fix(libkernel): follow a Windows symbolic link in chmod

core/libs/prx/libkernel/File/src/Stdio.cpp

@@ -91,16 +91,7 @@ static int NativeMkdir(const std::filesystem::path& path, std::uint16_t mode) {
     (void)mode;
     return ::_wmkdir(path.wstring().c_str());
 }
-static int NativeChmod(const std::filesystem::path& path, int mode) {
-    RecordWrittenPath_nid_no_patch(path);
-    return ::_wchmod(path.wstring().c_str(), mode);
-}
-std::optional<std::filesystem::path> File::WindowsDescriptorPath_nid_no_patch(int descriptor) {
-    const auto handle = reinterpret_cast<HANDLE>(::_get_osfhandle(descriptor));
-    if (handle == INVALID_HANDLE_VALUE) {
-        errno = EBADF;
-        return std::nullopt;
-    }
+static std::optional<std::filesystem::path> HandlePath(HANDLE handle) {
     std::wstring path(MAX_PATH, L'\0');
     auto length = ::GetFinalPathNameByHandleW(handle, path.data(), static_cast<DWORD>(path.size()), FILE_NAME_NORMALIZED);
     if (length >= path.size()) {
@@ -120,6 +111,32 @@ std::optional<std::filesystem::path> File::WindowsDescriptorPath_nid_no_patch(in
     else if (path.starts_with(LR"(\\?\)") && path.size() > 6 && path[5] == L':' && path[6] == L'\\') path.erase(0, 4);
     return path;
 }
+std::optional<std::filesystem::path> File::WindowsDescriptorPath_nid_no_patch(int descriptor) {
+    const auto handle = reinterpret_cast<HANDLE>(::_get_osfhandle(descriptor));
+    if (handle == INVALID_HANDLE_VALUE) {
+        errno = EBADF;
+        return std::nullopt;
+    }
+    return HandlePath(handle);
+}
+static int NativeChmod(const std::filesystem::path& path, int mode) {
+    const DWORD attributes = GetFileAttributesW(path.c_str());
+    if (attributes == INVALID_FILE_ATTRIBUTES || (attributes & FILE_ATTRIBUTE_REPARSE_POINT) == 0) {
+        RecordWrittenPath_nid_no_patch(path);
+        return ::_wchmod(path.wstring().c_str(), mode);
+    }
+    const HANDLE handle = CreateFileW(path.c_str(), 0, FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, nullptr,
+        OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, nullptr);
+    if (handle == INVALID_HANDLE_VALUE) {
+        errno = WindowsOpenError_nid_no_patch(GetLastError());
+        return -1;
+    }
+    const auto target = HandlePath(handle);
+    CloseHandle(handle);
+    if (!target) return -1;
+    RecordWrittenPath_nid_no_patch(*target);
+    return ::_wchmod(target->wstring().c_str(), mode);
+}
 static int NativeFchmod(int descriptor, int mode) {
     const auto path = File::WindowsDescriptorPath_nid_no_patch(descriptor);
     return path ? NativeChmod(*path, mode) : -1;

core/libs/tests/GuestFilesystem.cpp

@@ -914,6 +914,37 @@ int main() {
     };
     Require(sceKernelFchmod(descriptor, 0400) == 0 && !ownerWrite());
     Require(fchmod_nid_postfix(descriptor, 0600) == 0 && ownerWrite());
+    const auto sizedLink = sized.parent_path() / "sized.link";
+    const auto missingLink = sized.parent_path() / "missing.link";
+    const auto loopLink = sized.parent_path() / "loop.link";
+#ifdef _WIN32
+    const DWORD linkFlags = SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE;
+    const bool chmodLinked = CreateSymbolicLinkW(sizedLink.wstring().c_str(), sized.filename().wstring().c_str(), linkFlags) &&
+        CreateSymbolicLinkW(missingLink.wstring().c_str(), L"missing.bin", linkFlags) &&
+        CreateSymbolicLinkW(loopLink.wstring().c_str(), L"loop.link", linkFlags);
+#else
+    std::error_code chmodLinkError;
+    std::filesystem::create_symlink(sized.filename(), sizedLink, chmodLinkError);
+    if (!chmodLinkError) std::filesystem::create_symlink("missing.bin", missingLink, chmodLinkError);
+    if (!chmodLinkError) std::filesystem::create_symlink("loop.link", loopLink, chmodLinkError);
+    const bool chmodLinked = !chmodLinkError;
+#endif
+    if (chmodLinked) {
+        Require(chmod_nid_postfix(sizedLink.string().c_str(), 0400) == 0 && !ownerWrite());
+#ifdef _WIN32
+        Require((GetFileAttributesW(sizedLink.wstring().c_str()) & FILE_ATTRIBUTE_READONLY) == 0);
+#endif
+        Require(chmod_nid_postfix(sizedLink.string().c_str(), 0600) == 0 && ownerWrite());
+        Require(chmod_nid_postfix(missingLink.string().c_str(), 0600) == -1 && *__error_nid_postfix() == 2);
+#ifdef _WIN32
+        Require(chmod_nid_postfix(loopLink.string().c_str(), 0600) == -1 && *__error_nid_postfix() == 62);
+#endif
+    } else {
+        std::fprintf(stderr, "symbolic links unavailable: the chmod link cases not tested\n");
+    }
+    unlink_nid_postfix(sizedLink.string().c_str());
+    unlink_nid_postfix(missingLink.string().c_str());
+    unlink_nid_postfix(loopLink.string().c_str());
     Require(sceKernelFtruncate(descriptor, 3) == 0);
     FileStat times{};
     const KernelTimeval past[2]{{1000000000, 0}, {1000000000, 500000}};