From: H. Peter Anvin <hpa@xxxxxxxxx>
Add documentation for the runtime_start and runtime_size fields;
bzImage protocol version 2.10 (0x020a).
[ Impact: documentation only ]
Signed-off-by: H. Peter Anvin <hpa at zytor.com>
---
Documentation/x86/boot.txt | 41 +++++++++++++++++++++++++++++++++++++++++
1 files changed, 41 insertions(+), 0 deletions(-)
diff --git a/Documentation/x86/boot.txt b/Documentation/x86/boot.txt
index e020366..093f838 100644
--- a/Documentation/x86/boot.txt
+++ b/Documentation/x86/boot.txt
@@ -50,6 +50,10 @@ Protocol 2.08: (Kernel 2.6.26) Added crc32 checksum and ELF format
Protocol 2.09: (Kernel 2.6.26) Added a field of 64-bit physical
pointer to single linked list of struct setup_data.
+Protocol 2.10: (Kernel 2.6.31) Added the runtime_start and
+ runtime_size fields for the post-decompression address
+ and memory requirements of the kernel.
+
**** MEMORY LAYOUT
The traditional memory map for the kernel loader, used for Image or
@@ -182,6 +186,8 @@ Offset Proto Name Meaning
024C/4 2.08+ payload_length Length of kernel payload
0250/8 2.09+ setup_data 64-bit physical pointer to linked list
of struct setup_data
+0258/4 2.10+ runtime_start (Minimum) post-decompression address
+025C/4 2.10+ runtime_size Minimum linear memory required
(1) For backwards compatibility, if the setup_sects field contains 0, the
real value is 4.
@@ -582,6 +588,41 @@ Protocol: 2.09+
sure to consider the case where the linked list already contains
entries.
+Field name: runtime_start
+Type: modify (optional, reloc)
+Offset/size: 0x258/4
+Protocol: 2.10+
+
+ For a non-relocatable kernel, this is a readonly field indicating
+ the post-decompression address of the kernel. This will typically
+ be larger than the load address (0x100000).
+
+ For a relocatable kernel, this is a read-write field indicating the
+ *minimum* post-decompression address of the kernel. This allows
+ unchanged behavior when a non-relocating bootloader is used. If
+ this value is greater than the load address, this value is used; if
+ this value is smaller than the load address, the load address is
+ rounded up to the nearest multiple of the kernel_alignment field and
+ this field is ignored.
+
+ A relocating bootloader can override this field, e.g. by setting it
+ to zero, to force the load address to control the runtime address of
+ the kernel.
+
+Field name: runtime_size
+Type: read
+Offset/size: 0x25C/4
+Protocol: 2.10+
+
+ This field informs the boot loader of the amount of linearly
+ contiguous memory starting at the kernel decompression address (as
+ given by the appropriate combination of the load address,
+ runtime_start, and kernel_alignment) that the kernel will require
+ before it becomes aware of the memory map. It does *not* guarantee
+ a successful boot with only this memory, but it may be a useful
+ guideline for a relocating bootloader when it comes to selecting an
+ address to load the kernel.
+
**** THE IMAGE CHECKSUM
--
1.6.0.6
