kernel/amd64: Add Task State Segment

Signed-off-by: Ian Moffett <ian@osmora.org>

1 files changed, 82 insertions, 0 deletions

diff --git a/sys/arch/amd64/tss.c b/sys/arch/amd64/tss.c
new file mode 100644
index 0000000..3463291
--- /dev/null
+++ b/sys/arch/amd64/tss.c
@@ -0,0 +1,82 @@
+/*
+ * Copyright (c) 2023 Ian Marco Moffett and the Osmora 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 Hyra 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.
+ */
+
+#include <machine/tss.h>
+#include <machine/cpu.h>
+#include <lib/string.h>
+#include <vm/dynalloc.h>
+#include <sys/panic.h>
+
+__MODULE_NAME("TSS");
+__KERNEL_META("$Hyra$: tss.c, Ian Marco Moffett, "
+              "AMD64 Task state segment code");
+
+static void
+alloc_resources(struct cpu_info *cpu)
+{
+    struct tss_entry *tss;
+
+    /*
+     * Allocate TSS entries for this CPU
+     */
+    if (cpu->tss == NULL) {
+        /* Allocate a TSS for this CPU */
+        tss = dynalloc(sizeof(*tss));
+        if (tss == NULL)
+            panic("Failed to alloc %d bytes for TSS\n", sizeof(*tss));
+        memset(tss, 0, sizeof(*tss));
+        cpu->tss = tss;
+    }
+}
+
+void
+write_tss(struct cpu_info *cpu, struct tss_desc *desc)
+{
+    uintptr_t tss_base;
+
+    alloc_resources(cpu);
+
+    tss_base = (uintptr_t)cpu->tss;
+
+    /*
+     * XXX: The AVL (Available for use by system software)
+     *      bit is ignored by hardware and it is up to us
+     *      to decide how to use it... As of now, it is useless
+     *      to us and shall remain 0.
+     */
+    desc->p = 1;        /* Must be present to be valid! */
+    desc->g = 0;        /* Granularity -> 0 */
+    desc->avl = 0;      /* Not used */
+    desc->dpl = 0;      /* Descriptor Privilege Level -> 0 */
+    desc->type = 0x9;   /* For TSS -> 0x9 (0b1001) */
+
+    desc->base_lo16 = __SHIFTOUT(tss_base, __MASK(16));
+    desc->base_mid24 = __SHIFTOUT(tss_base, __MASK(8) << 24);
+    desc->base_mid32 = __SHIFTOUT(tss_base, __MASK(32) << 32);
+}