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