Linux Standard Base Core Specification 4.0
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12.3. Dynamic Entries

12.3.1. Introduction

As described in System V ABI, if an object file participates in dynamic linking, its program header table shall have an element of type PT_DYNAMIC. This `segment' contains the .dynamic section. A special symbol, _DYNAMIC, labels the section, which contains an array of the following structures.

typedef struct {
	Elf32_Sword	d_tag;
   	union {
   		Elf32_Word	d_val;
   		Elf32_Addr	d_ptr;
	} d_un;
} Elf32_Dyn;

extern Elf32_Dyn	_DYNAMIC[];

typedef struct {
	Elf64_Sxword	d_tag;
   	union {
   		Elf64_Xword	d_val;
   		Elf64_Addr	d_ptr;
	} d_un;
} Elf64_Dyn;

extern Elf64_Dyn	_DYNAMIC[];

Figure 12-1. Dynamic Structure

For each object with this type, d_tag controls the interpretation of d_un.

12.3.2. Dynamic Entries

12.3.2.1. ELF Dynamic Entries

The following dynamic entries are defined in the System V ABI and System V ABI Update.

DT_BIND_NOW		Process relocations of object
DT_DEBUG		For debugging; unspecified
DT_FINI		Address of termination function
DT_HASH		Address of symbol hash table
DT_HIPROC		End of processor-specific
DT_INIT		Address of init function
DT_JMPREL		Address of PLT relocs
DT_LOPROC		Start of processor-specific
DT_NEEDED		Name of needed library
DT_NULL		Marks end of dynamic section
DT_PLTREL		Type of reloc in PLT
DT_PLTRELSZ		Size in bytes of PLT relocs
DT_REL		Address of Rel relocs
DT_RELA		Address of Rela relocs
DT_RELAENT		Size of one Rela reloc
DT_RELASZ		Total size of Rela relocs
DT_RELENT		Size of one Rel reloc
DT_RELSZ		Total size of Rel relocs
DT_RPATH		Library search path
DT_SONAME		Name of shared object
DT_STRSZ		Size of string table
DT_STRTAB		Address of string table
DT_SYMBOLIC		Start symbol search here
DT_SYMENT		Size of one symbol table entry
DT_SYMTAB		Address of symbol table
DT_TEXTREL		Reloc might modify .text

12.3.2.2. Additional Dynamic Entries

An LSB conforming object may also use the following additional Dynamic Entry types.

DT_ADDRRNGHI		Values from DT_ADDRRNGLO through DT_ADDRRNGHI are reserved for definition by an archLSB.
DT_ADDRRNGLO		Values from DT_ADDRRNGLO through DT_ADDRRNGHI are reserved for definition by an archLSB.
DT_AUXILIARY		Shared object to load before self
DT_FILTER		Shared object to get values from
DT_FINI_ARRAY		The address of an array of pointers to termination functions.
DT_FINI_ARRAYSZ		Size in bytes of DT_FINI_ARRAY
DT_HIOS		Values from DT_LOOS through DT_HIOS are reserved for definition by specific operating systems.
DT_INIT_ARRAY		The address of an array of pointers to initialization functions.
DT_INIT_ARRAYSZ		Size in bytes of DT_INIT_ARRAY
DT_LOOS		Values from DT_LOOS through DT_HIOS are reserved for definition by specific operating systems.
DT_NUM		Number of dynamic entry tags defined (excepting reserved ranges).
DT_POSFLAG_1		Flags for DT_* entries, effecting the following DT_* entry
DT_RELCOUNT		All Elf32_Rel R_*_RELATIVE relocations have been placed into a single block and this entry specifies the number of entries in that block. This permits ld.so.1 to streamline the processing of RELATIVE relocations.
DT_RUNPATH		null-terminated library search path string
DT_SYMINENT		Entry size of syminfo
DT_SYMINFO		Address of the Syminfo table.
DT_SYMINSZ		Size of syminfo table (in bytes)
DT_VALRNGHI		Entries which fall between DT_VALRNGHI & DT_VALRNGLO use the Dyn.d_un.d_val field of the Elf*_Dyn structure.
DT_VALRNGLO		Entries which fall between DT_VALRNGHI & DT_VALRNGLO use the Dyn.d_un.d_val field of the Elf*_Dyn structure.
DT_VERDEF		Address of version definition table
DT_VERDEFNUM		Number of version definitions
DT_VERNEED		Address of table with needed versions
DT_VERNEEDNUM		Number of needed versions
DT_VERSYM		Address of the table provided by the .gnu.version section.