Re: [PATCH 2/2] Test stepping within a runtime loader / dynamic linker

[John Baldwin <jhb@FreeBSD.org>]

On 10/7/22 8:57 PM, Kevin Buettner via Gdb-patches wrote:
> See the remarks in rtld-step.exp for a description of what this
> test is about.
> 
> This test case has been tested using gcc on the following x86-64 Linux
> distributions/releases:
> 
>      Fedora 28
>      Fedora 32
>      Fedora 33
>      Fedora 34
>      Fedora 35
>      Fedora 36
>      Fedora 37
>      rawhide (f38)
>      RHEL 9.1
>      Ubuntu 22.04.1 LTS
> 
> It's also been tested (and found to be working) with
> RUNTESTFLAGS="CC_FOR_TARGET=clang" on all of the above expect for
> Fedora 28.  The (old) version of clang available on F28 did not
> accept the -static-pie option.
> 
> I also tried to make this test work on FreeBSD 13.1.  While I think I
> made significant progress, I was ultimately stymied by this message
> which occurs when attempting to run the main program which has been
> set to use the fake/pretend RTLD as the ELF interpreter:
> 
> ELF interpreter /path/to/rtld-step-rtld not found, error 22
> 
> I have left one of the flags (-static) in place which I believe
> to be needed for FreeBSD (though since I never got it to work, I
> don't know for sure.)  I've also left some declarations needed
> for FreeBSD in rtld-step-rtld.c.  They're currently disabled via
> a #if 0; you'll need to enable them if you want to try to make
> it work on FreeBSD.

Hmm, thanks for testing on FreeBSD.  FreeBSD currently doesn't support
static PIE binaries, so I think the failure you ran into is not
unexpected.

In terms of the feature, this is indeed useful (I sometimes need to
step inside rtld myself).  I think your implementation in patch 1 makes
sense.

-- 
John Baldwin