main 末尾的跳转未使用 int 0x80 执行

Question

所以我有了这个基本的 hello world 代码

SECTION .data       ; data section
msg:    db "Hello World",10 ; the string to print, 10=cr
len:    equ $-msg       ; "$" means "here"
                ; len is a value, not an address
msg2:    db "test" ; the string to print, 10=cr
len2:    equ $-msg2       ; "$" means "here"
                ; len is a value, not an address                

SECTION .text       ; code section
        global main     ; make label available to linker 
main:               ; standard  gcc  entry point
    mov edx,len     ; arg3, length of string to print
    mov ecx, msg   ; arg2, pointer to string
    mov ebx,1       ; arg1, where to write, screen
    mov eax,4       ; write sysout command to int 80 hex
    int 0x80        ; interrupt 80 hex, call kernel
    mov ebx,0       ; exit code, 0=normal
    mov eax,1       ; exit command to kernel
    int 0x80        ; interrupt 80 hex, call kernel
    JMP l2



l2:
    mov edx,len2     ; arg3, length of string to print
    mov ecx,msg2     ; arg2, pointer to string
    mov ebx,1       ; arg1, where to write, screen
    mov eax,4       ; write sysout command to int 80 hex
    int 0x80        ; interrupt 80 hex, call kernel

    mov ebx,0       ; exit code, 0=normal
    mov eax,1       ; exit command to kernel
    int 0x80        ; interrupt 80 hex, call kernel

当我把跳转放在主线的末尾时，它不起作用，但如果我把它放在最后一行之前，这样：

main:               ; standard  gcc  entry point
    mov edx,len     ; arg3, length of string to print
    mov ecx, msg   ; arg2, pointer to string
    mov ebx,1       ; arg1, where to write, screen
    mov eax,4       ; write sysout command to int 80 hex
    int 0x80        ; interrupt 80 hex, call kernel
    mov ebx,0       ; exit code, 0=normal
    mov eax,1       ; exit command to kernel
    JMP l2
    int 0x80        ; interrupt 80 hex, call kernel

跳跃有效。为什么它不适用于第一种情况？

Answer 1

最后的 int 0x80 是一个系统调用，要求 (Linux?) 内核终止进程。

在 C 中它会是 like:

     exit(0);
     goto somewhere;   // Never executed because the process no longer exists

main 末尾的跳转未使用 int 0x80 执行

jump at the end of main is not execute with int 0x80

assembly

nasm