feat: added UART support with a basic kprint in kernel

wip: DTB

Kernel/CMakeLists.txt

@@ -1,5 +1,6 @@
 cmake_minimum_required(VERSION 3.10)
 project(ksOSKernel LANGUAGES ASM C)
+set(KERNEL_MODULE_NAME "Kernel")
 
 # --- Locate Swift toolchain with Embedded Swift stdlib ---
 # Priority: cmake var > env var > auto-detect
@@ -62,7 +63,11 @@ add_link_options(
     -Wl,-T,${LINKER_SCRIPT}
 )
 
-set(SWIFT_SOURCES ${CMAKE_CURRENT_SOURCE_DIR}/Source/kernel.swift)
+set(SWIFT_SOURCES 
+    ${CMAKE_CURRENT_SOURCE_DIR}/Source/kernel.swift
+    ${CMAKE_CURRENT_SOURCE_DIR}/Source/Arch/dtb.swift
+    ${CMAKE_CURRENT_SOURCE_DIR}/Source/IO/uart.swift
+)
 set(SWIFT_OBJ     ${CMAKE_CURRENT_BINARY_DIR}/kernel_swift.o)
 
 add_custom_command(
@@ -75,7 +80,7 @@ add_custom_command(
         -O
         -Xcc -fno-stack-protector
         -Xcc -I${CMAKE_CURRENT_SOURCE_DIR}/../Common
-        -import-bridging-header ${CMAKE_CURRENT_SOURCE_DIR}/Source/BridgingHeader.h
+        -import-bridging-header ${CMAKE_CURRENT_SOURCE_DIR}/Source/Support/BridgingHeader.h
         -resource-dir ${SWIFT_RESOURCE_DIR}
         -c ${SWIFT_SOURCES}
         -o ${SWIFT_OBJ}
@@ -89,17 +94,47 @@ set_source_files_properties(${SWIFT_OBJ} PROPERTIES
     GENERATED TRUE
 )
 
-add_executable(kernel.elf Source/entry.S Source/stubs.c ${SWIFT_OBJ})
+add_executable(kernel.elf Source/Arch/entry.S Source/Support/stubs.c ${SWIFT_OBJ})
 
 add_custom_command(TARGET kernel.elf POST_BUILD
     COMMAND ${LLVM_OBJCOPY} -O binary kernel.elf kernel.bin
-    COMMENT "kernel.elf -> kernel.bin"
 )
 
-# --- SourceKit-LSP: generate compile_commands.json for Swift ---
+# --- SourceKit-LSP: generate compile_commands.json for Swift (Dynamic) ---
-set(_COMMON_DIR "${CMAKE_CURRENT_SOURCE_DIR}/../Common")
+set(_BRIDGING_HEADER "${CMAKE_CURRENT_SOURCE_DIR}/Source/Support/BridgingHeader.h")
-set(_BRIDGING_HEADER "${CMAKE_CURRENT_SOURCE_DIR}/Source/BridgingHeader.h")
+
+set(SWIFT_ARGS 
+    "\"${SWIFTC}\""
+    "\"-target\"" "\"aarch64-none-none-elf\""
+    "\"-enable-experimental-feature\"" "\"Embedded\""
+    "\"-module-name\"" "\"${KERNEL_MODULE_NAME}\""
+    "\"-parse-as-library\""
+    "\"-import-bridging-header\"" "\"${_BRIDGING_HEADER}\""
+)
+foreach(_src IN LISTS SWIFT_SOURCES)
+    list(APPEND SWIFT_ARGS "\"${_src}\"")
+endforeach()
+
+string(JOIN ", " SWIFT_ARGS_JSON ${SWIFT_ARGS})
+
+set(COMPDB_ENTRIES "")
+list(LENGTH SWIFT_SOURCES _src_count)
+math(EXPR _last_idx "${_src_count} - 1")
+set(_idx 0)
+
+foreach(_src IN LISTS SWIFT_SOURCES)
+    set(_entry "  {\n    \"file\": \"${_src}\",\n    \"directory\": \"${CMAKE_CURRENT_BINARY_DIR}\",\n    \"arguments\": [${SWIFT_ARGS_JSON}]\n  }")
+    
+    if(_idx LESS _last_idx)
+        string(APPEND _entry ",\n")
+    else()
+        string(APPEND _entry "\n")
+    endif()
+    
+    string(APPEND COMPDB_ENTRIES "${_entry}")
+    math(EXPR _idx "${_idx} + 1")
+endforeach()
 
 file(GENERATE OUTPUT "${CMAKE_CURRENT_SOURCE_DIR}/compile_commands.json"
-    CONTENT "[\n  {\n    \"file\": \"${SWIFT_SOURCES}\",\n    \"directory\": \"${CMAKE_CURRENT_BINARY_DIR}\",\n    \"arguments\": [\n      \"${SWIFTC}\",\n      \"-target\", \"aarch64-none-none-elf\",\n      \"-enable-experimental-feature\", \"Embedded\",\n      \"-parse-as-library\",\n      \"-wmo\",\n      \"-O\",\n      \"-Xcc\", \"-fno-stack-protector\",\n      \"-Xcc\", \"-I${_COMMON_DIR}\",\n      \"-import-bridging-header\", \"${_BRIDGING_HEADER}\",\n      \"-resource-dir\", \"${SWIFT_RESOURCE_DIR}\",\n      \"${SWIFT_SOURCES}\"\n    ]\n  }\n]\n"
+    CONTENT "[\n${COMPDB_ENTRIES}]\n"
 )

Kernel/Source/Arch/dtb.swift

@@ -0,0 +1,81 @@
+struct FDTHeader {
+    let magic: UInt32            // 0xd00dfeed
+    let totalsize: UInt32
+    let off_dt_struct: UInt32
+    let off_dt_strings: UInt32
+    let off_mem_rsvmap: UInt32
+    let version: UInt32
+    let last_comp_version: UInt32
+    let boot_cpuid_phys: UInt32
+    let size_dt_strings: UInt32
+    let size_dt_struct: UInt32
+}
+
+struct FDTProperty {
+    let len: UInt32
+    let nameoff: UInt32
+}
+
+enum FDTToken: UInt32 {
+    case beginNode = 0x1
+    case endNode   = 0x2
+    case prop      = 0x3
+    case nop       = 0x4
+    case end       = 0x9
+}
+
+extension UInt32 {
+    var fromBe: UInt32 {
+        return self.byteSwapped
+    }
+}
+
+func alignUp(_ value: Int, to: Int) -> Int {
+    return (value + to - 1) & ~(to - 1)
+}
+
+let kFDTHeaderMagic = 0xd00dfeed
+
+func parseDTB(at pointer: UnsafeRawPointer) {
+    let header = pointer.bindMemory(to: FDTHeader.self, capacity: 1).pointee
+    guard header.magic.byteSwapped == kFDTHeaderMagic else {
+        return
+    }
+
+    let structOffset = Int(header.off_dt_struct.byteSwapped)
+    let stringOffset = Int(header.off_dt_strings.byteSwapped)
+
+    var structBase = pointer.advanced(by: structOffset)
+    let stringsBase = pointer.advanced(by: stringOffset)
+
+    var finished = false
+    while !finished {
+        let rawToken = structBase.load(as: UInt32.self).byteSwapped
+        structBase = structBase.advanced(by: 4)
+
+        if let token = FDTToken(rawValue: rawToken) {
+            switch token {
+                case .beginNode:
+                    let namePointer = structBase.assumingMemoryBound(to: UInt8.self)
+                    let name = String(cString: namePointer)
+                    let nameLength = name.utf8.count + 1
+                    structBase = structBase.advanced(by: alignUp(nameLength, to: 4))
+                case .prop:
+                    let propertyHeader = structBase.load(as: FDTProperty.self)
+                    let dataLength = Int(propertyHeader.len.byteSwapped)
+                    let nameOffset = Int(propertyHeader.nameoff.byteSwapped)
+
+                    let namePointer = stringsBase.advanced(by: nameOffset).assumingMemoryBound(to: UInt8.self)
+
+                    structBase = structBase.advanced(by: 8) // skip header
+                    structBase = structBase.advanced(by: alignUp(dataLength, to: 4)) // skip data for now
+                case .endNode:
+                    continue
+                case .nop:
+                    continue
+                case .end:
+                    finished = true
+            }
+        }
+    }
+}

Kernel/Source/BridgingHeader.h

@@ -1 +0,0 @@
-#include "bootinfo.h"

Kernel/Source/IO/uart.swift

@@ -0,0 +1,19 @@
+let kUARTBaseAddress: UInt = 0x09000000 // TODO: Make it dynamic by parsion DTB
+
+@_cdecl("putchar")
+@discardableResult func _serialPutchar(_ char: Int32) -> Int32 {
+    let uartFR: UInt = kUARTBaseAddress + 0x18// TXFF -- TRansmit FIFO Full for PL011 is 5 bit of FR reg (0x18)
+
+    while (mmio_read32(uartFR) & (1 << 5)) != 0 {
+        // i love pizza btw
+    }
+    
+    mmio_write32(UInt(kUARTBaseAddress), UInt32(char))
+    return char
+}
+
+public func kprint(_ message: StaticString) {
+    for i in 0..<message.utf8CodeUnitCount {
+        _serialPutchar(Int32(message.utf8Start[i]))
+    }
+}

Kernel/Source/Support/BridgingHeader.h

@@ -0,0 +1,10 @@
+#include "bootinfo.h"
+#include <stdint.h>
+
+static inline void mmio_write32(uintptr_t addr, uint32_t val) {
+    *(volatile uint32_t *)addr = val;
+}
+
+static inline uint32_t mmio_read32(uintptr_t addr) {
+    return *(volatile uint32_t *)addr;
+}

Kernel/Source/Support/stubs.c

@@ -1,4 +1,5 @@
 #include <stddef.h>
+#include <stdint.h>
 
 void* memmove(void* dest, const void* src, unsigned long n) {
     unsigned char* d = (unsigned char*)dest;
@@ -26,9 +27,6 @@ void* memset(void* dest, int c, unsigned long n) {
 long __stack_chk_guard = (long)0xDEADBEEFCAFEBABEULL;
 void __stack_chk_fail(void) { while (1); }
 
-// Swift embedded uses putchar for print(); stub so it links but does nothing
-int putchar(int c) { return c; }
-
 // Swift runtime allocator stubs — should never be called in embedded mode
 int posix_memalign(void** ptr, unsigned long align, unsigned long size) {
     (void)ptr; (void)align; (void)size;

Kernel/Source/kernel.swift

@@ -1,7 +1,9 @@
 @_cdecl("kmain")
 public func kernelMain(_ bootInfo: UnsafeMutablePointer<Bootinfo>) {
     let fb = bootInfo.pointee.framebuffer
+
     let pixels = fb.base!
+
     let width  = Int(fb.width)
     let height = Int(fb.height)
     let total  = width * height
@@ -17,4 +19,5 @@ public func kernelMain(_ bootInfo: UnsafeMutablePointer<Bootinfo>) {
         pixels[i] = color
         i &+= 1
     }
+    kprint("Meow prrr meow nyaaa")
 }