在64位模式下编译NASM代码时发生重定位错误 [英] Relocation error when compiling NASM code in 64-bit mode
问题描述
我编写了一个简单的汇编代码，试图在64位模式下进行编译.这是代码:
I have written a simple assembly code which I am trying to compile in 64-bit mode. Here is the code:
extern printf
section .rodata
readinfo db `%d\n`, 0
section .text
global main
main:
mov rbp, rsp ; for correct debugging
mov rax, 5
push rax
push readinfo
call printf
add rsp, 8
xor rax, rax
mov rsp, rbp
ret
这是我给nasm和gcc的说明(正如我在其他文章中所读到的那样，gcc会自动将目标文件与默认的c库链接):
And here are the instructions I give to nasm and gcc (as I have read on other posts, gcc automatically links the object file with the default c libraries):
nasm -f elf64 -o test.o test.asm -D UNIX
gcc -o test test.o
但是，我收到以下重定位错误:
However, I get the following relocation error:
/usr/bin/x86_64-linux-gnu-ld:test.o:针对 制作PIE对象时，不能使用`.rodata'.重新编译 -fPIC
/usr/bin/x86_64-linux-gnu-ld: test.o: relocation R_X86_64_32S against `.rodata' can not be used when making a PIE object; recompile with -fPIC
/usr/bin/x86_64-linux-gnu-ld:最终链接失败:无法表示 输出部分
/usr/bin/x86_64-linux-gnu-ld: final link failed: Nonrepresentable section on output
collect2:错误:ld返回1个退出状态
collect2: error: ld returned 1 exit status
当我使用'-no-pic'选项进行编译以禁用与位置无关的代码时，它编译时没有错误，但是执行后，我遇到了没有输出的段错误. 当我重新编译32位代码(用32位替换64位寄存器)时，没有任何错误.这些命令是:
When I compile with the '-no-pic' option to disable positionally-independent code, it compiles without errors, but after execution I get a segfault with no output. When I recompile the code in 32-bit (replacing 64-bit registers with 32-bit), I get no error. The commands are:
nasm -f elf32 -o test.o test.asm -D UNIX
gcc -o test test.o -m32
我的问题是:为什么我不能在64位模式下使用PIC编译代码?
My question is: why can't I compile the code with PIC in 64bit mode?
PS: This is not a duplicate of Can't link a shared library from an x86-64 object from assembly because of PIC , since the error is different and the solution found in that post has nothing in relation with my problem. I have edited the error output to specify.
推荐答案
错误是我使用了错误的调用约定.在体系结构x86_64中，前两个参数分别在rdi和rsi中传递，而无需使用堆栈.另外，我需要在通话中添加"wrt ..plt".以下代码有效:
The mistake was that I was using the wrong calling convention. In architecture x86_64 the first two arguments are passed in rdi and rsi, respectively, without using the stack. Also, I needed to add "wrt ..plt" to the call. The following code works:
extern printf
section .rodata
readinfo db `%d\n`, 0
section .text
global main
main:
mov rbp, rsp ; for correct debugging
mov rsi, 5
mov rdi, readinfo
xor rax, rax
call printf wrt ..plt
xor rax, rax
mov rsp, rbp
ret
nasm和gcc的命令未更改.
The commands for nasm and gcc haven't changed.
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