使用 gcc 将汇编代码与 C 代码链接的正确方法是什么 [英] What is the correct way to link assembly code with C code using gcc

问题描述

假设您有以下程序集文件:

Suppose you have the following assembly files:

  .file "print.s"
  .intel_syntax noprefix

  .text

  .globl _start
  .type _start, @function
_start:
  mov rax, 1
  mov rdi, 1
  lea rsi, hello_string
  mov rdx, 14
  syscall
  mov rax, 60
  mov rdi, 0
  syscall
  .size _start, .-_start

和

  .file "string.s"
  .intel_syntax noprefix

  .data

  .globl hello_string
  .type hello_string, @object
hello_string:
  .string "Hello, world!\n"
  .size hello_string, 14

如果你运行 as string.s -o string.o，as print.s -o print.o 然后 ld *.o -ohello.elf，您将获得一个可执行文件，该文件打印 Hello, world!.现在假设您将 print.s 中的 _start 标签更改为 print 并且您有以下 C 文件:

If you run as string.s -o string.o, as print.s -o print.o and then ld *.o -o hello.elf, you get a executable file which prints Hello, world!. Now suppose that you change the _start label in print.s to print and you have the following C file:

// main.c
void print(void);

int main (void) {
  print();
  return 0;
}

我想运行类似 gcc -o main.elf main.c string.s print.s 的东西来获取我的两个程序集文件并将它们链接到标准 C 运行时.所写的此命令不起作用.我收到以下错误消息:

I want to run something like gcc -o main.elf main.c string.s print.s to take my two assembly files and link them into the standard C runtime. This command as written doesn't work. I get the following error message:

/usr/bin/ld: /tmp/ccc1yRif.o: relocation R_X86_64_32S against symbol `hello_string' can not be used when making a shared object; recompile with -fPIC

我不知道如何正确使用 -fPIC 标志来使工作正常进行.我什至不确定这是否是我应该做的.我可以尝试使用内联汇编器来做到这一点，但对于我的实际用例来说，这会非常烦人，我更愿意学习如何将汇编块正确链接到我的 C 程序中.我在网上找不到太多关于此的信息.

I can't figure out how to correctly use the -fPIC flag to make things work. I am not even sure if that is what I should be doing. I could try and use the inline assembler to do this, but for my actual use cases, that would be extremely annoying and I would much rather learn how to correctly link assembly chunks into my C programs. I haven't been able to find much information about this online.

问题: 如何正确使用 GNU 链接器将汇编文件链接到 C 运行时?

Question: How do you correctly use the GNU linker to link assembly files into the C runtime?

在 如何将 C 目标文件与汇编语言目标文件链接起来?，OP 正在询问如何仅使用 ld 解决类似的链接问题.我想使用 gcc 这是链接问题中推荐的解决方案，但我什至无法让它工作.

In How to link a C object file with a Assembly Language object file?, the OP is asking about how to solve a similar linking problem just using ld. I want to use gcc which is the recommended solution in the linked question, but I can't even get that to work.

推荐答案

好的，我现在想通了.错误消息似乎告诉我 gcc 正在尝试创建共享对象.这让我想到了一个问题 gcc 6.2.0 试图在不应该创建共享对象时创建共享对象?

OK, so I have figured it out now. The error message seems to be telling me that gcc is trying to make a shared object. This lead me to the question gcc 6.2.0 is attempting to create shared object when it shouldn't?

解决办法是运行gcc -no-pie main.c string.s print.s -o main.elf

根据手册页，-no-pie 告诉 gcc 不要生成位置独立的可执行文件.

according to the man page, -no-pie tells gcc to not produce a position indipendent executable.

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