feat: add linker script and common macros for RISC-V architecture

3 files changed, 163 insertions, 1 deletions

diff --git a/na/Makefile b/na/Makefile
index 6b5e84c..cc51a65 100644
--- a/na/Makefile
+++ b/na/Makefile
@@ -42,7 +42,8 @@ ARCH    := riscv
 BUILD   := build
 TARGET  := $(BUILD)/kernel.elf
 IMAGE   := $(BUILD)/kernel.bin
-LINKER_SCRIPT := linker.ld
+LDS_SRC := arch/$(ARCH)/kernel/lumeos.lds.S
+LINKER_SCRIPT := $(BUILD)/lumeos.lds
 
 # Common flags (base, before module includes)
 WARNINGS := -Wall -Wextra -Wno-unused-parameter
@@ -103,6 +104,12 @@ DEPS := $(OBJS:.o=.d)
 
 all: $(IMAGE)
 
+# Preprocess linker script template (.lds.S → .lds)
+$(LINKER_SCRIPT): $(LDS_SRC) include/lume/lumeos.lds.h
+	@echo "  LDS     $@"
+	@mkdir -p $(dir $@)
+	@$(CC) -E -P -x c $(INCLUDES) $< -o $@
+
 # Link kernel ELF
 $(TARGET): $(OBJS) $(LINKER_SCRIPT)
 	@echo "  LD      $@"
diff --git a/na/arch/riscv/kernel/lumeos.lds.S b/na/arch/riscv/kernel/lumeos.lds.S
new file mode 100644
index 0000000..f47fef2
--- /dev/null
+++ b/na/arch/riscv/kernel/lumeos.lds.S
@@ -0,0 +1,81 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Copyright (C) 2026 Richard Qin */
+
+/*
+ * RISC-V Kernel Linker Script Template
+ *
+ * This is a C-preprocessed linker script (.lds.S). The build system
+ * runs it through CPP to produce the final vmlinux.lds which is
+ * passed to the linker.
+ *
+ * Architecture-specific definitions:
+ *   - OUTPUT_ARCH, ENTRY
+ *   - PAGE_OFFSET, BASE_ADDRESS, PHYS_BASE
+ *   - .head.text placement
+ *   - GP anchor (__global_pointer$ for RISC-V medany)
+ *   - early_pgdir and boot stacks in .bss
+ *
+ * Common section macros come from include/lume/vmlinux.lds.h
+ *
+ * Reference: docs/specs/linker_and_entry.md
+ */
+
+#include <lume/lumeos.lds.h>
+
+/* ===== RISC-V Architecture Constants ===== */
+
+OUTPUT_ARCH(riscv)
+
+PAGE_OFFSET  = 0xFFFFFFC000000000;
+BASE_ADDRESS = 0xFFFFFFC080200000;
+PHYS_BASE    = 0x80200000;
+
+ENTRY(_start)
+
+/* ===== RISC-V: GP anchor in .data (medany model) ===== */
+#define ARCH_DATA_EXTRA                         \
+    . = ALIGN(16);                              \
+    PROVIDE(__global_pointer$ = . + 0x800);     \
+    *(.sdata .sdata.*)
+
+/* ===== RISC-V: early page table + per-CPU boot stacks in .bss ===== */
+#define ARCH_BSS_EXTRA                          \
+    /* Early page table: 4KB aligned, used by entry.S before VMM */ \
+    . = ALIGN(4096);                            \
+    early_pgdir = .;                            \
+    . += 4096;                                  \
+    /* Per-CPU boot stacks: 8KB per CPU, max 8 CPUs */              \
+    . = ALIGN(4096);                            \
+    boot_stack = .;                             \
+    . += 8192 * 8;                              \
+    boot_stack_top = .;
+
+/* ===== Layout ===== */
+
+SECTIONS {
+    . = BASE_ADDRESS;
+
+    /* .head.text: Image Header (must be at byte 0 of the kernel image) */
+    .head.text : AT(PHYS_BASE) {
+        _start = .;
+        KEEP(*(.head.text))
+    }
+
+    TEXT_SECTION
+
+    . = ALIGN(4096);
+
+    RODATA_SECTION
+
+    . = ALIGN(4096);
+
+    DATA_SECTION
+
+    . = ALIGN(4096);
+
+    BSS_SECTION
+
+    KERNEL_END
+
+    DISCARDS
+}
diff --git a/na/include/lume/lumeos.lds.h b/na/include/lume/lumeos.lds.h
new file mode 100644
index 0000000..b4a8f42
--- /dev/null
+++ b/na/include/lume/lumeos.lds.h
@@ -0,0 +1,74 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Copyright (C) 2026 Richard Qin */
+
+/*
+ * Common Linker Script Macros (Machine-Independent)
+ *
+ * Shared section definitions that every architecture must emit.
+ * Architecture-specific lumeos.lds.S files #include this header
+ * and use these macros to avoid duplicating common boilerplate.
+ *
+ * Modeled after Linux include/asm-generic/vmlinux.lds.h
+ * Reference: docs/specs/linker_and_entry.md
+ */
+
+#ifndef _LUME_LUMEOS_LDS_H
+#define _LUME_LUMEOS_LDS_H
+
+/* ===== Text Section: executable code ===== */
+#define TEXT_SECTION                         \
+    .text : AT(ADDR(.text) - PAGE_OFFSET) { \
+        _stext = .;                         \
+        *(.text .text.*)                    \
+        _etext = .;                         \
+    } = 0
+
+/* ===== Read-Only Data + C++ init_array ===== */
+#define RODATA_SECTION                              \
+    .rodata : AT(ADDR(.rodata) - PAGE_OFFSET) {     \
+        _srodata = .;                               \
+        *(.rodata .rodata.*)                        \
+        INIT_ARRAY                                  \
+        _erodata = .;                               \
+    }
+
+/* ===== C++ Global Constructor Table ===== */
+#define INIT_ARRAY          \
+    . = ALIGN(8);           \
+    __init_array_start = .; \
+    KEEP(*(.init_array .init_array.*)) \
+    __init_array_end = .;
+
+/* ===== Initialized Read-Write Data ===== */
+#define DATA_SECTION                            \
+    .data : AT(ADDR(.data) - PAGE_OFFSET) {     \
+        _sdata = .;                             \
+        *(.data .data.*)                        \
+        ARCH_DATA_EXTRA                         \
+        _edata = .;                             \
+    }
+
+/* ===== BSS: Uninitialized Data ===== */
+#define BSS_SECTION                             \
+    .bss : AT(ADDR(.bss) - PAGE_OFFSET) {       \
+        _sbss = .;                              \
+        *(.bss .bss.*)                          \
+        *(.sbss .sbss.*)                        \
+        ARCH_BSS_EXTRA                          \
+        _ebss = .;                              \
+    }
+
+/* ===== Discard Unwanted Sections ===== */
+#define DISCARDS            \
+    /DISCARD/ : {           \
+        *(.eh_frame .eh_frame_hdr) \
+        *(.note .note.*)    \
+        *(.comment)         \
+    }
+
+/* ===== Kernel Image Boundary ===== */
+#define KERNEL_END          \
+    . = ALIGN(4096);        \
+    _kernel_end = .;
+
+#endif /* _LUME_LUMEOS_LDS_H */