arch: i386: simplifiy GDT setup

Simplify the setup and definitions of GDT/TSS entries.

Signed-off-by: Danny Holman <dholman@gymli.org>

1 files changed, 26 insertions, 0 deletions

diff --git a/arch/i386/boot/tss.c b/arch/i386/boot/tss.c
new file mode 100644
index 0000000..2edfa76
--- /dev/null
+++ b/arch/i386/boot/tss.c
@@ -0,0 +1,26 @@
+#include "tss.h"
+#include <kernel/string.h>
+
+struct tss tss_entry;
+
+uint64_t create_tss_entry(uint16_t ss0, uint32_t esp0) {
+        uint32_t base = (uint32_t)&tss_entry;
+        uint32_t limit = base + sizeof(&tss_entry);
+        uint64_t ret = create_gdt_entry(base, limit, 0xE9);
+
+        memset(&tss_entry, 0, sizeof(struct tss));
+        tss_entry.ss0 = ss0;
+        tss_entry.esp0 = esp0;
+        tss_entry.cs = 0x08;
+        tss_entry.ss = 0x13;
+        tss_entry.ds = 0x13;
+        tss_entry.es = 0x13;
+        tss_entry.fs = 0x13;
+        tss_entry.gs = 0x13;
+        tss_entry.io_offset = sizeof(struct tss) & 0xFFFF;
+        return ret;
+}
+
+void set_kernel_stack(uint32_t stack) {
+        tss_entry.esp0 = stack;
+}