1 files changed, 80 insertions, 0 deletions
diff --git a/sys/include/arch/amd64/gdt.h b/sys/include/arch/amd64/gdt.h
new file mode 100644
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+++ b/sys/include/arch/amd64/gdt.h
@@ -0,0 +1,80 @@
+/*
+ * Copyright (c) 2023 Ian Marco Moffett and the VegaOS team.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of VegaOS nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/* $Id$ */
+
+#ifndef AMD64_GDT_H_
+#define AMD64_GDT_H_
+
+#include <sys/types.h>
+#include <sys/cdefs.h>
+
+#define GDT_TSS 5
+#define KERNEL_CS 0x8
+#define KERNEL_DS 0x10
+
+struct __packed gdt_entry {
+    uint16_t limit;
+    uint16_t base_low;
+    uint8_t base_mid;
+    uint8_t access;
+    uint8_t granularity;
+    uint8_t base_hi;
+};
+
+struct __packed gdtr {
+    uint16_t limit;
+    uintptr_t offset;
+};
+
+static inline void
+gdt_load(struct gdtr *gdtr)
+{
+        __asm("lgdt %0\n"
+              "push $8\n"               /* Push CS */
+              "lea 1f(%%rip), %%rax\n"  /* Load 1 label address into RAX */
+              "push %%rax\n"            /* Push the return address (label 1) */
+              "lretq\n"                 /* Far return to update CS */
+              "1:\n"
+              "  mov $0x10, %%eax\n"
+              "  mov %%eax, %%ds\n"
+              "  mov %%eax, %%es\n"
+              "  mov %%eax, %%fs\n"
+              "  mov %%eax, %%gs\n"
+              "  mov %%eax, %%ss\n"
+              :
+              : "m" (*gdtr)
+              : "rax", "memory"
+        );
+}
+
+extern struct gdt_entry g_dmmy_gdt[256];
+extern struct gdtr g_early_gdtr;
+
+#endif  /* !AMD64_GDT_H_ */