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

[Florian Weimer]

* 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.

Thanks,
Florian