.\" $OpenBSD: pinsyscalls.2,v 1.5 2024/04/01 19:29:16 benno Exp $
.\"
.\" Copyright (c) 2023 Theo de Raadt <deraadt@openbsd.org>
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.Dd $Mdocdate: April 1 2024 $
.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" "u_int *pintable" "int npins"
.Sh DESCRIPTION
The
.Fn pinsyscalls
system call specifies the
.Va start
to
.Va start + len
address space range where the system call entry instructions are found,
and a
.Va npins Ns
-sized array of u_int entries (indexed by the system call number)
which are offsets from the
.Va start .
.Pp
This provides the precise location for the system call instruction
required for each system call number.
Attempting to use a different system call entry instruction to perform
a non-corresponding system call operation will fail with signal
.Dv SIGABRT .
.Pp
.Fn pinsyscalls
is only called by the shared library linker
.Xr ld.so 1
to tell the kernel where the text / executable region containing
system calls is 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.
.Sh RETURN VALUES
.Rv -std
.Sh ERRORS
.Fn pinsyscalls
will fail if:
.Bl -tag -width Er
.It Bq Er E2BIG
Implausible number of system calls provided.
.It Bq Er ENOMEM
Insufficient memory to service the request.
.It Bq Er EPERM
A static binary tried to call
.Fn pinsyscalls , or it was called a second time.
.It Bq Er ERANGE
At least one system call offset is beyond the bounds of
.Ar len .
.El
.Sh HISTORY
The
.Fn pinsyscalls
system call first appeared in
.Ox 7.5 .