Add AT_EMPTY_PATH for several *at(2) syscalls

(cherry picked from commit 509124b62616f73dcdc42263ee109392dafafd99)

7 files changed, 82 insertions, 7 deletions

diff --git a/lib/libc/sys/access.2 b/lib/libc/sys/access.2
index 13bfd7e5a88a..12af63385780 100644
--- a/lib/libc/sys/access.2
+++ b/lib/libc/sys/access.2
@@ -28,7 +28,7 @@
 .\"     @(#)access.2	8.2 (Berkeley) 4/1/94
 .\" $FreeBSD$
 .\"
-.Dd February 23, 2021
+.Dd March 30, 2021
 .Dt ACCESS 2
 .Os
 .Sh NAME
@@ -129,6 +129,17 @@ See the description of the
 flag in the
 .Xr open 2
 manual page.
+.It Dv AT_EMPTY_PATH
+If the
+.Fa path
+argument is an empty string, operate on the file or directory
+referenced by the descriptor
+.Fa fd .
+If
+.Fa fd
+is equal to
+.Dv AT_FDCWD ,
+operate on the current working directory.
 .El
 .Pp
 Even if a process's real or effective user has appropriate privileges
diff --git a/lib/libc/sys/chflags.2 b/lib/libc/sys/chflags.2
index a44713904599..f8dfd59c39d3 100644
--- a/lib/libc/sys/chflags.2
+++ b/lib/libc/sys/chflags.2
@@ -28,7 +28,7 @@
 .\"	@(#)chflags.2	8.3 (Berkeley) 5/2/95
 .\" $FreeBSD$
 .\"
-.Dd February 23, 2021
+.Dd March 30, 2021
 .Dt CHFLAGS 2
 .Os
 .Sh NAME
@@ -103,6 +103,17 @@ See the description of the
 flag in the
 .Xr open 2
 manual page.
+.It Dv AT_EMPTY_PATH
+If the
+.Fa path
+argument is an empty string, operate on the file or directory
+referenced by the descriptor
+.Fa fd .
+If
+.Fa fd
+is equal to
+.Dv AT_FDCWD ,
+operate on the current working directory.
 .El
 .Pp
 If
diff --git a/lib/libc/sys/chmod.2 b/lib/libc/sys/chmod.2
index 0127a5b629e4..44a1b18718f1 100644
--- a/lib/libc/sys/chmod.2
+++ b/lib/libc/sys/chmod.2
@@ -28,7 +28,7 @@
 .\"     @(#)chmod.2	8.1 (Berkeley) 6/4/93
 .\" $FreeBSD$
 .\"
-.Dd February 23, 2021
+.Dd March 30, 2021
 .Dt CHMOD 2
 .Os
 .Sh NAME
@@ -110,6 +110,17 @@ See the description of the
 flag in the
 .Xr open 2
 manual page.
+.It Dv AT_EMPTY_PATH
+If the
+.Fa path
+argument is an empty string, operate on the file or directory
+referenced by the descriptor
+.Fa fd .
+If
+.Fa fd
+is equal to
+.Dv AT_FDCWD ,
+operate on the current working directory.
 .El
 .Pp
 If
diff --git a/lib/libc/sys/chown.2 b/lib/libc/sys/chown.2
index 4c45ce9174bb..467ff8a87e55 100644
--- a/lib/libc/sys/chown.2
+++ b/lib/libc/sys/chown.2
@@ -28,7 +28,7 @@
 .\"     @(#)chown.2	8.4 (Berkeley) 4/19/94
 .\" $FreeBSD$
 .\"
-.Dd February 23, 2021
+.Dd March 30, 2021
 .Dt CHOWN 2
 .Os
 .Sh NAME
@@ -127,6 +127,17 @@ See the description of the
 flag in the
 .Xr open 2
 manual page.
+.It Dv AT_EMPTY_PATH
+If the
+.Fa path
+argument is an empty string, operate on the file or directory
+referenced by the descriptor
+.Fa fd .
+If
+.Fa fd
+is equal to
+.Dv AT_FDCWD ,
+operate on the current working directory.
 .El
 .Pp
 If
diff --git a/lib/libc/sys/link.2 b/lib/libc/sys/link.2
index bcf03f17f3bb..37225f9571d0 100644
--- a/lib/libc/sys/link.2
+++ b/lib/libc/sys/link.2
@@ -28,7 +28,7 @@
 .\"     @(#)link.2	8.3 (Berkeley) 1/12/94
 .\" $FreeBSD$
 .\"
-.Dd February 23, 2021
+.Dd March 30, 2021
 .Dt LINK 2
 .Os
 .Sh NAME
@@ -124,6 +124,15 @@ See the description of the
 flag in the
 .Xr open 2
 manual page.
+.It Dv AT_EMPTY_PATH
+If the
+.Fa path2
+argument is an empty string, link the file referenced by the descriptor
+.Fa fd2 .
+The operation requires that the calling process has the
+.Dv PRIV_VFS_FHOPEN
+privilege, effectively being executed with effective user
+.Dv root .
 .El
 .Pp
 If
diff --git a/lib/libc/sys/stat.2 b/lib/libc/sys/stat.2
index 0ed70620af63..55221d05a60e 100644
--- a/lib/libc/sys/stat.2
+++ b/lib/libc/sys/stat.2
@@ -28,7 +28,7 @@
 .\"     @(#)stat.2	8.4 (Berkeley) 5/1/95
 .\" $FreeBSD$
 .\"
-.Dd February 23, 2021
+.Dd March 30, 2021
 .Dt STAT 2
 .Os
 .Sh NAME
@@ -111,6 +111,17 @@ See the description of the
 flag in the
 .Xr open 2
 manual page.
+.It Dv AT_EMPTY_PATH
+If the
+.Fa path
+argument is an empty string, operate on the file or directory
+referenced by the descriptor
+.Fa fd .
+If
+.Fa fd
+is equal to
+.Dv AT_FDCWD ,
+operate on the current working directory.
 .El
 .Pp
 If
diff --git a/lib/libc/sys/utimensat.2 b/lib/libc/sys/utimensat.2
index d31ee1f1515a..2af452898c9d 100644
--- a/lib/libc/sys/utimensat.2
+++ b/lib/libc/sys/utimensat.2
@@ -31,7 +31,7 @@
 .\"     @(#)utimes.2	8.1 (Berkeley) 6/4/93
 .\" $FreeBSD$
 .\"
-.Dd February 23, 2021
+.Dd March 30, 2021
 .Dt UTIMENSAT 2
 .Os
 .Sh NAME
@@ -155,6 +155,17 @@ See the description of the
 flag in the
 .Xr open 2
 manual page.
+.It Dv AT_EMPTY_PATH
+If the
+.Fa path
+argument is an empty string, operate on the file or directory
+referenced by the descriptor
+.Fa fd .
+If
+.Fa fd
+is equal to
+.Dv AT_FDCWD ,
+operate on the current working directory.
 .El
 .Sh RETURN VALUES
 .Rv -std