[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Tue, 8 Aug 2023 21:42:20 +0100
From: Mark Brown <broonie@...nel.org>
To: Szabolcs Nagy <Szabolcs.Nagy@....com>
Cc: Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
Jonathan Corbet <corbet@....net>,
Andrew Morton <akpm@...ux-foundation.org>,
Marc Zyngier <maz@...nel.org>,
Oliver Upton <oliver.upton@...ux.dev>,
James Morse <james.morse@....com>,
Suzuki K Poulose <suzuki.poulose@....com>,
Arnd Bergmann <arnd@...db.de>, Oleg Nesterov <oleg@...hat.com>,
Eric Biederman <ebiederm@...ssion.com>,
Kees Cook <keescook@...omium.org>,
Shuah Khan <shuah@...nel.org>,
"Rick P. Edgecombe" <rick.p.edgecombe@...el.com>,
Deepak Gupta <debug@...osinc.com>,
Ard Biesheuvel <ardb@...nel.org>,
"H.J. Lu" <hjl.tools@...il.com>,
Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>,
linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org,
kvmarm@...ts.linux.dev, linux-fsdevel@...r.kernel.org,
linux-arch@...r.kernel.org, linux-mm@...ck.org,
linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v3 21/36] arm64/mm: Implement map_shadow_stack()
On Tue, Aug 08, 2023 at 09:21:03AM +0100, Szabolcs Nagy wrote:
> The 08/07/2023 14:00, Mark Brown wrote:
> > That's not what the manual page or a quick check of the code suggest
> > that mmap() does, they say that the kernel just takes it as a hint and
> i should have said that i expect MAP_FIXED_NOREPLACE semantics
> (since the x86 code seemed to use that) and then the mapped
> address must match exactly thus page aligned.
Ah, I see. We do pass MAP_FIXED_NOREPLACE when allocating the stack if
an address was specified but currently leave it up to the VM subsystem
to figure out what to do with the address. I don't immediately see
where mmap() enforces this requirement, but I have to admit I didn't
look overly hard. I don't see a problem with enforcing a PAGE_SIZE
constraint here.
> > > > + if (size == 16 || size % 16)
> > > > + return -EINVAL;
> > > why %16 and not %8 ?
> > I don't think that's needed any more - there was some stuff in an
> > earlier version of the code but no longer.
> it's kind of important to know the exact logic so the cap token
> location can be computed in userspace for arbitrary size.
> (this is why i wanted to see the map_shadow_stack man page first
> but i was told that comes separately on linux..)
Right, I'd already changed it to % 8 in the version I posted yesterday.
Download attachment "signature.asc" of type "application/pgp-signature" (489 bytes)
Powered by blists - more mailing lists