i'm trying to make a buffer overflow attack but when i adding nop - sled (\x90), memory in stack show something else

buff2.c

#include<stdio.h>
#include<string.h>

int main()
{
        char buff[80];
        scanf("%s",buff);
        printf("Hello %s !\n",buff);
        return 0;
}

genrating nop-sled

perl -e 'print "\x90"x80 . "\n"' ��������������������������������������������������������������������������������

when i'm running this buff2.c in gdb -

�������������������������������������������������������������������������������� Hello �������������������������������������������������������������������������������� !

Program received signal SIGSEGV, Segmentation fault. 0x0000555555555183 in main () at buff2.c:10

and the stack look like -

0x7fffffffe130: 0x00000000      0x00000000      0x00000000      0x00000000
0x7fffffffe140: 0x00000000      0x00000000      0x00000000      0x00000000
0x7fffffffe150: 0x00000000      0x00000000      0x00000000      0x00000000
0x7fffffffe160: 0x00000000      0x00000000      0x00000000      0x00000000
0x7fffffffe170: 0x00000000      0x00000000      0x00000000      0x00000000
0x7fffffffe180: 0x00000000      0x00000000      0xf7ffe190      0x00007fff
0x7fffffffe190: 0x00000000      0x00000000      0x5555517d      0x00005555
0x7fffffffe1a0: 0xefbdbfef      0xbfefbdbf      0xbdbfefbd      0xefbdbfef
0x7fffffffe1b0: 0xbfefbdbf      0xbdbfefbd      0xefbdbfef      0xbfefbdbf
0x7fffffffe1c0: 0xbdbfefbd      0xefbdbfef      0xbfefbdbf      0xbdbfefbd
0x7fffffffe1d0: 0xefbdbfef      0xbfefbdbf      0xbdbfefbd      0xefbdbfef
0x7fffffffe1e0: 0xbfefbdbf      0xbdbfefbd      0xefbdbfef      0xbfefbdbf
0x7fffffffe1f0: 0xbdbfefbd      0xefbdbfef      0xbfefbdbf      0xbdbfefbd
0x7fffffffe200: 0xefbdbfef      0xbfefbdbf      0xbdbfefbd      0xefbdbfef
0x7fffffffe210: 0xbfefbdbf      0xbdbfefbd      0xefbdbfef      0xbfefbdbf
0x7fffffffe220: 0xbdbfefbd      0xefbdbfef      0xbfefbdbf      0xbdbfefbd
0x7fffffffe230: 0xefbdbfef      0xbfefbdbf      0xbdbfefbd      0xefbdbfef
0x7fffffffe240: 0xbfefbdbf      0xbdbfefbd      0xefbdbfef      0xbfefbdbf
0x7fffffffe250: 0xbdbfefbd      0xefbdbfef      0xbfefbdbf      0xbdbfefbd
--Type <RET> for more, q to quit, c to continue without paging--
0x7fffffffe260: 0xefbdbfef      0xbfefbdbf      0xbdbfefbd      0xefbdbfef
0x7fffffffe270: 0xbfefbdbf      0xbdbfefbd      0xefbdbfef      0xbfefbdbf
0x7fffffffe280: 0xbdbfefbd      0xefbdbfef      0xbfefbdbf      0xbdbfefbd
0x7fffffffe290: 0x00000000      0x00000000      0x00000000      0x00000000
0x7fffffffe2a0: 0x55555060      0x00005555      0xffffe2d0      0x00007fff
0x7fffffffe2b0: 0x00000000      0x00000000      0x5555508a      0x00005555

can't get what is 0xefbdbfef