From 9a6bd859243df604c1b1f1762bb701165917f367 Mon Sep 17 00:00:00 2001
From: Ariel Don <ariel@arieldon.com>
Date: Mon, 2 May 2022 15:26:10 -0500
Subject: Kernel+LibC+VFS: Implement utimensat(3)

Create POSIX utimensat() library call and corresponding system call to
update file access and modification times.
---
 Userland/Libraries/LibC/fcntl.cpp | 47 +++++++++++++++++++++++++++++++++++++++
 Userland/Libraries/LibC/fcntl.h   |  3 +++
 2 files changed, 50 insertions(+)

(limited to 'Userland/Libraries/LibC')

diff --git a/Userland/Libraries/LibC/fcntl.cpp b/Userland/Libraries/LibC/fcntl.cpp
index 9ce5039f18..4a421178d0 100644
--- a/Userland/Libraries/LibC/fcntl.cpp
+++ b/Userland/Libraries/LibC/fcntl.cpp
@@ -11,6 +11,7 @@
 #include <stdarg.h>
 #include <string.h>
 #include <syscall.h>
+#include <time.h>
 
 extern "C" {
 
@@ -102,4 +103,50 @@ int posix_fadvise(int fd, off_t offset, off_t len, int advice)
     (void)advice;
     return 0;
 }
+
+// https://pubs.opengroup.org/onlinepubs/9699919799/functions/utimensat.html
+int utimensat(int dirfd, char const* path, struct timespec const times[2], int flag)
+{
+    if (!path) {
+        errno = EFAULT;
+        return -1;
+    }
+
+    size_t path_length = strlen(path);
+    if (path_length > INT32_MAX) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    // POSIX allows AT_SYMLINK_NOFOLLOW flag or no flags.
+    if (flag & ~AT_SYMLINK_NOFOLLOW) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    // Return early without error since both changes are to be omitted.
+    if (times && times[0].tv_nsec == UTIME_OMIT && times[1].tv_nsec == UTIME_OMIT)
+        return 0;
+
+    // According to POSIX, when times is a nullptr, it's equivalent to setting
+    // both last access time and last modification time to the current time.
+    // Setting the times argument to nullptr if it matches this case prevents
+    // the need to copy it in the kernel.
+    if (times && times[0].tv_nsec == UTIME_NOW && times[1].tv_nsec == UTIME_NOW)
+        times = nullptr;
+
+    if (times) {
+        for (int i = 0; i < 2; ++i) {
+            if ((times[i].tv_nsec != UTIME_NOW && times[i].tv_nsec != UTIME_OMIT)
+                && (times[i].tv_nsec < 0 || times[i].tv_nsec >= 1'000'000'000L)) {
+                errno = EINVAL;
+                return -1;
+            }
+        }
+    }
+
+    Syscall::SC_utimensat_params params { dirfd, { path, path_length }, times, flag };
+    int rc = syscall(SC_utimensat, &params);
+    __RETURN_WITH_ERRNO(rc, rc, -1);
+}
 }
diff --git a/Userland/Libraries/LibC/fcntl.h b/Userland/Libraries/LibC/fcntl.h
index 8681676945..3704d6a7a7 100644
--- a/Userland/Libraries/LibC/fcntl.h
+++ b/Userland/Libraries/LibC/fcntl.h
@@ -8,6 +8,7 @@
 #pragma once
 
 #include <Kernel/API/POSIX/fcntl.h>
+#include <Kernel/API/POSIX/sys/stat.h>
 
 __BEGIN_DECLS
 
@@ -29,4 +30,6 @@ int inode_watcher_remove_watch(int fd, int wd);
 
 int posix_fadvise(int fd, off_t offset, off_t len, int advice);
 
+int utimensat(int dirfd, char const* path, struct timespec const times[2], int flag);
+
 __END_DECLS
-- 
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