Load TSS

src/kernel/cpu/cpu.c

@@ -1,11 +1,12 @@
 #include <cpu.h>
 #include <interrupts.h>
 
-uint64_t gdt[2];
+uint64_t gdt[5];
-void gdt_init(uint64_t *);
+uint8_t tss[104];
+void gdt_init(uint64_t *, void *);
 
 void cpu_init()
 {
   interrupt_init();
-  gdt_init(gdt);
+  gdt_init(gdt, tss);
 }

src/kernel/cpu/gdt.c

@@ -6,11 +6,11 @@
 #define GDT_DPL(lvl)  ((lvl)<<13)
 #define GDT_PRESENT   (1<<15)
 #define GDT_LONG      (1<<21)
-
+#define GDT_TSS       (1<<8)
 
 struct gdt
 {
-  uint32_t _;
+  uint32_t addr;
   uint32_t flags;
 }__attribute__((packed));
 
@@ -20,21 +20,53 @@ struct gdtp
   struct gdt *gdt;
 }__attribute__((packed));
 
+struct tss
+{
+  uint32_t r1;
+  uint64_t rsp0;
+  uint64_t rsp1;
+  uint64_t rsp2;
+  uint64_t r2;
+  uint64_t ist1;
+  uint64_t ist2;
+  uint64_t ist3;
+  uint64_t ist4;
+  uint64_t ist5;
+  uint64_t ist6;
+  uint64_t ist7;
+  uint64_t r3;
+  uint16_t r4;
+  uint16_t io_mba;
+}__attribute__((packed));
+
 
 struct gdt BootGDT[] = {
   {0, 0},
-  {0, GDT_PRESENT | GDT_DPL(0) | GDT_CODE | GDT_LONG}
+  {0, GDT_PRESENT | GDT_DPL(0) | GDT_CODE | GDT_LONG},
+  {0, GDT_PRESENT | GDT_DPL(3) | GDT_CODE | GDT_LONG},
+  {0, 0},
+  {0, 0},
 };
 
 struct gdtp GDTp = {2*8-1, BootGDT};
 
 
-void gdt_init(uint64_t *_gdt)
+void gdt_init(uint64_t *_gdt, void *_tss)
 {
   struct gdt *gdt = (struct gdt *)_gdt;
   memcpy(gdt, BootGDT, sizeof(BootGDT));
 
-  GDTp.len = 2*8 - 1;
+  uint32_t tss_limit = sizeof(struct tss);
+  uint64_t tss_base = (uint64_t)_tss;
+  gdt[3].flags = GDT_PRESENT | GDT_TSS;
+  gdt[3].flags |= (((tss_base >> 24) & 0xFF) << 24);
+  gdt[3].flags |= ((tss_base >> 16) & 0xFF);
+  gdt[3].flags |= (((tss_limit >> 16) & 0xF) << 16);
+  gdt[3].addr = ((tss_base & 0xFFFF) << 16) | (tss_limit & 0xFFFF);
+  gdt[4].flags = 0;
+  gdt[4].addr = ((tss_base >> 32) & 0xFFFF);
+
+  GDTp.len = 5*8 - 1;
   GDTp.gdt = gdt;
 
   load_gdt(&GDTp);

src/kernel/cpu/registers.S

@@ -17,6 +17,8 @@ load_gdt:
   push rax
   retfq
 .load_gdt:
+  mov rax, 0x18
+  ltr ax
   ret
 
 .global read_cr0