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Changed stage1 to report error strings instead of single characters.

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Removed display of characters on success, as it was confusing.
This commit is contained in:
erich 1998-08-20 20:52:57 +00:00
parent 30aa899004
commit ae07073cec
1 changed files with 78 additions and 120 deletions
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198
stage1/stage1.S
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@ -25,7 +25,7 @@
#define BPBEND 0x3e
#define PARTSTART 0x1be /* starting address of partition table */
#define PARTEND 0x1fe /* ending addres of the partition table */
#define MINPARAMSIZ 18 /* size of extra data parameters */
#define MINPARAMSIZ 13 /* size of extra data parameters */
#define LISTSIZ 8 /* size of sector list */
#define REALSTACK 0x2000 /* stack for this code and BIOS calls */
#define BUFFERSEG 0x7000 /* segment address of disk buffer, the
@ -34,28 +34,6 @@
#define BIOS_HD_FLAG 0x80 /* bit set in BIOS drive number to designate
a hard disk vs. a floppy */
/* data for debugging */
#define CHAR_1 '1'
#define CHAR_2 '2'
#define CHAR_3 '3'
#define CHAR_4 '4'
#define CHAR_5 '5'
#define CHAR_6 '6'
#define CHAR_a 'a'
/* messages displayed at all times */
#define CHAR_S 'S'
#define CHAR_J 'J'
/* error messages */
/* Read error (trying to read non-existent sector, perhaps) */
#define CHAR_R 'R'
/* Geometry translation error (off of probed geometry) */
#define CHAR_G 'G'
/* Disk geometry probe failed! */
#define CHAR_P 'P'
/* Absolute addresses
This makes the assembler generate the address without support
from the linker. (ELF can't relocate 16bit addresses!) */
@ -67,9 +45,9 @@
#define REL(x) .word x-0f; 0:
#define RELB(x) .byte x-0f; 0:
/* Print message
movb $x, %al; call message */
#define MSG(x) movb $x, %al; .byte 0xe8; REL(message)
/* Print message string
movw $x, %cx; call message */
#define MSG(x) movw $x, %aw; .byte 0xe8; REL(message)
.file "stage1.S"
@ -122,18 +100,18 @@ cylinders:
after_BPB:
/* general setup */
cli /* we're not safe here! */
/* set up %ds and %ss as offset from 0 */
xorw %ax, %ax
movw %ax, %ds
movw %ax, %es
cld /* sets the copy direction to forward */
movw %ax, %ss
/* set up the REAL stack */
movw %ax, %ss
movw $REALSTACK, %sp
sti /* we're safe again */
/*
* Check if we have a forced disk reference here
*/
@ -147,10 +125,6 @@ after_BPB:
/* save drive reference first thing! */
pushw %dx
/* tell the user that we're here before anything else! */
MSG(CHAR_S)
#ifndef BIOS_PROBE_ONLY
/*
* Jump to floppy probe instead of the hard disk probe ?
*/
@ -159,11 +133,6 @@ after_BPB:
/* jz floppy_probe */
.byte 0x0f, 0x84; REL(floppy_probe)
#endif
#ifdef DEBUG
MSG(CHAR_6)
#endif
/*
* Determine the hard disk geometry from the BIOS!
@ -172,8 +141,8 @@ after_BPB:
int $0x13
/* if BIOS geometry call fails, display error and die! */
/* jc probe_error (16-bit)*/
.byte 0x0f, 0x82; REL(probe_error)
/* jc hd_probe_error (16-bit)*/
.byte 0x0f, 0x82; REL(hd_probe_error)
final_init:
xorb %ah, %ah
@ -211,10 +180,6 @@ final_init:
/* this is the loop for reading the secondary boot-loader in */
bootloop:
#ifdef DEBUG
MSG(CHAR_2)
#endif
/* update position to load from */
subw $LISTSIZ, %di
@ -254,10 +219,6 @@ bootloop:
setup_sectors:
#ifdef DEBUG
MSG(CHAR_3)
#endif
/* determine the maximum sector length of this read */
/* movw (%si), %ax */ /* get number of sectors per track/head */
.byte 0x8b, 0x04
@ -275,25 +236,13 @@ setup_sectors:
/* movw 4(%di), %ax */ /* if less than, set to total */
.byte 0x8b, 0x45, 0x04
#ifdef DEBUG
pushw %ax
MSG(CHAR_4)
popw %ax
#endif
more_sectors:
/* subw %ax, 4(%di) */ /* subtract from total */
.byte 0x29, 0x45, 0x04
/* this is the loop for taking care of BIOS translation (ugh!) */
#ifdef DEBUG
pushw %ax
addb $CHAR_a, %al
/* call message */
.byte 0xe8; REL(message)
popw %ax
#endif
/*
* This is the loop for taking care of BIOS geometry translation (ugh!)
*/
/* movb 3(%di), %dl */ /* get high bits of cylinder */
.byte 0x8a, 0x55, 0x03
@ -338,16 +287,15 @@ more_sectors:
int $0x13
/* jc read_error */
.byte 0x72
RELB(read_error)
.byte 0x72; RELB(read_error)
movw %es, %ax
movw %ax, %fs /* load source segment */
/* load addresses for copy from disk buffer to destination */
/* movw 6(%di), %es */ /* load destination segment */
.byte 0x8e, 0x45, 0x06
movw $BUFFERSEG, %ax
movw %ax, %fs /* load source segment */
/* restore %ax */
popw %ax
@ -368,6 +316,7 @@ more_sectors:
xorw %di, %di /* zero offset of destination addresses */
xorw %si, %si /* zero offset of source addresses */
cld /* sets the copy direction to forward */
/* perform copy */
rep /* sets a repeat */
@ -385,10 +334,6 @@ more_sectors:
/* je bootloop */
.byte 0x0f, 0x84; REL(bootloop)
#ifdef DEBUG
MSG(CHAR_5)
#endif
/* find out the next BIOS set to load in */
/* movb $0, (%di) */ /* set the sector start */
.byte 0xc6, 0x05, 0
@ -423,46 +368,42 @@ update_heads:
/* movb %al, 1(%di) */ /* store new head number */
.byte 0x88, 0x45, 0x01
#ifdef DEBUG
addb $CHAR_a, %al
/* call message */
.byte 0xe8; REL(message)
/* movb 2(%di), %al */
.byte 0x8a, 0x45, 0x02
addb $CHAR_a, %al
/* call message */
.byte 0xe8; REL(message)
#endif
/* jump to "setup_sectors" to determine length of the new read */
/* jmp setup_sectors */
.byte 0xe9; REL(setup_sectors)
/* END OF MAIN LOOP */
/*
* BIOS Geometry translation error (past the end of the disk geometry!).
*/
geometry_error:
movb $CHAR_G, %al
movw $geometry_error_string, %si
/* call message */
.byte 0xe8; REL(message)
/* jmp display_error (8-bit) */
.byte 0xeb; RELB(display_error)
.byte 0xeb; RELB(general_error)
/*
* Disk probe failure.
*/
probe_error:
movb $CHAR_P, %al
hd_probe_error:
movw $hd_probe_error_string, %si
/* call message */
.byte 0xe8; REL(message)
/* jmp display_error (8-bit) */
.byte 0xeb; RELB(display_error)
.byte 0xeb; RELB(general_error)
/*
* Read error on the disk.
*/
read_error:
movb $CHAR_R, %al
movw $read_error_string, %si
/* call message */
.byte 0xe8; REL(message)
display_error:
general_error:
movw $general_error_string, %si
/* call message */
.byte 0xe8; REL(message)
@ -470,27 +411,46 @@ display_error:
stop: /* jmp stop (8-bit) */
.byte 0xeb; RELB(stop)
geometry_error_string: .string "Geom"
hd_probe_error_string: .string "Hard Disk"
read_error_string: .string "Read"
general_error_string: .string " Error"
/*
* message: write the character in %al to the console, %ah gets trashed.
* message: write the string pointed to by %si
*
* WARNING: trashes %si, %ax, and %bx
*/
message:
/*
* Use BIOS "int 10H Function 0Eh" to write character in teletype mode
* %ah = 0xe %al = character
* %bh = page %bl = foreground color (graphics modes)
*/
pushw %bx
1:
movw $0x0001, %bx
movb $0xe, %ah
int $0x10 /* display a byte */
popw %bx
incw %si
message:
/* movb (%si), %al */
.byte 0x8a, 0x4
cmpb $0, %al
/* jne 1b */
.byte 0x75; RELB(1b) /* if not end of string, jmp to display */
/* ret */
.byte 0xc3
lastlist:
/*
* This area is an empty space between the main body of code below which
* grows up (fixed after compilation, but between releases it may change
* in size easily), and the lists of sectors to read, which grows down
* from a fixed top location.
*/
/*
* This data area is for keeping general parameters.
*/
@ -517,28 +477,18 @@ lastlist:
.word 0x0800 /* this is the segment of the starting address
to load the data into */
#endif
firstlist:
firstlist: /* this label has to be after the list data!!! */
.byte 0xff /* the disk to load stage2 from */
/* 0xff means use the boot drive */
/* the above label has to be after its data!!! */
/*
* Jump here when all data loading is done.
* Jump here when all data loading is done. This
* goes to the second stage bootloader.
*/
bootit:
/*
* Tell the user we're going to the next stage...
*/
MSG(CHAR_J)
popw %dx /* this makes sure %dl is our "boot" drive */
/*
* ljmp to the second stage boot loader.
*/
/* ljmp $myoffset, $myseg */
.byte 0xea
#ifdef STAGE1_5
@ -552,7 +502,7 @@ bootit:
*
* DO NOT MOVE THIS!!!
*/
.byte 1, 0
.byte 2, 0
/*
* This is where an MBR would go if on a hard disk. The code
@ -562,13 +512,12 @@ bootit:
. = _start + PARTSTART
#ifndef BIOS_PROBE_ONLY
probe_values:
.byte 36, 18, 15, 9, 0
floppy_probe:
/*
* Perform floppy probe!
* Perform floppy probe.
*/
movw $ABS(probe_values-1), %si
@ -586,9 +535,21 @@ probe_loop:
/* if number of sectors is 0, display error and die */
cmpb $0, %cl
/* je probe_error (16-bit)*/
.byte 0x0f, 0x84; REL(probe_error)
/* jne 1f (8-bit) */
.byte 0x75; RELB(1f)
/*
* Floppy disk probe failure.
*/
movw $fd_probe_error_string, %si
/* call message */
.byte 0xe8; REL(message)
/* jmp display_error (16-bit) */
.byte 0xe9; REL(general_error)
fd_probe_error_string: .string "Floppy"
1:
/* perform read */
movw $REALSTACK, %bx
movw $0x201, %ax
@ -607,10 +568,7 @@ probe_loop:
/* jmp final_init */
.byte 0xe9; REL(final_init)
#endif /* !BIOS_PROBE_ONLY */
. = _start + PARTEND
/* the last 2 bytes in the sector 0 contain the signature */
.word SIGNATURE