1 files changed, 88 insertions, 0 deletions
diff --git a/arch/i386/kernel/paging.c b/arch/i386/kernel/paging.c
new file mode 100644
index 0000000..d8f72a3
--- /dev/null
+++ b/arch/i386/kernel/paging.c
@@ -0,0 +1,88 @@
+#include <kernel/paging.h>
+#include <kernel/io.h>
+#include <kernel/syscall.h>
+#include <kernel/string.h>
+#include <kernel/alloc.h>
+#include <stddef.h>
+
+extern int halt_catch_fire();
+extern uint32_t _kernel_start;
+extern uint32_t _kernel_end;
+static uint32_t *kstart = &_kernel_start;
+static uint32_t *kend = (uint32_t)(&_kernel_end) - 0xC0000000;
+
+static uint32_t page_directory[1024] __attribute__((aligned(PAGE_SIZE)));
+static uint32_t first_page_table[1024] __attribute__((aligned(PAGE_SIZE)));
+
+static int paging_enabled = 0;
+
+void paging_init(void) {
+        for (int i = 0; i < 1024; i++)
+                page_directory[i] = 0x00000002;
+
+        page_directory[1023] = ((uint32_t)&page_directory - 0xC0000000) | 3;
+        page_directory[0] = ((uint32_t)&first_page_table - 0xC0000000) | 3;
+        page_directory[768] = ((uint32_t)&first_page_table - 0xC0000000) | 3;
+        for (uint32_t i = kstart; i < kend; i += 4096) {
+                map_page(i, get_vaddr(i), 0x003);
+                mark_bitmap(i, 1);
+        }
+
+        map_page(0xB8000, 0xC03FF000, 0x003);
+        mark_bitmap(0xB8000, 1);
+
+        load_page_dir(((uint32_t)&page_directory) - 0xC0000000);
+        enable_paging();
+        paging_enabled = 1;
+        return;
+}
+
+void page_fault_handler(struct isr_frame *frame) {
+        kprintf("Page fault detected\n");
+        uint32_t errno = frame->errno;
+
+        uint32_t fault_addr;
+        __asm__ volatile("movl %%cr2, %0" : "=r"(fault_addr));
+        kprintf("Fault occured at address %x\n", fault_addr);
+        uint32_t present = errno & ERR_PRESENT;
+        uint32_t rw = errno & ERR_RW;
+        uint32_t user = errno & ERR_USER;
+        uint32_t reserved = errno & ERR_RESERVED;
+        uint32_t ifetch = errno & ERR_INST;
+        kprintf("Possible causes:\n");
+        if (!present) kprintf("\tPage not present\n");
+        if (rw || user) kprintf("\tPage is read only\n");
+        if (reserved) kprintf("\tOverwrote reserved bits\n");
+        if (ifetch) kprintf("\tInstruction fetch\n");
+        halt_catch_fire(frame);
+}
+
+uint32_t get_paddr(uint32_t vaddr) {
+        uint32_t pdindex = vaddr >> 22;
+        uint32_t ptindex = vaddr >> 12 & 0x03FF;
+
+        uint32_t *page_table = (page_directory[pdindex] + 0xC0000000 & 0xFFFFF000);
+        return (page_table[ptindex] & 0xFFFFF000) | (vaddr & 0x00000FFF);
+}
+
+uint32_t get_vaddr(uint32_t paddr) {
+        return paddr + 0xC0000000;
+}
+
+void map_page(uint32_t paddr, uint32_t vaddr, uint32_t flags) {
+        uint32_t pdindex = vaddr >> 22;
+        uint32_t ptindex = vaddr >> 12 & 0x03FF;
+
+        uint32_t *page_table = (page_directory[pdindex] + 0xC0000000 & 0xFFFFF000);
+        uint32_t *pte = (uint32_t*)(&page_table[ptindex]);
+        *pte |= paddr | (flags & 0xFFF) | 0x01;
+}
+
+void unmap_page(uint32_t vaddr) {
+        uint32_t pdindex = vaddr >> 22;
+        uint32_t ptindex = vaddr >> 12 & 0x03FF;
+
+        uint32_t *page_table = (page_directory[pdindex] + 0xC0000000 & 0xFFFFF000);
+        uint32_t *pte = (uint32_t*)(&page_table[ptindex]);
+        *pte &= 0;
+}