To arrive to your _init function just continue execution. This will stop once again in the intended place.
gdb -q test.out
Reading symbols from test.out...done.
(gdb) b _init
Breakpoint 1 at 0x4003e0
(gdb) run
Starting program: /home/[censored]/stk/test.out
Breakpoint 1, _init (argc=1, argv=0x7fffffffe008, envp=0x7fffffffe018) at ../csu/init-first.c:52
52 ../csu/init-first.c: No such file or directory.
(gdb) bt
#0 _init (argc=1, argv=0x7fffffffe008, envp=0x7fffffffe018) at ../csu/init-first.c:52
#1 0x00007ffff7dea0fd in call_init (l=0x7ffff7ff74c0, argc=argc@entry=1, argv=argv@entry=0x7fffffffe008, env=env@entry=0x7fffffffe018) at dl-init.c:64
#2 0x00007ffff7dea223 in call_init (env=<optimized out>, argv=<optimized out>, argc=<optimized out>, l=<optimized out>) at dl-init.c:36
#3 _dl_init (main_map=0x7ffff7ffe1c8, argc=1, argv=0x7fffffffe008, env=0x7fffffffe018) at dl-init.c:126
#4 0x00007ffff7ddb30a in _dl_start_user () from /lib64/ld-linux-x86-64.so.2
#5 0x0000000000000001 in ?? ()
#6 0x00007fffffffe364 in ?? ()
#7 0x0000000000000000 in ?? ()
(gdb) c
Continuing.
Breakpoint 1, 0x00000000004003e0 in _init ()
(gdb) bt
#0 0x00000000004003e0 in _init ()
#1 0x0000000000400593 in __libc_csu_init ()
#2 0x00007ffff7a36e55 in __libc_start_main (main=0x40052d <main>, argc=1, argv=0x7fffffffe008, init=0x400560 <__libc_csu_init>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fffffffdff8)
at libc-start.c:246
#3 0x0000000000400469 in _start ()
(gdb) info shared
From To Syms Read Shared Object Library
0x00007ffff7ddaae0 0x00007ffff7df54e0 Yes /lib64/ld-linux-x86-64.so.2
0x00007ffff7a344a0 0x00007ffff7b79583 Yes /lib/x86_64-linux-gnu/libc.so.6
(gdb) x/10i $pc
=> 0x4003e0 <_init>: sub $0x8,%rsp
0x4003e4 <_init+4>: mov 0x200c0d(%rip),%rax # 0x600ff8
0x4003eb <_init+11>: test %rax,%rax
0x4003ee <_init+14>: je 0x4003f5 <_init+21>
0x4003f0 <_init+16>: callq 0x400430 <__gmon_start__@plt>
0x4003f5 <_init+21>: add $0x8,%rsp
0x4003f9 <_init+25>: retq
(gdb) info breakpoints
Num Type Disp Enb Address What
1 breakpoint keep y <MULTIPLE>
breakpoint already hit 2 times
1.1 y 0x00000000004003e0 <_init>
1.2 y 0x00007ffff7a36c20 in _init at ../csu/init-first.c:52
According to information about shared libraries, it stopped first time in address area of libc.so , which looks like also has _init function, which caused gdb to set this breakpoint there too (see breakpoint definition at the end of the listing).
Good luck.