What is ELF

> file /bin/bash
/bin/bash: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0, stripped

> readelf -h /bin/bash                                               
ELF Header:
 Magic:  7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
 Class:               ELF64
 Data:               2's complement, little endian
 Version:              1 (current)
 OS/ABI:              UNIX - System V
 ABI Version:            0
 Type:               DYN (Position-Independent Executable file)
 Machine:              Advanced Micro Devices X86-64
 Version:              0x1
 Entry point address:        0x10ab0
 Start of program headers:     64 (bytes into file)
 Start of section headers:     863256 (bytes into file)
 Flags:               0x0
 Size of this header:        64 (bytes)
 Size of program headers:      56 (bytes)
 Number of program headers:     13
 Size of section headers:      64 (bytes)
 Number of section headers:     28
 Section header string table index: 27

> od -Ax -t x1 -N 64 /bin/bash                                           
000000 7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
000010 03 00 3e 00 01 00 00 00 b0 0a 01 00 00 00 00 00
000020 40 00 00 00 00 00 00 00 18 2c 0d 00 00 00 00 00
000030 00 00 00 00 40 00 38 00 0d 00 40 00 1c 00 1b 00
000040

> readelf -h /bin/bash                                               
ELF Header:
 Magic:  7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
 Class:               ELF64
 Data:               2's complement, little endian
 Version:              1 (current)
 OS/ABI:              UNIX - System V
 ABI Version:            0
 Type:               DYN (Position-Independent Executable file)
 Machine:              Advanced Micro Devices X86-64
 Version:              0x1
 Entry point address:        0x10ab0
 Start of program headers:     64 (bytes into file)
 Start of section headers:     863256 (bytes into file)
 Flags:               0x0
 Size of this header:        64 (bytes)
 Size of program headers:      56 (bytes)
 Number of program headers:     13
 Size of section headers:      64 (bytes)
 Number of section headers:     28
 Section header string table index: 27

> ldd /bin/bash
	linux-vdso.so.1 (0x00007ffd9d55b000)
	libreadline.so.8 => /lib64/libreadline.so.8 (0x00007fc83225b000)
	libtinfo.so.6 => /lib64/libtinfo.so.6 (0x00007fc83221f000)
	libc.so.6 => /lib64/libc.so.6 (0x00007fc83202b000)
	libtinfow.so.6 => /lib64/libtinfow.so.6 (0x00007fc831fef000)
	/lib64/ld-linux-x86-64.so.2 (0x00007fc8323b1000)

> objdump -p /bin/bash

/bin/bash:   file format elf64-x86-64

Program Header:
  PHDR off  0x0000000000000040 vaddr 0x0000000000000040 paddr 0x0000000000000040 align 2**3
     filesz 0x00000000000002d8 memsz 0x00000000000002d8 flags r--
 INTERP off  0x0000000000000318 vaddr 0x0000000000000318 paddr 0x0000000000000318 align 2**0
     filesz 0x000000000000001c memsz 0x000000000000001c flags r--
  LOAD off  0x0000000000000000 vaddr 0x0000000000000000 paddr 0x0000000000000000 align 2**12
     filesz 0x000000000000d070 memsz 0x000000000000d070 flags r--
  LOAD off  0x000000000000e000 vaddr 0x000000000000e000 paddr 0x000000000000e000 align 2**12
     filesz 0x0000000000090275 memsz 0x0000000000090275 flags r-x
  LOAD off  0x000000000009f000 vaddr 0x000000000009f000 paddr 0x000000000009f000 align 2**12
     filesz 0x000000000002e0f0 memsz 0x000000000002e0f0 flags r--
  LOAD off  0x00000000000cd4b0 vaddr 0x00000000000ce4b0 paddr 0x00000000000ce4b0 align 2**12
     filesz 0x000000000000566c memsz 0x00000000000143f0 flags rw-
 DYNAMIC off  0x00000000000ced10 vaddr 0x00000000000cfd10 paddr 0x00000000000cfd10 align 2**3
     filesz 0x0000000000000200 memsz 0x0000000000000200 flags rw-
  NOTE off  0x0000000000000338 vaddr 0x0000000000000338 paddr 0x0000000000000338 align 2**3
     filesz 0x0000000000000030 memsz 0x0000000000000030 flags r--
  NOTE off  0x0000000000000368 vaddr 0x0000000000000368 paddr 0x0000000000000368 align 2**2
     filesz 0x0000000000000020 memsz 0x0000000000000020 flags r--
0x6474e553 off  0x0000000000000338 vaddr 0x0000000000000338 paddr 0x0000000000000338 align 2**3
     filesz 0x0000000000000030 memsz 0x0000000000000030 flags r--
EH_FRAME off  0x00000000000b6f00 vaddr 0x00000000000b6f00 paddr 0x00000000000b6f00 align 2**2
     filesz 0x00000000000032cc memsz 0x00000000000032cc flags r--
  STACK off  0x0000000000000000 vaddr 0x0000000000000000 paddr 0x0000000000000000 align 2**4
     filesz 0x0000000000000000 memsz 0x0000000000000000 flags rw-
  RELRO off  0x00000000000cd4b0 vaddr 0x00000000000ce4b0 paddr 0x00000000000ce4b0 align 2**0
     filesz 0x0000000000001b50 memsz 0x0000000000001b50 flags r--

Dynamic Section:
 NEEDED        libreadline.so.8
 NEEDED        libtinfo.so.6
 NEEDED        libc.so.6
 INIT         0x000000000000e000
 FINI         0x000000000009e26c
 INIT_ARRAY      0x00000000000ce4b0
 INIT_ARRAYSZ     0x0000000000000008
 FINI_ARRAY      0x00000000000ce4b8
 FINI_ARRAYSZ     0x0000000000000008
 GNU_HASH       0x0000000000000388
 STRTAB        0x0000000000002ce8
 SYMTAB        0x0000000000000840
 STRSZ        0x000000000000153f
 SYMENT        0x0000000000000018
 DEBUG        0x0000000000000000
 PLTGOT        0x00000000000d0000
 PLTRELSZ       0x0000000000001ad0
 PLTREL        0x0000000000000007
 JMPREL        0x000000000000b5a0
 RELA         0x00000000000045f8
 RELASZ        0x0000000000006fa8
 RELAENT       0x0000000000000018
 FLAGS_1       0x0000000008000000
 VERNEED       0x0000000000004538
 VERNEEDNUM      0x0000000000000001
 VERSYM        0x0000000000004228
 RELACOUNT      0x000000000000044b

Version References:
 required from libc.so.6:
  0x06969185 0x00 12 GLIBC_2.25
  0x06969191 0x00 11 GLIBC_2.11
  0x06969194 0x00 10 GLIBC_2.14
  0x0d696918 0x00 09 GLIBC_2.8
  0x069691b3 0x00 08 GLIBC_2.33
  0x06969195 0x00 07 GLIBC_2.15
  0x0d696914 0x00 06 GLIBC_2.4
  0x069691b4 0x00 05 GLIBC_2.34
  0x09691974 0x00 04 GLIBC_2.3.4
  0x0d696913 0x00 03 GLIBC_2.3
  0x09691a75 0x00 02 GLIBC_2.2.5