feature (kernel): implemented Page Maps

kernel/inc/mm/page_map.h

@@ -0,0 +1,58 @@
+/* Copyright (C) Antifallobst <antifallobst@systemausfall.org>
+ *
+ * NoxOS is free software:
+ * you can redistribute it and/or modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3 of the License,
+ * or (at your option) any later version.
+ *
+ * NoxOS is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
+ * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with this program.
+ * If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef NOX_PAGE_MAP_H
+#define NOX_PAGE_MAP_H
+
+#include "utils/stdtypes.h"
+#include "boot/boot_info.h"
+
+#define VIRTUAL_ADDRESS_MAX 0x1000000000000     // 256 TB (the limit of PML4s)
+
+typedef enum {
+    PM_FLAG_PRESENT         = 0b0000000000000001,   // 1 << 0
+    PM_FLAG_READ_WRITE      = 0b0000000000000010,   // 1 << 1
+    PM_FLAG_USER_SUPER      = 0b0000000000000100,   // 1 << 2
+    PM_FLAG_WRITE_THROUGH   = 0b0000000000001000,   // 1 << 3
+    PM_FLAG_CACHE_DISABLED  = 0b0000000000010000,   // 1 << 4
+    PM_FLAG_ACCESSED        = 0b0000000000100000,   // 1 << 5
+    PM_FLAG_LARGER_PAGES    = 0b0000000010000000,   // 1 << 7
+    PM_FLAG_CUSTOM_0        = 0b0000001000000000,   // 1 << 9
+    PM_FLAG_CUSTOM_1        = 0b0000010000000000,   // 1 << 10
+    PM_FLAG_CUSTOM_2        = 0b0000100000000000,   // 1 << 11
+    PM_FLAG_NO_EXECUTE      = 0x8000000000000000    // 1 << 63
+} page_map_flag_E;
+
+typedef struct {
+    uint64_t entries[512];
+}__attribute__((aligned(0x1000))) page_map_T;
+
+page_map_T*         page_map_create                 ();
+extern page_map_T*  page_map_fetch_current          ();
+extern void         page_map_load                   (page_map_T* page_map);
+void                page_map_map_memory             (page_map_T* page_map, void* virtual_address, void* physical_address, uint64_t flags);
+void                page_map_unmap_memory           (page_map_T* page_map, void* virtual_address);
+void                page_map_destruct               (page_map_T* page_map);
+
+void                page_map_entry_set_flags        (uint64_t* entry, uint64_t flags);
+bool                page_map_entry_get_flag         (uint64_t* entry, page_map_flag_E flag);
+void                page_map_entry_set_address      (uint64_t* entry, void* address);
+void*               page_map_entry_get_address      (uint64_t* entry);
+
+void                paging_init                     (boot_info_T* boot_info);
+
+extern page_map_T* g_kernel_page_map;
+
+#endif //NOX_PAGE_MAP_H

kernel/src/kmain.c

@@ -19,6 +19,9 @@
 #include "platform/gdt.h"
 #include "platform/interrupts.h"
 #include "mm/page_frame.h"
+#include "mm/page_map.h"
+
+#include "utils/memory.h"
 
 void limine_terminal_print(boot_info_T* boot_info, string_t string) {
     boot_info->terminal->write(boot_info->terminal->terminals[0], string, string_length(string));
@@ -28,6 +31,7 @@ void kernel_init(boot_info_T* boot_info) {
     gdt_init();
     pframe_manager_init(boot_info);
     idt_init();
+    paging_init(boot_info);
 }
 
 void kmain(boot_info_T boot_info) {
@@ -38,7 +42,12 @@ void kmain(boot_info_T boot_info) {
     kernel_init(&boot_info);
 
     // this should cause a kernel panic
-    int x = 1312 / 0;
+//    int x = 1312 / 0;
+
+    page_map_map_memory(g_kernel_page_map, (void*)0x100000000000, pframe_request(), PM_FLAG_READ_WRITE);
+    memory_copy("test string", (void*)0x100000000000, 13);
+    log(LOG_DEBUG, (string_t)0x100000000000);
+
 
     CORE_HALT_FOREVER
 }

kernel/src/mm/page_map.c

@@ -0,0 +1,97 @@
+/* Copyright (C) Antifallobst <antifallobst@systemausfall.org>
+ *
+ * NoxOS is free software:
+ * you can redistribute it and/or modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3 of the License,
+ * or (at your option) any later version.
+ *
+ * NoxOS is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
+ * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with this program.
+ * If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include "mm/page_map.h"
+#include "mm/page_frame.h"
+#include "mm/memory_map.h"
+#include "utils/memory.h"
+#include "utils/math.h"
+#include "utils/logger.h"
+
+page_map_T* g_kernel_page_map;
+
+page_map_T* page_map_create() {
+    page_map_T* page_map = pframe_request();
+    memory_set(page_map, 0, PFRAME_SIZE);
+
+    return page_map;
+}
+
+page_map_T* page_map_request_entry(page_map_T* page_map, uint16_t index) {
+    uint64_t* entry = &page_map->entries[index];
+
+    if (page_map_entry_get_flag(entry, PM_FLAG_PRESENT)) {
+        return page_map_entry_get_address(entry);
+    }
+
+    page_map_T* table = pframe_request();
+    memory_set(table, 0, PFRAME_SIZE);
+    page_map_entry_set_address(entry, (void*)((uint64_t)table >> 12));
+
+    page_map_entry_set_flags(entry, PM_FLAG_PRESENT | PM_FLAG_READ_WRITE);
+
+    return table;
+}
+
+void page_map_map_memory(page_map_T* page_map, void* virtual_address, void* physical_address, uint64_t flags) {
+    virtual_address = (void*)FLOOR_TO((uint64_t)virtual_address, PFRAME_SIZE);
+
+    // Intel's Developer Manual has a nice graph, that explains how these indexes are calculated
+    uint16_t    page_index                  =  ((uint64_t)virtual_address >> 12) & 0x1FF;
+    uint16_t    page_table_index            =  ((uint64_t)virtual_address >> 21) & 0x1FF;
+    uint16_t    page_directory_index        =  ((uint64_t)virtual_address >> 30) & 0x1FF;
+    uint16_t    page_directory_page_index   =  ((uint64_t)virtual_address >> 39) & 0x1FF;
+    page_map_T* page_directory_page         =  page_map_request_entry(page_map, page_directory_page_index);
+    page_map_T* page_directory              =  page_map_request_entry(page_directory_page, page_directory_index);
+    page_map_T* page_table                  =  page_map_request_entry(page_directory, page_table_index);
+    uint64_t*   page                        = &page_table->entries[page_index];
+
+    page_map_entry_set_address(page, (void*)((uint64_t)physical_address >> 12));
+    page_map_entry_set_flags(page, PM_FLAG_PRESENT | flags);
+}
+
+void page_map_unmap_memory(page_map_T* page_map, void* virtual_address) {
+
+}
+
+void page_map_destruct(page_map_T* page_map) {
+
+}
+
+void page_map_entry_set_flags(uint64_t* entry, uint64_t flags) {
+    *entry |= flags;
+}
+
+bool page_map_entry_get_flag(uint64_t* entry, page_map_flag_E flag) {
+    return ((*entry & flag) > 0);
+}
+
+void page_map_entry_set_address(uint64_t* entry, void* address) {
+    uint64_t masked_address = (uint64_t)address & 0x000000ffffffffff;
+
+    *entry &= 0xfff0000000000fff;
+    *entry |= (masked_address << 12);
+}
+
+void* page_map_entry_get_address(uint64_t* entry) {
+    return (void*)(*entry & 0x000ffffffffff000);
+}
+
+void paging_init(boot_info_T* boot_info) {
+    // fetching the page map that was created by the bootloader
+    g_kernel_page_map = page_map_fetch_current();
+
+    log(LOG_INFO, "Paging Initialized");
+}

kernel/src/platform/x86/paging.asm

@@ -0,0 +1,9 @@
+page_map_load:
+    mov cr3, rax
+    ret
+GLOBAL page_map_load
+
+page_map_fetch_current:
+    mov rax, cr3
+    ret
+GLOBAL page_map_fetch_current