; @(#)crt0.s 1.3 96/05/31 14:40:27, AMD
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; Copyright 1988, 1989, 1990 Advanced Micro Devices, Inc.
;
; This software is the property of Advanced Micro Devices, Inc (AMD) which
; specifically grants the user the right to modify, use and distribute this
; software provided this notice is not removed or altered. All other rights
; are reserved by AMD.
;
; AMD MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARD TO THIS
; SOFTWARE. IN NO EVENT SHALL AMD BE LIABLE FOR INCIDENTAL OR CONSEQUENTIAL
; DAMAGES IN CONNECTION WITH OR ARISING FROM THE FURNISHING, PERFORMANCE, OR
; USE OF THIS SOFTWARE.
;
; So that all may benefit from your experience, please report any problems
; or suggestions about this software to the 29K Technical Support Center at
; 800-29-29-AMD (800-292-9263) in the USA, or 0800-89-1131 in the UK, or
; 0031-11-1129 in Japan, toll free. The direct dial number is 512-462-4118.
;
; Advanced Micro Devices, Inc.
; 29K Support Products
; Mail Stop 573
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; 800-292-9263
;
; /* $Id$ */
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
.file "crt0.s"
; crt0.s version 3.3-0
;
; This module gets control from the OS.
; It saves away the Am29027 Mode register settings and
; then sets up the pointers to the resident spill and fill
; trap handlers. It then establishes argv and argc for passing
; to main. It then calls _main. If main returns, it calls _exit.
;
; void = start( );
; NOTE - not C callable (no lead underscore)
;
.include "sysmac.h"
;
;
.extern V_SPILL, V_FILL
; .comm __29027Mode, 8 ; A shadow of the mode register
.comm __LibInit, 4
.text
.extern _main, _exit, _atexit
.word 0 ; Terminating tag word
.global start
start:
sub gr1, gr1, 6 * 4
asgeu V_SPILL, gr1, rab ; better not ever happen
add lr1, gr1, 6 * 4
;
; Save the initial value of the Am29027's Mode register
;
; If your system does not enter crt0 with value for Am29027's Mode
; register in gr96 and gr97, and also the coprocessor is active
; uncomment the next 4 instructions.
;
; const gr96, 0xfc00820
; consth gr96, 0xfc00820
; const gr97, 0x1375
; store 1, 3, gr96, gr97
;
; const gr98, __29027Mode
; consth gr98, __29027Mode
; store 0, 0, gr96, gr98
; add gr98, gr98, 4
; store 0, 0, gr97, gr98
;
; Now call the system to setup the spill and fill trap handlers
;
const lr3, spill
consth lr3, spill
const lr2, V_SPILL
syscall setvec
const lr3, fill
consth lr3, fill
const lr2, V_FILL
syscall setvec
;
; atexit(_fini)
;
; const lr0, _atexit
; consth lr0, _atexit
; const lr2,__fini
; calli lr0,lr0
; consth lr2,__fini
;
; Now call _init
;
; const lr0, __init
; consth lr0, __init
; calli lr0,lr0
; nop
;
; Get the argv base address and calculate argc.
;
syscall getargs
add lr3, v0, 0 ; argv
add lr4, v0, 0
constn lr2, -1
argcloop: ; scan for NULL terminator
load 0, 0, gr97, lr4
add lr4, lr4, 4
cpeq gr97, gr97, 0
jmpf gr97, argcloop
add lr2, lr2, 1
;
; Now call LibInit, if there is one. To aid runtime libraries
; that need to do some startup initialization, we have created
; a bss variable called LibInit. If the library doesn't need
; any run-time initialization, the variable is still 0. If the
; library does need run-time initialization, the library will
; contain a definition like
; void (*_LibInit)(void) = LibInitFunction;
; The linker will match up our bss LibInit with this data LibInit
; and the variable will not be 0. This results in the LibInit routine
; being called via the calli instruction below.
;
const lr0, __LibInit
consth lr0, __LibInit
load 0, 0, lr0, lr0
cpeq gr96, lr0, 0
jmpt gr96, NoLibInit
nop
calli lr0, lr0
nop
NoLibInit:
;
; Call RAMInit to initialize the data memory.
;
; The following code segment was used to create the two flavors of the
; run-time initialization routines (crt0_1.o, and crt0_2.o) as described
; in the User's Manual. If osboot is used to create a stand-alone
; application, or the call to RAMInit is made in the start-up routine,
; then the following is not needed.
;
; .ifdef ROM_LOAD
; .extern RAMInit
;
; const lr0, RAMInit
; consth lr0, RAMInit
; calli gr96, lr0
; nop
; .else
; nop
; nop
; nop
; nop
; .endif
;
; Uncomment the following .comm, if you ARE NOT using osboot as released
; with the High C 29K product, AND plan to use the romcoff utility to
; move code and/or data sections to ROM.
;
; .comm RAMInit, 4
;
; Furthermore, if the above is uncommented, then use the following logic
; to call the RAMInit function, if needed.
;
; const lr0, RAMInit
; consth lr0, RAMInit
; load 0, 0, gr96, lr0
; cpeq gr96, gr96, 0 ; nothing there?
; jmpt gr96, endRAMInit ; yes, nothing to init
; nop
; calli gr96, lr0 ; no, then instruction found
; nop ; execute function.
;
;
; call main, passing it 2 arguments. main( argc, argv )
;
const lr0, _main
consth lr0, _main
calli lr0, lr0
nop
;
; call exit
;
const lr0, _exit
consth lr0, _exit
calli lr0, lr0
add lr2, gr96, 0
;
; Should never get here, but just in case
;
loop:
syscall exit
jmp loop
nop
.sbttl "Spill and Fill trap handlers"
.eject
;
; SPILL, FILL trap handlers
;
; Note that these Spill and Fill trap handlers allow the OS to
; assume that the only registers of use are between gr1 and rfb.
; Therefore, if the OS desires to, it may simply preserve from
; lr0 for (rfb-gr1)/4 registers when doing a context save.
;
;
; Here is the spill handler
;
; spill registers from [*gr1..*rab)
; and move rab downto where gr1 points
;
; rab must change before rfb for signals to work
;
; On entry: rfb - rab = windowsize, gr1 < rab
; Near the end: rfb - rab > windowsize, gr1 == rab
; On exit: rfb - rab = windowsize, gr1 == rab
;
.global spill
spill:
sub tav, rab, gr1 ; tav = number of bytes to spill
srl tav, tav, 2 ; change byte count to word count
sub tav, tav, 1 ; make count zero based
mtsr CR, tav ; set Count Remaining register
sub tav, rab, gr1
sub tav, rfb, tav ; pull down free bound and save it in rab
add rab, gr1, 0 ; first pull down allocate bound
storem 0, 0, lr0, tav ; store lr0..lr(tav) into rfb
jmpi tpc ; return...
add rfb, tav, 0
;
; Here is the fill handler
;
; fill registers from [*rfb..*lr1)
; and move rfb upto where lr1 points.
;
; rab must change before rfb for signals to work
;
; On entry: rfb - rab = windowsize, lr1 > rfb
; Near the end: rfb - rab < windowsize, lr1 == rab + windowsize
; On exit: rfb - rab = windowsize, lr1 == rfb
;
.global fill
fill:
const tav, 0x80 << 2
or tav, tav, rfb ; tav = ((rfb>>2) | 0x80)<<2 == [rfb]<<2
mtsr IPA, tav ; ipa = [rfb]<<2 == 1st reg to fill
; gr0 is now the first reg to fill
sub tav, lr1, rfb ; tav = number of bytes to fill
add rab, rab, tav ; push up allocate bound
srl tav, tav, 2 ; change byte count to word count
sub tav, tav, 1 ; make count zero based
mtsr CR, tav ; set Count Remaining register
loadm 0, 0, gr0, rfb ; load registers
jmpi tpc ; return...
add rfb, lr1, 0 ; ... first pushing up free bound
;
; The __init function
;
; .sect .init,text
; .use .init
; .global __init
;__init:
; sub gr1,gr1,16
; asgeu V_SPILL,gr1,gr126
; add lr1,gr1,24
;
;
; The __fini function
;
; .sect .fini,text
; .use .fini
; .global __fini
;__fini:
; sub gr1,gr1,16
; asgeu V_SPILL,gr1,gr126
; add lr1,gr1,24
;
.end
