[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 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.                  |                             |
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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

-- 
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 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

[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);
}