Date: Thu, 13 Jan 2022 22:57:20 +0100 From: Florian Weimer <fweimer@...hat.com> To: Andy Lutomirski <luto@...nel.org> Cc: linux-arch@...r.kernel.org, Linux API <linux-api@...r.kernel.org>, linux-x86_64@...r.kernel.org, kernel-hardening@...ts.openwall.com, linux-mm@...ck.org, the arch/x86 maintainers <x86@...nel.org>, musl@...ts.openwall.com, libc-alpha@...rceware.org, linux-kernel@...r.kernel.org, Dave Hansen <dave.hansen@...el.com>, Kees Cook <keescook@...omium.org>, Andrei Vagin <avagin@...il.com> Subject: Re: [PATCH v3 3/3] x86: Add test for arch_prctl(ARCH_VSYSCALL_CONTROL) * Andy Lutomirski: > On 1/5/22 08:03, Florian Weimer wrote: >> Signed-off-by: Florian Weimer <fweimer@...hat.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
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