[PATCH] D20024: [ELF] - Protect first entries of got.plt with RelRo.

[Rafael Espíndola via llvm-commits]

I see that musl just does

lea _DYNAMIC(%rip),%rsi

to find its own _DYNAMIC.

I wonder if we can just drop the magical first entries.

Cheers,
Rafael


On 6 May 2016 at 14:12, Rafael Espíndola <rafael.espindola at gmail.com> wrote:
> Remind me again how the first entry works. From the ABI it looks like
> .got has to have the first entry be the value of _DYNAMIC and the
> dynamic linker can use that.
>
> But, it looks like it is actually .got.plt that has that. Also, if the
> dynamic linker can find the .got, it can find the .dynamic section,
> no?
>
> On 6 May 2016 at 13:09, George Rimar <grimar at accesssoftek.com> wrote:
>> grimar created this revision.
>> grimar added reviewers: ruiu, rafael.
>> grimar added subscribers: grimar, llvm-commits.
>> Herald added a subscriber: joker.eph.
>>
>> First entries of got.plt can be protected using RelRo technique,
>> this patch implements this by shifting got.plt to the memory page,
>> where relro is active.
>>
>> Both gold and bfd do that and it should be good for security.
>>
>> http://reviews.llvm.org/D20024
>>
>> Files:
>>   ELF/OutputSections.h
>>   ELF/Writer.cpp
>>   test/ELF/aarch64-condb-reloc.s
>>   test/ELF/aarch64-gnu-ifunc.s
>>   test/ELF/aarch64-tstbr14-reloc.s
>>   test/ELF/copy-rel-pie.s
>>   test/ELF/dynamic-reloc-index.s
>>   test/ELF/dynamic-reloc.s
>>   test/ELF/gnu-ifunc-i386.s
>>   test/ELF/gnu-ifunc.s
>>   test/ELF/lto/undefined-puts.ll
>>   test/ELF/mips-26.s
>>   test/ELF/plt-aarch64.s
>>   test/ELF/plt-i686.s
>>   test/ELF/plt.s
>>   test/ELF/relocation.s
>>   test/ELF/relro.s
>>   test/ELF/undef-with-plt-addr.s
>>