From: David Sterba <dsterba@suse.cz>
To: Borislav Petkov <bp@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Pu Wen <puwen@hygon.cn>, Thomas Gleixner <tglx@linutronix.de>,
Tom Lendacky <thomas.lendacky@amd.com>,
Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
the arch/x86 maintainers <x86@kernel.org>
Subject: Re: [GIT pull] x86/urgent for 5.3-rc5
Date: Wed, 28 Aug 2019 17:20:41 +0200 [thread overview]
Message-ID: <20190828152040.GC2752@twin.jikos.cz> (raw)
In-Reply-To: <20190827173955.GI29752@zn.tnic>
On Tue, Aug 27, 2019 at 07:39:55PM +0200, Borislav Petkov wrote:
> @@ -42,5 +43,24 @@ void x86_init_rdrand(struct cpuinfo_x86 *c)
> return;
> }
> }
> +
> + /*
> + * Stupid sanity-check whether RDRAND does *actually* generate
> + * some at least random-looking data.
> + */
> + prev = tmp;
> + for (i = 0; i < SANITY_CHECK_LOOPS; i++) {
> + if (rdrand_long(&tmp)) {
> + if (prev != tmp)
> + changed++;
You could do some sort of weak statistical test like
if (popcnt(prev ^ tmp) < BITS_PER_LONG / 3)
bad++;
if (bad > TOO_BAD)
WARN(...);
this should catch same value, increments you mentioned and possibly
other trivial classes of not-so-random values.
next prev parent reply other threads:[~2019-08-28 15:20 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-25 9:43 [GIT pull] irq/urgent for 5.3-rc5 Thomas Gleixner
2019-08-25 9:43 ` [GIT pull] x86/urgent " Thomas Gleixner
2019-08-25 17:18 ` Linus Torvalds
2019-08-25 17:30 ` Borislav Petkov
2019-08-25 17:37 ` Linus Torvalds
2019-08-25 18:29 ` Borislav Petkov
2019-08-25 18:38 ` Linus Torvalds
2019-08-25 19:32 ` Borislav Petkov
2019-08-25 19:35 ` Linus Torvalds
2019-08-25 19:49 ` Borislav Petkov
2019-08-25 19:59 ` Linus Torvalds
2019-08-25 20:17 ` Borislav Petkov
2019-08-26 12:53 ` Borislav Petkov
2019-08-27 16:55 ` Linus Torvalds
2019-08-27 17:39 ` Borislav Petkov
2019-08-27 17:46 ` Linus Torvalds
2019-08-27 17:59 ` Borislav Petkov
2019-08-28 15:20 ` David Sterba [this message]
2019-08-28 15:53 ` David Sterba
2019-10-02 19:09 ` [tip: x86/cpu] x86/rdrand: Sanity-check RDRAND output tip-bot2 for Borislav Petkov
2019-08-25 17:40 ` [GIT pull] x86/urgent for 5.3-rc5 pr-tracker-bot
2019-08-25 9:43 ` [GIT pull] timers/urgent " Thomas Gleixner
2019-08-25 17:40 ` pr-tracker-bot
2019-08-25 9:43 ` [GIT pull] perf/urgent " Thomas Gleixner
2019-08-25 17:40 ` pr-tracker-bot
2019-08-25 9:43 ` [GIT pull] sched/urgent " Thomas Gleixner
2019-08-25 17:40 ` pr-tracker-bot
2019-08-25 17:40 ` [GIT pull] irq/urgent " pr-tracker-bot
-- strict thread matches above, loose matches on Subject: below --
2019-08-18 11:34 [GIT pull] efi/urgent " Thomas Gleixner
2019-08-18 11:34 ` [GIT pull] x86/urgent " Thomas Gleixner
2019-08-18 16:55 ` pr-tracker-bot
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190828152040.GC2752@twin.jikos.cz \
--to=dsterba@suse.cz \
--cc=bp@suse.de \
--cc=linux-kernel@vger.kernel.org \
--cc=puwen@hygon.cn \
--cc=tglx@linutronix.de \
--cc=thomas.lendacky@amd.com \
--cc=torvalds@linux-foundation.org \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.