From c3485d4ac1b4b8a5ee3d7435400bf768ca0ff565 Mon Sep 17 00:00:00 2001
From: Richard Qin <richard.qin.x@gmail.com>
Date: Wed, 13 May 2026 16:30:54 +0800
Subject: feat: add self-tests for uaccess functionality

---
 na/test/test_uaccess.cc | 97 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 97 insertions(+)
 create mode 100644 na/test/test_uaccess.cc

diff --git a/na/test/test_uaccess.cc b/na/test/test_uaccess.cc
new file mode 100644
index 0000000..d5795fc
--- /dev/null
+++ b/na/test/test_uaccess.cc
@@ -0,0 +1,97 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Copyright (C) 2026 Richard Qin */
+
+#include <lume/selftest.h>
+#include <lume/uaccess.h>
+#include <lume/errno.h>
+
+#include <lume/vmm.h>
+#include <lume/pmm.h>
+#include <arch/pmap.h>
+
+constexpr uint64 kKernelVABase = 0xFFFFFFC000000000ULL;
+
+void selftest_uaccess()
+{
+    /* To test valid user addresses (< kKernelVABase), we need a writable page mapped there.
+     * We cannot use VmSpace::create() because it does not yet inherit kernel mappings, 
+     * so switching to it hangs. We also cannot map it with the U bit because S-mode 
+     * would need the SUM bit enabled.
+    * So we manually allocate a physical page and map it into the CURRENT page table 
+     * at 0x100000 without the U bit, just for this test.
+     */
+    uint64 mock_user_addr = 0x100000;
+    
+    uint64 satp;
+    asm volatile("csrr %0, satp" : "=r"(satp));
+    uint64 root_pa = (satp & 0xFFFFFFFFFFFULL) << 12;
+    
+    Page* page = pmm_alloc_page();
+    ST_ASSERT(page != nullptr);
+    uint64 paddr = page_to_pa(page).raw;
+    
+    pmap::map(root_pa, mock_user_addr, paddr, pmap::PTE_R | pmap::PTE_W | pmap::PTE_V | pmap::PTE_A | pmap::PTE_D);
+    
+    /* Flush TLB to see the new mapping */
+    asm volatile("sfence.vma" : : : "memory");
+
+    st_begin("uaccess: copy_to_user valid range");
+    char kernel_buf[32] = "Hello User Space!";
+    int ret = copy_to_user(mock_user_addr, kernel_buf, 18);
+    ST_ASSERT_EQ(ret, 0);
+    st_pass();
+
+    st_begin("uaccess: copy_from_user valid range");
+    char read_buf[32] = {0};
+    /* We wrote "Hello User Space!" to mock_user_addr previously */
+    ret = copy_from_user(read_buf, mock_user_addr, 18);
+    ST_ASSERT_EQ(ret, 0);
+    ST_ASSERT(read_buf[0] == 'H');
+    ST_ASSERT(read_buf[1] == 'e');
+    ST_ASSERT(read_buf[6] == 'U');
+    st_pass();
+
+    st_begin("uaccess: strncpy_from_user valid range");
+    char str_buf[32] = {0};
+    int64 len = strncpy_from_user(str_buf, mock_user_addr, 32);
+    ST_ASSERT_EQ(len, 17); /* "Hello User Space!" is 17 chars long */
+    ST_ASSERT(str_buf[0] == 'H');
+    st_pass();
+
+    st_begin("uaccess: strncpy_from_user max_len truncation");
+    char trunc_buf[32] = {0};
+    len = strncpy_from_user(trunc_buf, mock_user_addr, 6);
+    ST_ASSERT_EQ(len, 5); /* Will copy 5 chars and NUL terminate */
+    ST_ASSERT(trunc_buf[4] == 'o');
+    ST_ASSERT(trunc_buf[5] == '\0');
+    st_pass();
+
+    st_begin("uaccess: copy_to_user invalid range (crosses boundary)");
+    ret = copy_to_user(kKernelVABase - 10, kernel_buf, 20);
+    ST_ASSERT_EQ(ret, -EFAULT);
+    st_pass();
+
+    st_begin("uaccess: copy_to_user invalid range (entirely in kernel)");
+    ret = copy_to_user(kKernelVABase + 0x1000, kernel_buf, 20);
+    ST_ASSERT_EQ(ret, -EFAULT);
+    st_pass();
+
+    st_begin("uaccess: copy_to_user invalid range (overflow)");
+    ret = copy_to_user(0xFFFFFFFFFFFFFFF0ULL, kernel_buf, 0x100);
+    ST_ASSERT_EQ(ret, -EFAULT);
+    st_pass();
+
+    st_begin("uaccess: copy_from_user invalid ranges");
+    ret = copy_from_user(read_buf, kKernelVABase - 5, 10);
+    ST_ASSERT_EQ(ret, -EFAULT);
+    
+    ret = copy_from_user(read_buf, kKernelVABase, 10);
+    ST_ASSERT_EQ(ret, -EFAULT);
+    st_pass();
+
+    st_begin("uaccess: strncpy_from_user invalid range");
+    uint64 invalid_addr = kKernelVABase + 0x1000;
+    len = strncpy_from_user(str_buf, invalid_addr, 10);
+    ST_ASSERT_EQ(len, -EFAULT);
+    st_pass();
+}
-- 
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