path: root/Documentation/x86/boot.txt
diff options
authorAnton Arapov <>2012-10-29 11:15:37 +0100
committerAnton Arapov <>2012-10-29 11:15:37 +0100
commit7d558cd9c7b18e4b16953265aa0da45e63f3b968 (patch)
tree7135d5a810768c9c619346282ee9cfdf1765e225 /Documentation/x86/boot.txt
parent985ef6b2108ed28ffd5f6630e1e0fce2e2a775f2 (diff)
fedora kernel: cd394142aac30b5c751f25b517572e2448695641v3.6.3-2f17
Signed-off-by: Anton Arapov <>
Diffstat (limited to 'Documentation/x86/boot.txt')
1 files changed, 45 insertions, 1 deletions
diff --git a/Documentation/x86/boot.txt b/Documentation/x86/boot.txt
index 7c3a8801b7c..9efceff51bf 100644
--- a/Documentation/x86/boot.txt
+++ b/Documentation/x86/boot.txt
@@ -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.
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.
@@ -363,7 +367,8 @@ Protocol: 2.00+
ext_loader_type <- 0x05
ext_loader_ver <- 0x23
- Assigned boot loader ids:
+ Assigned boot loader ids (hexadecimal):
0 LILO (0x00 reserved for pre-2.00 bootloader)
1 Loadlin
2 bootsect-loader (0x20, all other values reserved)
@@ -378,6 +383,8 @@ Protocol: 2.00+
C Arcturus Networks uCbootloader
E Extended (see ext_loader_type)
F Special (0xFF = undefined)
+ 10 Reserved
+ 11 Minimal Linux Bootloader <>
Please contact <> if you need a bootloader ID
value assigned.
@@ -690,6 +697,16 @@ Offset/size: 0x260/4
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.
@@ -1010,3 +1027,30 @@ 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.
+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
+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.