Set task state segment

arch/Makefile

@@ -18,6 +18,8 @@ OBJS += kprintf.c.o
 
 OBJS += protected.c.o protected.asm.cpp.o
 
+OBJS += tss.c.o
+
 OBJS += interrupt.asm.cpp.o
 
 OBJS += exception.c.o

arch/config.h

@@ -16,7 +16,8 @@
 #define GDT_KERNEL_DS_INDEX 2
 #define GDT_USER_CS_INDEX   3
 #define GDT_USER_DS_INDEX   4
-#define GDT_SIZE            5
+#define GDT_TSS_INDEX       5
+#define GDT_SIZE            6
 
 #define GDT_DESCRIPTOR_SIZE 8 // bytes
 
@@ -27,6 +28,7 @@
 #define GDT_KERNEL_DS_SELECTOR GDT_SEGMENT_SELECTOR(GDT_KERNEL_DS_INDEX)
 #define GDT_USER_CS_SELECTOR   GDT_SEGMENT_SELECTOR(GDT_USER_CS_INDEX)
 #define GDT_USER_DS_SELECTOR   GDT_SEGMENT_SELECTOR(GDT_USER_DS_INDEX)
+#define GDT_TSS_SELECTOR       GDT_SEGMENT_SELECTOR(GDT_TSS_INDEX)
 
 #define INT_EXCEPTION_COUNT 32
 #define INT_HWINT_COUNT     16

arch/protected.c

@@ -5,6 +5,7 @@
 #include "asm.h"
 #include "interrupt.h"
 #include "hwint.h"
+#include "tss.h"
 
 #include <kernelmq/stdlib.h>
 
@@ -75,6 +76,8 @@ void protected_initialize()
     gdt_set_gate(GDT_USER_CS_INDEX,   0, 0xFFFFFFFF, 0xFA, 0xCF);
     gdt_set_gate(GDT_USER_DS_INDEX,   0, 0xFFFFFFFF, 0xF2, 0xCF);
 
+    tss_write_to_gdt(&gdt_entries[GDT_TSS_INDEX]);
+
     logger_info("Setup IDT.");
 
     kmemset(idt_entries, 0, sizeof(idt_entries));

arch/tss.c

@@ -0,0 +1,88 @@
+#include "tss.h"
+
+#include "config.h"
+
+#include <kernelmq/stdlib.h>
+
+struct gdt_entry_bits {
+    unsigned int limit_low              : 16;
+    unsigned int base_low               : 24;
+    unsigned int accessed               : 1;
+    unsigned int read_write             : 1;
+    unsigned int conforming_expand_down : 1;
+    unsigned int code                   : 1;
+    unsigned int always_1               : 1;
+    unsigned int DPL                    : 2;
+    unsigned int present                : 1;
+    unsigned int limit_high             : 4;
+    unsigned int available              : 1;
+    unsigned int always_0               : 1;
+    unsigned int big                    : 1;
+    unsigned int gran                   : 1;
+    unsigned int base_high              : 8;
+}
+__attribute__((packed));
+
+struct tss_entry {
+    unsigned int prev_tss;
+    unsigned int esp0;
+    unsigned int ss0;
+    unsigned int esp1;
+    unsigned int ss1;
+    unsigned int esp2;
+    unsigned int ss2;
+    unsigned int cr3;
+    unsigned int eip;
+    unsigned int eflags;
+    unsigned int eax;
+    unsigned int ecx;
+    unsigned int edx;
+    unsigned int ebx;
+    unsigned int esp;
+    unsigned int ebp;
+    unsigned int esi;
+    unsigned int edi;
+    unsigned int es;
+    unsigned int cs;
+    unsigned int ss;
+    unsigned int ds;
+    unsigned int fs;
+    unsigned int gs;
+    unsigned int ldt;
+    unsigned short trap;
+    unsigned short iomap_base;
+}
+__attribute__((packed));
+
+static struct tss_entry tss;
+
+void tss_write_to_gdt(void *gdt_entry_ptr)
+{
+    struct gdt_entry_bits *const g = gdt_entry_ptr;
+
+    unsigned long base = (unsigned long)&tss;
+    unsigned long limit = sizeof(tss);
+
+    g->limit_low = limit & 0xFFFF;
+    g->base_low  = base  & 0xFFFFFF;
+
+    g->base_high  = (base  & 0xFF000000) >> 24;
+    g->limit_high = (limit & 0xF0000)    >> 16;
+
+    g->accessed               = 1;
+    g->read_write             = 0;
+    g->conforming_expand_down = 0;
+    g->code                   = 1;
+    g->always_1               = 0;
+    g->DPL                    = 3;
+    g->present                = 1;
+    g->available              = 0;
+    g->always_0               = 0;
+    g->big                    = 0;
+    g->gran                   = 0;
+
+    kmemset(&tss, 0, sizeof(tss));
+
+    tss.ss0 = GDT_KERNEL_DS_SELECTOR;
+    tss.esp0 = 0; // TODO: get from kinfo
+}

arch/tss.h

@@ -0,0 +1,6 @@
+#ifndef KERNELMQ_INCLUDED_TSS
+#define KERNELMQ_INCLUDED_TSS 1
+
+void tss_write_to_gdt(void *gdt_entry);
+
+#endif