.\" Copyright (c) 2005 Mark Kettenis
.\" Copyright (c) 2012 Konstantin Belousov <kib@FreeBSD.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
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.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.\"   $OpenBSD: dl_iterate_phdr.3,v 1.3 2007/05/31 19:19:48 jmc Exp $
.Dd April 5, 2021
.Dt DL_ITERATE_PHDR 3
.Os
.Sh NAME
.Nm dl_iterate_phdr
.Nd iterate over program headers
.Sh LIBRARY
For the dynamically linked binaries, the service is provided by
.Xr ld-elf.so.1 1
dynamic linker.
Statically linked programs use an implementation of
.Fn dl_iterate_phdr
from libc.
.Sh SYNOPSIS
.In link.h
.Ft int
.Fn dl_iterate_phdr "int (*callback)(struct dl_phdr_info *, size_t, void *)" "void *data"
.Sh DESCRIPTION
The
.Fn dl_iterate_phdr
function iterates over all ELF objects loaded into a process's
address space, calling
.Fa callback
for each object, passing it information about the object's
program headers and the
.Fa data
argument.
The iteration is aborted when all objects are passed, or when the next
.Fa callback
call returns non-zero value.
The information about the program headers is passed in a structure
that is defined as:
.Bd -literal
struct dl_phdr_info {
	Elf_Addr	dlpi_addr;
	const char	*dlpi_name;
	const Elf_Phdr	*dlpi_phdr;
	Elf_Half	dlpi_phnum;
	unsigned long long int dlpi_adds;
	unsigned long long int dlpi_subs;
	size_t		dlpi_tls_modid;
	void		*dlpi_tls_data;
};
.Ed
.Pp
The members of
.Li struct dl_phdr_info
have the following meaning:
.Bl -tag -width dlpi_tls_modid
.It Fa dlpi_addr
The base address at which the object is mapped into the address
space of the calling process.
.It Fa dlpi_name
The pathname of the ELF object.
.It Fa dlpi_phdr
A pointer to the object's program headers.
.It Fa dlpi_phnum
The number of program headers in the object.
.It Fa dlpi_adds
The counter of the object loads performed by the dynamic linker.
.It Fa dlpi_subs
The counter of the object unloads performed by the dynamic linker.
.It Fa dlpi_tls_modid
The TLS index of the object.
.It Fa dlpi_tls_data
A pointer to the calling thread' TLS data segment for this module,
if it was allocated,
.Dv NULL
otherwise.
.El
.Pp
Future versions of
.Fx
might add more members to this structure.
To make it possible for programs to check whether any new members have
been added, the size of the structure is passed as an second argument to
.Fa callback .
.Pp
The third argument to callback is the
.Fa data
value passed to the call to
.Fn dl_iterate_phdr ,
allowing the
.Fa callback
to have a context.
.Sh RETURN VALUES
The
.Fn dl_iterate_phdr
returns the value returned by the last
.Fa callback
call executed.
.Sh SEE ALSO
.Xr ld 1 ,
.Xr ld-elf.so.1 1 ,
.Xr dlopen 3 ,
.Xr elf 5
.Sh HISTORY
The
.Nm
function first appeared in
.Fx 7.0 .