map on page fault

1 files changed, 48 insertions, 21 deletions

diff --git a/kernel/src/mem/paging.c b/kernel/src/mem/paging.c
index fdd1dd2..cd1cb68 100644
--- a/kernel/src/mem/paging.c
+++ b/kernel/src/mem/paging.c
@@ -2,42 +2,69 @@
 #include <paging.h>
 
 #include <libk/stdio.h>
+#include <debug.h>
 
 void load_pt_lvl4(uint64_t*);
 
 __attribute__((aligned(4096))) uint64_t page_table_lvl4[512];
 __attribute__((aligned(4096))) uint64_t page_table_lvl3[512];
-__attribute__((aligned(4096))) uint64_t page_table_lvl2_hh[512];
+__attribute__((aligned(4096))) uint64_t page_table_lvl2_0[512];
+__attribute__((aligned(4096))) uint64_t page_table_lvl2_1[512];
+__attribute__((aligned(4096))) uint64_t page_table_lvl2_2[512];
+__attribute__((aligned(4096))) uint64_t page_table_lvl2_3[512];
 
-#define PAGE_SIZE 0x00200000
-#define FLAG_PRESENT 0x1
-#define FLAG_WRITABLE 0x2
-#define FLAG_HUGE 0x80
-#define KERNEL_VMA 0xc0000000
-
-void init_paging(void)
+void map_addr(uint64_t virt, uint64_t phys, uint32_t flags)
 {
-	page_table_lvl4[0] = (uint64_t)page_table_lvl3 + FLAG_PRESENT + FLAG_WRITABLE - KERNEL_VMA;
-	page_table_lvl3[3] = (uint64_t)page_table_lvl2_hh + FLAG_PRESENT + FLAG_WRITABLE - KERNEL_VMA;
+	virt -= virt % 0x00200000;
+	phys -= phys % 0x00200000;
 
-	// higher half kernel
-	// 0xc0000000 - 0xc0400000 : 0xc0000000 - 0xc0400000
-	for (uint64_t i = 0; i < 2; i++) {
-		page_table_lvl2_hh[i] = i * PAGE_SIZE + FLAG_PRESENT + FLAG_WRITABLE + FLAG_HUGE;
+	// i is in range [0, 511]
+	size_t pt_lvl4_i = (virt >> 39) % 0x200; // 512gb entry
+	size_t pt_lvl3_i = (virt >> 30) % 0x200; // 1gb entry
+	size_t pt_lvl2_i = (virt >> 21) % 0x200; // 2mb entry
+//	size_t pt_lvl1_i = (virt >> 12) % 0x200; // 4kb entry
+
+	// first 4gb
+	if (pt_lvl4_i == 0) {
+		switch(pt_lvl3_i) {
+			case 0:
+				page_table_lvl2_0[pt_lvl2_i] = phys | flags;
+				break;
+			case 1:
+				page_table_lvl2_1[pt_lvl2_i] = phys | flags;
+				break;
+			case 2:
+				page_table_lvl2_2[pt_lvl2_i] = phys | flags;
+				break;
+			case 3:
+				page_table_lvl2_3[pt_lvl2_i] = phys | flags;
+				break;
+		}
 	}
+}
 
-	// TODO: remove initial mapping for fb and instead page on demand
+void init_paging(void)
+{
+	page_table_lvl4[0] = (uint64_t)page_table_lvl3 + FLAG_PRESENT + FLAG_WRITABLE - KERNEL_VMA;
+	page_table_lvl3[0] = (uint64_t)page_table_lvl2_0 + FLAG_PRESENT + FLAG_WRITABLE - KERNEL_VMA;
+	page_table_lvl3[1] = (uint64_t)page_table_lvl2_1 + FLAG_PRESENT + FLAG_WRITABLE - KERNEL_VMA;
+	page_table_lvl3[2] = (uint64_t)page_table_lvl2_2 + FLAG_PRESENT + FLAG_WRITABLE - KERNEL_VMA;
+	page_table_lvl3[3] = (uint64_t)page_table_lvl2_3 + FLAG_PRESENT + FLAG_WRITABLE - KERNEL_VMA;
 
-	// identity paged for fb
-	// 0xe0000000 - 0xffffffff : 0xe0000000 - 0xffffffff
-	for (uint64_t i = 2; i < 512; i++) {
-		page_table_lvl2_hh[i] = i * PAGE_SIZE + 0xc0000000 + FLAG_PRESENT + FLAG_WRITABLE + FLAG_HUGE;
-	}
+	// higher half map first 4mb
+	map_addr(KERNEL_VMA, 0x00000000, FLAG_PRESENT + FLAG_WRITABLE + FLAG_HUGE);
+	map_addr(KERNEL_VMA + PAGE_SIZE, 0x00000000 + PAGE_SIZE, FLAG_PRESENT + FLAG_WRITABLE + FLAG_HUGE);
 
 	load_pt_lvl4(page_table_lvl4);
 }
 
+
 void page_fault(uint64_t error)
 {
-	printf("%d\n", error);
+	uint64_t addr;
+	__asm__ volatile ("mov %%cr2, %0" : "=r"(addr) : : "memory");
+
+	map_addr(addr, addr, FLAG_PRESENT | FLAG_WRITABLE | FLAG_HUGE);
+
+	printf("address: 0x%x, error code: %d\n", addr, error);
 }