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Disk does very basic read caching

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This commit is contained in:
Lucia Ceionia 2023-02-10 01:06:42 -06:00
parent 89c0f95219
commit d1024d7793
3 changed files with 77 additions and 5 deletions
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78
disk.c
View File

@ -5,6 +5,13 @@
extern void *memcpy(void *restrict dest, const void *restrict src, uintptr_t n);
uintptr_t DiskCacheBlockSize = 0x1000; // 512 * 4
uintptr_t DiskCacheSectorMask = 7;
uintptr_t DiskCacheSectorSize = 8;
uint8_t (*DiskCache)[128][0x1000] = (uint8_t (*)[128][0x1000])0x280000;
uint32_t DiskCacheLastRead[128];
uint32_t DiskCacheSector[128];
extern uint32_t _gpf_eax_save;
extern uint32_t _gpf_eflags_save;
extern uint16_t error_screen[80*50]; // defined in kernel.c
@ -14,6 +21,7 @@ uint32_t numHead;
uint32_t secPerTrack;
uint32_t maxCylinder;
char useCHS = -1;
// TODO This function also inits cache, make that go somewhere else
void Disk_SetupCHS() {
union V86Regs_t regs;
// Check for INT 13 Extensions support
@ -39,25 +47,77 @@ void Disk_SetupCHS() {
maxCylinder = ((_gpf_eax_save & 0xff0000) >> 16) | ((_gpf_eax_save & 0xc0) << 2);
useCHS = 1;
}
// Init Cache
for (int i = 0; i < 128; i++) {
DiskCacheLastRead[i] = 0;
DiskCacheSector[i] = -1;
}
}
extern uint32_t TIMERVAL;
uint8_t *FindInCache(uint32_t sector) {
uint32_t maskedSector = sector & ~DiskCacheSectorMask;
for (int i = 0; i < 128; i++) {
// Found
if (DiskCacheSector[i] == maskedSector) {
DiskCacheLastRead[i] = TIMERVAL;
return &(*DiskCache)[i][(sector & DiskCacheSectorMask) << 9];
}
}
// Not Found
return 0;
}
void AddToCache(uint32_t sector, uint8_t *buffer) {
uintptr_t lowestFoundTime = DiskCacheLastRead[0];
uintptr_t lowestFoundIdx = 0;
for (int i = 1; i < 32; i++) {
if (DiskCacheLastRead[i] < lowestFoundTime) {
lowestFoundTime = DiskCacheLastRead[i];
lowestFoundIdx = i;
}
}
for (int i = 0; i < DiskCacheBlockSize / sizeof(uint32_t); i++)
((uint32_t *)((*DiskCache)[lowestFoundIdx]))[i] = ((uint32_t*)buffer)[i];
DiskCacheLastRead[lowestFoundIdx] = TIMERVAL;
DiskCacheSector[lowestFoundIdx] = sector;
}
// NOTE Only updates one sector (512B)
void UpdateCache(uint32_t sector, uint8_t *buffer) {
uint8_t *cache = FindInCache(sector);
// Not in cache, nothing to update
if (!cache) return;
for (int i = 0; i < SECTOR_SIZE/sizeof(uint32_t); i++)
((uint32_t*)cache)[i] = ((uint32_t*)buffer)[i];
}
uint32_t DFS_ReadSector(uint8_t unit, uint8_t *buffer, uint32_t sector, uint32_t count) {
// NOTE If the buffer provided is outside the 0x20000-0x2FE00 range,
// the function will use that buffer for the Virtual 8086 process
// and copy to the other buffer after
uint8_t *v86buf = buffer;
if ((uintptr_t)v86buf < 0x20000 || (uintptr_t)v86buf > 0x2FE00)
v86buf = (uint8_t *)0x20000;
if ((uintptr_t)v86buf >= 0x20000 && (uintptr_t)v86buf < 0x28000)
v86buf = (uint8_t *)0x28000;
else v86buf = (uint8_t *)0x20000;
// TODO This check should probably happen at the kernel level
if (useCHS == -1) {
Disk_SetupCHS();
}
uint8_t *cache = FindInCache(sector);
if (cache) {
memcpy(buffer, cache, count * SECTOR_SIZE);
return 0;
}
// TODO Do error handling
if (!useCHS) {
// LBA Read
v86disk_addr_packet.start_block = sector;
v86disk_addr_packet.blocks = count;
v86disk_addr_packet.start_block = sector & ~DiskCacheSectorMask;
v86disk_addr_packet.blocks = DiskCacheSectorSize;
v86disk_addr_packet.transfer_buffer =
(uintptr_t)v86buf & 0x000F |
(((uintptr_t)v86buf & 0xFFFF0) << 12);
@ -65,6 +125,15 @@ uint32_t DFS_ReadSector(uint8_t unit, uint8_t *buffer, uint32_t sector, uint32_t
regs.h.ah = 0x42;
FARPTR v86_entry = i386LinearToFp(v86DiskOp);
enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry), &regs);
if (v86disk_addr_packet.blocks != DiskCacheSectorSize) {
uint16_t *vga = error_screen;
vga += printStr("INT13 Read Secs: ", vga);
vga += printDec(v86disk_addr_packet.blocks, vga);
error_environment();
for(;;);
}
AddToCache(sector & ~DiskCacheSectorMask, v86buf);
v86buf = &v86buf[(sector & DiskCacheSectorMask) << 9];
} else {
uint32_t tmp = sector / secPerTrack;
uint32_t sec = (sector % (secPerTrack)) + 1;
@ -110,6 +179,7 @@ uint32_t DFS_WriteSector(uint8_t unit, uint8_t *buffer, uint32_t sector, uint32_
regs.w.ax = 0x4300;
FARPTR v86_entry = i386LinearToFp(v86DiskOp);
enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry), &regs);
UpdateCache(sector, buffer);
} else {
uint16_t *vga = error_screen;
vga += printStr("CHS Write Unimplemented", vga);

1
handler.nasm
View File

@ -50,6 +50,7 @@ test eax, eax
jz .loop
ret
global TIMERVAL
TIMERVAL: dd 0
global timerHandler
timerHandler:

3
kernel.c
View File

@ -174,7 +174,8 @@ Protected Only (1MB+)
100000 - 200000 Kernel Code (1mB)
200000 - 200080 TSS (128B)
200080 - 202080 TSS IOMAP (8kB)
202080 - 300000 Free (~1mB)
202080 - 300000 Free (~1/2mB)
280000 - 300000 Disk Cache (512kB)
300000 - 310000 Task Stack (64kB)
310000 - 320000 Interrupt Stack (64kB)
320000 - 400000 Kernel Stack (896kB)