Create a new page directory for each new task (except the GUI shell, which shares the kernel's page directory).

In KPageAllocator(), check if we're mapping a new page into kernel space, and if so, copy that mapping into all the other page directories of running tasks.

Author: tthomps

MyOS_1/Executables/PE32.c

@@ -5,7 +5,7 @@
 #include "../Terminal.h"
 #include "../printf.h"
 #include "../Tasks/Context.h"
-
+#include "../paging.h"
 
 jmp_buf peReturnBuf;
 
@@ -81,6 +81,26 @@ bool loadAndRunPE(uint8_t *executableDestination, DOS_Header *mzAddress, const c
         }
     }
 
+    // Disable interrupts
+    _disable();
+
+    // Get a new page directory for the new task
+    PAGE_DIRECTORY_ENTRY *newPageDirectory;
+
+    // GUI.exe shares the kernel's page directory
+    if ((uint32_t)executableDestination != 0xC00000)
+    {
+        newPageDirectory = (PAGE_DIRECTORY_ENTRY *)nextPageDirectory;
+        nextPageDirectory += sizeof(PAGE_DIRECTORY_ENTRY) * 1024;
+
+        // Copy the kernel's page table to this new page table
+        memcpy((void*)newPageDirectory, pageDir, sizeof(PAGE_DIRECTORY_ENTRY) * 1024);
+
+        //Paging_Print_Page_Table(newPageDirectory);
+    }
+    else
+        newPageDirectory = pageDir;
+
     // TEMPTEMP - zero out 5 0x1000 sections of memory (tailored to TestApp1.exe)
     memset(executableDestination, 0, 0x5000);
 
@@ -140,10 +160,13 @@ bool loadAndRunPE(uint8_t *executableDestination, DOS_Header *mzAddress, const c
     if (multiEnable)
     {
         // TEMP: use kernel page directory
-        DispatchNewTask((uint32_t)entryPoint, __readcr3(), 0x20000, imageName, exclusive);
+        DispatchNewTask((uint32_t)entryPoint, newPageDirectory, 0x20000, imageName, exclusive);
     }
     else
-    {        
+    {   
+        // Re-enable interrupts
+        _enable();
+
         /*_asm {
             // Setup the program's stack
             mov [espVal], esp

MyOS_1/Interrupts/Interrupts.c

@@ -558,7 +558,9 @@ void _declspec(naked) page_fault_handler(void)
 
     terminal_fill(' ', VGA_COLOR_WHITE, VGA_COLOR_BLUE);
 
-    terminal_writestring("Page Fault handler fired.\nError code ");
+    terminal_writestring("Page Fault handler fired by ");
+    terminal_writestring(tasks[currentTask].imageName);
+    terminal_writestring(".\nError code ");
     terminal_print_ulong_hex(errorCode);
     terminal_writestring("\nOffending instruction at ");
     terminal_print_ulong_hex(address);

MyOS_1/Interrupts/System_Calls.c

@@ -187,7 +187,7 @@ void SystemCallPageAllocator(unsigned int pages, unsigned int *pPagesAllocated,
         push pReturnVal
         push pPagesAllocated
         push pages
-        int  SYSCALL_PAGE_ALLOCATOR  // call PageAllocator(pagesToAllocate, pPagesAllocated, pReturnVal);
+        int  SYSCALL_PAGE_ALLOCATOR  // call page_allocator_interrupt_handler(pagesToAllocate, pPagesAllocated, pReturnVal);
         add esp, pointerSize         // restore value of stack pointer
     }
 }

MyOS_1/Tasks/Context.h

@@ -2,6 +2,7 @@
 #include "../misc.h"
 #include "../printf.h"
 #include <stdint.h>
+#include "../paging.h"
 
 // TODO: Make less ghetto
 #define MAX_TASKS               64
@@ -58,6 +59,6 @@ extern uint32_t nextPID;
 
 extern bool multiEnable; // TEMPTEMP
 
-void DispatchNewTask(uint32_t programStart, uint32_t newPageDirectory, uint32_t stackSize, const char *imageName, bool exclusive);
+void DispatchNewTask(uint32_t programStart, PAGE_DIRECTORY_ENTRY *newPageDirectory, uint32_t stackSize, const char *imageName, bool exclusive);
 
 void SwitchTask(uint32_t taskIndex);

MyOS_1/Tasks/Dispatcher.c

@@ -1,6 +1,7 @@
 #include "Context.h"
 #include "../printf.h"
 #include "../Interrupts/System_Calls.h"
+#include "../paging.h"
 
 PROCESS_CONTROL_BLOCK tasks[64] = { 0 };
 READY_QUEUE_ENTRY *readyQueueHead = NULL;
@@ -12,7 +13,7 @@ uint32_t nextPID = 1000;
 // This must be global so we can access it while playing with the stack in ways the compiler can't predict
 uint32_t stackPtr;
 
-void DispatchNewTask(uint32_t programStart, uint32_t newPageDirectory, uint32_t stackSize, const char *imageName, bool exclusive)
+void DispatchNewTask(uint32_t programStart, PAGE_DIRECTORY_ENTRY *newPageDirectory, uint32_t stackSize, const char *imageName, bool exclusive)
 {
     // disable interrupts
     __asm cli
@@ -62,7 +63,7 @@ void DispatchNewTask(uint32_t programStart, uint32_t newPageDirectory, uint32_t
     strncpy(tasks[taskSlot].imageName, imageName, MAX_IMAGE_NAME_LENGTH - 1);
     tasks[taskSlot].inUse = true;
     tasks[taskSlot].PID = nextPID++;
-    tasks[taskSlot].cr3 = newPageDirectory;
+    tasks[taskSlot].cr3 = (uint32_t)newPageDirectory;
 
     // Create ready queue entry
     READY_QUEUE_ENTRY *queueEntry;

MyOS_1/main.c

@@ -118,6 +118,7 @@ void KeStartupPhase2(multiboot_info *multibootInfo)
     tasks[0].inUse = true;
     strncpy(tasks[0].imageName, "KERNEL PROCESS", sizeof("KERNEL PROCESS"));
     tasks[0].PID = nextPID - 1;
+    tasks[0].cr3 = pageDir;
 
     // Initialize interrupts
     Interrupts_Init();

MyOS_1/paging.c

@@ -2,7 +2,8 @@
 #include "Paging.h"
 #include "Console_VGA.h"
 #include <stdint.h>
-#include "Interrupts\System_Calls.h"
+#include "Interrupts/System_Calls.h"
+#include "Tasks/Context.h"
 
 // Allocate space for paging structures. We need enough space for three arrays with 0x1000 32-bit entries each.
 // Each array must be aligned on a 0x1000-byte boundary.
@@ -27,6 +28,13 @@ uint32_t nextPageDirectory; // TEMPTEMP where the next created page directory wi
 // TODO: Make multi-threading safe
 void KPageAllocator(unsigned int pages, unsigned int *pPagesAllocated, uint32_t *pRetVal)
 {
+    // Ensure interrupts are disabled
+    __asm
+    {
+        pushf
+        cli
+    }
+
     *pPagesAllocated = 0;
 
     // make sure there's enough pages available
@@ -49,19 +57,42 @@ void KPageAllocator(unsigned int pages, unsigned int *pPagesAllocated, uint32_t
 
     uint32_t nextPage = pagingNextAvailableMemory / FOUR_MEGABYTES;
 
+    // Get the page directory we'll be using
+    PAGE_DIRECTORY_ENTRY *pageDirectory = (PAGE_DIRECTORY_ENTRY *)tasks[currentTask].cr3;
+
     // Add each page to the page directory
     for (size_t allocated = 0; allocated < pages; ++allocated)
     {
         // Add the current page to the page directory
-        pageDir[nextPage] = ((nextPage * FOUR_MEGABYTES)
+        pageDirectory[nextPage] = ((nextPage * FOUR_MEGABYTES)
             | DIRECTORY_ENTRY_PRESENT | DIRECTORY_ENTRY_USER_ACCESSIBLE | DIRECTORY_ENTRY_WRITABLE | DIRECTORY_ENTRY_4MB);
+
+        // If we're mapping this into the kernel space, we need to copy that mapping into every running task
+        if (pageDirectory == pageDir)
+        {
+            for (int i = 0; i < MAX_TASKS; ++i)
+            {
+                if (!tasks[i].inUse || tasks[i].cr3 == pageDir)
+                    continue;
+
+                PAGE_DIRECTORY_ENTRY *otherPageDir = (PAGE_DIRECTORY_ENTRY *)tasks[i].cr3;
+
+                otherPageDir[nextPage] = ((nextPage * FOUR_MEGABYTES)
+                                           | DIRECTORY_ENTRY_PRESENT | DIRECTORY_ENTRY_USER_ACCESSIBLE | DIRECTORY_ENTRY_WRITABLE | DIRECTORY_ENTRY_4MB);
+            }
+        }
 
         // update pointers and stuff
         ++nextPage;
         --paging4MPagesAvailable;
         pagingNextAvailableMemory += FOUR_MEGABYTES;
         ++(*pPagesAllocated);
     }
+
+    //kprintf("Task: %s\n", tasks[currentTask].imageName);
+    //Paging_Print_Page_Table(pageDirectory);
+
+    __asm popf
 }
 
 bool Paging_Print_Page_Table(PAGE_DIRECTORY_ENTRY *thePageDir)

Release/MyOS_1.dll

@@ -130,11 +130,12 @@
       <AdditionalDependencies>%(AdditionalDependencies)</AdditionalDependencies>
       <IgnoreAllDefaultLibraries>true</IgnoreAllDefaultLibraries>
       <LinkTimeCodeGeneration>Default</LinkTimeCodeGeneration>
-      <BaseAddress>0xC00000</BaseAddress>
+      <BaseAddress>0x800000</BaseAddress>
       <EntryPointSymbol>main</EntryPointSymbol>
       <RandomizedBaseAddress>false</RandomizedBaseAddress>
       <StackReserveSize>0x100000</StackReserveSize>
       <StackCommitSize>0x100000</StackCommitSize>
+      <FixedBaseAddress>true</FixedBaseAddress>
     </Link>
     <PostBuildEvent>
       <Command>copy "$(TargetDir)$(TargetFileName)" C:\Users\Administrator\.VirtualBox\TFTP\$(TargetFileName)</Command>