add broken Scheduler

11 files changed, 102 insertions, 13 deletions

diff --git a/drivers/keyboard.cc b/drivers/keyboard.cc
index 09fd4e9..2fae83c 100644
--- a/drivers/keyboard.cc
+++ b/drivers/keyboard.cc
@@ -25,7 +25,7 @@ Keyboard::Keyboard() : InterruptHandler(0x01) {
   dataport.write(dat_enable_scanning);
 }
 
-void Keyboard::trigger() {
+cpu_state_t* Keyboard::trigger(cpu_state_t* cpu) {
   const auto key = dataport.read();
 
   if (key < 0x80) {
@@ -157,4 +157,6 @@ void Keyboard::trigger() {
         break;
     }
   }
+
+  return cpu;
 }
diff --git a/drivers/keyboard.h b/drivers/keyboard.h
index cac0cb0..b7b67c1 100644
--- a/drivers/keyboard.h
+++ b/drivers/keyboard.h
@@ -8,7 +8,7 @@ class Keyboard : public InterruptHandler {
 public:
   Keyboard();
 
-  void trigger() override;
+  cpu_state_t* trigger(cpu_state_t*) override;
 
 private:
   /* 8042 PS/2 Controller Ports */
diff --git a/libk/types.h b/libk/types.h
index 08d42b9..4c50a35 100644
--- a/libk/types.h
+++ b/libk/types.h
@@ -4,7 +4,11 @@ typedef unsigned short size_t;
 typedef int ssize_t;
 
 typedef unsigned char uint8_t;
+
 typedef unsigned short uint16_t;
+constexpr uint16_t uint16_t_min = 0;
+constexpr uint16_t uint16_t_max = 0xffff;
+
 typedef unsigned int uint32_t;
 typedef unsigned long long int uint64_t;
 
diff --git a/src/idt.cc b/src/idt.cc
index 363afcd..5be738a 100644
--- a/src/idt.cc
+++ b/src/idt.cc
@@ -1,7 +1,6 @@
 #include "idt.h"
 #include <stdlib.h>
 #include "cpu/irq.h"
-#include "cpu/registers.h"
 #include "ports.h"
 
 static_assert(sizeof(IDT::Pointer) == 6);
@@ -39,23 +38,25 @@ bool IDT::uninstall(uint8_t irq, InterruptHandler* h) {
 #define ICW4_BUF_MASTER 0x0C /* Buffered mode/master */
 #define ICW4_SFNM 0x10       /* Special fully nested (not) */
 
-extern "C" void print_exception(cpu_state_t* r) {
+extern "C" uint32_t handle_exception(cpu_state_t* r) {
   printk("exception ", uhex{r->irq}, " error ", uhex{r->error}, '\n');
   asm volatile("cli");
   while (true) asm volatile("hlt");
   __builtin_unreachable();
+
+  return reinterpret_cast<uint32_t>(r);
 };
 
 extern "C" uint32_t handle_interrupt(cpu_state_t* r) {
-  if (r->irq < irq_base) print_exception(r);
+  if (r->irq < irq_base) return reinterpret_cast<uint32_t>(r);
 
   if (handlers[r->irq] != nullptr) {
-    handlers[r->irq]->trigger();
+    r = handlers[r->irq]->trigger(r);
   }
 
   pic1_t pic1;
   pic1.write(0x20);
-  if (r->irq > 7 + irq_base) {
+  if (r->irq > irq_base + 7) {
     pic2_t pic2;
     pic2.write(0x20);
   }
diff --git a/src/idt.h b/src/idt.h
index 3a9848f..ce5209c 100644
--- a/src/idt.h
+++ b/src/idt.h
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <types.h>
+#include "cpu/registers.h"
 
 class InterruptHandler {
 private:
@@ -11,7 +12,7 @@ protected:
   ~InterruptHandler();
 
 public:
-  virtual void trigger();
+  virtual cpu_state_t* trigger(cpu_state_t*);
 };
 
 class IDT {
diff --git a/src/idt/interrupthandler.cc b/src/idt/interrupthandler.cc
index 7af830b..7524f19 100644
--- a/src/idt/interrupthandler.cc
+++ b/src/idt/interrupthandler.cc
@@ -9,6 +9,7 @@ InterruptHandler::~InterruptHandler() {
   IDT::uninstall(m_irq, this);
 }
 
-void InterruptHandler::trigger() {
+cpu_state_t* InterruptHandler::trigger(cpu_state_t* cpu) {
   printk("Unhandled interrupt ", uhex{m_irq}, '\n');
+  return cpu;
 }
diff --git a/src/idt/stubs.S b/src/idt/stubs.S
index 97f1797..4f1440d 100644
--- a/src/idt/stubs.S
+++ b/src/idt/stubs.S
@@ -2,6 +2,7 @@
 
 .section .text
 .extern handle_interrupt
+.extern handle_exception
 
 .macro interrupt num
 .global interrupt\num
@@ -16,14 +17,14 @@ interrupt\num:
 exception\num:
     push $0
     push $\num
-    jmp interrupt_common
+    jmp exception_common
 .endm
 
 .macro exception_ec num
 .global exception\num
 exception\num:
     push $\num
-    jmp interrupt_common
+    jmp exception_common
 .endm
 
 /* exceptions */
@@ -67,12 +68,25 @@ interrupt 0x0d  # fpu
 interrupt 0x0e  # primary ATA
 interrupt 0x0f  # secondary ATA
 
+exception_common:
+    pusha
+
+    push %esp
+    call handle_exception
+    mov %eax, %esp
+
+    popa
+    /* remove error code and irq from stack */
+    add $8, %esp
+
+    iret
+
 interrupt_common:
     pusha
 
     push %esp
     call handle_interrupt
-    mov %eax, %esp
+    add $4, %esp
 
     popa
     /* remove error code and irq from stack */
diff --git a/src/kernel.cc b/src/kernel.cc
index ff8e6bd..85d4124 100644
--- a/src/kernel.cc
+++ b/src/kernel.cc
@@ -13,6 +13,7 @@
 #include "cga.h"
 #include "gdt.h"
 #include "idt.h"
+#include "scheduler.h"
 #include "serial.h"
 
 #include "keyboard.h"
@@ -50,6 +51,7 @@ void kernel_main([[maybe_unused]] uint32_t mb_magic, [[maybe_unused]] uint32_t m
   GDT gdt;
   IDT idt{gdt.codeDescriptor()};
 
+  Scheduler s{gdt.codeDescriptor()};
   Keyboard kb;
 
   idt.enable();
diff --git a/src/makefile b/src/makefile
index 64853fe..d4b2ac8 100644
--- a/src/makefile
+++ b/src/makefile
@@ -8,7 +8,8 @@ CXX_OBJ += src/kernel.o \
 	   src/gdt.o \
 	   src/gdt/segmentdescriptor.o \
 	   src/idt.o \
-	   src/idt/interruptgate.o src/idt/interrupthandler.o
+	   src/idt/interruptgate.o src/idt/interrupthandler.o \
+	   src/scheduler.o
 
 src/cpu/irq.h: $(OBJ_DIR)/src/idt/stubs.o
 	@echo "  GEN $@"
diff --git a/src/scheduler.cc b/src/scheduler.cc
new file mode 100644
index 0000000..1557e28
--- /dev/null
+++ b/src/scheduler.cc
@@ -0,0 +1,46 @@
+#include "scheduler.h"
+#include <stdlib.h>
+
+void task_a(void) {
+  while (true) printk("A");
+}
+
+void task_b(void) {
+  while (true) printk("B");
+}
+
+static uint8_t stack_a[4096] = {0};
+static uint8_t stack_b[4096] = {0};
+constexpr uint16_t max_tasks = 2;
+static cpu_state_t* tasks[max_tasks];
+
+Scheduler::Scheduler(uint16_t cs) : InterruptHandler(0x00) {
+  add_task(stack_a, cs, &task_a);
+  add_task(stack_b, cs, task_b);
+}
+
+bool Scheduler::add_task(uint8_t* stack, uint16_t cs, void (*entry)()) {
+  if (last_task_id == uint16_t_max) return false;
+
+  uint16_t id = last_task_id++;
+  ++num_tasks;
+
+  cpu_state_t* cpu_state = reinterpret_cast<cpu_state_t*>(stack + 4096 - sizeof(cpu_state_t));
+  cpu_state->eip = reinterpret_cast<uint32_t>(entry);
+  cpu_state->cs = cs;
+  cpu_state->eflags = 0x202;
+
+  tasks[id] = cpu_state;
+  printk("adding task: cs ", uhex{cpu_state->cs}, " stack ", uhex{reinterpret_cast<uint32_t>(tasks[id])}, " entry ",
+         uhex{cpu_state->eip}, '\n');
+  return true;
+}
+
+cpu_state_t* Scheduler::trigger(cpu_state_t* cpu) {
+  tasks[current_task] = cpu;
+
+  if (++current_task >= num_tasks) current_task %= num_tasks;
+
+  // printk("swapped to task ", current_task, '\n');
+  return tasks[current_task];
+}
diff --git a/src/scheduler.h b/src/scheduler.h
new file mode 100644
index 0000000..9e5e9f2
--- /dev/null
+++ b/src/scheduler.h
@@ -0,0 +1,17 @@
+#pragma once
+
+#include <types.h>
+#include "idt.h"
+
+class Scheduler : public InterruptHandler {
+public:
+  Scheduler(uint16_t cs);
+
+  bool add_task(uint8_t* stack, uint16_t cs, void (*entry)());
+  [[nodiscard]] cpu_state_t* trigger(cpu_state_t*) override;
+
+private:
+  uint16_t current_task = 0;
+  uint16_t last_task_id = 0;
+  uint16_t num_tasks = 0;
+};