Adding upstream version 5.10.209.upstream/5.10.209

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 62 insertions, 0 deletions

diff --git a/Documentation/riscv/boot-image-header.rst b/Documentation/riscv/boot-image-header.rst
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+=================================
+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 = 0x05435352;  /* Magic number 2, little endian, "RSC\x05" */
+	u32 res3;		  /* 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 res3(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.