Message-Id: <1415290033-15771-4-git-send-email-drysdale@google.com>
Date:	Thu,  6 Nov 2014 16:07:13 +0000
From:	David Drysdale <drysdale@...gle.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andy Lutomirski <luto@...capital.net>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Meredydd Luff <meredydd@...atehouse.org>,
	linux-kernel@...r.kernel.org
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kees Cook <keescook@...omium.org>,
	Arnd Bergmann <arnd@...db.de>, Rich Felker <dalias@...ifal.cx>,
	Christoph Hellwig <hch@...radead.org>, x86@...nel.org,
	linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
	David Drysdale <drysdale@...gle.com>
Subject: [PATCHv6 man-pages 3/3] execveat.2: initial man page for execveat(2)

Signed-off-by: David Drysdale <drysdale@...gle.com>
---
 man2/execveat.2 | 153 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 153 insertions(+)
 create mode 100644 man2/execveat.2

diff --git a/man2/execveat.2 b/man2/execveat.2
new file mode 100644
index 000000000000..937d79e4c4f0
--- /dev/null
+++ b/man2/execveat.2
@@ -0,0 +1,153 @@
+.\" Copyright (c) 2014 Google, Inc.
+.\"
+.\" %%%LICENSE_START(VERBATIM)
+.\" Permission is granted to make and distribute verbatim copies of this
+.\" manual provided the copyright notice and this permission notice are
+.\" preserved on all copies.
+.\"
+.\" Permission is granted to copy and distribute modified versions of this
+.\" manual under the conditions for verbatim copying, provided that the
+.\" entire resulting derived work is distributed under the terms of a
+.\" permission notice identical to this one.
+.\"
+.\" Since the Linux kernel and libraries are constantly changing, this
+.\" manual page may be incorrect or out-of-date.  The author(s) assume no
+.\" responsibility for errors or omissions, or for damages resulting from
+.\" the use of the information contained herein.  The author(s) may not
+.\" have taken the same level of care in the production of this manual,
+.\" which is licensed free of charge, as they might when working
+.\" professionally.
+.\"
+.\" Formatted or processed versions of this manual, if unaccompanied by
+.\" the source, must acknowledge the copyright and authors of this work.
+.\" %%%LICENSE_END
+.\"
+.TH EXECVEAT 2 2014-04-02 "Linux" "Linux Programmer's Manual"
+.SH NAME
+execveat \- execute program relative to a directory file descriptor
+.SH SYNOPSIS
+.B #include <unistd.h>
+.sp
+.BI "int execveat(int " fd ", const char *" pathname ","
+.br
+.BI "             char *const " argv "[],  char *const " envp "[],"
+.br
+.BI "             int " flags);
+.SH DESCRIPTION
+The
+.BR execveat ()
+system call executes the program pointed to by the combination of \fIfd\fP and \fIpathname\fP.
+The
+.BR execveat ()
+system call operates in exactly the same way as
+.BR execve (2),
+except for the differences described in this manual page.
+
+If the pathname given in
+.I pathname
+is relative, then it is interpreted relative to the directory
+referred to by the file descriptor
+.I fd
+(rather than relative to the current working directory of
+the calling process, as is done by
+.BR execve (2)
+for a relative pathname).
+
+If
+.I pathname
+is relative and
+.I fd
+is the special value
+.BR AT_FDCWD ,
+then
+.I pathname
+is interpreted relative to the current working
+directory of the calling process (like
+.BR execve (2)).
+
+If
+.I pathname
+is absolute, then
+.I fd
+is ignored.
+
+If
+.I pathname
+is an empty string and the
+.BR AT_EMPTY_PATH
+flag is specified, then the file descriptor
+.I fd
+specifies the file to be executed.
+
+.I flags
+can either be 0, or include the following flags:
+.TP
+.BR AT_EMPTY_PATH
+If
+.I pathname
+is an empty string, operate on the file referred to by
+.IR fd
+(which may have been obtained using the
+.BR open (2)
+.B O_PATH
+flag).
+.TP
+.B AT_SYMLINK_NOFOLLOW
+If the file identified by
+.I fd
+and a non-NULL
+.I pathname
+is a symbolic link, then the call fails with the error
+.BR EINVAL .
+.SH "RETURN VALUE"
+On success,
+.BR execveat ()
+does not return. On error \-1 is returned, and
+.I errno
+is set appropriately.
+.SH ERRORS
+The same errors that occur for
+.BR execve (2)
+can also occur for
+.BR execveat ().
+The following additional errors can occur for
+.BR execveat ():
+.TP
+.B EBADF
+.I fd
+is not a valid file descriptor.
+.TP
+.B ENOENT
+The program identified by \fIfd\fP and \fIpathname\fP requires the
+use of an interpreter program (such as a script starting with
+"#!") but the file descriptor
+.I fd
+was opened with the
+.B O_CLOEXEC
+flag and so the program file is inaccessible to the launched interpreter.
+.TP
+.B EINVAL
+Invalid flag specified in
+.IR flags .
+.TP
+.B ENOTDIR
+.I pathname
+is relative and
+.I fd
+is a file descriptor referring to a file other than a directory.
+.SH VERSIONS
+.BR execveat ()
+was added to Linux in kernel 3.???.
+.SH NOTES
+In addition to the reasons explained in
+.BR openat (2),
+the
+.BR execveat ()
+system call is also needed to allow
+.BR fexecve (3)
+to be implemented on systems that do not have the
+.I /proc
+filesystem mounted.
+.SH SEE ALSO
+.BR execve (2),
+.BR fexecve (3)
--
2.1.0.rc2.206.gedb03e5
--
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