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2011. 10. 25최 윤 정

2

PointBinary / Hexadecimal / DecimalGrammar in C language

- %d %f %lf %u %x %p …

- *, &

Floating Point FormatStack Structure

3

: Chap.2 & C 의 기본문법(1/4)1) 0x502c + 64 = 0x502c + 0x40 = 0x506c, %x 출력형태는

506c

2) 0x50da + 0x502c = 0xa106 , %x 출력형태는 a106

3) x = 0xFFFFFF0, x<<3 ?

X = 00001111……11110000 , X<<3 = 00001111……….111 1000 0000, ∴

7FFFFFF80

4) unsigned int x = 0xFFFFFFF0, x>>2 ?

Arithmetic shift vs. Logical shift

X = 1111 ………. 0000, X >> 2 = 001111……….1111 0000, ∴ 3FFFFFFC

4

Page 3 : Chap.2 & C 의 기본문법 (2/4)

5) int x = 0x15213F10 >> 4; // 즉 0x015213F1

char y = (char) x // y = 0xF1 unsigned char z = (unsigned char) x; z = 0xF1

F1 = 11110001,

signed = -x7(27) + (x6(26) + … x0(20)) = -128 +(64+32+16+1)= -15

unsigned = x7(27) + x6(26) + … x0(20) = 128+64+32+16+1 = 241

6) float x = 31/8 ; float y = 31/8.0;

Arithmetic : 31/8 = 3.875, but , integer 31 / interger 8 = 3, (∵ 11111 >> 3)

(float) 31/ 8.0 = 3.875

5

Page 3 : Chap.2 & C 의 기본문법 (3/4)

7) n-bit signed integer 의 범위 : -2n-1 ~ 0 ~ 2n-1 - 1

n-bit unsigned integer 의 범위 : 0 ~ 2n – 1 Two’s complement 에서 , 즉 , signed integer 로 -1 과 1 을 표현하는 필요한 bit

size

-1 : -21-0 n = 1, 1bit 1 : 2-1 = 22-1 - 1 = 1, 2bit

8) 4 page 에서

9) 15213U > -1 15213U >(unsigned) -1 ,15213U > FFFFFFFF ? false ∴ 0.

10) INT_MIN == TMIN 1000 …. 0000, 32bit 에서 , 800000000 -INT_MIN = INT_MAX + 1 INT_MIN 즉 , 800000000

6

Page 3 : Chap.2 & C 의 기본문법(4/4)

11) , 12) : a - n = ~ n + 1, ~(0000101101) + 1 = 1111010010 +1 = 1111010011

13) %eax

14) sizeof(char) + sizeof(int) + sizeof(void *) + sizeof(int *) IA32 : 1 + 4 + 4 + 4 = 13, Intel x86_64 : 1 + 4 + 8 + 8 = 21 , sizeof(int) =4, sizeof(long int) = 8. 그러나 , linux 의 버전과 compiler 별 차이를 분명히 명시하지 않았던 점으로 인하여 sizeof(int) = 8 로 계산한

1 + 8 + 8 + 8 = 25 의 답도 인정함 .

15) Lea vs. Mov, Lea : 0x10(%eax, %ecx, 4) , %eax %eax = 16+ %eax + 4*%ecx Mov : 0x10(%eax, %ecx, 4) , %eax %eax = *(16 + %eax + 4*%ecx )

16) #include <stdio.h>

int main(){

int x = 0;

printf("Please input an inte-

ger:");

scanf("%d", x );

printf("%d", (!!x)<<31);

}

7

Page 4 : Chap.2 – Floating Point Format

Description Binary exp M E V

Fraction number 0 010 010 2 5/4 -1 5/8

2 3/8 0 100 010 4 5/4 1 5/2

-infinity 1 111 000 7 - - -Largest Positive

Norm. 0 110 111 6 15/8 3 15Smallest Negative

Norm. 1 110 111 6 15/8 3 -15Largest Negative

Norm. 1 001 000 1 1 -2 -1/4

1 0 011 000 3 1 0 1Smallest Positive

Norm. 0 001 000 1 1 -2 1/4Largest Positive

DeNorm. 0 000 001 0 7/8 -2 7/32Smallest Positive

DeNorm. 0 000 111 0 1/8 -2 1/32

7-bit floating point representation based on the IEEE floating point • There is a sign bit in the most significant bit.• The next 3 bits are the exponent. The exponent bias is 3.• The last 3 bits are the fraction.

V = (-1)s * M * 2E M is the significand and E the integer value of the exponent

E = exp - Bias (norm.)E = 1 - Bias ( denorm.)

2 와 3/8 = 10.011 (-1) 0 * 1.0011 * 21

따라서 , s = 0E = 1M = 1.0011, exp = 3 +1 = 4frac. = 010

( ∵ 소수부 0011 의 3bit 를 취할 때 , round-to-even 적용 )

exp frac.

0 000 000

8

Page 3. 8) ¼ - bit representa-tion in IEEE 754 IEEEE 754 = 1 sign bit, 8 exp bits , 23

frac. bits Bias = 2 8-1 – 1 = 2 7 – 1 = 127 , sign bit = 0. ¼ = 0.01 (-1) 0 * 1.0 * 2 -2

exp = Bias + E = 127 + (-2) = 125, 0111 1101 frac = 0000 …. 0000 ∴ 0 01111101 0000…0000 = 3 E 8 0 0 0 0 0

9

IA32 Stack Region of memory managed

with stack discipline Grows toward lower addresses

Register %esp contains lowest stack address address of “top” element

Push : %esp = %esp – 4 Pop : %esp = %esp + 4 Call Procedure :

push next address(Return address)

Stack Pointer: %esp

Stack GrowsDown

IncreasingAddresses

Stack “Top”

Stack “Bottom”

%esp

%eip 0x804854e

0x108

0x10c

0x110

123

.

.

.

.

0x108

ex) call 0x8048b90(Next addr = 0x8048553)

0x80485530x104

0x104

0x8048b90

10

9*9 단 inline - assembly code 에서 void print(int x, int y);

..".Lp3 : " "movl %1, 4(%%esp) " "movl %0, (%%esp) " "call print " //0x804b90 "movl 4(%%esp), %1" "movl (%%esp), %0 " ...

:"r" (i), "r" (j)..

%esp

%ebp

%eip 0x804b1100

0x108

0x10c

0x1100x804854e

.

.

.

.

0x108

call 8048b90

%ebx

%edx j

i

%eax 0x804b1204

%esp

11



:"r" (i), "r" (j)..

%esp

%ebp

%eip 0x804b1200

0x108

0x10c

0x1100x804854e

.

.

.

.

0x108

call 8048b90

%ebx

%edx j

i

%eax 0x804b1204

i

j

%esp

12



:"r" (i), "r" (j)..

0x804b1204

0x108

0x10c

0x110

0x104

i

.

.

.

.

call 8048b90

j

%esp

%esp

%ebp

%eip 0x804b90

0x804854e

0x104

%ebx

%edx j

i

%eax 0x804b1204

13



:"r" (i), "r" (j)..

0x804b1204

0x108

0x10c

0x110

0x104

i

.

.

.

.

call 8048b90

j

%esp0x804854e0x100

%esp

%ebp

%eip 0x804b90+a

0x100

%ebx

%edx j

i

%eax ...

0x804854e

//setup code in func. print

pushl %ebpmovl %esp, %ebp…

14



:"r" (i), "r" (j)..

0x804b1204

0x108

0x10c

0x110

0x104

i

.

.

.

.

call 8048b90

j

%ebp0x100 %esp

%esp

%ebp

%eip 0x804b90+b

0x100

%ebx

%edx j

i

%eax ...

0x100

0x804854e

//setup code in func. print

pushl %ebpmovl %esp, %ebp…

pop %ebp

15



:"r" (i), "r" (j)..

0x804b1204

0x108

0x10c

0x110

0x104

i

.

.

.

.

call 8048b90

j

%esp

%esp

%ebp

%eip 0x804b90+c

0x104

%ebx

%edx j

i

%eax ...

0x804854e

//return from func. print

…

pop %ebp

16



:"r" (i), "r" (j)..

0x108

0x10c

0x110

i

.

.

.

.

call 8048b90

j

%esp

%esp

%ebp

%eip 0x804b1204

0x108

%ebx

%edx j

i

%eax ...

0x804854e

17

#include <stdio.h>void gugu_for();void gugu_no_loop();void println(){ printf("\n");}void print(int x, int y){ printf("%2d x %2d = %2d \n", x, y, x*y);}void gugu_for(){ int a, sum, i, j; a = 1; for ( i=1; i<=9; i++){ for(j=1; j<=9; j++){

__asm__ __volatile__("movl %1, %0 \n\t""imull %2, %0 \n\t""movl %2, 4(%%esp) \n\t""movl %1, (%%esp) \n\t""call print": "=g" (sum):"r" (i), "r" (j));// printf("%d x %d = sum=%d \n", i, j,

sum); }printf("\n"); }

}

void gugu_no_loop(){int i=0, j=0;__asm__ __volatile__(

"movl $0, %0 \n\t""movl $0, %1 \n\t"

".Lp1 : " "cmpl $9, %0 \n\t""jge .End \n\t""incl %0 \n\t"

".Lp2 : " "cmpl $9, %1 \n\t""jl .Lp4 \n\t""movl $0, %1 \n\t""movl %1, 4(%%esp) \n\t""movl %0, (%%esp) \n\t""call println \n\t""movl 4(%%esp), %1 \n\t""movl (%%esp), %0 \n\t""jmp .Lp1 \n\t"

".Lp3 : " "movl %1, 4(%%esp) \n\t""movl %0, (%%esp) \n\t""call print \n\t""movl 4(%%esp), %1 \n\t""movl (%%esp), %0 \n\t""jmp .Lp2 \n\t"

".Lp4 : " "incl %1 \n\t""jmp .Lp3 \n\t"

".End : " "movl $0, %1 \n\t"::"r" (i), "r" (j));

}

18

Page 4 : Chap. 3 – Stack&Assembly코드의 이해

…

Stack%ebp

%espfunc1

%ebp

%espfunc2

%ebp

%espfunc3

%ebp

%esp

%esp

%ebp 0x100

0x100

%eax

%edx

pushl %ebp movl %esp,

%ebp movl 8(%ebp),

%edx movl 12(%ebp),

%eax movl %ebp,

%esp movl (%edx),

%edx addl %edx,

(%eax) movl %edx,

%eax popl %ebp ret

%esp%ebp

200

300

Old ebp

Rtn addr0x104

0x1080x10c

0x100

1

20x200

0x300

19


%esp

%ebp 0x100

0x100

%eax

%edx


%ebp movl 8(%ebp),

%edx movl 12(%ebp),

%eax movl %ebp,

%esp movl (%edx),

%edx addl %edx,

(%eax) movl %edx,

%eax popl %ebp ret

%esp%ebp

200

300

Old ebp

Rtn addr0x104

0x1080x10c

0x100

*(0x100+8)200

*(0x100+c)

300

1

20x200

0x300

20



%ebp movl 8(%ebp),

%edx movl 12(%ebp),

%eax movl %ebp,

%esp movl (%edx),

%edx addl %edx,

(%eax) movl %edx,

%eax popl %ebp ret

%esp

%ebp 0x100

0x100

%eax

%edx *(0x100+8)200

*(0x100+c)

300

%esp%ebp

200

1

Old ebp

Rtn addr0x104

0x1080x10c

0x100

0x200

0x300

2

300

21



%ebp movl 8(%ebp),

%edx movl 12(%ebp),

%eax movl %ebp,

%esp movl (%edx),

%edx addl %edx,

(%eax) movl %edx,

%eax popl %ebp ret

%esp

%ebp 0x100

0x100

%eax

%edx 2

*(0x100+c)

300

%esp%ebp

200

1

Old ebp

Rtn addr0x104

0x1080x10c

0x100

0x200

0x300

2

300

22



%ebp movl 8(%ebp),

%edx movl 12(%ebp),

%eax movl %ebp,

%esp movl (%edx),

%edx addl %edx,

(%eax) movl %edx,

%eax popl %ebp ret

%esp

%ebp 0x100

0x100

%eax

%edx 2

*(0x100+c)

300

%esp%ebp

200

1+2

Old ebp

Rtn addr0x104

0x1080x10c

0x100

0x200

0x300

2

300

23



%ebp movl 8(%ebp),

%edx movl 12(%ebp),

%eax movl %ebp,

%esp movl (%edx),

%edx addl %edx,

(%eax) movl %edx,

%eax popl %ebp ret

%esp

%ebp 0x100

0x100

%eax

%edx 2

2

%esp%ebp

200

1+2

Old ebp

Rtn addr0x104

0x1080x10c

0x100

0x200

0x300

2

300

24



%ebp movl 8(%ebp),

%edx movl 12(%ebp),

%eax movl %ebp,

%esp movl (%edx),

%edx addl %edx,

(%eax) movl %edx,

%eax popl %ebp ret

%esp

%ebp Old ebp

0x104

%eax

%edx *(0x100+8)200

*(0x100+c)

300

%esp

200

300

Rtn addr0x104

0x1080x10c

Old ebp

1

20x200

0x300

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