feat: add initial RISC-V architecture support and core kernel functionality

- Implement MMU hardware primitives for RISC-V SV39 in mmu.h
- Create trap vector control primitives in trap.h
- Define trap frame structure for RISC-V in trapframe.h
- Add assembly routines for context switching in swtch.S
- Implement trap vector entry/exit in trap_vector.S
- Introduce basic error number definitions in errno.h
- Provide placement new/delete operators in new.h
- Define kernel panic handler in panic.h and implement in panic.cc
- Establish basic type definitions in types.h
- Create the kernel main entry point in main.cc with global initialization
- Add synchronization primitives using spinlocks in spinlock.h and spinlock.cc
- Define per-CPU state tracking for interrupts in cpu_state.h
- Create a linker script for the kernel in linker.ld
- Update module makefiles for kernel and library components

4 files changed, 116 insertions, 0 deletions

diff --git a/na/include/lume/errno.h b/na/include/lume/errno.h
new file mode 100644
index 0000000..e0786ce
--- /dev/null
+++ b/na/include/lume/errno.h
@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2026 Richard Qin */
+/* from linux kernel linux/include/uapi/asm-generic/errno-base.h*/
+
+#ifndef _ASM_GENERIC_ERRNO_BASE_H
+#define _ASM_GENERIC_ERRNO_BASE_H
+
+#define	EPERM		 1	/* Operation not permitted */
+#define	ENOENT		 2	/* No such file or directory */
+#define	ESRCH		 3	/* No such process */
+#define	EINTR		 4	/* Interrupted system call */
+#define	EIO		 5	/* I/O error */
+#define	ENXIO		 6	/* No such device or address */
+#define	E2BIG		 7	/* Argument list too long */
+#define	ENOEXEC		 8	/* Exec format error */
+#define	EBADF		 9	/* Bad file number */
+#define	ECHILD		10	/* No child processes */
+#define	EAGAIN		11	/* Try again */
+#define	ENOMEM		12	/* Out of memory */
+#define	EACCES		13	/* Permission denied */
+#define	EFAULT		14	/* Bad address */
+#define	ENOTBLK		15	/* Block device required */
+#define	EBUSY		16	/* Device or resource busy */
+#define	EEXIST		17	/* File exists */
+#define	EXDEV		18	/* Cross-device link */
+#define	ENODEV		19	/* No such device */
+#define	ENOTDIR		20	/* Not a directory */
+#define	EISDIR		21	/* Is a directory */
+#define	EINVAL		22	/* Invalid argument */
+#define	ENFILE		23	/* File table overflow */
+#define	EMFILE		24	/* Too many open files */
+#define	ENOTTY		25	/* Not a typewriter */
+#define	ETXTBSY		26	/* Text file busy */
+#define	EFBIG		27	/* File too large */
+#define	ENOSPC		28	/* No space left on device */
+#define	ESPIPE		29	/* Illegal seek */
+#define	EROFS		30	/* Read-only file system */
+#define	EMLINK		31	/* Too many links */
+#define	EPIPE		32	/* Broken pipe */
+#define	EDOM		33	/* Math argument out of domain of func */
+#define	ERANGE		34	/* Math result not representable */
+
+#endif
\ No newline at end of file
diff --git a/na/include/lume/new.h b/na/include/lume/new.h
new file mode 100644
index 0000000..cdcacb8
--- /dev/null
+++ b/na/include/lume/new.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Copyright (C) 2026 Richard Qin */
+
+#pragma once
+
+/*
+ * Placement New for Freestanding Environments
+ *
+ * In -ffreestanding -nostdlib mode, <new> may not be available.
+ * LumeOS provides its own placement new/delete operators.
+ *
+ * Usage: g_obj = new (g_obj_buf) MyClass(args...);
+ *
+ * Reference: docs/specs/global_init.md §3.1
+ */
+
+inline void* operator new(decltype(sizeof(0)), void* ptr) noexcept { return ptr; }
+inline void  operator delete(void*, void*) noexcept {}
diff --git a/na/include/lume/panic.h b/na/include/lume/panic.h
new file mode 100644
index 0000000..6316c28
--- /dev/null
+++ b/na/include/lume/panic.h
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Copyright (C) 2026 Richard Qin */
+
+#pragma once
+
+/*
+ * Kernel Panic — fatal error handler.
+ *
+ * Prints the message (if UART is ready), disables interrupts,
+ * and enters an infinite wfi loop. Never returns.
+ *
+ * Implementation will be provided by lib/kprintf.cc or a
+ * dedicated panic module. For now this header declares the interface.
+ */
+
+extern "C" [[noreturn]] void kernel_panic(const char* msg, const char* detail = nullptr);
diff --git a/na/include/lume/types.h b/na/include/lume/types.h
new file mode 100644
index 0000000..a8440f6
--- /dev/null
+++ b/na/include/lume/types.h
@@ -0,0 +1,39 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Copyright (C) 2026 Richard Qin */
+
+#pragma once
+
+/*
+ * LumeOS Base Type Definitions
+ *
+ * All kernel code should use these types instead of
+ * stdint.h (which may not exist in freestanding mode).
+ */
+
+using uint8  = unsigned char;
+using uint16 = unsigned short;
+using uint32 = unsigned int;
+using uint64 = unsigned long long;
+
+using int8   = signed char;
+using int16  = signed short;
+using int32  = signed int;
+using int64  = signed long long;
+
+using size_t  = uint64;
+using ssize_t = int64;
+using uintptr = uint64;
+
+/* Null pointer constant */
+#ifndef nullptr
+/* C++11 and later have nullptr built-in */
+#endif
+
+/* Max CPUs supported */
+inline constexpr int kMaxCPUs = 8;
+
+/* Page size */
+inline constexpr uint64 kPageSize = 4096;
+
+/* Kernel virtual address offset */
+inline constexpr uint64 kPageOffset = 0xFFFFFFC000000000ULL;