[PATCH] D30256: [ELF] - Implemented -z noreloc-overflow.

[Rui Ueyama via llvm-commits]

On Wed, Feb 22, 2017 at 11:08 AM, George Rimar via Phabricator <
reviews at reviews.llvm.org> wrote:

> grimar added a comment.
>
> In https://reviews.llvm.org/D30256#683650, @ruiu wrote:
>
> > The fact that the name does not correspond what it does is actually a
> bit alarming. It could be a sign that something is wrong. Did you know why
> it was named "noreloc-overflow"?
>
>
> Yes. I am sorry, now I see that patch was very confusing. They use it for
> different thing:
> https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;
> a=blob;f=bfd/elf64-x86-64.c;h=a058eca3abf03cc2f79601d170b2d6
> b9f9c459e5;hb=HEAD#l2594
> They do not allow to use some relocations as dynamic because they can
> overflow in runtime
>  and report "recompile with fPIC" error instead. To avoid that error, they
> have this flag.
> There is a single relocation in kernel I see that is fixed by that option
> for them, but we resolve this relocation statically, so at least for my
> case it was never a problem.
>
> Issue I tried to solve in this patch is different. Issue is that we
> restrict creating the relocations against RO sections. Though
> self-relocatable binaries
> for kernel wants to have that. For that case I supposed it is fine to
> ignore all kinds of checks for dynamic relocations under this option. Now I
> am not sure
> that was good idea.
>
> May be we should just allow relocations against text segment when
> --no-dynamic-linker is given ? That also solves kernel problem and
> delegates a problem
> of handling of such relocation to users generally, what should not be a
> trouble in that case, because if user specifies no-dynamic-linker, it knows
> he will
> need to handle them anyways. What do you think ?
>

Allowing relocations against text segments when -no-dynamic-linker is given
sounds too hacky and not OK. You cannot describe why it makes sense, right?
By making sense, I don't mean "because Linux kernel needs this" but
something like "-no-dynamic-linker is an option to do blah blah and
semantically it naturally implies it should allow text relocations".
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20170222/85ecfa21/attachment.html>