Begin multitasking refactor to support ring-3 TSS
diff --git a/src/kernel/descriptor_tables.c b/src/kernel/descriptor_tables.c
index 211dcb2..339162e 100644
--- a/src/kernel/descriptor_tables.c
+++ b/src/kernel/descriptor_tables.c
@@ -7,6 +7,7 @@
extern void gdt_flush(uint gdt);
extern void idt_flush(uint idt);
+extern void tss_flush();
static void gdt_set_gate(uint i, uint base, uint limit, uchar access,
uchar gran);
@@ -29,26 +30,7 @@
extern void (*interrupt_handlers[256])(struct registers);
-void init_gdt()
-{
- vga_write("Initializing GDT...\n");
- gdt_pointer.limit = sizeof(struct gdt_entry) * 5 - 1;
- gdt_pointer.base = (uint)&gdt_entries;
-
- gdt_set_gate(0, 0, 0, 0, 0); // Null segment
- gdt_set_gate(1, 0, ~0, 0x9a, 0xcf); // Code segment
- gdt_set_gate(2, 0, ~0, 0x92, 0xcf); // Data segment
- gdt_set_gate(3, 0, ~0, 0xfa, 0xcf); // User mode code segment
- gdt_set_gate(4, 0, ~0, 0xf2, 0xcf); // User mode data segment
-
- for (volatile uint i = 0; i < 0x1000; i++)
- {
- } // waste some time, for some reason this helps
-
- gdt_flush((uint)&gdt_pointer);
-
- vga_write("GDT Initialized\n");
-}
+struct tss_entry tss_entry;
static void gdt_set_gate(uint i, uint base, uint limit, uchar access,
uchar gran)
@@ -65,6 +47,44 @@
e->access = access;
}
+static void init_tss(uint num, uint ss, uint esp)
+{
+ gdt_set_gate(num, (uint)&tss_entry, (uint)&tss_entry+1, 0xe9, 0x00);
+
+ memset(&tss_entry, 0, sizeof(tss_entry));
+
+ tss_entry.ss0 = ss;
+ tss_entry.esp0 = esp;
+ tss_entry.cs = 0x0b;
+ // | 0b11 to make these readable from user-mode. i.e. user mode
+ // can switch to kernel mode using this tss
+ tss_entry.ss = tss_entry.ds = tss_entry.es = tss_entry.fs = tss_entry.gs = 0x13;
+}
+
+void init_gdt()
+{
+ vga_write("Initializing GDT...\n");
+ gdt_pointer.limit = sizeof(struct gdt_entry) * 5 - 1;
+ gdt_pointer.base = (uint)&gdt_entries;
+
+ gdt_set_gate(0, 0, 0, 0, 0); // Null segment, 0x00
+ gdt_set_gate(1, 0, ~0, 0x9a, 0xcf); // Code segment, 0x08
+ gdt_set_gate(2, 0, ~0, 0x92, 0xcf); // Data segment, 0x10
+ gdt_set_gate(3, 0, ~0, 0xfa, 0xcf); // User mode code segment, 0x18
+ gdt_set_gate(4, 0, ~0, 0xf2, 0xcf); // User mode data segment, 0x20
+ //init_tss(5, 0x10, 0x0); // 0x10 = kernel data segment, 0x28
+
+ for (volatile uint i = 0; i < 0x1000; i++)
+ {
+ } // waste some time, for some reason this helps
+
+ gdt_flush((uint)&gdt_pointer);
+ // For now let's not do this
+ // tss_flush();
+
+ vga_write("GDT Initialized\n");
+}
+
void init_idt()
{
idt_pointer.limit = sizeof(struct idt_entry) * 256 - 1;
@@ -114,3 +134,8 @@
init_gdt();
init_idt();
}
+
+void set_kernel_interrupt_stack(void *stack)
+{
+ tss_entry.esp0 = (uint)stack;
+}