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Sprache English
Level University
Created / Updated 21.06.2019 / 21.06.2019
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Describe the memory layout of a 32 bit system inluding the EIP and ESP pointer.

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What are the charecteristics of the stack?

Stack:

  • There is one contiguous memory region containing the stack for the process
  • LIFO - Last in, First Out
  • Contains funtion local variables
  • Also contains: Saved Instruction Pointer (SIP)
  • Current function adds data to the top (bottom) of the stack
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What are the charecteristics of the heap?

Heap: 

  • There is on contiguous memory region containing the heap
  • Memory allocator returns specific pieces of the memory region
  • For malloc()
  • Alos contains: heap management data
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What is stored in the code region in memory?

Code region contains:

  • Compiled program code
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What is the ELF format, and name 3 types.

Programs are stored in ELF files

ELF: Executable and Linkable Format

  • Like COFF, PE (EXE), ....

ELF types:

  • ET_EXEC: Executable File
  • ET_REL: Relocatable File
  • ET_DYN: Shared Object File

ELF "views"

  • Sections
  • Segments
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Describe the ELF Format how is it structured?

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Sturcture of ELF file from top to bottom:

  1. ELF Header
  2. Program Header Table (contains the location of sections)
  3. Sections (are contained in segments)
  4. Section Header Table (contains locationn of sections
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In the ELF format what can be contained in the sections?

Sections:

  • .text: Executable instructions
  • .bss: Unitialized data (usualy the heap)
  • .data: initialized data
  • .rodata: Read-Only data
  • .got: Global Offset Table
  • .plt: Prcedure Linkage Table
  • .init / .fini: initialiyation instructions ("glibc")
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How is an ELF file loaded what is loaded into the stack, heap and code block?

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.plt, .text, .init get written into code block

.got, .data, .bss is written into the heap

unalocated space is the stack.