x86, boot: Define the 2.12 bzImage boot protocol

[linux-beck.git] / Documentation / x86 / boot.txt

diff --git a/Documentation/x86/boot.txt b/Documentation/x86/boot.txt
index 406d82d5d2bb1e08a8cb9e4c548ce937f448b376..3edb4c2887a1f816eaf0f53f7dbf800bf73bf42a 100644 (file)
--- a/Documentation/x86/boot.txt
+++ b/Documentation/x86/boot.txt
@@ -57,6 +57,10 @@ Protocol 2.10:       (Kernel 2.6.31) Added a protocol for relaxed alignment
 Protocol 2.11: (Kernel 3.6) Added a field for offset of EFI handover
                protocol entry point.
 
+Protocol 2.12: (Kernel 3.9) Added the xloadflags field and extension fields
+               to struct boot_params for for loading bzImage and ramdisk
+               above 4G in 64bit.
+
 **** MEMORY LAYOUT
 
 The traditional memory map for the kernel loader, used for Image or
@@ -182,7 +186,7 @@ Offset      Proto   Name            Meaning
 0230/4 2.05+   kernel_alignment Physical addr alignment required for kernel
 0234/1 2.05+   relocatable_kernel Whether kernel is relocatable or not
 0235/1 2.10+   min_alignment   Minimum alignment, as a power of two
-0236/2 N/A     pad3            Unused
+0236/2 2.12+   xloadflags      Boot protocol option flags
 0238/4 2.06+   cmdline_size    Maximum size of the kernel command line
 023C/4 2.07+   hardware_subarch Hardware subarchitecture
 0240/8 2.07+   hardware_subarch_data Subarchitecture-specific data
@@ -582,6 +586,27 @@ Protocol:  2.10+
   misaligned kernel.  Therefore, a loader should typically try each
   power-of-two alignment from kernel_alignment down to this alignment.
 
+Field name:     xloadflags
+Type:           read
+Offset/size:    0x236/2
+Protocol:       2.12+
+
+  This field is a bitmask.
+
+  Bit 0 (read):        XLF_KERNEL_64
+       - If 1, this kernel has the legacy 64-bit entry point at 0x200.
+
+  Bit 1 (read): XLF_CAN_BE_LOADED_ABOVE_4G
+        - If 1, kernel/boot_params/cmdline/ramdisk can be above 4G.
+
+  Bit 2 (read):        XLF_EFI_HANDOVER_32
+       - If 1, the kernel supports the 32-bit EFI handoff entry point
+          given at handover_offset.
+
+  Bit 3 (read): XLF_EFI_HANDOVER_64
+       - If 1, the kernel supports the 64-bit EFI handoff entry point
+          given at handover_offset + 0x200.
+
 Field name:    cmdline_size
 Type:          read
 Offset/size:   0x238/4