Linux NASM OUTSB SegFault

Question

I'm trying to write byte 0xff to the parallel port at 0x378. It compiles and links without issue, but segfaults at the OUTSB instruction.

section .text
        global _start

_err_exit:
        mov     eax,    1
        mov     ebx,    1
        int     80h

_start:
        mov     eax,    101     ; ioperm
        mov     ebx,    0x378   ; Parallel port addr
        mov     ecx,    2       ; number of bytes to 'unlock'
        mov     edx,    1       ; enable
        int     80h

        mov     esi,    0xff
        mov     dx,     0x378
        outsb

        mov     eax,    1       ; exit
        mov     ebx,    0
        int     80h

If I step through it with GDB and check the registers just before the OUTSB instruction, it doesn't look like there is anything in the DX register? or dx == edx in 32bit?

(gdb) info registers 
eax            0x0  0
ecx            0x2  2
edx            0x378    888
ebx            0x378    888
esp            0xffffd810   0xffffd810
ebp            0x0  0x0
esi            0xff 255
edi            0x0  0
eip            0x8048090    0x8048090 <_start+36>
eflags         0x246    [ PF ZF IF ]
cs             0x23 35
ss             0x2b 43
ds             0x2b 43
es             0x2b 43
fs             0x0  0
gs             0x0  0

What am I doing wrong here?

(info on the OUTS instructions: http://siyobik.info/main/reference/instruction/OUTS%2FOUTSB%2FOUTSW%2FOUTSD)

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EDIT:

The C version of the program works:

int main(int argc, char *argv[])
{
  int addr = 0x378;
  int result = ioperm(addr,5,1);

  outb(0xff, addr);

}