[SOLVED] Why my code will crash at the end of the start function?

Why my code will crash at the end of the start function?

Test platform is 32 bit Linux.

Basically, I did a modification to the asm code gcc generated to change the entry point from main to start as below:

asm code:

     .file   "test.c"
    .intel_syntax noprefix
    .section        .rodata
.LC0:
    .string "%d\n"
    .text
    .globl  start
    .type   start, @function
start:
    push    ebp
    mov     ebp, esp
    call    main
    mov     eax, 0
    leave
    ret
    .size   start, .-start

    .globl  main
    .type   main, @function
main:
    push    ebp
    mov     ebp, esp
    and     esp, -16
    sub     esp, 32
    mov     DWORD PTR [esp+28], 1
    mov     eax, OFFSET FLAT:.LC0
    mov     edx, DWORD PTR [esp+28]
    mov     DWORD PTR [esp+4], edx
    mov     DWORD PTR [esp], eax
    call    printf
    mov     eax, 0

Then I use these to compile and link:

 as test.s -g -o test.o
 ld -o test test.o -lc -dynamic-linker /lib/ld-linux.so.2 -e start

When debug using gdb, it can successfully work until the end of start function, then from the debug info it seems that $EIP don't know where to jump next, and segment fault occurs...

Could anyone give me some help on this issue..? Thank you a lot!

Solution

you should call exit instead of set eax to 0 and return, because you don't use C main function(C-runtime), so nowhere to return.