Contents
What is symbol table in ELF file?
In the ELF file format, each Symbol is represented as an instance of an Elfxx_Sym structure inside a given Symbol Table. The Elements of this structure include: st_name: index in string table of symbol name. If this field is not initialized, then the symbol doesn’t have a name.
What is symbol binding?
The . global directive sets the symbol binding to STB_GLOBAL. These symbols are visible to all object files being linked, so a definition in one object file can satisfy a reference in another. If a reference to a symbol with weak binding is not satisfied (no definition of the symbol is found), this is not an error.
What are local symbols?
Local symbols are symbols, which are only known within a macro body, but not outside the macro. Symbols that are defined for the whole program, will subsequently be called “global symbols” for better understanding.
How do I read an elf file?
you can use readelf and objdump to read parts of an elf file. You can also use ‘hexdump filename’ to get a hexdump of the contents of a binary file (this is likely only useful if you like reading machine code or you are writing an assembler).
What are symbols in a library?
A symbol library is a collection of symbols. Typically the symbols in a symbol library belong to a specific group or correspond to a specific standard. Symbol libraries can be stored in a project or in a master data pool.
Where to find binary symbol table in Elf?
Let’s build it and examine the binary: It lists the symbol in the .data section of the ELF file. Page 20 of the ELF documentation defines the .data section as:
What does St _ info mean in ELF format?
For the symbol highlighted here we can see the following: st_size is set to 0 which means it won’t take up any space in the binary during execution and probably doesn’t define a variable. st_info is set to 0x03 which means the symbol type is SECTION which means its a symbol associated to a section.
Where are the symbols in Elf-unix.data?
The .data section contains the data itself, i.e. the four bytes which hold the int value 5. The .symtab section contains the symbols, i.e. the names given to various parts of the binary; the var_global_init symbol name points to the four bytes of storage in the .data section.
Where to find relocations in the ELF format?
Suffice it to say “relocations” will be found in the Relocation Tables and the symbols these refer to will be found in the ELFs Symbol Tables – I should mention also there is more than one symbol table and more than one relocation table, for nothing else than efficiency and extended capability in configuring symbol resolution.