URL https://opencores.org/ocsvn/eco32/eco32/trunk

Subversion Repositories eco32

[/] [eco32/] [trunk/] [disk/] [tools/] [fs-NetBSD/] [mkpboot/] [pbr.s] - Blame information for rev 274

Go to most recent revision | Details | Compare with Previous | View Log


;
; pbr.s -- the partition boot record
;
 
; Runtime environment:
;
; This code must be loaded and started at 0xC0010000.
; It allocates a stack from 0xC0011000 downwards. So
; it must run within 4K (code + data + stack).
;
; This code expects the disk number of the boot disk
; in $16, the start sector of the disk or partition
; to be booted in $17 and its size in $18.
;
; NOTE: THIS IS A FAKE PARTITION BOOT RECORD!
;       It doesn't load anything, but displays a message
;       where the real thing can be downloaded from.
 
        .set    stacktop,0xC0011000     ; top of stack
 
        .set    cout,0xC0000020         ; the monitor's console output
 
        ; display a message and halt
start:
        add     $29,$0,stacktop          ; setup stack
        add     $4,$0,strtmsg            ; say what is going on
        jal     msgout
        j       halt
 
        ; output message
        ;   $4 pointer to string
msgout:
        sub     $29,$29,8
        stw     $31,$29,4
        stw     $16,$29,0
        add     $16,$4,0         ; $16: pointer to string
msgout1:
        ldbu    $4,$16,0         ; get character
        beq     $4,$0,msgout2            ; done?
        jal     chrout                  ; output character
        add     $16,$16,1               ; bump pointer
        j       msgout1                 ; continue
msgout2:
        ldw     $16,$29,0
        ldw     $31,$29,4
        add     $29,$29,8
        jr      $31
 
        ; output character
        ;   $4 character
chrout:
        sub     $29,$29,4
        stw     $31,$29,0
        add     $8,$0,cout
        jalr    $8
        ldw     $31,$29,0
        add     $29,$29,4
        jr      $31
 
        ; halt execution by looping
halt:
        add     $4,$0,hltmsg
        jal     msgout
halt1:
        j       halt1
 
        ; messages
strtmsg:
        .byte   0x0D, 0x0A
        .byte   "You didn't expect this tiny program to be"
        .byte   0x0D, 0x0A
        .byte   "a full-fledged operating system, did you?"
        .byte   0x0D, 0x0A
        .byte   "You can find the real NetBSD for ECO32 on"
        .byte   0x0D, 0x0A
        .byte   "GitHub, under the name 'netbsd-on-eco32'."
        .byte   0x0D, 0x0A, 0x0D, 0x0A, 0
hltmsg:
        .byte   "bootstrap halted", 0x0D, 0x0A, 0
 
        ; boot record signature
        .locate 512-2
        .byte   0x55, 0xAA

Line No.	Rev	Author	Line
1	265	hellwig	`;`
2			`; pbr.s -- the partition boot record`
3			`;`
4
5			`; Runtime environment:`
6			`;`
7			`; This code must be loaded and started at 0xC0010000.`
8			`; It allocates a stack from 0xC0011000 downwards. So`
9			`; it must run within 4K (code + data + stack).`
10			`;`
11			`; This code expects the disk number of the boot disk`
12			`; in $16, the start sector of the disk or partition`
13			`; to be booted in $17 and its size in $18.`
14			`;`
15			`; NOTE: THIS IS A FAKE PARTITION BOOT RECORD!`
16			`; It doesn't load anything, but displays a message`
17			`; where the real thing can be downloaded from.`
18
19			`.set stacktop,0xC0011000 ; top of stack`
20
21			`.set cout,0xC0000020 ; the monitor's console output`
22
23			`; display a message and halt`
24			`start:`
25			`add $29,$0,stacktop ; setup stack`
26			`add $4,$0,strtmsg ; say what is going on`
27			`jal msgout`
28			`j halt`
29
30			`; output message`
31			`; $4 pointer to string`
32			`msgout:`
33			`sub $29,$29,8`
34			`stw $31,$29,4`
35			`stw $16,$29,0`
36			`add $16,$4,0 ; $16: pointer to string`
37			`msgout1:`
38			`ldbu $4,$16,0 ; get character`
39			`beq $4,$0,msgout2 ; done?`
40			`jal chrout ; output character`
41			`add $16,$16,1 ; bump pointer`
42			`j msgout1 ; continue`
43			`msgout2:`
44			`ldw $16,$29,0`
45			`ldw $31,$29,4`
46			`add $29,$29,8`
47			`jr $31`
48
49			`; output character`
50			`; $4 character`
51			`chrout:`
52			`sub $29,$29,4`
53			`stw $31,$29,0`
54			`add $8,$0,cout`
55			`jalr $8`
56			`ldw $31,$29,0`
57			`add $29,$29,4`
58			`jr $31`
59
60			`; halt execution by looping`
61			`halt:`
62			`add $4,$0,hltmsg`
63			`jal msgout`
64			`halt1:`
65			`j halt1`
66
67			`; messages`
68			`strtmsg:`
69	269	hellwig	`.byte 0x0D, 0x0A`
70			`.byte "You didn't expect this tiny program to be"`
71			`.byte 0x0D, 0x0A`
72			`.byte "a full-fledged operating system, did you?"`
73			`.byte 0x0D, 0x0A`
74			`.byte "You can find the real NetBSD for ECO32 on"`
75			`.byte 0x0D, 0x0A`
76			`.byte "GitHub, under the name 'netbsd-on-eco32'."`
77			`.byte 0x0D, 0x0A, 0x0D, 0x0A, 0`
78	265	hellwig	`hltmsg:`
79			`.byte "bootstrap halted", 0x0D, 0x0A, 0`
80
81			`; boot record signature`
82			`.locate 512-2`
83			`.byte 0x55, 0xAA`

Browse

Tools

Subversion Repositories eco32

[/] [eco32/] [trunk/] [disk/] [tools/] [fs-NetBSD/] [mkpboot/] [pbr.s] - Blame information for rev 274