3BSD/usr/mdec/mboot.s
#
# Tape boot program to load and transfer
# to a program on a 9-tr mag tape in
# UNIX 'tp' format on the VAX machine.
# This program is the boot block on the mag tape.
#
# Entry is made to the desired file via 'calls $0,entrypt'
# so return can be 'ret'.
#
.set core,50 # assume 50 K words avail.
.set BOOBLK,1 # no. tape blocks for boot
.set RELOC,0x50000
.set HDRSIZ,040 # size of file header for VAX
.set MAGIC,0410 # file type id in header
.set ENTSIZ,64 # size of 1 TP dir entry, bytes
.set PTHSIZ,32 # size of TP path name, bytes
.set BLKSIZ,512 # tape block size, bytes
.set NUMDIR,24 # no. of dir blocks on tape
.set ENTBLK,8 # no. of dir entries per tape block
.set NL,012 # new-line char
.set CR,015 # carriage-return char
.set MAXC,65535 # max. count for 'movc' op
.set TSIZ,4 # text size
.set DSIZ,8 # data size
.set BSIZ,12 # bss size
.set TENT,024 # task header entry loc
#
.set RXCS,32
.set RXDB,33
.set TXCS,34
.set TXDB,35
.set RXCS_DONE,0x80
.set TXCS_RDY,0x80
.set TXCS_pr,7 # bit position of TXCS ready bit
.set RXCS_pd,7 # bit position of RXCS done bit
#
.set FILSIZ,38 # dir offset for file size
.set BNUM,44 # dir offset for start block no.
#
# MBA registers
.set MBA1,0x20012000 # MBA 1 device reg's
.set M_cfg,0 # MBA config reg
.set M_cr,4 # MBA control reg
.set M_stat,8 # MBA status reg
.set M_var,12 # MBA virt addr reg
.set M_bc,16 # MBA byte count reg
.set M_map,0x800 # start of MBA map reg's
.set MBAinit,1 # MBA init bit in MBA control reg
#
# TM02 registers
.set TM02,MBA1+0x400 # start of TM02 reg's
.set TM_cs1,0 # TM02 control 1 reg
.set TM_ds,4 # status reg
.set TM_er,8 # error reg
.set TM_as,16 # attention summary
.set TM_fc,20 # frame count
.set TM_tc,36 # TM02 tape control
# Function codes for TM02 control reg 1
.set GO,1 # GO bit
.set RWND,6 # rewind, on-line
.set DCLR,010 # drive clear
.set SFWD,030 # space forward
.set SREV,032 # space reverse
.set WRIF,060 # write forward
.set REDF,070 # read forward
# misc bits
.set ERR,040000 # composite error bit in status reg
.set TCHAR,012300 # drive 0, odd parity, PDP11,
# 1600 BPI NRZ, abort on error - for
# tape control reg
.set DRDY,0200 # TM02/drive ready in status reg
.set TM_pd,7 # bit position of TM DRDY bit
.set TM_pe,14 # bit position of TM ERROR bit
#
.set tapa,-4 # desired tape addr
.set mtapa,-8 # current tape addr
.set name,-8-PTHSIZ # operator-typed file name
#
.set rMBA,r10
.set rTM,r11
# system initialization
init:
movl $RELOC,fp # core loc to which to move this program
addl3 $name,fp,sp # set stack pointer, leaving room for locals
clrl r0
cmpl (r0),$MAGIC
bneq rel
movl $HDRSIZ,r0 # skip header
rel :
movc3 $end,(r0),(fp) # move boot up to relocated position
jmp start+RELOC # jump to relocated code
#
start :
movab *$MBA1,%rMBA
movl $MBAinit,M_cr(%rMBA) # MBA initialize
movab *$TM02,%rTM
movl $TCHAR,TM_tc(%rTM) # drive no., etc.
movl $DCLR+GO,TM_cs1(%rTM) # drive clear
bsbw rew # rewind input tape
movab name(fp),r4 # start of filename storage
movzbl $'=,r0 # prompt character
bsbw putc # output char to main console
#
gfil :
movl r4,r1 # loc at which to store user-specified file name
nxtc :
bsbw getc # get input char's in file name
cmpb r0,$NL # terminator ?
beql nullc
cmpb r0,$'@ # r0 = return character
beql gfil
movb r0,(r1)+
cmpb r0,$'#
bneq nxtc
tstw -(r1) # subl2 $2,r1
cmpl r1,r4
blss gfil
brb nxtc
nullc:
subl3 r4,r1,r9 # size of path name
beql start # dumb operator
#
# user-specified TP filename has been stored at name(fp)
#
# read in entire tp directory contents into low core
# 'cmpc[35]' instruction uses reg's 0-3
#
dirred :
movl $BOOBLK,tapa(fp) # desired tape block no.
movl $(NUMDIR*BLKSIZ),r6 # no. bytes in total dir
bsbw taper # read no. bytes indicated
#
# search entire directory for user-specified file name
clrl r5 # dir buff loc = 0
nxtdir :
cmpc3 r9,(r5),(r4) # see if dir entry matches filename
beql fndfil # found match
acbl $NUMDIR*BLKSIZ-1,$ENTSIZ,r5,nxtdir # see if done with tp dir
#
brb start # entry not in directory - start all over
#
# found desired tp dir entry
fndfil :
movzwl BNUM(r5),tapa(fp) # start block no., 2 bytes
movzwl FILSIZ(r5),r6 # low 2 bytes file size
insv FILSIZ-1(r5),$16,$8,r6 # file size, high byte
cmpl r6,$RELOC-512 # check if file fits below stack
blss filok # file o.k.
brw start # file too large
#
# time to read in desired file from tape
filok :
movl r6,r7 # save r6
bsbb taper
bsbw rew
#
# if load module header exists, move down rest of load
# module to 0
clrl r5 # entry loc
cmpl (r5),$MAGIC # unix a.out?
bneq clrcor
# move start of exec image down to 0
clrl r0
movq TSIZ(r0),r1 # text size and data size
movq BSIZ(r0),r3 # bss size, symbol table size
movl TENT(r0),r5 # entry loc
movl r7,r6 # restore file size
movtxt:
movb HDRSIZ(r0),(r0)+
sobgtr r6,movtxt
# move data up to page boundary
extzv $0,$9,r1,r0 # byte-in-page of last text byte
beql clrcor
subl3 r0,$512,r0 # room needed
addl2 r2,r1 # current end+1 of data
addl2 r1,r0 # new end+1 of data
movl r0,r7 # start here on bssz clearing
movdat:
movb -(r1),-(r0)
sobgtr r2,movdat
#
# clear core up to stack
clrcor :
subl3 r7,$RELOC-4,r0 # no. bytes to clear
clrit :
clrb (r7)+
sobgtr r0,clrit
#
# time to jump to start of file & execute
calls $0,(r5)
brw start # returned from execution - start all over
#
#
# taper: movcTAPE (r6),tapa(fp),0
#
rew2 :
bsbb rew # beginning of tape
taper0:
bsbb rrec # advance 1 block; (we never want block 0)
taper :
clrl r0 # SBI page no.
cmpl mtapa(fp),tapa(fp) # current position .vs. desired
bgtr rew2
blss taper0
rloop :
bsbb rrec
acbl $1,$-BLKSIZ,r6,rloop
rsb
#
# subr to read 1 block from mag tape into page (r0)
#
rrec :
movl TM_ds(%rTM),r2
bbc $TM_pd,r2,rrec # TM02 & drive ready ?
movl $-BLKSIZ,M_bc(%rMBA) # byte count
bisl3 $0x80000000,r0,M_map(%rMBA) # MBA map entry = valid bit + phys page no.
clrl M_var(%rMBA) # MBA virt addr reg = map reg no. + byte offset
movl $REDF+GO,TM_cs1(%rTM) # read forward
tmrdy :
movl TM_ds(%rTM),r2
bbc $TM_pd,r2,tmrdy # TM02 & device ready ?
movl TM_er(%rTM),r2
bbc $TM_pe,r2,donred # any read errors ?
clrl TM_ds(%rTM) # clear status - try to recover
mnegl $1,TM_fc(%rTM) # frame count for backspace
movl $SREV+GO,TM_cs1(%rTM) # space reverse
brb rrec
donred :
incl r0 # next SBI page no.
incl mtapa(fp) # mag tape block position
rsb
#
# subr to rewind mag tape
#
rew :
movl $RWND+GO,TM_cs1(%rTM) # rewind
clrl mtapa(fp) # current position
rsb
#
# subroutines to do char i-o with main tty console
#
getc :
mfpr $RXCS,r0
bbc $RXCS_pd,r0,getc # receiver ready ?
mfpr $RXDB,r0
cmpb r0,$CR
bneq putc
movb $NL,r0
#
putc:
mfpr $TXCS,r2
bbc $TXCS_pr,r2,putc # transmitter ready ?
cmpb r0,$NL
bneq wbyt
movb $CR,r0
bsbb putc
clrb r0
bsbb putc
movb $NL,r0
wbyt :
extzv $0,$7,r0,r0
mtpr r0,$TXDB
rsb
end :