2.11BSD#431 - /usr/src/sys/pdpstand/srt0.s

   1: / 2000/04/06 - make 'nofault' global so toyset.o can use it
   2: / 1995/06/04 - devsw[] entries are 14. bytes, need a tape seek routine entry.
   3: / 1995/06/02 - Modifications for split I/D to work.  The vectors need to be
   4: /	       in 'data' space.
   5: / 1995/06/01 - Make copy of SSR3 so we can tell if split I/D is enabled.
   6: / 1995/05/30 - devsw[] entries are 12. bytes now.
   7: /
   8: / Startup code for standalone utilities
   9: / sms - mods to pass boot device and csr on to program
  10: /
  11: /      Note that the bootstrap passes the cputype through in r0.
  12: 
  13: PS      = 177776
  14: SSR3    = 172516
  15: 
  16: .globl  _main, __rtt, _devsw, _ADJcsr
  17: 
  18: #ifdef  SPLIT_ID
  19:         .data
  20: #else
  21:         .text
  22: #endif
  23: ZERO:
  24:         jmp     start
  25: 
  26: /
  27: / trap vectors
  28: /
  29:         trap;340        / 004 - bus error
  30:         trap;341        / 010 - illegal instruction
  31:         trap;342        / 014 - BPT
  32:         trap;343        / 020 - IOT
  33:         trap;344        / 024 - POWER FAIL
  34:         trap;345        / 030 - EMT
  35:         start;346       / 034 - TRAP
  36: .= ZERO + 400
  37:         .text
  38: 
  39: start:
  40:         mov     $340,*$PS
  41:         mov     $trap,*$034
  42: 
  43: / Save information which Boot has passed thru to us
  44: 
  45:         mov     r0,_cputype     / assume that the boot left this in r0
  46:         mov     r1,_bootcsr     / assume that boot left csr in r1
  47:         mov     r3,_bootdev     / and boot device major,minor in r3
  48: 
  49: / Make a copy of SSR3.  If this register does not exist it is probably better
  50: / to trap now rather than later - the absence of this register means no  split
  51: / I/D space and the kernel won't run.
  52: 
  53:         mov     *$SSR3,_ssr3copy
  54: 
  55:         mov     $157772,sp      / return address,psw at 157774&6
  56: 
  57: / controller number is in bits 6&7 of r3 (_bootdev).  major device number
  58: / is in bits 8-15.  what we need to do now is place the csr into
  59: / the appropriate driver's csrlist which is indexed by controller number.
  60: 
  61:         ash     $-5,r3                  / r3 = controller# * 2
  62:         mov     r3,r0                   / controller number in bits 1,2
  63:         bic     $!6,r0                  / make a word index
  64:         ash     $-3,r3                  / major device # to bits 0-7
  65:         mov     r3,r2                   / save major for later
  66:         mul     $14.,r3                 / devsw[] members are 14. bytes each
  67:         mov     _devsw+10(r3),r3        / get csrlist for driver
  68:         add     r0,r3                   / point to controller's entry
  69:         asr     r0                      / controller number in bits 0,1
  70:         mov     r0,_bootctlr            / set default controller number
  71: 
  72: / the CSR passed from the ROMs is not necessarily the first address
  73: / of a device!  We therefore have to adjust the CSR so that the structure
  74: / pointers in the drivers are origined at the base address rather than
  75: / the ROM supplied address.  The adjustment was not stored in devsw[] to
  76: / save space (can get by with an array of bytes instead of words).
  77: 
  78:         movb    _ADJcsr(r2),r2          / adjust (possibly) the CSR
  79:         mov     _bootcsr,r1
  80:         sub     r2,r1
  81: 
  82:         mov     r1,(r3)                 / store controller's csr in table
  83:         jsr     pc,_main
  84: 
  85: / fix up stack to point at trap ps-pc pair located at top of memory
  86: / so we can return to the bootstrap.
  87: /
  88: / the return protocol originally changed from 140000 because icheck was
  89: / too large.  icheck was reduced in size but the 157774 return protocol
  90: / was retained to allow for slightly oversized programs.
  91: 
  92: __rtt:
  93:         mov     $157774,sp
  94:         rtt                             / we hope!
  95:         br      .
  96: 
  97: 
  98: .globl  _trap
  99: trap:
 100:         mov     *$PS,-(sp)
 101:         tst     nofault
 102:         bne     3f
 103:         mov     r0,-(sp)
 104:         mov     r1,-(sp)
 105: 2:      jsr     pc,_trap
 106:         mov     (sp)+,r1
 107:         mov     (sp)+,r0
 108:         tst     (sp)+
 109:         rtt
 110: 3:      tst     (sp)+
 111:         mov     nofault,(sp)
 112:         rtt
 113: 
 114:         .data
 115: .globl  nofault, _cputype, _bootcsr, _bootdev, _ssr3copy, _bootctlr
 116: 
 117: nofault:        .=.+2   / where to go on predicted trap
 118: _cputype:       .=.+2   / cpu type (currently 44, 70, 73)
 119: _bootdev:       .=.+2   / makedev(major,unit) for boot device
 120: _bootcsr:       .=.+2   / csr of boot controller
 121: _bootctlr:      .=.+2   / number of boot controller (bits 6 and 7 of minor)
 122: _ssr3copy:      .=.+2   / copy of SSR3

Defined functions

Defined variables