+Cc: Yun Liu <liuyun@xxxxxxxxxxx>
2022-11-21 (一) 20:16:30 +0800 Yanteng Si 曰：
> Describes the meaning and value of the image header field.
>
> Suggested-by: Xiaotian Wu <wuxiaotian@xxxxxxxxxxx>
> Signed-off-by: Yanteng Si <siyanteng@xxxxxxxxxxx>
> ---
> Documentation/loongarch/boot-image-header.rst | 76 +++++++++++++++++++
> Documentation/loongarch/index.rst | 1 +
> 2 files changed, 77 insertions(+)
> create mode 100644 Documentation/loongarch/boot-image-header.rst
>
> diff --git a/Documentation/loongarch/boot-image-header.rst b/Documentation/loongarch/boot-image-header.rst
> new file mode 100644
> index 000000000000..92a953a6f2e6
> --- /dev/null
> +++ b/Documentation/loongarch/boot-image-header.rst
> @@ -0,0 +1,76 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +====================================
> +Boot image header in LoongArch Linux
> +====================================
> +
> +:Author: Yanteng Si <siyanteng@xxxxxxxxxxx>
> +:Date: 18 Nov 2022
> +
> +This document only describes the boot image header details for
> +LoongArch Linux.
> +
> +The following 64-byte header is present in decompressed Linux
> +kernel image::
> +
> + u32 MZ_MAGIC /* "MZ", MS-DOS header */
> + u32 res0 = 0 /* reserved */
> + u64 kernel_entry /* Kernel entry point */
> + u64 _end - _text /* Kernel image effective size */
> + u64 0 /* Kernel image load offset from start of RAM */
> + u64 res1 = 0 /* reserved */
> + u64 res2 = 0 /* reserved */
> + u64 res3 = 0 /* reserved */
> + u32 res4 = 0 /* reserved */
> + u32 pe_header - _head /* Offset to the PE header */
> +
Any code related need to be linked here?
> +
> +Header notes
> +============
> +
> +Currently, LoongArch has removed the "magic" field.
> +
> +According to the EFI specification, the PE/COFF image file header is
> +required at the beginning of the kernel image; the LoongArch kernel
> +supports the EFI stub, so the first two bytes of the kernel image header
> +are "MZ" magic characters, and 0x3c should point to the rest of the
> +PE/COFF file header, between which The kernel entry point, image
> +effectivesize, and image load offset layout are as follows::
> +
> + +-----------------------------------------------+
> + 0x0: | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
> + +-----------------------------------------------+
> + 0x8: | MZ_MAGIC | res0 |
> + +-----------------------------------------------+
> + 0x10: | kernel_entry |
> + +-----------------------------------------------+
> + 0x18: | _end - _text |
> + +-----------------------------------------------+
> + 0x20: | 0 |
> + +-----------------------------------------------+
> + 0x28: | res1 |
> + +-----------------------------------------------+
> + 0x30: | res2 |
> + +-----------------------------------------------+
> + 0x38: | res3 |
> + +-----------------------------------------------+
> + 0x40: | res14 | PE header |
> + +-----------------------------------------------+
> +
emmm, this figure...
So MZ_MAGIC start from 0x08 ?
Or
0 1 2 3 4 5 6 7
+-----------------------+-----------------------+
0x00 | MZ_MAGIC | res0 |
+-----------------------+-----------------------+
0x08 | kernel_entry |
+-----------------------------------------------+
0x10 | _end - _text |
+-----------------------------------------------+
0x18 | 0 |
+-----------------------------------------------+
0x20 | res1 |
+-----------------------------------------------+
0x28 | res2 |
+-----------------------------------------------+
0x30 | res3 |
+-----------------------+-----------------------+
0x38 | res14 | PE header |
+-----------------------+-----------------------+
If the figure is too difficult to draw, a simple table can also be used
to instead.
Offset Name Size Note
...
> +
> +All bit fields are in little endian:
> +
> + - MZ: Effective length of 2 bytes;
> +
> + - kernel entry point: leaving 6 bytes blank in front, starting
> + from 0x8, with a effective length of 8 bytes;
> +
> + - kernel image effective size: Immediately following the kernel
> + entry point, with a effective length of 8 bytes, this field is
> + required for the bootloader;
> +
> + - kernel image load offset: Immediately following the kernel
> + image effective size, with a effective length of 8 bytes;
> +
> + - Offset to the PE header: leaving 28 bytes blank in front,
> + starting from 0x3c, with a effective length of 4 bytes.
> diff --git a/Documentation/loongarch/index.rst b/Documentation/loongarch/index.rst
> index aaba648db907..97419821adf9 100644
> --- a/Documentation/loongarch/index.rst
> +++ b/Documentation/loongarch/index.rst
> @@ -10,6 +10,7 @@ LoongArch Architecture
>
> introduction
> irq-chip-model
> + boot-image-header
>
> features
>
> --
> 2.31.1
>
--
Wu XiangCheng 0x32684A40BCA7AEA7
