ELF_GETDATA(3) BSD Library Functions Manual ELF_GETDATA(3)NAME
elf_getdata, elf_newdata, elf_rawdata — iterate through or allocate sec‐
tion 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 asso‐
ciated with section descriptors. Data descriptors used by the ELF
library are described in elf(3).
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 con‐
trol 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).
The application must set these values as appropriate before calling
elf_update(3). 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 refer‐
enced 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 asso‐
ciated 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 func‐
tions 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 success‐
ful, or NULL if an error occurs.
ERRORS
These functions may fail with the following errors:
[ELF_E_ARGUMENT] Either of 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 associ‐
ated 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] The section type associated with section scn is 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 cur‐
rently unsupported by the library.
SEE ALSOelf(3), elf_flagdata(3), elf_flagscn(3), elf_getscn(3), elf_getshdr(3),
elf_newscn(3), elf_rawfile(3), elf_update(3), elf_version(3), gelf(3)BSD January 26, 2011 BSD
