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

[Rui Ueyama via llvm-commits]

Why does it work for other linkers? Do they just allow text relocations by
default?

On Wed, Feb 22, 2017 at 12:11 PM, Rui Ueyama <ruiu at google.com> wrote:

> 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=a058eca3abf03cc2f79601d170b2d6b9
>> f9c459e5;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".
>
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