链接时已编译的gcc .s代码存在问题 [英] Problems with compiled gcc .s Code when linking

问题描述

第一次在这里，我运行的是Kali linux 64bits，我是linux新秀，也是ASM的新手....于是我用C语言编写了一个代码，它工作得非常好....这里是代码:

First time here, Im running Kali linux 64bits ,Im a linux rookie and a new to ASM aswell.... So I pulled a code in C ,the wich works perfectly fine..... here is the code:

#include<stdio.h>
#include<string.h>    //strlen
#include<sys/socket.h>
#include<arpa/inet.h> //inet_addr

int main(int argc , char *argv[])
{
int socket_desc;
struct sockaddr_in server;
char *message , server_reply[2000];

//Create socket
socket_desc = socket(AF_INET , SOCK_STREAM , 0);
if (socket_desc == -1)
{
    printf("Could not create socket");
}

server.sin_addr.s_addr = inet_addr("127.0.0.1");
server.sin_family = AF_INET;
server.sin_port = htons( 2000 );

//Connect to remote server
if (connect(socket_desc , (struct sockaddr *)&server , sizeof(server)) <0)
{
    puts("connect error");
    return 1;
}

puts("Connected\n");

//Send some data
message = "Hola!!!!\n\r\n";
if( send(socket_desc , message , strlen(message) , 0) < 0)
{
    puts("Send failed");
    return 1;
}
puts("Data Send\n");

//Receive a reply from the server
if( recv(socket_desc, server_reply , 2000 , 0) < 0)
{
    puts("recv failed");
}
puts("Reply received\n");
puts(server_reply);

return 0;
}

所以...我使用gcc -S -o example.s example.c来获取ASM代码...这是:

So ... I use gcc -S -o example.s example.c , to get the ASM code... wich is:

.file   "test.c"
.section    .rodata
.LC0:
.string "Could not create socket"
.LC1:
.string "127.0.0.1"
.LC2:
.string "connect error"
.LC3:
.string "Connected\n"
.align 8
.LC4:
.string "Hola!!  , \n\r\n"
.LC5:
.string "Send failed"
.LC6:
.string "Data Send\n"
.LC7:
.string "recv failed"
.LC8:
.string "Reply received\n"
.text
.globl  main
.type   main, @function
main:
.LFB2:
.cfi_startproc
pushq   %rbp
.cfi_def_cfa_offset 16
.cfi_offset 6, -16
movq    %rsp, %rbp
.cfi_def_cfa_register 6
subq    $2048, %rsp
movl    %edi, -2036(%rbp)
movq    %rsi, -2048(%rbp)
movl    $0, %edx
movl    $1, %esi
movl    $2, %edi
call    socket
movl    %eax, -4(%rbp)
cmpl    $-1, -4(%rbp)
jne .L2
movl    $.LC0, %edi
movl    $0, %eax
call    printf
.L2:
movl    $.LC1, %edi
call    inet_addr
movl    %eax, -28(%rbp)
movw    $2, -32(%rbp)
movl    $2000, %edi
call    htons
movw    %ax, -30(%rbp)
leaq    -32(%rbp), %rcx
movl    -4(%rbp), %eax
movl    $16, %edx
movq    %rcx, %rsi
movl    %eax, %edi
call    connect
testl   %eax, %eax
jns .L3
movl    $.LC2, %edi
call    puts
movl    $1, %eax
jmp .L7
.L3:
movl    $.LC3, %edi
call    puts
movq    $.LC4, -16(%rbp)
movq    -16(%rbp), %rax
movq    %rax, %rdi
call    strlen
movq    %rax, %rdx
movq    -16(%rbp), %rsi
movl    -4(%rbp), %eax
movl    $0, %ecx
movl    %eax, %edi
call    send
testq   %rax, %rax
jns .L5
movl    $.LC5, %edi
call    puts
movl    $1, %eax
jmp .L7
.L5:
movl    $.LC6, %edi
call    puts
leaq    -2032(%rbp), %rsi
movl    -4(%rbp), %eax
movl    $0, %ecx
movl    $2000, %edx
movl    %eax, %edi
call    recv
testq   %rax, %rax
jns .L6
movl    $.LC7, %edi
call    puts
.L6:
movl    $.LC8, %edi
call    puts
leaq    -2032(%rbp), %rax
movq    %rax, %rdi
call    puts
movl    $0, %eax
.L7:
leave
.cfi_def_cfa 7, 8
ret
.cfi_endproc
.LFE2:
.size   main, .-main
.ident  "GCC: (Debian 4.9.2-10) 4.9.2"

因此，在将example.s -o example.o用作示例之后，我使用ld example.o -o example，多数民众赞成在其中得到以下错误:

So after using as example.s -o example.o, I use ld example.o -o example, and thats where I get these following errors:

ld:警告:找不到入口符号 _start；默认为00000000004000b0test.o:在功能 main'中:test.c :(.text + 0x28):未定义对套接字的引用test.c :(.text + 0x40):对 printf'的未定义引用test.c :(.text + 0x4a):对 inet_addr的未定义引用test.c :(.text + 0x5d):未定义对 htons'的引用test.c :(.text + 0x77):未定义对 connect的引用test.c :(.text + 0x85):对 puts的未定义引用test.c :(.text + 0x99):对 puts的未定义引用test.c :(.text + 0xad):对 strlen'的未定义引用test.c :(.text + 0xc3):未定义引用发送test.c :(.text + 0xd2):对 puts的未定义引用test.c :(.text + 0xe3):对 puts的未定义引用test.c :(.text + 0xfe):对 recv'的未定义引用test.c :(.text + 0x10d):未定义对 puts的引用test.c :(.text + 0x117):对 puts的未定义引用test.c :(.text + 0x126):对 puts'

ld: warning: cannot find entry symbol _start; defaulting to 00000000004000b0 test.o: In function main': test.c:(.text+0x28): undefined reference tosocket' test.c:(.text+0x40): undefined reference to printf' test.c:(.text+0x4a): undefined reference toinet_addr' test.c:(.text+0x5d): undefined reference to htons' test.c:(.text+0x77): undefined reference toconnect' test.c:(.text+0x85): undefined reference to puts' test.c:(.text+0x99): undefined reference toputs' test.c:(.text+0xad): undefined reference to strlen' test.c:(.text+0xc3): undefined reference tosend' test.c:(.text+0xd2): undefined reference to puts' test.c:(.text+0xe3): undefined reference toputs' test.c:(.text+0xfe): undefined reference to recv' test.c:(.text+0x10d): undefined reference toputs' test.c:(.text+0x117): undefined reference to puts' test.c:(.text+0x126): undefined reference toputs'

在我看来，gcc没有正确使用.start，global main等.但是老实说，我不知道如何解决它.如果这是正确的，那为什么呢?

it seems to me that gcc is not usingn correctly .start, global main, etc. but to be honest I wouldnt know how to fix it., if this is correct then why?

任何帮助将不胜感激.

谢谢.

推荐答案

尝试一下

gcc -Wall -O -fverbose-asm -S example.c
gcc -c example.s -o example.o
gcc  example.o -o example

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