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Some systems (esp. those with a Promise IDE controller card) seem to

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destroy %dl (drive number) across the 'disk reset' command.
Preserve %dl across that call and all registers across the disk reads.
Reorder the code to remove some long conditional jumps to save space.
This commit is contained in:
dsl 2003-08-09 20:57:45 +00:00
parent 7061f16abb
commit 221f1dff47
1 changed files with 57 additions and 55 deletions
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112
sys/arch/i386/stand/bootxx/pbr.S
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@ -1,4 +1,4 @@
/* $NetBSD: pbr.S,v 1.5 2003/08/05 15:14:49 dsl Exp $ */
/* $NetBSD: pbr.S,v 1.6 2003/08/09 20:57:45 dsl Exp $ */
/*-
* Copyright (c) 2003 The NetBSD Foundation, Inc.
@ -124,7 +124,9 @@ start0:
mov $0xfffc, %sp
/* A 'reset disk system' request is traditional here... */
push %dx /* some BIOS zap %dl here :-( */
int $0x13 /* ah == 0 from code above */
pop %dx
/* Read from start of disk */
movw $0x0001, %cx /* track zero sector 1 */
@ -136,7 +138,7 @@ start0:
xorl %ebp, %ebp /* pass sector 0 to next stage */
movl (%bx), %eax /* mbr code shouldn't even have ... */
cmpl R(start), %eax /* ... a jmp at the start. */
je pbr_read_ok
je pbr_read_ok1
/* Now scan the mbr partition table for a netbsd partition */
@ -175,31 +177,6 @@ scan_ptn_tbl:
call read_lba
jmp scan_ptn_tbl
/*
* Something went wrong,
* Output error code,
*/
read_err:
set_err(ERR_READ)
error:
#ifdef TERSE_ERROR
movb %al, errcod
movw $errtxt, %si
call message
#else
push %ax
movw $errtxt, %si
call message
pop %si
call message
movw $newline, %si
call message
#endif
1: sti
hlt
jmp 1b
no_netbsd_ptn:
/* Specific sector not found: try again looking for first NetBSD ptn */
testl %esi, %esi
@ -208,6 +185,19 @@ no_netbsd_ptn:
xorl %esi, %esi
jmp start
/*
* Sector below CHS limit
* Do a cylinder-head-sector read instead
* I believe the bios should do reads that cross track boundaries.
* (but the read should start at the beginning of a track...)
*/
read_chs:
movb 1(%di), %dh /* head */
movw 2(%di), %cx /* ch=cyl, cl=sect */
call chs_read
pbr_read_ok1:
jmp pbr_read_ok
/*
* Active partition pointed to by di.
*
@ -261,32 +251,12 @@ boot:
pop %dx /* recover drive nmber */
cmp %bp, %ax
jne check_lba
/* Read using CHS */
/*
* Sector below CHS limit
* Do a cylinder-head-sector read instead
* I believe the bios should do reads that cross track boundaries.
* (but the read should start at the beginning of a track...)
*/
read_chs:
movb 1(%di), %dh /* head */
movw 2(%di), %cx /* ch=cyl, cl=sect */
call chs_read
jmp pbr_read_ok
chs_read:
movw $BOOTADDR, %bx /* es:bx is buffer */
movw $0x200 + BOOTXX_SECTORS, %ax /* command 2, xx sectors */
int $0x13
jc read_err
ret
je read_chs
check_lba:
#ifndef NO_LBA_CHECK
#ifdef NO_LBA_CHECK
jmp boot_lba
#else
/*
* Determine whether we have int13-extensions, by calling
* int 13, function 41. Check for the magic number returned,
@ -306,9 +276,31 @@ check_lba:
testb $1, %cl
jnz boot_lba
1: set_err(ERR_NO_LBA)
jmp error
#endif /* NO_LBA_CHECK */
/*
* Something went wrong,
* Output error code,
*/
error:
#ifdef TERSE_ERROR
movb %al, errcod
movw $errtxt, %si
call message
#else
push %ax
movw $errtxt, %si
call message
pop %si
call message
movw $newline, %si
call message
#endif
1: sti
hlt
jmp 1b
boot_lba:
call read_lba
@ -326,15 +318,25 @@ pbr_read_ok:
/* Read disk using int13-extension parameter block */
read_lba:
push %si
pusha
movw $lba_info, %si /* ds:si is ctl block */
movb $0x42, %ah
do_read:
int $0x13
pop %si
popa
jc read_err
set_err(ERR_READ)
jc error
ret
/* Read using CHS */
chs_read:
movw $BOOTADDR, %bx /* es:bx is buffer */
pusha
movw $0x200 + BOOTXX_SECTORS, %ax /* command 2, xx sectors */
jmp do_read
_errtxt: .ascii "Error " /* runs into newline... */
_errcod: .byte 0 /* ... if errcod set */
_newline: