Re: [PATCH 07/11] efi: payload: split image handling from legacy handover boot

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

On 10/6/25 6:15 AM, chalianis1@gmail.com wrote:
> From: Chali Anis <chalianis1@gmail.com>
> 
> The handover boot support is Linux-specific and can be disabled
> with CONFIG_EFI_HANDOVER_PROTOCOL. In preparation for adding a compliant
> boot method, move the handover-specific parts into their own file.
> 
> Signed-off-by: Ahmad Fatoum <a.fatoum@barebox.org>
> Signed-off-by: Chali Anis <chalianis1@gmail.com>

Reviewed-by: Ahmad Fatoum <a.fatoum@pengutronix.de>

> ---
>  efi/payload/Kconfig        |   5 +
>  efi/payload/Makefile       |   1 +
>  efi/payload/handover.c     | 154 +++++++++++++++++++++++++++++
>  efi/payload/image.c        | 192 +++++--------------------------------
>  efi/payload/image.h        |  14 +++
>  efi/payload/setup_header.h |  63 ++++++++++++
>  6 files changed, 260 insertions(+), 169 deletions(-)
>  create mode 100644 efi/payload/handover.c
>  create mode 100644 efi/payload/image.h
>  create mode 100644 efi/payload/setup_header.h
> 
> diff --git a/efi/payload/Kconfig b/efi/payload/Kconfig
> index a403acc81a93..d0a46704a6b9 100644
> --- a/efi/payload/Kconfig
> +++ b/efi/payload/Kconfig
> @@ -25,4 +25,9 @@ if EFI_PAYLOAD
>  config EFI_STUB
>  	def_bool HAVE_EFI_STUB
>  
> +config EFI_HANDOVER_PROTOCOL
> +	bool "EFI Handover protocol"
> +	default y
> +	depends on X86
> +
>  endif
> diff --git a/efi/payload/Makefile b/efi/payload/Makefile
> index 1250535302d3..d8b577bf3e23 100644
> --- a/efi/payload/Makefile
> +++ b/efi/payload/Makefile
> @@ -2,6 +2,7 @@
>  
>  obj-y += init.o
>  obj-y += image.o
> +obj-$(CONFIG_EFI_HANDOVER_PROTOCOL) += handover.o
>  obj-y += efi-initrd.o
>  obj-$(CONFIG_OFTREE) += fdt.o
>  bbenv-y += env-efi
> diff --git a/efi/payload/handover.c b/efi/payload/handover.c
> new file mode 100644
> index 000000000000..82f4cb4f5286
> --- /dev/null
> +++ b/efi/payload/handover.c
> @@ -0,0 +1,154 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * handover.c - legacy x86 EFI handover protocol
> + *
> + * Copyright (c) 2014 Sascha Hauer <s.hauer@pengutronix.de>, Pengutronix
> + */
> +
> +#define pr_fmt(fmt) "efi-handover: " fmt
> +
> +#include <clock.h>
> +#include <common.h>
> +#include <linux/sizes.h>
> +#include <linux/ktime.h>
> +#include <memory.h>
> +#include <command.h>
> +#include <magicvar.h>
> +#include <init.h>
> +#include <driver.h>
> +#include <io.h>
> +#include <efi.h>
> +#include <malloc.h>
> +#include <string.h>
> +#include <linux/err.h>
> +#include <boot.h>
> +#include <bootm.h>
> +#include <fs.h>
> +#include <libfile.h>
> +#include <binfmt.h>
> +#include <wchar.h>
> +#include <efi/efi-payload.h>
> +#include <efi/efi-device.h>
> +
> +#include "image.h"
> +#include "setup_header.h"
> +
> +static int efi_do_execute_image(enum filetype filetype, const char *file)
> +{
> +	efi_handle_t handle;
> +	struct efi_loaded_image *loaded_image;
> +	int ret;
> +
> +	ret = efi_load_image(file, &loaded_image, &handle);
> +	if (ret)
> +		return ret;
> +
> +	return efi_execute_image(handle, loaded_image, filetype);
> +}
> +
> +typedef void(*handover_fn)(void *image, struct efi_system_table *table,
> +			   struct x86_setup_header *header);
> +
> +static inline void linux_efi_handover(efi_handle_t handle,
> +				      struct x86_setup_header *header)
> +{
> +	handover_fn handover;
> +	uintptr_t addr;
> +
> +	addr = header->code32_start + header->handover_offset;
> +	if (IS_ENABLED(CONFIG_X86_64))
> +		addr += 512;
> +
> +	handover = efi_phys_to_virt(addr);
> +	handover(handle, efi_sys_table, header);
> +}
> +
> +static int do_bootm_efi(struct image_data *data)
> +{
> +	void *tmp;
> +	void *initrd = NULL;
> +	size_t size;
> +	efi_handle_t handle;
> +	int ret;
> +	const char *options;
> +	struct efi_loaded_image *loaded_image;
> +	struct x86_setup_header *image_header, *boot_header;
> +
> +	ret = efi_load_image(data->os_file, &loaded_image, &handle);
> +	if (ret)
> +		return ret;
> +
> +	image_header = (struct x86_setup_header *)loaded_image->image_base;
> +
> +	if (!is_x86_setup_header(image_header) ||
> +	    image_header->version < 0x20b ||
> +	    !image_header->relocatable_kernel) {
> +		pr_err("Not a valid kernel image!\n");
> +		BS->unload_image(handle);
> +		return -EINVAL;
> +	}
> +
> +	boot_header = xmalloc(0x4000);
> +	memset(boot_header, 0, 0x4000);
> +	memcpy(boot_header, image_header, sizeof(*image_header));
> +
> +	/* Refer to Linux kernel commit a27e292b8a54
> +	 * ("Documentation/x86/boot: Reserve type_of_loader=13 for barebox")
> +	 */
> +	boot_header->type_of_loader = 0x13;
> +
> +	if (data->initrd_file) {
> +		tmp = read_file(data->initrd_file, &size);
> +		initrd = xmemalign(PAGE_SIZE, PAGE_ALIGN(size));
> +		memcpy(initrd, tmp, size);
> +		memset(initrd + size, 0, PAGE_ALIGN(size) - size);
> +		free(tmp);
> +		boot_header->ramdisk_image = efi_virt_to_phys(initrd);
> +		boot_header->ramdisk_size = PAGE_ALIGN(size);
> +	}
> +
> +	options = linux_bootargs_get();
> +	if (options) {
> +		boot_header->cmd_line_ptr = efi_virt_to_phys(options);
> +		boot_header->cmdline_size = strlen(options);
> +	}
> +
> +	boot_header->code32_start = efi_virt_to_phys(loaded_image->image_base +
> +			(image_header->setup_sects+1) * 512);
> +
> +	if (bootm_verbose(data)) {
> +		printf("\nStarting kernel at 0x%p", loaded_image->image_base);
> +		if (data->initrd_file)
> +			printf(", initrd at 0x%08x",
> +			       boot_header->ramdisk_image);
> +		printf("...\n");
> +	}
> +
> +	if (data->dryrun) {
> +		BS->unload_image(handle);
> +		free(boot_header);
> +		free(initrd);
> +		return 0;
> +	}
> +
> +	efi_set_variable_usec("LoaderTimeExecUSec", &efi_systemd_vendor_guid,
> +			      ktime_to_us(ktime_get()));
> +
> +	shutdown_barebox();
> +	linux_efi_handover(handle, boot_header);
> +
> +	return 0;
> +}
> +
> +static struct image_handler efi_handle_tr = {
> +	.name = "EFI Application",
> +	.bootm = do_bootm_efi,
> +	.filetype = filetype_exe,
> +};
> +
> +static int efi_register_handover_handler(void)
> +{
> +	register_image_handler(&efi_handle_tr);
> +	return 0;
> +}
> +late_efi_initcall(efi_register_handover_handler);
> diff --git a/efi/payload/image.c b/efi/payload/image.c
> index 33c5e18dac27..ae7678188d84 100644
> --- a/efi/payload/image.c
> +++ b/efi/payload/image.c
> @@ -5,13 +5,12 @@
>   * Copyright (c) 2014 Sascha Hauer <s.hauer@pengutronix.de>, Pengutronix
>   */
>  
> +#define pr_fmt(fmt) "efi-image: " fmt
> +
>  #include <clock.h>
>  #include <common.h>
>  #include <linux/sizes.h>
> -#include <linux/ktime.h>
>  #include <memory.h>
> -#include <command.h>
> -#include <magicvar.h>
>  #include <init.h>
>  #include <driver.h>
>  #include <io.h>
> @@ -19,7 +18,7 @@
>  #include <malloc.h>
>  #include <string.h>
>  #include <linux/err.h>
> -#include <boot.h>
> +#include <bootargs.h>
>  #include <bootm.h>
>  #include <fs.h>
>  #include <libfile.h>
> @@ -28,54 +27,8 @@
>  #include <efi/efi-payload.h>
>  #include <efi/efi-device.h>
>  
> -struct linux_kernel_header {
> -	/* first sector of the image */
> -	uint8_t code1[0x0020];
> -	uint16_t cl_magic;		/**< Magic number 0xA33F */
> -	uint16_t cl_offset;		/**< The offset of command line */
> -	uint8_t code2[0x01F1 - 0x0020 - 2 - 2];
> -	uint8_t setup_sects;		/**< The size of the setup in sectors */
> -	uint16_t root_flags;		/**< If the root is mounted readonly */
> -	uint16_t syssize;		/**< obsolete */
> -	uint16_t swap_dev;		/**< obsolete */
> -	uint16_t ram_size;		/**< obsolete */
> -	uint16_t vid_mode;		/**< Video mode control */
> -	uint16_t root_dev;		/**< Default root device number */
> -	uint16_t boot_flag;		/**< 0xAA55 magic number */
> -
> -	/* second sector of the image */
> -	uint16_t jump;			/**< Jump instruction (this is code!) */
> -	uint32_t header;		/**< Magic signature "HdrS" */
> -	uint16_t version;		/**< Boot protocol version supported */
> -	uint32_t realmode_swtch;	/**< Boot loader hook */
> -	uint16_t start_sys;		/**< The load-low segment (obsolete) */
> -	uint16_t kernel_version;	/**< Points to kernel version string */
> -	uint8_t type_of_loader;		/**< Boot loader identifier */
> -	uint8_t loadflags;		/**< Boot protocol option flags */
> -	uint16_t setup_move_size;	/**< Move to high memory size */
> -	uint32_t code32_start;		/**< Boot loader hook */
> -	uint32_t ramdisk_image;		/**< initrd load address */
> -	uint32_t ramdisk_size;		/**< initrd size */
> -	uint32_t bootsect_kludge;	/**< obsolete */
> -	uint16_t heap_end_ptr;		/**< Free memory after setup end */
> -	uint8_t ext_loader_ver;		/**< boot loader's extension of the version number */
> -	uint8_t ext_loader_type;	/**< boot loader's extension of its type */
> -	uint32_t cmd_line_ptr;		/**< Points to the kernel command line */
> -	uint32_t initrd_addr_max;	/**< Highest address for initrd */
> -	uint32_t kernel_alignment;	/**< Alignment unit required by the kernel */
> -	uint8_t relocatable_kernel;	/** */
> -	uint8_t min_alignment;		/** */
> -	uint16_t xloadflags;		/** */
> -	uint32_t cmdline_size;		/** */
> -	uint32_t hardware_subarch;	/** */
> -	uint64_t hardware_subarch_data;	/** */
> -	uint32_t payload_offset;	/** */
> -	uint32_t payload_length;	/** */
> -	uint64_t setup_data;		/** */
> -	uint64_t pref_address;		/** */
> -	uint32_t init_size;		/** */
> -	uint32_t handover_offset;	/** */
> -} __attribute__ ((packed));
> +#include "image.h"
> +#include "setup_header.h"
>  
>  static void *efi_read_file(const char *file, size_t *size)
>  {
> @@ -85,10 +38,6 @@ static void *efi_read_file(const char *file, size_t *size)
>  	char *buf;
>  	ssize_t ret;
>  
> -	buf = read_file(file, size);
> -	if (buf || errno != ENOMEM)
> -		return buf;
> -
>  	ret = stat(file, &s);
>  	if (ret)
>  		return NULL;
> @@ -122,8 +71,8 @@ static void efi_free_file(void *_mem, size_t size)
>  		BS->free_pages(mem, DIV_ROUND_UP(size, EFI_PAGE_SIZE));
>  }
>  
> -static int efi_load_image(const char *file, struct efi_loaded_image **loaded_image,
> -		efi_handle_t *h)
> +int efi_load_image(const char *file, struct efi_loaded_image **loaded_image,
> +		   efi_handle_t *h)
>  {
>  	void *exe;
>  	size_t size;
> @@ -158,10 +107,7 @@ static int efi_load_image(const char *file, struct efi_loaded_image **loaded_ima
>  
>  static bool is_linux_image(enum filetype filetype, const void *base)
>  {
> -	const struct linux_kernel_header *hdr = base;
> -
> -	if (IS_ENABLED(CONFIG_X86) &&
> -	    hdr->boot_flag == 0xAA55 && hdr->header == 0x53726448)
> +	if (IS_ENABLED(CONFIG_X86) && is_x86_setup_header(base))
>  		return true;
>  
>  	if (IS_ENABLED(CONFIG_ARM64) &&
> @@ -171,18 +117,13 @@ static bool is_linux_image(enum filetype filetype, const void *base)
>  	return false;
>  }
>  
> -static int efi_execute_image(enum filetype filetype, const char *file)
> +int efi_execute_image(efi_handle_t handle,
> +		      struct efi_loaded_image *loaded_image,
> +		      enum filetype filetype)
>  {
> -	efi_handle_t handle;
> -	struct efi_loaded_image *loaded_image;
>  	efi_status_t efiret;
>  	const char *options;
>  	bool is_driver;
> -	int ret;
> -
> -	ret = efi_load_image(file, &loaded_image, &handle);
> -	if (ret)
> -		return ret;
>  
>  	is_driver = (loaded_image->image_code_type == EFI_BOOT_SERVICES_CODE) ||
>  		(loaded_image->image_code_type == EFI_RUNTIME_SERVICES_CODE);
> @@ -216,110 +157,17 @@ static int efi_execute_image(enum filetype filetype, const char *file)
>  	return -efi_errno(efiret);
>  }
>  
> -typedef void(*handover_fn)(void *image, struct efi_system_table *table,
> -		struct linux_kernel_header *header);
> -
> -static inline void linux_efi_handover(efi_handle_t handle,
> -		struct linux_kernel_header *header)
> -{
> -	handover_fn handover;
> -	uintptr_t addr;
> -
> -	addr = header->code32_start + header->handover_offset;
> -	if (IS_ENABLED(CONFIG_X86_64))
> -		addr += 512;
> -
> -	handover = efi_phys_to_virt(addr);
> -	handover(handle, efi_sys_table, header);
> -}
> -
> -static int do_bootm_efi(struct image_data *data)
> +static int efi_execute(struct binfmt_hook *b, char *file, int argc, char **argv)
>  {
> -	void *tmp;
> -	void *initrd = NULL;
> -	size_t size;
> +	struct efi_loaded_image *loaded_image;
>  	efi_handle_t handle;
>  	int ret;
> -	const char *options;
> -	struct efi_loaded_image *loaded_image;
> -	struct linux_kernel_header *image_header, *boot_header;
>  
> -	ret = efi_load_image(data->os_file, &loaded_image, &handle);
> +	ret = efi_load_image(file, &loaded_image, &handle);
>  	if (ret)
>  		return ret;
>  
> -	image_header = (struct linux_kernel_header *)loaded_image->image_base;
> -
> -	if (image_header->boot_flag != 0xAA55 ||
> -	    image_header->header != 0x53726448 ||
> -	    image_header->version < 0x20b ||
> -	    !image_header->relocatable_kernel) {
> -		pr_err("Not a valid kernel image!\n");
> -		BS->unload_image(handle);
> -		return -EINVAL;
> -	}
> -
> -	boot_header = xmalloc(0x4000);
> -	memset(boot_header, 0, 0x4000);
> -	memcpy(boot_header, image_header, sizeof(*image_header));
> -
> -	/* Refer to Linux kernel commit a27e292b8a54
> -	 * ("Documentation/x86/boot: Reserve type_of_loader=13 for barebox")
> -	 */
> -	boot_header->type_of_loader = 0x13;
> -
> -	if (data->initrd_file) {
> -		tmp = read_file(data->initrd_file, &size);
> -		initrd = xmemalign(PAGE_SIZE, PAGE_ALIGN(size));
> -		memcpy(initrd, tmp, size);
> -		memset(initrd + size, 0, PAGE_ALIGN(size) - size);
> -		free(tmp);
> -		boot_header->ramdisk_image = efi_virt_to_phys(initrd);
> -		boot_header->ramdisk_size = PAGE_ALIGN(size);
> -	}
> -
> -	options = linux_bootargs_get();
> -	if (options) {
> -		boot_header->cmd_line_ptr = efi_virt_to_phys(options);
> -		boot_header->cmdline_size = strlen(options);
> -	}
> -
> -	boot_header->code32_start = efi_virt_to_phys(loaded_image->image_base +
> -			(image_header->setup_sects+1) * 512);
> -
> -	if (bootm_verbose(data)) {
> -		printf("\nStarting kernel at 0x%p", loaded_image->image_base);
> -		if (data->initrd_file)
> -			printf(", initrd at 0x%08x",
> -			       boot_header->ramdisk_image);
> -		printf("...\n");
> -	}
> -
> -	if (data->dryrun) {
> -		BS->unload_image(handle);
> -		free(boot_header);
> -		free(initrd);
> -		return 0;
> -	}
> -
> -	efi_set_variable_usec("LoaderTimeExecUSec", &efi_systemd_vendor_guid,
> -			      ktime_to_us(ktime_get()));
> -
> -	shutdown_barebox();
> -	linux_efi_handover(handle, boot_header);
> -
> -	return 0;
> -}
> -
> -static struct image_handler efi_handle_tr = {
> -	.name = "EFI Application",
> -	.bootm = do_bootm_efi,
> -	.filetype = filetype_exe,
> -};
> -
> -static int efi_execute(struct binfmt_hook *b, char *file, int argc, char **argv)
> -{
> -	return efi_execute_image(b->type, file);
> +	return efi_execute_image(handle, loaded_image, b->type);
>  }
>  
>  static struct binfmt_hook binfmt_efi_hook = {
> @@ -352,13 +200,19 @@ static struct binfmt_hook binfmt_arm64_efi_hook = {
>  	.hook = efi_execute,
>  };
>  
> +static struct binfmt_hook binfmt_x86_efi_hook = {
> +	.type = filetype_x86_linux_image,
> +	.hook = efi_execute,
> +};
> +
>  static int efi_register_image_handler(void)
>  {
> -	register_image_handler(&efi_handle_tr);
>  	binfmt_register(&binfmt_efi_hook);
>  
> -	if (IS_ENABLED(CONFIG_X86))
> +	if (IS_ENABLED(CONFIG_X86)) {
>  		register_image_handler(&non_efi_handle_linux_x86);
> +		binfmt_register(&binfmt_x86_efi_hook);
> +	}
>  
>  	if (IS_ENABLED(CONFIG_ARM64))
>  		binfmt_register(&binfmt_arm64_efi_hook);
> diff --git a/efi/payload/image.h b/efi/payload/image.h
> new file mode 100644
> index 000000000000..673b21db839a
> --- /dev/null
> +++ b/efi/payload/image.h
> @@ -0,0 +1,14 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +#ifndef __EFI_PAYLOAD_IMAGE_H__
> +#define __EFI_PAYLOAD_IMAGE_H__
> +
> +#include <efi/types.h>
> +
> +int efi_load_image(const char *file, struct efi_loaded_image **loaded_image,
> +		   efi_handle_t *h);
> +
> +int efi_execute_image(efi_handle_t handle,
> +		      struct efi_loaded_image *loaded_image,
> +		      enum filetype filetype);
> +
> +#endif
> diff --git a/efi/payload/setup_header.h b/efi/payload/setup_header.h
> new file mode 100644
> index 000000000000..4f094b844415
> --- /dev/null
> +++ b/efi/payload/setup_header.h
> @@ -0,0 +1,63 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +#ifndef __EFI_PAYLOAD_SETUP_HEADER_H__
> +#define __EFI_PAYLOAD_SETUP_HEADER_H__
> +
> +#include <linux/types.h>
> +
> +struct x86_setup_header {
> +	/* first sector of the image */
> +	uint8_t code1[0x0020];
> +	uint16_t cl_magic;		/**< Magic number 0xA33F */
> +	uint16_t cl_offset;		/**< The offset of command line */
> +	uint8_t code2[0x01F1 - 0x0020 - 2 - 2];
> +	uint8_t setup_sects;		/**< The size of the setup in sectors */
> +	uint16_t root_flags;		/**< If the root is mounted readonly */
> +	uint16_t syssize;		/**< obsolete */
> +	uint16_t swap_dev;		/**< obsolete */
> +	uint16_t ram_size;		/**< obsolete */
> +	uint16_t vid_mode;		/**< Video mode control */
> +	uint16_t root_dev;		/**< Default root device number */
> +	uint16_t boot_flag;		/**< 0xAA55 magic number */
> +
> +	/* second sector of the image */
> +	uint16_t jump;			/**< Jump instruction (this is code!) */
> +	uint32_t header;		/**< Magic signature "HdrS" */
> +	uint16_t version;		/**< Boot protocol version supported */
> +	uint32_t realmode_swtch;	/**< Boot loader hook */
> +	uint16_t start_sys;		/**< The load-low segment (obsolete) */
> +	uint16_t kernel_version;	/**< Points to kernel version string */
> +	uint8_t type_of_loader;		/**< Boot loader identifier */
> +	uint8_t loadflags;		/**< Boot protocol option flags */
> +	uint16_t setup_move_size;	/**< Move to high memory size */
> +	uint32_t code32_start;		/**< Boot loader hook */
> +	uint32_t ramdisk_image;		/**< initrd load address */
> +	uint32_t ramdisk_size;		/**< initrd size */
> +	uint32_t bootsect_kludge;	/**< obsolete */
> +	uint16_t heap_end_ptr;		/**< Free memory after setup end */
> +	uint8_t ext_loader_ver;		/**< boot loader's extension of the version number */
> +	uint8_t ext_loader_type;	/**< boot loader's extension of its type */
> +	uint32_t cmd_line_ptr;		/**< Points to the kernel command line */
> +	uint32_t initrd_addr_max;	/**< Highest address for initrd */
> +	uint32_t kernel_alignment;	/**< Alignment unit required by the kernel */
> +	uint8_t relocatable_kernel;	/** */
> +	uint8_t min_alignment;		/** */
> +	uint16_t xloadflags;		/** */
> +	uint32_t cmdline_size;		/** */
> +	uint32_t hardware_subarch;	/** */
> +	uint64_t hardware_subarch_data;	/** */
> +	uint32_t payload_offset;	/** */
> +	uint32_t payload_length;	/** */
> +	uint64_t setup_data;		/** */
> +	uint64_t pref_address;		/** */
> +	uint32_t init_size;		/** */
> +	uint32_t handover_offset;	/** */
> +} __attribute__ ((packed));
> +
> +static inline bool is_x86_setup_header(const void *base)
> +{
> +	const struct x86_setup_header *hdr = base;
> +
> +	return hdr->boot_flag == 0xAA55 && hdr->header == 0x53726448;
> +}
> +
> +#endif

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