Modifying fs/binfmt_elf.c to fetch a custom-added section content - c

Question

I am trying to modify fs/binfmt_elf.c to fetch the content of a new ELF section I have added to my sample C program.
Sample C program:
#include <stdio.h>
/* Adding my own ELF section*/
char my_custom_section[128][2] __attribute__ ((section (".mysection"))) = { 0 };
int main() {
return 0;
}
Here's the output of readelf -l a.out:
Elf file type is EXEC (Executable file)
Entry point 0x4003d0
There are 9 program headers, starting at offset 64
Program Headers:
Type Offset VirtAddr PhysAddr
FileSiz MemSiz Flags Align
PHDR 0x0000000000000040 0x0000000000400040 0x0000000000400040
0x00000000000001f8 0x00000000000001f8 R E 8
INTERP 0x0000000000000238 0x0000000000400238 0x0000000000400238
0x000000000000001c 0x000000000000001c R 1
[Requesting program interpreter: /lib64/ld-linux-x86-64.so.2]
LOAD 0x0000000000000000 0x0000000000400000 0x0000000000400000
0x000000000000067c 0x000000000000067c R E 200000
LOAD 0x0000000000000e28 0x0000000000600e28 0x0000000000600e28
0x00000000000002f8 0x0000000000000308 RW 200000
DYNAMIC 0x0000000000000e50 0x0000000000600e50 0x0000000000600e50
0x0000000000000190 0x0000000000000190 RW 8
NOTE 0x0000000000000254 0x0000000000400254 0x0000000000400254
0x0000000000000044 0x0000000000000044 R 4
GNU_EH_FRAME 0x00000000000005ac 0x00000000004005ac 0x00000000004005ac
0x000000000000002c 0x000000000000002c R 4
GNU_STACK 0x0000000000000000 0x0000000000000000 0x0000000000000000
0x0000000000000000 0x0000000000000000 RW 8
GNU_RELRO 0x0000000000000e28 0x0000000000600e28 0x0000000000600e28
0x00000000000001d8 0x00000000000001d8 R 1
Section to Segment mapping:
Segment Sections...
00
01 .interp
02 .interp .note.ABI-tag .note.gnu.build-id .gnu.hash .dynsym .dynstr .gnu.version .gnu.version_r .rela.dyn .rela.plt .init .plt .text .fini .rodata .eh_frame_hdr .eh_frame
03 .ctors .dtors .jcr .dynamic .got .got.plt .data .mysection .bss
04 .dynamic
05 .note.ABI-tag .note.gnu.build-id
06 .eh_frame_hdr
07
08 .ctors .dtors .jcr .dynamic .got
So .mysection is assigned to segment 03 of type LOAD.
However, going through the source of fs/binfmt.c, I am unable to understand how exactly can I fetch the content/value of .mysection. It seems that load_elf_binary() only iterates through program headers and segments, and not section headers or sections.
(which presumably makes sense because it's a loader and hence, views an ELF file as segments and not as sections).
But even when it iterates through the program segments, I don't understand how is it iterating through the sections within a segment.
Basically, I need to fetch the value of my own section .mysection, through modifying fs/binfmt.c, so that whenever an ELF executable with .mynewsection is loaded in my kernel, its value is stored in some variable/CPU registers. Any pointers which can help in doing this job are much appreciated.
EDIT:
My primary goal is to extend the ELF file format into my own custom file format, which I plan to use for a research project on extending the x86 architecture. The executables in that extended architecture need to have a unique identity key used to perform cryptographic operations on its code/data segments. Therefore, a new section in the file could store that key, and the kernel loader can fetch it for further cryptographic processes.

Answer 1

But even when it iterates through the program segments, I don't
understand how is it iterating through the sections within a segment.
Since load_elf_binary() mmaps all the PT_LOAD segments into memory, and those segments contain all the needed sections (e. g. segment 03 contains sections .ctors .dtors .jcr .dynamic .got .got.plt .data .mysection .bss), there is no need for iterating through the sections.