Changeset 699 for trunk/src/kernel32/mmap.cpp

Timestamp:

Aug 25, 1999, 7:05:57 PM (26 years ago)

Author:

sandervl

Message:

Memory mapped file (writes) changes

File:

• trunk/src/kernel32/mmap.cpp (modified) (5 diffs)

trunk/src/kernel32/mmap.cpp

@@ -1 @@
-/* $Id: mmap.cpp,v 1.12 1999-08-25 15:27:19 sandervl Exp $ */
+/* $Id: mmap.cpp,v 1.13 1999-08-25 17:05:57 sandervl Exp $ */
 
 /*
@@ -10 +10 @@
  *       dispatched to our exception handler until after the kernel mode
  *       call returns (too late))
- *
- * NOTE: There's no easy way to determine which pages were modified. Temporary
- *       solution is to write all paged-in memory to disk.
  *
  * NOTE: Are apps allowed to change the protection flags of memory mapped pages?
@@ -140 +137 @@
 }
 //******************************************************************************
-//******************************************************************************
-BOOL Win32MemMap::commitPage(LPVOID lpPageFaultAddr, ULONG nrpages)
-{
+//We determine whether a page has been modified by checking it's protection flags
+//If the write flag is set, this means commitPage had to enable this due to a pagefault
+//(all pages are readonly until the app tries to write to it)
+//******************************************************************************
+BOOL Win32MemMap::commitPage(LPVOID lpPageFaultAddr, ULONG nrpages, BOOL fWriteAccess)
+{
+ MEMORY_BASIC_INFORMATION memInfo;
  DWORD pageAddr = (DWORD)lpPageFaultAddr & ~0xFFF;
  DWORD oldProt, newProt, nrBytesRead, offset, size;
@@ -151 +152 @@
   dprintf(("Win32MemMap::commitPage %x (faultaddr %x), nr of pages %d", pageAddr, lpPageFaultAddr, nrpages));
   if(hMemFile != -1) {
-        if(VirtualAlloc((LPVOID)pageAddr, nrpages*PAGE_SIZE, MEM_COMMIT, PAGE_READWRITE) == FALSE) {
-                goto fail;
-        }
-        offset = pageAddr - (ULONG)pMapping;
-        size   = nrpages*PAGE_SIZE;
-        if(offset + size > mSize) {
-                size = mSize - offset;
-        }
-        if(SetFilePointer(hMemFile, offset, NULL, FILE_BEGIN) != offset) {
-                dprintf(("Win32MemMap::commitPage: SetFilePointer failed to set pos to %x", offset));
-                goto fail;
-        }
-        if(ReadFile(hMemFile, (LPSTR)pageAddr, size, &nrBytesRead, NULL) == FALSE) {
-                dprintf(("Win32MemMap::commitPage: ReadFile failed for %x", pageAddr));
-                goto fail;
-        }
-        if(nrBytesRead != size) {
-                dprintf(("Win32MemMap::commitPage: ReadFile didn't read all bytes for %x", pageAddr));
-                goto fail;
-        }
-        if(mProtFlags & PAGE_READONLY) {
+        if(VirtualQuery((LPSTR)pageAddr, &memInfo, nrpages*PAGE_SIZE) == 0) {
+                dprintf(("Win32MemMap::commitPage: VirtualQuery (%x,%x) failed for %x", pageAddr, nrpages*PAGE_SIZE));
+                goto fail;
+        }
+        if(memInfo.State & MEM_COMMIT)
+        {//if it's already committed, then the app tried to write to it
+                if(!fWriteAccess) {
+                        dprintf(("Win32MemMap::commitPage: Huh? Already committed and not trying to write (%x,%x) failed for %x", pageAddr, nrpages*PAGE_SIZE));
+                        goto fail;
+                }
+                if(VirtualProtect((LPVOID)pageAddr, nrpages*PAGE_SIZE, newProt, &oldProt) == FALSE) {
+                        dprintf(("Win32MemMap::commitPage: Failed to set write flag on page (%x,%x) failed for %x", pageAddr, nrpages*PAGE_SIZE));
+                        goto fail;
+                }
+        }
+        else {
+                if(VirtualAlloc((LPVOID)pageAddr, nrpages*PAGE_SIZE, MEM_COMMIT, PAGE_READWRITE) == FALSE) {
+                        goto fail;
+                }
+                offset = pageAddr - (ULONG)pMapping;
+                size   = nrpages*PAGE_SIZE;
+                if(offset + size > mSize) {
+                        size = mSize - offset;
+                }
+                if(SetFilePointer(hMemFile, offset, NULL, FILE_BEGIN) != offset) {
+                        dprintf(("Win32MemMap::commitPage: SetFilePointer failed to set pos to %x", offset));
+                        goto fail;
+                }
+                if(ReadFile(hMemFile, (LPSTR)pageAddr, size, &nrBytesRead, NULL) == FALSE) {
+                        dprintf(("Win32MemMap::commitPage: ReadFile failed for %x", pageAddr));
+                        goto fail;
+                }
+                if(nrBytesRead != size) {
+                        dprintf(("Win32MemMap::commitPage: ReadFile didn't read all bytes for %x", pageAddr));
+                        goto fail;
+                }
+                if(mProtFlags & PAGE_READONLY) {
 //DosSetMem returns flags with EXECUTE bit set, even though the initial allocation is without this bit set!
 //Also returns access denied when trying to set it back to READONLY
-                VirtualProtect((LPVOID)pageAddr, nrpages*PAGE_SIZE, newProt, &oldProt);
-//              if(VirtualProtect((LPVOID)pageAddr, nrpages*PAGE_SIZE, newProt, &oldProt) == FALSE) {
-//                      goto fail;
-//              }
+                        VirtualProtect((LPVOID)pageAddr, nrpages*PAGE_SIZE, newProt, &oldProt);
+//                      if(VirtualProtect((LPVOID)pageAddr, nrpages*PAGE_SIZE, newProt, &oldProt) == FALSE) {
+//                              goto fail;
+//                      }
+                }
         }
   }
@@ -256 +274 @@
 }
 //******************************************************************************
-// NOTE: There's no easy way to determine which pages were modified. Temporary
-//       solution is to write all paged-in memory to disk.
+//We determine whether a page has been modified by checking it's protection flags
+//If the write flag is set, this means commitPage had to enable this due to a pagefault
+//(all pages are readonly until the app tries to modify it)
+//
 //TODO: Are apps allowed to change the protection flags of memory mapped pages?
 //      I'm assuming they aren't for now.