DOS ain't dead

Memory mapped devices from resl mode (Developers)

posted by Khusraw , Bucharest, Romania, 02.03.2020, 19:39

> Freepascal uses an own version of a (probably very old) djgpp stub.asm.
>
> See
> https://svn.freepascal.org/cgi-bin/viewvc.cgi/trunk/rtl/go32v2/v2prt0.as?view=co
>
> It seems it has some support for increasing the ds limit depending on
> __crt0_startup_flags, but I don't know how to set those.
>
> /* Maybe set our DS limit to 4Gb in size if flag set */
> testb $0x80, __crt0_startup_flags /* include/crt0.h */
> jz 2f
> movw $0xffff, %cx
> movl %ecx, %edx
> movw $0x0008, %ax /* reset alias limit to
> -1 */
> int $0x31
> movw %cs, %bx
> movw $0x0008, %ax /* reset DS limit to -1
> */
> int $0x31
> movw %ds, %bx
> movw $0x0008, %ax /* reset DS limit to -1
> */
> int $0x31
> lsl %ebx, %ebx /* Should be -1 */
> incl %ebx
> jz 2f
> andb $0x7f, __crt0_startup_flags /* clear it if failure
> */
> 2:

With DJGPP the flag is not set by default in __crt0_startup_flags (see crt0.S), normally you need to call __djgpp_nearptr_enable (see also nearptr.c).

---
Glory to God for all things

Complete thread:

• Memory mapped devices from resl mode - Laaca, 26.02.2020, 12:11
  • Memory mapped devices from resl mode - Khusraw, 26.02.2020, 12:35
  • Memory mapped devices from resl mode - RayeR, 27.02.2020, 05:27
    • Memory mapped devices from resl mode - Khusraw, 27.02.2020, 09:07
      • Memory mapped devices from resl mode - Laaca, 04.03.2020, 14:01
        • Memory mapped devices from resl mode - Khusraw, 04.03.2020, 15:02
          • Memory mapped devices from resl mode - Laaca, 04.03.2020, 15:08
            • Memory mapped devices from resl mode - Khusraw, 04.03.2020, 15:23
            • Memory mapped devices from resl mode - Khusraw, 04.03.2020, 15:36
            • Memory mapped devices from resl mode - Khusraw, 04.03.2020, 16:55
              • Memory mapped devices from resl mode - Laaca, 04.03.2020, 18:54
                • Memory mapped devices from resl mode - Khusraw, 04.03.2020, 19:33
    • Memory mapped devices from resl mode - Laaca, 27.02.2020, 17:50
      • Memory mapped devices from resl mode - Khusraw, 27.02.2020, 20:25
        • Memory mapped devices from resl mode - KormaX, 01.03.2020, 22:23
          • Memory mapped devices from resl mode - Zyzzle, 02.03.2020, 06:10
            • Memory mapped devices from resl mode - KormaX, 12.05.2020, 11:21
        • Memory mapped devices from resl mode - marcov, 02.03.2020, 15:43
          • Memory mapped devices from resl mode - Khusraw, 02.03.2020, 19:39
            • Memory mapped devices from resl mode - marcov, 02.03.2020, 23:13
              • Memory mapped devices from real mode - Rugxulo, 03.03.2020, 06:11
                • Memory mapped devices from real mode - marcov, 03.03.2020, 10:12
                  • Memory mapped devices from real mode - Rugxulo, 03.03.2020, 22:12
              • Memory mapped devices from resl mode - Khusraw, 03.03.2020, 13:34