Re: [PATCH] ld.so: command argument "--preload"

[Carlos O'Donell <carlos at redhat dot com>]

On 11/5/18 4:16 AM, David Newall wrote:
> On 24/10/18 9:24 pm, Florian Weimer wrote:
>> For some reason, the [--preload] patch as posted does not apply to
>> master.
>> 
>> I think the general approach of the patch is fine.  Could you write
>> a test case for it?
> 
> I hate to say this, but I can't work out how to write a test case.
> Normally I'd crib from something similar, but I can't find any test
> cases for any of rtld's arguments.  (In all cases where I can find
> arguments for rtld, it's not rtld that's being tested, but something
> else.)

Is elf/tst-rtld-load-self.sh a useful template?

You will need:

* 3 parts in elf/Makefile, a binary you're going to build for the
  test, and two shared objects that provide the same function, the
  default one exits with a non-zero exit code, and the preloading
  one which exits with a zero exit code.
* The test itself e.g. tst-rtld-args.sh, with a dependency on the
  DSOs and binary so they get built. It will be tests-special and
  have it's own rule to run the test, and pass in the right
  arguments along with an additional argument of the path to the
  binary to run.
* The script tst-rtld-args.sh will run the loader with --preload
  and try to load the new DSO, and run the test. It return 0 if
  it was able to successfully preload the DSO and interpose the
  function and you can catch that in your script and exit with
  a zero also to indicate the test passed e.g. just passing along
  the return code and printing some information.
 

-- 
Cheers,
Carlos.