From 9436e6e0332ee2564b01497b81e272ac379166e2 Mon Sep 17 00:00:00 2001
From: Nigel <nigelbarink@hotmail.com>
Date: Fri, 19 Aug 2022 01:05:10 +0200
Subject: [PATCH] End of the day cleanup.

* Added symbol files to .gitignore
* Improved text in #PG and #GP handlers
* Added the printing of the multiboot structure address and the magic value
* Added page fault screenshot to readme
---
 .gitignore                        |  2 ++
 README.md                         |  5 ++++
 screenshots/PageFault.png         |  3 +++
 src/kernel/Interrupts/idt/idt.cpp | 38 +++++++++++++++----------------
 src/kernel/kernel.cpp             |  6 +++--
 5 files changed, 32 insertions(+), 22 deletions(-)
 create mode 100644 screenshots/PageFault.png

diff --git a/.gitignore b/.gitignore
index 3ac905f..82ca499 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,4 +5,6 @@ isodir/
 root/
 *.iso
 *.img
+*.sym
+
 
diff --git a/README.md b/README.md
index 2e5fbb6..155afd0 100644
--- a/README.md
+++ b/README.md
@@ -16,6 +16,11 @@ W.I.P - Working on interrupt handling
 
 ![Multiboot integration](screenshots/multiboot.png) \
 Multiboot information can be read by the kernel.
+
+![Page faulting](screenshots/PageFault.png) \
+Enabled paging and am getting page faults!
+
+
 ________________________
 
 ### The goal
diff --git a/screenshots/PageFault.png b/screenshots/PageFault.png
new file mode 100644
index 0000000..adc5332
--- /dev/null
+++ b/screenshots/PageFault.png
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:edf3a8ff640f0a3fbf58756d10526ee3bc03068d0cea4d81d64a897d52e29c85
+size 10406
diff --git a/src/kernel/Interrupts/idt/idt.cpp b/src/kernel/Interrupts/idt/idt.cpp
index 4c5f934..8b4fd83 100644
--- a/src/kernel/Interrupts/idt/idt.cpp
+++ b/src/kernel/Interrupts/idt/idt.cpp
@@ -122,31 +122,29 @@ void irs_handler (registers regs) {
             // General Protection Exception #GP
             printf("#GP\n");
 
-
-            printf("ERR_CODE: 0x%x", regs.err_code);
+            printf("Accessing memory caused a general protectuion exception.\n");
             
-            if( regs.err_code & 0x1)
-            {
-                printf("Originated externally!");
-            }
+            printf("Fault due to entry at index: %d", (regs.err_code >> 3 & 0xFFF ) );
 
             if(regs.err_code & 0x3 >> 1 == 0   ){
-                printf("Index references GDT");
+                printf("* Index references GDT");
             }
             if(regs.err_code & 0x3 >> 1 == 1  ){
-                printf("Index references IDT");
+                printf("* Index references IDT");
             }
 
             if(regs.err_code & 0x3 >> 1 == 2   ){
-                printf("Index references LDT");
+                printf("* Index references LDT");
             }
 
             if(regs.err_code & 0x3 >> 1 == 4  ){
-                printf("Index references IDT");
+                printf("* Index references IDT");
             }
 
-
-            printf("Index: ", (regs.err_code >> 3 & 0xFFF ) );
+            if( regs.err_code & 0x1)
+            {
+                printf("* Originated externally!");
+            }
 
             __asm__("cli;" "1: hlt;" "jmp 1b;");
 
@@ -157,7 +155,7 @@ void irs_handler (registers regs) {
             printf("#PF\n");
 
             FaultingAddress = GetCR2();
-            printf("Faulting instruction adddress: 0x%x\n", FaultingAddress);
+            printf("Accessing the linear address 0x%x resulted in a page fault!\n\n", FaultingAddress);
         
             // Error code of 32 bits are on the stack
             // CR2 register contains the 32-bit linear virtual address that generated the exception
@@ -171,27 +169,27 @@ void irs_handler (registers regs) {
             #define PF_ERR_SHADOW_STACK_BIT 0x7
             #define PF_ERR_SOFTWARE_GUARD_EXTENSION_BIT 0xE
 
-            printf("Determining cause of fault...\n");
+            printf("REASON: \n\n");
 
          
             if (regs.err_code & PF_ERR_PRESENT_BIT ){
-                printf("Page protection violation!\n");
+                printf("* Page protection violation!\n");
             } else{
-                printf("page not-present!\n");
+                printf("* Page not-present!\n");
             }
 
             if(regs.err_code & PF_ERR_WRITE_BIT){
-                printf("Write access violation!\n");
+                printf("* Write access violation!\n");
             } else{
-                printf("Read access violation!\n");
+                printf("* Read access violation!\n");
             }
 
             if(regs.err_code & PF_ERR_USER_BIT){
-                printf("Violation from user-space (CPL=3)\n");
+                printf("* Violation from user-space (CPL=3)\n");
             }
 
             if(regs.err_code & PF_ERR_INSTRUCTION_FETCH_BIT){
-                printf("Caused by an instruction fetch. \n");
+                printf("* Caused by an instruction fetch. \n");
             }
 
             /*
diff --git a/src/kernel/kernel.cpp b/src/kernel/kernel.cpp
index 8409b44..22aa47f 100644
--- a/src/kernel/kernel.cpp
+++ b/src/kernel/kernel.cpp
@@ -48,6 +48,8 @@ extern "C" void early_main(unsigned long magic, unsigned long addr){
     // Reload CR3 to force a flush
     asm("movl %cr3, %ecx;" "movl %ecx, %cr3" );
     */
+
+    printf("DEBUG:\n Magic: 0x%x\n MBT_addr: 0x%x\n", magic, addr);
     /**
      * Check Multiboot magic number
      * NOTE: Printf call should not be a thing this early on ...
@@ -61,12 +63,12 @@ extern "C" void early_main(unsigned long magic, unsigned long addr){
      * Show a little banner for cuteness
      */
     printf("|===    BarinkOS       ===|\n");
-    
+    const uint32_t KERNEL_BASE_ADDR = 0xC0000000;
     /**
      * Use the address given as an argument as the pointer
      * to a Multiboot information structure.
      */
-        multiboot_info_t* mbt = (multiboot_info_t*) addr;
+        multiboot_info_t* mbt = (multiboot_info_t*) (addr + KERNEL_BASE_ADDR);
 
     /**
      * Construct our own bootInfo structure