minix/sys/arch/i386/stand/lib/dos_file.S
2012-02-09 18:48:13 +01:00

203 lines
2.9 KiB
ArmAsm

/* $NetBSD: dos_file.S,v 1.6 2009/11/21 11:52:57 dsl Exp $ */
/* extracted from Tor Egge's patches for NetBSD boot */
#include <machine/asm.h>
/*
# MSDOS call "INT 0x21 Function 0x3d" to open a file.
# Call with %ah = 0x3d
# %al = 0x0 (access and sharing modes)
# %ds:%dx = ASCIZ filename
# %cl = attribute mask of files to look for
*/
.globl _C_LABEL(doserrno)
_C_LABEL(doserrno): .long 1
ENTRY(dosopen)
.code32
pushl %ebp
movl %esp, %ebp
pushl %edx
pushl %ebx
pushl %esi
pushl %edi
movl 0x8(%ebp), %edx # File name.
call _C_LABEL(prot_to_real) # enter real mode
.code16
push %ds
movl %edx, %eax
shrl $4, %eax
mov %ds, %si
add %si, %ax
mov %ax, %ds
and $0xf, %dx
movb $0x3d, %ah # Open existing file.
movb $0x0 , %al # ro
sti
int $0x21
cli
pop %ds
jnc ok1
mov %ax, _C_LABEL(doserrno)
movl $-1, %edx
jmp err1
ok1:
movl $0,%edx
mov %ax, %dx
err1:
calll _C_LABEL(real_to_prot) # back to protected mode
.code32
movl %edx, %eax # return value in %eax
popl %edi
popl %esi
popl %ebx
popl %edx
popl %ebp
ret
ENTRY(dosread)
.code32
pushl %ebp
movl %esp, %ebp
pushl %ebx
pushl %ecx
pushl %edx
pushl %esi
pushl %edi
movl 0x8(%ebp), %ebx # File handle
movl 0xc(%ebp), %edx # Buffer.
movl 0x10(%ebp), %ecx # Bytes to read
call _C_LABEL(prot_to_real) # enter real mode
.code16
push %ds
movl %edx, %eax
shrl $4, %eax
mov %ds, %si
add %si, %ax
mov %ax, %ds
and $0xf, %dx
movb $0x3f, %ah # Read from file or device
sti
int $0x21
cli
pop %ds
jnc ok2
mov %ax, _C_LABEL(doserrno)
movl $-1, %edx
jmp err2
ok2:
movl $0,%edx
mov %ax, %dx
err2:
calll _C_LABEL(real_to_prot) # back to protected mode
.code32
movl %edx, %eax # return value in %eax
popl %edi
popl %esi
popl %edx
popl %ecx
popl %ebx
popl %ebp
ret
ENTRY(dosclose)
.code32
pushl %ebp
movl %esp, %ebp
pushl %ebx
pushl %esi
pushl %edi
movl 0x8(%ebp), %ebx # File handle
call _C_LABEL(prot_to_real) # enter real mode
.code16
movb $0x3e, %ah # Close file.
sti
int $0x21
cli
jnc ok3
mov %ax, _C_LABEL(doserrno)
movl $-1, %ebx
jmp err3
ok3:
movl $0, %ebx
err3:
calll _C_LABEL(real_to_prot) # back to protected mode
.code32
movl %ebx, %eax # return value in %eax
popl %edi
popl %esi
popl %ebx
popl %ebp
ret
ENTRY(dosseek)
.code32
pushl %ebp
movl %esp, %ebp
pushl %ebx
pushl %ecx
pushl %edx
pushl %esi
pushl %edi
movl 0x8(%ebp), %ebx # File handle
movl 0xc(%ebp), %ecx # Offset
movl 0x10(%ebp) , %edx # whence
call _C_LABEL(prot_to_real) # enter real mode
.code16
movb $0x42, %ah # Seek
movb %dl, %al # whence
mov %cx, %dx #offs lo
shrl $0x10, %ecx #offs hi
sti
int $0x21
cli
jnc ok4
mov %ax, _C_LABEL(doserrno)
movl $-1, %edx
jmp err4
ok4:
shll $0x10, %edx #new ofs hi
mov %ax, %dx #new ofs lo
err4:
calll _C_LABEL(real_to_prot) # back to protected mode
.code32
movl %edx, %eax # return value in %eax
popl %edi
popl %esi
popl %edx
popl %ecx
popl %ebx
popl %ebp
ret