[mit 6.s081] LEC 5: calling conventions and stack frames risc-v notes

Lec 5: Calling conventions and stack frames RISC-V

• Ref: https://github.com/huihongxiao/MIT6.S081/tree/master/lec05-calling-conventions-and-stack-frames-risc-v
• Preparation: Calling Convention

Outline

• C -> ASM / Processors
• RISC-V & x86
• Registers
• Stack + calling conventions
• Struct Layout in memory

C -> ASM

• C -> Asm -> Bianary (.o/.obj file )

RISC-V & x86

• RISC-V( Reduced instruction set ) and x86( Complex instruction set ) The difference between :
  • Number of instruction sets : RISC-V Fewer instruction sets
  • RISC-V The operation ratio of instructions x86 It's simpler
  • RISC Instruction set open source
• RISC-V Instruction set composition :
  • Base Integer Instruction Set: Commonly used instructions , Such as add, mult
  • Standard Extension Instruction Set: Extended instruction set

RISC-V Registers

• a0~a7 Used to pass parameters to functions , The parameter exceeds 8 Use this memory to transfer parameters
• Saver:
  • Caller: Not preserved across function call The value of this type of register will not be retained during the function call , That is, the register may be rewritten in the function call
  • Callee: preserved across function call

Stack

• fp: frame ponter, Stack frame , amount to x86 Of bp.
• Assembly function ASM Function form :
  1. Function prologue: adjustment sp, Save return address ra
  2. Body
  3. Epollgue: Load the return address ra register , Restore sp