Commit 9ca8f72a authored by Matt Fleming's avatar Matt Fleming Committed by H. Peter Anvin
Browse files

x86, efi: Handover Protocol 



As things currently stand, traditional EFI boot loaders and the EFI
boot stub are carrying essentially the same initialisation code
required to setup an EFI machine for booting a kernel. There's really
no need to have this code in two places and the hope is that, with
this new protocol, initialisation and booting of the kernel can be
left solely to the kernel's EFI boot stub. The responsibilities of the
boot loader then become,

   o Loading the kernel image from boot media

File system code still needs to be carried by boot loaders for the
scenario where the kernel and initrd files reside on a file system
that the EFI firmware doesn't natively understand, such as ext4, etc.

   o Providing a user interface

Boot loaders still need to display any menus/interfaces, for example
to allow the user to select from a list of kernels.

Bump the boot protocol number because we added the 'handover_offset'
field to indicate the location of the handover protocol entry point.

Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Peter Jones <pjones@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: default avatarMatt Fleming <matt.fleming@intel.com>
Acked-and-Tested-by: default avatarMatthew Garrett <mjg@redhat.com>
Link: http://lkml.kernel.org/r/1342689828-16815-1-git-send-email-matt@console-pimps.org


Signed-off-by: default avatarH. Peter Anvin <hpa@zytor.com>
parent bacef661

Documentation/x86/boot.txt

+41 −0
Original line number Diff line number Diff line
@@ -54,6 +54,9 @@ Protocol 2.10: (Kernel 2.6.31) Added a protocol for relaxed alignment 
		beyond the kernel_alignment added, new init_size and

		pref_address fields.  Added extended boot loader IDs.



Protocol 2.11:	(Kernel 3.6) Added a field for offset of EFI handover

		protocol entry point.



**** MEMORY LAYOUT



The traditional memory map for the kernel loader, used for Image or
@@ -189,6 +192,7 @@ Offset Proto Name Meaning 
				of struct setup_data

0258/8	2.10+	pref_address	Preferred loading address

0260/4	2.10+	init_size	Linear memory required during initialization

0264/4	2.11+	handover_offset	Offset of handover entry point



(1) For backwards compatibility, if the setup_sects field contains 0, the

    real value is 4.
@@ -690,6 +694,16 @@ Offset/size: 0x260/4 
  else

	runtime_start = pref_address



Field name:	handover_offset

Type:		read

Offset/size:	0x264/4



  This field is the offset from the beginning of the kernel image to

  the EFI handover protocol entry point. Boot loaders using the EFI

  handover protocol to boot the kernel should jump to this offset.



  See EFI HANDOVER PROTOCOL below for more details.





**** THE IMAGE CHECKSUM
@@ -1010,3 +1024,30 @@ segment; __BOOS_CS must have execute/read permission, and __BOOT_DS 
must have read/write permission; CS must be __BOOT_CS and DS, ES, SS

must be __BOOT_DS; interrupt must be disabled; %esi must hold the base

address of the struct boot_params; %ebp, %edi and %ebx must be zero.



**** EFI HANDOVER PROTOCOL



This protocol allows boot loaders to defer initialisation to the EFI

boot stub. The boot loader is required to load the kernel/initrd(s)

from the boot media and jump to the EFI handover protocol entry point

which is hdr->handover_offset bytes from the beginning of

startup_{32,64}.



The function prototype for the handover entry point looks like this,



    efi_main(void *handle, efi_system_table_t *table, struct boot_params *bp)



'handle' is the EFI image handle passed to the boot loader by the EFI

firmware, 'table' is the EFI system table - these are the first two

arguments of the "handoff state" as described in section 2.3 of the

UEFI specification. 'bp' is the boot loader-allocated boot params.



The boot loader *must* fill out the following fields in bp,



    o hdr.code32_start

    o hdr.cmd_line_ptr

    o hdr.cmdline_size

    o hdr.ramdisk_image (if applicable)

    o hdr.ramdisk_size  (if applicable)



All other fields should be zero.

arch/x86/boot/compressed/eboot.c

+120 −78
Original line number Diff line number Diff line
@@ -729,32 +729,68 @@ fail: 
 * need to create one ourselves (usually the bootloader would create

 * one for us).

 */

static efi_status_t make_boot_params(struct boot_params *boot_params,

				     efi_loaded_image_t *image,

				     void *handle)

struct boot_params *make_boot_params(void *handle, efi_system_table_t *_table)

{

	struct efi_info *efi = &boot_params->efi_info;

	struct apm_bios_info *bi = &boot_params->apm_bios_info;

	struct sys_desc_table *sdt = &boot_params->sys_desc_table;

	struct e820entry *e820_map = &boot_params->e820_map[0];

	struct e820entry *prev = NULL;

	struct setup_header *hdr = &boot_params->hdr;

	unsigned long size, key, desc_size, _size;

	efi_memory_desc_t *mem_map;

	void *options = image->load_options;

	u32 load_options_size = image->load_options_size / 2; /* ASCII */

	struct boot_params *boot_params;

	struct sys_desc_table *sdt;

	struct apm_bios_info *bi;

	struct setup_header *hdr;

	struct efi_info *efi;

	efi_loaded_image_t *image;

	void *options;

	u32 load_options_size;

	efi_guid_t proto = LOADED_IMAGE_PROTOCOL_GUID;

	int options_size = 0;

	efi_status_t status;

	__u32 desc_version;

	unsigned long cmdline;

	u8 nr_entries;

	u16 *s2;

	u8 *s1;

	int i;



	sys_table = _table;



	/* Check if we were booted by the EFI firmware */

	if (sys_table->hdr.signature != EFI_SYSTEM_TABLE_SIGNATURE)

		return NULL;



	status = efi_call_phys3(sys_table->boottime->handle_protocol,

				handle, &proto, (void *)&image);

	if (status != EFI_SUCCESS) {

		efi_printk("Failed to get handle for LOADED_IMAGE_PROTOCOL\n");

		return NULL;

	}



	status = low_alloc(0x4000, 1, (unsigned long *)&boot_params);

	if (status != EFI_SUCCESS) {

		efi_printk("Failed to alloc lowmem for boot params\n");

		return NULL;

	}



	memset(boot_params, 0x0, 0x4000);



	hdr = &boot_params->hdr;

	efi = &boot_params->efi_info;

	bi = &boot_params->apm_bios_info;

	sdt = &boot_params->sys_desc_table;



	/* Copy the second sector to boot_params */

	memcpy(&hdr->jump, image->image_base + 512, 512);



	/*

	 * Fill out some of the header fields ourselves because the

	 * EFI firmware loader doesn't load the first sector.

	 */

	hdr->root_flags = 1;

	hdr->vid_mode = 0xffff;

	hdr->boot_flag = 0xAA55;



	hdr->code32_start = (__u64)(unsigned long)image->image_base;



	hdr->type_of_loader = 0x21;



	/* Convert unicode cmdline to ascii */

	options = image->load_options;

	load_options_size = image->load_options_size / 2; /* ASCII */

	cmdline = 0;

	s2 = (u16 *)options;
@@ -791,18 +827,36 @@ static efi_status_t make_boot_params(struct boot_params *boot_params, 
	hdr->ramdisk_image = 0;

	hdr->ramdisk_size = 0;



	status = handle_ramdisks(image, hdr);

	if (status != EFI_SUCCESS)

		goto free_cmdline;



	setup_graphics(boot_params);



	/* Clear APM BIOS info */

	memset(bi, 0, sizeof(*bi));



	memset(sdt, 0, sizeof(*sdt));



	memcpy(&efi->efi_loader_signature, EFI_LOADER_SIGNATURE, sizeof(__u32));

	status = handle_ramdisks(image, hdr);

	if (status != EFI_SUCCESS)

		goto fail2;



	return boot_params;

fail2:

	if (options_size)

		low_free(options_size, hdr->cmd_line_ptr);

fail:

	low_free(0x4000, (unsigned long)boot_params);

	return NULL;

}



static efi_status_t exit_boot(struct boot_params *boot_params,

			      void *handle)

{

	struct efi_info *efi = &boot_params->efi_info;

	struct e820entry *e820_map = &boot_params->e820_map[0];

	struct e820entry *prev = NULL;

	unsigned long size, key, desc_size, _size;

	efi_memory_desc_t *mem_map;

	efi_status_t status;

	__u32 desc_version;

	u8 nr_entries;

	int i;



	size = sizeof(*mem_map) * 32;
@@ -811,7 +865,7 @@ again: 
	_size = size;

	status = low_alloc(size, 1, (unsigned long *)&mem_map);

	if (status != EFI_SUCCESS)

		goto free_cmdline;

		return status;



	status = efi_call_phys5(sys_table->boottime->get_memory_map, &size,

				mem_map, &key, &desc_size, &desc_version);
@@ -823,6 +877,7 @@ again: 
	if (status != EFI_SUCCESS)

		goto free_mem_map;



	memcpy(&efi->efi_loader_signature, EFI_LOADER_SIGNATURE, sizeof(__u32));

	efi->efi_systab = (unsigned long)sys_table;

	efi->efi_memdesc_size = desc_size;

	efi->efi_memdesc_version = desc_version;
@@ -906,61 +961,13 @@ again: 


free_mem_map:

	low_free(_size, (unsigned long)mem_map);

free_cmdline:

	if (options_size)

		low_free(options_size, hdr->cmd_line_ptr);

fail:

	return status;

}



/*

 * On success we return a pointer to a boot_params structure, and NULL

 * on failure.

 */

struct boot_params *efi_main(void *handle, efi_system_table_t *_table)

static efi_status_t relocate_kernel(struct setup_header *hdr)

{

	struct boot_params *boot_params;

	unsigned long start, nr_pages;

	struct desc_ptr *gdt, *idt;

	efi_loaded_image_t *image;

	struct setup_header *hdr;

	efi_status_t status;

	efi_guid_t proto = LOADED_IMAGE_PROTOCOL_GUID;

	struct desc_struct *desc;



	sys_table = _table;



	/* Check if we were booted by the EFI firmware */

	if (sys_table->hdr.signature != EFI_SYSTEM_TABLE_SIGNATURE)

		goto fail;



	status = efi_call_phys3(sys_table->boottime->handle_protocol,

				handle, &proto, (void *)&image);

	if (status != EFI_SUCCESS) {

		efi_printk("Failed to get handle for LOADED_IMAGE_PROTOCOL\n");

		goto fail;

	}



	status = low_alloc(0x4000, 1, (unsigned long *)&boot_params);

	if (status != EFI_SUCCESS) {

		efi_printk("Failed to alloc lowmem for boot params\n");

		goto fail;

	}



	memset(boot_params, 0x0, 0x4000);



	hdr = &boot_params->hdr;



	/* Copy the second sector to boot_params */

	memcpy(&hdr->jump, image->image_base + 512, 512);



	/*

	 * Fill out some of the header fields ourselves because the

	 * EFI firmware loader doesn't load the first sector.

	 */

	hdr->root_flags = 1;

	hdr->vid_mode = 0xffff;

	hdr->boot_flag = 0xAA55;



	/*

	 * The EFI firmware loader could have placed the kernel image
@@ -978,16 +985,40 @@ struct boot_params *efi_main(void *handle, efi_system_table_t *_table) 
	if (status != EFI_SUCCESS) {

		status = low_alloc(hdr->init_size, hdr->kernel_alignment,

				   &start);

		if (status != EFI_SUCCESS) {

		if (status != EFI_SUCCESS)

			efi_printk("Failed to alloc mem for kernel\n");

			goto fail;

		}

	}



	if (status == EFI_SUCCESS)

		memcpy((void *)start, (void *)(unsigned long)hdr->code32_start,

		       hdr->init_size);



	hdr->pref_address = hdr->code32_start;

	hdr->code32_start = (__u32)start;

	hdr->pref_address = (__u64)(unsigned long)image->image_base;



	memcpy((void *)start, image->image_base, image->image_size);

	return status;

}



/*

 * On success we return a pointer to a boot_params structure, and NULL

 * on failure.

 */

struct boot_params *efi_main(void *handle, efi_system_table_t *_table,

			     struct boot_params *boot_params)

{

	struct desc_ptr *gdt, *idt;

	efi_loaded_image_t *image;

	struct setup_header *hdr = &boot_params->hdr;

	efi_status_t status;

	struct desc_struct *desc;



	sys_table = _table;



	/* Check if we were booted by the EFI firmware */

	if (sys_table->hdr.signature != EFI_SYSTEM_TABLE_SIGNATURE)

		goto fail;



	setup_graphics(boot_params);



	status = efi_call_phys3(sys_table->boottime->allocate_pool,

				EFI_LOADER_DATA, sizeof(*gdt),
@@ -1015,7 +1046,18 @@ struct boot_params *efi_main(void *handle, efi_system_table_t *_table) 
	idt->size = 0;

	idt->address = 0;



	status = make_boot_params(boot_params, image, handle);

	/*

	 * If the kernel isn't already loaded at the preferred load

	 * address, relocate it.

	 */

	if (hdr->pref_address != hdr->code32_start) {

		status = relocate_kernel(hdr);



		if (status != EFI_SUCCESS)

			goto fail;

	}



	status = exit_boot(boot_params, handle);

	if (status != EFI_SUCCESS)

		goto fail;

arch/x86/boot/compressed/head_32.S

+10 −0
Original line number Diff line number Diff line
@@ -42,6 +42,16 @@ ENTRY(startup_32) 
	 */

	add	$0x4, %esp



	call	make_boot_params

	cmpl	$0, %eax

	je	1f

	movl	0x4(%esp), %esi

	movl	(%esp), %ecx

	pushl	%eax

	pushl	%esi

	pushl	%ecx



	.org 0x30,0x90

	call	efi_main

	cmpl	$0, %eax

	movl	%eax, %esi

arch/x86/boot/compressed/head_64.S

+10 −0
Original line number Diff line number Diff line
@@ -209,6 +209,16 @@ ENTRY(startup_64) 
	.org 0x210

	mov	%rcx, %rdi

	mov	%rdx, %rsi

	pushq	%rdi

	pushq	%rsi

	call	make_boot_params

	cmpq	$0,%rax

	je	1f

	mov	%rax, %rdx

	popq	%rsi

	popq	%rdi



	.org 0x230,0x90

	call	efi_main

	movq	%rax,%rsi

	cmpq	$0,%rax

arch/x86/boot/header.S

+3 −1
Original line number Diff line number Diff line
@@ -263,7 +263,7 @@ _start: 
	# Part 2 of the header, from the old setup.S



		.ascii	"HdrS"		# header signature

		.word	0x020a		# header version number (>= 0x0105)

		.word	0x020b		# header version number (>= 0x0105)

					# or else old loadlin-1.5 will fail)

		.globl realmode_swtch

realmode_swtch:	.word	0, 0		# default_switch, SETUPSEG
@@ -381,6 +381,8 @@ pref_address: .quad LOAD_PHYSICAL_ADDR # preferred load addr 
#define INIT_SIZE VO_INIT_SIZE

#endif

init_size:		.long INIT_SIZE		# kernel initialization size

handover_offset:	.long 0x30		# offset to the handover

						# protocol entry point



# End of setup header #####################################################

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