[PATCH v3] elf: Canonicalize $ORIGIN in an explicit ld.so invocation [BZ 25263]

[Adhemerval Zanella Netto]

On 19/03/25 14:28, Florian Weimer wrote:
> * Adhemerval Zanella Netto:
> 
>> On 19/03/25 11:02, Adhemerval Zanella Netto wrote:
>>>
>>>
>>> On 19/03/25 09:42, Joseph Myers wrote:
>>>> This still isn't working for me; the build fails with "cannot find 
>>>> -lorigin-mod".  (Before 5291d9f1e274dd869bc0b3d044fd4cbae486893d it was 
>>>> also broken with a lint-makefiles failure.)
>>>>
>>>
>>> I forgot that rules dependencies are evaluated in no defined order. I am
>>> trying to come up a fix, the main issue is making the build with
>>> --enable-hardcoded-path-in-tests.
>>
>> I had to reinstate a custom rule to avoid the DT_NEEDED with a full path
>> and also link tst-origin with built libc:
> 
> This looks like a job for .EXTRA_PREREQS, I think:
> 
>   <https://www.gnu.org/software/make/manual/html_node/Special-Variables.html#index-_002eEXTRA_005fPREREQS-_0028prerequisites-not-added-to-automatic-variables_0029>
> 
> Unfortunately that was only added in make 4.3, which is quite recent.
> 
> I think we could add this:
> 
>  # sofini.os must be placed last since it terminates .eh_frame section.
>  build-module-helper-objlist = \
>  	$(patsubst %_pic.a,$(whole-archive) %_pic.a $(no-whole-archive),\
>  		   $(filter-out %.lds $(map-file) $(+preinit) $(+postinit) \
> + 				$(build-module-nolink) \
>  				$(elf-objpfx)sofini.os \
>  				$(link-libc-deps),$^))
> 
> 
> and then use:
> 
> LDFLAGS-tst-origin += -Wl,-rpath,\$$ORIGIN -L$(subst :, -L,$(rpath-link)) -lorigin-mod
> $(objpfx)tst-origin: $(objpfx)liborigin-mod.so
> $(objpfx)tst-origin: build-module-nolink = $(objpfx)liborigin-mod.so
> 
> But I haven't tested it.

It did not work, the $(objpfx)liborigin-mod.so still adds the full path DT_NEEDED.
It works if I just use the build-module-nolink trick, but it does back to prerequisite
order issue (even if I add $(objpfx)liborigin-mod.so in the same rule).