x86_64: implement TSS initialisation and user/kernel stack pointer switching

arch/x86_64/cpu.c

@@ -1,11 +1,14 @@
-#include <mango/machine/cpu.h>
 #include <arch/msr.h>
+#include <mango/machine/cpu.h>
 
 int ml_cpu_block_init(ml_cpu_block *p)
 {
 	p->c_this = p;
 	gdt_init(&p->c_gdt, &p->c_gdt_ptr);
 	idt_init(&p->c_idt_ptr);
+	tss_init(&p->c_tss, &p->c_tss_ptr);
+
+	gdt_write_tss(&p->c_gdt, &p->c_tss);
 	return 0;
 }
 
@@ -13,6 +16,27 @@ int ml_cpu_block_use(ml_cpu_block *p)
 {
 	gdt_load(&p->c_gdt_ptr);
 	idt_load(&p->c_idt_ptr);
+	tss_load(&p->c_tss);
 	wrmsr(MSR_GS_BASE, (uint64_t)p);
 	return 0;
 }
+
+virt_addr_t ml_cpu_block_get_kstack(ml_cpu_block *p)
+{
+	return tss_get_kstack(&p->c_tss);
+}
+
+virt_addr_t ml_cpu_block_get_ustack(ml_cpu_block *p)
+{
+	return tss_get_ustack(&p->c_tss);
+}
+
+void ml_cpu_block_set_kstack(ml_cpu_block *p, virt_addr_t sp)
+{
+	tss_set_kstack(&p->c_tss, sp);
+}
+
+void ml_cpu_block_set_ustack(ml_cpu_block *p, virt_addr_t sp)
+{
+	tss_set_ustack(&p->c_tss, sp);
+}