Provide wrappers for the new I386_{GET,SET}_{FS,GS}BASE sysarch() calls.

In some sense, these are mainly to give names to hang manpages from.

1 files changed, 99 insertions, 0 deletions

diff --git a/lib/libarch/i386/i386_get_gsbase.2 b/lib/libarch/i386/i386_get_gsbase.2
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+.\"	$OpenBSD: i386_get_gsbase.2,v 1.1 2011/03/12 04:12:29 guenther Exp $
+.\"	$NetBSD: i386_get_ioperm.2,v 1.3 1996/02/27 22:57:17 jtc Exp $
+.\"
+.\" Copyright (c) 1996 The NetBSD Foundation, Inc.
+.\" All rights reserved.
+.\"
+.\" This code is derived from software contributed to The NetBSD Foundation
+.\" by John T. Kohl and Charles M. Hannum.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+.\" PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE
+.\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+.\" POSSIBILITY OF SUCH DAMAGE.
+.\"
+.Dd $Mdocdate: March 12 2011 $
+.Dt I386_GET_GSBASE 2 i386
+.Os
+.Sh NAME
+.Nm i386_get_gsbase ,
+.Nm i386_set_gsbase
+.Nd manage i386 per-thread %gs base address
+.Sh SYNOPSIS
+.Fd #include <sys/types.h>
+.Fd #include <machine/sysarch.h>
+.Ft int
+.Fn i386_get_gsbase "void **base"
+.Ft int
+.Fn i386_set_gsbase "void *base"
+.Sh DESCRIPTION
+.Fn i386_get_gsbase
+copies the current base address of the segment that, by default,
+is referenced by the %gs selector into the memory referenced by
+.Fa base .
+.Pp
+.Fn i386_set_gsbase
+sets the base address of the segment that, by default, is referenced
+by %gs to the address
+.Fa base .
+.Pp
+When rfork(RFPROC | RFTHREAD) is used, the segment base address
+for the above calls is a per-thread value.
+When a new thread is created,
+it inherits the base from the thread that created it.
+.Pp
+.Sy Note:
+Code using the
+.Fn i386_get_gsbase
+and
+.Fn i386_set_gsbase
+functions must be compiled using
+.Cm -li386 .
+.Sh RETURN VALUES
+Upon successful completion,
+.Fn i386_get_gsbase
+and
+.Fn i386_set_gsbase
+return 0.
+Otherwise, a value of \-1 is returned and the global variable
+.Va errno
+is set to indicate the error.
+.Sh ERRORS
+.Fn i386_get_gsbase
+will fail if:
+.Bl -tag -width [EINVAL]
+.It Bq Er EFAULT
+.Fa base
+points outside the process's allocated address space.
+.El
+.Sh SEE ALSO
+.Rs
+.%A Intel
+.%T i386 Microprocessor Programmer's Reference Manual
+.Re
+.Sh WARNING
+The ELF Thread-Local Storage ABI reserves %gs for its own use and
+requires that the dynamic linker and thread library set it to
+reference data-structures internal to and shared between them.
+Programs should use the __thread storage class keyword instead of
+using these calls.
+To be maximally portable,
+programs that require per-thread data should use the
+.Fn pthread_key_create
+interface.