Re: [PATCH] ld.so: Handle read-only dynamic section gracefully [BZ #28340]

[Siddhesh Poyarekar <siddhesh@sourceware.org>]

On 9/16/21 9:56 AM, H.J. Lu wrote:
> On Wed, Sep 15, 2021 at 8:46 PM Siddhesh Poyarekar
> <siddhesh@sourceware.org> wrote:
>>
>> On 9/16/21 7:53 AM, H.J. Lu wrote:
>>>> What's the use case for read-only dynamic segments beyond VDSO?  That
>>>> is, in what situations would one need to load an relocatable DSO (or
>>>> execute a PIE program) that has a read-only dynamic segment?  On the
>>>> other hand for DSOs without relocations, in what situations do you see a
>>>> valid object having a read-only DYNAMIC segment?
>>>
>>> There is nothing wrong with read-only dynamic segment.
>>
>> Do you mean to say that the dynamic linker should always try to read
>> such DSOs correctly and, like the vdso, allocate a writable dynamic
>> array to work around the .dynamic section being read-only?
>>
>> I suppose if ld.so needs to handle it correctly, then it would also have
>> to read the flags of the LOAD segment that covers the DYNAMIC segment to
>> make sure that it has the right permission flags.
> 
> What if DL_RO_DYN_SECTION is always 1?
> 

That's only true for riscv and mips.  The addresses in the dynamic 
section are not updated in that case.

Siddhesh