Kernel+LibC+VFS: Implement utimensat(3)

Create POSIX utimensat() library call and corresponding system call to
update file access and modification times.

1 files changed, 61 insertions, 0 deletions

diff --git a/Kernel/Syscalls/utimensat.cpp b/Kernel/Syscalls/utimensat.cpp
new file mode 100644
index 0000000000..4a6ca189a3
--- /dev/null
+++ b/Kernel/Syscalls/utimensat.cpp
@@ -0,0 +1,61 @@
+/*
+ * Copyright (c) 2022, Ariel Don <ariel@arieldon.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/Assertions.h>
+#include <AK/StringView.h>
+#include <Kernel/FileSystem/VirtualFileSystem.h>
+#include <Kernel/KLexicalPath.h>
+#include <Kernel/Process.h>
+
+namespace Kernel {
+
+ErrorOr<FlatPtr> Process::sys$utimensat(Userspace<Syscall::SC_utimensat_params const*> user_params)
+{
+    VERIFY_PROCESS_BIG_LOCK_ACQUIRED(this);
+    TRY(require_promise(Pledge::fattr));
+
+    auto params = TRY(copy_typed_from_user(user_params));
+    auto now = kgettimeofday().to_truncated_seconds();
+
+    timespec times[2];
+    if (params.times) {
+        TRY(copy_from_user(times, params.times, sizeof(times)));
+        if (times[0].tv_nsec == UTIME_NOW)
+            times[0].tv_sec = now;
+        if (times[1].tv_nsec == UTIME_NOW)
+            times[1].tv_sec = now;
+    } else {
+        // According to POSIX, both access and modification times are set to
+        // the current time given a nullptr.
+        times[0].tv_sec = now;
+        times[0].tv_nsec = UTIME_NOW;
+        times[1].tv_sec = now;
+        times[1].tv_nsec = UTIME_NOW;
+    }
+
+    int dirfd = params.dirfd;
+    auto path = TRY(get_syscall_path_argument(params.path));
+
+    RefPtr<Custody> base;
+    if (dirfd == AT_FDCWD) {
+        base = current_directory();
+    } else {
+        auto base_description = TRY(open_file_description(dirfd));
+        if (!KLexicalPath::is_absolute(path->view()) && !base_description->is_directory())
+            return ENOTDIR;
+        if (!base_description->custody())
+            return EINVAL;
+        base = base_description->custody();
+    }
+
+    auto& atime = times[0];
+    auto& mtime = times[1];
+    int follow_symlink = params.flag & AT_SYMLINK_NOFOLLOW ? O_NOFOLLOW_NOERROR : 0;
+    TRY(VirtualFileSystem::the().utimensat(path->view(), *base, atime, mtime, follow_symlink));
+    return 0;
+}
+
+}