delorie.com/archives/browse.cgi   search  
Mail Archives: djgpp/1995/05/29/23:56:24

From: Elio Tondo <elio AT pvax DOT ICO DOT Olivetti DOT Com>
Subject: Re: Compiling gdb, dpmi DS:VRAM hack.
To: sandmann AT praline DOT no DOT NeoSoft DOT com (Charles Sandmann)
Date: Mon, 29 May 1995 14:17:03 +0200 (MET DST)
Cc: elio AT pvax DOT ICO DOT Olivetti DOT Com (Elio Tondo), djgpp AT sun DOT soe DOT clarkson DOT edu

> Yes, the system() in V1.x will sometimes break the VRAM hack, since the
> memory is completely deallocated and written to the swap file.  Since we 
> moved to COFF images in V1.11 this really hasn't been needed, and goes away
> in V2 (which expects the DPMI provider to page if necessary).

Any comments about the "reliability" I noticed when only calling malloc() and
not system()? On May 2 you wrote that a custom malloc was needed; can you
give us all some more details about the conditions that can trigger the
modification of the segment linear base address, and any way to avoid that?

> You can do this with a DPMI 1.0 host but not with a DPMI 0.9 host.  
> Unfortunately DPMI 0.9 is here to stay - even Win 95 only provides DPMI 0.9.

Yes, and this is the problem. I know that DPMI 1.0 has its own mmap()-like
functionality; I was only trying to understand if some trick can be used, given
that the page tables are global (is this right?) and maybe there is some way
to circumvent the DPMI protections and access them directly.

   Elio
 _____________________________________________________________________________
|  __           ___                | Olivetti - Viale Gramsci 12 - Pisa, Italy
| |_  | .  _     |  _   _   _|  _  | Tel:  +39-50-516554   Fax:  +39-50-502664
| |__ | | (_)    | (_) | | (_| (_) | elio AT olivetti DOT com | Standard disclaimers.

- Raw text -


  webmaster     delorie software   privacy  
  Copyright 2019   by DJ Delorie     Updated Jul 2019