[PATCH 1/2] Add support for extlinux.conf

[PATCH 1/2] Add support for extlinux.conf

[Alexander Shiyan]

This adds support for the extlinux.conf configuration format, commonly
used by Syslinux and many Linux distributions. The configuration file
is typically located at /boot/extlinux/extlinux.conf or
/extlinux/extlinux.conf and defines boot entries with kernel, initrd,
device tree, and command line options.

The implementation integrates with the existing boot entry framework:
- The extlinux scanner discovers entries on mounted filesystems
- Default label is turned into a boot entry
- The "root=" parameter is automatically stripped from the append line
  to allow barebox to inject the correct root device (via appendroot)
- Bootm is used to load and start the kernel
---
barebox@Diasom DS-RK3568-SOM-EVB:/ global.boot.default=mmc1.2
barebox@Diasom DS-RK3568-SOM-EVB:/ boot
ext4 ext40: EXT2 rev 1, inode_size 256, descriptor size 64
Booting entry 'extlinux: linux'
extlinux: Booting extlinux label 'linux'
Adding "root=/dev/mmcblk1p3" to Kernel commandline
Loading ARM aarch64 Linux/EFI image '/mnt/mmc1.2/boot/extlinux/../vmlinuz'
Loaded initrd from GZIP compressed /mnt/mmc1.2/boot/extlinux/../initrd.img to 0x000000000d390000-0x000000000fb48ca6
commandline: mem=0xef600000 root=/dev/mmcblk1p3 console=ttyS2,1500000n8 ro systemd.unit=setup.target quiet splash  systemd.machine_id=181af2816b4c6b0aef77068e0ccc69ad
Loaded kernel to 0x0a400000, devicetree at 0x000000000fb49000

Signed-off-by: Alexander Shiyan <eagle.alexander923@gmail.com>
---
 common/Kconfig    |  19 ++++
 common/Makefile   |   1 +
 common/extlinux.c | 271 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 291 insertions(+)
 create mode 100644 common/extlinux.c

diff --git a/common/Kconfig b/common/Kconfig
index cd002865f7..bbffbfe92c 100644
--- a/common/Kconfig
+++ b/common/Kconfig
@@ -726,6 +726,25 @@ config BLSPEC
 	  on a device and it allows the Operating System to install / update
 	  kernels.
 
+config EXTLINUX
+	bool
+	prompt "Support extlinux.conf"
+	depends on FLEXIBLE_BOOTARGS
+	depends on !SHELL_NONE
+	select BOOT
+	select BOOTM
+	select MMCBLKDEV_ROOTARG if MCI
+	help
+	  Enable this to let barebox parse extlinux.conf configuration files,
+	  commonly used by the Syslinux bootloader and many Linux distributions
+	  (e.g., on SD cards or USB drives).
+	  extlinux.conf is typically located at /boot/extlinux/extlinux.conf or
+	  /extlinux/extlinux.conf. It defines boot entries with kernel, initrd,
+	  device tree, and command line options.
+	  This option allows barebox to discover and boot operating systems
+	  that follow the extlinux configuration format, providing a simple
+	  and portable way to manage multiple boot options.
+
 config FLEXIBLE_BOOTARGS
 	bool
 	prompt "flexible Linux bootargs generation"
diff --git a/common/Makefile b/common/Makefile
index ac39ee4e3e..dda42c099a 100644
--- a/common/Makefile
+++ b/common/Makefile
@@ -9,6 +9,7 @@ obj-y				+= clock.o
 pbl-$(CONFIG_PBL_CLOCKSOURCE)	+= clock.o
 obj-y				+= console_common.o
 obj-$(CONFIG_OFDEVICE)		+= deep-probe.o
+obj-$(CONFIG_EXTLINUX)		+= extlinux.o
 obj-y				+= startup.o
 obj-y				+= misc.o
 obj-pbl-y			+= memsize.o
diff --git a/common/extlinux.c b/common/extlinux.c
new file mode 100644
index 0000000000..39d5191ecc
--- /dev/null
+++ b/common/extlinux.c
@@ -0,0 +1,271 @@
+// SPDX-License-Identifier: GPL-2.0+
+/* SPDX-FileCopyrightText: Alexander Shiyan <shc_work@mail.ru> */
+
+#define pr_fmt(fmt)     "extlinux: " fmt
+
+#include <boot.h>
+#include <bootm.h>
+#include <bootscan.h>
+#include <common.h>
+#include <environment.h>
+#include <fs.h>
+#include <globalvar.h>
+#include <libfile.h>
+#include <libgen.h>
+#include <malloc.h>
+#include <string.h>
+
+struct extlinux_entry {
+	struct bootentry entry;
+	char *rootpath;
+	char *label;
+	char *kernel;
+	char *initrd;
+	char *fdtdir;
+	char *fdt;
+	char *append;
+};
+
+static int extlinux_boot(struct bootentry *be, int verbose, int dryrun)
+{
+	struct extlinux_entry *e =
+		container_of(be, struct extlinux_entry, entry);
+	char *kernel_abs, *initrd_abs = NULL, *fdt_abs = NULL;
+	struct bootm_data data = {};
+	int ret;
+
+	bootm_data_init_defaults(&data);
+
+	data.dryrun = max_t(int, dryrun, data.dryrun);
+	data.verbose = max(verbose, data.verbose);
+	data.appendroot = true;
+
+	kernel_abs = basprintf("%s/%s", e->rootpath, e->kernel);
+	data.os_file = kernel_abs;
+
+	if (e->initrd) {
+		initrd_abs = basprintf("%s/%s", e->rootpath, e->initrd);
+		data.initrd_file = initrd_abs;
+	}
+
+	if (e->fdt) {
+		char *fdtdir = e->fdtdir ? : e->rootpath;
+
+		fdt_abs = basprintf("%s/%s", fdtdir, e->fdt);
+		data.oftree_file = fdt_abs;
+	}
+
+	if (e->append)
+		globalvar_add_simple("linux.bootargs.dyn.extlinux", e->append);
+
+	pr_info("Booting extlinux label '%s'\n", e->label);
+
+	ret = bootm_boot(&data);
+	if (ret)
+		pr_err("bootm failed: %s\n", strerror(-ret));
+
+	free(kernel_abs);
+	free(initrd_abs);
+	free(fdt_abs);
+
+	return ret;
+}
+
+static void extlinux_entry_free(struct bootentry *be)
+{
+	struct extlinux_entry *e =
+		container_of(be, struct extlinux_entry, entry);
+
+	free(e->rootpath);
+	free(e->label);
+	free(e->kernel);
+	free(e->initrd);
+	free(e->fdtdir);
+	free(e->fdt);
+	free(e->append);
+	free(e);
+}
+
+static char *remove_param(const char *params, const char *param)
+{
+	char *result, *dst;
+	const char *src;
+
+	result = xmalloc(strlen(params) + 1);
+
+	src = params;
+	dst = result;
+
+	while (*src) {
+		if (!strncasecmp(src, param, strlen(param))) {
+			while (*src && *src != ' ')
+				src++;
+
+			src = skip_spaces(src);
+
+			continue;
+		}
+
+		*dst++ = *src++;
+	}
+
+	*dst = '\0';
+
+	return result;
+}
+
+static struct extlinux_entry *parse_extlinux_conf(const char *abspath,
+						  const char *rootpath)
+{
+	char *buf, *bufptr, *line, *p, *default_label = NULL;
+	struct extlinux_entry *entry = NULL;
+
+	bufptr = read_file(abspath, NULL);
+	if (!bufptr)
+		return ERR_PTR(-errno);
+
+	for (p = bufptr; *p; p++)
+		if (*p == '\r')
+			*p = '\n';
+
+	buf = bufptr;
+	while ((line = strsep(&buf, "\n")) != NULL) {
+		char *key, *val;
+
+		line = skip_spaces(line);
+
+		if (*line == '#' || *line == '\0')
+			continue;
+
+		key = line;
+		val = strchr(line, ' ');
+		if (!val)
+			val = strchr(line, '\t');
+		if (val) {
+			*val++ = '\0';
+			val = skip_spaces(val);
+		} else
+			continue;
+
+		if (!default_label) {
+			if (!strcasecmp(key, "DEFAULT"))
+				default_label = xstrdup(val);
+
+			continue;
+		}
+
+		if (!strcasecmp(key, "LABEL")) {
+			if (!strcmp(val, default_label)) {
+				entry = xzalloc(sizeof(*entry));
+				entry->label = xstrdup(val);
+				entry->rootpath = dirname(xstrdup(abspath));
+			} else if (entry)
+				break;
+			continue;
+		}
+
+		/*
+		 * The same rootfs image may be launched from eMMC or SD card.
+		 * Remove any hardcoded root= parameter from "append" to avoid
+		 * conflicts, then let barebox automatically add the correct
+		 * root= (via appendroot) based on the boot device.
+		 */
+		if (entry) {
+			if (!strcasecmp(key, "KERNEL"))
+				entry->kernel = xstrdup(val);
+			else if (!strcasecmp(key, "INITRD"))
+				entry->initrd = xstrdup(val);
+			else if (!strcasecmp(key, "FDTDIR"))
+				entry->fdtdir = xstrdup(val);
+			else if (!strcasecmp(key, "FDT"))
+				entry->fdt = xstrdup(val);
+			else if (!strcasecmp(key, "APPEND"))
+				entry->append = remove_param(val, "ROOT=");
+			else
+				pr_debug("Unhandled key: %s\n", key);
+		}
+	}
+
+	free(default_label);
+	free(bufptr);
+
+	if (!entry || !entry->kernel) {
+		if (entry)
+			extlinux_entry_free(&entry->entry);
+		return ERR_PTR(-EINVAL);
+	}
+
+	return entry;
+}
+
+static int extlinux_scan_file(struct bootscanner *scanner,
+			      struct bootentries *bootentries,
+			      const char *configname)
+{
+	struct extlinux_entry *e;
+	const char *rootpath;
+
+	if (!strends(configname, "extlinux.conf"))
+		return 0;
+
+	rootpath = get_mounted_path(configname);
+	if (IS_ERR(rootpath))
+		return PTR_ERR(rootpath);
+
+	e = parse_extlinux_conf(configname, rootpath);
+	if (IS_ERR(e))
+		return PTR_ERR(e);
+
+	e->entry.boot = extlinux_boot;
+	e->entry.release = extlinux_entry_free;
+	e->entry.path = xstrdup(configname);
+	e->entry.title = basprintf("extlinux: %s", e->label);
+	e->entry.description = basprintf("extlinux entry \'%s\" on %s",
+					 e->label, rootpath);
+	e->entry.me.type = MENU_ENTRY_NORMAL;
+
+	bootentries_add_entry(bootentries, &e->entry);
+
+	return 1;
+}
+
+static int extlinux_scan_directory(struct bootscanner *scanner,
+				   struct bootentries *bootentries,
+				   const char *rootpath)
+{
+	char *path;
+	struct stat s;
+	int ret;
+
+	path = basprintf("%s/boot/extlinux/extlinux.conf", rootpath);
+
+	ret = stat(path, &s);
+	if (!ret && S_ISREG(s.st_mode))
+		ret = extlinux_scan_file(scanner, bootentries, path);
+
+	free(path);
+
+	return ret < 1 ? ret : 1;
+}
+
+static struct bootscanner extlinux_scanner = {
+	.name = "extlinux",
+	.scan_file = extlinux_scan_file,
+	.scan_directory = extlinux_scan_directory,
+};
+
+static int extlinux_generate(struct bootentries *bootentries, const char *name)
+{
+	return bootentry_scan_generate(&extlinux_scanner, bootentries, name);
+}
+
+static struct bootentry_provider extlinux_provider = {
+	.name = "extlinux",
+	.generate = extlinux_generate,
+};
+
+static int extlinux_init(void)
+{
+	return bootentry_register_provider(&extlinux_provider);
+}
+device_initcall(extlinux_init);
-- 
2.52.0

[PATCH 2/2] Documentation: add extlinux.conf support description

[Alexander Shiyan]

Signed-off-by: Alexander Shiyan <eagle.alexander923@gmail.com>
---
 Documentation/user/booting-linux.rst | 38 ++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/Documentation/user/booting-linux.rst b/Documentation/user/booting-linux.rst
index ed1ec3f68a..307f33bb22 100644
--- a/Documentation/user/booting-linux.rst
+++ b/Documentation/user/booting-linux.rst
@@ -306,6 +306,44 @@ Additional notes about keys in the bootloader spec entries:
    different devices without having to specify a different ``root=`` option each
    time.
 
+.. _extlinux_conf:
+
+extlinux.conf Support
+^^^^^^^^^^^^^^^^^^^^^
+
+In addition to the Boot Loader Specification, barebox also supports the
+extlinux configuration format, commonly used by the Syslinux bootloader and
+many Linux distributions. This format is often found on SD cards, USB drives,
+or disk partitions prepared with tools like ``extlinux --install``.
+
+The configuration file is named ``extlinux.conf`` and can be located at:
+* ``/boot/extlinux/extlinux.conf``
+
+The file uses a simple key-value syntax with sections labeled by ``LABEL``.
+A typical example looks like:
+
+.. code-block:: none
+
+  DEFAULT linux
+  LABEL linux
+    KERNEL /boot/vmlinuz
+    INITRD /boot/initrd.img
+    FDT /boot/board.dtb
+    APPEND console=ttyS0,115200 root=PARTUUID=deadbeef-01
+
+When booting an extlinux entry, barebox automatically strips any ``root=``
+parameter from the ``APPEND`` line and injects the correct ``root=`` based on
+the boot device (similar to the ``linux-appendroot`` feature in blspec). This
+makes the same root filesystem image usable across different storage media.
+
+To use extlinux support, enable ``CONFIG_EXTLINUX`` in your barebox
+configuration. Entries are automatically discovered by the :ref:`command_boot`
+command when scanning a device or mount point. For example:
+
+.. code-block:: sh
+
+  boot mmc1.2
+
 .. _booting_linux_net:
 
 Network boot
-- 
2.52.0

Re: [PATCH 2/2] Documentation: add extlinux.conf support description

[Ahmad Fatoum]

Hi,

On 4/16/26 3:45 PM, Alexander Shiyan wrote:
> Signed-off-by: Alexander Shiyan <eagle.alexander923@gmail.com>

Thanks for adding documentation.

I have been wanting to add bootloader spec support to openembedded-core
to barebox can be used to boot Beaglebone black images generated by it,
but with extlinux support in barebox that should work as well.
I will surely give this a try in the future.

Could I motivate you to add a self test that exercises the parser?

Doesn't have to be anything extensive, see test/self/blspec.c for an
example. It's basically adding a few configs into the barebox
environment, calling bootentry_create_from_name() on the directory and
then running some assertions.

Thanks,
Ahmad

> ---
>  Documentation/user/booting-linux.rst | 38 ++++++++++++++++++++++++++++
>  1 file changed, 38 insertions(+)
> 
> diff --git a/Documentation/user/booting-linux.rst b/Documentation/user/booting-linux.rst
> index ed1ec3f68a..307f33bb22 100644
> --- a/Documentation/user/booting-linux.rst
> +++ b/Documentation/user/booting-linux.rst
> @@ -306,6 +306,44 @@ Additional notes about keys in the bootloader spec entries:
>     different devices without having to specify a different ``root=`` option each
>     time.
>  
> +.. _extlinux_conf:
> +
> +extlinux.conf Support
> +^^^^^^^^^^^^^^^^^^^^^
> +
> +In addition to the Boot Loader Specification, barebox also supports the
> +extlinux configuration format, commonly used by the Syslinux bootloader and
> +many Linux distributions. This format is often found on SD cards, USB drives,
> +or disk partitions prepared with tools like ``extlinux --install``.
> +
> +The configuration file is named ``extlinux.conf`` and can be located at:
> +* ``/boot/extlinux/extlinux.conf``
> +
> +The file uses a simple key-value syntax with sections labeled by ``LABEL``.
> +A typical example looks like:
> +
> +.. code-block:: none
> +
> +  DEFAULT linux
> +  LABEL linux
> +    KERNEL /boot/vmlinuz
> +    INITRD /boot/initrd.img
> +    FDT /boot/board.dtb
> +    APPEND console=ttyS0,115200 root=PARTUUID=deadbeef-01
> +
> +When booting an extlinux entry, barebox automatically strips any ``root=``
> +parameter from the ``APPEND`` line and injects the correct ``root=`` based on
> +the boot device (similar to the ``linux-appendroot`` feature in blspec). This
> +makes the same root filesystem image usable across different storage media.
> +
> +To use extlinux support, enable ``CONFIG_EXTLINUX`` in your barebox
> +configuration. Entries are automatically discovered by the :ref:`command_boot`
> +command when scanning a device or mount point. For example:
> +
> +.. code-block:: sh
> +
> +  boot mmc1.2
> +
>  .. _booting_linux_net:
>  
>  Network boot

-- 
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Steuerwalder Str. 21              | http://www.pengutronix.de/  |
31137 Hildesheim, Germany         | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686  | Fax:   +49-5121-206917-5555 |

Re: [PATCH 2/2] Documentation: add extlinux.conf support description

[Alexander Shiyan]

Hello Ahmad.

> On 4/16/26 3:45 PM, Alexander Shiyan wrote:
> > Signed-off-by: Alexander Shiyan <eagle.alexander923@gmail.com>
>
> Thanks for adding documentation.
>
> I have been wanting to add bootloader spec support to openembedded-core
> to barebox can be used to boot Beaglebone black images generated by it,
> but with extlinux support in barebox that should work as well.
> I will surely give this a try in the future.
>
> Could I motivate you to add a self test that exercises the parser?
>
> Doesn't have to be anything extensive, see test/self/blspec.c for an
> example. It's basically adding a few configs into the barebox
> environment, calling bootentry_create_from_name() on the directory and
> then running some assertions.

I think this can be done later, so as not to bloat the patch series...

Re: [PATCH 1/2] Add support for extlinux.conf

[Ahmad Fatoum]

Hi Alexander,

Thanks for your patch!

On 4/16/26 3:45 PM, Alexander Shiyan wrote:
> This adds support for the extlinux.conf configuration format, commonly
> used by Syslinux and many Linux distributions. The configuration file
> is typically located at /boot/extlinux/extlinux.conf or
> /extlinux/extlinux.conf and defines boot entries with kernel, initrd,
> device tree, and command line options.
> 
> The implementation integrates with the existing boot entry framework:
> - The extlinux scanner discovers entries on mounted filesystems
> - Default label is turned into a boot entry
> - The "root=" parameter is automatically stripped from the append line
>   to allow barebox to inject the correct root device (via appendroot)
> - Bootm is used to load and start the kernel
> ---
> barebox@Diasom DS-RK3568-SOM-EVB:/ global.boot.default=mmc1.2
> barebox@Diasom DS-RK3568-SOM-EVB:/ boot
> ext4 ext40: EXT2 rev 1, inode_size 256, descriptor size 64
> Booting entry 'extlinux: linux'
> extlinux: Booting extlinux label 'linux'
> Adding "root=/dev/mmcblk1p3" to Kernel commandline
> Loading ARM aarch64 Linux/EFI image '/mnt/mmc1.2/boot/extlinux/../vmlinuz'
> Loaded initrd from GZIP compressed /mnt/mmc1.2/boot/extlinux/../initrd.img to 0x000000000d390000-0x000000000fb48ca6
> commandline: mem=0xef600000 root=/dev/mmcblk1p3 console=ttyS2,1500000n8 ro systemd.unit=setup.target quiet splash  systemd.machine_id=181af2816b4c6b0aef77068e0ccc69ad
> Loaded kernel to 0x0a400000, devicetree at 0x000000000fb49000
> 
> Signed-off-by: Alexander Shiyan <eagle.alexander923@gmail.com>
> ---
>  common/Kconfig    |  19 ++++
>  common/Makefile   |   1 +
>  common/extlinux.c | 271 ++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 291 insertions(+)
>  create mode 100644 common/extlinux.c
> 
> diff --git a/common/Kconfig b/common/Kconfig
> index cd002865f7..bbffbfe92c 100644
> --- a/common/Kconfig
> +++ b/common/Kconfig
> @@ -726,6 +726,25 @@ config BLSPEC
>  	  on a device and it allows the Operating System to install / update
>  	  kernels.
>  
> +config EXTLINUX
> +	bool
> +	prompt "Support extlinux.conf"
> +	depends on FLEXIBLE_BOOTARGS
> +	depends on !SHELL_NONE
> +	select BOOT
> +	select BOOTM
> +	select MMCBLKDEV_ROOTARG if MCI
> +	help
> +	  Enable this to let barebox parse extlinux.conf configuration files,
> +	  commonly used by the Syslinux bootloader and many Linux distributions
> +	  (e.g., on SD cards or USB drives).
> +	  extlinux.conf is typically located at /boot/extlinux/extlinux.conf or
> +	  /extlinux/extlinux.conf. It defines boot entries with kernel, initrd,
> +	  device tree, and command line options.
> +	  This option allows barebox to discover and boot operating systems
> +	  that follow the extlinux configuration format, providing a simple
> +	  and portable way to manage multiple boot options.
> +
>  config FLEXIBLE_BOOTARGS
>  	bool
>  	prompt "flexible Linux bootargs generation"
> diff --git a/common/Makefile b/common/Makefile
> index ac39ee4e3e..dda42c099a 100644
> --- a/common/Makefile
> +++ b/common/Makefile
> @@ -9,6 +9,7 @@ obj-y				+= clock.o
>  pbl-$(CONFIG_PBL_CLOCKSOURCE)	+= clock.o
>  obj-y				+= console_common.o
>  obj-$(CONFIG_OFDEVICE)		+= deep-probe.o
> +obj-$(CONFIG_EXTLINUX)		+= extlinux.o
>  obj-y				+= startup.o
>  obj-y				+= misc.o
>  obj-pbl-y			+= memsize.o
> diff --git a/common/extlinux.c b/common/extlinux.c
> new file mode 100644
> index 0000000000..39d5191ecc
> --- /dev/null
> +++ b/common/extlinux.c
> @@ -0,0 +1,271 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/* SPDX-FileCopyrightText: Alexander Shiyan <shc_work@mail.ru> */
> +
> +#define pr_fmt(fmt)     "extlinux: " fmt
> +
> +#include <boot.h>
> +#include <bootm.h>
> +#include <bootscan.h>
> +#include <common.h>
> +#include <environment.h>
> +#include <fs.h>
> +#include <globalvar.h>
> +#include <libfile.h>
> +#include <libgen.h>
> +#include <malloc.h>
> +#include <string.h>
> +
> +struct extlinux_entry {
> +	struct bootentry entry;
> +	char *rootpath;
> +	char *label;
> +	char *kernel;
> +	char *initrd;
> +	char *fdtdir;
> +	char *fdt;
> +	char *append;
> +};
> +
> +static int extlinux_boot(struct bootentry *be, int verbose, int dryrun)
> +{
> +	struct extlinux_entry *e =
> +		container_of(be, struct extlinux_entry, entry);
> +	char *kernel_abs, *initrd_abs = NULL, *fdt_abs = NULL;
> +	struct bootm_data data = {};
> +	int ret;
> +
> +	bootm_data_init_defaults(&data);
> +
> +	data.dryrun = max_t(int, dryrun, data.dryrun);
> +	data.verbose = max(verbose, data.verbose);
> +	data.appendroot = true;

Not sure this is a good idea because of potential of clashing with
extlinux appended command line options.

> +
> +	kernel_abs = basprintf("%s/%s", e->rootpath, e->kernel);
> +	data.os_file = kernel_abs;
> +
> +	if (e->initrd) {
> +		initrd_abs = basprintf("%s/%s", e->rootpath, e->initrd);
> +		data.initrd_file = initrd_abs;
> +	}
> +
> +	if (e->fdt) {
> +		char *fdtdir = e->fdtdir ? : e->rootpath;
> +
> +		fdt_abs = basprintf("%s/%s", fdtdir, e->fdt);
> +		data.oftree_file = fdt_abs;
> +	}
> +
> +	if (e->append)
> +		globalvar_add_simple("linux.bootargs.dyn.extlinux", e->append);
> +
> +	pr_info("Booting extlinux label '%s'\n", e->label);
> +
> +	ret = bootm_boot(&data);

Please make use of new bootm_entry instead, so it can be used with devboot:

https://github.com/barebox/barebox/blob/next/Documentation/user/devboot.rst

> +	if (ret)
> +		pr_err("bootm failed: %s\n", strerror(-ret));
> +
> +	free(kernel_abs);
> +	free(initrd_abs);
> +	free(fdt_abs);
> +
> +	return ret;
> +}
> +
> +static void extlinux_entry_free(struct bootentry *be)
> +{
> +	struct extlinux_entry *e =
> +		container_of(be, struct extlinux_entry, entry);
> +
> +	free(e->rootpath);
> +	free(e->label);
> +	free(e->kernel);
> +	free(e->initrd);
> +	free(e->fdtdir);
> +	free(e->fdt);
> +	free(e->append);
> +	free(e);
> +}
> +
> +static char *remove_param(const char *params, const char *param)
> +{
> +	char *result, *dst;
> +	const char *src;
> +
> +	result = xmalloc(strlen(params) + 1);
> +
> +	src = params;
> +	dst = result;
> +
> +	while (*src) {
> +		if (!strncasecmp(src, param, strlen(param))) {
> +			while (*src && *src != ' ')
> +				src++;
> +
> +			src = skip_spaces(src);
> +
> +			continue;
> +		}
> +
> +		*dst++ = *src++;
> +	}
> +
> +	*dst = '\0';
> +
> +	return result;
> +}
> +
> +static struct extlinux_entry *parse_extlinux_conf(const char *abspath,
> +						  const char *rootpath)
> +{
> +	char *buf, *bufptr, *line, *p, *default_label = NULL;
> +	struct extlinux_entry *entry = NULL;
> +
> +	bufptr = read_file(abspath, NULL);
> +	if (!bufptr)
> +		return ERR_PTR(-errno);
> +
> +	for (p = bufptr; *p; p++)
> +		if (*p == '\r')
> +			*p = '\n';

I think this can be dropped.

> +
> +	buf = bufptr;
> +	while ((line = strsep(&buf, "\n")) != NULL) {

And then you replace the set searched here with "\r\n"

> +		char *key, *val;
> +
> +		line = skip_spaces(line);
> +
> +		if (*line == '#' || *line == '\0')
> +			continue;
> +

Nitpick: I think below can be simplified to:

> +		key = line;
> +		val = strchr(line, ' ');
> +		if (!val)
> +			val = strchr(line, '\t');
> +		if (val) {
> +			*val++ = '\0';
> +			val = skip_spaces(val);
> +		} else
> +			continue;

key = strsep(&line, ' \t');
val = strsep(&line, '\n');
val = isempty(val) ? NULL : skip_spaces(val);



> +
> +		if (!default_label) {
> +			if (!strcasecmp(key, "DEFAULT"))
> +				default_label = xstrdup(val);
> +
> +			continue;
> +		}
> +
> +		if (!strcasecmp(key, "LABEL")) {
> +			if (!strcmp(val, default_label)) {

defaut_label might not have been set here?

You can use streq_ptr which includes NULL pointer checks.

> +				entry = xzalloc(sizeof(*entry));
> +				entry->label = xstrdup(val);
> +				entry->rootpath = dirname(xstrdup(abspath));
> +			} else if (entry)
> +				break;

Kernel coding style is keeping the { braces } for an else when the if
has some.

> +			continue;
> +		}
> +
> +		/*
> +		 * The same rootfs image may be launched from eMMC or SD card.
> +		 * Remove any hardcoded root= parameter from "append" to avoid
> +		 * conflicts, then let barebox automatically add the correct
> +		 * root= (via appendroot) based on the boot device.
> +		 */

I understand the thought process, but this feels very invasive. What if
the extlinux.conf files are on a different partition? I think that's not
too uncommon for systems that have a ROM-code mandated FAT partition anyway.

At the very least, make this dependent on a parameter being set, maybe
just global.bootm.appendroot?

> +		if (entry) {
> +			if (!strcasecmp(key, "KERNEL"))
> +				entry->kernel = xstrdup(val);
> +			else if (!strcasecmp(key, "INITRD"))
> +				entry->initrd = xstrdup(val);
> +			else if (!strcasecmp(key, "FDTDIR"))
> +				entry->fdtdir = xstrdup(val);
> +			else if (!strcasecmp(key, "FDT"))
> +				entry->fdt = xstrdup(val);
> +			else if (!strcasecmp(key, "APPEND"))
> +				entry->append = remove_param(val, "ROOT=");
> +			else
> +				pr_debug("Unhandled key: %s\n", key);

I would make this a pr_warn or at least a pr_info, so new users have an
easier time knowing why something doesn't work.

> +		}
> +	}
> +
> +	free(default_label);
> +	free(bufptr);
> +
> +	if (!entry || !entry->kernel) {
> +		if (entry)
> +			extlinux_entry_free(&entry->entry);
> +		return ERR_PTR(-EINVAL);
> +	}
> +
> +	return entry;
> +}
> +
> +static int extlinux_scan_file(struct bootscanner *scanner,
> +			      struct bootentries *bootentries,
> +			      const char *configname)
> +{
> +	struct extlinux_entry *e;
> +	const char *rootpath;
> +
> +	if (!strends(configname, "extlinux.conf"))
> +		return 0;
> +
> +	rootpath = get_mounted_path(configname);
> +	if (IS_ERR(rootpath))
> +		return PTR_ERR(rootpath);

This means you don't support this file existing at a subdirectory of a
mountpoint. That can be useful though if one is using ostree or if we
include extlinux.conf files in the environment for testing.

Please add an intermediate __extlinux_scan_file that takes rootpath, see
how blspec does it.

> +
> +	e = parse_extlinux_conf(configname, rootpath);
> +	if (IS_ERR(e))
> +		return PTR_ERR(e);
> +
> +	e->entry.boot = extlinux_boot;
> +	e->entry.release = extlinux_entry_free;
> +	e->entry.path = xstrdup(configname);

xstrdup_const

> +	e->entry.title = basprintf("extlinux: %s", e->label);
> +	e->entry.description = basprintf("extlinux entry \'%s\" on %s",
> +					 e->label, rootpath);
> +	e->entry.me.type = MENU_ENTRY_NORMAL;
> +
> +	bootentries_add_entry(bootentries, &e->entry);
> +
> +	return 1;
> +}
> +
> +static int extlinux_scan_directory(struct bootscanner *scanner,
> +				   struct bootentries *bootentries,
> +				   const char *rootpath)
> +{
> +	char *path;
> +	struct stat s;
> +	int ret;
> +
> +	path = basprintf("%s/boot/extlinux/extlinux.conf", rootpath);

You mention both /boot/extlinux/extlinux and /extlinux/extlinux
as directory, but you only check one of them here.

Should you not check the second one as well?

> +	ret = stat(path, &s);
> +	if (!ret && S_ISREG(s.st_mode))

A extlinux.conf _directory_ is silently skipped by this. Intentional?

> +		ret = extlinux_scan_file(scanner, bootentries, path);

You should pass along rootpath here.

> +
> +	free(path);
> +
> +	return ret < 1 ? ret : 1;

This can be simplified to return ret;

> +}
> +
> +static struct bootscanner extlinux_scanner = {
> +	.name = "extlinux",
> +	.scan_file = extlinux_scan_file,
> +	.scan_directory = extlinux_scan_directory,

This implements

boot -l /mnt/mmc0.1/boot/extlinux/extlinux.conf
boot -l /mnt/mmc0.1/

and leaves the rest to the core.
I think that's fine, but can you check if the following work:

boot -l mmc0
boot -l /dev/mmc0
boot -l mmc0.1
boot -l /dev/mmc0.1

> +};
> +
> +static int extlinux_generate(struct bootentries *bootentries, const char *name)
> +{
> +	return bootentry_scan_generate(&extlinux_scanner, bootentries, name);
> +}
> +
> +static struct bootentry_provider extlinux_provider = {
> +	.name = "extlinux",
> +	.generate = extlinux_generate,

You need to set a negative priority here, so existing bootloader spec
support wins if both are available.

I think .priority = -25 is ok, so it's in-between blspec and efiboomgr.

> +};
> +
> +static int extlinux_init(void)
> +{
> +	return bootentry_register_provider(&extlinux_provider);
> +}
> +device_initcall(extlinux_init);


Thanks,
Ahmad

-- 
Pengutronix e.K.                  |                             |
Steuerwalder Str. 21              | http://www.pengutronix.de/  |
31137 Hildesheim, Germany         | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686  | Fax:   +49-5121-206917-5555 |

Re: [PATCH 1/2] Add support for extlinux.conf

[Alexander Shiyan]

Hello Ahmad.

> Thanks for your patch!
>
> On 4/16/26 3:45 PM, Alexander Shiyan wrote:
> > This adds support for the extlinux.conf configuration format, commonly
> > used by Syslinux and many Linux distributions. The configuration file
> > is typically located at /boot/extlinux/extlinux.conf or
> > /extlinux/extlinux.conf and defines boot entries with kernel, initrd,
> > device tree, and command line options.
...
> > +static int extlinux_boot(struct bootentry *be, int verbose, int dryrun)
> > +{
> > +     struct extlinux_entry *e =
> > +             container_of(be, struct extlinux_entry, entry);
> > +     char *kernel_abs, *initrd_abs = NULL, *fdt_abs = NULL;
> > +     struct bootm_data data = {};
> > +     int ret;
> > +
> > +     bootm_data_init_defaults(&data);
> > +
> > +     data.dryrun = max_t(int, dryrun, data.dryrun);
> > +     data.verbose = max(verbose, data.verbose);
> > +     data.appendroot = true;
>
> Not sure this is a good idea because of potential of clashing with
> extlinux appended command line options.

globalvar_add_bool("extlinux.fix_root", NULL); ?

...
> > +     if (e->append)
> > +             globalvar_add_simple("linux.bootargs.dyn.extlinux", e->append);
> > +
> > +     pr_info("Booting extlinux label '%s'\n", e->label);
> > +
> > +     ret = bootm_boot(&data);
>
> Please make use of new bootm_entry instead, so it can be used with devboot:
>
> https://github.com/barebox/barebox/blob/next/Documentation/user/devboot.rst

I haven't figured out how to do this yet...

...
> > +static struct extlinux_entry *parse_extlinux_conf(const char *abspath,
> > +                                               const char *rootpath)
> > +{
> > +     char *buf, *bufptr, *line, *p, *default_label = NULL;
> > +     struct extlinux_entry *entry = NULL;
> > +
> > +     bufptr = read_file(abspath, NULL);
> > +     if (!bufptr)
> > +             return ERR_PTR(-errno);
> > +
> > +     for (p = bufptr; *p; p++)
> > +             if (*p == '\r')
> > +                     *p = '\n';
>
> I think this can be dropped.
>
> > +
> > +     buf = bufptr;
> > +     while ((line = strsep(&buf, "\n")) != NULL) {
>
> And then you replace the set searched here with "\r\n"

The end of the line may be \n, \r, \n\r.
We are simply converting it to a uniform format.

> > +             char *key, *val;
> > +
> > +             line = skip_spaces(line);
> > +
> > +             if (*line == '#' || *line == '\0')
> > +                     continue;
> > +
>
> Nitpick: I think below can be simplified to:
>
> > +             key = line;
> > +             val = strchr(line, ' ');
> > +             if (!val)
> > +                     val = strchr(line, '\t');
> > +             if (val) {
> > +                     *val++ = '\0';
> > +                     val = skip_spaces(val);
> > +             } else
> > +                     continue;
>
> key = strsep(&line, ' \t');
> val = strsep(&line, '\n');
> val = isempty(val) ? NULL : skip_spaces(val);

strsep inserts a null byte in place of the separator; this will
corrupt the buffer,
and consequently, we will not be able to find the val.

> > +
> > +             if (!default_label) {
> > +                     if (!strcasecmp(key, "DEFAULT"))
> > +                             default_label = xstrdup(val);
> > +
> > +                     continue;
> > +             }
> > +
> > +             if (!strcasecmp(key, "LABEL")) {
> > +                     if (!strcmp(val, default_label)) {
>
> defaut_label might not have been set here?

No: if (!default_label) ... continue;

Re: [PATCH 1/2] Add support for extlinux.conf

[Ahmad Fatoum]

Hello,

On 4/24/26 10:46 AM, Alexander Shiyan wrote:
>> On 4/16/26 3:45 PM, Alexander Shiyan wrote:
>>> This adds support for the extlinux.conf configuration format, commonly
>>> used by Syslinux and many Linux distributions. The configuration file
>>> is typically located at /boot/extlinux/extlinux.conf or
>>> /extlinux/extlinux.conf and defines boot entries with kernel, initrd,
>>> device tree, and command line options.
> ...
>>> +static int extlinux_boot(struct bootentry *be, int verbose, int dryrun)
>>> +{
>>> +     struct extlinux_entry *e =
>>> +             container_of(be, struct extlinux_entry, entry);
>>> +     char *kernel_abs, *initrd_abs = NULL, *fdt_abs = NULL;
>>> +     struct bootm_data data = {};
>>> +     int ret;
>>> +
>>> +     bootm_data_init_defaults(&data);
>>> +
>>> +     data.dryrun = max_t(int, dryrun, data.dryrun);
>>> +     data.verbose = max(verbose, data.verbose);
>>> +     data.appendroot = true;
>>
>> Not sure this is a good idea because of potential of clashing with
>> extlinux appended command line options.
> 
> globalvar_add_bool("extlinux.fix_root", NULL); ?

global.extlinux.strip_root to remove root=
and bootm.appendroot to add barebox' own root?

@Sascha, any thoughts on this?

> 
> ...
>>> +     if (e->append)
>>> +             globalvar_add_simple("linux.bootargs.dyn.extlinux", e->append);
>>> +
>>> +     pr_info("Booting extlinux label '%s'\n", e->label);
>>> +
>>> +     ret = bootm_boot(&data);
>>
>> Please make use of new bootm_entry instead, so it can be used with devboot:
>>
>> https://github.com/barebox/barebox/blob/next/Documentation/user/devboot.rst
> 
> I haven't figured out how to do this yet...

Just make sure it can be used by calling bootm_entry instead of bootm_boot.


> ...
>>> +static struct extlinux_entry *parse_extlinux_conf(const char *abspath,
>>> +                                               const char *rootpath)
>>> +{
>>> +     char *buf, *bufptr, *line, *p, *default_label = NULL;
>>> +     struct extlinux_entry *entry = NULL;
>>> +
>>> +     bufptr = read_file(abspath, NULL);
>>> +     if (!bufptr)
>>> +             return ERR_PTR(-errno);
>>> +
>>> +     for (p = bufptr; *p; p++)
>>> +             if (*p == '\r')
>>> +                     *p = '\n';
>>
>> I think this can be dropped.
>>
>>> +
>>> +     buf = bufptr;
>>> +     while ((line = strsep(&buf, "\n")) != NULL) {
>>
>> And then you replace the set searched here with "\r\n"
> 
> The end of the line may be \n, \r, \n\r.
> We are simply converting it to a uniform format.

strsep's second argument means split at any of these characters and not
split at them in exactly that order.

> 
>>> +             char *key, *val;
>>> +
>>> +             line = skip_spaces(line);
>>> +
>>> +             if (*line == '#' || *line == '\0')
>>> +                     continue;
>>> +
>>
>> Nitpick: I think below can be simplified to:
>>
>>> +             key = line;
>>> +             val = strchr(line, ' ');
>>> +             if (!val)
>>> +                     val = strchr(line, '\t');
>>> +             if (val) {
>>> +                     *val++ = '\0';
>>> +                     val = skip_spaces(val);
>>> +             } else
>>> +                     continue;
>>
>> key = strsep(&line, ' \t');
>> val = strsep(&line, '\n');
>> val = isempty(val) ? NULL : skip_spaces(val);
> 
> strsep inserts a null byte in place of the separator; this will
> corrupt the buffer,
> and consequently, we will not be able to find the val.

char line[] = "DEFAULT test", *p = line;

char *key = strsep(&p, " \t");
char *val = strsep(&p, "\n");

printf("key<%s> value<%s>\n", key, val);

prints key<DEFAULT> value<test>.
Isn't that exactly what you need?

>> defaut_label might not have been set here?
> 
> No: if (!default_label) ... continue;

Ah ok.

Cheers,
Ahmad

-- 
Pengutronix e.K.                  |                             |
Steuerwalder Str. 21              | http://www.pengutronix.de/  |
31137 Hildesheim, Germany         | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686  | Fax:   +49-5121-206917-5555 |

Re: [PATCH 1/2] Add support for extlinux.conf

[Sascha Hauer]

On Fri, Apr 24, 2026 at 04:53:59PM +0200, Ahmad Fatoum wrote:
> Hello,
> 
> On 4/24/26 10:46 AM, Alexander Shiyan wrote:
> >> On 4/16/26 3:45 PM, Alexander Shiyan wrote:
> >>> This adds support for the extlinux.conf configuration format, commonly
> >>> used by Syslinux and many Linux distributions. The configuration file
> >>> is typically located at /boot/extlinux/extlinux.conf or
> >>> /extlinux/extlinux.conf and defines boot entries with kernel, initrd,
> >>> device tree, and command line options.
> > ...
> >>> +static int extlinux_boot(struct bootentry *be, int verbose, int dryrun)
> >>> +{
> >>> +     struct extlinux_entry *e =
> >>> +             container_of(be, struct extlinux_entry, entry);
> >>> +     char *kernel_abs, *initrd_abs = NULL, *fdt_abs = NULL;
> >>> +     struct bootm_data data = {};
> >>> +     int ret;
> >>> +
> >>> +     bootm_data_init_defaults(&data);
> >>> +
> >>> +     data.dryrun = max_t(int, dryrun, data.dryrun);
> >>> +     data.verbose = max(verbose, data.verbose);
> >>> +     data.appendroot = true;
> >>
> >> Not sure this is a good idea because of potential of clashing with
> >> extlinux appended command line options.
> > 
> > globalvar_add_bool("extlinux.fix_root", NULL); ?
> 
> global.extlinux.strip_root to remove root=
> and bootm.appendroot to add barebox' own root?

We already have the latter, so nothing to do here.

Shouldn't we by default remove the root= option once data->appendroot is
set? Also in the bootspec case we do not want to end up with two root=
options.

Sascha

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

Re: [PATCH 1/2] Add support for extlinux.conf

[Alexander Shiyan]

Hello, Sasha.

...
> > >>> This adds support for the extlinux.conf configuration format, commonly
> > >>> used by Syslinux and many Linux distributions. The configuration file
> > >>> is typically located at /boot/extlinux/extlinux.conf or
> > >>> /extlinux/extlinux.conf and defines boot entries with kernel, initrd,
> > >>> device tree, and command line options.
> > > ...
> > >>> +static int extlinux_boot(struct bootentry *be, int verbose, int dryrun)
> > >>> +{
> > >>> +     struct extlinux_entry *e =
> > >>> +             container_of(be, struct extlinux_entry, entry);
> > >>> +     char *kernel_abs, *initrd_abs = NULL, *fdt_abs = NULL;
> > >>> +     struct bootm_data data = {};
> > >>> +     int ret;
> > >>> +
> > >>> +     bootm_data_init_defaults(&data);
> > >>> +
> > >>> +     data.dryrun = max_t(int, dryrun, data.dryrun);
> > >>> +     data.verbose = max(verbose, data.verbose);
> > >>> +     data.appendroot = true;
> > >>
> > >> Not sure this is a good idea because of potential of clashing with
> > >> extlinux appended command line options.
> > >
> > > globalvar_add_bool("extlinux.fix_root", NULL); ?
> >
> > global.extlinux.strip_root to remove root=
> > and bootm.appendroot to add barebox' own root?
>
> We already have the latter, so nothing to do here.
>
> Shouldn't we by default remove the root= option once data->appendroot is
> set? Also in the bootspec case we do not want to end up with two root=
> options.

Is this method better?
I haven't tested it yet, but it goes something like this:

if (getenv_bool("bootm.appendroot", (int *)&data.appendroot))
data.appendroot = true;

if (e->append) {
/*
* The same rootfs image may be launched from eMMC or SD card.
* Remove any hardcoded root= parameter from "append" to avoid
* conflicts, then let barebox automatically add the correct
* root= (via appendroot) based on the boot device.
*/
if (data.appendroot) {
char *append = remove_param(e->append, "ROOT=");
free(e->append);
e->append = append;
}

globalvar_add_simple("linux.bootargs.dyn.extlinux", e->append);
}

Re: [PATCH 1/2] Add support for extlinux.conf

[Ahmad Fatoum]

Hello Sascha,

On 4/27/26 10:58 AM, Sascha Hauer wrote:
> On Fri, Apr 24, 2026 at 04:53:59PM +0200, Ahmad Fatoum wrote:
>> Hello,
>>
>> On 4/24/26 10:46 AM, Alexander Shiyan wrote:
>>>> On 4/16/26 3:45 PM, Alexander Shiyan wrote:
>>>>> This adds support for the extlinux.conf configuration format, commonly
>>>>> used by Syslinux and many Linux distributions. The configuration file
>>>>> is typically located at /boot/extlinux/extlinux.conf or
>>>>> /extlinux/extlinux.conf and defines boot entries with kernel, initrd,
>>>>> device tree, and command line options.
>>> ...
>>>>> +static int extlinux_boot(struct bootentry *be, int verbose, int dryrun)
>>>>> +{
>>>>> +     struct extlinux_entry *e =
>>>>> +             container_of(be, struct extlinux_entry, entry);
>>>>> +     char *kernel_abs, *initrd_abs = NULL, *fdt_abs = NULL;
>>>>> +     struct bootm_data data = {};
>>>>> +     int ret;
>>>>> +
>>>>> +     bootm_data_init_defaults(&data);
>>>>> +
>>>>> +     data.dryrun = max_t(int, dryrun, data.dryrun);
>>>>> +     data.verbose = max(verbose, data.verbose);
>>>>> +     data.appendroot = true;
>>>>
>>>> Not sure this is a good idea because of potential of clashing with
>>>> extlinux appended command line options.
>>>
>>> globalvar_add_bool("extlinux.fix_root", NULL); ?
>>
>> global.extlinux.strip_root to remove root=
>> and bootm.appendroot to add barebox' own root?
> 
> We already have the latter, so nothing to do here.
> 
> Shouldn't we by default remove the root= option once data->appendroot is
> set? Also in the bootspec case we do not want to end up with two root=
> options.

I think we can't get this to work properly anyhow. Besides root= there
are other options as well (e.g. rootfstype) that we won't be able to
exhaustively remove. Add on top of that, that an initrd may decide for
itself that another rootfs should be used anyway...

If a user knows for a given system that appending root= will work, they
can do that, but I think it's useful for the cases where it doesn't work
that there are two root='s, so the root appending is directly apparent.

We just need to ensure the appended root comes last, so it has precedence.

Cheers,
Ahmad

> 
> Sascha
> 

-- 
Pengutronix e.K.                  |                             |
Steuerwalder Str. 21              | http://www.pengutronix.de/  |
31137 Hildesheim, Germany         | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686  | Fax:   +49-5121-206917-5555 |