Utilities: Add blockdev utility

This new utility queries a block device for its size via the newly
introduced ioctl STORAGE_DEVICE_GET_SIZE request.

Userland/Utilities/blockdev.cpp

@@ -0,0 +1,61 @@
+/*
+ * Copyright (c) 2021, David Isaksson <davidisaksson93@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibCore/ArgsParser.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <sys/ioctl.h>
+#include <unistd.h>
+
+static void fetch_ioctl(int fd, int request)
+{
+    size_t value;
+    if (ioctl(fd, request, &value) < 0) {
+        perror("ioctl");
+        exit(1);
+    }
+    outln("{}", value);
+}
+
+int main(int argc, char** argv)
+{
+    if (unveil("/dev", "r") < 0) {
+        perror("unveil");
+        return 1;
+    }
+
+    if (unveil(nullptr, nullptr) < 0) {
+        perror("unveil");
+        return 1;
+    }
+
+    if (pledge("stdio rpath", nullptr) < 0) {
+        perror("pledge");
+        return 1;
+    }
+
+    const char* device = nullptr;
+
+    bool flag_get_disk_size = false;
+
+    Core::ArgsParser args_parser;
+    args_parser.set_general_help("Call block device ioctls");
+    args_parser.add_option(flag_get_disk_size, "Get size in bytes", "size", 's');
+    args_parser.add_positional_argument(device, "Device to query", "device");
+    args_parser.parse(argc, argv);
+
+    int fd = open(device, O_RDONLY);
+    if (fd < 0) {
+        perror("open");
+        return 1;
+    }
+
+    if (flag_get_disk_size) {
+        fetch_ioctl(fd, STORAGE_DEVICE_GET_SIZE);
+    }
+
+    return 0;
+}