Kernel: Add statvfs & fstatvfs Syscalls

These syscalls fill a statvfs struct with various data
about the mount on the VFS.

Kernel/Syscalls/statvfs.cpp

@@ -0,0 +1,97 @@
+/*
+ * Copyright (c) 2021, Justin Mietzner <sw1tchbl4d3@sw1tchbl4d3.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <Kernel/FileSystem/Custody.h>
+#include <Kernel/FileSystem/FileDescription.h>
+#include <Kernel/FileSystem/VirtualFileSystem.h>
+#include <Kernel/Process.h>
+
+namespace Kernel {
+
+KResultOr<int> Process::do_statvfs(String path, statvfs* buf)
+{
+    auto custody_or_error = VFS::the().resolve_path(path, current_directory(), nullptr, 0);
+    if (custody_or_error.is_error())
+        return custody_or_error.error();
+
+    auto& custody = custody_or_error.value();
+    auto& inode = custody->inode();
+    auto& fs = inode.fs();
+
+    statvfs kernelbuf = {};
+
+    kernelbuf.f_bsize = static_cast<u64>(fs.block_size());
+    kernelbuf.f_frsize = fs.fragment_size();
+    kernelbuf.f_blocks = fs.total_block_count();
+    kernelbuf.f_bfree = fs.free_block_count();
+
+    // FIXME: Implement "available blocks" into Filesystem
+    kernelbuf.f_bavail = fs.free_block_count();
+
+    kernelbuf.f_files = fs.total_inode_count();
+    kernelbuf.f_ffree = fs.free_inode_count();
+    kernelbuf.f_favail = fs.free_inode_count(); // FIXME: same as f_bavail
+
+    kernelbuf.f_fsid = 0; // FIXME: Implement "Filesystem ID" into Filesystem
+
+    kernelbuf.f_namemax = 255;
+
+    Custody* current_custody = custody;
+
+    while (current_custody) {
+        VFS::the().for_each_mount([&kernelbuf, &current_custody](auto& mount) {
+            if (current_custody) {
+                if (&current_custody->inode() == &mount.guest()) {
+                    int mountflags = mount.flags();
+                    int flags = 0;
+                    if (mountflags & MS_RDONLY)
+                        flags = flags | ST_RDONLY;
+                    if (mountflags & MS_NOSUID)
+                        flags = flags | ST_NOSUID;
+
+                    kernelbuf.f_flag = flags;
+                    current_custody = nullptr;
+                }
+            }
+        });
+
+        if (current_custody) {
+            current_custody = current_custody->parent();
+        }
+    }
+
+    if (!copy_to_user(buf, &kernelbuf))
+        return EFAULT;
+
+    return 0;
+}
+
+KResultOr<int> Process::sys$statvfs(Userspace<const Syscall::SC_statvfs_params*> user_params)
+{
+    REQUIRE_PROMISE(rpath);
+
+    Syscall::SC_statvfs_params params;
+    if (!copy_from_user(&params, user_params))
+        return EFAULT;
+    auto path = get_syscall_path_argument(params.path);
+    if (path.is_error())
+        return path.error();
+
+    return do_statvfs(path.value(), params.buf);
+}
+
+KResultOr<int> Process::sys$fstatvfs(int fd, statvfs* buf)
+{
+    REQUIRE_PROMISE(stdio);
+
+    auto description = file_description(fd);
+    if (!description)
+        return EBADF;
+
+    return do_statvfs(description->absolute_path(), buf);
+}
+
+}