|elf_*||Used for class-independent functions.|
|Used for functions working with 32 bit ELF objects.|
|Used for functions working with 64 bit ELF objects.|
|Elf_*||Used for class-independent data types.|
Used for command values used in a few functions.
These symbols are defined as members of the
.Vt Elf_Cmd enumeration.
|Used for error numbers.|
|Used for flags.|
These constants define the kind of file associated with an ELF
The symbols are defined by the
.Vt Elf_Kind enumeration.
These values are defined by the
.Vt Elf_Type enumeration, and denote the types of ELF data structures that can be present in an ELF object.
Applications communicate with the library using descriptors. These are:
Vt Elf An
.Vt Elf descriptor represents an ELF object or an ar(1) archive. It is allocated using one of the elf_begin or elf_memory functions. An
.Vt Elf descriptor can be used to read and write data to an ELF file. An
.Vt Elf descriptor can be associated with zero or more
.Vt Elf_Scn section descriptors.
Given an ELF descriptor, the application may retrieve the ELF objects class-dependent "Executable Header" structures using the elf32_getehdr or elf64_getehdr functions. A new Ehdr structure may be allocated using the elf64_newehdr or elf64_newehdr functions.
The "Program Header Table" associated with an ELF descriptor may be allocated using the elf32_getphdr or elf64_getphdr functions. A new program header table may be allocated or an existing table resized using the elf32_newphdr or elf64_newphdr functions.
.Vt Elf structure is opaque and has no members visible to the application.
Vt Elf_Data An
.Vt Elf_Data data structure describes an individual chunk of a ELF file as represented in memory. It has the following application visible members:
Vt uint64_t d_align The in-file alignment of the data buffer within its containing ELF section. This value must be a power of two. Vt uint64_t d_off The offset with the containing section where this descriptors data would be placed. This field will be computed by the library unless the application requests full control of the ELF objects layout. Vt uint64_t d_size The number of bytes of data in this descriptor. Vt void *d_buf A pointer to data in memory. Vt Elf_Type d_type The ELF type (see below) of the data in this descriptor. Vt unsigned int d_version The operating version for the data in this buffer.
.Vt Elf_Data descriptors are usually associated with
.Vt Elf_Scn descriptors. Existing data descriptors associated with an ELF section may be structures are retrieved using the elf_getdata function. The elf_newdata function may be used to attach new data descriptors to an ELF section.
.Vt Elf_Scn descriptors represent a section in an ELF object.
They are retrieved using the elf_getscn function. An application may iterate through the existing sections of an ELF object using the elf_nextscn function. New sections may be allocated using the elf_newscn function.
.Vt Elf_Scn descriptor is opaque and contains no application modifiable fields.
The following ELF datatypes are supported by the library.
ELF_T_ADDR Machine addresses. ELF_T_BYTE Byte data. The library will not attempt to translate byte data. ELF_T_CAP Software and hardware capability records. ELF_T_DYN Records used in a section of type SHT_DYNAMIC. ELF_T_EHDR ELF executable header. ELF_T_HALF 16-bit unsigned words. ELF_T_LWORD 64 bit unsigned words. ELF_T_MOVE ELF Move records. ELF_T_NOTE ELF Note structures. ELF_T_OFF File offsets. ELF_T_PHDR ELF program header table entries. ELF_T_REL ELF relocation entries. ELF_T_RELA ELF relocation entries with addends. ELF_T_SHDR ELF section header entries. ELF_T_SWORD Signed 32-bit words. ELF_T_SXWORD Signed 64-bit words. ELF_T_SYMINFO ELF symbol information. ELF_T_SYM ELF symbol table entries. ELF_T_VDEF Symbol version definition records. ELF_T_VNEED Symbol version requirement records. ELF_T_WORD Unsigned 32-bit words. ELF_T_XWORD Unsigned 64-bit words.
The symbol ELF_T_NUM denotes the number of Elf types known to the library.
The following table shows the mapping between ELF section types defined in elf(5) and the types supported by the library.
Section Type Library Type Description
SHT_DYNAMIC ELF_T_DYN Xo
'.dynamic' section entries. SHT_DYNSYM ELF_T_SYM Symbols for dynamic linking.
SHT_FINI_ARRAY ELF_T_ADDR Termination function pointers.
SHT_GROUP ELF_T_WORD Section group marker.
SHT_HASH ELF_T_HASH Symbol hashes.
SHT_INIT_ARRAY ELF_T_ADDR Initialization function pointers.
SHT_NOBITS ELF_T_BYTE Xo
Empty sections. See elf(5). SHT_NOTE ELF_T_NOTE ELF note records.
SHT_PREINIT_ARRAY ELF_T_ADDR Pre-initialization function pointers.
SHT_PROGBITS ELF_T_BYTE Machine code.
SHT_REL ELF_T_REL ELF relocation records.
SHT_RELA ELF_T_RELA Relocation records with addends.
SHT_STRTAB ELF_T_BYTE String tables.
SHT_SYMTAB ELF_T_SYM Symbol tables.
SHT_SYMTAB_SHNDX ELF_T_WORD Used with extended section numbering.
SHT_GNU_verdef ELF_T_VDEF Symbol version definitions.
SHT_GNU_verneed ELF_T_VNEED Symbol versioning requirements.
SHT_GNU_versym ELF_T_HALF Version symbols.
SHT_SUNW_move ELF_T_MOVE ELF move records.
SHT_SUNW_syminfo ELF_T_SYMINFO Additional symbol flags.
This section contains a brief overview of the available functionality in the ELF library. Each function listed here is described further in its own manual page.
Archive Access elf_getarsym Retrieve the archive symbol table. elf_getarhdr Retrieve the archive header for an object. elf_getbase Retrieve the offset of a member inside an archive. elf_next Iterate through an ar(1) archive. elf_rand Random access inside an ar(1) archive.
Data Structures elf_getdata Retrieve translated data for an ELF section. elf_getscn Retrieve the section descriptor for a named section. elf_ndxscn Retrieve the index for a section. elf_newdata Add a new
.Vt Elf_Data descriptor to an ELF section.
elf_newscn Add a new section descriptor to an ELF descriptor. elf_nextscn Iterate through the sections in an ELF object. elf_rawdata Retrieve untranslated data for an ELF sectino. elf_rawfile Return a pointer to the untranslated file contents for an ELF object. elf32_getehdr, elf64_getehdr Retrieve the Executable Header in an ELF object. elf32_getphdr, elf64_getphdr Retrieve the Program Header Table in an ELF object. elf32_getshdr, elf64_getshdr Retrieve the ELF section header associated with an
.Vt Elf_Scn descriptor.
elf32_newehdr, elf64_newehdr Allocate an Executable Header in an ELF object. elf32_newphdr, elf64_newphdr Allocate or resize the Program Header Table in an ELF object.
Data Translation elf32_xlatetof, elf64_xlatetof Translate an ELF data structure from its native representation to its file representation. elf32_xlatetom, elf64_xlatetom Translate an ELF data structure from its file representation to a native representation.
Error Reporting elf_errno Retrieve the current error. elf_errmsg Retrieve a human readable description of the current error.
Initialization elf_begin Opens an ar(1) archive or ELF object given a file descriptor. elf_end Close an ELF descriptor and release all its resources. elf_memory Opens an ar(1) archive or ELF object present in a memory area. elf_version Sets the operating version.
IO Control elf_cntl Manage the association between and ELF descriptor and its underlying file. elf_flagdata Mark an
.Vt Elf_Data descriptor as dirty.
elf_flagehdr Mark the ELF Executable Header in an ELF descriptor as dirty. elf_flagphdr Mark the ELF Program Header Table in an ELF descriptor as dirty. elf_flagscn Mark an
.Vt Elf_Scn descriptor as dirty.
elf_flagshdr Mark an ELF Section Header as dirty. elf_setshstrndx Set the index of the section name string table for the ELF object. elf_update Recompute ELF object layout and optionally write the modified object back to the underlying file.
Queries elf32_checksum, elf64_checkum Compute checksum of an ELF object. elf_getident Retrieve the identification bytes for an ELF object. elf_getshnum Retrieve the number of sections in an ELF object. elf_getshstrndx Retrieve the section index of the section name string table in an ELF object. elf_hash Compute the ELF hash value of a string. elf_kind Query the kind of object associated with an ELF descriptor. elf32_fsize, elf64_fsize Return the size of the file representation of an ELF type.
In the usual mode of operation, library will compute section offsets and alignments based on the contents of an ELF descriptors sections without need for further intervention by the application.
However, if the application wishes to take complete charge of the layout of the ELF file, it may set the ELF_F_LAYOUT flag on an ELF descriptor using elf_flagelf(3), following which the library will use the data offsets and alignments specified by the application when laying out the file. Application control of file layout is described further in the elf_update(3) manual page.
Gaps in between sections will be filled with the fill character set by function elf_fill.
In case an error is encountered, these library functions set an internal error number and signal the presence of the error by returning an special return value. The application can check the current error number by calling elf_errno(3). A human readable description of the recorded error is available by calling elf_errmsg(3).
The library keeps track of all
.Vt Elf_Scn and
.Vt Elf_Data descriptors associated with an ELF descriptor and recovers them when the descriptor is closed using elf_end(3). Thus the application must not call free(3) on data structures allocated by the ELF library.
Conversely the library will not free data that it has not allocated. As an example, an application may call elf_newdata(3) to allocate a new
.Vt Elf_Data descriptor and can set the d_off member of the descriptor to point to a region of memory allocated using malloc(3). It is the applications responsibility to free this area, though the library will reclaim the space used by the
.Vt Elf_Data descriptor itself.
The original ELF(3) API was developed for Unix System V. The current implementation of the ELF(3) API appeared in
.Fx 7.0 .
The ELF library was written by
.An Joseph Koshy <jkoshy@FreeBSD.org>.