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FAT16 structures read from disk using ATA. 

The proper reading of folders and files is not yet implemented. Although
it is close.
dev
Nigel Barink 2021-12-24 21:31:10 +01:00
parent 72008b0a7a
commit fb2a19e11d
4 changed files with 119 additions and 18 deletions
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21
src/kernel/filesytems/FAT32/BiosParameterBlock.h Normal file
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@ -0,0 +1,21 @@
#pragma once
#include <stdint.h>
#include "./ExtendBootRecord.h"
struct BiosParameterBlock {
uint8_t BootLoaderCodeSection [3];
uint8_t OEM_id [8];
uint16_t BytesPerSector ; // I suspect would be 512
uint8_t SectorsPerCluster ;
uint16_t ReservedSectors;
uint8_t NumberOfFileAllocationTables; // Probably equals 2
uint16_t NumberOfDirectoryEntries; // Root directory must contain entire sectors
uint16_t TotalSectorsInLogicalVolume ; // 0 means >65535 sectors in volume , actual count can be found in LargeSectorCount
uint8_t MediaDescriptor ; // Indication the media descriptor type
uint16_t NumberOfSectorsPerFAT;// only in FAT12 / FAT 16
uint16_t NumberOfSectorsPerTrack;
uint16_t NumberOfHeadsOnMedia;
uint32_t NumberOfHiddenSectors;
uint32_t LargeSectorCount;
ExtendedBootRecord_FAT16 ebpb;
}__attribute__((packed));

32
src/kernel/filesytems/FAT32/ExtendBootRecord.h Normal file
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@ -0,0 +1,32 @@
#pragma once
#include <stdint.h>
struct ExtendedBootRecord_FAT16{
uint8_t DriveNumber;
uint8_t Reserved;
uint8_t Signature;
const uint32_t VOLUME_ID_SERIAL_NUMBER;
uint8_t volume_label [11];
uint8_t Identifier_string [8];
uint8_t bootCode [448];
uint16_t partitionSignature;
}__attribute__((packed));
struct ExtendedBootRecord_FAT32{
uint32_t SectorsPerFAT;
uint16_t Flags;
const uint16_t FAT_VERSION_NUMBER;
uint32_t rootDirectory_clusterNumber;// Often set to 2;
uint16_t FSInfo_SectorNumber;
uint16_t backup_bpb_sectorNumber;
uint8_t Reserved [12];
uint8_t DriveNumber;
uint8_t Reserved2;
uint8_t Signature; // must be 0x28 or 0x29
uint32_t VOLUME_ID_SERIAL;
uint8_t volume_label[11];
uint8_t SystemIdentifierString [8]; // ALWAYS "FAT32 " but spec says do not trust
uint8_t BootCode [420]; // NICE
uint16_t PartitionSignature; // 0xAA55
}__attribute__((packed));

76
src/kernel/kernel.cpp
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@ -44,40 +44,84 @@ extern "C" void kernel_main (void);
init_serial();
print_serial("Serial port initialized!");
RSDPTR* rsd = FindRSD();
RSDT* rsd_table = getRSDT(rsd);
// Enumerate the PCI bus
PCI_Enumerate();
TestIDEController();
TestIDEController();
int devNumber = 0 ;
for ( auto device : ide_devices){
if (!device.Reserved)
continue;
printf("Device %d\n" , devNumber);
printf (" Device on Channel: (0x%x) %s\n" ,device.Channel, device.Channel == 0 ? "Primary" : "Secondary");
printf (" Device drive:(0x%x) %s\n" , device.Drive, device.Drive? "Slave" : "Master");
printf (" Device Type:(0x%x) %s\n" , device.Type, device.Type ? "ATAPI" : "ATA");
devNumber ++;
}
// ATAPI_DEVICE::isPacketDevice();
enum BUS_PORT {
Primary= 0x1f0,
Secondary = 0x170
};
ATAPI_DEVICE::Identify(ATA_SECONDARY, DEVICE_DRIVE::MASTER);
ATA_DEVICE::Identify((uint16_t) BUS_PORT::Primary, DEVICE_DRIVE::MASTER);
const int C = 0;
const int H = 0;
const int HPC = 16;
const int SPT = 63;
int S = 1;
uint32_t LBA = (C*HPC+H) * SPT + (S-1);
printf("LBA: %d\n" , LBA);
uint16_t buffer [256];
ATA_DEVICE::Read(BUS_PORT::Primary, DEVICE_DRIVE::MASTER, LBA, buffer);
MBR* mbr = (MBR*) buffer;
printf("BootSector: 0x%x\n", mbr->ValidBootsector );
for( int i = 0 ; i < 4 ; i ++){
PartitionTableEntry PT = mbr->TableEntries[i];
printf("Partition %d [ %d sectors, PartitionType: %x, 0x%x, \nLBA Start: 0x%x ]\n" ,
i, PT.Number_sectors_inPartition, PT.PartitionType, mbr->uniqueID, PT.LBA_partition_start );
}
// Find the super block
uint16_t superBlock[256];
ATA_DEVICE::Read(BUS_PORT::Primary, DEVICE_DRIVE::MASTER, mbr->TableEntries[0].LBA_partition_start, superBlock);
BiosParameterBlock* bpb = (BiosParameterBlock*) superBlock;
printf("\nBPB: Bytes per Sector %d\n", bpb->BytesPerSector );
printf("OEM ID: %s\n", bpb->OEM_id);
printf("Bytes per sector: %d\n", bpb->BytesPerSector);
printf("Sectors per cluster: %d\n", bpb->SectorsPerCluster);
printf("Reserved sectors: %d\n", bpb->ReservedSectors);
printf("Number of FAT: %d\n", bpb->NumberOfFileAllocationTables);
printf("Number of Dir entries: %d\n", bpb->NumberOfDirectoryEntries);
printf("Total Sectors in volume: %d\n", bpb->TotalSectorsInLogicalVolume);
printf("Sectors per FAT: %d\n", bpb->NumberOfSectorsPerFAT);
uint32_t PartitionAddress = mbr->TableEntries[0].LBA_partition_start *512 ;
uint32_t RootDirAddress = PartitionAddress + ((bpb->ReservedSectors + bpb->NumberOfSectorsPerFAT * bpb->NumberOfFileAllocationTables ) * bpb->BytesPerSector);
uint32_t RootDirLBA =RootDirAddress/512;
uint16_t RootDir [16];
ATA_DEVICE::Read(BUS_PORT::Primary, DEVICE_DRIVE::MASTER,RootDirLBA, (uint16_t*) RootDir );

8
src/kernel/kernel.h
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@ -20,8 +20,12 @@ extern "C"{
#include "serial.h"
#include "pci.h"
#include "ide/ide.h"
#include "drivers/atapi/atapiDevice.h"
//#include "drivers/atapi/atapiDevice.h"
#include "drivers/ata/ataDevice.h"
#include "./PartitionTable/MBR/MasterBootRecord.h"
#include "./filesytems/FAT32/BiosParameterBlock.h"
#include "./filesytems/FAT32/ExtendBootRecord.h"
#include "./drivers/rsdp/rsdp.h"
#define CHECK_FLAG(flags, bit) ((flags) & (1 <<(bit)))