kernel: report /dev/random and /dev/urandom as character devices (#1140)

kernel: report entropy sources as character devices

Co-authored-by: nmzik <Nmzik@mail.ru>

src/kernel/fileSystem.cpp

@@ -1138,19 +1138,11 @@ int KYTY_SYSV_ABI KernelFstat(int d, FileStat* sb) {
 	auto wt = at;
 
 	if (file->special != SpecialFile::None) {
+		stat.st_mode    = 0020644u;
 		stat.st_size    = 0;
 		stat.st_blksize = 512;
 		stat.st_blocks  = 0;
-		SecToTimespec(&stat.st_atim, at.ToUnix());
-		SecToTimespec(&stat.st_mtim, wt.ToUnix());
-		stat.st_ctim     = stat.st_atim;
-		stat.st_birthtim = stat.st_mtim;
-		*sb              = stat;
-
-		return OK;
-	}
-
-	if (!file->directory) {
+	} else if (!file->directory) {
 		file->mutex.Lock();
 
 		bool is_invalid = file->f.IsInvalid();

tests/KernelFileSystemTests.cpp

@@ -121,6 +121,20 @@ void CheckSaveRename(const std::filesystem::path &root,
         "renamed save contents");
 }
 
+void TestRandomDevices() {
+  for (const auto* path : {"/dev/urandom", "/dev/random"}) {
+    const int fd = FileSystem::KernelOpen(path, 0, 0);
+    FileSystem::FileStat stat {};
+    Check(fd >= 3 && FileSystem::KernelFstat(fd, &stat) == OK &&
+              (stat.st_mode & 0170000) == 0020000,
+          "entropy sources are character devices");
+    std::array<uint8_t, 32> entropy {};
+    Check(FileSystem::KernelRead(fd, entropy.data(), entropy.size()) == entropy.size(),
+          "character device supplies requested entropy");
+    Check(FileSystem::KernelClose(fd) == OK, "close entropy source");
+  }
+}
+
 void TestSaveOpenVisibility() {
   constexpr char Path[] = "/savedata0/visible-save.dat";
   constexpr char Payload[] = "saved progress";
@@ -1398,6 +1412,7 @@ int main(int, char**) {
 
   TempDirectory temporary;
   FileSystem::Initialize();
+  TestRandomDevices();
   CheckMountRoot(temporary.Path());
   CheckUnmappedPaths(temporary.Path());
   CheckArchiveMount(temporary.Path());