[ Linux ] 심볼없는 파일 메인함수 찾기

root@Kali-Linux:/home/flag# ltrace ./nos

__libc_start_main(0x40050c, 1, 0x7fffd6006a28, 0x400540, 0x400530 <unfinished ...>

printf("hello")                                            = 5

hello+++ exited (status 0) +++

__libc_start_main에 첫번째 인자가 main함수의 주소

root@Kali-Linux:/home/flag# objdump -f ./nos

./nos:     file format elf64-x86-64

architecture: i386:x86-64, flags 0x00000112:

EXEC_P, HAS_SYMS, D_PAGED

start address 0x0000000000400400

root@Kali-Linux:/home/flag# objdump -d ./nos | grep 400400 -A 20

0000000000400400 <.text>:

  400400: 31 ed                 xor    %ebp,%ebp

  400402: 49 89 d1             mov    %rdx,%r9

  400405: 5e                   pop    %rsi

  400406: 48 89 e2             mov    %rsp,%rdx

  400409: 48 83 e4 f0           and    $0xfffffffffffffff0,%rsp

  40040d: 50                   push   %rax

  40040e: 54                   push   %rsp

  40040f: 49 c7 c0 30 05 40 00 mov    $0x400530,%r8            //finit

  400416: 48 c7 c1 40 05 40 00 mov    $0x400540,%rcx            //init

  40041d: 48 c7 c7 0c 05 40 00 mov    $0x40050c,%rdi

  400424: e8 c7 ff ff ff       callq  4003f0 <__libc_start_main@plt>

마찬가지로  __libc_start_main 첫번째 인자