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#include "i8253.h"
#include "i386.h"
#include "IO.h"
#include "VGA.h"
#include "Process.h"
#include "system.h"
#include "PIC.h"
#include "Scheduler.h"
#define IRQ_TIMER 0
extern "C" void tick_ISR();
extern "C" void clock_handle();
extern volatile DWORD state_dump;
asm(
".globl tick_ISR \n"
".globl state_dump \n"
"state_dump: \n"
".long 0\n"
"tick_ISR: \n"
" pusha\n"
" pushw %ds\n"
" pushw %es\n"
" pushw %fs\n"
" pushw %gs\n"
" pushw %ss\n"
" pushw %ss\n"
" pushw %ss\n"
" pushw %ss\n"
" pushw %ss\n"
" popw %ds\n"
" popw %es\n"
" popw %fs\n"
" popw %gs\n"
" mov %esp, state_dump\n"
" call clock_handle\n"
" popw %gs\n"
" popw %gs\n"
" popw %fs\n"
" popw %es\n"
" popw %ds\n"
" popa\n"
" iret\n"
);
/* Timer related ports */
#define TIMER0_CTL 0x40
#define TIMER1_CTL 0x41
#define TIMER2_CTL 0x42
#define PIT_CTL 0x43
/* Building blocks for PIT_CTL */
#define TIMER0_SELECT 0x00
#define TIMER1_SELECT 0x40
#define TIMER2_SELECT 0x80
#define MODE_COUNTDOWN 0x00
#define MODE_ONESHOT 0x02
#define MODE_RATE 0x04
#define MODE_SQUARE_WAVE 0x06
#define WRITE_WORD 0x30
/* Miscellaneous */
#define BASE_FREQUENCY 1193182
void clock_handle()
{
IRQHandlerScope scope(IRQ_TIMER);
if (!current)
return;
system.uptime++;
if (current->tick())
return;
auto& regs = *reinterpret_cast<RegisterDump*>(state_dump);
current->tss().gs = regs.gs;
current->tss().fs = regs.fs;
current->tss().es = regs.es;
current->tss().ds = regs.ds;
current->tss().edi = regs.edi;
current->tss().esi = regs.esi;
current->tss().ebp = regs.ebp;
current->tss().ebx = regs.ebx;
current->tss().edx = regs.edx;
current->tss().ecx = regs.ecx;
current->tss().eax = regs.eax;
current->tss().eip = regs.eip;
current->tss().cs = regs.cs;
current->tss().eflags = regs.eflags;
// Compute process stack pointer.
// Add 12 for CS, EIP, EFLAGS (interrupt mechanic)
current->tss().esp = regs.esp + 12;
current->tss().ss = regs.ss;
if ((current->tss().cs & 3) != 0) {
current->tss().ss = regs.ss_if_crossRing;
current->tss().esp = regs.esp_if_crossRing;
}
if (!Scheduler::pick_next())
return;
Scheduler::prepare_for_iret_to_new_process();
// Set the NT (nested task) flag.
asm(
"pushf\n"
"orl $0x00004000, (%esp)\n"
"popf\n"
);
}
namespace PIT {
void initialize()
{
WORD timer_reload;
IO::out8(PIT_CTL, TIMER0_SELECT | WRITE_WORD | MODE_SQUARE_WAVE);
timer_reload = (BASE_FREQUENCY / TICKS_PER_SECOND);
/* Send LSB and MSB of timer reload value. */
kprintf("PIT(i8253): %u Hz, square wave (%x)\n", TICKS_PER_SECOND, timer_reload);
IO::out8(TIMER0_CTL, LSB(timer_reload));
IO::out8(TIMER0_CTL, MSB(timer_reload));
registerInterruptHandler(IRQ_VECTOR_BASE + IRQ_TIMER, tick_ISR);
PIC::enable(IRQ_TIMER);
}
}
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