Changeset 8913 for trunk/src/kernel32/windllpeldr.cpp

Timestamp:

Jul 23, 2002, 3:51:49 PM (23 years ago)

Author:

sandervl

Message:

Enhanced PE loader class to support files with PE image starting at an offset ..= 0 (custom build) & Fixes for memory map view with offset

File:

• trunk/src/kernel32/windllpeldr.cpp (modified) (3 diffs)

trunk/src/kernel32/windllpeldr.cpp

@@ -1 @@
-/* $Id: windllpeldr.cpp,v 1.10 2002-07-18 11:52:56 achimha Exp $ */
+/* $Id: windllpeldr.cpp,v 1.11 2002-07-23 13:51:48 sandervl Exp $ */
 
 /*
@@ -34 +34 @@
 #include "dbglocal.h"
 
-//******************************************************************************
-// Design information on PE DLL memory layout - AH 2002-07-18
-//
-// We are currently using (high) private memory for all PE objects, including the
-// read/execute code segments, constant data segments and global data segments.
-// Global data segments might not be implemented correctly at all as we've never
-// encountered any applictions making use of them. Therefore we are actually
-// wasting memory when running multiple processes using the same PE DLLs.
-//
-// There are several reasons for this design decisions. Both OS/2 (LX) and
-// Windows NT put all DLL segments into the shared arena. What they do for
-// instance data is map it for each process to read-only pages initially. When
-// a write attempt is made by a process, an exception will be triggered. This
-// makes the operating system to copy the data to a new page that is read/write
-// and change the page table of the process to map the linear process in the
-// shared arena to private memory (this is called "copy-on-write").
-// Even though an application is not guaranteed any virtual address for instance
-// data segments, they always end up in the shared region and the virtual addreses
-// are contiguous. An application could therefore make nasty assumptions.
-// Unfortunately, it is not possible for us from ring 3 to replicate the behavior
-// for our PE loader. While we can make the page read only and catch the
-// exception, we have no method to remap the pages to private memory.
-//
-// One solution would be to create another reagion with the private region,
-// i.e. define some address space range as reserved in Odin (configurable to
-// workaround issues with certain PE images requiring those addresses). We
-// could then load the instance data segments of PE DLLs into this private
-// memory arena and still guarantee identical virtual addresses for each
-// process.
-//
-// While the above method should work fine (assuming an application does not
-// make any nasty assumptions), there is one major problem. If we enable the
-// PE on-demand loader (i.e. the mmap loads each page from the PE file when
-// it is accesses for the first time - very much like NT), then we would have
-// nasty concurrency issues. A process could access a page for the first time
-// and the exception is triggered. We commit the page read the data in using
-// a call to DosRead. If the very same page is accessed from a different
-// process after we have committed it but before we have finished the DosRead,
-// we would run into problems. Unfortunately, there does not seem to be any
-// solution for this.
-//
-// The bottomline is that we put everything into private memory and accept the
-// drawback of wasting memory.
-//******************************************************************************
-
 
 //******************************************************************************
@@ -98 +53 @@
 //******************************************************************************
 //******************************************************************************
-BOOL Win32PeLdrDll::init(ULONG reservedMem)
+BOOL Win32PeLdrDll::init(ULONG reservedMem, ULONG ulPEOffset)
 {
  char   modname[CCHMAXPATH];