C语言 hello.c 的汇编解释

下面是著名的hello world！程序，此文将逐行解释c程序使用gcc 编译生成的汇编的 汇编程序。

hello.c

#include <stdio.h>
    
int main(void){
    printf("hello.\n");
    return 0;
}

编译生成汇编文件hello.s

gcc -S hello.c

    .file   "hello.c"
    .section    .rodata
.LC0:
    .string "hello."
    .text
    .globl  main
    .type   main, @function
main:
.LFB0:
    .cfi_startproc
    pushq   %rbp
    .cfi_def_cfa_offset 16
    .cfi_offset 6, -16
    movq    %rsp, %rbp
    .cfi_def_cfa_register 6
    leaq    .LC0(%rip), %rdi
    call    puts@PLT
    movl    $0, %eax
    popq    %rbp
    .cfi_def_cfa 7, 8
    ret
    .cfi_endproc
.LFE0:
    .size   main, .-main
    .ident  "GCC: (Ubuntu 7.2.0-8ubuntu3) 7.2.0"
    .section    .note.GNU-stack,"",@progbits

解释 line by line

.file "hello.c"
# 汇编来源的原始文件名

.section .rodata
# 定义一个data section，里面的数据是ro（read only的）

.LC0:
# .LC0 local constant, e.g string literal.

.string "hello"

.text
# 代码开始

.globl main
# global makes the symbol visible to ld.
# 定义一个全局可见的symbol
# We define a function called "main" and
# globally visible (other object files will be able to invoke it).

.type main, @function
# set the type of a symbol.
# 定义symbol main 的类型为一个function

.LFB0:
# .LFB0 local function beginning

pushq %rbp
movq %rsp, %rbp
leaq .LC0(%rip), %rdi
call puts@PLT
movl $0, %eax
popq %rbp

ret
# funtion exit

.LFE0:
# .LFE0 local function ending,

.size main, .-main
# set the size associated with a symbol
# 设置symbol main 的大小
# “.-main” ： 从当前位置到main

.ident "GCC: (Ubuntu 7.2.0-8ubuntu3) 7.2.0"
# 备注编译器版本

.section .note.GNU-stack,"",@progbits
# 意思是这个segment会被标记为 “非可执行栈”（栈中不能存可执行的指令，只存数据）
# With this section, the executable will be marked as
# "compatible with a non-executable stack" which the kernel
# will happily provide as such.
# A special section where GCC writes that the code can
# accommodate a non-executable stack. This is the normal case.
# Executable stacks are needed for some special usages (not standard C).
# On modern processors, the kernel can make a non-executable stack
# (a stack which triggers an exception if someone tries to execute
# as code some data which is on the stack); this is viewed by
# some people as a "security feature" because putting code on the stack
# is a common way to exploit buffer overflows.

参考链接：https://stackoverflow.com/questions/5325326/what-is-the-meaning-of-each-line-of-the-assembly-output-of-a-c-hello-world

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