7 files changed, 71 insertions, 130 deletions

diff --git a/src/kernel/arch/amd64/32/32 b/src/kernel/arch/amd64/32/32
deleted file mode 100644
index 9bd97e6..0000000
--- a/src/kernel/arch/amd64/32/32
+++ /dev/null
@@ -1,130 +0,0 @@
-#include <kernel/arch/generic.h>
-#include <kernel/arch/amd64/gdt.h>
-#include <shared/mem.h>
-#include <stdbool.h>
-#include <stdint.h>
-
-extern char _isr_mini_stack;
-
-struct gdt_entry {
-	uint64_t limit_low  : 16;
-	uint64_t base_low   : 24;
-	uint64_t accessed   :  1; // set by the processor
-	                          // CODE        | DATA
-	uint64_t rw         :  1; // readable?   | writeable?
-	uint64_t conforming :  1; // conforming? | expands down?
-	uint64_t code       :  1; // 1           | 0
-
-	uint64_t codeordata :  1; // 1 for everything other than TSS and LDT
-	uint64_t ring       :  2;
-	uint64_t present    :  1; // always 1
-	uint64_t limit_high :  4;
-	uint64_t available  :  1; // ???
-	uint64_t long_mode  :  1;
-	uint64_t x32        :  1;
-	uint64_t gran       :  1; // 1 - 4kb, 0 - 1b
-	uint64_t base_high  :  8;
-} __attribute__((packed));
-
-struct tss_entry {
-	uint32_t _unused0;
-	uint32_t esp0; // kernel mode stack pointer
-	uint32_t ss0;  // kernel mode stack segment
-	uint8_t  _unused1[0x5c];
-} __attribute__((packed));
-
-struct lgdt_arg {
-	uint16_t limit;
-	uint32_t base;
-} __attribute__((packed));
-
-__attribute__((section(".shared")))
-static struct gdt_entry GDT[SEG_end];
-__attribute__((section(".shared")))
-static struct tss_entry TSS;
-static struct lgdt_arg lgdt_arg; // probably doesn't need to be global
-
-static void gdt_fillout(struct gdt_entry* entry, uint8_t ring, bool code);
-static void gdt_prepare(void);
-static void gdt_load(void);
-
-
-static void gdt_fillout(struct gdt_entry* entry, uint8_t ring, bool code) {
-	*entry = (struct gdt_entry) {
-		// set up the identity mapping
-		.limit_low  = 0xFFFF,
-		.limit_high = 0xF,
-		.gran       = 1, // 4KB * 0xFFFFF = (almost) 4GB
-		.base_low   = 0,
-		.base_high  = 0,
-
-		.ring       = ring,
-		.code       = code,
-
-		.accessed   = 0,
-		.rw         = 1,
-		.conforming = 0,
-		.codeordata = 1,
-		.present    = 1,
-		.long_mode  = 0, // ???
-		.available  = 1, // ???
-		.x32        = 1,
-	};
-}
-
-static void gdt_prepare(void) {
-	GDT[SEG_null].present = 0;
-
-	gdt_fillout(&GDT[SEG_r0code], 0, true);
-	gdt_fillout(&GDT[SEG_r0data], 0, false);
-	gdt_fillout(&GDT[SEG_r3code], 3, true);
-	gdt_fillout(&GDT[SEG_r3data], 3, false);
-
-	// tss
-	memset(&TSS, 0, sizeof(TSS));
-	TSS.ss0 = SEG_r0data << 3; // kernel data segment
-	TSS.esp0 = (uintptr_t) &_isr_mini_stack;
-
-	GDT[SEG_TSS] = (struct gdt_entry) {
-		.limit_low  = sizeof(TSS),
-		.limit_high = sizeof(TSS) >> 16,
-		.gran       = 0,
-		.base_low   =  (uintptr_t) &TSS,
-		.base_high  = ((uintptr_t) &TSS) >> 24,
-
-		.accessed   = 1, // 1 for TSS
-		.rw         = 0, // 1 busy / 0 not busy
-		.conforming = 0, // 0 for TSS
-		.code       = 1, // 32bit
-		.codeordata = 0, // is a system entry
-		.ring       = 3,
-		.present    = 1,
-		.available  = 0, // 0 for TSS
-		.long_mode  = 0,
-		.x32        = 0, // idk
-	};
-}
-
-static void gdt_load(void) {
-	lgdt_arg.limit = sizeof(GDT) - 1;
-	lgdt_arg.base = (uintptr_t) &GDT;
-	asm("lgdt (%0)" 
-	    : : "r" (&lgdt_arg) : "memory");
-
-	asm("ltr %%ax"
-	    : : "a" (SEG_TSS << 3 | 3) : "memory");
-
-	// update all segment registers
-	gdt_farjump(SEG_r0code << 3);
-	asm("mov %0, %%ds;"
-	    "mov %0, %%ss;"
-	    "mov %0, %%es;"
-	    "mov %0, %%fs;"
-	    "mov %0, %%gs;"
-	    : : "r" (SEG_r0data << 3) : "memory");
-}
-
-void gdt_init(void) {
-	gdt_prepare();
-	gdt_load();
-}
diff --git a/src/kernel/arch/amd64/32/boot.s b/src/kernel/arch/amd64/32/boot.s
index 0e21036..0621038 100644
--- a/src/kernel/arch/amd64/32/boot.s
+++ b/src/kernel/arch/amd64/32/boot.s
@@ -2,6 +2,7 @@
 .global _start
 .type _start, @function
 _start:
+	cli
 	mov $_stack_top, %esp
 	push %ebx // save the address of the multiboot struct
 
diff --git a/src/kernel/arch/amd64/interrupts/irq.c b/src/kernel/arch/amd64/interrupts/irq.c
index b5e9255..9872ec7 100644
--- a/src/kernel/arch/amd64/interrupts/irq.c
+++ b/src/kernel/arch/amd64/interrupts/irq.c
@@ -5,6 +5,12 @@
 static const int PIC1 = 0x20;
 static const int PIC2 = 0xA0;
 
+static void pit_init(void) {
+	uint16_t divisor = 1193;
+	port_out8(0x40, divisor & 0xFF);
+	port_out8(0x40, divisor >> 8);
+}
+
 void irq_init(void) {
 	port_out8(PIC1, 0x11); /* start init sequence */
 	port_out8(PIC2, 0x11);
@@ -18,11 +24,14 @@ void irq_init(void) {
 	port_out8(PIC2+1, 0x1);
 
 	uint8_t mask = 0xff;
+	mask &= ~(1 << IRQ_PIT);
 	mask &= ~(1 << IRQ_PS2);
 	mask &= ~(1 << IRQ_COM1);
 
 	port_out8(PIC1+1, mask);
 	port_out8(PIC2+1, 0xff);
+
+	pit_init();
 }
 
 void irq_eoi(uint8_t line) {
diff --git a/src/kernel/arch/amd64/interrupts/irq.h b/src/kernel/arch/amd64/interrupts/irq.h
index 3340101..2a4b12d 100644
--- a/src/kernel/arch/amd64/interrupts/irq.h
+++ b/src/kernel/arch/amd64/interrupts/irq.h
@@ -3,6 +3,7 @@
 #include <stdint.h>
 
 #define IRQ_IBASE 0x20
+#define IRQ_PIT 0
 #define IRQ_PS2 1
 #define IRQ_COM1 4
 
diff --git a/src/kernel/arch/amd64/interrupts/isr.c b/src/kernel/arch/amd64/interrupts/isr.c
index 71da27b..0bfd865 100644
--- a/src/kernel/arch/amd64/interrupts/isr.c
+++ b/src/kernel/arch/amd64/interrupts/isr.c
@@ -3,6 +3,7 @@
 #include <kernel/arch/amd64/interrupts/irq.h>
 #include <kernel/arch/amd64/interrupts/isr.h>
 #include <kernel/arch/amd64/port_io.h>
+#include <kernel/arch/amd64/time.h>
 #include <kernel/arch/generic.h>
 #include <kernel/panic.h>
 #include <kernel/proc.h>
@@ -28,6 +29,11 @@ void isr_stage3(int interrupt, uint64_t *stackframe) {
 			isr_test_interrupt_called = true;
 			return;
 
+		case IRQ_IBASE + IRQ_PIT:
+			pit_irq();
+			irq_eoi(IRQ_PIT);
+			return;
+
 		case IRQ_IBASE + IRQ_PS2:
 			ps2_irq();
 			irq_eoi(IRQ_PS2);
diff --git a/src/kernel/arch/amd64/time.c b/src/kernel/arch/amd64/time.c
new file mode 100644
index 0000000..d6e53dd
--- /dev/null
+++ b/src/kernel/arch/amd64/time.c
@@ -0,0 +1,50 @@
+#include <kernel/arch/amd64/time.h>
+#include <kernel/panic.h>
+#include <kernel/proc.h>
+
+static uint64_t uptime = 0, goal = ~0;
+static struct process *scheduled = NULL;
+
+uint64_t uptime_ms(void) { return uptime; }
+
+static void update_goal(void) {
+	goal = scheduled ? scheduled->waits4timer.goal : ~(uint64_t)0;
+}
+
+void pit_irq(void) {
+	// TODO inefficient - getting here executes a lot of code which could just be a few lines of asm
+	uptime++;
+	if (uptime < goal) return;
+
+	struct process *p = scheduled;
+	assert(p);
+	scheduled = p->waits4timer.next;
+	process_transition(p, PS_RUNNING);
+	update_goal();
+}
+
+void timer_schedule(struct process *p, uint64_t time) {
+	process_transition(p, PS_WAITS4TIMER);
+	p->waits4timer.goal = time;
+
+	struct process **slot = &scheduled;
+	while (*slot && (*slot)->waits4timer.goal <= time) {
+		assert((*slot)->state == PS_WAITS4TIMER);
+		slot = &(*slot)->waits4timer.next;
+	}
+	p->waits4timer.next = *slot;
+	*slot = p;
+	update_goal();
+}
+
+void timer_deschedule(struct process *p) {
+	assert(p->state == PS_WAITS4TIMER);
+
+	struct process **slot = &scheduled;
+	while (*slot && *slot != p)
+		slot = &(*slot)->waits4timer.next;
+	assert(*slot);
+	*slot = p->waits4timer.next;
+
+	update_goal();
+}
diff --git a/src/kernel/arch/amd64/time.h b/src/kernel/arch/amd64/time.h
new file mode 100644
index 0000000..04ba9b0
--- /dev/null
+++ b/src/kernel/arch/amd64/time.h
@@ -0,0 +1,4 @@
+#pragma once
+#include <kernel/arch/generic.h>
+
+void pit_irq(void);