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

Kaylee Blake klkblake@gmail.com
Mon Mar 9 00:02:39 GMT 2020 
On 9/3/20 10:16 am, H.J. Lu wrote:
> On Sun, Mar 8, 2020 at 4:35 PM Alan Modra <amodra@gmail.com> wrote:
>>
>> On Sun, Mar 08, 2020 at 11:06:33AM -0700, H.J. Lu wrote:
>>> On Sun, Mar 8, 2020 at 10:59 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>>>>
>>>> Any comments?
>>>>
>>>> Kaylee, do you have copyright paper with FSF?
>>>>
>>>> H.J.
>>>> ---
>>>> 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,
>>>
>>> It should read
>>>
>>> ---
>>> all symbols with STB_LOCAL binding are placed
>>> before symbols with other bindings and all undefined symbols are placed
>>> before defined ones,
>>> ---
>>
>> That's new to me.  I don't think there is any ordering in .dynsym
>> among non-local symbols.
> 
> I will get clarification from gABI group.
> 
>> The patch looks OK.
>>
> 

Looks like it's required by DT_GNU_HASH, from what I could find.

-- 
Kaylee Blake <klkblake@gmail.com>
C is the worst language, except for all the others.
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