From eb5389e933bec98735e71c3bab3706841647af48 Mon Sep 17 00:00:00 2001
From: sin-ack <sin-ack@users.noreply.github.com>
Date: Sat, 1 Oct 2022 11:36:24 +0000
Subject: [PATCH] Kernel+LibC+LibCore: Implement `mkdirat(2)`

---
 Kernel/Process.h                      | 2 +-
 Kernel/Syscalls/mkdir.cpp             | 4 ++--
 Userland/Libraries/LibC/stat.cpp      | 8 +++++++-
 Userland/Libraries/LibC/sys/stat.h    | 1 +
 Userland/Libraries/LibCore/System.cpp | 2 +-
 5 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/Kernel/Process.h b/Kernel/Process.h
index 3147965db38..cc1410d9e05 100644
--- a/Kernel/Process.h
+++ b/Kernel/Process.h
@@ -374,7 +374,7 @@ public:
     ErrorOr<FlatPtr> sys$access(Userspace<char const*> pathname, size_t path_length, int mode);
     ErrorOr<FlatPtr> sys$fcntl(int fd, int cmd, uintptr_t extra_arg);
     ErrorOr<FlatPtr> sys$ioctl(int fd, unsigned request, FlatPtr arg);
-    ErrorOr<FlatPtr> sys$mkdir(Userspace<char const*> pathname, size_t path_length, mode_t mode);
+    ErrorOr<FlatPtr> sys$mkdir(int dirfd, Userspace<char const*> pathname, size_t path_length, mode_t mode);
     ErrorOr<FlatPtr> sys$times(Userspace<tms*>);
     ErrorOr<FlatPtr> sys$utime(Userspace<char const*> pathname, size_t path_length, Userspace<const struct utimbuf*>);
     ErrorOr<FlatPtr> sys$utimensat(Userspace<Syscall::SC_utimensat_params const*>);
diff --git a/Kernel/Syscalls/mkdir.cpp b/Kernel/Syscalls/mkdir.cpp
index 7cd0de8cbdc..e614316c8b8 100644
--- a/Kernel/Syscalls/mkdir.cpp
+++ b/Kernel/Syscalls/mkdir.cpp
@@ -10,12 +10,12 @@
 
 namespace Kernel {
 
-ErrorOr<FlatPtr> Process::sys$mkdir(Userspace<char const*> user_path, size_t path_length, mode_t mode)
+ErrorOr<FlatPtr> Process::sys$mkdir(int dirfd, Userspace<char const*> user_path, size_t path_length, mode_t mode)
 {
     VERIFY_NO_PROCESS_BIG_LOCK(this);
     TRY(require_promise(Pledge::cpath));
     auto path = TRY(get_syscall_path_argument(user_path, path_length));
-    TRY(VirtualFileSystem::the().mkdir(credentials(), path->view(), mode & ~umask(), current_directory()));
+    TRY(VirtualFileSystem::the().mkdir(credentials(), path->view(), mode & ~umask(), TRY(custody_for_dirfd(dirfd))));
     return 0;
 }
 }
diff --git a/Userland/Libraries/LibC/stat.cpp b/Userland/Libraries/LibC/stat.cpp
index d1ce13ea902..10c95b1d260 100644
--- a/Userland/Libraries/LibC/stat.cpp
+++ b/Userland/Libraries/LibC/stat.cpp
@@ -23,12 +23,18 @@ mode_t umask(mode_t mask)
 
 // https://pubs.opengroup.org/onlinepubs/9699919799/functions/mkdir.html
 int mkdir(char const* pathname, mode_t mode)
+{
+    return mkdirat(AT_FDCWD, pathname, mode);
+}
+
+// https://pubs.opengroup.org/onlinepubs/9699919799/functions/mkdirat.html
+int mkdirat(int dirfd, char const* pathname, mode_t mode)
 {
     if (!pathname) {
         errno = EFAULT;
         return -1;
     }
-    int rc = syscall(SC_mkdir, pathname, strlen(pathname), mode);
+    int rc = syscall(SC_mkdir, dirfd, pathname, strlen(pathname), mode);
     __RETURN_WITH_ERRNO(rc, rc, -1);
 }
 
diff --git a/Userland/Libraries/LibC/sys/stat.h b/Userland/Libraries/LibC/sys/stat.h
index 16b8a2c2e81..e9a4e9b0300 100644
--- a/Userland/Libraries/LibC/sys/stat.h
+++ b/Userland/Libraries/LibC/sys/stat.h
@@ -18,6 +18,7 @@ int chmod(char const* pathname, mode_t);
 int fchmodat(int fd, char const* path, mode_t mode, int flag);
 int fchmod(int fd, mode_t);
 int mkdir(char const* pathname, mode_t);
+int mkdirat(int dirfd, char const* pathname, mode_t);
 int mkfifo(char const* pathname, mode_t);
 int fstat(int fd, struct stat* statbuf);
 int lstat(char const* path, struct stat* statbuf);
diff --git a/Userland/Libraries/LibCore/System.cpp b/Userland/Libraries/LibCore/System.cpp
index e4576c4f633..11c8ea9b02f 100644
--- a/Userland/Libraries/LibCore/System.cpp
+++ b/Userland/Libraries/LibCore/System.cpp
@@ -857,7 +857,7 @@ ErrorOr<void> mkdir(StringView path, mode_t mode)
     if (path.is_null())
         return Error::from_errno(EFAULT);
 #ifdef AK_OS_SERENITY
-    int rc = syscall(SC_mkdir, path.characters_without_null_termination(), path.length(), mode);
+    int rc = syscall(SC_mkdir, AT_FDCWD, path.characters_without_null_termination(), path.length(), mode);
     HANDLE_SYSCALL_RETURN_VALUE("mkdir", rc, {});
 #else
     DeprecatedString path_string = path;