tasking: switch tss.esp0 on switching process

src/kernel/gdt.c

@@ -4,6 +4,13 @@
 
 struct tss_entry_struct tss;
 
+struct seg_desc gdt[NR_GDT_ENTRIES];
+
+struct desc_r gdtr = {
+	sizeof(gdt) - 1,
+	(uint32_t)&gdt
+};
+
 void bss_init()
 {
 	memset((void *)((int)_edata), 0, KERNEL_BSS_SIZE);

src/tasking/task.c

@@ -3,6 +3,7 @@
 #include "../include/paging.h"
 #include "../include/string.h"
 #include "../include/liballoc.h"
+#include "../include/gdt.h"
 
 #include <stddef.h>
 
@@ -145,6 +146,7 @@ void schedule() {
     }
 
     if (next && next != current) {
+        tss.esp0 = next->kesp;
         switchProcess(next);
     }