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.\" $OpenBSD: pinsyscalls.2,v 1.1 2023/12/11 00:34:24 deraadt Exp $
.\"
.\" Copyright (c) 2023 Theo de Raadt <deraadt@openbsd.org>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd $Mdocdate: December 11 2023 $
.Dt PINSYSCALLS 2
.Os
.Sh NAME
.Nm pinsyscalls
.Nd pin system call entry to precise locations in the address space
.Sh SYNOPSIS
.In sys/types.h
.Ft int
.Fn pinsyscalls "void *start" "size_t len" "uint *pintable" "size_t pintablesize"
.Sh DESCRIPTION
The
.Fn pinsyscalls
system call specifies the
.Va start
to
.Va start + len
range in the address space where the system call entry instructions are found,
and furthermore provides a table of uint offsets from that
.Va start
(indexed by the system call number) to
provide the precise location for the system call instruction required
for that system call number.
.Pp
.Fn pinsyscalls
is only called by the shared library linker
.Xr ld.so 1
to tell the kernel where system calls are found in the dynamic library
.Pa libc.so
(the filename is actually /usr/lib/libc.so.major.minor).
.Pp
A similar setup operation is done automatically by the kernel for
the system calls found in
.Xr ld.so 1
and in static executables.
.Pp
Once the kernel knows the specific location in the address space where
a specific system call must be entered from, any attempt to use a different
system call entry instruction to perform a non-corresponding system call
operation will fail with signal
.Dv SIGABRT .
.Sh RETURN VALUES
.Rv -std
.Sh ERRORS
.Fn pinsyscalls
will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
Process already has a system call pinning table loaded.
.It Bq Er EPERM
A static binary tried to call
.Fn pinsyscalls .
.It Bq Er ERANGE
At least one system call offset is out of bounds.
.El
.Sh HISTORY
The
.Fn pinsyscalls
system call first appeared in
.Ox 7.4 .
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