From 4534f1da147bf28628097a19ee6440f436a682a5 Mon Sep 17 00:00:00 2001
From: Kevin Alavik <kevin@alavik.se>
Date: Fri, 30 May 2025 11:05:07 +0200
Subject: [PATCH] feat/kernel: Started on LAPIC

---
 .vscode/settings.json       |  3 ++-
 kernel/src/arch/cpu.h       |  1 +
 kernel/src/emk.c            |  2 ++
 kernel/src/sys/apic/lapic.c | 42 +++++++++++++++++++++++++++++++++++++
 kernel/src/sys/apic/lapic.h | 16 ++++++++++++++
 5 files changed, 63 insertions(+), 1 deletion(-)
 create mode 100644 kernel/src/sys/apic/lapic.c
 create mode 100644 kernel/src/sys/apic/lapic.h

diff --git a/.vscode/settings.json b/.vscode/settings.json
index ac25aab..71349dc 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -24,7 +24,8 @@
         "lapic.h": "c",
         "spinlock.h": "c",
         "fb.h": "c",
-        "acpi.h": "c"
+        "acpi.h": "c",
+        "madt.h": "c"
     },
     "editor.formatOnPaste": true,
     "editor.formatOnSave": true,
diff --git a/kernel/src/arch/cpu.h b/kernel/src/arch/cpu.h
index e3cd47f..591e4d6 100644
--- a/kernel/src/arch/cpu.h
+++ b/kernel/src/arch/cpu.h
@@ -3,6 +3,7 @@
 #define CPU_H
 
 #include <stdnoreturn.h>
+#include <stdint.h>
 
 static inline noreturn void hlt()
 {
diff --git a/kernel/src/emk.c b/kernel/src/emk.c
index 8c41cab..0af2497 100644
--- a/kernel/src/emk.c
+++ b/kernel/src/emk.c
@@ -20,6 +20,7 @@
 #include <arch/smp.h>
 #include <sys/acpi.h>
 #include <sys/acpi/madt.h>
+#include <sys/apic/lapic.h>
 
 __attribute__((used, section(".limine_requests"))) static volatile LIMINE_BASE_REVISION(3);
 __attribute__((used, section(".limine_requests"))) static volatile struct limine_memmap_request memmap_request = {
@@ -182,6 +183,7 @@ void emk_entry(void)
 
     /* Setup APIC */
     madt_init();
+    lapic_init();
 
     /* Finished */
     log_early("%s", LOG_SEPARATOR);
diff --git a/kernel/src/sys/apic/lapic.c b/kernel/src/sys/apic/lapic.c
new file mode 100644
index 0000000..600b78e
--- /dev/null
+++ b/kernel/src/sys/apic/lapic.c
@@ -0,0 +1,42 @@
+/* EMK 1.0 Copyright (c) 2025 Piraterna */
+#include <sys/apic/lapic.h>
+#include <arch/cpu.h>
+#include <sys/acpi/madt.h>
+#include <util/log.h>
+#include <mm/vmm.h>
+#include <boot/emk.h>
+
+uint64_t lapic_msr = 0;
+volatile uint64_t *lapic_base = 0;
+
+void lapic_write(uint32_t offset, uint32_t value)
+{
+    if (!lapic_base)
+    {
+        log_early("warning: LAPIC not initialized!");
+        return;
+    }
+    volatile uint32_t *reg = (volatile uint32_t *)((uint8_t *)lapic_base + offset);
+    *reg = value;
+}
+
+uint32_t lapic_read(uint32_t offset)
+{
+    if (!lapic_base)
+    {
+        log_early("warning: LAPIC not initialized!");
+        return 0;
+    }
+    volatile uint32_t *reg = (volatile uint32_t *)((uint8_t *)lapic_base + offset);
+    uint32_t value = *reg;
+    return value;
+}
+
+void lapic_init()
+{
+    lapic_msr = rdmsr(LAPIC_BASE);
+    lapic_base = (volatile uint64_t *)(lapic_msr & ~(0xffff));
+    /* Change the lapic address that we got from MADT earlier */
+    lapic_addr = (uint64_t)lapic_base;
+    log_early("New LAPIC base: 0x%lx", lapic_base);
+}
\ No newline at end of file
diff --git a/kernel/src/sys/apic/lapic.h b/kernel/src/sys/apic/lapic.h
new file mode 100644
index 0000000..2852b8f
--- /dev/null
+++ b/kernel/src/sys/apic/lapic.h
@@ -0,0 +1,16 @@
+/* EMK 1.0 Copyright (c) 2025 Piraterna */
+#ifndef LAPIC_H
+#define LAPIC_H
+
+#include <stdint.h>
+
+#define LAPIC_BASE 0x1b
+#define LAPIC_REGOFF_LAPICID 0x20
+#define LAPIC_REGOFF_EOI 0xB0
+#define LAPIC_REGOFF_SPIV 0xF0
+
+uint32_t lapic_read(uint32_t offset);
+void lapic_write(uint32_t offset, uint32_t value);
+void lapic_init();
+
+#endif // LAPIC_H
\ No newline at end of file