ae500c1ff8
Highlights: - Make sure that only TLS sections are sorted into TLS segment. - Fixed multiple errors in "Section to Segment mapping". - Man page updates - ar improvements - elfcopy: avoid filter_reloc uninitialized variable for rela - elfcopy: avoid stripping relocations from static binaries - readelf: avoid printing directory in front of absolute path - readelf: add NT_FREEBSD_FEATURE_CTL FreeBSD note type - test improvements NOTES: Some of these changes originated in FreeBSD and simply reduce diffs between contrib and vendor. ELF Tool Chain ar is not (currently) used in FreeBSD, and there are improvements in both FreeBSD and ELF Tool Chain ar that are not in the other. Sponsored by: The FreeBSD Foundation
230 lines
6.2 KiB
Groff
230 lines
6.2 KiB
Groff
.\" Copyright (c) 2006,2008,2010-2011 Joseph Koshy. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" This software is provided by Joseph Koshy ``as is'' and
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.\" any express or implied warranties, including, but not limited to, the
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.\" implied warranties of merchantability and fitness for a particular purpose
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.\" are disclaimed. in no event shall Joseph Koshy be liable
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.\" for any direct, indirect, incidental, special, exemplary, or consequential
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.\" damages (including, but not limited to, procurement of substitute goods
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.\" or services; loss of use, data, or profits; or business interruption)
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.\" however caused and on any theory of liability, whether in contract, strict
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.\" liability, or tort (including negligence or otherwise) arising in any way
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.\" out of the use of this software, even if advised of the possibility of
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.\" such damage.
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.\"
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.\" $Id: elf_getdata.3 3643 2018-10-14 21:09:24Z jkoshy $
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.\"
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.Dd January 26, 2011
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.Dt ELF_GETDATA 3
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.Os
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.Sh NAME
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.Nm elf_getdata ,
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.Nm elf_newdata ,
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.Nm elf_rawdata
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.Nd iterate through or allocate section data
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.Sh LIBRARY
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.Lb libelf
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.Sh SYNOPSIS
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.In libelf.h
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.Ft "Elf_Data *"
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.Fn elf_getdata "Elf_Scn *scn" "Elf_Data *data"
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.Ft "Elf_Data *"
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.Fn elf_newdata "Elf_Scn *scn"
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.Ft "Elf_Data *"
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.Fn elf_rawdata "Elf_Scn *scn" "Elf_Data *data"
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.Sh DESCRIPTION
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These functions are used to access and manipulate data descriptors
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associated with section descriptors.
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Data descriptors used by the ELF library are described in
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.Xr elf 3 .
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.Pp
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Function
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.Fn elf_getdata
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will return the next data descriptor associated with section descriptor
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.Ar scn .
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The returned data descriptor will be setup to contain translated data.
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Argument
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.Ar data
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may be NULL, in which case the function returns the first data descriptor
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associated with section
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.Ar scn .
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If argument
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.Ar data
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is not NULL, it must be a pointer to a data descriptor associated with
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section descriptor
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.Ar scn ,
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and function
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.Fn elf_getdata
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will return a pointer to the next data descriptor for the section,
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or NULL when the end of the section's descriptor list is reached.
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.Pp
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Function
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.Fn elf_newdata
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will allocate a new data descriptor and append it to the list of data
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descriptors associated with section descriptor
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.Ar scn .
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The new data descriptor will be initialized as follows:
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.Bl -tag -width "d_version" -compact -offset indent
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.It Va d_align
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Set to 1.
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.It Va d_buf
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Initialized to NULL.
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.It Va d_off
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Set to (off_t) -1.
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This field is under application control if the
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.Dv ELF_F_LAYOUT
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flag was set on the ELF descriptor.
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.It Va d_size
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Set to zero.
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.It Va d_type
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Initialized to
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.Dv ELF_T_BYTE .
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.It Va d_version
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Set to the current working version of the library, as set by
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.Xr elf_version 3 .
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.El
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The application must set these values as appropriate before
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calling
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.Xr elf_update 3 .
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Section
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.Ar scn
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must be associated with an ELF file opened for writing.
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If the application has not requested full control of layout by
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setting the
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.Dv ELF_F_LAYOUT
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flag on descriptor
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.Ar elf ,
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then the data referenced by the returned descriptor will be positioned
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after the existing content of the section, honoring the file alignment
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specified in member
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.Va d_align .
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On successful completion of a call to
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.Fn elf_newdata ,
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the ELF library will mark the section
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.Ar scn
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as
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.Dq dirty .
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.Pp
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Function
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.Fn elf_rawdata
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is used to step through the data descriptors associated with
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section
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.Ar scn .
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In contrast to function
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.Fn elf_getdata ,
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this function returns untranslated data.
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If argument
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.Ar data
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is NULL, the first data descriptor associated with section
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.Ar scn
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is returned.
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If argument
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.Ar data
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is not NULL, is must be a data descriptor associated with
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section
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.Ar scn ,
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and function
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.Fn elf_rawdata
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will return the next data descriptor in the list, or NULL
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if no further descriptors are present.
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Function
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.Fn elf_rawdata
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always returns
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.Vt Elf_Data
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structures of type
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.Dv ELF_T_BYTE .
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.Ss Special handling of zero-sized and SHT_NOBITS sections
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For sections of type
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.Dv SHT_NOBITS ,
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and for zero-sized sections,
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the functions
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.Fn elf_getdata
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and
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.Fn elf_rawdata
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return a pointer to a valid
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.Vt Elf_Data
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structure that has its
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.Va d_buf
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member set to NULL and its
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.Va d_size
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member set to the size of the section.
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.Pp
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If an application wishes to create a section of type
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.Dv SHT_NOBITS ,
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it should add a data buffer to the section using function
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.Fn elf_newdata .
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It should then set the
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.Va d_buf
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and
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.Va d_size
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members of the returned
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.Vt Elf_Data
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structure to NULL and the desired size of the section respectively.
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.Sh RETURN VALUES
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These functions return a valid pointer to a data descriptor if successful, or
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NULL if an error occurs.
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.Sh ERRORS
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These functions may fail with the following errors:
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.Bl -tag -width "[ELF_E_RESOURCE]"
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.It Bq Er ELF_E_ARGUMENT
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Either of the arguments
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.Ar scn
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or
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.Ar data
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was NULL.
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.It Bq Er ELF_E_ARGUMENT
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The data descriptor referenced by argument
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.Ar data
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is not associated with section descriptor
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.Ar scn .
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.It Bq Er ELF_E_ARGUMENT
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The section denoted by argument
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.Ar scn
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had no data associated with it.
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.It Bq Er ELF_E_DATA
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Retrieval of data from the underlying object failed.
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.It Bq Er ELF_E_RESOURCE
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An out of memory condition was detected.
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.It Bq Er ELF_E_SECTION
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Section
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.Ar scn
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had type
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.Dv SHT_NULL .
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.It Bq Er ELF_E_SECTION
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The type of the section
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.Ar scn
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was not recognized by the library.
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.It Bq Er ELF_E_SECTION
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The size of the section
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.Ar scn
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is not a multiple of the file size for its section type.
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.It Bq Er ELF_E_SECTION
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The file offset for section
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.Ar scn
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is incorrect.
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.It Bq Er ELF_E_UNIMPL
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The section type associated with section
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.Ar scn
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is currently unsupported by the library.
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.El
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.Sh SEE ALSO
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.Xr elf 3 ,
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.Xr elf_flagdata 3 ,
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.Xr elf_flagscn 3 ,
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.Xr elf_getscn 3 ,
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.Xr elf_getshdr 3 ,
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.Xr elf_newscn 3 ,
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.Xr elf_rawfile 3 ,
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.Xr elf_update 3 ,
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.Xr elf_version 3 ,
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.Xr gelf 3
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