Re: RFC: [PATCH] ELF: Don't require section header on ELF objects

[Florian Weimer <fw@deneb.enyo.de>]

* H. J. Lu:

> Section header isn't mandatory on ELF executable nor shared library.
> This patch adds a new linker option, -z nosectionheader, to omit ELF
> section header when building an executable or shared library, adds
> an objcopy and strip option, --remove-section-header, to remove ELF
> section header from an executable or shared library.
>
> The PT_DYNAMIC segment contains DT_HASH/DT_GNU_HASH/DT_MIPS_XHASH,
> DT_STRTAB, DT_SYMTAB, DT_STRSZ and DT_SYMENT, which can be used to
> reconstruct dynamic symbol table when section header isn't available.
> For DT_HASH, the number of dynamic symbol table entries equals the
> number of chains.  For DT_GNU_HASH/DT_MIPS_XHASH, only defined symbols
> with non-STB_LOCAL indings are in hash table.  Since in dynamic symbol
> table, all symbols with STB_LOCAL binding are placed before symbols with
> other bindings and all defined symbols are placed before undefined ones,
> the highest symbol index in DT_GNU_HASH/DT_MIPS_XHASH is the highest
> dynamic symbol table index.

Does this patch enable ld to use shared objects without a section
header for linking?

I think the NEWS and manual update should clarify this.

In my opinion, it should NOT be possible to link against objects
without section headers.  Lack of section headers clearly marks the
object as a run-time only object.  This is useful if you want to
prevent developers to create DT_NEEDED dependencies on internal
libraries, for example.