feat: start of paging setup

kernel/mem/paging.c

@@ -2,58 +2,80 @@
 // Created by rick on 21-02-21.
 //
 
-#include <attributes.h>
-#include <stdbool.h>
 #include <sys/types.h>
+#include <attributes.h>
 
 #include <myke/mem/paging.h>
+#include <sys/param.h>
 
-#define TABLE_ADDR_MASK 0xFFFFF000
-#define DIRECTORY_SIZE 1024
+#define PAGING_DIR_INDEX(virt) ((virt) >> 22)
+#define PAGING_TABLE_INDEX(virt) ((virt) >> 12 & 0x03FF)
 
-const uint32_t x = TABLE_ADDR_MASK;
-typedef struct {
-    union {
-        struct {
-            bool present: 1;
-            bool read_write: 1;
-            bool user_mode: 1;
-            bool write_through: 1;
-            bool cache_disabled: 1;
-            bool accessed: 1;
-            char ignored: 1;
-            bool page_size: 1;
-            bool global: 1; // ignored
-            uint8_t avail: 3;
-        } att_packed;
-        uint32_t addr;
-    };
-} att_packed page_directory_entry;
+#define KERNEL_OFFSET 0xC0000000
 
-typedef struct {
-    union {
-        struct {
-            bool present: 1;
-            bool read_write: 1;
-            bool user_supervisor: 1;
-            bool write_through: 1;
-            bool cache_disabled: 1;
-            bool accessed: 1;
-            bool dirty: 1;
-            char ignored: 1;
-            bool global: 1;
-            uint8_t available: 3;
-        } att_packed;
-        uint32_t addr;
-    };
-} att_packed page_table_entry;
+// One page table, only 4M
+#define PAGING_STATE_EARLY 0
+#define PAGING_STATE_FULL 60
 
-page_directory_entry page_directory[DIRECTORY_SIZE] att_aligned(4096);
+page_directory_entry att_aligned(4096) kernel_page_directory[DIRECTORY_SIZE] = {0};
 
-void page_pre_init() {
-    for (int i = 0; i < DIRECTORY_SIZE; ++i) {
-        page_directory[i].read_write = true;
-        page_directory[i].user_mode = false;
-        page_directory[i].present = false;
+int paging_state = PAGING_STATE_EARLY;
+
+void paging_load_directory(uintptr_t physical_address) {
+    asm volatile("mov %%eax, %%cr3" : : "a" (physical_address));
+}
+
+uintptr_t paging_get_current_directory_physical() {
+    uintptr_t directory_address;
+    asm volatile("mov %%cr3, %%eax" : "=a" (directory_address));
+    return directory_address;
+}
+
+page_directory_entry *paging_get_current() {
+    return kernel_page_directory;
+}
+
+int paging_map_4m(uintptr_t physical_address, uintptr_t virtual_address, int count, int mode) {
+    if (virtual_address & ~PAGING_MASK_4M || physical_address & PAGING_MASK_4M) {
+        // address not 4M aligned
+        return PAGING_RESULT_ALIGN;
     }
+    page_directory_entry *dir = paging_get_current();
+    for (int i = 0; i < count; ++i) {
+        page_directory_entry current_val = dir[PAGING_DIR_INDEX(virtual_address) + i];
+        if (current_val & DIRECTORY_PRESENT_MASK) {
+            return PAGING_RESULT_INUSE;
+        }
+    }
+    page_directory_entry mask = DIRECTORY_PAGE_SIZE_MASK;
+    if (mode & PAGING_MODE_RW) {
+        mask |= DIRECTORY_RW_MASK;
+    }
+    if (mode & PAGING_MODE_US) {
+        mask |= DIRECTORY_US_MASK;
+    }
+    for (int i = 0; i < count; ++i) {
+        dir[PAGING_DIR_INDEX(virtual_address) + i] = physical_address & mask;
+    }
+    paging_load_directory((uintptr_t) dir);
+    return PAGING_RESULT_OK;
+}
+
+int paging_map_memory(uintptr_t physical_address, uintptr_t virtual_address, int count, int mode) {
+    if (mode & PAGING_MODE_4M) {
+        return paging_map_4m(physical_address, virtual_address, count, mode);
+    }
+    if (paging_state < PAGING_STATE_FULL) {
+        // can't allocate 4K pages yet
+        if ((virtual_address & ~PAGING_MASK_4M) != (physical_address & ~PAGING_MASK_4M)) {
+            return PAGING_RESULT_ERR; // not in same pos in 4M page
+        }
+        int table_index = PAGING_TABLE_INDEX(virtual_address);
+        int pages = DIV_ROUND_UP(table_index + count, 1024);
+        return paging_map_4m(physical_address & PAGING_MASK_4M,
+                             virtual_address & PAGING_MASK_4M,
+                             pages,
+                             mode | PAGING_MODE_4M);
+    }
+    return PAGING_RESULT_ERR;
 }