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Low-Level
ABI

ABI

  • How data structures & computational routines are accessed in machine code (Code Types)
    • Machine code therefore hardware-dependent
  • API defines this structure in source code
  • Adherence usually responsibility of

Components

  • Processor instruction set
    • Register file structure
    • Stack organisation
    • Memory access types
  • Size, layouts and alignments of basic data types
  • Calling Conventions
    • How function arguments are passed
      • Stack or register
      • Which registers for which function param
      • Parameter order
    • Return values retrieved
  • How app makes sys calls to OS
    • If ABI specifies direct sys calls over procedure calls to sys call stubs then sys call numbers
  • Binary format of object files, program files
    • For complete OS ABIs

Complete ABI

  • Allows program from one OS to run on any other without change
    • Provided all shared libraries and prerequisites etc

Embedded ABI

  • File format, data types, register usage, stack frame organisation, function parameter passing conventions
    • For embedded OS
  • Compilers create object code compatible with code from other compilers
Calling Conventions