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.\" Copyright (c) 2006,2008 Joseph Koshy. All rights reserved.
.\"
.\" 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 Joseph Koshy ``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 Joseph Koshy 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.
.\"
.\" $Id: gelf_getrel.3,v 1.2 2020/05/18 06:46:23 jsg Exp $
.\"
.Dd April 22, 2019
.Dt GELF_GETREL 3
.Os
.Sh NAME
.Nm gelf_getrel ,
.Nm gelf_update_rel
.Nd read and update ELF relocation entries
.Sh LIBRARY
.Lb libelf
.Sh SYNOPSIS
.In gelf.h
.Ft "GElf_Rel *"
.Fn gelf_getrel "Elf_Data *data" "int ndx" "GElf_Rel *rel"
.Ft int
.Fn gelf_update_rel "Elf_Data *data" "int ndx" "GElf_Rel *rel"
.Sh DESCRIPTION
These convenience functions are used to retrieve and update class-dependent
.Vt Elf32_Rel
or
.Vt Elf64_Rel
structures in an ELF object.
.Pp
Argument
.Ar data
is an
.Vt Elf_Data
descriptor associated with a section of type
.Dv SHT_REL .
Argument
.Ar ndx
is the index of the entry being retrieved or updated.
The class-independent
.Vt GElf_Rel
structure is described in
.Xr gelf 3 .
.Pp
Function
.Fn gelf_getrel
retrieves the class-dependent entry at index
.Ar ndx
in data buffer
.Ar data
and copies it to the destination pointed to by argument
.Ar rel
after translation to class-independent form.
.Pp
Function
.Fn gelf_update_rel
converts the class-independent entry pointed to
by argument
.Ar rel
to class-dependent form, and writes it to the entry at index
.Ar ndx
in the data buffer described by argument
.Ar data .
Function
.Fn gelf_update_rel
signals an error if any of the values in the class-independent
representation exceeds the representable limits of the target
type.
.Sh RETURN VALUES
Function
.Fn gelf_getrel
returns the value of argument
.Ar rel
if successful, or NULL in case of an error.
Function
.Fn gelf_update_rel
returns a non-zero value if successful, or zero in case of an error.
.Sh ERRORS
These functions may fail with the following errors:
.Bl -tag -width "[ELF_E_RESOURCE]"
.It Bq Er ELF_E_ARGUMENT
Arguments
.Ar data
or
.Ar rel
were NULL.
.It Bq Er ELF_E_ARGUMENT
Argument
.Ar ndx
was less than zero or larger than the number of entries in the data
descriptor.
.It Bq Er ELF_E_ARGUMENT
Data descriptor
.Ar data
was not associated with a section of type
.Dv SHT_REL .
.It Bq Er ELF_E_RANGE
A value was not representable in the target type.
.It Bq Er ELF_E_VERSION
The
.Vt Elf_Data
descriptor denoted by argument
.Ar data
is associated with an ELF object with an unsupported version.
.El
.Sh SEE ALSO
.Xr elf 3 ,
.Xr elf_getdata 3 ,
.Xr elf_getscn 3 ,
.Xr gelf 3
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