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IABSD.fr/src/lib/libelf/elf_getdata.3
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- lib/libelf/elf_getdata.3
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.\" Copyright (c) 2006,2008,2010-2011 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: elf_getdata.3,v 1.2 2020/05/18 06:46:23 jsg Exp $ .\" .Dd April 22, 2019 .Dt ELF_GETDATA 3 .Os .Sh NAME .Nm elf_getdata , .Nm elf_newdata , .Nm elf_rawdata .Nd iterate through or allocate section data .Sh LIBRARY .Lb libelf .Sh SYNOPSIS .In libelf.h .Ft "Elf_Data *" .Fn elf_getdata "Elf_Scn *scn" "Elf_Data *data" .Ft "Elf_Data *" .Fn elf_newdata "Elf_Scn *scn" .Ft "Elf_Data *" .Fn elf_rawdata "Elf_Scn *scn" "Elf_Data *data" .Sh DESCRIPTION These functions are used to access and manipulate data descriptors associated with section descriptors. Data descriptors used by the ELF library are described in .Xr elf 3 . .Pp Function .Fn elf_getdata will return the next data descriptor associated with section descriptor .Ar scn . The returned data descriptor will be setup to contain translated data. Argument .Ar data may be NULL, in which case the function returns the first data descriptor associated with section .Ar scn . If argument .Ar data is not NULL, it must be a pointer to a data descriptor associated with section descriptor .Ar scn , and function .Fn elf_getdata will return a pointer to the next data descriptor for the section, or NULL when the end of the section's descriptor list is reached. .Pp Function .Fn elf_newdata will allocate a new data descriptor and append it to the list of data descriptors associated with section descriptor .Ar scn . The new data descriptor will be initialized as follows: .Bl -tag -width "d_version" -compact -offset indent .It Va d_align Set to 1. .It Va d_buf Initialized to NULL. .It Va d_off Set to (off_t) -1. This field is under application control if the .Dv ELF_F_LAYOUT flag was set on the ELF descriptor. .It Va d_size Set to zero. .It Va d_type Initialized to .Dv ELF_T_BYTE . .It Va d_version Set to the current working version of the library, as set by .Xr elf_version 3 . .El The application must set these values as appropriate before calling .Xr elf_update 3 . Section .Ar scn must be associated with an ELF file opened for writing. If the application has not requested full control of layout by setting the .Dv ELF_F_LAYOUT flag on descriptor .Ar elf , then the data referenced by the returned descriptor will be positioned after the existing content of the section, honoring the file alignment specified in member .Va d_align . On successful completion of a call to .Fn elf_newdata , the ELF library will mark the section .Ar scn as .Dq dirty . .Pp Function .Fn elf_rawdata is used to step through the data descriptors associated with section .Ar scn . In contrast to function .Fn elf_getdata , this function returns untranslated data. If argument .Ar data is NULL, the first data descriptor associated with section .Ar scn is returned. If argument .Ar data is not NULL, is must be a data descriptor associated with section .Ar scn , and function .Fn elf_rawdata will return the next data descriptor in the list, or NULL if no further descriptors are present. Function .Fn elf_rawdata always returns .Vt Elf_Data structures of type .Dv ELF_T_BYTE . .Ss Special handling of zero-sized and SHT_NOBITS sections For sections of type .Dv SHT_NOBITS , and for zero-sized sections, the functions .Fn elf_getdata and .Fn elf_rawdata return a pointer to a valid .Vt Elf_Data structure that has its .Va d_buf member set to NULL and its .Va d_size member set to the size of the section. .Pp If an application wishes to create a section of type .Dv SHT_NOBITS , it should add a data buffer to the section using function .Fn elf_newdata . It should then set the .Va d_buf and .Va d_size members of the returned .Vt Elf_Data structure to NULL and the desired size of the section respectively. .Sh RETURN VALUES These functions return a valid pointer to a data descriptor if successful, or NULL if an error occurs. .Sh ERRORS These functions may fail with the following errors: .Bl -tag -width "[ELF_E_RESOURCE]" .It Bq Er ELF_E_ARGUMENT Either of the arguments .Ar scn or .Ar data was NULL. .It Bq Er ELF_E_ARGUMENT The data descriptor referenced by argument .Ar data is not associated with section descriptor .Ar scn . .It Bq Er ELF_E_ARGUMENT The section denoted by argument .Ar scn had no data associated with it. .It Bq Er ELF_E_DATA Retrieval of data from the underlying object failed. .It Bq Er ELF_E_RESOURCE An out of memory condition was detected. .It Bq Er ELF_E_SECTION Section .Ar scn had type .Dv SHT_NULL . .It Bq Er ELF_E_SECTION The type of the section .Ar scn was not recognized by the library. .It Bq Er ELF_E_SECTION The size of the section .Ar scn is not a multiple of the file size for its section type. .It Bq Er ELF_E_SECTION The file offset for section .Ar scn is incorrect. .It Bq Er ELF_E_UNIMPL The section type associated with section .Ar scn is not supported. .It Bq Er ELF_E_VERSION Section .Ar scn was associated with an ELF object with an unsupported version. .El .Sh SEE ALSO .Xr elf 3 , .Xr elf_flagdata 3 , .Xr elf_flagscn 3 , .Xr elf_getscn 3 , .Xr elf_getshdr 3 , .Xr elf_newscn 3 , .Xr elf_rawfile 3 , .Xr elf_update 3 , .Xr elf_version 3 , .Xr gelf 3