Special Sections

Various sections hold program and control information. Sections in the following table are used by the system and have the indicated types and attributes.

Table 12-10 ELF Special Sections

.bss

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

Comment information, typically contributed by the components of the compilation system. This section can be manipulated by mcs(1).

.data, .data1

Initialized data that contribute to the program's memory image.

.dynamic

Dynamic linking information. See Dynamic Section for details.

.dynstr

Strings needed for dynamic linking, most commonly the strings that represent the names associated with symbol table entries.

.dynsym

Dynamic linking symbol table. See Symbol Table Section for details.

.eh_frame_hdr, .eh_frame

Call frame information used to unwind the stack.

.fini

Executable instructions that contribute to a single termination function for the executable or shared object containing the section. See Initialization and Termination Routines for details.

.fini_array

An array of function pointers that contribute to a single termination array for the executable or shared object containing the section. See Initialization and Termination Routines for details.

.got

The global offset table. See Global Offset Table (Processor-Specific) for details.

.hash

Symbol hash table. See Hash Table Section for details.

.init

Executable instructions that contribute to a single initialization function for the executable or shared object containing the section. See Initialization and Termination Routines for details.

.init_array

An array of function pointers that contributes to a single initialization array for the executable or shared object containing the section. See Initialization and Termination Routines for details.

.interp

The path name of a program interpreter. See Program Interpreter for details.

.lbss

x64 specific uninitialized data. This data is similar to .bss, but provides for a section that is larger than 2 Gbytes.

.ldata, .ldata1

x64 specific initialized data. This data is similar to .data, but provides for a section that is larger than 2 Gbytes.

.lrodata, .lrodata1

x64 specific read-only data. This data is similar to .rodata, but provides for a section that is larger than 2 Gbytes.

.note

Information in the format described in Note Section.

.plt

The procedure linkage table. See Procedure Linkage Table (Processor-Specific) for details.

.preinit_array

An array of function pointers that contribute to a single pre-initialization array for the executable or shared object containing the section. See Initialization and Termination Routines for details.

.rela

Relocations that do not apply to a particular section. One use of this section is for register relocations. See Register Symbols for details.

.relname, .relaname

Relocation information, as Relocation Sections describes. If the file has a loadable segment that includes relocation, the sections' attributes include the SHF_ALLOC bit. Otherwise, that bit is off. Conventionally, name is supplied by the section to which the relocations apply. Thus, a relocation section for .text normally will have the name .rel.text or .rela.text.

.rodata, .rodata1

Read-only data that typically contribute to a non-writable segment in the process image. See Program Header for details.

.shstrtab

Section names.

.strtab

Strings, most commonly the strings that represent the names that are associated with symbol table entries. If the file has a loadable segment that includes the symbol string table, the section's attributes include the SHF_ALLOC bit. Otherwise, that bit is turned off.

.symtab

Symbol table, as Symbol Table Section describes. If the file has a loadable segment that includes the symbol table, the section's attributes include the SHF_ALLOC bit. Otherwise, that bit is turned off.

.symtab_shndx

This section holds the special symbol table section index array, as described by .symtab. The section's attributes include the SHF_ALLOC bit if the associated symbol table section does. Otherwise, that bit is turned off.

.tbss

This section holds uninitialized thread-local data that contribute to the program's memory image. By definition, the system initializes the data with zeros when the data is instantiated for each new execution flow. The section occupies no file space, as indicated by the section type, SHT_NOBITS. See Chapter 14, Thread-Local Storage for details.

.tdata, .tdata1

These sections hold initialized thread-local data that contribute to the program's memory image. A copy of its contents is instantiated by the system for each new execution flow. See Chapter 14, Thread-Local Storage for details.

.text

The text or executable instructions of a program.

.SUNW_ancillary

Ancillary group information. See Ancillary Section for details.

.SUNW_bss

Partially initialized data for shared objects that contribute to the program's memory image. The data is initialized at runtime. The section occupies no file space, as indicated by the section type SHT_NOBITS.

.SUNW_cap

Capability requirements. See Capabilities Section for details.

.SUNW_capchain

Capability chain table. See Capabilities Section for details.

.SUNW_capinfo

Capability symbol information. See Capabilities Section for details.

.SUNW_heap

The heap of a dynamic executable created from dldump(3C).

.SUNW_dynsymsort

An array of indices to symbols in the combined .SUNW_ldynsym – .dynsym symbol table. The indices are sorted to reference symbols in order of increasing address. Symbols that do not represent variables or do not represent functions are not included. In the case of redundant global symbols and weak symbols, only the weak symbol is kept. See Symbol Sort Sections for details.

.SUNW_dyntlssort

An array of indices to thread-local storage symbols in the combined .SUNW_ldynsym – .dynsym symbol table. The indices are sorted to reference symbols in order of increasing offset. Symbols that do not represent TLS variables are not included. In the case of redundant global symbols and weak symbols, only the weak symbol is kept. See Symbol Sort Sections for details.

.SUNW_ldynsym

Augments the .dynsym section. This section contains local function symbols, for use in contexts where the full .symtab section is not available. The link-editor always places the data for a .SUNW_ldynsym section immediately before, and adjacent to, the .dynsym section. Both sections always use the same .dynstr string table section. This placement and organization, allows both symbol tables to be treated as a single larger symbol table. See Symbol Table Section.

.SUNW_move

Additional information for partially initialized data. See Move Section for details.

.SUNW_reloc

Relocation information, as Relocation Sections describes. This section is a concatenation of relocation sections that provides better locality of reference of the individual relocation records. Only the offset of the relocation record is meaningful, thus the section sh_info value is zero.

.SUNW_syminfo

Additional symbol table information. See Syminfo Table Section for details.

.SUNW_version

Versioning information. See Versioning Sections for details.

Section names with a dot (.) prefix are reserved for the system, although applications can use these sections if their existing meanings are satisfactory. Applications can use names without the prefix to avoid conflicts with system sections. The object file format enables you to define sections that are not reserved. An object file can have more than one section with the same name.

Section names that are 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 that are used for e_machine. For example, .Foo.psect is the psect section defined by the FOO architecture.

Existing extensions use their historical names.