ELF header

Some object file control structures can grow, because the ELF header contains their actual sizes. If the object file format changes, a program may encounter control structures that are larger or smaller than expected. Programs might therefore ignore ``extra'' information. The treatment of ``missing'' information depends on context and will be specified when and if extensions are defined.

   #define EI_NIDENT	16
   

   typedef struct {
   	unsigned char	e_ident[EI_NIDENT];
   	Elf32_Half	e_type;
   	Elf32_Half	e_machine;
   	Elf32_Word	e_version;
   	Elf32_Addr	e_entry;
   	Elf32_Off	e_phoff;
   	Elf32_Off	e_shoff;
   	Elf32_Word	e_flags;
   	Elf32_Half	e_ehsize;
   	Elf32_Half	e_phentsize;
   	Elf32_Half	e_phnum;
   	Elf32_Half	e_shentsize;
   	Elf32_Half	e_shnum;
   	Elf32_Half	e_shstrndx;
   } Elf32_Ehdr;
   

   typedef struct {
   	unsigned char	e_ident[EI_NIDENT];
   	Elf64_Half	e_type;
   	Elf64_Half	e_machine;
   	Elf64_Word	e_version;
   	Elf64_Addr	e_entry;
   	Elf64_Off	e_phoff;
   	Elf64_Off	e_shoff;
   	Elf64_Word	e_flags;
   	Elf64_Half	e_ehsize;
   	Elf64_Half	e_phentsize;
   	Elf64_Half	e_phnum;
   	Elf64_Half	e_shentsize;
   	Elf64_Half	e_shnum;
   	Elf64_Half	e_shstrndx;
   } Elf64_Ehdr;

ELF header

e_ident

The initial bytes mark the file as an object file and provide machine-independent data with which to decode and interpret the file's contents. Complete descriptions appear in ``ELF identification''.

e_type

This member identifies the object file type.

Name	Value	Meaning
ET_NONE	0	No file type
ET_REL	1	Relocatable file
ET_EXEC	2	Executable file
ET_DYN	3	Shared object file
ET_CORE	4	Core file
ET_LOOS	0xff00	Operating system-specific
ET_HIOS	0xff00	Operating system-specific
ET_LOPROC	0xff00	Processor-specific
ET_HIPROC	0xffff	Processor-specific

Although the core file contents are unspecified, type ET_CORE is reserved to mark the file. Values from ET_LOOS through ET_HIOS (inclusive) are reserved for operating system-specific semantics. Values from ET_LOPROC through ET_HIPROC (inclusive) are reserved for processor-specific semantics. If meanings are specified, the processor supplement explains them. Other values are reserved and will be assigned to new object file types as necessary.

e_machine

This member's value specifies the required architecture for an individual file.

Name	Value	Meaning
EM_NONE	0	No machine
EM_M32	1	AT&T WE 32100
EM_SPARC	2	SPARC
EM_386	3	Intel 80386
EM_68K	4	Motorola 68000
EM_88K	5	Motorola 88000
RESERVED	6	Reserved for future use
EM_860	7	Intel 80860
EM_MIPS	8	MIPS I Architecture
EM_S370	9	IBM System/370 Processor
EM_MIPS_RS3_LE	10	MIPS RS3000 Little-endian
RESERVED	11-14	Reserved for future use
EM_PARISC	15	Hewlett-Packard PA-RISC
RESERVED	16	Reserved for future use
EM_VPP500	17	Fujitsu VPP500
EM_SPARC32PLUS	18	Enhanced instruction set SPARC
EM_960	19	Intel 80960
EM_PPC	20	PowerPC
EM_PPC64	21	64-bit PowerPC
RESERVED	22-35	Reserved for future use
EM_V800	36	NEC V800
EM_FR20	37	Fujitsu FR20
EM_RH32	38	TRW RH-32
EM_RCE	39	Motorola RCE
EM_ARM	40	Advanced RISC Machines ARM
EM_ALPHA	41	Digital Alpha
EM_SH	42	Hitachi SH
EM_SPARCV9	43	SPARC Version 9
EM_TRICORE	44	Siemens Tricore embedded processor
EM_ARC	45	Argonaut RISC Core, Argonaut Technologies Inc.
EM_H8_300	46	Hitachi H8/300
EM_H8_300H	47	Hitachi H8/300H
EM_H8S	48	Hitachi H8S
EM_H8_500	49	Hitachi H8/500
EM_IA_64	50	Intel IA-64 processor architecture
EM_MIPS_X	51	Stanford MIPS-X
EM_COLDFIRE	52	Motorola ColdFire
EM_68HC12	53	Motorola M68HC12
EM_MMA	54	Fujitsu MMA Multimedia Accelerator
EM_PCP	55	Siemens PCP
EM_NCPU	56	Sony nCPU embedded RISC processor
EM_NDR1	57	Denso NDR1 microprocessor
EM_STARCORE	58	Motorola Star*Core processor
EM_ME16	59	Toyota ME16 processor
EM_ST100	60	STMicroelectronics ST100 processor
EM_TINYJ	61	Advanced Logic Corp. TinyJ embedded processor family
Reserved	62-65	Reserved for future use
EM_FX66	66	Siemens FX66 microcontroller
EM_ST9PLUS	67	STMicroelectronics ST9+ 8/16 bit microcontroller
EM_ST7	68	STMicroelectronics ST7 8-bit microcontroller
EM_68HC16	69	Motorola MC68HC16 Microcontroller
EM_68HC11	70	Motorola MC68HC11 Microcontroller
EM_68HC08	71	Motorola MC68HC08 Microcontroller
EM_68HC05	72	Motorola MC68HC05 Microcontroller
EM_SVX	73	Silicon Graphics SVx
EM_ST19	74	STMicroelectronics ST19 8-bit microcontroller
EM_VAX	75	Digital VAX
EM_CRIS	76	Axis Communications 32-bit embedded processor
EM_JAVELIN	77	Infineon Technologies 32-bit embedded processor
EM_FIREPATH	78	Element 14 64-bit DSP Processor
EM_ZSP	79	LSI Logic 16-bit DSP Processor

Other values are reserved and will be assigned to new machines as necessary. Processor-specific ELF names use the machine name to distinguish them. For example, the flags mentioned in the next table use the prefix EF_; a flag named WIDGET for the EM_XYZ machine would be called EM_XYZ_WIDGET.

e_version

This member identifies the object file version.

Name	Value	Meaning
EV_NONE	0	Invalid version
EV_CURRENT	1	Current version

The value ``1'' signifies the original file format; extensions will create new versions with higher numbers. Although the value of ``EV_CURRENT'' is shown as 1 in the previous table, it will change as necessary to reflect the current version number.

e_entry

This member gives the virtual address to which the system first transfers control, thus starting the process. If the file has no associated entry point, this member holds zero.

e_phoff

This member holds the program header table's file offset in bytes. If the file has no program header table, this member holds zero.

e_shoff

This member holds the section header table's file offset in bytes. If the file has no section header table, this member holds zero.

e_flags

This member holds processor-specific flags associated with the file. Flag names take the form EF_machine_flag.

e_ehsize

This member holds the ELF header's size in bytes.

e_phentsize

This member holds the size in bytes of one entry in the file's program header table; all entries are the same size.

e_phnum

This member holds the number of entries in the program header table. Thus the product of e_phentsize and e_phnum gives the table's size in bytes. If a file has no program header table, e_phnum holds the value zero.

e_shentsize

This member holds a section header's size in bytes. A section header is one entry in the section header table; all entries are the same size.

e_shnum

This member holds the number of entries in the section header table. Thus the product of e_shentsize and e_shnum gives the section header table's size in bytes. If a file has no section header table, e_shnum holds the value zero.

e_shstrndx

This member holds the section header table index of the entry associated with the section name string table. If the file has no section name string table, this member holds the value SHN_UNDEF.

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NOTE: See ``Sections'' and ``String table'' for more information.

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