kern/amd64: Add interrupt descriptor table core

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

2 files changed, 172 insertions, 0 deletions

diff --git a/src/sys/arch/amd64/intel/idt.c b/src/sys/arch/amd64/intel/idt.c
new file mode 100644
index 0000000..62a9de2
--- /dev/null
+++ b/src/sys/arch/amd64/intel/idt.c
@@ -0,0 +1,73 @@
+/*
+ * Copyright (c) 2025 Ian Marco Moffett and L5 engineers
+ * 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 the project 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.
+ */
+
+/*
+ * Description: Interrupt descriptor table core
+ * Author: Ian Marco Moffett
+ */
+
+#include <sys/types.h>
+#include <machine/idt.h>
+#include <machine/gdt.h>
+
+static struct idt_entry idt[256];
+static struct idtr idtr = {
+    .limit  = sizeof(struct idt_entry) * 256 - 1,
+    .offset = (uintptr_t)&idt[0]
+};
+
+void
+idt_set_desc(uint8_t vector, uint8_t type, uintptr_t isr, uint8_t ist)
+{
+    struct idt_entry *desc;
+
+    if (vector >= 255) {
+        /* Invalid vector */
+        return;
+    }
+
+    desc = &idt[vector];
+    desc->off_low = isr & 0xFFFF;
+    desc->off_mid = (isr >> 16) & 0xFFFF;
+    desc->off_high = (isr >> 32) & 0xFFFFFFFF;
+    desc->segsel = KERNEL_CS;
+    desc->type = type;
+    desc->dpl = (type == IDT_USER_GATE) ? 3 : 0;
+    desc->p = 1;
+    desc->zero = 0;
+    desc->zero1 = 0;
+    desc->reserved = 0;
+    desc->ist = ist;
+}
+
+void
+idt_load(void)
+{
+    __ASMV("lidt %0" :: "m" (idtr) : "memory");
+}
diff --git a/src/sys/include/arch/amd64/idt.h b/src/sys/include/arch/amd64/idt.h
new file mode 100644
index 0000000..132550c
--- /dev/null
+++ b/src/sys/include/arch/amd64/idt.h
@@ -0,0 +1,99 @@
+/*
+ * Copyright (c) 2025 Ian Marco Moffett and L5 engineers
+ * 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 the project 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.
+ */
+
+#ifndef _MACHINE_IDT_H_
+#define _MACHINE_IDT_H_ 1
+
+#include <sys/types.h>
+#include <sys/cdefs.h>
+
+#define IDT_INT_GATE    0x8E
+#define IDT_TRAP_GATE   0x8F
+#define IDT_USER_GATE   0xEE
+
+#define ISR(p) ((uintptr_t)p)
+
+/*
+ * Represents a single interrupt/trap gate entry
+ * within the interrupt descriptor table
+ *
+ * @off_low: Low 16 bits of ISR offset
+ * @segsel: Expected code segment upon ISR entry
+ * @ist: Interrupt stack table
+ * @zero: [UNUSED] keep zero
+ * @type: Gate type
+ * @zero1: Same as `zero'
+ * @dpl: Descriptor privilege level
+ * @p: Present (1=valid)
+ * @off_mid: Middle offset bits of ISR entry
+ * @off_high: High offset bits of ISR entry
+ * @reserved: [RESERVED] keep zero
+ */
+struct __packed idt_entry {
+    uint16_t off_low;
+    uint16_t segsel;
+    uint8_t ist : 3;
+    uint8_t zero : 5;
+    uint8_t type : 4;
+    uint8_t zero1 : 1;
+    uint8_t dpl : 2;
+    uint8_t p : 1;
+    uint16_t off_mid;
+    uint32_t off_high;
+    uint32_t reserved;
+};
+
+/*
+ * Represents the IDT register that points to the
+ * base and limit of the Interrupt Descriptor Table.
+ *
+ * @limit: Limit of the IDT structure
+ * @offset: Base offset of IDT structure
+ */
+struct __packed idtr {
+    uint16_t limit;
+    uintptr_t offset;
+};
+
+/*
+ * Set an entry in the interrupt descriptor table
+ *
+ * @vector: Vector of entry to set
+ * @type: Interrupt gate type
+ * @isr: Interrupt service routine entrypoint
+ * @ist: Interrupt stack table index
+ */
+void idt_set_desc(uint8_t vector, uint8_t type, uintptr_t isr, uint8_t ist);
+
+/*
+ * Load the interrupt descriptor table
+ */
+void idt_load(void);
+
+#endif  /* !_MACHINE_IDT_H_ */