a89265b386 100644
--- a/common/Kconfig
+++ b/common/Kconfig
@@ -769,7 +769,7 @@ config MMCBLKDEV_ROOTARG
 	  kernel doesn't contain commit [1]. The first linux kernel release
 	  containing that commit is v5.10-rc1.
 
-	  The appending only happens if barebox' 'linux.bootargs.bootm.appendroot'
+	  The appending only happens if barebox' 'global.bootm.appendroot'
 	  variable is set or the used blspec entry contains 'linux-appendroot'.
 
 	  Note: It is crucial that the kernel device tree and the barebox device
@@ -1285,8 +1285,9 @@ config MACHINE_ID
 	  updating barebox the machine id might change.
 
 	  global.bootm.provide_machine_id may be used to automatically set
-	  the linux.bootargs.machine_id global variable with a value of
-	  systemd.machine_id=${global.machine_id}
+	  fix up the kernel command line on boot with 
+
+	    systemd.machine_id=${global.machine_id}
 
 	  Note: if no hashable information is available no machine id will be passed
 	  to the kernel.
-- 
2.47.3

[PATCH 2/3] Documentation: user: booting-linux: split off mtdparts fixup section

[Ahmad Fatoum]

Specifying mtdparts on the command line instead of the device tree is
not as relevant nowadays, so move it into its own section at the end as
not to clutter the more relevant global.linux.bootargs section that is
going to be extended in a later commit.

While at it, extend it to cover the related blkdevparts as well.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 Documentation/user/booting-linux.rst | 55 +++++++++++++++-------------
 1 file changed, 30 insertions(+), 25 deletions(-)

diff --git a/Documentation/user/booting-linux.rst b/Documentation/user/booting-linux.rst
index 3972777f30cf..cc0bdb4661ca 100644
--- a/Documentation/user/booting-linux.rst
+++ b/Documentation/user/booting-linux.rst
@@ -98,31 +98,6 @@ with ``global.linux.bootargs.`` will be concatenated to the bootargs:
 
   Kernel command line: console=ttymxc0,115200n8 earlyprintk ignore_loglevel
 
-Additionally all variables starting with ``global.linux.mtdparts.`` are concatenated
-to a ``mtdparts=`` parameter to the kernel. This makes it possible to consistently
-partition devices with the :ref:`command_addpart` command and pass the same string as used
-with addpart to the Kernel:
-
-.. code-block:: sh
-
-  norparts="512k(bootloader),512k(env),4M(kernel),-(root)"
-  nandparts="1M(bootloader),1M(env),4M(kernel),-(root)"
-
-  global linux.mtdparts.nor0="physmap-flash.0:$norparts"
-  global linux.mtdparts.nand0="mxc_nand:$nandparts"
-
-  addpart /dev/nor0 $norparts
-  addpart /dev/nand0 $nandparts
-
-  ...
-
-  bootm zImage
-
-  ...
-
-  Kernel command line: mtdparts=physmap-flash.0:512k(bootloader),512k(env),4M(kernel),-(root);
-			mxc_nand:1M(bootloader),1M(env),4M(kernel),-(root)
-
 Creating root= options for the Kernel
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
@@ -380,3 +355,33 @@ If the preconfigured paths or names are not suitable, they can be adjusted in
 
 ``boot net`` will then retrieve the kernel (and also the device tree and
 initramfs, if used) over TFTP and boot it.
+
+mtdparts/blkdevparts fixup
+--------------------------
+
+All variables starting with ``global.linux.mtdparts.`` or ``global.linux.blkdevparts``
+are concatenated to a ``mtdparts=`` or ``blkdevparts=`` parameter to the
+kernel, respectively.
+This makes it possible to consistently partition devices with the :ref:`command_addpart`
+command and pass the same string as used with addpart to the Kernel:
+
+.. code-block:: sh
+
+  norparts="512k(bootloader),512k(env),4M(kernel),-(root)"
+  nandparts="1M(bootloader),1M(env),4M(kernel),-(root)"
+
+  global linux.mtdparts.nor0="physmap-flash.0:$norparts"
+  global linux.mtdparts.nand0="mxc_nand:$nandparts"
+
+  addpart /dev/nor0 $norparts
+  addpart /dev/nand0 $nandparts
+
+  ...
+
+  bootm zImage
+
+  ...
+
+  Kernel command line: mtdparts=physmap-flash.0:512k(bootloader),512k(env),4M(kernel),-(root);
+			mxc_nand:1M(bootloader),1M(env),4M(kernel),-(root)
+
-- 
2.47.3

[PATCH 3/3] bootm: append automatic parameters after all other linux.bootargs

[Ahmad Fatoum]

bootm can be configured to determine suitable values for a number of
kernel command line options that will automatically be fixed up.

Currently, these options are concatenated into the kernel command line
interleaved with all other options in the lexicographical order of the
linux.bootargs. parameter name.

For the root= option, this means that any root= in a blspec file for
example will override barebox' own root=, because:

  global.linux.bootargs.bootm.root < global.linux.bootargs.dyn.bootentries

The other way makes more sense however, especially as there is always a
device parameter or Kconfig option to control whether the fixup should
happen at all.

With the new order, it's now possible to set global.bootm.appendroot=1
and have barebox append a new root= and have it take precedence over a
bootloader spec provided root=. To reflect that this has occurred, the
kernel command-line will continue to list two root='s, which greatly
simplifies debugging if issues happen (e.g. because there was a
rootfstype that is no longer accurate).

This commit doesn't add any LINUX_BOOTARGS_BOOTM_EARLY as it's not yet
needed. Still it lays out how it could look like in future.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 .../migration-guides/migration-master.rst     |  9 +++++++
 Documentation/user/booting-linux.rst          | 24 +++++++++++++++--
 common/bootm.c                                | 26 ++++++++++++++-----
 3 files changed, 50 insertions(+), 9 deletions(-)

diff --git a/Documentation/migration-guides/migration-master.rst b/Documentation/migration-guides/migration-master.rst
index 5be4659d5b3d..f6d193417f1d 100644
--- a/Documentation/migration-guides/migration-master.rst
+++ b/Documentation/migration-guides/migration-master.rst
@@ -31,3 +31,12 @@ Scripts that **read** the parameter will now receive ``"disabled"`` or
 ``"enabled"`` instead of ``"0"`` or ``"1"``.
 
 Scripts that **write** ``"0"`` or ``"1"`` continue to work.
+
+global.linux.bootargs.* appending order
+---------------------------------------
+
+If barebox was configured to automatically generate any of the ``root``,
+``rootwait``, ``earlycon``, ``systemd.machine_id``, ``systemd.hostname``
+or ``barebox.security.policy`` kernel command line options, they will be
+appended onto the final kernel command line
+:ref:`**after** all other options <bootargs_concat_order>`.
diff --git a/Documentation/user/booting-linux.rst b/Documentation/user/booting-linux.rst
index cc0bdb4661ca..7bbb79ecdfc2 100644
--- a/Documentation/user/booting-linux.rst
+++ b/Documentation/user/booting-linux.rst
@@ -89,14 +89,34 @@ with ``global.linux.bootargs.`` will be concatenated to the bootargs:
 
 .. code-block:: sh
 
+  global linux.bootargs.Loglevel="ignore_loglevel"
   global linux.bootargs.base="console=ttyO0,115200"
-  global linux.bootargs.debug="earlyprintk ignore_loglevel"
+  global linux.bootargs.debug="earlyprintk"
 
   bootm zImage
 
   ...
 
-  Kernel command line: console=ttymxc0,115200n8 earlyprintk ignore_loglevel
+  Kernel command line: ignore_loglevel console=ttyO0,115200 earlyprintk
+
+.. _bootargs_concat_order:
+
+Concatenation order
+"""""""""""""""""""
+
+The kernel command line arguments are concatenated in lexicographical order of
+their ``linux.bootargs.``-prefixed parameter names.
+
+Kernel command line arguments that barebox generates internally are not
+interleaved with externally provided command-line arguments:
+
+* Following arguments will be concatenated **after** all other options:
+  * ``root=`` and ``rootwait=`` controlled by :ref:`global.bootm.appendroot <magicvar_global_bootm_appendroot>`
+    :ref:`global.linux.rootwait <magicvar_global_linux_rootwait>`
+  * ``earlycon=`` controlled by :ref:`global.bootm.earlycon <magicvar_global_bootm_earlycon>`
+  * ``systemd.machine_id=`` controlled by :ref:`global.bootm.provide_machine_id <magicvar_global_bootm_provide_machine_id>`
+  * ``systemd.hostname=`` controlled by :ref:`global.bootm.provide_hostname <magicvar_global_bootm_provide_hostname>`
+  * ``barebox.security.policy=`` controlled by :ref:`global.bootm.provide_policy <magicvar_global_bootm_provide_policy>`
 
 Creating root= options for the Kernel
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/common/bootm.c b/common/bootm.c
index c7bf414effa4..26465875ad94 100644
--- a/common/bootm.c
+++ b/common/bootm.c
@@ -22,6 +22,19 @@
 #include <security/config.h>
 #include <security/policy.h>
 
+/*
+ * All device parameter iteration happens in lexicographical order.
+ * To ensure that bootm options are consistently applied before or after
+ * other options from the environment or boot configuration files, we
+ * employ following convention for the prefix:
+ *
+ *   !		0x21 is less than any non-space printable character
+ *   ~		0x7e is greater than any printable character
+ *
+ * Users will never see those as bootm_boot_cleanup() will delete them again.
+ */
+#define LINUX_BOOTARGS_BOOTM_LATE	"linux.bootargs.~bootm."
+
 static LIST_HEAD(handler_list);
 static struct sconfig_notifier_block sconfig_notifier;
 
@@ -650,7 +663,7 @@ struct image_data *bootm_boot_prep(const struct bootm_data *bootm_data)
 
 			rootarg = format_root_bootarg(bootm_data->root_param, root, rootopts);
 			pr_info("Adding \"%s\" to Kernel commandline\n", rootarg);
-			globalvar_add_simple("linux.bootargs.bootm.appendroot",
+			globalvar_add_simple(LINUX_BOOTARGS_BOOTM_LATE "appendroot",
 					     rootarg);
 			free(rootarg);
 		}
@@ -672,7 +685,7 @@ struct image_data *bootm_boot_prep(const struct bootm_data *bootm_data)
 			earlycon = "earlycon";
 
 		pr_info("Adding \"%s\" to Kernel commandline\n", earlycon);
-		globalvar_add_simple("linux.bootargs.bootm.earlycon", earlycon);
+		globalvar_add_simple(LINUX_BOOTARGS_BOOTM_LATE "earlycon", earlycon);
 	}
 
 	if (bootm_data->provide_machine_id) {
@@ -686,7 +699,7 @@ struct image_data *bootm_boot_prep(const struct bootm_data *bootm_data)
 		}
 
 		machine_id_bootarg = basprintf("systemd.machine_id=%s", machine_id);
-		globalvar_add_simple("linux.bootargs.machine_id", machine_id_bootarg);
+		globalvar_add_simple(LINUX_BOOTARGS_BOOTM_LATE "machine_id", machine_id_bootarg);
 		free(machine_id_bootarg);
 	}
 
@@ -714,7 +727,7 @@ struct image_data *bootm_boot_prep(const struct bootm_data *bootm_data)
 					     hostname, suffix ? "-" : "",
 					     suffix ?: "");
 
-		globalvar_add_simple("linux.bootargs.hostname", hostname_bootarg);
+		globalvar_add_simple(LINUX_BOOTARGS_BOOTM_LATE "hostname", hostname_bootarg);
 		free(hostname_bootarg);
 	}
 
@@ -729,7 +742,7 @@ struct image_data *bootm_boot_prep(const struct bootm_data *bootm_data)
 		}
 
 		policy_bootargs = basprintf("barebox.security.policy=%s", active_policy->name);
-		globalvar_add_simple("linux.bootargs.dyn.policy", policy_bootargs);
+		globalvar_add_simple(LINUX_BOOTARGS_BOOTM_LATE "policy", policy_bootargs);
 		free(policy_bootargs);
 	}
 
@@ -792,8 +805,7 @@ void bootm_boot_cleanup(struct image_data *data)
 	if (data->of_root_node)
 		of_delete_node(data->of_root_node);
 
-	globalvar_remove("linux.bootargs.bootm.earlycon");
-	globalvar_remove("linux.bootargs.bootm.appendroot");
+	globalvar_remove(LINUX_BOOTARGS_BOOTM_LATE  "*");
 	free(data->os_header);
 	free(data->os_file);
 	free(data->oftree_file);
-- 
2.47.3

Re: [PATCH 3/3] bootm: append automatic parameters after all other linux.bootargs

[Alexander Shiyan]

Tested-by: Alexander Shiyan <eagle.alexander923@gmail.com>

вт, 5 мая 2026 г. в 12:51, Ahmad Fatoum <a.fatoum@pengutronix.de>:
>
> bootm can be configured to determine suitable values for a number of
> kernel command line options that will automatically be fixed up.
>
> Currently, these options are concatenated into the kernel command line
> interleaved with all other options in the lexicographical order of the
> linux.bootargs. parameter name.
>
> For the root= option, this means that any root= in a blspec file for
> example will override barebox' own root=, because:
>
>   global.linux.bootargs.bootm.root < global.linux.bootargs.dyn.bootentries
>
> The other way makes more sense however, especially as there is always a
> device parameter or Kconfig option to control whether the fixup should
> happen at all.
>
> With the new order, it's now possible to set global.bootm.appendroot=1
> and have barebox append a new root= and have it take precedence over a
> bootloader spec provided root=. To reflect that this has occurred, the
> kernel command-line will continue to list two root='s, which greatly
> simplifies debugging if issues happen (e.g. because there was a
> rootfstype that is no longer accurate).
>
> This commit doesn't add any LINUX_BOOTARGS_BOOTM_EARLY as it's not yet
> needed. Still it lays out how it could look like in future.
>
> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> ---
>  .../migration-guides/migration-master.rst     |  9 +++++++
>  Documentation/user/booting-linux.rst          | 24 +++++++++++++++--
>  common/bootm.c                                | 26 ++++++++++++++-----
>  3 files changed, 50 insertions(+), 9 deletions(-)
>
> diff --git a/Documentation/migration-guides/migration-master.rst b/Documentation/migration-guides/migration-master.rst
> index 5be4659d5b3d..f6d193417f1d 100644
> --- a/Documentation/migration-guides/migration-master.rst
> +++ b/Documentation/migration-guides/migration-master.rst
> @@ -31,3 +31,12 @@ Scripts that **read** the parameter will now receive ``"disabled"`` or
>  ``"enabled"`` instead of ``"0"`` or ``"1"``.
>
>  Scripts that **write** ``"0"`` or ``"1"`` continue to work.
> +
> +global.linux.bootargs.* appending order
> +---------------------------------------
> +
> +If barebox was configured to automatically generate any of the ``root``,
> +``rootwait``, ``earlycon``, ``systemd.machine_id``, ``systemd.hostname``
> +or ``barebox.security.policy`` kernel command line options, they will be
> +appended onto the final kernel command line
> +:ref:`**after** all other options <bootargs_concat_order>`.
> diff --git a/Documentation/user/booting-linux.rst b/Documentation/user/booting-linux.rst
> index cc0bdb4661ca..7bbb79ecdfc2 100644
> --- a/Documentation/user/booting-linux.rst
> +++ b/Documentation/user/booting-linux.rst
> @@ -89,14 +89,34 @@ with ``global.linux.bootargs.`` will be concatenated to the bootargs:
>
>  .. code-block:: sh
>
> +  global linux.bootargs.Loglevel="ignore_loglevel"
>    global linux.bootargs.base="console=ttyO0,115200"
> -  global linux.bootargs.debug="earlyprintk ignore_loglevel"
> +  global linux.bootargs.debug="earlyprintk"
>
>    bootm zImage
>
>    ...
>
> -  Kernel command line: console=ttymxc0,115200n8 earlyprintk ignore_loglevel
> +  Kernel command line: ignore_loglevel console=ttyO0,115200 earlyprintk
> +
> +.. _bootargs_concat_order:
> +
> +Concatenation order
> +"""""""""""""""""""
> +
> +The kernel command line arguments are concatenated in lexicographical order of
> +their ``linux.bootargs.``-prefixed parameter names.
> +
> +Kernel command line arguments that barebox generates internally are not
> +interleaved with externally provided command-line arguments:
> +
> +* Following arguments will be concatenated **after** all other options:
> +  * ``root=`` and ``rootwait=`` controlled by :ref:`global.bootm.appendroot <magicvar_global_bootm_appendroot>`
> +    :ref:`global.linux.rootwait <magicvar_global_linux_rootwait>`
> +  * ``earlycon=`` controlled by :ref:`global.bootm.earlycon <magicvar_global_bootm_earlycon>`
> +  * ``systemd.machine_id=`` controlled by :ref:`global.bootm.provide_machine_id <magicvar_global_bootm_provide_machine_id>`
> +  * ``systemd.hostname=`` controlled by :ref:`global.bootm.provide_hostname <magicvar_global_bootm_provide_hostname>`
> +  * ``barebox.security.policy=`` controlled by :ref:`global.bootm.provide_policy <magicvar_global_bootm_provide_policy>`
>
>  Creating root= options for the Kernel
>  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> diff --git a/common/bootm.c b/common/bootm.c
> index c7bf414effa4..26465875ad94 100644
> --- a/common/bootm.c
> +++ b/common/bootm.c
> @@ -22,6 +22,19 @@
>  #include <security/config.h>
>  #include <security/policy.h>
>
> +/*
> + * All device parameter iteration happens in lexicographical order.
> + * To ensure that bootm options are consistently applied before or after
> + * other options from the environment or boot configuration files, we
> + * employ following convention for the prefix:
> + *
> + *   !         0x21 is less than any non-space printable character
> + *   ~         0x7e is greater than any printable character
> + *
> + * Users will never see those as bootm_boot_cleanup() will delete them again.
> + */
> +#define LINUX_BOOTARGS_BOOTM_LATE      "linux.bootargs.~bootm."
> +
>  static LIST_HEAD(handler_list);
>  static struct sconfig_notifier_block sconfig_notifier;
>
> @@ -650,7 +663,7 @@ struct image_data *bootm_boot_prep(const struct bootm_data *bootm_data)
>
>                         rootarg = format_root_bootarg(bootm_data->root_param, root, rootopts);
>                         pr_info("Adding \"%s\" to Kernel commandline\n", rootarg);
> -                       globalvar_add_simple("linux.bootargs.bootm.appendroot",
> +                       globalvar_add_simple(LINUX_BOOTARGS_BOOTM_LATE "appendroot",
>                                              rootarg);
>                         free(rootarg);
>                 }
> @@ -672,7 +685,7 @@ struct image_data *bootm_boot_prep(const struct bootm_data *bootm_data)
>                         earlycon = "earlycon";
>
>                 pr_info("Adding \"%s\" to Kernel commandline\n", earlycon);
> -               globalvar_add_simple("linux.bootargs.bootm.earlycon", earlycon);
> +               globalvar_add_simple(LINUX_BOOTARGS_BOOTM_LATE "earlycon", earlycon);
>         }
>
>         if (bootm_data->provide_machine_id) {
> @@ -686,7 +699,7 @@ struct image_data *bootm_boot_prep(const struct bootm_data *bootm_data)
>                 }
>
>                 machine_id_bootarg = basprintf("systemd.machine_id=%s", machine_id);
> -               globalvar_add_simple("linux.bootargs.machine_id", machine_id_bootarg);
> +               globalvar_add_simple(LINUX_BOOTARGS_BOOTM_LATE "machine_id", machine_id_bootarg);
>                 free(machine_id_bootarg);
>         }
>
> @@ -714,7 +727,7 @@ struct image_data *bootm_boot_prep(const struct bootm_data *bootm_data)
>                                              hostname, suffix ? "-" : "",
>                                              suffix ?: "");
>
> -               globalvar_add_simple("linux.bootargs.hostname", hostname_bootarg);
> +               globalvar_add_simple(LINUX_BOOTARGS_BOOTM_LATE "hostname", hostname_bootarg);
>                 free(hostname_bootarg);
>         }
>
> @@ -729,7 +742,7 @@ struct image_data *bootm_boot_prep(const struct bootm_data *bootm_data)
>                 }
>
>                 policy_bootargs = basprintf("barebox.security.policy=%s", active_policy->name);
> -               globalvar_add_simple("linux.bootargs.dyn.policy", policy_bootargs);
> +               globalvar_add_simple(LINUX_BOOTARGS_BOOTM_LATE "policy", policy_bootargs);
>                 free(policy_bootargs);
>         }
>
> @@ -792,8 +805,7 @@ void bootm_boot_cleanup(struct image_data *data)
>         if (data->of_root_node)
>                 of_delete_node(data->of_root_node);
>
> -       globalvar_remove("linux.bootargs.bootm.earlycon");
> -       globalvar_remove("linux.bootargs.bootm.appendroot");
> +       globalvar_remove(LINUX_BOOTARGS_BOOTM_LATE  "*");
>         free(data->os_header);
>         free(data->os_file);
>         free(data->oftree_file);
> --
> 2.47.3
>

Re: (subset) [PATCH 3/3] bootm: append automatic parameters after all other linux.bootargs

[Sascha Hauer]

On Tue, 05 May 2026 11:51:00 +0200, Ahmad Fatoum wrote:
> bootm can be configured to determine suitable values for a number of
> kernel command line options that will automatically be fixed up.
> 
> Currently, these options are concatenated into the kernel command line
> interleaved with all other options in the lexicographical order of the
> linux.bootargs. parameter name.
> 
> [...]

Applied, thanks!

[3/3] bootm: append automatic parameters after all other linux.bootargs
      https://git.pengutronix.de/cgit/barebox/commit/?id=d99ca66b6806 (link may not be stable)

Best regards,
-- 
Sascha Hauer <s.hauer@pengutronix.de>