ack/plat/msdos386/libsys/sys_rawopen.s
tkchia 15955282f6 plat/msdos386: fix some issues in libsys code
- ensure es = ds = ss upon exit of each C runtime function
 - clear upper 16 bits of ebx before setting them to 0x0021,
   when invoking interrupt_ptr to simulate a RM int 0x21
 - make _sys_exists use the transfer buffer (which it needs)
 - make _sys_rawread properly handle an end-of-file read
   (zero bytes read)
 - make argument to _sys_seterrno short --- after a failed
   int 0x21 call, only the lower 16 bits of eax hold the MS-DOs
   error code
 - _sys_rawlseek accepts only 3 longword arguments, not 4
   (the offset is only 1 longword)
 - other minor fixes
2022-08-24 15:17:04 +00:00

48 lines
588 B
ArmAsm

#
! $Source$
! $State$
! $Revision$
! Declare segments (the order is important).
.sect .text
.sect .rom
.sect .data
.sect .bss
.sect .text
! Open an existing file.
.define __sys_rawopen
__sys_rawopen:
! Copy filename to transfer buffer.
mov ebx, esp
push esi
push edi
mov esi, 4(ebx)
movzx edi, (transfer_buffer_ptr)
mov es, (pmode_ds)
cld
1:
lodsb
stosb
testb al, al
jnz 1b
! Make the DOS call.
movb ah, 0x3d
o16 mov dx, (transfer_buffer_ptr)
movb al, 8(ebx)
mov ebx, 0x210000
callf (interrupt_ptr)
pop edi
pop esi
push ss
pop es
jmp .sys_axret