From c39cbb79cdf58e243db962da45ddc5420c875c55 Mon Sep 17 00:00:00 2001
From: ngiddings <nathang567@gmail.com>
Date: Sun, 18 Apr 2021 02:10:03 -0500
Subject: [PATCH] Task contexts now load segment registers correctly Interrupt
 enable bit set in saved EFLAGS register

---
 include/context.h |  2 +-
 src/x86/context.c | 13 +++++++++----
 src/x86/isr.c     | 24 ++++++++++++++++++++++--
 3 files changed, 32 insertions(+), 7 deletions(-)

diff --git a/include/context.h b/include/context.h
index 792966c..c65932e 100644
--- a/include/context.h
+++ b/include/context.h
@@ -5,4 +5,4 @@
 
 void *initialize_context(void *task_entry, struct page_stack_t *page_stack);
 
-void load_context(struct process_state_t *context) __attribute__((noreturn));
+void load_context(struct process_state_t *context) __attribute__((naked));
diff --git a/src/x86/context.c b/src/x86/context.c
index 9da0bb2..69e1481 100644
--- a/src/x86/context.c
+++ b/src/x86/context.c
@@ -35,7 +35,7 @@ void *initialize_context(void *task_entry, struct page_stack_t *page_stack)
     memset(stack, 0, sizeof(*stack));
     stack->eip = (uint32_t)task_entry;
     stack->cs = 27;
-    stack->flags = flags;
+    stack->flags = flags | 0x200;
     stack->esp = 0xFF7FE000;
     stack->ss = 35;
     stack->esp_temp = &stack->eax;
@@ -44,8 +44,13 @@ void *initialize_context(void *task_entry, struct page_stack_t *page_stack)
 
 void load_context(struct process_state_t *context)
 {
-    asm("mov %0, %%esp; "
+    asm("mov $0x10, %%ax; "
+        "mov %%ax, %%ds; "
+        "mov %%ax, %%es; "
+        "mov %%ax, %%fs; "
+        "mov %%ax, %%gs; "
+        ::: "ax");
+    asm("mov 4(%esp), %esp; "
         "popal; "
-        "iret; "
-        :: "r"(context));
+        "iret; ");
 }
\ No newline at end of file
diff --git a/src/x86/isr.c b/src/x86/isr.c
index 81dbc4e..2e95102 100644
--- a/src/x86/isr.c
+++ b/src/x86/isr.c
@@ -16,6 +16,12 @@ void isr_division_by_zero(void* frame)
 void isr_gp_fault(void* frame, unsigned int error)
 {
     asm("cli");
+    asm("mov $0x10, %%ax; "
+        "mov %%ax, %%ds; "
+        "mov %%ax, %%es; "
+        "mov %%ax, %%fs; "
+        "mov %%ax, %%gs; "
+        ::: "ax");
     printf("Exception: GP fault, code %08x\n", error);
     asm("hlt");
 }
@@ -25,6 +31,12 @@ void isr_page_fault(void* frame, unsigned int error)
     size_t addr;
     asm("mov %%cr2, %0"
         : "=r"(addr));
+    asm("mov $0x10, %%ax; "
+        "mov %%ax, %%ds; "
+        "mov %%ax, %%es; "
+        "mov %%ax, %%fs; "
+        "mov %%ax, %%gs; "
+        ::: "ax");
     printf("Exception: Page fault, code %08x, linear address %08x\n", error, addr);
     asm("hlt");
 }
@@ -45,11 +57,19 @@ void isr_timer(void* frame)
 
 void isr_preempt(void* frame)
 {
-    asm("pushal;"
-        "mov %esp, %ebp");
+    asm("pushal; "
+        "mov %esp, %ebp; ");
+    asm("mov $0x10, %%ax; "
+        "mov %%ax, %%ds; "
+        "mov %%ax, %%es; "
+        "mov %%ax, %%fs; "
+        "mov %%ax, %%gs; "
+        ::: "ax");
     struct process_state_t *process_state;
     asm("mov %%ebp, %0"
         : "=r"(process_state));
+    printf("Preempted process %08x.\n", kernel_state.active_process);
+    apic_eoi();
     next_process(&kernel_state, process_state);
 }