Special sections

Various sections hold program and control information. Table 8-8, ``Special sections'' shows sections that are used by the system and have the indicated types and attributes.

Table 8-8 Special sections

 ----------------------------------------------------
 Name          Type           Attributes
 ----------------------------------------------------
 .bss          SHT_NOBITS     SHF_ALLOC+SHF_WRITE
 .comment      SHT_PROGBITS   none
 .data         SHT_PROGBITS   SHF_ALLOC+SHF_WRITE
 .data1        SHT_PROGBITS   SHF_ALLOC+SHF_WRITE
 .debug        SHT_PROGBITS   none
 .dynamic      SHT_DYNAMIC    see below
 .dynstr       SHT_STRTAB     SHF_ALLOC
 .dynsym       SHT_DYNSYM     SHF_ALLOC
 .fini         SHT_PROGBITS   SHF_ALLOC+SHF_EXECINSTR
 .got          SHT_PROGBITS   see below
 .hash         SHT_HASH       SHF_ALLOC
 .init         SHT_PROGBITS   SHF_ALLOC+SHF_EXECINSTR
 .interp       SHT_PROGBITS   none
 .line         SHT_PROGBITS   none
 .note         SHT_NOTE       none
 .plt          SHT_PROGBITS   see below
 .relname      SHT_REL        see below
 .relaname     SHT_RELA       see below
 .rodata       SHT_PROGBITS   SHF_ALLOC
 .rodata1      SHT_PROGBITS   SHF_ALLOC
 .shstrtab     SHT_STRTAB     none
 .strtab       SHT_STRTAB     see below
 .symtab       SHT_SYMTAB     see below
 .text         SHT_PROGBITS   SHF_ALLOC+SHF_EXECINSTR

.bss

This section holds uninitialized data that contribute to the program's memory image. By definition, the system initializes the data with zeros when the program begins to run. The section occupies no file space, as indicated by the section type, SHT_NOBITS.

.comment

This section holds version control information.

.data and .data1

These sections hold initialized data that contribute to the program's memory image.

.debug

This section holds information for symbolic debugging. The contents are unspecified.

.dynamic

This section holds dynamic linking information. The section's attributes will include the SHF_ALLOC bit. Whether the SHF_WRITE bit is set is processor specific. See the second part of this chapter for more information.

.dynstr

This section holds strings needed for dynamic linking, most commonly the strings that represent the names associated with symbol table entries. See the second part of this chapter for more information.

.dynsym

This section holds the dynamic linking symbol table, as described in ``Symbol table''. See the second part of this chapter for more information.

.fini

This section holds executable instructions that contribute to the process termination code. When a program exits normally, the system arranges to execute the code in this section.

.got

This section holds the global offset table.

.hash

This section holds a symbol hash table. See ``Hash table'' in the second part of this chapter for more information.

.init

This section holds executable instructions that contribute to the process initialization code. When a program starts to run, the system arranges to execute the code in this section before calling the main program entry point (called main in C programs).

.interp

This section holds the path name of a program interpreter. See ``Program interpreter'' for more information.

.line

This section holds line number information for symbolic debugging, which describes the correspondence between the source program and the machine code. The contents are unspecified.

.note

This section holds information in the format described in ``Note section''.

.plt

This section holds the procedure linkage table.

.relname and .relaname

These sections hold relocation information, as described in ``Relocation''. If the file has a loadable segment that includes relocation, the sections' attributes will include the SHF_ALLOC bit; otherwise, that bit will be off. Conventionally, name is supplied by the section to which the relocations apply. Thus a relocation section for .text normally would have the name .rel.text or .rela.text.

.rodata and .rodata1

These sections hold read-only data that typically contribute to a non-writable segment in the process image. See ``Program header'' in the second part of this chapter for more information.

.shstrtab

This section holds section names.

.strtab

This section holds strings, most commonly the strings that represent the names associated with symbol table entries. If the file has a loadable segment that includes the symbol string table, the section's attributes will include the SHF_ALLOC bit; otherwise, that bit will be off.

.symtab

This section holds a symbol table, as described in ``Symbol table''. If the file has a loadable segment that includes the symbol table, the section's attributes will include the SHF_ALLOC bit; otherwise, that bit will be off.

.text

This section holds the ``text'', or executable instructions, of a program.

Section names reserved for a processor architecture are formed by placing an abbreviation of the architecture name ahead of the section name. The name should be taken from the architecture names used for e_machine. For instance .FOO.psect is the psect section defined by the FOO architecture. Existing extensions are called by their historical names.