问题
I'm trying to compile this x86 assembly code on x64 Debian :
BITS 32
%include 'training.s'
global main
extern exit
; ===============================================
section .text
main:
; The program begins here:
call read_hex
mov edx,eax
call read_hex
add eax,edx
add eax,eax
inc eax
call print_eax
; Exit the process:
push 0
call exit
I'm getting these errors:
~$nasm -f elf -g 0_strange_calc.asm && ld -o 0_strange_calc 0_strange_calc.o
ld: i386 architecture of input file `0_strange_calc.o' is incompatible with i386:x86-64 output
ld: warning: cannot find entry symbol _start; defaulting to 00000000004000b0
0_strange_calc.o:training.s:25: undefined reference to `printf'
0_strange_calc.o:training.s:35: undefined reference to `printf'
0_strange_calc.o:training.s:45: undefined reference to `printf'
0_strange_calc.o:training.s:56: undefined reference to `read'
0_strange_calc.o:training.s:77: undefined reference to `scanf'
0_strange_calc.o:training.s:97: undefined reference to `scanf'
0_strange_calc.o:training.s:108: undefined reference to `printf'
0_strange_calc.o:training.s:129: undefined reference to `printf'
0_strange_calc.o:training.s:137: undefined reference to `printf'
0_strange_calc.o:0_strange_calc.asm:50: undefined reference to `exit'
~$ yasm -f elf64 0_strange_calc.asm
~$ gcc -m32 -nostdlib -nostdinc 0_strange_calc.o -o 0_strange_calc
/usr/bin/ld: i386:x86-64 architecture of input file `0_strange_calc.o' is incompatible with i386 output
/usr/bin/ld: warning: cannot find entry symbol _start; defaulting to 00000000080480c0
0_strange_calc.o: In function `no symbol':
0_strange_calc.asm:(.text+0x8): undefined reference to `printf'
0_strange_calc.asm:(.text+0x19): undefined reference to `printf'
0_strange_calc.asm:(.text+0x2a): undefined reference to `printf'
0_strange_calc.asm:(.text+0x39): undefined reference to `read'
0_strange_calc.asm:(.text+0x5b): undefined reference to `scanf'
0_strange_calc.asm:(.text+0x7a): undefined reference to `scanf'
0_strange_calc.asm:(.text+0x89): undefined reference to `printf'
0_strange_calc.asm:(.text+0xa8): undefined reference to `printf'
0_strange_calc.asm:(.text+0xb9): undefined reference to `printf'
0_strange_calc.o: In function `main':
0_strange_calc.asm:(.text+0xdb): undefined reference to `exit'
collect2: error: ld returned 1 exit status
This is my dump of 0_strange_calc.o:
~$ objdump -M intel -d 0_strange_calc.o
0_strange_calc.o: file format elf64-x86-64
Disassembly of section .text:
0000000000000000 <main-0xc2>:
0: 60 (bad)
1: 50 push rax
2: 68 00 00 00 00 push 0x0
7: e8 00 00 00 00 call c <main-0xb6>
c: 83 c4 08 add esp,0x8
f: 61 (bad)
10: c3 ret
11: 60 (bad)
12: 50 push rax
13: 68 00 00 00 00 push 0x0
18: e8 00 00 00 00 call 1d <main-0xa5>
1d: 83 c4 08 add esp,0x8
20: 61 (bad)
21: c3 ret
22: 60 (bad)
23: b8 00 00 00 00 mov eax,0x0
28: 50 push rax
29: e8 00 00 00 00 call 2e <main-0x94>
2e: 83 c4 04 add esp,0x4
31: 61 (bad)
32: c3 ret
33: 60 (bad)
34: 51 push rcx
35: 57 push rdi
36: 6a 00 push 0x0
38: e8 00 00 00 00 call 3d <main-0x85>
3d: 83 c4 0c add esp,0xc
40: 31 d2 xor edx,edx
42: c6 04 07 00 mov BYTE PTR [rdi+rax*1],0x0
46: 61 (bad)
47: c3 ret
48: 55 push rbp
49: 89 e5 mov ebp,esp
4b: 83 ec 04 sub esp,0x4
4e: 53 push rbx
4f: 51 push rcx
50: 52 push rdx
51: 8d 5d fc lea ebx,[rbp-0x4]
54: 53 push rbx
55: 68 00 00 00 00 push 0x0
5a: e8 00 00 00 00 call 5f <main-0x63>
5f: 83 c4 08 add esp,0x8
62: 8b 03 mov eax,DWORD PTR [rbx]
64: 5a pop rdx
65: 59 pop rcx
66: 5b pop rbx
67: c9 leave
68: c3 ret
69: 55 push rbp
6a: 89 e5 mov ebp,esp
6c: 83 ec 04 sub esp,0x4
6f: 8d 5d fc lea ebx,[rbp-0x4]
72: 60 (bad)
73: 53 push rbx
74: 68 00 00 00 00 push 0x0
79: e8 00 00 00 00 call 7e <main-0x44>
7e: 83 c4 08 add esp,0x8
81: 61 (bad)
82: 8b 03 mov eax,DWORD PTR [rbx]
84: c9 leave
85: c3 ret
86: 60 (bad)
87: 56 push rsi
88: e8 00 00 00 00 call 8d <main-0x35>
8d: 83 c4 04 add esp,0x4
90: 61 (bad)
91: c3 ret
92: 60 (bad)
93: b9 20 00 00 00 mov ecx,0x20
98: d1 c0 rol eax,1
9a: 89 c2 mov edx,eax
9c: 83 e2 01 and edx,0x1
9f: 51 push rcx
a0: 50 push rax
a1: 52 push rdx
a2: 68 00 00 00 00 push 0x0
a7: e8 00 00 00 00 call ac <main-0x16>
ac: 83 c4 08 add esp,0x8
af: 58 pop rax
b0: 59 pop rcx
b1: e2 e5 loop 98 <main-0x2a>
b3: 68 00 00 00 00 push 0x0
b8: e8 00 00 00 00 call bd <main-0x5>
bd: 83 c4 04 add esp,0x4
c0: 61 (bad)
c1: c3 ret
00000000000000c2 <main>:
c2: e8 81 ff ff ff call 48 <main-0x7a>
c7: 89 c2 mov edx,eax
c9: e8 7a ff ff ff call 48 <main-0x7a>
ce: 01 d0 add eax,edx
d0: 01 c0 add eax,eax
d2: 40 e8 28 ff ff ff rex call 0 <main-0xc2>
d8: 6a 00 push 0x0
da: e8 00 00 00 00 call df <main+0x1d>
It seems to have been converted successfully in x64 asm, other simple code I had compiled and linked without problems. What am I doing wrong? And how can I fix it?
回答1:
You have a couple of options
- Use LD to link to a final executable
- Use GCC to link to a final executable
Using LD Method
Your command lines use LD, unfortunately that presents a number of problems. The first:
ld: i386 architecture of input file `0_strange_calc.o' is incompatible with i386:x86-6
You are on 64-bit Debian, trying to produce a 32-bit executable. -f elf on the NASM command line generates 32-bit ELF (-f elf64 generate 64 bit objects). Your LD command line is by default trying to generate a 64-bit executable thus the error above is given. You can force LD to generate a 32-bit executable by adding the -m elf_i386 option to LD's command line.
ld: warning: cannot find entry symbol _start; defaulting to 00000000004000b0
You should tell LD that your entry point is main . LD by default looks for an entry point of _start. You can add -e main to the LD command line to resolve that.
Errors like this suggest you need the C library (where printf exists):
0_strange_calc.asm:(.text+0x8): undefined reference to `printf'
Since your code doesn't use printf directly I can only assume that is required by the functions in training.s . In order to link in the C library you will need to add it after the .o files in your command line. You can do this with -lc on your LD command line. You'll also need to tell LD specifically what dynamic linker library you will need to use (In this case a 32-bit one). In a Debian environment that will usually look like: -dynamic-linker /lib/ld-linux.so.2
So your NASM and LD lines should look like this:
nasm -f elf -g 0_strange_calc.asm
ld -melf_i386 -e main -dynamic-linker /lib/ld-linux.so.2 -o 0_strange_calc 0_strange_calc.o -lc
Using GCC Method
You can simplify linking to the C library by using GCC to link you your object file to an executable. To build a 32-bit executable you could use:
nasm -f elf -g 0_strange_calc.asm
gcc -m32 0_strange_calc.o -o 0_strange_calc
The C library and runtime has a _start method that does C startup initialization and in turn calls a function called main which happens to be the function in your assembly file. -m32 tells GCC you are also linking to a 32-bit executable.
Special Considerations
You may also need to to install the Multlilib versions of gcc (and g++ if you want to) so that you can properly build and run 32-bit applications on 64-bit Debian using the appropriate C libraries. That can be done with this command line:
apt-get install gcc-multilib g++-multilib
On Ubuntu based systems you'd need to use:
sudo apt-get install gcc-multilib g++-multilib
回答2:
Note that the problem is not the asm code but a missing imported function. If you read
training.s you will see the definition of printeax and other methods as well. Moreover you will see that some of those method use external function like printf which is of course not asm function but some imported language lib
BITS 32
extern printf
extern exit
extern scanf
extern read
So in order to make it work - i.e to find those external libs ( you have also warning there that you should handle but this is out of this scope). You need to use the linker properly. According to Frank at the nasm board you have two options
use the
ldlinker but tell it to useclib vialcoptions. i.e:ld -ld -o 0_strange_calc 0_strange_calc.o -lc. More info can be found hereuse the
gcclinker.
P.S
Note that also the code uses 32bit which on your computer produce a warning as you can use 64 bit and you use elf flag. More on it you can find at the nasm docs
来源：https://stackoverflow.com/questions/34374591/linking-an-assembler-program-error-undefined-reference-to-printf