From 4252e90680a6c7591cf7bfc330e119c3952f4553 Mon Sep 17 00:00:00 2001
From: StoneDC <19905433+StoneDC@users.noreply.github.com>
Date: Thu, 29 Oct 2026 19:32:29 +0800
Subject: [PATCH] test(libc): verify bounded copy padding and write extents

---
 core/libs/prx/libc/CMakeLists.txt         | 10 +++
 core/libs/tests/GuestStrncpyProtected.cpp | 80 +++++++++++++++++++++++
 2 files changed, 90 insertions(+)
 create mode 100644 core/libs/tests/GuestStrncpyProtected.cpp

diff --git a/core/libs/prx/libc/CMakeLists.txt b/core/libs/prx/libc/CMakeLists.txt
index e4c0758f24..c2cde75bd6 100644
--- a/core/libs/prx/libc/CMakeLists.txt
+++ b/core/libs/prx/libc/CMakeLists.txt
@@ -558,6 +558,16 @@ if(BUILD_TESTING)
         set_tests_properties(guest_stdio_variadic PROPERTIES ENVIRONMENT_MODIFICATION
             "PATH=path_list_prepend:$<TARGET_FILE_DIR:libc>")
     endif()
+    add_test_executable(guest_strncpy_protected_tests ${LIBS_INCLUDE_DIR}/tests/GuestStrncpyProtected.cpp)
+    target_include_directories(guest_strncpy_protected_tests PRIVATE ${LIBS_INCLUDE_DIR})
+    target_link_libraries(guest_strncpy_protected_tests PRIVATE libc)
+    configure_windows_unwind(guest_strncpy_protected_tests)
+    add_test(NAME guest_strncpy_protected COMMAND guest_strncpy_protected_tests)
+    set_tests_properties(guest_strncpy_protected PROPERTIES TIMEOUT 20)
+    if(WIN32)
+        set_tests_properties(guest_strncpy_protected PROPERTIES ENVIRONMENT_MODIFICATION
+            "PATH=path_list_prepend:$<TARGET_FILE_DIR:libc>")
+    endif()
     add_test_executable(guest_execute_once_tests ${LIBS_INCLUDE_DIR}/tests/GuestExecuteOnce.cpp)
     target_include_directories(guest_execute_once_tests PRIVATE ${LIBS_INCLUDE_DIR})
     target_link_libraries(guest_execute_once_tests PRIVATE libc)
diff --git a/core/libs/tests/GuestStrncpyProtected.cpp b/core/libs/tests/GuestStrncpyProtected.cpp
new file mode 100644
index 0000000000..390257d386
--- /dev/null
+++ b/core/libs/tests/GuestStrncpyProtected.cpp
@@ -0,0 +1,80 @@
+#include "prx/libc/include/Api.hpp"
+#include <algorithm>
+#include <array>
+#include <cstddef>
+#include <cstdint>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <string>
+#include <vector>
+
+static void Require(bool condition) {
+    if (!condition) {
+        std::fputs("GuestStrncpyProtected check failed\n", stderr);
+        std::abort();
+    }
+}
+
+#ifdef _WIN32
+#include <windows.h>
+#else
+#include <sys/mman.h>
+#include <unistd.h>
+#endif
+
+class Buffer {
+    unsigned char* allocation;
+    std::size_t page;
+public:
+    Buffer() {
+#ifdef _WIN32
+        SYSTEM_INFO info{};
+        GetSystemInfo(&info);
+        page = info.dwPageSize;
+        allocation = static_cast<unsigned char*>(VirtualAlloc(nullptr, page * 3, MEM_RESERVE | MEM_COMMIT, PAGE_NOACCESS));
+        Require(allocation != nullptr);
+        DWORD previous;
+        Require(VirtualProtect(allocation + page, page, PAGE_READWRITE, &previous) != 0);
+#else
+        const long size = sysconf(_SC_PAGESIZE);
+        Require(size > 0);
+        page = static_cast<std::size_t>(size);
+        allocation = static_cast<unsigned char*>(mmap(nullptr, page * 3, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0));
+        Require(allocation != MAP_FAILED);
+        Require(mprotect(allocation + page, page, PROT_READ | PROT_WRITE) == 0);
+#endif
+        std::memset(allocation + page, 0xa5, page);
+    }
+    ~Buffer() {
+#ifdef _WIN32
+        Require(VirtualFree(allocation, 0, MEM_RELEASE) != 0);
+#else
+        Require(munmap(allocation, page * 3) == 0);
+#endif
+    }
+    Buffer(const Buffer&) = delete;
+    Buffer& operator=(const Buffer&) = delete;
+    unsigned char* At(std::size_t count) {
+        Require(count <= page - 32);
+        return allocation + page * 2 - (std::max)(count, std::size_t{1});
+    }
+};
+
+int main() {
+    Buffer input, output;
+    for (std::size_t count = 0; count <= 192; ++count) {
+        for (std::size_t length : {std::size_t{0}, count / 2, count, count + 1}) {
+            const std::string original(length, static_cast<char>(0x81));
+            auto* source = reinterpret_cast<char*>(input.At(length + 1));
+            auto* destination = reinterpret_cast<char*>(output.At(count));
+            std::memcpy(source, original.c_str(), length + 1);
+            std::memset(destination - 16, 0xa5, (std::max)(count, std::size_t{1}) + 16);
+            Require(strncpy_nid_postfix(destination, source, count) == destination);
+            for (std::size_t i = 0; i < count; ++i) Require(destination[i] == (i < length ? static_cast<char>(0x81) : '\0'));
+            if (count == 0) Require(static_cast<unsigned char>(*destination) == 0xa5);
+            for (int i = 1; i <= 16; ++i) Require(static_cast<unsigned char>(destination[-i]) == 0xa5);
+            Require(std::memcmp(source, original.c_str(), length + 1) == 0);
+        }
+    }
+}