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Linker and Libraries Guide     Oracle Solaris 11 Information Library
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Document Information


Part I Using the Link-Editor and Runtime Linker

1.  Introduction to the Oracle Solaris Link Editors

2.  Link-Editor

3.  Runtime Linker

4.  Shared Objects

5.  Interfaces and Versioning

6.  Establishing Dependencies with Dynamic String Tokens

Part II Quick Reference

7.  Link-Editor Quick Reference

8.  Versioning Quick Reference

Part III Advanced Topics

9.  Direct Bindings

10.  Mapfiles

11.  Extensibility Mechanisms

Part IV ELF Application Binary Interface

12.  Object File Format

File Format

Data Representation

ELF Header

ELF Identification

Data Encoding


Section Merging

Special Sections

COMDAT Section

Group Section

Capabilities Section

Hash Table Section

Move Section

Note Section

Relocation Sections

Relocation Calculations

SPARC: Relocations

SPARC: Relocation Types

64-bit SPARC: Relocation Types

x86: Relocations

32-bit x86: Relocation Types

x64: Relocation Types

String Table Section

Symbol Table Section

Symbol Values

Symbol Table Layout and Conventions

Symbol Sort Sections

Register Symbols

Syminfo Table Section

Versioning Sections

Version Definition Section

Version Dependency Section

Version Symbol Section

13.  Program Loading and Dynamic Linking

14.  Thread-Local Storage

Part V Appendices

A.  Linker and Libraries Updates and New Features

B.  System V Release 4 (Version 1) Mapfiles


Hash Table Section

A hash table consists of Elf32_Word or Elf64_Word objects that provide for symbol table access. The SHT_HASH section provides this hash table. The symbol table to which the hashing is associated is specified in the sh_link entry of the hash table's section header. Labels are used in the following figure to help explain the hash table organization, but these labels are not part of the specification.

Figure 12-4 Symbol Hash Table

image:ELF hash table information example.

The bucket array contains nbucket entries, and the chain array contains nchain entries. Indexes start at 0. Both bucket and chain hold symbol table indexes. Chain table entries parallel the symbol table. The number of symbol table entries should equal nchain, so symbol table indexes also select chain table entries.

A hashing function that accepts a symbol name, returns a value to compute a bucket index. Consequently, if the hashing function returns the value x for some name, bucket [x% nbucket] gives an index y. This index is an index into both the symbol table and the chain table. If the symbol table entry is not the name desired, chain[y] gives the next symbol table entry with the same hash value.

The chain links can be followed until the selected symbol table entry holds the desired name, or the chain entry contains the value STN_UNDEF.

The hash function is as follows.

unsigned long
elf_Hash(const unsigned char *name)
    unsigned long h = 0, g;
        while (*name)
             h = (h << 4) + *name++;
             if (g = h & 0xf0000000)
                  h ^= g >> 24;
                   h &= ~g;
        return h;