removed confusing old README information

Author: phip1611

README.md

@@ -10,9 +10,7 @@ used in a Multiboot2-kernel.
 
 It follows the Multiboot 2.0 specification at https://www.gnu.org/software/grub/manual/multiboot2/multiboot.html and the ELF 64 specification at http://www.uclibc.org/docs/elf-64-gen.pdf.
 
-Below is the draft for a blog post about this. I don't plan to finish it but maybe it's helpful as documentation.
-
-## The Multiboot 2 Information Structure
+## Background: The Multiboot 2 Information Structure
 The Multiboot information structure looks like this:
 
 Field            | Type
@@ -30,46 +28,7 @@ type          | u32
 size          | u32
 other fields  | variable
 
-All tags are 8-byte aligned. The last tag must be the _end tag_, which is a tag of type `0` and size `8`.
-
-## Tags
-
-We are interested in two tags, the _Elf-symbols_ tag and the _memory map_ tag. For a full list of possible tags see section 3.4 in the Multiboot 2 specification ([PDF][Multiboot 2]).
-
-[Multiboot 2]: http://nongnu.askapache.com/grub/phcoder/multiboot.pdf
-
-### The Elf-Symbols Tag
-The Elf-symbols tag contains a list of all sections of the loaded [ELF] kernel. It has the following format:
-
-[ELF]: http://www.uclibc.org/docs/elf-64-gen.pdf
-
-Field                       | Type
---------------------------- | -----------------
-type = 9                    | u32
-size                        | u32
-number of entries           | u32
-entry size                  | u32
-string table                | u32
-section headers             | variable
-
-Note that this format differs from the description in the Multiboot specification because it seems to be wrong for ELF 64 kernels: The `number of entries`, `entry size`, and `string table` fields seem to be `u32` instead of `u16`. The `multiboot2.h` file in the example section of the specification also specifies these fields as being `u32`, which suggests that the `u16` fields are an editing error. The GRUB2 bootloader [uses u32 fields](https://github.com/josefbacik/grub2/blob/96695ad84ce9c93f057ba53ae77d04d8561586e9/include/multiboot2.h#L298-L300), too.
-
-The section headers are just copied from the ELF file, so we need to look at the ELF specification to find the corresponding structure definition. Our kernel is a 64-bit ELF file, so we need to look at the ELF-64 specification ([PDF][ELF specification]). According to section 4 and figure 3, a section header has the following format:
-
-[ELF specification]: http://www.uclibc.org/docs/elf-64-gen.pdf
-
-Field                       | Type             | Value
---------------------------- | ---------------- | -----------
-name                        | u32              | string table index
-type                        | u32              | `0` (unused), `1` (section of program), `3` (string table), `8` (uninitialized section), etc.
-flags                       | u64              | `0x1` (writable), `0x2` (loaded), `0x4` (executable), etc.
-address                     | u64              | virtual start address of section (0 if not loaded)
-file offset                 | u64              | offset (in bytes) of section contents in the file
-size                        | u64              | size of the section in bytes
-link                        | u32              | associated section (only for some section types)
-info                        | u32              | extra information (only for some section types)
-address align               | u64              | required alignment of section (power of 2)
-entry size                  | u64              | contains the entry size for table sections (e.g. string table)
+All tags and the mbi itself are 8-byte aligned. The last tag must be the _end tag_, which is a tag of type `0` and size `8`.
 
 ## License