.sourcekit-lsp/config.json

@@ -1,8 +0,0 @@
-{
-  "defaultWorkspaceType": "compilationDatabase",
-  "compilationDatabase": {
-    "searchPaths": [".", "Kernel"]
-  },
-  "backgroundIndexing": true,
-  "backgroundPreparationMode": "enabled"
-}

Kernel/CMakeLists.txt

@@ -5,6 +5,7 @@ set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 file(GLOB_RECURSE KERNEL_SOURCES CMAKE_CONFIGURE_DEPENDS 
     ${CMAKE_CURRENT_SOURCE_DIR}/Source/KernelMain.c
     ${CMAKE_CURRENT_SOURCE_DIR}/Source/Arch/entry.S
+#    ${CMAKE_CURRENT_SOURCE_DIR}/Source/IO/*.c
     ${CMAKE_CURRENT_SOURCE_DIR}/Source/**/*.c
 )
 

Kernel/Include/Arch/CPU.h

@@ -0,0 +1,9 @@
+#pragma once
+
+static inline void CPUYield() {
+    __asm__ volatile ("yield" ::: "memory");
+}
+
+static inline void CPUWaitForInterrupt() {
+    __asm__ volatile ("wfi" ::: "memory");
+}

Kernel/Include/Arch/IO.h

@@ -0,0 +1,14 @@
+#pragma once
+#include <types.h>
+
+static inline void IOAddressWrite32(UInt64 address, UInt32 value) {
+    __asm__ volatile ("dsb sy" ::: "memory"); // wait till all previous writes are finished physically
+    *(volatile UInt32*)address = value;
+    __asm__ volatile ("dsb sy" ::: "memory"); // wait till my write is finished physically
+}
+
+static inline UInt32 IOAddressRead32(UInt64 address) {
+    UInt32 value = *(volatile UInt32*)address;
+    __asm__ volatile ("dsb ld" ::: "memory"); // wait till my read is finished physically
+    return value;
+}

Kernel/Include/IO/IOSerial.h

@@ -0,0 +1,9 @@
+#pragma once
+#include <types.h>
+
+enum {
+    kUARTBaseAddress = 0x09000000, // TODO: make it dynamic by parsing DTB
+};
+
+Int32 IOSerialPutCharacter(ASCII character);
+Int32 IOSerialPutString(const ASCII* string);

Kernel/Include/types.h

@@ -7,12 +7,18 @@ typedef unsigned char      UInt8;
 typedef unsigned short     UInt16;
 typedef unsigned int       UInt32;
 typedef unsigned long long UInt64; 
+typedef unsigned long long UInt;
+
+typedef UInt Address;
+typedef UInt8* BytePointer;
+typedef UInt8* MemoryPointer;
 
 typedef signed char        Int8;
 typedef signed short       Int16;
 typedef signed int         Int32;
 typedef signed long long   Int64;
+typedef int Int;
 
 typedef UInt64 Size;
-
+typedef char ASCII;
 

Kernel/Source/IO/IOSerial.c

@@ -0,0 +1,25 @@
+#include <IO/IOSerial.h>
+#include <Arch/IO.h>
+#include <Arch/CPU.h>
+
+Int32 IOSerialPutCharacter(ASCII character) {
+    // TXFF -- TRansmit FIFO Full for PL011 is 5 bit of FR reg (0x18)
+    UInt64 uartFR = kUARTBaseAddress + 0x18; 
+
+    while ((IOAddressRead32(uartFR) & (1 << 5)) != 0)  {
+        CPUYield();
+    }
+
+    IOAddressWrite32(kUARTBaseAddress, character);
+    return character;
+}
+
+Int32 IOSerialPutString(const ASCII* string) {
+    Int i = 0;
+    while (string[i] != '\0') {
+        IOSerialPutCharacter(string[i]);
+        i++;
+    }
+
+    return i;
+}

Kernel/Source/KernelMain.c

@@ -1,5 +1,6 @@
-#include "types.h"
+#include <types.h>
+#include <IO/IOSerial.h>
 
 void KernelMain(void) {
-    volatile UInt64 meow = 0x12345;
+    IOSerialPutString("Meow nya!!\n");
 }