diff options
| -rw-r--r-- | sys/i386/boot/netboot/start2.S | 50 |
1 files changed, 38 insertions, 12 deletions
diff --git a/sys/i386/boot/netboot/start2.S b/sys/i386/boot/netboot/start2.S index 6d0d113..c81d87a 100644 --- a/sys/i386/boot/netboot/start2.S +++ b/sys/i386/boot/netboot/start2.S @@ -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 */ |
