ack/plat/msdos386/libsys/sys_isopen.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

26 lines
338 B
ArmAsm

#
! $Source$
! $State$
! $Revision$
! Declare segments (the order is important).
.sect .text
.sect .rom
.sect .data
.sect .bss
.sect .text
! Say whether a given file descriptor number refers to a valid open file
! descriptor.
.define __sys_isopen
__sys_isopen:
mov ebx, 4(esp)
mov eax, 0x4400
int 0x21
sbb eax, eax
inc eax
ret