From: David Laight <David.Laight@ACULAB.COM>
To: 'Josh Poimboeuf' <jpoimboe@redhat.com>,
Andy Lutomirski <luto@kernel.org>
Cc: X86 ML <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
David Kaplan <David.Kaplan@amd.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
"David Woodhouse" <dwmw2@infradead.org>,
Kees Cook <keescook@chromium.org>, "Jann Horn" <jannh@google.com>
Subject: RE: Do we need to do anything about "dead µops?"
Date: Tue, 4 May 2021 13:06:06 +0000 [thread overview]
Message-ID: <5937e5a2f1014e2da4a07e249745ceb1@AcuMS.aculab.com> (raw)
In-Reply-To: <20210504031616.covixup7rhdil3yq@treble>
From: Josh Poimboeuf
> Sent: 04 May 2021 04:16
...
> I was actually thinking more along the lines of
>
> val = 0;
>
> if (user_supplied_idx < ARRAY_SIZE) // trained to speculatively be 'true'
> val = boring_non_secret_array[user_supplied_idx];
>
> if (val & 1)
> do_something();
>
> In other words, the victim code wouldn't be accessing the secret
> intentionally. So there's no reason for it to avoid doing
> data-dependent branches.
Isn't that one of the very boring standard spectre cases?
David
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Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2021-05-04 13:06 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-01 16:26 Do we need to do anything about "dead µops?" Andy Lutomirski
2021-05-01 17:35 ` Andrew Cooper
2021-05-03 23:30 ` Josh Poimboeuf
2021-05-04 1:31 ` Andy Lutomirski
2021-05-04 3:16 ` Josh Poimboeuf
2021-05-04 13:06 ` David Laight [this message]
2021-05-04 13:24 ` Josh Poimboeuf
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