Create pmm.c

Add implementation for the physical memory manager pmm

kernel/fat16.c

@@ -1,107 +0,0 @@
-#include "fat16.h"
-#include "ata.h"   // Use ata_read_sector and ata_write_sector
-#include "print.h" // For debugging
-#include <string.h> // For string manipulation
-
-// Global variables
-static fat16_boot_sector_t boot_sector;
-static uint32_t root_dir_sector = FAT16_ROOT_DIR_SECTOR;
-
-// Read a sector from the disk using ATA
-bool read_sector(uint32_t lba, uint8_t* buffer) {
-    return ata_read_sector(lba, buffer);
-}
-
-// Write a sector to the disk using ATA
-bool write_sector(uint32_t lba, const uint8_t* buffer) {
-    return ata_write_sector(lba, buffer);
-}
-
-// Parse the boot sector to retrieve basic file system info
-bool parse_fat16_boot_sector(void) {
-    uint8_t sector_buffer[FAT16_SECTOR_SIZE];
-
-    // Read the boot sector
-    if (!read_sector(FAT16_BOOT_SECTOR, sector_buffer)) {
-        print_string("[FAT16] Failed to read boot sector\n");
-        return false;
-    }
-
-    // Cast to boot sector structure
-    memcpy(&boot_sector, sector_buffer, sizeof(fat16_boot_sector_t));
-
-    // Check for FAT16 signature
-    if (boot_sector.oem_name[0] != 'F' || boot_sector.oem_name[1] != 'A' || boot_sector.oem_name[2] != 'T') {
-        print_string("[FAT16] Invalid FAT16 boot sector signature\n");
-        return false;
-    }
-
-    print_string("[FAT16] FAT16 boot sector parsed successfully\n");
-    return true;
-}
-
-// Parse the root directory
-bool parse_fat16_root_dir(void) {
-    uint8_t sector_buffer[FAT16_SECTOR_SIZE];
-
-    for (int i = 0; i < (boot_sector.max_root_entries / (FAT16_SECTOR_SIZE / sizeof(fat16_dir_entry_t))); i++) {
-        // Read root directory sector
-        if (!read_sector(root_dir_sector + i, sector_buffer)) {
-            print_string("[FAT16] Failed to read root directory sector\n");
-            return false;
-        }
-
-        // Parse the root directory entries
-        for (int j = 0; j < (FAT16_SECTOR_SIZE / sizeof(fat16_dir_entry_t)); j++) {
-            fat16_dir_entry_t* entry = (fat16_dir_entry_t*)&sector_buffer[j * sizeof(fat16_dir_entry_t)];
-            if (entry->name[0] == 0x00) {
-                // End of directory entries
-                return true;
-            }
-            if (entry->name[0] != 0xE5) {
-                // Print file name (8.3 format)
-                char filename[12];
-                strncpy(filename, (char*)entry->name, 8);
-                filename[8] = '.';
-                strncpy(&filename[9], (char*)entry->ext, 3);
-                filename[11] = '\0';
-                print_string(filename);
-                print_string("\n");
-            }
-        }
-    }
-    return true;
-}
-
-// Read a specific directory entry from the FAT16 root directory
-bool read_fat16_entry(uint16_t entry_index, fat16_dir_entry_t* entry) {
-    uint8_t sector_buffer[FAT16_SECTOR_SIZE];
-    uint32_t sector_num = FAT16_ROOT_DIR_SECTOR + (entry_index / (FAT16_SECTOR_SIZE / sizeof(fat16_dir_entry_t)));
-    uint16_t entry_offset = entry_index % (FAT16_SECTOR_SIZE / sizeof(fat16_dir_entry_t));
-
-    // Read the sector
-    if (!read_sector(sector_num, sector_buffer)) {
-        print_string("[FAT16] Failed to read root directory sector\n");
-        return false;
-    }
-
-    // Get the entry
-    memcpy(entry, &sector_buffer[entry_offset * sizeof(fat16_dir_entry_t)], sizeof(fat16_dir_entry_t));
-    return true;
-}
-
-// Mount the FAT16 filesystem
-bool mount_fat16(void) {
-    // Parse the boot sector
-    if (!parse_fat16_boot_sector()) {
-        return false;
-    }
-
-    // Parse the root directory
-    if (!parse_fat16_root_dir()) {
-        return false;
-    }
-
-    print_string("[FAT16] Filesystem mounted successfully\n");
-    return true;
-}

kernel/fat16.h

@@ -1,60 +0,0 @@
-#ifndef FAT16_H
-#define FAT16_H
-
-#include <stdint.h>
-#include <stdbool.h>
-
-/* FAT16 Constants */
-#define FAT16_SECTOR_SIZE        512
-#define FAT16_CLUSTER_SIZE       1
-#define FAT16_MAX_FILENAME_LEN   11   // 8.3 format
-#define FAT16_ROOT_DIR_ENTRIES   224  // Fat16 root directory entries (typically 512 bytes per entry)
-
-#define FAT16_BOOT_SECTOR        0
-#define FAT16_FAT1_SECTOR        1
-#define FAT16_FAT2_SECTOR        2
-#define FAT16_ROOT_DIR_SECTOR    19  // First sector of root directory
-
-/* Boot Sector */
-typedef struct {
-    uint8_t jmp[3];               // Jump instruction to code
-    uint8_t oem_name[8];          // OEM Name
-    uint16_t bytes_per_sector;    // Bytes per sector (512)
-    uint8_t sectors_per_cluster;  // Sectors per cluster
-    uint16_t reserved_sectors;    // Reserved sectors
-    uint8_t num_fats;             // Number of FAT tables
-    uint16_t max_root_entries;    // Max number of root directory entries
-    uint16_t total_sectors_16;    // Total sectors in FAT16
-    uint8_t media_type;           // Media type (0xF8 = fixed drive)
-    uint16_t sectors_per_fat;    // Sectors per FAT table
-    uint16_t sectors_per_track;  // Sectors per track (for CHS addressing)
-    uint16_t num_heads;          // Number of heads (for CHS addressing)
-    uint32_t hidden_sectors;     // Hidden sectors (before the partition)
-    uint32_t total_sectors_32;   // Total sectors in FAT16 (extended)
-} __attribute__((packed)) fat16_boot_sector_t;
-
-/* FAT16 Directory Entry */
-typedef struct {
-    uint8_t name[8];   // File name (8 chars)
-    uint8_t ext[3];    // File extension (3 chars)
-    uint8_t attributes; // File attributes (e.g., directory, read-only)
-    uint8_t reserved;   // Reserved
-    uint8_t creation_time[2]; // Creation time
-    uint8_t creation_date[2]; // Creation date
-    uint8_t last_access_date[2]; // Last access date
-    uint8_t first_cluster_high[2]; // High part of first cluster number
-    uint8_t last_mod_time[2];  // Last modification time
-    uint8_t last_mod_date[2];  // Last modification date
-    uint8_t first_cluster_low[2];  // Low part of first cluster number
-    uint32_t file_size;         // File size in bytes
-} __attribute__((packed)) fat16_dir_entry_t;
-
-/* Function Prototypes */
-bool mount_fat16(void);
-bool read_sector(uint32_t lba, uint8_t* buffer);
-bool write_sector(uint32_t lba, const uint8_t* buffer);
-bool parse_fat16_boot_sector(void);
-bool parse_fat16_root_dir(void);
-bool read_fat16_entry(uint16_t entry_index, fat16_dir_entry_t* entry);
-
-#endif // FAT16_H

kernel/pmm.h

@@ -0,0 +1,21 @@
+#ifndef PMM_H
+#define PMM_H
+
+#include <stdint.h>
+#include <stddef.h>
+#include "memmap.h"
+#include "paging.h" // For PAGE_SIZE
+
+#define BLOCKS_PER_BYTE 8
+
+void pmm_init(memory_map_entry_t* mmap, uint32_t mmap_size, uintptr_t bitmap_addr);
+void pmm_mark_used(uintptr_t addr);
+void pmm_mark_free(uintptr_t addr);
+
+void* pmm_alloc_block();
+void  pmm_free_block(void* addr);
+
+uint32_t pmm_get_used_block_count();
+uint32_t pmm_get_free_block_count();
+
+#endif

pmm.c

@@ -0,0 +1,102 @@
+#include "pmm.h"
+#include "memory.h" // For memset
+
+static uint32_t* pmm_bitmap = NULL;
+static uint32_t  max_blocks = 0;
+static uint32_t  used_blocks = 0;
+
+// Internal bitmap helpers
+static inline void bitmap_set(uint32_t bit) {
+    pmm_bitmap[bit / 32] |= (1 << (bit % 32));
+}
+
+static inline void bitmap_unset(uint32_t bit) {
+    pmm_bitmap[bit / 32] &= ~(1 << (bit % 32));
+}
+
+static inline int bitmap_test(uint32_t bit) {
+    return pmm_bitmap[bit / 32] & (1 << (bit % 32));
+}
+
+void pmm_init(memory_map_entry_t* mmap, uint32_t mmap_size, uintptr_t bitmap_addr) {
+    // 1. Calculate total memory from mmap to find max_blocks
+    uint64_t total_mem = 0;
+    for (uint32_t i = 0; i < mmap_size; i++) {
+        if (mmap[i].type == 1) { // Available RAM
+            total_mem = mmap[i].base_addr + mmap[i].length;
+        }
+    }
+
+    max_blocks = (uint32_t)(total_mem / PAGE_SIZE);
+    used_blocks = max_blocks; 
+    pmm_bitmap = (uint32_t*)bitmap_addr;
+
+    // 2. Default all memory to "Reserved" (1s)
+    memset(pmm_bitmap, 0xFF, max_blocks / BLOCKS_PER_BYTE);
+
+    // 3. Mark only the regions reported as Type 1 (Available) as free (0s)
+    for (uint32_t i = 0; i < mmap_size; i++) {
+        if (mmap[i].type == 1) {
+            uint32_t start_block = (uint32_t)(mmap[i].base_addr / PAGE_SIZE);
+            uint32_t block_count = (uint32_t)(mmap[i].length / PAGE_SIZE);
+            
+            for (uint32_t j = 0; j < block_count; j++) {
+                bitmap_unset(start_block + j);
+                used_blocks--;
+            }
+        }
+    }
+
+    // 4. Critical: Re-protect the first 1MB (BIOS/VGA/Real Mode stuff)
+    for (uint32_t i = 0; i < (1024 * 1024) / PAGE_SIZE; i++) {
+        pmm_mark_used(i * PAGE_SIZE);
+    }
+
+    // 5. Critical: Re-protect the Kernel + Page Tables
+    // Since your paging tables are at 0x200000 and linker at 1MB, 
+    // mark everything from 0x100000 to roughly 0x400000 as used for safety.
+    for (uint32_t i = 0x100000 / PAGE_SIZE; i < 0x400000 / PAGE_SIZE; i++) {
+        pmm_mark_used(i * PAGE_SIZE);
+    }
+    
+    // 6. Protect the bitmap itself
+    uint32_t bitmap_size_blocks = (max_blocks / BLOCKS_PER_BYTE) / PAGE_SIZE + 1;
+    for(uint32_t i = 0; i < bitmap_size_blocks; i++) {
+        pmm_mark_used(bitmap_addr + (i * PAGE_SIZE));
+    }
+}
+
+void pmm_mark_used(uintptr_t addr) {
+    uint32_t block = addr / PAGE_SIZE;
+    if (!bitmap_test(block)) {
+        bitmap_set(block);
+        used_blocks++;
+    }
+}
+
+void pmm_mark_free(uintptr_t addr) {
+    uint32_t block = addr / PAGE_SIZE;
+    if (bitmap_test(block)) {
+        bitmap_unset(block);
+        used_blocks--;
+    }
+}
+
+void* pmm_alloc_block() {
+    for (uint32_t i = 0; i < max_blocks / 32; i++) {
+        if (pmm_bitmap[i] != 0xFFFFFFFF) {
+            for (int j = 0; j < 32; j++) {
+                if (!bitmap_test(i * 32 + j)) {
+                    uint32_t addr = (i * 32 + j) * PAGE_SIZE;
+                    pmm_mark_used(addr);
+                    return (void*)addr;
+                }
+            }
+        }
+    }
+    return NULL; // OOM
+}
+
+void pmm_free_block(void* addr) {
+    pmm_mark_free((uintptr_t)addr);
+}