starting to work on pty drivers, fork(), and scheduler redesign

kernel/memory/mm.c

@@ -1,8 +1,8 @@
 #include "memory/mm.h"
-#include "lib/print.h"
 #include "multiboot.h"
 
 #include <stddef.h>
+#include <lib/string.h>
 
 extern uint8_t __kernel_start;
 extern uint8_t __kernel_end;
@@ -17,6 +17,8 @@ extern uint32_t page_directory[1024];
 #define PAGE_DIRECTORY  0xFFFFF000
 
 #define TEMP_MAPPING_VADDR 0xDFFF0000
+#define TEMP_COPY_SRC      0xDFFE0000 // Safely 1 page down
+#define TEMP_COPY_DST      0xDFFD0000
 
 #define USR_PAGE 0x07
 #define SUP_PAGE 0x03
@@ -190,4 +192,77 @@ void* create_task_pd() {
     uint32_t* kernel_pt = (uint32_t*)(PAGE_TABLES + (pde * PAGE_SIZE));
     kernel_pt[pte] = 0;
     return (void*)pd_address;
+}
+
+void* clone_task_pd() {
+    uint32_t child_pd_phys = (uint32_t)p_alloc_frame();
+    if (child_pd_phys == 0) return NULL;
+
+    map_page(TEMP_MAPPING_VADDR, child_pd_phys, PAGE_PRESENT | PAGE_WRITABLE);
+    uint32_t* child_pd = (uint32_t*)TEMP_MAPPING_VADDR;
+    uint32_t* parent_pd = (uint32_t*)PAGE_DIRECTORY;
+
+    for (int i = 768; i < 1023; i++) {
+        child_pd[i] = parent_pd[i];
+    }
+
+    child_pd[1023] = child_pd_phys | PAGE_PRESENT | PAGE_WRITABLE;
+
+    for (int i = 0; i < 768; i++) {
+        child_pd[i] = 0;
+    }
+
+    for (int i = 0; i < 768; i++) {
+        uint32_t pde = parent_pd[i];
+        if (!(pde & PAGE_PRESENT)) continue;
+        uint32_t child_pt_phys = (uint32_t)p_alloc_frame();
+        
+        child_pd[i] = child_pt_phys | (pde & 0xFFF); 
+
+        map_page(TEMP_COPY_SRC, pde & ~(PAGE_SIZE - 1), PAGE_PRESENT | PAGE_WRITABLE);
+        map_page(TEMP_COPY_DST, child_pt_phys, PAGE_PRESENT | PAGE_WRITABLE);
+        flush_tlb();
+
+        uint32_t* src_pt = (uint32_t*)TEMP_COPY_SRC;
+        uint32_t* dst_pt = (uint32_t*)TEMP_COPY_DST;
+
+        for (int j = 0; j < 1024; j++) {
+            uint32_t pte = src_pt[j];
+            if (!(pte & PAGE_PRESENT)) {
+                dst_pt[j] = 0;
+                continue;
+            }
+
+            uint32_t child_frame_phys = (uint32_t)p_alloc_frame();
+            dst_pt[j] = child_frame_phys | (pte & 0xFFF);
+
+            uint32_t parent_data_phys = pte & ~(PAGE_SIZE - 1);
+            
+            map_page(TEMP_COPY_SRC, parent_data_phys, PAGE_PRESENT | PAGE_WRITABLE);
+            map_page(TEMP_COPY_DST, child_frame_phys, PAGE_PRESENT | PAGE_WRITABLE);
+            flush_tlb();
+
+            memcpy((void*)TEMP_COPY_DST, (void*)TEMP_COPY_SRC, PAGE_SIZE);
+
+            map_page(TEMP_COPY_SRC, pde & ~(PAGE_SIZE - 1), PAGE_PRESENT | PAGE_WRITABLE);
+            map_page(TEMP_COPY_DST, child_pt_phys, PAGE_PRESENT | PAGE_WRITABLE);
+            flush_tlb();
+        }
+    }
+
+    uint32_t pde_main = TEMP_MAPPING_VADDR >> 22;
+    uint32_t* pt_main = (uint32_t*)(PAGE_TABLES + (pde_main * PAGE_SIZE));
+    pt_main[(TEMP_MAPPING_VADDR >> 12) & 0x3FF] = 0;
+
+    uint32_t pde_src = TEMP_COPY_SRC >> 22;
+    uint32_t* pt_src = (uint32_t*)(PAGE_TABLES + (pde_src * PAGE_SIZE));
+    pt_src[(TEMP_COPY_SRC >> 12) & 0x3FF] = 0;
+
+    uint32_t pde_dst = TEMP_COPY_DST >> 22;
+    uint32_t* pt_dst = (uint32_t*)(PAGE_TABLES + (pde_dst * PAGE_SIZE));
+    pt_dst[(TEMP_COPY_DST >> 12) & 0x3FF] = 0;
+
+    flush_tlb();
+
+    return (void*)child_pd_phys;
 }

kernel/memory/mm.h

@@ -21,6 +21,7 @@ void* p_alloc_frame();
 uint32_t total_free_memory();
 
 void* create_task_pd();
+void* clone_task_pd();
 
 void map_page(uint32_t vaddr, uint32_t paddr, uint32_t flags);