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Practical Session 9 Co-Routines

This practical session explores the implementation of co-routines using state variables. Learn about co-routine structures, stack size, code position, flag position, and stack pointer position. Understand the initialization and resumption of co-routines.

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Practical Session 9 Co-Routines

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  1. Practical Session 9Co-Routines

  2. Co-Routines

  3. Co-routine state

  4. Variable Decleration STKSZ equ 16*1024 CODEP equ 0 FLAGSP equ 4 SPP equ 8 section .rodata align 16 global numco numco: dd 3 CORS: dd CO1 dd CO2 dd CO3 section .data align 16 ; Structure for first co-routine CO1: dd Function1 Flags1: dd 0 SP1: dd STK1+STKSZ ; Structure for second co-routine CO2: dd Function1 Flags2: dd 0 SP2: dd STK2+STKSZ ; Structure for third co-routine CO3: dd Function2 Flags3: dd 0 SP3: dd STK3+STKSZ ; Counter COUNTER: dd 0 MAX_ITER: dd 3 section .bss align 16 CURR: resd 1 SPT: resd 1 SPMAIN: resd 1 STK1: resb STKSZ STK2: resb STKSZ STK3: resb STKSZ

  5. Co-routine structure

  6. Co-routine structure

  7. Variables • STKSZ – Stack Size • CODEP – Code Position: Offset to code • FLAGP – Flag Position: Offset to flags • SPP – Stack Pointer Position: Offset to stack pointer • numco – Number of Co-Routines: Global • CORS –Co-Routines Array • COi – Function Address of Co-Routine i • Flagsi – Flags of Co-Routine i • SPi – Stack Pointer of Co-Routine i • STKi – The Stack of Co-Routine i • SPMain – Stack Pointer of Main Function • CURR – Current Co-Routine • SPT – Temporary Storage for Stack Pointer

  8. Initializtion section .text align 16 extern printf global init_co_from_c global start_co_from_c global end_co ; Initalize a co-routine number given as an argument from C init_co_from_c: push EBP mov EBP, ESP push EBX mov EBX, [EBP+8] mov EBX, [EBX*4+CORS] call co_init pop EBX pop EBP ret ; EBX is pointer to co-routine structure to initialize co_init: pusha bts dword [EBX+FLAGSP],0 ; test if already initialized jc init_done mov EAX,[EBX+CODEP] ; Get initial PC mov [SPT], ESP mov ESP,[EBX+SPP] ; Get initial SP mov EBP, ESP ; Also use as EBP push EAX ; Push initial "return" address pushf ; and flags pusha ; and all other regs mov [EBX+SPP],ESP ; Save new SP in structure mov ESP, [SPT] ; Restore original SP init_done: popa ret

  9. Co-routine initialization

  10. Co-routine initialization

  11. Co-routine initialization

  12. Function1 ; This function used as code for co-routines 0 and 1 Function1: push dword 0 push dword 1 push dword [CORS+8] push dword [CURR] push dword FMT1 call printf add ESP, 20 mov EBX, [CORS+8] call dword resume mov dword [COUNTER], 0 func1_loop: push dword [COUNTER] push dword 2 push dword [CORS+8] push dword [CURR] push dword FMT1 call printf add ESP, 20 add dword [COUNTER], 1 mov eax, [MAX_ITER] cmp [COUNTER], eax jne func1_loop mov EBX, [CORS+8] call dword resume jmp end_co

  13. Function2 ; This function used as code for co-routine 2 Function2: push dword 0 push dword 1 push dword [CORS] push dword [CURR] push dword FMT2 call printf add ESP, 16 mov EBX, [CORS] call dword resume mov dword [COUNTER], 0 func2_loop: push dword [COUNTER] push dword 2 push dword [CORS+4] push dword [CURR] push dword FMT2 call printf add ESP, 20 add dword [COUNTER], 1 mov eax, [MAX_ITER] cmp [COUNTER], eax jne func2_loop mov EBX, [CORS+4] call dword resume push dword 3 push dword [CORS] push dword [CURR] push dword FMT2 call printf add ESP, 16 mov EBX, [CORS] call dword resume push dword 4 push dword [CORS+4] push dword [CURR] push dword FMT2 call printf add ESP, 16 mov EBX, [CORS+4] call dword resume jmp end_co

  14. Co-routine code (function)

  15. Co-routine code (function)

  16. Resume ; EBX is pointer to co-init structure of co-routine to be resumed ; CURR holds a pointer to co-init structure of the curent co-routine resume: pushf ; Save state of caller pusha mov EDX, [CURR] mov [EDX+SPP],ESP ; Save current SP do_resume: mov ESP, [EBX+SPP] ; Load SP for resumed co-routine mov [CURR], EBX popa ; Restore resumed co-routine state popf ret ; "return" to resumed co-routine!

  17. Co-routine resume

  18. Co-routine resume

  19. Start and End ; C-callable start of the first co-routine start_co_from_c: push EBP mov EBP, ESP pusha mov [SPMAIN], ESP ; Save SP of main code mov EBX, [EBP+8] ; Get number of co-routine mov EBX, [EBX*4+CORS] ; and pointer to co-routine structure jmp do_resume ; End co-routine mechanism, back to C main end_co: mov ESP, [SPMAIN] ; Restore state of main code popa pop EBP ret

  20. Start Co-routine scheduler

  21. Example

  22. After Init

  23. Resuming resume: pushf pusha mov EDX, [CURR] mov [EDX+SPP],ESP do_resume: mov ESP, [EBX+SPP] mov [CURR], EBX popa popf ret

  24. Resuming – Resume is Called resume: pushf pusha mov EDX, [CURR] mov [EDX+SPP],ESP do_resume: mov ESP, [EBX+SPP] mov [CURR], EBX popa popf ret

  25. Resuming resume: pushf pusha mov EDX, [CURR] mov [EDX+SPP],ESP do_resume: mov ESP, [EBX+SPP] mov [CURR], EBX popa popf ret

  26. Resuming resume: pushf pusha mov EDX, [CURR] mov [EDX+SPP],ESP do_resume: mov ESP, [EBX+SPP] mov [CURR], EBX popa popf ret

  27. Resuming resume: pushf pusha mov EDX, [CURR] mov [EDX+SPP],ESP do_resume: mov ESP, [EBX+SPP] mov [CURR], EBX popa popf ret

  28. Resuming resume: pushf pusha mov EDX, [CURR] mov [EDX+SPP],ESP do_resume: mov ESP, [EBX+SPP] mov [CURR], EBX popa popf ret

  29. Resuming resume: pushf pusha mov EDX, [CURR] mov [EDX+SPP],ESP do_resume: mov ESP, [EBX+SPP] mov [CURR], EBX popa popf ret

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