Re: [PATCH 1/2] ld: Define _edata, __bss_start, and _end only for executables

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Wed, May 30, 2018 at 5:44 PM, Alan Modra <amodra@gmail.com> wrote:
> On Wed, May 30, 2018 at 02:59:39PM -0700, H.J. Lu wrote:
>> _edata, __bss_start, and _end are defined for executables.  FreeBSD's
>> libc.so uses executable's _end to initialize curbrk.  But there is no
>> good reason to access values of _edata, __bss_start, and _end defined
>> in shared libraries.  We should define _edata, __bss_start, and _end
>> only for executables.
>
> I agree with the idea, but the patch isn't complete.  You'll need to
> look at all the target OTHER_END_SYMBOLS, OTHER_BSS_SYMBOLS, and
> OTHER_BSS_END_SYMBOLS.  For instance, elf32mep.sh defines __heap = _end
> in OTHER_END_SYMBOLS, which is going to go wrong when _end isn't
> defined in a shared library..  Ah, no, mep uses its own mep.sc so
> won't be affected by your elf.sc patch, but I'm sure you can see the
> potential problem in other targets.  So please do look for _edata,
> edata, __bss_start, _end and end in emulparams/*.sh.  A quick look
> says this patch will likely cause fails on some targets, eg. see
> elf32epiphany.sh EXECUTABLE_SYMBOLS.
>
> If you're lucky you might be able to wrap the occurrences of
> OTHER_END_SYMBOLS, OTHER_BSS_SYMBOLS, OTHER_BSS_END_SYMBOLS and
> EXECUTABLE_SYMBOLS in elf.sc with ${CREATE_SHLIB- }.
>
> Also, do test this sort of patch on a large set of ELF targets before
> posting.
>

The new set of patches are posted at

https://sourceware.org/ml/binutils/2018-06/msg00021.html


-- 
H.J.