mirror of https://gitee.com/openkylin/linux.git
63 lines
2.2 KiB
ReStructuredText
63 lines
2.2 KiB
ReStructuredText
|
=================================
|
||
|
|
Boot image header in RISC-V Linux
|
||
|
|
=================================
|
||
|
|
|
||
|
|
:Author: Atish Patra <atish.patra@wdc.com>
|
||
|
|
:Date: 20 May 2019
|
||
|
|
|
||
|
|
This document only describes the boot image header details for RISC-V Linux.
|
||
|
|
|
||
|
|
TODO:
|
||
|
|
Write a complete booting guide.
|
||
|
|
|
||
|
|
The following 64-byte header is present in decompressed Linux kernel image::
|
||
|
|
|
||
|
|
u32 code0; /* Executable code */
|
||
|
|
u32 code1; /* Executable code */
|
||
|
|
u64 text_offset; /* Image load offset, little endian */
|
||
|
|
u64 image_size; /* Effective Image size, little endian */
|
||
|
|
u64 flags; /* kernel flags, little endian */
|
||
|
|
u32 version; /* Version of this header */
|
||
|
|
u32 res1 = 0; /* Reserved */
|
||
|
|
u64 res2 = 0; /* Reserved */
|
||
|
|
u64 magic = 0x5643534952; /* Magic number, little endian, "RISCV" */
|
||
|
|
u32 magic2 = 0x56534905; /* Magic number 2, little endian, "RSC\x05" */
|
||
|
|
u32 res4; /* Reserved for PE COFF offset */
|
||
|
|
|
||
|
|
This header format is compliant with PE/COFF header and largely inspired from
|
||
|
|
ARM64 header. Thus, both ARM64 & RISC-V header can be combined into one common
|
||
|
|
header in future.
|
||
|
|
|
||
|
|
Notes
|
||
|
|
=====
|
||
|
|
|
||
|
|
- This header can also be reused to support EFI stub for RISC-V in future. EFI
|
||
|
|
specification needs PE/COFF image header in the beginning of the kernel image
|
||
|
|
in order to load it as an EFI application. In order to support EFI stub,
|
||
|
|
code0 should be replaced with "MZ" magic string and res5(at offset 0x3c) should
|
||
|
|
point to the rest of the PE/COFF header.
|
||
|
|
|
||
|
|
- version field indicate header version number
|
||
|
|
|
||
|
|
========== =============
|
||
|
|
Bits 0:15 Minor version
|
||
|
|
Bits 16:31 Major version
|
||
|
|
========== =============
|
||
|
|
|
||
|
|
This preserves compatibility across newer and older version of the header.
|
||
|
|
The current version is defined as 0.2.
|
||
|
|
|
||
|
|
- The "magic" field is deprecated as of version 0.2. In a future
|
||
|
|
release, it may be removed. This originally should have matched up
|
||
|
|
with the ARM64 header "magic" field, but unfortunately does not.
|
||
|
|
The "magic2" field replaces it, matching up with the ARM64 header.
|
||
|
|
|
||
|
|
- In current header, the flags field has only one field.
|
||
|
|
|
||
|
|
===== ====================================
|
||
|
|
Bit 0 Kernel endianness. 1 if BE, 0 if LE.
|
||
|
|
===== ====================================
|
||
|
|
|
||
|
|
- Image size is mandatory for boot loader to load kernel image. Booting will
|
||
|
|
fail otherwise.
|