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save/restore %ebx, %esi and %edi when calling bios routines.

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Don't save/restore %ecx and %edx.
Reset segment limits when going to real mode.
Reviewed by:	phk (briefly)
This commit is contained in:
tegge 1997-05-12 23:00:32 +00:00
parent a78905acf9
commit 7e545378b6
1 changed files with 38 additions and 12 deletions
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50
sys/i386/boot/netboot/start2.S
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@ -2,7 +2,8 @@
#define STACKADDR 0xe000 /* Needs to be end of bss + stacksize */
#define KERN_CODE_SEG 0x08
#define KERN_DATA_SEG 0x10
#define REAL_MODE_SEG 0x18
#define REAL_MODE_CSEG 0x18
#define REAL_MODE_DSEG 0x20
#define CR0_PE 1
#define opsize .byte 0x66
@ -127,8 +128,9 @@ CURRTICKS - Get Time
_currticks:
push %ebp
mov %esp,%ebp
push %ecx
push %edx
push %ebx
push %esi
push %edi
xor %edx,%edx
call _prot_to_real
xor %eax,%eax
@ -139,8 +141,9 @@ _currticks:
shl $16,%ecx
mov %edx,%eax
or %ecx,%eax
pop %edx
pop %ecx
pop %edi
pop %esi
pop %ebx
pop %ebp
ret
@ -151,8 +154,9 @@ PUTCHAR - Print a character
_putchar:
push %ebp
mov %esp,%ebp
push %ecx
push %ebx
push %esi
push %edi
movb 8(%ebp),%cl
call _prot_to_real
opsize
@ -162,8 +166,9 @@ _putchar:
int $0x10
opsize
call _real_to_prot
pop %edi
pop %esi
pop %ebx
pop %ecx
pop %ebp
ret
@ -175,6 +180,8 @@ _getchar:
push %ebp
mov %esp,%ebp
push %ebx
push %esi
push %edi
call _prot_to_real
movb $0x0,%ah
int $0x16
@ -183,6 +190,8 @@ _getchar:
call _real_to_prot
xor %eax,%eax
movb %bl,%al
pop %edi
pop %esi
pop %ebx
pop %ebp
ret
@ -195,6 +204,8 @@ _iskey:
push %ebp
mov %esp,%ebp
push %ebx
push %esi
push %edi
call _prot_to_real
xor %ebx,%ebx
movb $0x1,%ah
@ -207,6 +218,8 @@ _iskey:
call _real_to_prot
xor %eax,%eax
movb %bl,%al
pop %edi
pop %esi
pop %ebx
pop %ebp
ret
@ -298,8 +311,17 @@ _prot_to_real:
sub $RELOC,%eax /* Adjust return address */
push %eax
sub $RELOC,%esp /* Adjust stack pointer */
ljmp $REAL_MODE_SEG, $1f /* jump to a 16 bit segment */
/* Prepare %ax while we're still in a mode that gas understands. */
movw $REAL_MODE_DSEG, %ax
ljmp $REAL_MODE_CSEG, $1f-RELOC /* jump to a 16 bit segment */
1:
mov %ax, %ds
mov %ax, %ss
mov %ax, %es
mov %ax, %fs
/* clear the PE bit of CR0 */
mov %cr0, %eax
opsize
@ -417,11 +439,15 @@ gdt:
.word 0xffff, 0
.byte 0, 0x93, 0xcf, 0
/* 16 bit real mode */
.word 0xffff, 0
.byte 0, 0x9b, 0x0f, 0
/* 16 bit real mode code segment */
.word 0xffff, RELOC & 0xffff
.byte (RELOC>>16), 0x9b, 0x00, (RELOC>>24)
/* 16 bit real mode data segment */
.word 0xffff, RELOC & 0xffff
.byte (RELOC>>16), 0x93, 0x00, (RELOC>>24)
.align 4
gdtarg:
.word 0x1f /* limit */
.word 0x27 /* limit */
.long gdt /* addr */