ELF_GETDATA(3) BSD Library Functions Manual ELF_GETDATA(3)
elf_getdata, elf_newdata, elf_rawdata -- iterate through or allocate section data
elf_getdata(Elf_Scn *scn, Elf_Data *data);
elf_rawdata(Elf_Scn *scn, Elf_Data *data);
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).
Function elf_getdata() will return the next data descriptor associated with section descrip-
tor 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 ini-
tialized 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
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 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 com-
pletion 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 fur-
ther descriptors are present. Function elf_rawdata() always returns Elf_Data structures of
Special handling of SHT_NOBITS sections
For sections of type SHT_NOBITS, 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 mem-
bers of the returned Elf_Data structure to NULL and the desired size of the section respec-
These functions return a valid pointer to a data descriptor if successful, or NULL if an
These functions may fail with the following errors:
[ELF_E_ARGUMENT] Arguments scn was NULL, or data descriptor data was not associated with
section descriptor scn.
[ELF_E_RESOURCE] An out of memory condition was detected.
elf(3), elf_flagdata(3), elf_flagscn(3), elf_getscn(3), elf_getshdr(3), elf_newscn(3),
elf_update(3), elf_version(3), gelf(3)
BSD April 7, 2008 BSD