From 6dd868b2919c594760d6cb671c859c1d35f12f2b Mon Sep 17 00:00:00 2001
From: Richard Qin <richard.qin.x@gmail.com>
Date: Wed, 13 May 2026 16:25:25 +0800
Subject: feat: implement syscall dispatcher and initialization for system
 calls

---
 na/kernel/syscall.cc | 99 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 99 insertions(+)
 create mode 100644 na/kernel/syscall.cc

diff --git a/na/kernel/syscall.cc b/na/kernel/syscall.cc
new file mode 100644
index 0000000..4dfbb5d
--- /dev/null
+++ b/na/kernel/syscall.cc
@@ -0,0 +1,99 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Copyright (C) 2026 Richard Qin */
+
+/*
+ * System Call MI Layer — Jump Table & Dispatcher
+ *
+ * O(1) function pointer array dispatch. No switch-case.
+ * syscall_init() registers all implemented handlers.
+ *
+ * Reference: docs/specs/syscall.md §6
+ */
+
+#include <lume/syscall.h>
+#include <lume/syscall_nr.h>
+#include <lume/errno.h>
+#include <lume/kprintf.h>
+#include <lume/klog.h>
+
+/* ======================================================================
+ * Jump table
+ * ====================================================================== */
+
+inline constexpr int kNrSyscalls = 512;
+
+static SyscallHandler sys_call_table[kNrSyscalls];
+
+/* ======================================================================
+ * MI Dispatcher
+ * ====================================================================== */
+
+int64 syscall_dispatch(uint64 nr, uint64 args[6])
+{
+    if (nr >= static_cast<uint64>(kNrSyscalls))
+        return -ENOSYS;
+
+    SyscallHandler handler = sys_call_table[nr];
+    if (!handler)
+        return -ENOSYS;
+
+    return handler(args[0], args[1], args[2],
+                   args[3], args[4], args[5]);
+}
+
+/* ======================================================================
+ * Forward declarations of sys_* handlers
+ * ====================================================================== */
+
+/* sys_process.cc */
+int64 sys_exit(uint64, uint64, uint64, uint64, uint64, uint64);
+int64 sys_exit_group(uint64, uint64, uint64, uint64, uint64, uint64);
+int64 sys_getpid(uint64, uint64, uint64, uint64, uint64, uint64);
+int64 sys_gettid(uint64, uint64, uint64, uint64, uint64, uint64);
+int64 sys_getppid(uint64, uint64, uint64, uint64, uint64, uint64);
+int64 sys_sched_yield_wrapper(uint64, uint64, uint64, uint64, uint64, uint64);
+int64 sys_clone_wrapper(uint64, uint64, uint64, uint64, uint64, uint64);
+int64 sys_wait4_wrapper(uint64, uint64, uint64, uint64, uint64, uint64);
+int64 sys_set_tid_address(uint64, uint64, uint64, uint64, uint64, uint64);
+int64 sys_getuid(uint64, uint64, uint64, uint64, uint64, uint64);
+int64 sys_getgid(uint64, uint64, uint64, uint64, uint64, uint64);
+
+/* sys_mm.cc */
+int64 sys_brk(uint64, uint64, uint64, uint64, uint64, uint64);
+int64 sys_mmap(uint64, uint64, uint64, uint64, uint64, uint64);
+int64 sys_munmap(uint64, uint64, uint64, uint64, uint64, uint64);
+int64 sys_mprotect(uint64, uint64, uint64, uint64, uint64, uint64);
+
+/* sys_info.cc */
+int64 sys_uname(uint64, uint64, uint64, uint64, uint64, uint64);
+
+/* ======================================================================
+ * syscall_init — register all handlers
+ * ====================================================================== */
+
+void syscall_init()
+{
+    /* Zero the table (redundant for BSS, but explicit) */
+    for (int i = 0; i < kNrSyscalls; i++)
+        sys_call_table[i] = nullptr;
+
+    /* Phase 2: minimal runnable set */
+    sys_call_table[SYS_exit]            = sys_exit;
+    sys_call_table[SYS_exit_group]      = sys_exit_group;
+    sys_call_table[SYS_getpid]          = sys_getpid;
+    sys_call_table[SYS_gettid]          = sys_gettid;
+    sys_call_table[SYS_getppid]         = sys_getppid;
+    sys_call_table[SYS_sched_yield]     = sys_sched_yield_wrapper;
+    sys_call_table[SYS_clone]           = sys_clone_wrapper;
+    sys_call_table[SYS_wait4]           = sys_wait4_wrapper;
+    sys_call_table[SYS_set_tid_address] = sys_set_tid_address;
+    sys_call_table[SYS_getuid]          = sys_getuid;
+    sys_call_table[SYS_getgid]          = sys_getgid;
+    sys_call_table[SYS_brk]             = sys_brk;
+    sys_call_table[SYS_mmap]            = sys_mmap;
+    sys_call_table[SYS_munmap]          = sys_munmap;
+    sys_call_table[SYS_mprotect]        = sys_mprotect;
+    sys_call_table[SYS_uname]           = sys_uname;
+
+    printk(KERN_INFO "init: syscall_init done (16 handlers registered)\n");
+}
-- 
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