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/               DPMILD32 - PE binary Loader                                   /
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 0.   Contents

      1.  Introduction
      2.  Requirements
      3.  Starting DPMILD32 from the Command-Line
      4.  Environment variable DPMILDR
      5.  Win32 API Emulation
      6.  Memory Model
      7.  Loader API
      8.  PX executables
      9.  Support for NE binaries
     10.  Debugging Support
     11.  Returncodes
     12.  Error Messages
     13.  Restrictions
     14.  History
     15.  Copyright


 1.  Introduction

     DPMILD32 is HX's PE loader. Both types of binaries, applications and
     dlls are supported, and dlls may be loaded statically or dynamically.
     HX's Win32 emulation is based on the functions DPMILD32 supplies and
     won't work without it.

     Although DPMILD32.EXE is a DOS MZ-executable and can be started
     by simply typing its name in the command line, it usually is invoked
     automatically. This is done either with the help of HXLdr32, a DOS
     TSR, or by a stub (DPMIST32.BIN) which has been added to the PE binary.

     DPMILD32 will search for the binary to load (.EXE extension may be
     omitted) in the current directory and then in all directories of the
     PATH environment variable.

     One of DPMILD32's first tasks is to check if a DPMI host is active.
     If this is not the case, it will try to silently start HDPMI32.EXE,
     which will be found only if it is located in the same directory as
     DPMILD32.EXE.

     Besides PE binaries DPMILD32 also knows NE binaries, but this is
     rarely needed.


 2.  Requirements

     þ DPMILD32 expects the DPMI host to implement Int 21h API translation. 
       That's why it does not run with CWSDPMI.

     þ Many Win32 applications are linked so they must be loaded at a 
       fixed location in address space (usually 0x400000). This is a problem
       for most DPMI hosts. The DPMI V0.9 API has no function to allocate
       memory with a given base address, it was introduced in the DPMI V1.0
       specifications (Int 31h, AX=0504h [allocate committed/uncommitted
       linear memory]). Some V0.9 hosts have this function implemented, but
       in practice they often fail. That's why DPMILD32 will need HDPMI or
       DOSEMU as underlying hosts to successfully load such binaries.

     þ To support files with long names (LFN) the underlying DPMI host
       must supply API translation for LFN (when running in a Windows NT/XP
       DOS box, the loader's LFN support is disabled).


 3.  Starting DPMILD32 from the Command-Line

     If DPMILD32 is launched manually, the syntax is as follows:

       DPMILD32 [ options ] name_of_binary_to_load

     valid options are:
       - g = instructs DPMILD32 to load a console application as if it is
             a GUI application, that is, it will try to load HXGUIHLP.DLL
             before the application's entry point is called.


 4.  Environment variable DPMILDR

     By setting environment variable DPMILDR one can control some aspects
     of the loader's behaviour. The variable is a number whose individual bits
     are interpreted as follows:

     - bit 0 (DPMILDR=1): forces a breakpoint at program entry point. If no
       debugger is present, this switch has no effect.

     - bit 1 (DPMILDR=2): prevents the loader from moving itself into extended
       memory. It remains in conventional DOS memory after switching to
       protected mode. 

     - bit 2 (DPMILDR=4): disables support for loading 32-Bit NE applications.

     - bit 3 (DPMILDR=8): prevents loader from trying to run another
       application in the current DPMI client. Instead the int 21h, ax=4B00h
       call is routed to the next handler in the chain. This is useful if
       the applications to run cannot share the client, which is mostly the
       case for Win32 applications where the relocation information has 
       been stripped from the binary. To make this finally work as expected,
       it must be ensured that the DPMI host will run clients in separate
       address spaces (see HDPMI docs for details).

     - bit 4 (DPMILDR=16): don't protect read-only sections. Without this
       option set DPMILDR will try to
         a) protect all read-only sections and to
         b) uncommit memory belonging to discardable sections.
       This will only succeed if the DPMI host supports DPMI function 0507h.
       There exist some apps written with WDOSX dos extender which write
       to sections marked as readonly, thus causing a GPF with DPMILD32
       if running on a DPMI 1.0 host. To avoid this use this switch.

     - bit 5 (DPMILDR=32): don't use any DPMI 1.0 function. This option
       is automatically set for Windows NT/2k/XP because of the very
       buggy DPMI support (DOSX.EXE) on these systems.               

     - bit 6 (DPMILDR=64): ignore SEM_NOOPENFILEERRORBOX flag. With this
       setting the loader will display errors during module loads in any
       case.

     - bit 7 (DPMILDR=128): ignore unresolved imports. With this
       setting the loader will continue to load and execute a binary even
       if an unresolved import has been detected. If such an import is 
       called, however, an error message is displayed and the application
       will exit.

     - bit 8 (DPMILDR=256): try to load NE debug dll DEBUGO32.DLL
       at startup. This is mainly for compatibility with older versions,
       where the loader has tried to load this dll unconditionally.
       
     - bit 9 (DPMILDR=512): <not used currently>

     - bit 10 (DPMILDR=1024): try to load dlls at their prefered load
       address. Usually the memory block for a dll's image is allocated
       without a given linear address. This option has no effect if dpmi
       host doesn't support function int 31h, ax=504h.

     - bit 11 (DPMILDR=2048): alloc 32-bit flat data selector as "expand
       down". This will provide memory access protection for linear address 
       range 0-3FFh. This is intended for debugging purposes to catch NULL
       pointer usage.

       *** Warning: the MS Windows 9x DPMI hosts will get confused by 
       *** "expand down" data segments and cause a GPF. Other hosts may 
       *** also have problems. Compatible are: HDPMI, DOSEMU, DPMIONE.
       *** WinXP SR2 fails, but previous versions work.

     - bit 12 (DPMILDR=4096): restrict size of stack to be allocated to
       128 kB. This usually is enough and may allow some PE apps to be run
       on systems with little memory, because DPMILD32 will allocate the
       stack as committed memory. If HDPMI is used, setting HDPMI=2 will
       add DOS memory to the memory pool, so with these 2 settings it may
       be possible to run some PE binaries on 2 MB machines ;-).

     - bit 13 (DPMILDR=8192): allow Win32 GUI apps to be loaded when
       running in a Windows DOS box. Usually DPMILD32 refuses to load
       such applications when running in this environment, because this 
       allows to launch Win32 GUI apps from DPMI applications.


 5.  Win32 API Emulation

     During the load process some imported dlls will be "replaced"
     by DPMI compatible versions. These are:

     KERNEL32.DLL ->  DKRNL32.DLL
     ADVAPI32.DLL ->  DADVAPI.DLL
     USER32.DLL   ->  DUSER32.DLL
     GDI32.DLL    ->  DGDI32.DLL
     DDRAW.DLL    ->  DDDRAW.DLL

     This feature allows dual-mode applications. Such apps run as normal Win32
     apps in Win32 environments and will run as DPMI clients in non-Win32
     environments. 

     Please note that some exports supplied by DKRNL32.DLL, such as 
     CreateProcess, LoadLibrary, FreeLibrary, GetProcAddress, GetModuleHandle
     or GetModuleFileName are just thin wrappers around the loader's int 21h
     API. This means that DKRNL32 can only work in conjunction with DPMILD32,
     other PE loaders won't do the job. 


 6.  Memory Model

     As in Win32, PE binaries loaded by DPMILD32 execute in a flat, zero
     based environment with a 4 GB 32-bit code selector in CS and a 4 GB
     32-bit data selector in SS, DS and ES. FS and GS are not used, they
     should have been initialized to ZERO by the DPMI host. 

      Processes in a Win32 environment execute in separate address spaces.
     For PE applications loaded with DPMILD32 this is not true. In fact,
     DPMILD32 has no means to support several address spaces. There 
     exist 2 workarounds:

     - set DPMILDR=8: as described below this may result in each PE   
       application having its own copy of DPMILD32 and HDPMI32, so in fact
       running in a privately owned address space. Will most likely work
       with HDPMI only.
     - use loader API Int 21h, ax=4B92: this is a simple way to ensure
       that each application has its own copies of dlls loaded. There is
       one address space for all apps, but if they behave well this should
       be no problem. However, running several applications in one address
       space most likely requires relocation information not being stripped
       from the binaries.

     DPMILD32 will always allocate the application's stack as committed
     memory, since there exists no "Guard Page" mechanism in DPMI. This may
     cause binaries defining a very large 'reserved' stack to run out of
     memory.


 7.  Loader API

     DPMILD32 installs a simple API for loading PE/NE binaries.

     þ Int 21h, AX=4B00h (LoadModule/LoadLibrary): Loads a PE/NE module
       dynamically.
       Input:
         DS:EDX - must hold a far32 pointer to the name of the module to
                  load
         ES:EBX - if an application is to be loaded, these must hold a
                  far32 pointer to a execute parameter block.
       Output:
         EAX - if a dll has been loaded returns the module handle
               (or 0 if an error occured)
         C - error

       Applications will execute synchronously, like in standard DOS,
       and a calling application will regain control when the loaded
       application has terminated.
       For dlls, the module handle returned in EAX is - for PE modules -
       simply the address the image has been loaded to. If the dll was
       a NE module, the module handle will be a selector containing
       the NE module header and HIWORD(eax) will be zero.

     þ Int 21h, AX=4B80h (FreeLibrary): Free a PE/NE module.
       Input:
         EDX - the handle of the module to free
       Output:
         EAX - 0 indicates a failure

     þ Int 21h, AX=4B81h (GetProcAddress): Get the address of an export
       in a PE dll. 
       Input:
         EBX - holds the module handle of the dll
         EDX - holds the linear address of the export's name or - if
               HIWORD(EDX) is zero - should contain the export's number 
       Output:
         EAX - the address of the export. EAX=0 will indicate a failure.
         C - error

     þ Int 21h, AX=4B82h (GetModuleHandle): Get the handle of a PE module.
       Input:
         EDX - holds the linear address of the name of the module.
         May be NULL, in which case the module handle of the binary
         attached to the current task is returned.
       Output:
         EAX - returns the module's handle. EAX=0 indicates a failure.
         if EDX was 0 on entry the following information is also returned:
          EDX - linear address of module's stack
          ECX - linear address of start of module list
         C - error

     þ Int 21h, AX=4B83h: Get next PE module handle.
       Input:
         EDX - current module handle or 0 for the first module.
       Output:
         EAX - next module handle
         ECX - module count
         EDX - DPMI memory handle for this module
         C - error

     þ Int 21h, AX=4B84h (CallProc32W): Call 32-bit flat procedure from a
       16-bit dll.
       Input: 
         EDX - holds the flat address of the proc to call

     þ Int 21h, AX=4B85h (GetProcAddress16): Get the address of a procedure
       in a 16-bit module.
       Input: 
         BX - holds the module handle
         CL - determines the type of the export and how EDX is interpreted.
              If CL=1, EDX is interpreted as a number. If CL=0, EDX is
              interpreted as offset to a name. 
         DS:EDX - points to name of procedure if CL=0.
       Output:  
         DX:AX - Address of procedure

     þ Int 21h, AX=4B86h (GetModuleFileName): Get a pointer to a 
       module's full path and file name.
       Input:
         EDX - holds module handle.
       Output:
         EAX - returns a linear address to the module's path.
               Works for 16bit NE dlls as well.
         C - error      

     þ Int 21h, AX=4B87h (CallProc16): call a 16-bit proc from a 32-bit
       module.
       Input:
         EDX - holds value for CS:IP to call
          CX - holds number of WORD parameters to copy to the 16-bit
               stack
         EBX - linear address of pointer to the stack parameters.

     þ Int 21h, AX=4B88h (GetModuleHandle16): Get the handle of a
       16-bit NE module.
       Input:
         CL - determines the type of the module reference. If CL=0,
              EDX is interpreted as an offset. If CL=1, EDX is
              interpreted as a selector.
         DS:(E)DX - must point to the name of the module if CL=0.
       Output:  
         AX - the module handle. AX=0 indicates a failure.
         DX - holds the module handle of kernel

     þ Int 21h, AX=4B91h: enable/disable loader. This feature may be
       useful for DPMI applications, which want to start a true Win32
       console application and so first have to prevent the loader from
       trying to load it as DPMI client.
       Input:
         BL - contains new state (1=enable, 0=disable).

     þ Int 21h, AX=4B92h: Set the start of the PE module list, which
       is read with int 21h, ax=4b83h.
       Input: 
         EDX - the linear address of new start address.
       Output:
         EAX - the linear address of the previous start address 

       Calling this service with edx=0 makes DPMILD32 load fresh copies
       of already loaded dlls at next program load.

     þ Int 21h, AX=4B93h (SetErrorMode): Set error mode flag
       SEM_NOOPENFILEERRORBOX. During the initial load process
       this flag is cleared, causing the loader to display error messages
       if it encounts any problems. Just before the application is started
       the loader will set this flag, thus suppressing any further messages.
       With environment variable DPMILDR=64 this behaviour may be modified.
       Input:
         EDX - new flags.

     þ Int 21h, AX=4B94h: Set new value of variable DPMILDR.
       Input:
         CX - mask for the bits to change
         DX - new values for these bits
       Output:  
         AX - returns old value of the bits.

     þ Int 21h, AX=4B95h: Set value of "system directory" path
       Input:
         EDX - linear address system directory path (or NULL)

     Support of DOS4G consists of

     þ Int 21h, AX=FF00h:
       Input:
         DX = 0078h
       Output:
         ES = PSP
         EAX = 4734FFFFh

     This API is available in protected mode only.


 8.  PX executables

     If a PE executable uses non-Win32 compatible features (like software
     interrupts 0x21/0x31 or in/out instructions), it should be ensured
     that is is NOT loaded as Win32 app. For this the loader supports
     "PX" files, which contain 'PX' as magic bytes instead of 'PE'.
     To convert a PE binary to PX, just use tool PATCHPE.EXE after the link
     step. A small catch is that modules modified this way won't be
     recognized by PE tools anymore.


 9.  Support for NE binaries

     The loader has built-in support for NE binaries. Usually this support
     isn't needed at all and can be ignored. But on some very rare occasions
     it may be advantageous to implement a dll in NE format. It doesn't 
     need to be written in 16bit code, the NE format supports 32bit code
     as well, although segment size is limited to 64 kB.
       Besides dlls the loader will also accept 32bit NE applications.
     This is a very special HX format and not recommended, because the
     NE format doesn't allow an application to run in a true flat memory
     model. But model tiny will work and is not too bad for small apps.
     On program entry the following registers are set:

     -  CS = code segment
     -  DS, SS = DGROUP (usually has the same base as CS)
     -  ES = PSP selector
     -  GS = true flat descriptor
     -  EBX = size of stack in bytes
     -  ECX = size of heap in bytes

     The application's type must be set to 6 (by tool patchNE), which will
     be unknown to NE file dumpers. 


10.  Debugging Support

     DPMILD32 supports Int 41h in protected mode. That is, events such as
     loading a dll, starting a task, loading a segment a.s.o are all
     reported through calls to Int 41h with AX set appropriately. To force
     a breakpoint at app start set environment variable "DPMILDR=1".


11.  Returncodes

     Usually DPMILD32 returns the returncode of the (last) program it
     has executed. But there are several internal error conditions, which
     are reported to the caller through the following return codes:

     rc   comment                  possible reasons
     -----------------------------------------------------------------
     FB   loader init error        cannot switch CPU in protected mode
          real mode                memory shrink error (in real mode)
                                   no conventional memory available
     FC   loader init error        no filename supplied
          protected mode           file not found
                                   no extended memory available
                                   no conventional memory available
                                   DOS API translation not available                                   no selectors available
     FD   error in exception 0Bh   no more memory
          (NE files only)          error in NE exe file
     FE   application init error   imports couldn't be resolved
                                   dll init returns with ax/eax=0
     FF   fatalexit                application has called FatalExit or
          (NE files only)          FatalAppExit

     DPMILD32 always displays an error text to STDERR in these cases.


12.  Error Messages

     "relocs stripped, cannot load": relocation information is stripped
                      from PE binary. It can only be loaded at prefered
                      load address, which may be used already or DPMI
                      host doesn't support function 0x504.
     "out of memory": allocating memory for PE binary failed. Please note
                      that DPMILD32 cannot commit stack memory dynamically
                      by setting a GUARD page, it has to be fully allocated
                      at load time.
     "cannot create psp": most likely there is no more conventional DOS
                      memory available.
     "invalid PE format": there is a severe error in the PE binary. Try
                      to relink it.
     "cannot resolve imports": not all imports could be resolved. DPMILD32
                      will display the missing imports in detail.
     "dll init failed": dll entry code was called and returned with EAX != 1


13.  Restrictions

     The Loader loads the PE header in the first page of a module, but it
     doesn't map the header as it is found in the image file. In fact, only
     the IMAGE_NT_HEADERS structure and the object table are loaded, the 
     rest is ignored. Usually this is no problem at all, but there exist
     at least one linker which places strings in the header. Such strings
     can be determined with a PE file dumper - the RVA of the string is
     < 1000h. If these strings have to be used by the loader (for example,
     if it is a name of an imported dll), the load process will fail!

     Tool PEStub may be used to test if such restrictions are met by
     a binary. Use "PEStub -r filename" and watch for warning messages.


14.  History

 16.11.2009: version 3.7

 þ bugfix: int 21h, ax=4B81h (GetProcAddress32) didn't check if RVA of
   export directory is NULL.
 þ WLink is used as linker.

 20.01.2009: version 3.6

 þ assembler switched to JWasm.
 þ int 21h, ax=4B82h (GetModuleHandle) now checks the full path if
   a full path is given.

 01.03.2008: version 3.5

 þ bugfix: the stub version (HDLD32.BIN) did release too much DOS
   memory, resulting in corruption of the DPMI host's memory image.
 þ bugfix: the bottom stack page was not always discarded (when running
   on a DPMI v1.0 host).
 þ the reserved stack space of PE binaries is still increased by 64 kB,
   but this is now uncommitted space (on a DPMI v1.0 host).
 þ for PE applications, it's ensured that ESI points to module base on
   entry (makes DPMILD32 compatible with HX's LOADPE.BIN stub).
 þ int 21h, ax=4B82h, edx=0 API returns more info.

 11.01.2008: version 3.4

 þ environment variable switch DPMILDR=512 isn't used anymore.
 þ if DPMILDR=128 is set and an "unresolved import" is called, there
   will be a message displayed before exiting.
 þ there is now another MZ stub supported (HDLD32.BIN), which includes HDPMI.

 15.07.2007: version 3.3.0

 þ FS is no longer used/modified by DPMILD32. 
 þ DPMILD32 does no longer allocate and initialize a TIB for DKRNL32. 
   This is now handled entirely by DKRNL32.

 15.03.2007: version 3.2.0

 þ bugfix: slashs ('/') in a path weren't handled like backslashs.
 þ loader initialization simplified.
 þ DPMILD32 now available as DOS MZ stub (DPMILD32.BIN).
 þ export GlobalDOSFree added.
 þ hack removed which made DPMILD32 set a field in the MZ header used
   by DKRNL32 (to end the application load phase). Now this is done
   by a Int 41h callout.
 þ int 21h, ax=4B95h added to support a "system directory", which some
   applications rely upon.

 14.12.2006: version 3.1.8

 þ bugfix: there was a chance that the loader allocated too large an
   environment (or even caused a GPF) when a new program was launched
   due to a bug in the routine which get the length of the program name.
 þ bugfix: exports _AHINCR and _AHSHIFT had wrong ordinals (should be
   a minor issue for DPMILD32 since these exports are used by 16-bit
   binaries only).
 þ NE dlls reference counter wasn't always updated correctly under some
   circumstances.

 15.10.2006: version 3.1.7

 þ bugfix: calling WEP of a 16-bit NE dll didn't set DS to DGROUP.

 14.09.2006: version 3.1.6

 þ GetMuduleFileName may have caused a GPF if an invalid hModule parameter
   was given. 16-bit dlls only.
 þ bugfix: GlobalFree modified ES. This should only happen if ES contains
   the selector of the block which was released (then ES should be set to 0).
   16-bit dlls only.
 þ in GlobalRealloc interrupts were disabled by "pushf cli" and restored
   by testing the pushed flags. Now DPMI functions 0900h and 0901h are used.
   16-bit dlls only.

 15.07.2006: version 3.1.5

 þ switch DPMILDR=8 no longer tries to "hide" the DPMI host. This was a
   hack which caused a HX or Win32 program launched by the current app
   to load a new instance of HDPMI, thus running in a separate address
   space. Since HDPMI 3.07 there is support for multiple address contexts
   natively, so hiding the host is no longer required (which had some
   disadvantages and most likely worked with HDPMI only). However, 
   setting DPMILDR=8 is still usefull when running Win32 applications,
   since it prevents the loader from trying to load the app into the current
   client.
 þ if DPMILDR=8 is set, the loader will no longer create a child PSP
   for the application to launch (since there will be just one application).
 þ int 2F, ax=168Eh (to set the console title in win9x) is now only called
   if system *is* win9x.

 14.06.2006: version 3.1.4

 þ bugfix: loader has lost values of ECX and EBX for 32-bit NE application
   entry points.

 15.05.2006: version 3.1.3

 þ command line option -g to load a console application as GUI app.

 02.05.2006: version 3.1.2

 þ bugfix: loading a dll standalone (without an application) didn't work
   in previous version.
 þ bugfix: if a dll launched a PE app (in dll initialization), it
   never returned.

 30.03.2006: version 3.1.1

 þ EBX saved/restored when trying to open a file. Some DOSes trash
   HIWORD(EBX) on this call.
 þ additional security check that FS is valid when unloading dlls.

 27.02.2006: version 3.1

 þ bugfix: lpvReserved parameter when calling DllMain was always 0.
   Now it is 0 only if dlls are loaded dynamically.
 þ test for invalid relocations and skip them (SDL_net.dll)
 þ 200h bytes at stack top no longer reserved and no longer needed.
   TLS array and context save area are handled entirely by DKRNL32.

 05.02.2006: version 3.0.9

 þ 200h bytes at stack top reserved for DKRNL32 thread context saving.
 þ Int 21h, AX=4B81h (GetProcAddress) may have caused a GPF if
   module handle was invalid.
 þ error "invalid module handle" no longer displayed if flag
   SEM_NOOPENFILEBOX is set.

 20.12.2005: version 3.0.8

 þ don't execute an application if it is loaded as dll.

 06.12.2005: version 3.0.7

 þ DPMILD32 displays to stderr now (because stdout output may be
   lost after HXGUIHLP has been loaded)
 þ HXGUIHLP.DLL now loaded *before* other dll initialization code
   is called (required for OPENGL32.DLL).
 þ bugfix: cross references in PE dlls caused a GPF
 þ bugfix LFN version: there was one place with still 65 byte
   size limit for filenames.

 24.11.2005: version 3.0.6

 þ implemented a version of DPMILD32 with LFN support enabled
 þ bugfix: bounds check didn't work when importing a function by number

 18.11.2005: version 3.0.5

 þ loader now will try loading GUI apps on true DOS without
   having to set DPMILDR=8192. 

 01.11.2005: version 3.0.4

 þ bugfix: int 21h, ax=4b80h (free module) returned 0 on success

 21.10.2005: version 3.0.3

 þ new DPMILDR setting (8192) to allow loading GUI apps.

 28.09.2005: version 3.0.2

 þ module name translation GDI32.DLL -> DGDI32.DLL added
 
 19.09.2005: version 3.0.1

 þ bugfix: memory for image wasn't freed if stack couldn't be allocated.
 þ DPMILDR switch 4096 added to restrict stack size to 128 kB.

 05.09.2005: version 3.0.0

 þ bugfix: launching a real-mode app may have failed just because
   MZ-Hdr contained a "big" value at offset 3Ch.

 28.08.2005: version 2.9.9

 þ error code 000Bh returned if a PE load error occured.
   Previously it was "undefined".

 14.08.2005: version 2.9.8

 þ bugfix: support for going resident with int 21h, ah=31h lost
   returncode in AL.
 þ DPMILDR switch 2048 added to protect address range 0-3FFh.
 þ bugfix: 32bit NE app didn't work in previous release if app wasn't
   the first one. 

 06.08.2005: version 2.9.7

 þ bugfix: program name in environment was ok for first task only.
 þ bugfix: first page of stack was uncommitted, but FS:[8]
   (stack bottom) was not adjusted accordingly.
 þ DOS4G "support" added. This is for PE binaries only, the loader
   doesn't know how to load LE/LX binaries. But it will allow
   to use Open Watcom's CRT modules for DOS extenders to create
   HX PE binaries.

 01.08.2005: version 2.9.6

 þ field FileHeader.Machine now checked for i386. This will
   prevent the loader from trying to load some old MS binaries
   which must use their own loader (MS32KRNL).
 þ bugfix: 32bit NE apps trying to load a PE dll caused a GPF.
 þ bugfix: there was always the last module name displayed on errors.
 þ new DPMILDR setting (1024) to load dlls at their prefered
   load address. This option is meant mainly for debugging
   purposes, usually dlls can be loaded anywhere in the user address space.

 20.07.2005: version 2.9.5

 þ bugfix: some messages weren't suppressed despite
   SEM_NOOPENFILEERRORBOX was active.
 þ bugfix: there was a problem with dynamically loaded dlls,
   which the app doesn't unload itself. DPMILD32 had problems
   to determine the correct unload order, which may have
   resulted in an access violation.

 15.07.2005: version 2.9.4

 þ first page of stack is now uncommitted to avoid stack 
   overflows to overwrite other memory regions. Works only
   if DPMI host supports int 31h, ax=0507h (V1.0).

 13.07.2005: version 2.9.3

 þ new DPMILDR setting (512) to exclude DKRNL32 from module list reset.
 þ bugfix: setting DPMILDR=4 worked, but then if a 32bit NE
   app was started, this caused a loop.

 06.07.2005: version 2.9.2

 þ bugfix: the 32bit loader may have tried to load 16bit NE
   applications - with bad results. Now this is refused.
 þ bugfix: int 21h, ax=4b81h expected ES to be a flat selector
 þ bugfix: if an error occured while resolving imports of a
   starting app, the application exited with errorcode 0FFh.
   Should have been 0FEh instead. And the error message may
   have been suppressed.
 þ Int 21h, ax=4B81h (GetProcAddress32) now accepts a number
   instead of a string (HIWORD(edx) == 0). This feature was
   required to fully support delay loading.
 þ bugfix: loader always assumed OptionalHeader has maximum size
   and ignored field FileHeader.SizeOfOptionalHeader.

 27.06.2005: version 2.9.1

 þ bugfix: an internal function to set the console title
   assumed a wrong DS, thus corrupting DOS memory! It was just
   one bit set to 0, that's why there was a good chance that the
   bug had no consequence - and that's why it remained undeteced
   for quite some time :(.
 þ bugfix: changing the order of FreeDynLoadedModules
   /FreeReferencedModules calls in the last version was a bug!
 þ try to load DEBUGO32.DLL now only if switch in DPMILDR is set
 þ support for 16-bit exports Get-/WritePrivateProfileString deleted.
 þ search order for dlls:
   - directory of application binary. didn't work previously! 
   - current directory
   - directories of PATH

 23.06.2005: version 2.9

 þ exchanged calls FreeDynLoadedModules/FreeReferencedModules in FreeModule32
 þ D bit of stack selector for calling 16-bit procs is now set
   (again). As long as HIWORD(ebp) is cleared before a 16-bit
   proc is called, this should be no problem. On the other hand
   SS with D bit cleared is something that most software doesn't
   expect in a 32-bit host.
 þ bugfix: error mode set to 8000h as default before app start
   (this means SEM_NOOPENFILEERRORBOX)
 þ bugfix: export _AHINCR/_AHSHIFT when using DM linker
 þ bugfix: process termination didn't work if a dll caused
   an error in DLL_DETACH_PROCESS routine.

 14.06.2005: version 2.8.9

 þ workaround for DPMIONE implemented
 þ display correct error if memory reallocation failed

 22.05.2005: version 2.8.8

 þ bugfix: version 2.8.7 introduced a bug so a module was
   searched in PATH even if a directory was included in path!

 20.05.2005: version 2.8.7

 þ bugfix: loading a dll with a relative path didn't work
 þ bugfix: the loader assumed that word at PSP:[7Eh] was
   zero-initialized. For OpenDOS (DR-DOS) this is not true and is
   the reason why the loader may have caused a crash by launching 
   a real-mode app. 
 þ 64kB are added to the reserved stack as it is done in win9x
   systems. Wlink by default defines a 64kB reserved stack region
   only, and, on the other hand, the OW stack checking code
   requires a stack of at least 76 kB on win9x systems!
 þ stack bottom now set in THREAD_INFORMATION_BLOCK.
   Used by VirtualQuery of DKRNL32.DLL (OW stack check)
             
 09.01.2005: version 2.8.7 preliminary

 þ stack for PE applications is now allocated as a separate
   memory block with unspecified address. Thus it will run
   much better on DOSEMU.

 03.12.2004: version 2.8.6

 þ loader moving in extended memory now supported for dosemu.
   termination code simplified.
 þ switched to Digital Mars C++ linker to link DPMILDxx.EXE
 þ bugfix: on int 21h, ah=4Ch don't modify AL

 31.10.2004: version 2.8.5

 þ error messages modified:
   "memory allocation error #2" -> "out of memory"
   "init failed" -> "dll init failed"

 08.10.2004: version 2.8.4

 þ always ignore relocation directory entry if relocations are
   stripped (ldw.exe)

 06.10.2004: version 2.8.3

 þ bugfix: GetModuleHandle32 didn't find modules if extension
   ".dll" wasn't specified

 11.09.2004: version 2.8.2

 þ bugfix: don't launch HDPMIxx with command line of DPMILDxx
 þ loader automatically increases file handles if file open
   fails with error 4

 21.08.2004: version 2.8.1

 þ new API int 21h, AX=4B94 (set DPMILDR value)
 þ ESI now holds module handle when a PE module starts
 þ when receiving an int 41h, AX=F003 (set break), CX:EBX
   may be modified, so it is no longer necessary to set a break

 21.08.2004: version 2.8

 þ DPMILDR=128 switch added (ignore unresolved import errors).
 þ bugfix: use current PSP to copy environment selector from
   when creating a child PSP. This is for FreeDOS mainly.

 27.07.2004: version 2.7.9

 þ DPMILD32, int 21h, ax=4B00h now compatible with DOSEMU 
 þ Load dlls at their base address if relocs are stripped

 14.06.2004: version 2.7.8

 þ bugfix: setting DTA (12.05.2004) destroyed HIWORD(ebx) in 
   DPMILD32 (EBX is pointer to EXEC parameter block)

 09.06.2004: version 2.7.7 (released in DEBXXF)

 þ bugfix: dpmi error display may have caused an exception
 þ disable 16bit flag now only valid for apps (and DPMILD32)
 þ SetErrorMode(0) called for PE apps just before app starts
 þ free 16-bit stack mem only if 16-bit stack selector is valid
 þ set NE flag 4000h if libentry has been called for dlls
 þ Loader now always sets parent in PSP as selector, since
   this is required not only by NT platforms, but by win31 as well

 26.05.2004: version 2.7.6

 þ DPMILD32: NE LibEntry now called with 16-bit stack
 þ vector int 31h now saved at startup and used in dpmicall.
   this helps for terminating code when client has left interrupts
   in a bad state
 þ bugfix: DPMILD32: before calling LoadlibIntern clear HIWORD(esi)
 þ DPMILD32: NE Wep now called with 16-bit stack
 þ dta saved and restored for each task
 þ bugfix: WritePrivateProfileString works now!?
 þ bugfix: user loader psp selector as parent for NT/2K/XP again
   (bugfix from 03.03.2004)
 þ DPMILD16.EXE and DPMILD32.EXE now patched as DPMI executable
 þ functions ax=4b91h and ax=4b93h for 16 bit loader as well.
   4b91h will totally disable/enable loader now
 þ use switch DPMILDR=8 for NE files as well (TLINK.EXE!)

 28.04.2004: version 2.7.5

 þ if pointer to raw data is zero, dont try to load from file
 þ use raw data size to determine if anything to load from
   the file (previous just checked uninitialized data flag)
 þ win16api.asm cleaned, OutputDebugString now for 16bit only
 þ bugfix: dont check for 0 as dpmi memory handle. this may be valid
 þ dont free psp with int 31h, ax=102h if dos kill function worked

 22.04.2004: version 2.7.4

 þ no changes in DPMILDXX, but in DKRNL32

 20.04.2004: version 2.7.3

 þ freeing 32-bit segment notifications added
 þ DPMILDR=64 switch added (ignore SEM_NOOPENFILEERRORBOX).
   Also added new API ax=4B93h (SetErrorMode)

 10.04.2004: version 2.7.2

 þ release memory of discardable sections
 þ to clear a section use phys size if virt size is smaller
 þ function int 21h, ax=4b83h now returns dpmi handle in edx

 30.03.2004: version 2.7.1

 þ no changes in DPMILDXX, but in DKRNL32

 14.03.2004: version 2.7.0

 þ no more special loader version for DOSEMU needed
 þ notification int 41h, ax=164h (loading 32bit dll)
 þ set parent PSP as segment, not selector
 þ loader now DOSEMU compatible (special version)

 02.02.2004: version 2.6.6

 þ in FreeModule32 check value of popped fs first (may be invalid)
 þ copy env ptr to child psp if it is NULL (FreeDOS)

 24.01.2004: version 2.6.5

 þ another bugfix (the last?) in command line preparation 
 þ call SetCmdLine for PE apps as well

 19.01.2004: version 2.6.4

 þ no changes in DPMILDXX, but in DKRNL32

 01.01.2004: version 2.6.3

 þ write-protect read/only sections (optionally, see DPMILDR=16)
 þ heap no longer allocated. is done by dkrnl32 now

 20.12.2003: version 2.6.2

 þ 32bit segment load notifications added (int 41h, AX=150)
 þ bug fixed in command line parser if DPMILDR was executed
   directly (not as overlay from stub)            
 þ loading continues after first import hasnt been found
   so all missing imports will be reported.
 þ some changes for CallProc16 (switch to 16-bit stack)
 þ Dlls now called with stack and PSP of application
   TIB now located behind MZ (each 40h bytes in size)
 þ FS points to a full TIB now, TLS slots now located on stack

 11.12.2003: version 2.5.3

 þ import resolves now works with borland PEs (missing ILT)
 þ dont try to load PE GUI apps

 07.12.2003: version 2.5.2

 þ new switch DPMILDR=8 (disable loader and server)

 30.11.2003: version 2.5.1

  Versions < 2.5.1:

  The loader was created mainly in 1993 to execute protected mode
  NE executables as 16-bit DPMI clients. This version was able to
  run on 80286 processors as well. Some time later a version for
  32-bit DPMI clients was added, still supporting NE executables
  only and thus unable to provide a true flat memory model. This
  changed in 1995, when the 32-bit version was extended to support
  PE file format. Another major extension was the win32 emulation dll
  DKRNL32.DLL, which allowed to create dual-mode (or bimodal) 
  applications. This happened mainly in 1995 and 1996.

  In 2003 some support for DPMI V1.0 features were added to the DPMI
  server HDPMI. The most remarkable extension was support for function
  0x0504, which allows a client to allocate memory at a specified address.
  This feature allowed the PE loader to load and execute (console) 
  programs even if relocation infos are missing.


15.  Copyright

  DPMILD32.EXE is part of HX DOS extender. This extender is freeware. 
  View HXRT.TXT for license details.

  Japheth (http://www.japheth.de)

