CODEWITHSUNDEEP
clinuxgccdebianelf
gtech
gtech

Reputation: 65

What is meant by "dynamic tag" referred to in this text:

Copied from http://wiki.debian.org/Multiarch/LibraryPathOverview :

any directory named in the (deprecated) DT_RPATH dynamic tag of the requesting object, or, recursively, any parent object (note that DT_RPATH is ignored if DT_RUNPATH is also present)

I can't seem to find the definition of a dynamic tag anywhere.

Upvotes: 2

Views: 1231

Answers (2)

Employed Russian
Employed Russian

Reputation: 213789

Every dynamically linked ELF image (executable of type ET_EXEC or library of type ET_DYN) has a dynamic table (which you can see via objdump -p a.out or readelf -d a.out). Each entry in a table contains a set of Elf32_Dyn or Elf64_Dyn entries, and each entry has a d_tag and d_value members. Documentation here.

The dynamic tag is the d_tag entry, which is just an integer tag (DT_NEEDED, DT_STRTAB, etc.) describing what the d_value of this particular entry in the table represents.

Dynamic loader uses the dynamic table to load ELF image, find libraries that are needed by it (using DT_NEEDED and DT_RPATH or DT_RUNPATH entries), initialize it (using DT_INIT or DT_INIT_ARRAY), find symbols in it (DT_SYMTAB, DT_STRTAB, DT_HASH), relocate it, etc. etc.

Upvotes: 6

rodrigo
rodrigo

Reputation: 98446

It simply refers to the entries in the Dynamic Section (DT probably stands for Dynamic Table or something).

You can see them with the command:

$ objdump -p program

Upvotes: 1

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