add tss

1 files changed, 80 insertions, 0 deletions

diff --git a/kernel/cpu/tss.c b/kernel/cpu/tss.c
new file mode 100644
index 0000000..bda713b
--- /dev/null
+++ b/kernel/cpu/tss.c
@@ -0,0 +1,80 @@
+#include "lib/kstring.h"
+#include <stdint.h>
+
+#include "tss.h"
+
+struct sys_seg_descriptor {
+	uint64_t limit0_15 : 16;
+	uint64_t base0_15 : 16;
+	uint64_t base16_23 : 8;
+	uint64_t type : 4;
+	uint64_t : 1;
+	uint64_t DPL : 2;
+	uint64_t present : 1;
+	uint64_t limit16_19: 4;
+	uint64_t available : 1;
+	uint64_t : 1;
+	uint64_t : 1;
+	uint64_t gran : 1;
+	uint64_t base24_31 : 8;
+	uint64_t base32_63 : 32;
+	uint64_t : 32;
+} __attribute__((packed));
+
+struct tss {
+	uint64_t : 32;
+	uint64_t rsp0 : 64;
+	uint64_t rsp1 : 64;
+	uint64_t rsp2 : 64;
+	uint64_t : 64;
+	uint64_t ist1 : 64;
+	uint64_t ist2 : 64;
+	uint64_t ist3 : 64;
+	uint64_t ist4 : 64;
+	uint64_t ist5 : 64;
+	uint64_t ist6 : 64;
+	uint64_t ist7 : 64;
+	uint64_t : 64;
+	uint64_t : 16;
+	uint64_t iopb : 16;
+} __attribute__((packed));
+
+// tss entry
+static volatile struct tss tss;
+
+// gdt entries
+extern volatile uint8_t GDT[];
+static volatile struct sys_seg_descriptor *GDT_TSS;
+
+// kernel stack pointer
+extern char kern_stack_end[];
+
+void tss_init(void) {
+	uint64_t base = (uint64_t) &tss;
+	uint64_t limit = sizeof tss - 1;
+
+	// setup tss entry
+	memsetv(&tss, 0, sizeof(struct tss));
+	tss.rsp0 = (uint64_t) kern_stack_end;
+
+	// map tss into gdt
+	GDT_TSS = (volatile struct sys_seg_descriptor *) (GDT + 0x28);
+	memsetv(GDT_TSS, 0, sizeof(struct sys_seg_descriptor));
+	GDT_TSS->limit0_15 = limit & 0xFFFF;
+	GDT_TSS->base0_15 = base & 0xFFFF;
+	GDT_TSS->base16_23 = (base >> 16) & 0xFF;
+	GDT_TSS->type = 0x9;
+	GDT_TSS->DPL = 0;
+	GDT_TSS->present = 1;
+	GDT_TSS->limit16_19 = (limit >> 16) & 0xF;
+	GDT_TSS->available = 0;
+	GDT_TSS->gran = 0;
+	GDT_TSS->base24_31 = (base >> 24) & 0xFF;
+	GDT_TSS->base32_63 = (base >> 32) & 0xFFFFFFFF;
+
+	tss_flush();
+}
+
+void tss_set_stack(uint64_t stack) {
+	tss.rsp0 = stack;
+}