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authorKonstantin Belousov <kib@FreeBSD.org>2021-03-18 10:41:47 +0000
committerKonstantin Belousov <kib@FreeBSD.org>2021-04-15 09:48:24 +0000
commit8d9ed174f3afba5f114742447e622fc1173d4774 (patch)
tree12c1f979472855bf6ed586e82d66cefc43e00817 /lib/libc/sys/open.2
parent509124b62616f73dcdc42263ee109392dafafd99 (diff)
downloadsrc-8d9ed174f3afba5f114742447e622fc1173d4774.tar.gz
src-8d9ed174f3afba5f114742447e622fc1173d4774.zip
open(2): Implement O_PATH
Reviewed by: markj Tested by: pho Discussed with: walker.aj325_gmail.com, wulf Sponsored by: The FreeBSD Foundation MFC after: 1 week Differential revision: https://reviews.freebsd.org/D29323
Diffstat (limited to 'lib/libc/sys/open.2')
-rw-r--r--lib/libc/sys/open.241
1 files changed, 40 insertions, 1 deletions
diff --git a/lib/libc/sys/open.2 b/lib/libc/sys/open.2
index e24c823d039a..f9c54bfc7581 100644
--- a/lib/libc/sys/open.2
+++ b/lib/libc/sys/open.2
@@ -28,7 +28,7 @@
.\" @(#)open.2 8.2 (Berkeley) 11/16/93
.\" $FreeBSD$
.\"
-.Dd February 23, 2021
+.Dd March 18, 2021
.Dt OPEN 2
.Os
.Sh NAME
@@ -168,6 +168,7 @@ O_DIRECTORY error if file is not a directory
O_CLOEXEC set FD_CLOEXEC upon open
O_VERIFY verify the contents of the file
O_RESOLVE_BENEATH path resolution must not cross the fd directory
+O_PATH record only the target path in the opened descriptor
.Ed
.Pp
Opening a file with
@@ -316,6 +317,44 @@ The primary use for this descriptor will be as the lookup descriptor for the
.Fn *at
family of functions.
.Pp
+.Dv O_PATH
+returns a file descriptor that can be used as a directory file descriptor for
+.Xr openat 2
+and other system calls taking a file descriptor argument, like
+.Xr fstatat 2
+and others.
+The other functionality of the returned file descriptor is limited to
+the descriptor-level operations.
+It can be used for
+.Bl -tag -width SCM_RIGHTS -offset indent -compact
+.It Xr fcntl 2
+but advisory locking is not allowed
+.It Xr dup 2
+.It Xr close 2
+.It Xr fstat 2
+.It Xr fexecve 2
+requires that
+.Dv O_EXEC
+was also specified at open time
+.It Dv SCM_RIGHTS
+can be passed over a
+.Xr unix 4
+socket using a
+.Dv SCM_RIGHTS
+message
+.El
+But operations like
+.Xr read 2 ,
+.Xr ftruncate 2 ,
+and any other that operate on file and not on file descriptor (except
+.Xr fstat 2 ),
+are not allowed.
+See also the description of
+.Dv AT_EMPTY_PATH
+flag for
+.Xr fstatat 2
+and related syscalls.
+.Pp
If successful,
.Fn open
returns a non-negative integer, termed a file descriptor.