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: Matt Fleming <matt.fleming@intel.com>
Acked-and-Tested-by: Matthew Garrett <mjg@redhat.com>
Link: http://lkml.kernel.org/r/1342689828-16815-1-git-send-email-matt@console-pimps.org
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

4 files changed, 143 insertions, 79 deletions

diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
index 4e85f5f85837..b3e0227df2c9 100644
--- a/arch/x86/boot/compressed/eboot.c
+++ b/arch/x86/boot/compressed/eboot.c
@@ -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;
 
diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index c85e3ac99bba..aa4aaf1b2380 100644
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -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
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index 87e03a13d8e3..2c4b171eec33 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -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
diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S
index 8bbea6aa40d9..097f4760faea 100644
--- a/arch/x86/boot/header.S
+++ b/arch/x86/boot/header.S
@@ -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 #####################################################