Practical Session 9Co-Routines

Co-Routines

Co-routine state

Variable DeclerationSTKSZ equ 16*1024CODEP equ 0FLAGSP equ 4SPP equ 8

section .rodataalign 16global numco

numco: dd 3CORS: dd CO1

dd CO2dd CO3

section .dataalign 16

; Structure for first co-routineCO1: dd Function1Flags1: dd 0SP1: dd STK1+STKSZ; Structure for second co-routineCO2: dd Function1Flags2: dd 0SP2: dd STK2+STKSZ; Structure for third co-routineCO3: dd Function2Flags3: dd 0SP3: dd STK3+STKSZ; CounterCOUNTER: dd 0MAX_ITER: dd 3

section .bssalign 16

CURR: resd 1SPT: resd 1SPMAIN: resd 1STK1: resb STKSZSTK2: resb STKSZSTK3: resb STKSZ

Co-routine structure

Co-routine structure

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

Initializtion

section .textalign 16extern printfglobal init_co_from_cglobal start_co_from_cglobal end_co

; Initalize a co-routine number given as an argument from Cinit_co_from_c:

push EBPmov EBP, ESPpush EBXmov EBX, [EBP+8]mov EBX, [EBX*4+CORS]call co_initpop EBXpop EBPret

; EBX is pointer to co-routine structure to initializeco_init:

pushabts dword [EBX+FLAGSP],0 ; test if already initializedjc init_donemov EAX,[EBX+CODEP] ; Get initial PCmov [SPT], ESPmov ESP,[EBX+SPP] ; Get initial SPmov EBP, ESP ; Also use as EBPpush EAX ; Push initial "return" addresspushf ; and flagspusha ; and all other regsmov [EBX+SPP],ESP ; Save new SP in structuremov ESP, [SPT] ; Restore original SP

init_done:poparet

Co-routine initialization

Co-routine initialization

Co-routine initialization

Function1; This function used as code for co-routines 0 and 1Function1:

push dword 0push dword 1push dword [CORS+8]push dword [CURR]push dword FMT1call printfadd ESP, 20mov EBX, [CORS+8]call dword resumemov dword [COUNTER], 0

func1_loop:push dword [COUNTER]push dword 2push dword [CORS+8]push dword [CURR]push dword FMT1call printfadd ESP, 20add dword [COUNTER], 1mov eax, [MAX_ITER]cmp [COUNTER], eaxjne func1_loop mov EBX, [CORS+8]call dword resumejmp end_co

Function2; This function used as code for co-routine 2Function2:

push dword 0push dword 1push dword [CORS]push dword [CURR]push dword FMT2call printfadd ESP, 16mov EBX, [CORS]call dword resumemov dword [COUNTER], 0

func2_loop:push dword [COUNTER]push dword 2push dword [CORS+4]push dword [CURR]push dword FMT2call printfadd ESP, 20

add dword [COUNTER], 1mov eax, [MAX_ITER]cmp [COUNTER], eaxjne func2_loopmov EBX, [CORS+4]call dword resumepush dword 3push dword [CORS]push dword [CURR]push dword FMT2call printfadd ESP, 16mov EBX, [CORS]call dword resumepush dword 4push dword [CORS+4]push dword [CURR]push dword FMT2call printfadd ESP, 16mov EBX, [CORS+4]call dword resumejmp end_co

Co-routine code (function)

Co-routine code (function)

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-routineresume:

pushf ; Save state of callerpushamov EDX, [CURR]mov [EDX+SPP],ESP; Save current SP

do_resume:mov ESP, [EBX+SPP] ; Load SP for resumed co-routinemov [CURR], EBXpopa ; Restore resumed co-routine statepopfret ; "return" to resumed co-routine!

Co-routine resume

Co-routine resume

Start and End; C-callable start of the first co-routinestart_co_from_c:

push EBPmov EBP, ESPpushamov [SPMAIN], ESP ; Save SP of main codemov EBX, [EBP+8] ; Get number of co-routinemov EBX, [EBX*4+CORS] ; and pointer to co-routine structurejmp do_resume

; End co-routine mechanism, back to C mainend_co:

mov ESP, [SPMAIN] ; Restore state of main codepopapop EBPret

Start Co-routine scheduler

ExampleCURR

SPT

SPMAIN

STK1

STK2

STK3

numco

CORS

Function1 CO1

0 Flags1

SP1

Function1 CO2

0 Flags2

SP2

Function2 CO3

0 Flags3

SP3

0 COUNTER

3 MAX_ITER

After InitCURR

SPT

SPMAIN

STK1

Registers

Flags

Function1

STK2

Registers

Flags

Function1

STK3

Registers

Flags

Function2

numco

CORS

Function1 CO1

1 Flags1

SP1

Function1 CO2

1 Flags2

SP2

Function2 CO3

1 Flags3

SP3

0 COUNTER

3 MAX_ITER

ResumingCO2 CURR

SPT

SPMAIN

STK1

Registers

Flags

Addr1

STK2

ESP ……….

……….

STK3

Registers

Flags

Addr3

numco

CORS

Function1 CO1

1 Flags1

SP1

Function1 CO2

1 Flags2

SP2

Function2 CO3

1 Flags3

SP3

0 COUNTER

3 MAX_ITER

resume:pushf

pushamov EDX, [CURR]mov [EDX+SPP],ESP

do_resume:mov ESP, [EBX+SPP] mov [CURR], EBXpopapopfret

Resuming – Resume is CalledCO2 CURR

SPT

SPMAIN

STK1

Registers

Flags

Addr1

STK2

ESP Addr2

……….

……….

STK3

Registers

Flags

Addr3

numco

CORS

Function1 CO1

1 Flags1

SP1

Function1 CO2

1 Flags2

SP2

Function2 CO3

1 Flags3

SP3

0 COUNTER

3 MAX_ITER

resume:pushf

pushamov EDX, [CURR]mov [EDX+SPP],ESP

do_resume:mov ESP, [EBX+SPP] mov [CURR], EBXpopapopfret

ResumingCO2 CURR

SPT

SPMAIN

STK1

Registers

Flags

Addr1

ESP Registers STK2

Flags

Addr2

……….

……….

STK3

Registers

Flags

Addr3

numco

CORS

Function1 CO1

1 Flags1

SP1

Function1 CO2

1 Flags2

SP2

Function2 CO3

1 Flags3

SP3

0 COUNTER

3 MAX_ITER

resume:pushf

pushamov EDX, [CURR]mov [EDX+SPP],ESP

do_resume:mov ESP, [EBX+SPP] mov [CURR], EBXpopapopfret

ResumingCO2 CURR

SPT

SPMAIN

STK1

Registers

Flags

Addr1

ESP Registers STK2

Flags

Addr2

……….

……….

STK3

Registers

Flags

Addr3

numco

CORS

Function1 CO1

1 Flags1

SP1

Function1 CO2

1 Flags2

SP2

Function2 CO3

1 Flags3

SP3

0 COUNTER

3 MAX_ITER

resume:pushf

pushamov EDX, [CURR]mov [EDX+SPP],ESP

do_resume:mov ESP, [EBX+SPP] mov [CURR], EBXpopapopfret

ResumingCO2 CURR

SPT

SPMAIN

STK1

Registers

Flags

Addr1

Registers STK2

Flags

Addr2

……….

……….

STK3

ESP Registers

Flags

Addr3

numco

CORS

Function1 CO1

1 Flags1

SP1

Function1 CO2

1 Flags2

SP2

Function2 CO3

1 Flags3

SP3

0 COUNTER

3 MAX_ITER

resume:pushf

pushamov EDX, [CURR]mov [EDX+SPP],ESP

do_resume:mov ESP,

[EBX+SPP] mov [CURR], EBXpopapopfret

ResumingCO3 CURR

SPT

SPMAIN

STK1

Registers

Flags

Addr1

Registers STK2

Flags

Addr2

……….

……….

STK3

ESP Registers

Flags

Addr3

numco

CORS

Function1 CO1

1 Flags1

SP1

Function1 CO2

1 Flags2

SP2

Function2 CO3

1 Flags3

SP3

0 COUNTER

3 MAX_ITER

resume:pushf

pushamov EDX, [CURR]mov [EDX+SPP],ESP

do_resume:mov ESP, [EBX+SPP] mov [CURR], EBXpopapopfret

ResumingCO3 CURR

SPT

SPMAIN

STK1

Registers

Flags

Addr1

Registers STK2

Flags

Addr2

……….

……….

STK3

ESP Addr3

numco

CORS

Function1 CO1

1 Flags1

SP1

Function1 CO2

1 Flags2

SP2

Function2 CO3

1 Flags3

SP3

0 COUNTER

3 MAX_ITER

resume:pushf

pushamov EDX, [CURR]mov [EDX+SPP],ESP

do_resume:mov ESP, [EBX+SPP] mov [CURR], EBXpopapopfret