runtimestack
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The run-time stack stores information needed for function calls such as return addresses, parameters, local variables, and CPU register states. It allows for recursive calls, variable parameters, and passing data between the caller and callee functions. The stack grows downward on x86 processors, with the top of the stack represented by the stack pointer register (SP).
![Local variables in “run-time stack”
_TEXT segment byte public 'CODE'
;
; int func(char cc,int ii,long jj)
;
assume cs:_TEXT
_func proc near
push bp
mov bp,sp
sub sp,4
;
; {
; int k=0, l=1;
;
mov word ptr [bp-2],0
mov word ptr [bp-4],1
;
; return k;
;
mov ax,word ptr [bp+6]
jmp short @1@58
@1@58:
;
; }
;
mov sp,bp
pop bp
ret
_func endp
;
; void main(void)
;
assume cs:_TEXT
_main proc near
...
_main endp
_TEXT ends
char c='a';
int i=0x1234;
long j=0x5678;
int val;
int func(char cc, int ii, long jj)
{
int k=0, l=1;
return ii;
}
void main(void)
{
val = func(c, i, j);
}
n-4
n-2
n
n+2
n+4
n+6
n+8
n+10
n+12
n+14
n+16
Return Address
.
.
.
low word of j =jj
I =ii
c =cc
bp
high word of j =jj
Return Address
sp
bpbp
?? = l
?? = k
Control
Link
bp
ENTER Instruction
LEAVE Instruction](https://image.slidesharecdn.com/06493d76-0b44-494b-b432-1d206d1957a5-170220130031/85/runtimestack-5-320.jpg)
runtimestack
- 1. Run-Time Stack • Why we can use C/C++ to write “recursive” program but not FORTRAN ? • Why we can use “variable number parameters” in C/C++ but not in other languages ? • How the parameter/return value are passed in function/procedure call ? • What are difference between local & static variables ? • Why new “ENTER/LEAVE” instruction since 80386 ? • How to correctly use the “local variables” ?
- 2. Why use “run-time stack” in languages ? • Store the following values in function calls: (communication between caller & callee) • Machine status: program counter (return address)、registers、CPU flags. • The parameters in function/procedure calls. • The data of local variables. • Control link: points to the activation record (or frame) of the caller.
- 3. Machine status in “run-time stack” void interrupt (*old_isr)(...); void interrupt new_isr(…) { (*old_isr)(); } @new_isr$qve proc far push ax push bx push cx push dx push es push ds push si push di push bp mov bp,DGROUP mov ds,bp mov bp,sp ; { ; (*old_isr)(); pushf call dword ptr DGROUP:_old_isr ; } pop bp pop di pop si pop ds pop es pop dx pop cx pop bx pop ax iret @new_isr$qve endp n-6 n-2 n n+2 n+4 n+6 n+8 n+10 n+12 n+14 n+16 n+18 n+22 n+24 CPU flags Return Address . . . ax axbx cx dx es ds si di bp sp, bp
- 4. Parameters in “run-time stack” _DATA segment word public 'DATA' _c label byte db 97 _i label word db 52,18 _j label word db 120,86,0,0 _DATA ends _TEXT segment byte public 'CODE' ; ; void main(void) ; assume cs:_TEXT _main proc near push bp mov bp,sp ; ; { ; val = func(c, i, j); ; push word ptr DGROUP:_j+2 push word ptr DGROUP:_j push word ptr DGROUP:_i mov al,byte ptr DGROUP:_c push ax call near ptr _func add sp,8 mov word ptr DGROUP:_val,ax ; ; } ; pop bp ret _main endp _TEXT ends char c='a'; int i=0x1234; long j=0x5678; int val; int func(char, int, long); void main(void) { val = func(c, i, j); } n-16 n-14 n-12 n-10 n-8 n-6 n-4 n-2 n n+2 n+4 Return Address . . . low word of j i c bp high word of j sp bp
- 5. Local variables in “run-time stack” _TEXT segment byte public 'CODE' ; ; int func(char cc,int ii,long jj) ; assume cs:_TEXT _func proc near push bp mov bp,sp sub sp,4 ; ; { ; int k=0, l=1; ; mov word ptr [bp-2],0 mov word ptr [bp-4],1 ; ; return k; ; mov ax,word ptr [bp+6] jmp short @1@58 @1@58: ; ; } ; mov sp,bp pop bp ret _func endp ; ; void main(void) ; assume cs:_TEXT _main proc near ... _main endp _TEXT ends char c='a'; int i=0x1234; long j=0x5678; int val; int func(char cc, int ii, long jj) { int k=0, l=1; return ii; } void main(void) { val = func(c, i, j); } n-4 n-2 n n+2 n+4 n+6 n+8 n+10 n+12 n+14 n+16 Return Address . . . low word of j =jj I =ii c =cc bp high word of j =jj Return Address sp bpbp ?? = l ?? = k Control Link bp ENTER Instruction LEAVE Instruction