--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/os/dos/cwsdpmi.txt Wed Nov 26 13:12:45 2008 +0000
@@ -0,0 +1,173 @@
+CWSDPMI is Copyright (C) 1995-2000 Charles W Sandmann (sandmann@clio.rice.edu)
+ 1206 Braelinn, Sugar Land, TX 77479
+
+This is release 5. The files in this binary distribution may be redistributed
+under the GPL (with source) or without the source code provided:
+
+* CWSDPMI.EXE or CWSDPR0.EXE are not modified in any way except via CWSPARAM.
+
+* CWSDSTUB.EXE internal contents are not modified in any way except via
+ CWSPARAM or STUBEDIT. It may have a COFF image plus data appended to it.
+
+* Notice to users that they have the right to receive the source code and/or
+ binary updates for CWSDPMI. Distributors should indicate a site for the
+ source in their documentation.
+
+-------------------------------------------------------------------------------
+
+CWSDPMI was written to provide DPMI services for V2 of DJGPP. It currently
+does not support 16-bit DPMI applications, or DPMI applications requiring a
+built in extender. It does support virtual memory and hardware interrupt
+reflection from real mode to protected mode. DJGPP V1.1x and RSX applications
+will also run using this server, which can be used to provide enhanced control
+over hardware interrupts. Some DPMI 1.0 extensions (0x506, 0x507, 0x508) have
+been implemented.
+
+CWSDPR0.EXE is an alternate version which runs at ring 0 with virtual memory
+disabled. It may be used if access to ring-0 features are desired. It
+currently does not switch stacks on HW interrupts, so some DJGPP features
+such as SIGINT and SIGFPE are not supported and will generate a double fault
+or stack fault error (to be fixed someday).
+
+CWSDSTUB.EXE is a stub loader image for DJGPP which includes CWSDPMI. This
+allows single executable image distributions. You can use the EXE2COFF
+program and COPY /B CWSDSTUB.EXE+yourimage yourimage.exe to create a
+standalone executable image.
+
+Some of the internal tuning and configuration parameters may be modified
+in the image using CWSPARAM.EXE (see CWSPARAM.DOC).
+
+If you want to use CWSDPMI with DJGPP, you expand the distribution into the
+DJGPP directory tree. CWSDPMI.EXE will be put in the BIN directory with your
+DJGPP images and it will automatically be loaded when they run.
+
+Directions for use (server can be used in either of two different ways):
+
+1) "cwsdpmi" alone with no parameters will terminate and stay resident
+ FOR A SINGLE DPMI PROCESS. This means it unloads itself when your
+ DPMI application exits. This mode is useful in software which needs
+ DPMI services, since CWSDPMI can be exec'ed and then will unload on exit.
+
+2) "cwsdpmi -p" will terminate and stay resident until you remove it.
+ It can be loaded into UMBs with LH. "cwsdpmi -u" will unload the TSR.
+
+3) The file used for virtual memory swapping, if desired, is controlled
+ by the "-sc:\cwsdpmi.swp" syntax on the command line. You must specify
+ either a file with full disk/directory syntax, or "-s-" which disables
+ virtual memory.
+
+4) The default swap file name is c:\cwsdpmi.swp, but this can be changed
+ with the CWSPARAM image, as can some other parameters.
+
+5) You can disable the DPMI 1.0 extensions by starting the image with the
+ "cwsdpmi -x" syntax. This feature allows you to run programs developed
+ under other DPMI providers which do not behave properly with these
+ extensions enabled (typically use of NULL pointers).
+
+I would like to give special thanks to DJ Delorie who wrote the original
+GO32 code on which CWSDPMI is based. Morten Welinder also provided and
+improved much of the code in this program.
+
+-------------------------------------------------------------------------------
+
+This section contains a list of the error messages you might see out of
+CWSDPMI and some details on what they mean.
+
+Exceptions are only handled by CWSDPMI if the application does not establish
+an exception handler, exceptions nest 5 deep, or the error is particularly bad:
+
+"Page fault" -
+ 1) an illegal page fault happens in a RMCB or HW interrupt, (lock all pages!)
+ 2) all available pages have been locked,
+ 3) the application is using non-committed pages for null pointer protection.
+"Double Fault" - multiple exceptions occurred
+"Invalid TSS" - typically due to RMCB or HW interrupt being called after the
+ selectors/memory have been deallocated (remember to reset the mouse)
+"General Protection Fault" - bad parameter sent to a DPMI call
+
+"80386 required."
+
+Since 80286 and lesser processors don't have the hardware necessary to
+run CWSDPMI. No workaround, upgrade.
+
+"DOS 3 required."
+
+A few interrupts are used which need DOS 3.0 or higher. I don't expect to
+ever see this message, since 80386 machines were introduced after DOS 3.0
+and that check is made first.
+
+"CWSDPMI V0.90+ (r5) Copyright (C) 2000 CW Sandmann ABSOLUTELY NO WARRANTY"
+
+An informational message displayed if the program is not run in one-pass mode.
+
+"Protected mode not accessible."
+
+This message should only be displayed if running CWSDPMI in a protected
+environment with no access to protected mode. In this case, DPMI should
+already be available and CWSDPMI would not be needed. This might happen if
+a 16-bit DPMI client is loaded and a DJGPP image attempts to load CWSDPMI
+to provide 32-bit DPMI services under Windows.
+
+"Warning: cannot open swap file c:\cwsdpmi.swp"
+
+Maybe you are out of file handles, or the swap file name is incorrectly
+specified in the image (change the name with cwsparam).
+
+"No swap space!"
+
+This message means you tried to use more paging file than CWSDPMI was
+configured to handle. Since this is protected against in the memory
+allocation code, you should never see this message.
+
+"Swap disk full!"
+
+This means the paging file could not be expanded when trying to page
+memory out to disk. This would normally not be seen, unless you are
+writing output to the same disk which holds the paging file. Decrease
+the amount of memory your DPMI application is using or free up disk space.
+
+"Interrupt 0x??"
+
+Your application tried to call an interrupt from protected mode which
+normally shouldn't be called (something like a data pointer). If the
+request was allowed to continue it would likely hang your machine. If you
+see this message and think the interrupt should be allowed to continue, let
+me know.
+
+"Error: Using XMS switched CPU into V86 mode."
+
+This message might be seen if you have your memory manager in AUTO mode. The
+only workaround in this case is to stop using AUTO mode.
+
+"Error: could not allocate page table memory"
+
+The page table memory (a minimum of 16Kb) is allocated from conventional
+memory (either in the 640Kb region or UMBs). If CWSDPMI cannot allocate the
+minimum necessary memory, you would see this message. Free up some
+conventional memory. You may also see this message if a page directory needs
+to be faulted in, and there are no available pages. This means too many pages
+have been locked for the allocated page tables available. While CWSDPMI
+tries to dynamically allocate these if needed, this effort failed. You need
+to increase the number of page tables with CWSPARAM, or increase the amount
+of free conventional memory if it is low. If the application which calls
+CWSDPMI internally manages all the DOS memory, the page tables may need to
+be pre-allocated at DPMI startup time (if this is needed, try using the
+run option flag 2 in cwsparam).
+
+"16-bit DPMI unsupported."
+
+CWSDPMI is a 32-bit only DPMI server. Ideally, on the request to enter DPMI's
+PM with a 16-bit request, we would just fail the call setting the carry bit
+like the DPMI specification describes. Some buggy 16-bit compiler tools don't
+check the return status and will hang the machine in this case. So, I issue
+an error message and exit the image instead.
+
+"Descriptors exhausted."
+
+An attempt to nest a DPMI client failed in the setup phase due to insufficient
+free selectors in the LDT.
+
+"CWSDPMI not removed"
+
+When the -u parameter is specified, if DPMI is not detected this message is
+printed. Informational.