---
name: "elf_getdata"
section: "3"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["linux", "freebsd"]
url: "https://new.carta.tech/elf_getdata"
---

# elf\_getdata(3)

iterate through or allocate section data

## NAME

**elf\_getdata**, **elf\_newdata**, **elf\_rawdata** – iterate through or allocate section data

## LIBRARY

library “libelf”

## SYNOPSIS

**#include \<libelf.h\>**

*Elf\_Data \**\

**elf\_getdata**(*Elf\_Scn \*scn*, *Elf\_Data \*data*);

*Elf\_Data \**\

**elf\_newdata**(*Elf\_Scn \*scn*);

*Elf\_Data \**\

**elf\_rawdata**(*Elf\_Scn \*scn*, *Elf\_Data \*data*);

## 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 [elf(3)](/elf/3.md).

Function **elf\_getdata**() will return the next data descriptor associated with section descriptor *scn*. The returned data descriptor will be setup to contain translated data. Argument *data* may be NULL, in which case the function returns the first data descriptor associated with section *scn*. If argument *data* is not NULL, it must be a pointer to a data descriptor associated with section descriptor *scn*, and function **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.

Function **elf\_newdata**() will allocate a new data descriptor and append it to the list of data descriptors associated with section descriptor *scn*. The new data descriptor will be initialized as follows:

- *d\_align*

  Set to 1.

- *d\_buf*

  Initialized to NULL.

- *d\_off*

  Set to (off\_t) -1. This field is under application control if the ELF\_F\_LAYOUT flag was set on the ELF descriptor.

- *d\_size*

  Set to zero.

- *d\_type*

  Initialized to ELF\_T\_BYTE.

- *d\_version*

  Set to the current working version of the library, as set by [elf\_version(3)](/elf_version/3.md).

The application must set these values as appropriate before calling [elf\_update(3)](/elf_update/3.md). Section *scn* must be associated with an ELF file opened for writing. If the application has not requested full control of layout by setting the ELF\_F\_LAYOUT flag on descriptor *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 *d\_align*. On successful completion of a call to **elf\_newdata**(), the ELF library will mark the section *scn* as “dirty”.

Function **elf\_rawdata**() is used to step through the data descriptors associated with section *scn*. In contrast to function **elf\_getdata**(), this function returns untranslated data. If argument *data* is NULL, the first data descriptor associated with section *scn* is returned. If argument *data* is not NULL, is must be a data descriptor associated with section *scn*, and function **elf\_rawdata**() will return the next data descriptor in the list, or NULL if no further descriptors are present. Function **elf\_rawdata**() always returns *Elf\_Data* structures of type ELF\_T\_BYTE.

### Special handling of zero-sized and SHT\_NOBITS sections

For sections of type SHT\_NOBITS, and for zero-sized sections, the functions **elf\_getdata**() and **elf\_rawdata**() return a pointer to a valid *Elf\_Data* structure that has its *d\_buf* member set to NULL and its *d\_size* member set to the size of the section.

If an application wishes to create a section of type SHT\_NOBITS, it should add a data buffer to the section using function **elf\_newdata**(). It should then set the *d\_buf* and *d\_size* members of the returned *Elf\_Data* structure to NULL and the desired size of the section respectively.

## RETURN VALUES

These functions return a valid pointer to a data descriptor if successful, or NULL if an error occurs.

## ERRORS

These functions may fail with the following errors:

- \[ELF\_E\_ARGUMENT\]

  Either of the arguments *scn* or *data* was NULL.

- \[ELF\_E\_ARGUMENT\]

  The data descriptor referenced by argument *data* is not associated with section descriptor *scn*.

- \[ELF\_E\_ARGUMENT\]

  The section denoted by argument *scn* had no data associated with it.

- \[ELF\_E\_DATA\]

  Retrieval of data from the underlying object failed.

- \[ELF\_E\_RESOURCE\]

  An out of memory condition was detected.

- \[ELF\_E\_SECTION\]

  Section *scn* had type SHT\_NULL.

- \[ELF\_E\_SECTION\]

  The type of the section *scn* was not recognized by the library.

- \[ELF\_E\_SECTION\]

  The size of the section *scn* is not a multiple of the file size for its section type.

- \[ELF\_E\_SECTION\]

  The file offset for section *scn* is incorrect.

- \[ELF\_E\_UNIMPL\]

  The section type associated with section *scn* is not supported.

- \[ELF\_E\_VERSION\]

  Section *scn* was associated with an ELF object with an unsupported version.

## SEE ALSO

[elf(3)](/elf/3.md), [elf\_flagdata(3)](/elf_flagdata/3.md), [elf\_flagscn(3)](/elf_flagscn/3.md), [elf\_getscn(3)](/elf_getscn/3.md), elf\_getshdr(3), [elf\_newscn(3)](/elf_newscn/3.md), [elf\_rawfile(3)](/elf_rawfile/3.md), [elf\_update(3)](/elf_update/3.md), [elf\_version(3)](/elf_version/3.md), [gelf(3)](/gelf/3.md)