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From: Dmitry V. Levin <ldv@altlinux.org>
To: elfutils-devel@lists.fedorahosted.org
Subject: Re: 0.161 elfutils test are failing on Linux Arch
Date: Sat, 17 Jan 2015 17:04:17 +0300
Message-ID: <20150117140416.GA10882@altlinux.org>
In-Reply-To: 1421320011.26117.11.camel@bordewijk.wildebeest.org

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On Thu, Jan 15, 2015 at 12:06:51PM +0100, Mark Wielaard wrote:
[...]
> And for the deleted test we can probably first call
> prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY, 0, 0, 0) to allow eu-stack -p
> to get at the memory image of the deleted-lib.so.

JFYI, we use the same approach in strace to make some of our tests work
properly on such systems:
http://sourceforge.net/p/strace/code/ci/master/tree/tests/set_ptracer_any.c

> I'll try to code something up and if you could test that, that would be
> awesome.
> =

> But... This is really workarounds for the testcases. Then we know the
> functionality works as intended. Except when a real user uses the dwfl
> attach library calls or eu-stack binary...
> =

> So we probably need to figure out how to really fix this. How do other
> tools and libraries work? What if a user wants to see why firefox is
> wonky and does a strace -p $(pidof firefox) or gstack $(pidof firefox).
> Are those tools also broken by default on Arch? Or do they use some
> other trick to work properly?

A consumer OS in default configuration does not allow ptrace'ing of
firefox for security reasons.  If a user wants to ptrace processes other
than direct descendants, there is no other way besides lifting the ptrace
restrictions.

Unfortunately, there is a consumer culture of wrapping in sudo any command
that fails with EPERM, but that's another problem.


-- =

ldv

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