I am trying to convert a C code (which reads number from stdin and compute the Fibonacci value of a number but the content of the code is no so important for the problem) to a nasm code using this Link: https://stackoverflow.com/a/20743090/9557460 but at step 3 when I put the command
nasm -f elf64 main.asm
I get
main.asm:45: error: symbol `?_001' undefined
main.asm:106: error: symbol `?_001' undefined
for some reason ?_001 is not defined but it is used in the code. and when removing it manually the code doesnt work.
The C code:
#include <stdio.h>
#include <stdlib.h>
#define MAX_PHYSICAL_MEMORY 500
static long M[MAX_PHYSICAL_MEMORY] = {
};
int main()
{
for (int i=0; i<MAX_PHYSICAL_MEMORY; i++){//taking the numbers from an array
scanf("%ld", &M[i]);
}
int i = 0;
//char *format;
while (M[i] || M[i + 1] || M[i + 2]){//this is the sic program
if ((M[M[i]] -= M[M[i + 1]]) < 0)
i = M[i + 2];
else
i += 3;
}
for (i = 0; i < MAX_PHYSICAL_MEMORY; ++i) {//it is just do the printing
printf("%ld ", M[i]);
}
printf("\n");
return 0;
}
the NASM code generated :
; Disassembly of file: main.o
; Tue May 22 11:34:20 2018
; Mode: 64 bits
; Syntax: YASM/NASM
; Instruction set: Pentium Pro, x64
default rel
global main
extern putchar ; near
extern __printf_chk ; near
extern __isoc99_scanf ; near
SECTION .text ; section number 1, code
SECTION .data ; section number 2, data
SECTION .bss ; section number 3, bss
M: ; byte
resq 500 ; 0000
SECTION .rodata.str1.1 ; section number 4, const
?_002: ; byte
db 25H, 6CH, 64H, 00H ; 0000 _ %ld.
?_003: ; byte
db 25H, 6CH, 64H, 20H, 00H ; 0004 _ %ld .
SECTION .text.unlikely ; section number 5, code
SECTION .text.startup ; section number 6, code
main: ; Function begin
push r12 ; 0000 _ 41: 54
push rbp ; 0002 _ 55
mov r12d, ?_001 ; 0003 _ 41: BC, 00000000(d)
push rbx ; 0009 _ 53
mov ebx, M ; 000A _ BB, 00000000(d)
mov rbp, rbx ; 000F _ 48: 89. DD
; Filling space: 6H
; Filler type: Multi-byte NOP
; db 66H, 0FH, 1FH, 44H, 00H, 00H
ALIGN 8
?_004: mov rsi, rbp ; 0018 _ 48: 89. EE
xor eax, eax ; 001B _ 31. C0
mov edi, ?_002 ; 001D _ BF, 00000000(d)
add rbp, 8 ; 0022 _ 48: 83. C5, 08
call __isoc99_scanf ; 0026 _ E8, 00000000(rel)
cmp r12, rbp ; 002B _ 49: 39. EC
jnz ?_004 ; 002E _ 75, E8
xor eax, eax ; 0030 _ 31. C0
; Filling space: 6H
; Filler type: Multi-byte NOP
; db 66H, 0FH, 1FH, 44H, 00H, 00H
ALIGN 8
?_005: movsxd rdx, eax ; 0038 _ 48: 63. D0
; Note: Address is not rip-relative
mov rcx, qword [abs M+rdx*8] ; 003B _ 48: 8B. 0C D5, 00000000(d)
lea edx, [rax+1H] ; 0043 _ 8D. 50, 01
movsxd rdx, edx ; 0046 _ 48: 63. D2
test rcx, rcx ; 0049 _ 48: 85. C9
; Note: Address is not rip-relative
mov rsi, qword [abs M+rdx*8] ; 004C _ 48: 8B. 34 D5, 00000000(d)
jnz ?_006 ; 0054 _ 75, 16
test rsi, rsi ; 0056 _ 48: 85. F6
jnz ?_006 ; 0059 _ 75, 11
lea edx, [rax+2H] ; 005B _ 8D. 50, 02
movsxd rdx, edx ; 005E _ 48: 63. D2
; Note: Address is not rip-relative
cmp qword [abs M+rdx*8], 0 ; 0061 _ 48: 83. 3C D5, 00000000(d), 00
jz ?_007 ; 006A _ 74, 24
?_006:
; Note: Address is not rip-relative
mov rdx, qword [abs M+rcx*8] ; 006C _ 48: 8B. 14 CD, 00000000(d)
; Note: Address is not rip-relative
sub rdx, qword [abs M+rsi*8] ; 0074 _ 48: 2B. 14 F5, 00000000(d)
test rdx, rdx ; 007C _ 48: 85. D2
; Note: Address is not rip-relative
mov qword [abs M+rcx*8], rdx ; 007F _ 48: 89. 14 CD, 00000000(d)
js ?_008 ; 0087 _ 78, 3F
add eax, 3 ; 0089 _ 83. C0, 03
jmp ?_005 ; 008C _ EB, AA
; Filling space: 2H
; Filler type: NOP with prefixes
; db 66H, 90H
ALIGN 8
?_007: mov rdx, qword [rbx] ; 0090 _ 48: 8B. 13
xor eax, eax ; 0093 _ 31. C0
mov esi, ?_003 ; 0095 _ BE, 00000000(d)
mov edi, 1 ; 009A _ BF, 00000001
add rbx, 8 ; 009F _ 48: 83. C3, 08
call __printf_chk ; 00A3 _ E8, 00000000(rel)
cmp rbx, ?_001 ; 00A8 _ 48: 81. FB, 00000000(d)
jnz ?_007 ; 00AF _ 75, DF
mov edi, 10 ; 00B1 _ BF, 0000000A
call putchar ; 00B6 _ E8, 00000000(rel)
pop rbx ; 00BB _ 5B
xor eax, eax ; 00BC _ 31. C0
pop rbp ; 00BE _ 5D
pop r12 ; 00BF _ 41: 5C
ret ; 00C1 _ C3
; Filling space: 6H
; Filler type: Multi-byte NOP
; db 66H, 0FH, 1FH, 44H, 00H, 00H
ALIGN 8
?_008: add eax, 2 ; 00C8 _ 83. C0, 02
cdqe ; 00CB _ 48: 98
; Note: Address is not rip-relative
mov eax, dword [abs M+rax*8] ; 00CD _ 8B. 04 C5, 00000000(d)
jmp ?_005 ; 00D4 _ E9, FFFFFF5F
; main End of function
