From e2564d112ba03b432f9f44f445cbc4a3ed85751a Mon Sep 17 00:00:00 2001
From: Richard Qin <richard.qin.x@gmail.com>
Date: Fri, 17 Apr 2026 01:05:31 +0800
Subject: 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
---
 na/arch/riscv/trap/swtch.S | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)
 create mode 100644 na/arch/riscv/trap/swtch.S

(limited to 'na/arch/riscv/trap/swtch.S')

diff --git a/na/arch/riscv/trap/swtch.S b/na/arch/riscv/trap/swtch.S
new file mode 100644
index 0000000..4393505
--- /dev/null
+++ b/na/arch/riscv/trap/swtch.S
@@ -0,0 +1,40 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Copyright (C) 2026 Richard Qin */
+
+    .section .text
+    .globl context_switch
+    .align 2
+# void context_switch(Context* old_ctx, Context* next_ctx);
+# a0 = old_ctx_ptr, a1 = next_ctx_ptr
+context_switch:
+    sd ra, 0(a0)
+    sd sp, 8(a0)
+    sd s0, 16(a0)
+    sd s1, 24(a0)
+    sd s2, 32(a0)
+    sd s3, 40(a0)
+    sd s4, 48(a0)
+    sd s5, 56(a0)
+    sd s6, 64(a0)
+    sd s7, 72(a0)
+    sd s8, 80(a0)
+    sd s9, 88(a0)
+    sd s10, 96(a0)
+    sd s11, 104(a0)
+
+    ld ra, 0(a1)
+    ld sp, 8(a1)
+    ld s0, 16(a1)
+    ld s1, 24(a1)
+    ld s2, 32(a1)
+    ld s3, 40(a1)
+    ld s4, 48(a1)
+    ld s5, 56(a1)
+    ld s6, 64(a1)
+    ld s7, 72(a1)
+    ld s8, 80(a1)
+    ld s9, 88(a1)
+    ld s10, 96(a1)
+    ld s11, 104(a1)
+
+    ret
\ No newline at end of file
-- 
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