如何编译由 GCC 生成的 asm？

我在玩高潮密码，有些事困扰着我。

我编译如下:

#include <stdio.h>


int main(int argc, char** argv){
printf("Hello World\n");
return 0;
}

使用 gcc file.c -S -o file.S可以生成一段漂亮的暗码:

    .cstring
LC0:
.ascii "Hello World\0"
.text
.globl _main
_main:
LFB3:
pushq   %rbp
LCFI0:
movq    %rsp, %rbp
LCFI1:
subq    $16, %rsp
LCFI2:
movl    %edi, -4(%rbp)
movq    %rsi, -16(%rbp)
leaq    LC0(%rip), %rdi
call    _puts
movl    $0, %eax
leave
ret
LFE3:
.section __TEXT,__eh_frame,coalesced,no_toc+strip_static_syms+live_support
EH_frame1:
.set L$set$0,LECIE1-LSCIE1
.long L$set$0
LSCIE1:
.long   0x0
.byte   0x1
.ascii "zR\0"
.byte   0x1
.byte   0x78
.byte   0x10
.byte   0x1
.byte   0x10
.byte   0xc
.byte   0x7
.byte   0x8
.byte   0x90
.byte   0x1
.align 3
LECIE1:
.globl _main.eh
_main.eh:
LSFDE1:
.set L$set$1,LEFDE1-LASFDE1
.long L$set$1
LASFDE1:
.long   LASFDE1-EH_frame1
.quad   LFB3-.
.set L$set$2,LFE3-LFB3
.quad L$set$2
.byte   0x0
.byte   0x4
.set L$set$3,LCFI0-LFB3
.long L$set$3
.byte   0xe
.byte   0x10
.byte   0x86
.byte   0x2
.byte   0x4
.set L$set$4,LCFI1-LCFI0
.long L$set$4
.byte   0xd
.byte   0x6
.align 3
LEFDE1:
.subsections_via_symbols

我的下一个问题实际上是，我如何编译这个输出，我能让 GCC 为我做这件事吗？

174718 次浏览
小开

Yes, gcc can also compile assembly source code. Alternatively, you can invoke as, which is the assembler. (gcc is just a "driver" program that uses heuristics to call C compiler, C++ compiler, assembler, linker, etc..)

小开

You can use GAS, which is gcc's backend assembler:

http://linux.die.net/man/1/as

小开
最佳答案

Yes, You can use gcc to compile your asm code. Use -c for compilation like this:

gcc -c file.S -o file.o

This will give object code file named file.o. To invoke linker perform following after above command:

gcc file.o -o file
小开

You can embed the assembly code in a normal C program. Here's a good introduction. Using the appropriate syntax, you can also tell GCC you want to interact with variables declared in C. The program below instructs gcc that:

  • eax shall be foo
  • ebx shall be bar
  • the value in eax shall be stored in foo after the assembly code executed

\n

int main(void)
{
int foo = 10, bar = 15;
__asm__ __volatile__("addl  %%ebx,%%eax"
:"=a"(foo)
:"a"(foo), "b"(bar)
);
printf("foo+bar=%d\n", foo);
return 0;
}
小开

gcc can use an assembly file as input, and invoke the assembler as needed. There is a subtlety, though:

  • If the file name ends with ".s" (lowercase 's'), then gcc calls the assembler.
  • If the file name ends with ".S" (uppercase 'S'), then gcc applies the C preprocessor on the source file (i.e. it recognizes directives such as #if and replaces macros), and then calls the assembler on the result.

So, on a general basis, you want to do things like this:

gcc -S file.c -o file.s
gcc -c file.s
小开 
nasm -f bin -o 2_hello 2_hello.asm
小开

If you have main.s file. you can generate object file by GCC and also as

# gcc -c main.s
# as main.s -o main.o

check this link, it will help you learn some binutils of GCC http://www.thegeekstuff.com/2017/01/gnu-binutils-commands/


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