Stopping at the first machine code instruction in GDB
Starting with GDB 8.1, there's a special command for this: starti
. Example GDB session:
$ gdb /bin/true
Reading symbols from /bin/true...(no debugging symbols found)...done.
(gdb) starti
Starting program: /bin/true
Program stopped.
0xf7fdd800 in _start () from /lib/ld-linux.so.2
(gdb) x/5i $pc
=> 0xf7fdd800 <_start>: mov eax,esp
0xf7fdd802 <_start+2>: call 0xf7fe2160 <_dl_start>
0xf7fdd807 <_dl_start_user>: mov edi,eax
0xf7fdd809 <_dl_start_user+2>: call 0xf7fdd7f0
0xf7fdd80e <_dl_start_user+7>: add ebx,0x1f7e6
The info files
command might give you an address you can break on:
(gdb) info files
...
Entry point: 0x80000000
...
(gdb) break *0x80000000
(gdb) run