Enable .bss zeroing and improve paging

src/boot/boot.S

@@ -3,6 +3,8 @@
 .extern bringelle
 .extern gdt_memcpy
 .extern mb_load_fb_tag
+.extern _bss_start
+.extern _bss_end
 
 .set STACK_LOCATION, 0x1FFFFF
 
@@ -73,6 +75,17 @@ movl $STACK_LOCATION,%esp
 mov $0x38, %eax
 ltr %ax
 
+# Zeroing the .bss section
+mov $_bss_start, %eax
+mov $_bss_end, %ebx
+start_zeroing:
+    movb $0x0, (%eax)
+    cmp %eax, %ebx
+    je end_zeroing
+    inc %eax
+    jmp start_zeroing
+end_zeroing:
+
 # Start kernel main function
 call bringelle
 

src/bringelle.c

@@ -27,6 +27,11 @@ void bringelle(){
   print("Paging enable!\n");
   print("Kernel started !");
 
+  paging_allocate(5);
+  print("\n");
+  paging_dump(1024,-1);
+  print("\n");
+
   show_tics=1;
   // Utask
   print("Launch user task ");
@@ -54,6 +59,7 @@ void bringelle(){
   while(1);
 }
 
+
 void clock(){
   static int tic=0;
   static int sec=0;
@@ -66,7 +72,6 @@ void clock(){
   }
 }
 
-
 void page_fault(){
   print("Page fault!");
 }

src/core/paging.c

@@ -1,21 +1,43 @@
 #include "paging.h"
+#include "libc/stdio.h"
+
+/// Use a bitmap to keep track of allocated pages
+char pages_status[PAGING_MAX_PAGES/8];
+/// Kernel page directory (ATTENTION need to be 4096)
+u32 k_pd[PAGING_MAX_DIR_ENTRY] __attribute__((aligned(4096)));
+/// Kernel page table
+u32 k_pt[PAGING_MAX_DIR_ENTRY][1024] __attribute__((aligned(4096)));
 
 void paging_enable(){
-    int *page_dir=(int*)PAGING_DIR_LOCATION;
+    // Init pages status
-    int *page_table=(int*)PAGING_TABLE_LOCATION;
+    for(int i=0;i<PAGING_MAX_PAGES/8;i++)
+        pages_status[i]=0;
 
     // Init page directory
-    for(int i=0;i<1024;i++)
+    for(int i=0;i<PAGING_MAX_DIR_ENTRY;i++){
-        page_dir[i]=0;
+        k_pd[i]=0;
-    page_dir[0]=(int)page_table;
+    }
-    page_dir[0] |=7; // Permissions
+    k_pd[0]=((int)&k_pt[0][0]);
+    k_pd[0]|=7; // Permissions
 
     // Init page table 0
     int addr_offset=0;
     for(int i=0;i<1024;i++){
-        page_table[i]=addr_offset;
+        k_pt[0][i]=addr_offset;
-        page_table[i]|=7; // Permission
+        k_pt[0][i]|=7; // Permission
-        addr_offset+=4096; // 4Ko pages
+        paging_set_usage(addr_offset,1); // Mark addr as used
+        addr_offset+=PAGING_PAGE_SIZE; // 4Ko pages
+    }
+
+    // Allow access to more ram
+    for(int i=1;i<PAGING_MAX_DIR_ENTRY;i++){
+        k_pd[i]=((int)&k_pt[i][0]);
+        k_pd[i]|=7; // Permissions
+        for(int j=0;j<1024;j++){
+            k_pt[i][j]=addr_offset;
+            k_pt[i][j]|=7; // Permission
+            addr_offset+=PAGING_PAGE_SIZE; // 4Ko pages
+        }
     }
 
     // Turns on paging
@@ -25,7 +47,63 @@ void paging_enable(){
         "movl %%cr0, %%eax    \n\t"
         "orl %1, %%eax        \n\t"
         "movl %%eax, %%cr0    \n\t" // Turn on paging
-        :: "i" (PAGING_DIR_LOCATION), "i" (PAGING_CR0_BIT)
+        :: "b" (k_pd), "i" (PAGING_CR0_BIT)
     );
-
+}
+void paging_set_usage(int addr,char state){
+    char bytes=pages_status[addr/PAGING_PAGE_SIZE/8];
+    char bit=addr/PAGING_PAGE_SIZE%8;
+    if(state=0)
+        pages_status[addr/PAGING_PAGE_SIZE/8]=~(1<<bit)&bytes;
+    else
+        pages_status[addr/PAGING_PAGE_SIZE/8]=(1<<bit)|bytes;
+}
+
+void paging_dump(int min,int max){
+    for(int i=0;i<(PAGING_MAX_PAGES/8);i++){
+        for(int j=0;j<8;j++){
+            char status=(pages_status[i]>>j)&0x1;
+            if((i*8+j)>=min){
+                if((i*8+j)<max || max<0)
+                    printi(status);
+            }
+        }
+    }
+}
+
+char* paging_allocate_next_page(){
+    for(int i=0;i<(PAGING_MAX_PAGES/8);i++){
+        char bytes=pages_status[i];
+        for(int j=0;j<8;j++){
+            char state=(bytes>>j)&1;
+            if(state!=1){
+                int page_id=i*8+j;
+                int page_addr=PAGING_PAGE_SIZE*page_id;
+                paging_set_usage(page_addr,1);
+                return((char*)page_addr);
+            }
+        }
+    }
+    print("Could not allocate anymore pages! Stopping...");
+    asm("hlt");
+}
+
+
+char *paging_allocate(int p){
+    int *page_dir=(int*)paging_allocate_next_page();
+    int *page_table;
+    int current_page_entry=0;
+    int current_dir_entry=0;
+    while(current_page_entry<p){
+        if(current_page_entry%1024 == 0){
+            current_dir_entry++;
+            page_table=(int*)paging_allocate_next_page();
+            page_dir[current_dir_entry]=(int)page_table;
+        }
+        int entry=current_page_entry%1024;
+        page_table[current_page_entry]=(int)paging_allocate_next_page();
+        current_page_entry++;
+        print("Jean\n");
+    }
+    print("end");
 }

src/core/paging.h

@@ -2,12 +2,25 @@
 #define PAGING_H
 
 #define PAGING_CR0_BIT 0x80000000
-#define PAGING_DIR_LOCATION 0x1000
+#define PAGING_PAGE_SIZE 4096
-#define PAGING_TABLE_LOCATION 0x5000
+#define PAGING_MAX_PAGES 2048
+#if PAGING_MAX_PAGES%1024>0
+    #define PAGING_MAX_DIR_ENTRY PAGING_MAX_PAGES/1024+1
+#else
+    #define PAGING_MAX_DIR_ENTRY PAGING_MAX_PAGES/1024
+#endif
 
 /*
  * Configure and enable paging
  */
 void paging_enable();
 
+char* paging_allocate_next_page();
+void paging_set_usage(int addr,char state);
+/**
+ * Create a new page directory containing
+ * p pages.
+ */
+char *paging_allocate(int p);
+void paging_dump(int min,int max);
 #endif

src/core/scheduler.h

@@ -0,0 +1,5 @@
+#ifndef SCHEDULER_H
+#define SCHEDULER_H
+
+
+#endif

src/linker.ld

@@ -5,23 +5,25 @@ OUTPUT_ARCH(i386)
 SECTIONS {
 
     . = 1M;
-    .text :
+    .text : ALIGN(4)
     {
         *(.multiboot)
         *(.text)
     }
-    .rodata :
+    .rodata : ALIGN(4)
     {
         *(.rodata)
     }
-    .data :
+    .data : ALIGN(4)
     {
         *(.data)
     }
-    .bss :
+    .bss : ALIGN(4)
     {
-        *(.bss)
+        _bss_start = .;
-        *(COMMON)
+        *(.bss);
+        _bss_end = .;
+        *(COMMON);
     }
 
 }