ELF_GETDATA(3) BSD Library Functions Manual ELF_GETDATA(3)
elf_getdata, elf_newdata, elf_rawdata -- iterate through or allocate section data
ELF Access Library (libelf, -lelf)
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 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
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).
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 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 argu-
ment 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
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.
These functions return a valid pointer to a data descriptor if successful, or NULL if an error occurs.
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 currently unsupported by the library.
elf(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)
January 26, 2011 BSD