1 files changed, 130 insertions, 0 deletions
diff --git a/kernel/arch/x86/kernel/paging.c b/kernel/arch/x86/kernel/paging.c
new file mode 100644
index 0000000..a0bbb92
--- /dev/null
+++ b/kernel/arch/x86/kernel/paging.c
@@ -0,0 +1,130 @@
+#include <kernel/paging.h>
+#include <kernel/asm.h>
+#include <kernel/vmem.h>
+#include <kernel/pmem.h>
+#include <kernel/panic.h>
+#include <kernel/syscall.h>
+#include <libk/io.h>
+#include <libk/string.h>
+
+static int paging_enabled = 0;
+
+void paging_init(void) {
+        if (paging_enabled == 1)
+                return;
+
+        uintptr_t phys_pt = pfa_alloc(1);
+        map_page(phys_pt, PAGE_TMP_MAP, PD_PRES | PD_RW);
+        uintptr_t *pt = (uintptr_t*)PAGE_TMP_MAP;
+        for (uintptr_t i = KSTART; i < KEND; i += PAGE_SIZE)
+                pt[GET_PTX(GET_VADDR(i))] = i | PD_PRES;
+        unmap_page(PAGE_TMP_MAP);
+
+        uintptr_t temp_pt = pfa_alloc(1);
+
+        uintptr_t phys_pd = pfa_alloc(1);
+        map_page(phys_pd, PAGE_TMP_MAP, PD_PRES | PD_RW);
+        uintptr_t *pd = (uintptr_t*)PAGE_TMP_MAP;
+        pd[GET_PDX(GET_VADDR(KSTART))] = phys_pt | PD_PRES | PD_RW;
+        pd[GET_PDX(PAGE_TMP_MAP)] = temp_pt | PD_PRES | PD_RW;
+        pd[1023] = phys_pd | PD_PRES | PD_RW;
+        unmap_page(PAGE_TMP_MAP);
+
+        enable_paging(phys_pd);
+        paging_enabled = 1;
+        return;
+}
+
+void init_page_table(int pdindex, uint32_t flags) {
+        uintptr_t *pd = (uintptr_t*)PAGE_DIR_MAP;
+        if ((pd[pdindex] & PD_PRES) != 0)
+                return;
+
+        uintptr_t paddr = pfa_alloc(1);
+        pd[pdindex] = paddr | PD_PRES | PD_RW | flags;
+        
+        uintptr_t *pt = ((uintptr_t*)PAGE_TAB_MAP) + (pdindex << 12);
+        pd[GET_PDX(pt)] = paddr | PD_PRES | PD_RW;
+}
+
+uintptr_t init_page_directory(void) {
+        uintptr_t ret = pfa_alloc(1);
+        map_page(ret, PAGE_TMP_MAP, PD_RW);
+
+        uintptr_t *new_pd = (uintptr_t*)PAGE_TMP_MAP;
+        uintptr_t *cur_pd = (uintptr_t*)PAGE_DIR_MAP;
+        int kernel_pdx = GET_PDX(GET_VADDR(KSTART));
+        new_pd[kernel_pdx] = cur_pd[kernel_pdx];
+
+        unmap_page(PAGE_TMP_MAP);
+        return ret;
+}
+
+void map_page(uintptr_t paddr, uintptr_t vaddr, uint32_t flags) {
+        paddr = PGROUNDDN(paddr);
+        vaddr = PGROUNDDN(vaddr);
+
+        int pdindex = GET_PDX(vaddr);
+        int ptindex = GET_PTX(vaddr);
+
+        uintptr_t *pd = (uintptr_t*)PAGE_DIR_MAP;
+        if ((pd[pdindex] & PD_PRES) == 0)
+                init_page_table(pdindex, 0);
+
+        uintptr_t *pt = (uintptr_t*)(PAGE_TAB_MAP + (pdindex << 12));
+        pt[ptindex] = paddr | PD_PRES | flags;
+        invlpg((void*)vaddr);
+}
+
+void unmap_page(uintptr_t vaddr) {
+        uintptr_t pdindex = GET_PDX(vaddr);
+        uintptr_t ptindex = GET_PTX(vaddr);
+
+        uintptr_t *pd = (uintptr_t*)PAGE_DIR_MAP;
+        if ((pd[pdindex] & PD_PRES) == 0)
+                return;
+
+        uintptr_t *pt = (uintptr_t*)(PAGE_TAB_MAP + (pdindex << 12));
+        pt[ptindex] = 0;
+        invlpg((void*)vaddr);
+}
+
+void page_fault_handler(struct isr_frame *frame) {
+        uintptr_t fault_addr;
+        __asm__ volatile("movl %%cr2, %0" : "=r"(fault_addr));
+
+        kprintf("Faulting address: %x\n", fault_addr);
+        panic("Page fault not operational");
+        switch (frame->isr_err) {
+                case 0:
+                        //map_page((uintptr_t*)GET_VADDR(frame->cr3), pfa_alloc(), fault_addr, PD_PRES);
+                        break;
+                case 1:
+                        panic("Kernel process caused protection fault on read\n");
+                        break;
+                case 2:
+                        //map_page((uintptr_t*)GET_VADDR(frame->cr3), pfa_alloc(), fault_addr, PD_PRES | PD_RW);
+                        break;
+                case 3:
+                        panic("Kernel process caused protection fault on write\n");
+                        break;
+                case 4:
+                        //map_page((uintptr_t*)GET_VADDR(frame->cr3), pfa_alloc(), fault_addr, PD_PRES | PD_USR);
+                        break;
+                case 5:
+                        // TODO: instead of panicking, kill process
+                        panic("User process caused protection fault on read\n");
+                        break;
+                case 6:
+                        //map_page((uintptr_t*)GET_VADDR(frame->cr3), pfa_alloc(), fault_addr, PD_PRES | PD_RW | PD_USR);
+                        break;
+                case 7:
+                        // TODO: see case 101
+                        panic("USER process caused protection fault on write\n");
+                        break;
+                default:
+                        kprintf("Unknown paging error occured on address %x\n", fault_addr);
+                        panic("Paging error");
+                        break;
+        }
+}