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

[Siddhesh Poyarekar <siddhesh@sourceware.org>]

On 9/17/21 3:41 AM, H.J. Lu wrote:
>> 2. Do we want to leave .dynamic unrelocated for read-only DYNAMIC or
>> should we instead allocate an array to write relocated addresses in
>> there, like we did for vdso?
> 
> My patch removed the hack for vDSO to leave the read-only
> PT_DYNAMIC segment unrelocated.

Presuming that your rationale for this is your response from your other 
email:

> Non-glibc consumers of
> PT_DYNAMIC segment need to handle it differently for these non-ABI
> conforming binaries.

could you qualify this a bit more?  My reading of the spec[1] suggests 
that the spec is silent on whether the .dynamic entries should be 
writable, it merely says that the dynamic linker reads d_un.d_ptr and 
adds the memory base address to it when referring to those addresses. 
So calling them non-conforming seems wrong.

And if they're conforming, there seems to be little reason to make them 
different from DSOs with writable DYNAMIC segment as far as l_info data 
returned from dl_iterate_phdr is concerned.

Siddhesh

[1] https://refspecs.linuxbase.org/elf/gabi4+/ch5.dynamic.html