Added MBR Support, FAT16 support and bug fixes.

Author: pradosh-arduino

Makefile

@@ -58,18 +58,21 @@ tarball:
 # QEMU targets
 # -----------------------------
 QEMU_COMMON = \
-	-vga std \
-	-debugcon stdio \
-	-serial file:serial.log \
-	-audiodev pa,id=speaker \
-	-device rtl8139,netdev=eth0 \
-	-netdev user,hostfwd=tcp::5555-:22,id=eth0 \
-	-cdrom $(ISO_FILE) \
-	-drive if=none,file=disk.txtimg,id=disk \
-	-device ahci,id=ahci \
-	-device ide-hd,drive=disk,bus=ahci.0 \
-	-rtc base=localtime,clock=host \
-	-m 512
+    -vga std \
+    -debugcon stdio \
+    -serial file:serial.log \
+	-boot menu=on \
+    -audiodev pa,id=speaker \
+    -device rtl8139,netdev=eth0 \
+    -netdev user,hostfwd=tcp::5555-:22,id=eth0 \
+    -device usb-ehci,id=ehci \
+    -drive if=none,format=raw,file=$(ISO_FILE),id=usbdisk,index=0\
+    -device usb-storage,drive=usbdisk \
+    -drive if=none,format=raw,file=disk.txtimg,id=disk,index=1 \
+    -device ahci,id=ahci \
+    -device ide-hd,drive=disk,bus=ahci.0 \
+    -rtc base=localtime,clock=host \
+    -m 512
 
 run-x86-hdd:
 	@qemu-system-x86_64 $(QEMU_COMMON)

disk.txtimg

@@ -24,6 +24,8 @@
 #define SECTOR_SIZE         512
 
 #define ATA_CMD_WRITE_DMA_EXT 0x35
+#define ATA_CMD_IDENTIFY 0xEC
+
 
 /**
  * @brief AHCI device signatures.
@@ -130,6 +132,27 @@ typedef volatile struct {
     ahci_port_t ports[32];       /* array of port structures (0x100.. ) */
 } ahci_hba_mem_t;
 
+typedef struct {
+    uint64_t total_sectors;
+    int present;
+} ahci_disk_info_t;
+
+extern ahci_disk_info_t ahci_disks[32];
+
+typedef struct {
+    int disk;
+    uint32_t lba_start;
+    uint32_t sectors;
+    uint8_t type;
+} block_part_t;
+
+// For block devics
+typedef struct {
+    int port;
+    uint64_t sectors;
+
+    block_part_t partitions[4];
+} block_disk_t;
 
 /**
  * @brief Global AHCI controller pointer.

source/includes/ahci.h

@@ -22,8 +22,9 @@ typedef uint8_t int8;
 typedef const char* cstring;
 typedef char* string;
 
-#define MiB *1024*1024
-#define KiB *1024
+#define GiB *1024*1024*1024ULL
+#define MiB *1024*1024ULL
+#define KiB *1024ULL
 
 #define yes true
 #define no false

source/includes/basics.h

@@ -32,5 +32,6 @@ int cmd_fwfetch(int argc, char** argv);
 int cmd_help(int argc, char** argv);
 int cmd_lspci(int argc, char** argv);
 int cmd_clear(int argc, char** argv);
+int cmd_lsblk(int argc, char** argv);
 
 #endif

source/includes/commands/commands.h

@@ -11,10 +11,6 @@
 #define GPT_PART_ATTRIB_USED_BY_OS      0b10
 #define GPT_ENTRIES_SIZE                (512*31)/sizeof(GPT_PartitionEntry)
 
-#if defined(__cplusplus)
-extern "C" {
-#endif
-
 extern uint8_t GPT_EFI_SIGNATURE[]; // it's just "EFI PART"
 
 struct GPT_PartTableHeader{
@@ -53,8 +49,4 @@ struct GPT_END{
     GPT_PartTableHeader PartitionTableHeaderMirror; // Has to be same as at the start
 } __attribute__((packed)) ;
 
-#if defined(__cplusplus)
-} // extern "C"
-#endif
-
 #endif

source/includes/disk/gpt.h

@@ -1,48 +1,32 @@
-/* 
+/**
+ * @file mbr.h
+ * @author Pradosh (pradoshgame@gmail.com)
+ * @brief  The header to read the LBA0 and check whether the disk is MBR. 
+ * @version 0.1
+ * @date 2025-12-28
  * 
- * Master Boot Record (partition table)
+ * @copyright Copyright (c) Pradosh 2025
  * 
  */
-#ifndef __MBR_H
-#define __MBR_H
-#include <stdint.h>
-#include <stddef.h>
+#ifndef MBR_H
+#define MBR_H
+#include <basics.h>
+#include <ahci.h>
 
 #define MBR_PART_BOOTABLE   0x80
-#define MBR_VALID_MBR       0xaa55
 
-#if defined( __cplusplus )
-extern "C" {
-#endif
+extern block_disk_t mbr_disks[10];
 
-struct MBR_Partition{
-    uint8_t              Attributes;
+typedef struct {
+    uint8_t boot_flag;
+    uint8_t chs_start[3];
+    uint8_t partition_type;
+    uint8_t chs_end[3];
+    uint32_t lba_start;
+    uint32_t num_sectors;
+} __attribute__((packed)) mbr_partition_t;
 
-    uint8_t              StartHead;
-    uint8_t              StartSector : 6;
-    uint16_t             StartCylinder : 10;
-
-    uint8_t              SystemID;
-
-    uint8_t              EndHead;
-    uint8_t              EndSector : 6;
-    uint16_t             EndCylinder : 10;
-
-    uint32_t             LBA_Start;
-    uint32_t             SectorCount;
-} __attribute__((packed)) ;
-
-struct MBR{
-    uint8_t              Bootloader[440];
-    uint32_t             UniqueDiskID;
-    uint16_t             Reserved0;
-    MBR_Partition   Partitions[4];
-    uint16_t             ValidationSignature;
-} __attribute__((packed)) ;
-
-
-#if defined( __cplusplus )
-}
-#endif
+void check_mbr(int portno);
+void parse_mbr_partitions(int8* mbr, int portno);
 
 #endif

source/includes/disk/mbr.h

@@ -0,0 +1,87 @@
+/**
+ * @file fat16.h
+ * @author Pradosh (pradoshgame@gmail.com)
+ * @brief The header file for reading in FAT16 file system
+ * @version 0.1
+ * @date 2025-12-28
+ * 
+ * @copyright Copyright (c) Pradosh 2025
+ * 
+ */
+
+#ifndef FAT16_H
+#define FAT16_H
+
+#include <basics.h>
+#include <graphics.h>
+
+typedef struct {
+    uint8_t  jmp[3];
+    uint8_t  oem[8];
+    uint16_t bytes_per_sector;
+    uint8_t  sectors_per_cluster;
+    uint16_t reserved_sectors;
+    uint8_t  num_fats;
+    uint16_t max_root_dir_entries;
+    uint16_t total_sectors_short; // if zero, use total_sectors_long
+    uint8_t  media_descriptor;
+    uint16_t sectors_per_fat;
+    uint16_t sectors_per_track;
+    uint16_t num_heads;
+    uint32_t hidden_sectors;
+    uint32_t total_sectors_long;
+    // We ignore the rest for now
+} __attribute__((packed)) fat16_boot_sector_t;
+
+typedef struct {
+    char     name[8];
+    char     ext[3];
+    uint8_t  attr;
+    uint8_t  reserved;
+    uint8_t  creation_time_tenths;
+    uint16_t creation_time;
+    uint16_t creation_date;
+    uint16_t last_access_date;
+    uint16_t ignore;       // high word of first cluster (FAT32 only)
+    uint16_t last_mod_time;
+    uint16_t last_mod_date;
+    uint16_t first_cluster;
+    uint32_t filesize;
+} __attribute__((packed)) fat16_dir_entry_t;
+
+typedef struct {
+    int portno;
+    uint32_t partition_lba;
+
+    fat16_boot_sector_t bs;
+
+    uint32_t fat_start;
+    uint32_t root_dir_start;
+    uint32_t root_dir_sectors;
+    uint32_t data_start;
+} fat16_fs_t;
+
+typedef struct {
+    fat16_fs_t* fs;
+    fat16_dir_entry_t entry;
+    uint32_t pos;
+    uint16_t cluster;
+} fat16_file_t;
+
+int detect_fat_type(int8* buf);
+int fat16_mount(int portno, uint32_t partition_lba, fat16_fs_t* fs) ;
+uint16_t fat16_read_fat_fs(fat16_fs_t* fs, uint16_t cluster);
+void fat16_list_root(fat16_fs_t* fs);
+int fat16_find_path(fat16_fs_t* fs, const char* path, fat16_dir_entry_t* out);
+int fat16_match_name(fat16_dir_entry_t* e, const char* name);
+int fat16_find_in_dir(fat16_fs_t* fs, uint16_t current_cluster, const char* name, fat16_dir_entry_t* out);
+void fat16_list_dir_cluster(fat16_fs_t* fs, uint16_t start_cluster);
+void fat16_format_name(const char* input, char out[11]);
+int fat16_find_file(fat16_fs_t* fs, const char* name, fat16_dir_entry_t* out);
+void fat16_read_file(fat16_fs_t* fs, fat16_dir_entry_t* file);
+int fat16_open(fat16_fs_t* fs, const char* path, fat16_file_t* f);
+int fat16_read(fat16_file_t* f, uint8_t* out, uint32_t size);
+int fat16_write(fat16_file_t* f, const uint8_t* data, uint32_t size);
+void fat16_close(fat16_file_t* f);
+
+#endif

source/includes/filesystems/fat16.h

@@ -12,6 +12,7 @@
 #include <heap.h>
 
 ahci_hba_mem_t* global_ahci_ctrl;
+ahci_disk_info_t ahci_disks[32];
 
 void detect_ahci_devices(ahci_hba_mem_t* ahci_ctrl) {
     global_ahci_ctrl = ahci_ctrl;
@@ -33,6 +34,8 @@ void detect_ahci_devices(ahci_hba_mem_t* ahci_ctrl) {
 
         uint32_t sig = port->sig;
 
+        printf("port->sig = 0x%x", port->sig);
+
         switch (sig) {
             case sata_disk:
                 printf("[AHCI] SATA Disk detected on port %d", i);
@@ -58,17 +61,28 @@ void detect_ahci_devices(ahci_hba_mem_t* ahci_ctrl) {
 void handle_sata_disk(int portno) {
     ahci_init_port(portno);
 
-    uint8_t* buf = kmalloc_aligned(512, 512);
-    memset(buf, 0, 512);
+    int16* id = kmalloc_aligned(512, 4096);
+
+    if (!id) {
+        error("[AHCI] Allocation failed!", __FILE__);
+        return;
+    }
 
-    if (ahci_read_sector(portno, 0, buf, 1) != 0) {
-        printf("[AHCI] Read LBA failed on port %d\n", portno);
+    if (ahci_identify(portno, id) != 0) {
+        printf("[AHCI] IDENTIFY failed on port %d", portno);
         return;
     }
 
-    for (int i = 0; i < 32; i++) printfnoln("%c", buf[i]);
+    uint64_t sectors =
+            ((uint64_t)id[103] << 48) |
+            ((uint64_t)id[102] << 32) |
+            ((uint64_t)id[101] << 16) |
+            ((uint64_t)id[100]);
+
+    ahci_disks[portno].total_sectors = sectors;
+    ahci_disks[portno].present = 1;
 
-    print("\n");
+    check_mbr(portno);
 
     // char* msg = "FROSTWING WAS HERE";
     // memset(buf, 0, 512);
@@ -77,13 +91,13 @@ void handle_sata_disk(int portno) {
     // uint64_t write_lba = 2; // or 10 for testing
 
     // if (ahci_write_sector(portno, 0, buf, 1) != 0) {
-    //     printf("[AHCI] Write LBA failed\n");
+    //     printf("[AHCI] Write LBA failed");
     //     return;
     // }
 
     // memset(buf, 0, 512);
     // if (ahci_read_sector(portno, 0, buf, 1) != 0) {
-    //     printf("[AHCI] Read LBA failed\n");
+    //     printf("[AHCI] Read LBA failed");
     //     return;
     // }
 
@@ -240,3 +254,54 @@ int ahci_write_sector(int portno, uint64_t lba, void* buffer, uint32_t count) {
     port->is = 0xFFFFFFFF;
     return 0;
 }
+
+int ahci_identify(int portno, void* buffer) {
+    ahci_port_t* port = &global_ahci_ctrl->ports[portno];
+    ahci_port_mem_t* mem = &port_mem[portno];
+
+    // Wait until port is ready
+    while (port->tfd & (0x80 | 0x08)); // BSY | DRQ
+
+    int slot = ahci_find_slot(port);
+    if (slot == -1) return -1;
+
+    ahci_cmd_header_t* hdr = &mem->cmd_list[slot];
+    memset(hdr, 0, sizeof(*hdr));
+    hdr->flags = 5; 
+    hdr->prdtl = 1; // one PRDT entry
+    hdr->ctba = (uint32_t)(uintptr_t)mem->cmd_tables[slot];
+    hdr->ctbau = 0;
+
+
+    ahci_cmd_table_t* tbl = mem->cmd_tables[slot];
+    memset(tbl->cfis, 0, 64);
+    memset(tbl->prdt, 0, sizeof(tbl->prdt));
+
+
+    tbl->prdt[0].dba  = (uint32_t)(uintptr_t)buffer;
+    tbl->prdt[0].dbau = 0;
+    tbl->prdt[0].dbc  = (512 - 1) | (1 << 31); // 512 bytes, IOC
+
+    uint8_t* cfis = tbl->cfis;
+    cfis[0] = 0x27;        // Host to device
+    cfis[1] = 1 << 7;      // Command
+    cfis[2] = ATA_CMD_IDENTIFY; // IDENTIFY DEVICE
+    cfis[7] = 0;           // Features = 0
+    cfis[8] = 0; cfis[9] = 0; cfis[10] = 0; // LBA = 0
+
+    port->serr = 0xFFFFFFFF;
+    port->is   = 0xFFFFFFFF;
+
+    port->ci = 1 << slot;
+
+    // Wait for completion
+    while (port->ci & (1 << slot)) {
+        if (port->tfd & (0x01 | 0x20)) { // ERR | DF
+            port->is = 0xFFFFFFFF;
+            return -2;
+        }
+    }
+
+    port->is = 0xFFFFFFFF;
+    return 0;
+}