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