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Annotation of researchv10no/cmd/basic/bas/enter.s, revision 1.1.1.1

1.1       root        1: # enter(&prog,arg)
                      2: # will execute prog(arg) and return zero
                      3: # if a "leave(str)" is executed, an immediate return
                      4: # from the caller to the lowest level enter will be
                      5: # executed, and will return(str) to the caller of enter.
                      6: 
                      7:        .globl  _write
                      8:        .globl  _exit
                      9: 
                     10:        .text
                     11: 
                     12:        .globl  _enter
                     13: _enter:
                     14:        .word   0
                     15:        pushl   savesp          # save previous stack pointer
                     16:        pushl   fp              # save the current frame pointer
                     17:        movl    sp,savesp       # the saved stack pointer
                     18:        pushl   8(ap)           # fetch the argument
                     19:        calls   $1,*4(ap)       # call the function
                     20:        clrl    r0              # normal return
                     21: rtn:
                     22:        movl    savesp,sp       # get old stack
                     23:        movl    (sp)+,fp        # and old fp
                     24:        movl    (sp)+,savesp    # and restore old exit
                     25:        ret
                     26: 
                     27:        .globl  _leave
                     28: 
                     29: _leave:
                     30:        .word   0
                     31:        movl    4(ap),r0        # fetch return value
                     32:        tstl    savesp
                     33:        bneq    rtn             # and exit
                     34:        pushl   $18
                     35:        pushl   $msg
                     36:        pushl   $2
                     37:        calls   $3,_write
                     38:        clrl    -(sp)
                     39:        calls   $1,_exit
                     40: 
                     41:        .data
                     42: msg:
                     43:        .ascii  "bad call to leave\12"
                     44: 
                     45:        .text
                     46:        .lcomm  savesp,4

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