usr/src/libc/sys/dup.s

# C library -- dup

#       f = dup(of [ ,nf])
#       f == -1 for error

        .set    dup,41
.globl  _dup
.globl  _dup2
.globl  cerror

_dup2:
        .word   0x0000
        bisb2   $0100,4(ap)
        brb     L1
_dup:
        .word   0x0000
L1:
        chmk    $dup
        bcc     noerror
        jmp     cerror
noerror:
        ret