SYMTAB and DYNSYM tables relationship question

[Mike Frysinger]

On Wednesday, June 30, 2010 06:21:51 Vladimir Simonov wrote:
> I have ELF executable (EXE) dynamically linked with DSO (SO) on
> some dos-like OS with ELF support. Some symbol A (FUNC GLOBAL DEFAULT)
> is referenced only from SO(not from EXE itself). After link
> (by ld, binutils 2.20.1) EXE contains info about symbol A only
> in DYNSYM table. There is nothing about A in SYMTAB and .rel.text.
> As result our runtime linker is unable to find symbol A during SO
> loading. If I reference A from EXE, A appears in SYMTAB, DYNSYM
> and .rel.text and runtime works OK.
>
> Questions:
> 1. Must symbol A be in SYMTAB and .rel.text if it is not
> referenced from EXE directly? By other words, is the problem
> in ld or in runtime linker?
> 2. If the problem is in runtime linker, then is it possible
> to force such records creation without explicit reference on A
> from EXE sources? Via ld's version-script, may be options...

your ldso should be using DT_STRTAB and DT_SYMTAB for the strtab and dynsym 
sections.  you shouldnt be relying on named sections to find the symbol table.

to speak to common ELF conventions, .dyn{str,sym} contain only the important 
symbol references.  the .{sym,str}tab sections contain extended debug info and 
are usually stripped from "released" ELFs.
-mike
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