upd paging logic

Author: tas0dev

src/boot/config.inc

@@ -1,5 +1,5 @@
 KERNEL_OFFSET EQU 0x10000       ; カーネルをロードするアドレス
-SECTOR_COUNT  EQU 39            ; 読み込むセクタの数
+SECTOR_COUNT  EQU 40            ; 読み込むセクタの数
 START_SECTOR  EQU 2             ; 開始するセクタ番号
 CYLINDER_NUM  EQU 0             ; シリンダ番号
 HEAD_NUM      EQU 0             ; ヘッド番号

src/include/mem/paging.h

@@ -4,12 +4,16 @@
 void paging_init_identity(uint32_t map_mb);
 void paging_enable(void);
 
+#include <stddef.h>
+
 #define PAGING_PRESENT 0x1
 #define PAGING_RW      0x2
 #define PAGING_USER    0x4
 
 void *alloc_page_table(void);
 int map_page(uint32_t phys, uint32_t virt, uint32_t flags);
 int unmap_page(uint32_t virt);
+int map_range(uint32_t phys_start, uint32_t virt_start, size_t size, uint32_t flags);
+void page_fault_handler_ex(uint32_t vec, uint32_t error_code, uint32_t eip);
 
 #endif /* _MEM_PAGING_H */

src/kernel/interrupt/idt.c

@@ -84,6 +84,7 @@ void irq_handler_c(uint32_t vec) {
 }
 
 extern void page_fault_handler(uint32_t vec);
+extern void page_fault_handler_ex(uint32_t vec, uint32_t error_code, uint32_t eip);
 
 void irq_exception_c(uint32_t vec) {
         if (vec == 14) {
@@ -95,6 +96,20 @@ void irq_exception_c(uint32_t vec) {
         }
 }
 
+/**
+ * @fn irq_exception_ex
+ * @brief 例外発生時の拡張ハンドラ
+ */
+void irq_exception_ex(uint32_t vec, uint32_t error_code) {
+        if (vec == 14) {
+                // C言語からEIPを正確に取得するのは難しいため、ここでは0を渡す
+                page_fault_handler_ex(vec, error_code, 0);
+        } else {
+                printk("exception ex vec=%u err=0x%x\n", (unsigned)vec, (unsigned)error_code);
+                while (1) {}
+        }
+}
+
 /**
  * @fn idt_init
  * @brief IDTを初期化する

src/kernel/interrupt/irq.c

@@ -1,10 +1,10 @@
- #include <config.h>
+#include <config.h>
 
- /**
-  * @fn irq_save
-  * Save EFLAGS and disable interrupts.
-  */
- uint32_t irq_save(void) {
+/**
+ * @fn irq_save
+ * Save EFLAGS and disable interrupts.
+ */
+uint32_t irq_save(void) {
         uint32_t flags;
         asm volatile(
                 "pushf\n\t"
@@ -15,18 +15,18 @@
         );
         asm volatile("cli" ::: "memory");
         return flags;
- }
+}
 
- /**
-  * @fn irq_restore
-  * Restore EFLAGS.
-  */
- void irq_restore(uint32_t flags) {
+/**
+ * @fn irq_restore
+ * Restore EFLAGS.
+ */
+void irq_restore(uint32_t flags) {
         asm volatile(
                 "push %0\n\t"
                 "popf\n\t"
                 :
                 : "r" (flags)
                 : "memory"
         );
- }
+}

src/kernel/interrupt/irq_stubs.asm

@@ -5,18 +5,24 @@ isr_stub_table:
 
 extern irq_handler_c
 extern irq_exception_c
+extern irq_exception_ex
 
-global isr32
-isr32:
+; Exception with error code: isr14
 global isr14
 isr14:
         pusha
-        push dword 14
-        call irq_exception_c
-        add esp, 4
+        ; error code is located just above the pushed registers (pusha pushes 8 regs = 32 bytes)
+        mov eax, [esp + 32]
+        push eax               ; push error_code
+        push dword 14          ; push vector
+        call irq_exception_ex
+        add esp, 8
         popa
         iretd
 
+; IRQ handlers 32-47
+global isr32
+isr32:
         pusha
         push dword 32
         call irq_handler_c

src/kernel/mem/paging.c

@@ -68,6 +68,18 @@ int unmap_page(uint32_t virt) {
         if ((pt[pt_idx] & PAGING_PRESENT) == 0) return -1;
         pt[pt_idx] = 0;
         invlpg((void *)virt);
+
+        /* check if the page table became empty -> free it and clear PDE */
+        int empty = 1;
+        for (int i = 0; i < 1024; ++i) {
+                if (pt[i] & PAGING_PRESENT) { empty = 0; break; }
+        }
+        if (empty) {
+                uint32_t pt_phys = (uint32_t)pt; /* current identity mapping */
+                page_directory[pd_idx] = 0x00000000;
+                free_frame((void *)pt_phys);
+        }
+
         return 0;
 }
 
@@ -93,6 +105,28 @@ void paging_init_identity(uint32_t map_mb) {
         printk("paging: identity map initialized for %u MB (pages=%u)\n", (unsigned)map_mb, (unsigned)pages);
 }
 
+/**
+ * @fn map_range
+ * @brief 指定範囲を連続ページとしてマップする
+ */
+int map_range(uint32_t phys_start, uint32_t virt_start, size_t size, uint32_t flags) {
+        if (phys_start % 0x1000 || virt_start % 0x1000) return -1;
+        uint32_t pages = (size + 0xFFF) / 0x1000;
+        for (uint32_t i = 0; i < pages; ++i) {
+                if (map_page(phys_start + i * 0x1000, virt_start + i * 0x1000, flags) != 0) {
+                        return -1;
+                }
+        }
+        return 0;
+}
+
+void page_fault_handler_ex(uint32_t vec, uint32_t error_code, uint32_t eip) {
+        uint32_t fault_addr;
+        asm volatile ("mov %%cr2, %0" : "=r" (fault_addr));
+        printk("PAGE FAULT: vec=%u err=0x%x eip=0x%x cr2=0x%x\n", (unsigned)vec, (unsigned)error_code, (unsigned)eip, (unsigned)fault_addr);
+        while (1) {}
+}
+
 /**
  * @fn paging_enable
  * @brief ページングを有効化