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From: Florian Weimer <fweimer@redhat.com>
To: Andy Lutomirski <luto@kernel.org>
Cc: linux-arch@vger.kernel.org,
	 Linux API <linux-api@vger.kernel.org>,
	linux-x86_64@vger.kernel.org,
	 kernel-hardening@lists.openwall.com, linux-mm@kvack.org,
	 the arch/x86 maintainers <x86@kernel.org>,
	musl@lists.openwall.com,  libc-alpha@sourceware.org,
	linux-kernel@vger.kernel.org,
	 Dave Hansen <dave.hansen@intel.com>,
	 Kees Cook <keescook@chromium.org>,
	 Andrei Vagin <avagin@gmail.com>
Subject: [musl] Re: [PATCH v3 3/3] x86: Add test for arch_prctl(ARCH_VSYSCALL_CONTROL)
Date: Thu, 13 Jan 2022 22:57:20 +0100	[thread overview]
Message-ID: <87pmovxprz.fsf@oldenburg.str.redhat.com> (raw)
In-Reply-To: <4db8cff9-8bf8-0c45-6956-4b1b19b53b2f@kernel.org> (Andy Lutomirski's message of "Thu, 13 Jan 2022 13:31:04 -0800")

* Andy Lutomirski:

> On 1/5/22 08:03, Florian Weimer wrote:
>> Signed-off-by: Florian Weimer <fweimer@redhat.com>
>
> This seems like a respectable test case, but why does it work so hard
> to avoid using libc?

Back when this was still a true lockout and not a toggle, it was
necessary to bypass the startup code, so that the test still works once
the (g)libc startup starts activating the lockout.  The /proc mounting
is there to support running as init in a VM (which makes development so
much easier).

I could ditch the /proc mounting, perform some limited data gathering in
a pre-_start routine, undo a potential lockout before the tests, and
then use libc functions for the actual test.  It would probably be a bit
less code (printf is nice), but I'd probably have to use direct system
calls for the early data gathering anyway, so those parts would still be
there.

Thanks,
Florian


  reply	other threads:[~2022-01-13 21:57 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-05 16:02 [musl] [PATCH v3 1/3] x86: Implement arch_prctl(ARCH_VSYSCALL_CONTROL) to disable vsyscall Florian Weimer
2022-01-05 16:03 ` [musl] [PATCH v3 2/3] selftests/x86/Makefile: Support per-target $(LIBS) configuration Florian Weimer
2022-01-05 16:03   ` [musl] [PATCH v3 3/3] x86: Add test for arch_prctl(ARCH_VSYSCALL_CONTROL) Florian Weimer
2022-01-13 21:31     ` [musl] " Andy Lutomirski
2022-01-13 21:57       ` Florian Weimer [this message]
2022-01-13 21:31   ` [musl] Re: [PATCH v3 2/3] selftests/x86/Makefile: Support per-target $(LIBS) configuration Andy Lutomirski
2022-01-13 22:00     ` Florian Weimer
2022-01-14  2:34       ` Andy Lutomirski
2022-01-14 13:28         ` Florian Weimer
2022-01-13 17:27 ` [musl] Re: [PATCH v3 1/3] x86: Implement arch_prctl(ARCH_VSYSCALL_CONTROL) to disable vsyscall Florian Weimer
2022-01-13 21:47 ` Andy Lutomirski
2022-01-14 13:36   ` Florian Weimer

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