Paging Fault During ATA Read/Write
Posted: Mon Jan 13, 2025 1:58 pm
Hello, everyone,
I'm encountering a paging fault in my custom OS when attempting to perform ATA read and write operations in my function. I've identified that the issue occurs within the following block of code from my updateDir function:
When this code runs, the CPU reports a paging fault with the following debug output:
Full Context
Here's the full function where the problematic code resides:
ata.c:
What I've Tried:
1. Verified that the dir_buffer array is allocated correctly.
2. Checked the ata_identify and ata_read/ata_write functions, and they seem to work in other contexts.
3. Confirmed that the START_DIR address is within the expected range.
Any help or suggestions would be greatly appreciated!
Thank you in advance.
https://github.com/IlanVinograd/OS_32Bi ... keyboard.c
I'm encountering a paging fault in my custom OS when attempting to perform ATA read and write operations in my
Code: Select all
updateDir Code: Select all
// Read the current directory entries from the disk
uint8_t dir_buffer[MAX_DIR * 16] = {0};
ata_identify(ATA_PRIMARY_IO, ATA_MASTER);
ata_read(ATA_PRIMARY_IO, ATA_MASTER, START_DIR, 1, dir_buffer);
// Copy the DirEntry struct into the directory buffer at the correct position
memcpy(&dir_buffer[pos * 16], &entry, sizeof(DirEntry));
// Write the updated directory entries back to the disk
ata_identify(ATA_PRIMARY_IO, ATA_MASTER);
ata_write(ATA_PRIMARY_IO, ATA_MASTER, START_DIR, MAX_DIR * 16 / 512, dir_buffer);
Code: Select all
CR2=00000000
EIP=c01015d0
Here's the full function where the problematic code resides:
Code: Select all
bool_t updateDir(char* filename) {
DirEntry entry = {0};
strncpy((char *)entry.name, filename, sizeof(entry.name) - 1);
entry.size = 0;
int pos = -1;
// Find the first available directory slot
for (int i = 0; i < MAX_DIR; i++) {
if (dir[i] == 0) {
dir[i] = 1;
entry.fat_entry = i;
pos = i;
break;
}
}
if (pos == -1) {
printf("Error: No free directory entry found\n");
return false;
}
uint8_t dir_buffer[MAX_DIR * 16] = {0};
ata_identify(ATA_PRIMARY_IO, ATA_MASTER);
ata_read(ATA_PRIMARY_IO, ATA_MASTER, START_DIR, 1, dir_buffer);
memcpy(&dir_buffer[pos * 16], &entry, sizeof(DirEntry));
ata_identify(ATA_PRIMARY_IO, ATA_MASTER);
ata_write(ATA_PRIMARY_IO, ATA_MASTER, START_DIR, MAX_DIR * 16 / 512, dir_buffer);
return true;
}
Code: Select all
#include "../Includes/ata.h"
void ata_initialize(uint16_t io_base, uint8_t drive) {
outPort(io_base + 6, drive);
outPort(io_base + 2, 0);
outPort(io_base + 3, 0);
outPort(io_base + 4, 0);
outPort(io_base + 5, 0);
outPort(io_base + 7, 0xEC);
uint8_t status = inPort(io_base + 7);
// Wait for BSY to clear
while ((status & 0x80) != 0) {
status = inPort(io_base + 7);
}
}
static void ata_wait_bsy(uint16_t io_base) {
while (inPort(io_base + 7) & 0x80); // Wait for BSY to clear
}
static void ata_wait_drq(uint16_t io_base) {
while (!(inPort(io_base + 7) & 0x08)); // Wait for DRQ to set
}
void ata_read(uint16_t io_base, uint8_t drive, uint32_t lba, uint8_t sectors, uint8_t* buffer) {
if (!buffer || sectors == 0) {
return;
}
if (sectors > 256) {
return;
}
// Select drive and LBA
outPort(io_base + 6, 0xE0 | (drive << 4) | ((lba >> 24) & 0x0F));
outPort(io_base + 2, sectors);
outPort(io_base + 3, (uint8_t)(lba));
outPort(io_base + 4, (uint8_t)(lba >> 8));
outPort(io_base + 5, (uint8_t)(lba >> 16));
outPort(io_base + 7, 0x20); // Read command
for (uint8_t i = 0; i < sectors; i++) {
ata_wait_bsy(io_base);
if (inPort(io_base + 7) & 0x01) { // Check for error
printf("ATA read error on sector %u.\n",RED_ON_BLACK_WARNING, lba + i);
return;
}
ata_wait_drq(io_base);
for (uint16_t j = 0; j < ATA_SECTOR_SIZE / 2; j++) {
((uint16_t*)buffer)[j] = inPort16(io_base);
}
buffer += ATA_SECTOR_SIZE;
}
}
void ata_write(uint16_t io_base, uint8_t drive, uint32_t lba, uint8_t sectors, const uint8_t* buffer) {
outPort(io_base + 6, 0xE0 | (drive << 4) | ((lba >> 24) & 0x0F));
outPort(io_base + 2, sectors);
outPort(io_base + 3, (uint8_t)(lba));
outPort(io_base + 4, (uint8_t)(lba >> 8));
outPort(io_base + 5, (uint8_t)(lba >> 16));
outPort(io_base + 7, 0x30);
for (uint8_t i = 0; i < sectors; i++) {
ata_wait_bsy(io_base);
ata_wait_drq(io_base);
for (uint16_t j = 0; j < ATA_SECTOR_SIZE / 2; j++) {
outPort16(io_base, ((uint16_t*)buffer)[j]);
}
buffer += ATA_SECTOR_SIZE;
}
ata_wait_bsy(io_base);
outPort(io_base + 7, 0xE7);
ata_wait_bsy(io_base);
}
void ata_identify(uint16_t io_base, uint8_t drive) {
outPort(io_base + 6, drive);
outPort(io_base + 2, 0);
outPort(io_base + 3, 0);
outPort(io_base + 4, 0);
outPort(io_base + 5, 0);
outPort(io_base + 7, 0xEC);
ata_wait_bsy(io_base);
uint8_t status = inPort(io_base + 7);
if (status == 0) {
printf("No ATA device detected.\n", COLOR_BLACK_ON_WHITE);
return;
}
uint16_t buffer[256];
for (uint16_t i = 0; i < 256; i++) {
buffer[i] = inPort16(io_base);
}
}
1. Verified that the dir_buffer array is allocated correctly.
2. Checked the ata_identify and ata_read/ata_write functions, and they seem to work in other contexts.
3. Confirmed that the START_DIR address is within the expected range.
Any help or suggestions would be greatly appreciated!
Thank you in advance.
https://github.com/IlanVinograd/OS_32Bi ... keyboard.c