fix: Resolve build errors and add multi-core synchronization

.gitattributes

@@ -1,3 +1,25 @@
+# Git LFS for large media files
 *.mkv filter=lfs diff=lfs merge=lfs -text
 *.mp4 filter=lfs diff=lfs merge=lfs -text
 *.gif filter=lfs diff=lfs merge=lfs -text
+*.png filter=lfs diff=lfs merge=lfs -text
+
+# Line endings
+* text=auto eol=lf
+*.bat text eol=crlf
+
+# Binary files
+*.elf binary
+*.uf2 binary
+*.bin binary
+
+# Custom diff drivers
+*.c diff=c
+*.cpp diff=cpp
+*.h diff=c
+*.hpp diff=cpp
+*.S diff=asm
+
+# Linker scripts
+*.x text
+*.ld text

.gitignore

@@ -1 +1,44 @@
+# Build directories
 /Build/
+/build/
+/build-*/
+
+# IDE and editor files
+.vscode/*
+!.vscode/c_cpp_properties.json
+!.vscode/settings.json
+!.vscode/launch.json
+
+.idea/
+*.swp
+*.swo
+*~
+.DS_Store
+
+# Compiled binaries
+*.o
+*.elf
+*.bin
+*.uf2
+*.hex
+*.dis
+*.map
+
+# CMake artifacts
+CMakeCache.txt
+CMakeFiles/
+cmake_install.cmake
+compile_commands.json
+Makefile
+
+# Python
+__pycache__/
+*.pyc
+.env
+
+# Temporary files
+*.tmp
+*.log
+cache/
+*.cache
+.cache/

.vscode/c_cpp_properties.json

@@ -1,16 +1,29 @@
 {
     "configurations": [
         {
-            "name": "Linux",
+            "name": "Pico-OS Kernel",
             "includePath": [
-                "${workspaceFolder}/**"
+                "${workspaceFolder}",
+                "${workspaceFolder}/build/_deps/pico_sdk-src/src/common/pico_stdlib_headers/include",
+                "${workspaceFolder}/build/_deps/pico_sdk-src/src/rp2_common/hardware_base/include",
+                "${workspaceFolder}/build/_deps/pico_sdk-src/src/rp2040/hardware_structs/include",
+                "${workspaceFolder}/build/_deps/pico_sdk-src/src/rp2_common/hardware_claim/include",
+                "${workspaceFolder}/build/_deps/pico_sdk-src/src/rp2_common/hardware_sync/include",
+                "${workspaceFolder}/build/_deps/pico_sdk-src/src/rp2_common/hardware_sync_spin_lock/include",
+                "${workspaceFolder}/build/_deps/pico_sdk-src/src/rp2_common/hardware_irq/include",
+                "${workspaceFolder}/build/_deps/pico_sdk-src/src/rp2_common/pico_platform/include",
+                "${workspaceFolder}/build/generated/pico_base"
             ],
-            "defines": [],
-            "compilerPath": "/usr/bin/clang",
+            "defines": [
+                "KERNEL",
+                "PICO_BOARD=\"pico\"",
+                "PICO_RP2040=1",
+                "PICO_32BIT=1"
+            ],
+            "compilerPath": "/usr/bin/clang++",
             "cStandard": "c11",
             "cppStandard": "c++20",
-            "intelliSenseMode": "clang-arm",
-            "compileCommands": "${workspaceFolder}/Build/compile_commands.json"
+            "intelliSenseMode": "macos-clang-arm64"
         }
     ],
     "version": 4

.vscode/launch.json

@@ -0,0 +1,19 @@
+{
+    "version": "0.2.0",
+    "configurations": [
+        {
+            "name": "Cortex Debug: Attach",
+            "type": "cortex-debug",
+            "request": "attach",
+            "servertype": "openocd",
+            "executable": "${workspaceFolder}/build/Kernel.elf",
+            "configFiles": [
+                "interface/picoprobe.cfg",
+                "target/rp2040.cfg"
+            ],
+            "svdFile": "${workspaceFolder}/build/_deps/pico_sdk-src/src/rp2040/hardware_regs/rp2040.svd",
+            "runToEntryPoint": "main",
+            "cwd": "${workspaceFolder}"
+        }
+    ]
+}

CHANGELOG.md

@@ -1,3 +1,85 @@
+# Changelog
+
+## [Unreleased] - 2025-12-14
+
+### Added
+- **Final Polish Items**:
+    - `SoftwareSpinLock`: Active locking with deadlock detection and power efficiency (`wfe`/`sev`).
+    - `SoftwareMutex`: Passive locking using `HardwareSpinLock`.
+    - `WaitingThreadQueue`: For managing threads waiting on resources.
+- **Hardware Integration**:
+    - `HardwareSpinLock`: Memory-mapped spin lock support for RP2040.
+    - `sys$read`, `sys$write`: Basic system calls hooked to `ConsoleDevice`.
+    - **MPU**: Supervisor/User memory separation verified.
+- **Core Infrastructure**:
+    - `init_array`/`fini_array` support in crt0 for C++ static constructors.
+    - Stack alignment fixes to prevent hardfaults.
+    - **Exception Handling**: Implemented HardFault handler (Userland kill, Kernel panic).
+    - **Memory**: Added `allocate_eternal` for silent allocation.
+    - **QEMU**: Added launch script `Tools/run-qemu.sh`.
+
+### Refactoring & Core Improvements
+- **Kernel/StackProtector**: Implemented `init_stack_guard` using RP2040 ROSC for hardware-randomized stack canaries.
+- **Kernel/Exceptions**: Enhanced HardFault handlers with clearer register dumps and stack trace headers.
+- **Kernel/PageAllocator**: Added detailed comments on RP2040 RAM layout and Buddy System initialization.
+- **Kernel/GlobalMemoryAllocator**: Standardized mutex usage with `ScopedMutex` and added comments. Implemented dynamic heap growth.
+- **Kernel/StackWrapper**: Improved API docs and parameter naming.
+- **Tools**: Removed unstable QEMU/Renode scripts (emulation deferred).
+
+### System
+- **Synchronization**: `HardwareSpinLock` is now ISR-safe, storing/restoring interrupt state.
+- **MPU**: Setup for supervisor/user mode isolation.
+- **Build**: Linker script (`linker.ld`) enforces 8-byte alignment for stack/heap.
+- **Documentation**:
+    - Added `docs/InterruptSafety.md`.
+- **Multi-Core Support**: `Scheduler` now supports creating and scheduling threads on both cores of the RP2040. Integrated `HardwareSpinLock` for safe inter-core synchronization.
+- **Robust Data Structures**:
+    - Replaced `Std::SortedSet`'s binary search tree with a **Red-Black Tree** implementation, guaranteeing O(log n) operations.
+    - Added `m_allocated_pages` to `PageAllocator` using `SortedSet` to explicitly track allocated memory ranges.
+- **Userland Allocator**: Implemented a free-list based `malloc`/`free`/`realloc`/`calloc` in `Userland/LibC`, replacing the previous bump allocator. This allows memory reuse and reduces fragmentation.
+- `Std::Formatter` specialization for `Kernel::PageRange`.
+
+### Changed
+- Refactored `ConsoleFileHandle` to store a reference to the specific `VirtualFile` instance, fixing an issue where `stat /dev/tty` returned incorrect device information.
+- Updated `Scheduler::dump()` to correctly iterate over core-specific thread arrays.
+- Enhanced `PageAllocator::dump()` to show detailed allocation tracking.
+
+### Fixed
+- `stat /dev/tty` listing incorrect file attributes by decoupling `ConsoleFileHandle` from the singleton.
+- Compilation errors in `Std/SortedSet.hpp` related to `HashTable` compatibility (relied on strict weak ordering `<` instead of `==`).
+
+## [Unreleased] - 2025-12-12
+
+### Fixed
+- **macOS Build Compatibility**: Added `Tools/compat/elf.h` with minimal ELF definitions for macOS.
+- **Portable File I/O**: Replaced Linux-specific `memfd_create`/`copy_file_range` with ANSI C alternatives (`tmpfile`, `fread`/`fwrite`).
+- **Missing Includes**: Added `MaskedInterruptGuard.hpp` includes to `Process.cpp`, `SystemHandler.cpp`, `Loader.cpp`, `Scheduler.cpp`, and `KernelMutex.hpp`.
+- **Stack Alignment**: Fixed potential hardfaults by ensuring 8-byte stack alignment in `Thread::setup_context()` and `hand_over_to_loaded_executable()`.
+- **strlcpy Conflict**: Updated `Std/Forward.hpp` to use standard `size_t` return type.
+- **Linker Symbol Resolution**: Hardcoded RP2040 RAM boundaries in `PageAllocator.cpp` to bypass missing linker script definitions.
+- **Iterator Const Correctness**: Fixed `SortedSet::InorderIterator` comparison operators to accept const references.
+- **Test Suite**: Fixed narrowing conversion, undeclared identifiers, and string arithmetic warnings in test files.
+
+### Added
+- **C++ Static Constructors**: Implemented `preinit_array`, `init_array`, and `fini_array` calling in `Userland/LibC/sys/crt0.c`.
+- **Non-Executable Stack**: Added `.note.GNU-stack` section to `crt0.S` to silence linker warnings.
+
+### Changed
+- Refactored `HardwareSpinLock` to correct lock acquisition logic (removed infinite loop on success) and added `wfe`/`sev` instructions for power-efficient SMP synchronization.
+- Enhanced `SoftwareSpinLock` with **Deadlock Detection** (checks if core already holds the lock) and `wfe`/`sev` support.
+- Updated `.gitignore` to allow useful VSCode configuration files.
+- Removed `-lbsd` dependency from `Tools/CMakeLists.txt`.
+- Removed unsupported `-fropi`/`-frwpi` compiler flags from `Userland/CMakeLists.txt`.
+- Commented out custom `operator new`/`delete` in `GlobalMemoryAllocator.cpp` to avoid conflicts with Pico SDK.
+
+### Added
+- **VSCode Configuration**: Added `c_cpp_properties.json` for IntelliSense and `launch.json` for Cortex-Debug support.
+- **C++ Static Constructors**: Implemented `preinit_array`, `init_array`, and `fini_array` calling in `Userland/LibC/sys/crt0.c`.
+
+---
+
+## Previous Changes
+
 ### Major
 
 -   Added `AbstractLock` which is used by the new `LockGuard`.

CMakeLists.txt

@@ -1,46 +1,162 @@
+# ==============================================================================
+# PicoOS - CMake Build Configuration
+# ==============================================================================
+#
+# Build targets:
+#   - Kernel.1.elf  : Main kernel binary with debug symbols
+#   - Kernel.1.uf2  : UF2 firmware for direct flashing
+#   - Kernel.elf    : Stripped kernel for production
+#
+# Usage:
+#   mkdir build && cd build
+#   cmake .. -G Ninja
+#   ninja
+#
+# ==============================================================================
+
 cmake_minimum_required(VERSION 3.19.5)
 
+# ------------------------------------------------------------------------------
+# Build Configuration
+# ------------------------------------------------------------------------------
+
+# Export compile_commands.json for IDE support
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 
-if (NOT CMAKE_BUILD_TYPE)
-    set(CMAKE_BUILD_TYPE Debug)
+# Default to Debug build
+if(NOT CMAKE_BUILD_TYPE)
+    set(CMAKE_BUILD_TYPE Debug CACHE STRING "Build type" FORCE)
 endif()
 
+message(STATUS "Build type: ${CMAKE_BUILD_TYPE}")
+
+# ------------------------------------------------------------------------------
+# Pico SDK Setup
+# ------------------------------------------------------------------------------
+
 set(CMAKE_MODULE_PATH ${CMAKE_SOURCE_DIR}/CMake)
 find_package(Tools MODULE)
 
+# Import Pico SDK (will download if PICO_SDK_PATH not set)
 include(CMake/pico_sdk_import.cmake)
 
-project(Pico C CXX ASM)
+# ------------------------------------------------------------------------------
+# Project Definition
+# ------------------------------------------------------------------------------
+
+project(PicoOS
+    VERSION 0.4.0
+    DESCRIPTION "A microkernel-inspired OS for the Raspberry Pi Pico"
+    LANGUAGES C CXX ASM
+)
+
 set(CMAKE_C_STANDARD 11)
+set(CMAKE_C_STANDARD_REQUIRED ON)
 set(CMAKE_CXX_STANDARD 20)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
+# Initialize Pico SDK
 pico_sdk_init()
 
-# FIXME: This is mostly necessary for the SDK
-set(DISABLE_WARNINGS -Wno-unused-parameter -Wno-type-limits)
-set(DISABLE_CXX_WARNINGS -Wno-reorder -Wno-ignored-qualifiers)
+# ------------------------------------------------------------------------------
+# Compiler Options
+# ------------------------------------------------------------------------------
+
+# Warnings to suppress from Pico SDK headers (not our code)
+set(SDK_WARNINGS_OFF
+    -Wno-unused-parameter
+    -Wno-type-limits
+)
+
+set(SDK_CXX_WARNINGS_OFF
+    -Wno-reorder
+    -Wno-ignored-qualifiers
+)
 
+# Common compile options interface
 add_library(project_options INTERFACE)
-target_compile_options(project_options INTERFACE -fdiagnostics-color=always -Wall ${DISABLE_WARNINGS} -Wextra -Werror -O0)
-target_compile_options(project_options INTERFACE $<$<COMPILE_LANGUAGE:CXX>:-frtti ${DISABLE_CXX_WARNINGS}>)
-target_include_directories(project_options INTERFACE ${CMAKE_SOURCE_DIR})
+
+target_compile_options(project_options INTERFACE
+    -fdiagnostics-color=always
+    -Wall
+    -Wextra
+    -Werror
+    -O0
+    -fstack-protector-strong
+    ${SDK_WARNINGS_OFF}
+)
+
+target_compile_options(project_options INTERFACE
+    $<$<COMPILE_LANGUAGE:CXX>:
+        -frtti
+        ${SDK_CXX_WARNINGS_OFF}
+    >
+)
+
+target_include_directories(project_options INTERFACE
+    ${CMAKE_SOURCE_DIR}
+)
+
+# ------------------------------------------------------------------------------
+# Userland Applications
+# ------------------------------------------------------------------------------
 
 add_subdirectory(Userland)
 
-file(GLOB_RECURSE Kernel_SOURCES CONFIGURE_DEPENDS Kernel/*.cpp Kernel/*.S Std/*.cpp)
+# ------------------------------------------------------------------------------
+# Kernel Build
+# ------------------------------------------------------------------------------
+
+file(GLOB_RECURSE KERNEL_SOURCES CONFIGURE_DEPENDS
+    Kernel/*.cpp
+    Kernel/*.S
+    Std/*.cpp
+)
+
+add_executable(Kernel.1 ${KERNEL_SOURCES})
+
+target_link_libraries(Kernel.1
+    pico_stdlib
+    pico_bootrom
+    hardware_dma
+    project_options
+    LibEmbeddedFiles
+)
 
-add_executable(Kernel.1 ${Kernel_SOURCES})
-target_link_libraries(Kernel.1 pico_stdlib pico_bootrom hardware_dma project_options LibEmbeddedFiles)
-target_compile_definitions(Kernel.1 PRIVATE KERNEL)
+target_compile_definitions(Kernel.1 PRIVATE
+    KERNEL
+)
+
+# Use custom linker script with alignment fixes
+pico_set_linker_script(Kernel.1 ${CMAKE_CURRENT_SOURCE_DIR}/Kernel/linker.ld)
+
+# Generate .uf2, .bin, .hex outputs
 pico_add_extra_outputs(Kernel.1)
 
+# ------------------------------------------------------------------------------
+# Stripped Kernel for Production
+# ------------------------------------------------------------------------------
+
 add_custom_target(Kernel.elf ALL
     COMMAND arm-none-eabi-objcopy
         --strip-symbol=__flash_data_2
         --strip-symbol=__flash_data_3
         --strip-symbol=__flash_data_4
         --strip-symbol=__flash_data_5
         --strip-symbol=__flash_base
-    Kernel.1.elf Kernel.elf
-    DEPENDS Kernel.1)
+        Kernel.1.elf Kernel.elf
+    DEPENDS Kernel.1
+    COMMENT "Creating stripped Kernel.elf"
+)
+
+# ------------------------------------------------------------------------------
+# Summary
+# ------------------------------------------------------------------------------
+
+message(STATUS "--------------------------------------------------------------")
+message(STATUS "PicoOS v${PROJECT_VERSION}")
+message(STATUS "  Platform:    RP2040 (Raspberry Pi Pico)")
+message(STATUS "  Build type:  ${CMAKE_BUILD_TYPE}")
+message(STATUS "  C Standard:  ${CMAKE_C_STANDARD}")
+message(STATUS "  C++ Standard: ${CMAKE_CXX_STANDARD}")
+message(STATUS "--------------------------------------------------------------")