From e8c6577617bffa4402c07c7aa20e3c24f03c1c20 Mon Sep 17 00:00:00 2001
From: Benji Dial <benji6283@gmail.com>
Date: Sun, 6 Sep 2020 00:48:07 -0400
Subject: program loading, others

big kernel additions: paging, elf loading, separate kernel and user page allocation
it now properly loads and runs sd0:bin/init.elf
still need to determine which disk was booted from, and start the init on that disk
---
 src/kernel/task.c | 90 +++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 84 insertions(+), 6 deletions(-)

(limited to 'src/kernel/task.c')

diff --git a/src/kernel/task.c b/src/kernel/task.c
index 3e64639..79b2f09 100644
--- a/src/kernel/task.c
+++ b/src/kernel/task.c
@@ -1,14 +1,92 @@
 #include "panic.h"
 #include "task.h"
+#include "paging.h"
 
-segment_id new_segment(bool is_code, uint32_t length, uint32_t *location_out) {
-  panic("TODO: make new segment");
+struct tss {
+  struct tss *prev;
+
+  uint32_t esp0;
+  uint32_t ss0;
+  uint32_t esp1;
+  uint32_t ss1;
+  uint32_t esp2;
+  uint32_t ss2;
+
+  uint32_t cr3;
+  uint32_t eip;
+  uint32_t eflags;
+
+  uint32_t eax;
+  uint32_t ecx;
+  uint32_t edx;
+  uint32_t ebx;
+  uint32_t esp;
+  uint32_t ebp;
+  uint32_t esi;
+  uint32_t edi;
+
+  uint32_t es;
+  uint32_t cs;
+  uint32_t ss;
+  uint32_t ds;
+  uint32_t fs;
+  uint32_t gs;
+
+  uint32_t ldt;
+  uint16_t trap;
+  uint16_t iomp;
+} __attribute__ ((packed));
+
+#define TSS ((struct tss *)0x00004f98)
+
+#define MAX_TASKS 64
+
+struct task_state tasks[MAX_TASKS];
+struct task_state *active_task;
+
+void init_tasks() {
+  active_task = tasks;
+
+  for (uint8_t i = 0; i < MAX_TASKS; ++i)
+    tasks[i].page_directory = 0;
+
+  TSS->ss0 = 0x18;
+  TSS->esp0 = 0x00040000;
+//TSS->cs = 0x13;
+//TSS->ds = 0x1b;
+//TSS->ss = 0x1b;
+  TSS->iomp = sizeof(struct tss);
+
+  asm volatile (
+    "mov $0x08, %%ax\n"
+    "ltr %%ax"
+  : : : "ax");
+}
+
+void new_task(struct task_state state) {
+  for (uint8_t n = 0; n < MAX_TASKS; ++n)
+    if (!tasks[n].page_directory) {
+      tasks[n] = state;
+      return;
+    }
+  panic("Maximum number of tasks reached.");
 }
 
-segment_id mirror_segment(bool is_code, segment_id other) {
-  panic("TODO: make new segment with same base and limit");
+void advance_active_task() {
+  struct task_state *prev_task = active_task;
+  do {
+    if (++active_task == tasks + MAX_TASKS)
+      active_task = tasks;
+    if (active_task == prev_task) {
+      logsz("No active tasks.\nHalting.");
+      while (1)
+        asm ("hlt");
+    }
+  }
+  while (!active_task->page_directory);
 }
 
-task_handle new_task(segment_id cs, segment_id ds, uint32_t eip, uint32_t esp) {
-  panic("TODO: add task to scheduler");
+void delete_task(struct task_state *state) {
+  free_task_pd(state->page_directory);
+  state->page_directory = 0;
 }
\ No newline at end of file
-- 
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