From: Thierry Escande <thierry.escande@linaro.org>
To: Steven Rostedt <rostedt@goodmis.org>, Petr Mladek <pmladek@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
David Miller <davem@davemloft.net>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
"Tobin C . Harding" <me@tobin.cc>,
linux-kernel@vger.kernel.org,
Andy Shevchenko <andy.shevchenko@gmail.com>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH RESEND] lib/test_printf.c: call wait_for_random_bytes() before plain %p tests
Date: Fri, 22 Jun 2018 23:50:20 +0200 [thread overview]
Message-ID: <a2f0729c-593e-b747-a22f-6468ea88882e@linaro.org> (raw)
In-Reply-To: <20180622205346.owyjk33wplzh7nhs@home.goodmis.org>
On 22/06/2018 22:53, Steven Rostedt wrote:
> On Thu, Jun 07, 2018 at 02:24:34PM +0200, Petr Mladek wrote:
>> On Mon 2018-06-04 13:37:08, Thierry Escande wrote:
>>> If the test_printf module is loaded before the crng is initialized, the
>>> plain 'p' tests will fail because the printed address will not be hashed
>>> and the buffer will contain '(ptrval)' instead.
>>> This patch adds a call to wait_for_random_bytes() before plain 'p' tests
>>> to make sure the crng is initialized.
>>
>> Hmm, my system did not boot with this patch and
>> CONFIG_TEST_PRINTF=y
>
> And neither does my test box. It killed my tests I was running, as one of the
> configs I test has this set.
>
> It appears that Andrew pulled it in and sent it to Linus, as it is in
> 4.18-rc1, and I need to now revert this patch to make my tests work.
This patch has been superseded with a v2 and a v3 pushed into Petr
printk.git tree
(https://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk.git/commit/?h=for-4.19&id=ce041c43f22298485122bab15c14d062383fbc67).
Sorry for the mess...
Regards,
Thierry
>
> -- Steve
>
>
>>
>> I guess that there was not enough entropy. It is basically a deadlock.
>> The build-in module init calls are called when SMP is enabled but
>> there is no real activity and the init calls are called sequentially.
>> Therefore there is nothing that could produce some entropy, ...
>>
>> I suggest to skip the test when crng is not ready.
>>
>> Best Regards,
>> Petr
>>
>>> Signed-off-by: Thierry Escande <thierry.escande@linaro.org>
>>> Acked-by: Tobin C. Harding <me@tobin.cc>
>>> ---
>>> lib/test_printf.c | 7 +++++++
>>> 1 file changed, 7 insertions(+)
>>>
>>> diff --git a/lib/test_printf.c b/lib/test_printf.c
>>> index 71ebfa43ad05..839be9385a8a 100644
>>> --- a/lib/test_printf.c
>>> +++ b/lib/test_printf.c
>>> @@ -260,6 +260,13 @@ plain(void)
>>> {
>>> int err;
>>>
>>> + /*
>>> + * Make sure crng is ready. Otherwise we get "(ptrval)" instead
>>> + * of a hashed address when printing '%p' in plain_hash() and
>>> + * plain_format().
>>> + */
>>> + wait_for_random_bytes();
>>> +
>>> err = plain_hash();
>>> if (err) {
>>> pr_warn("plain 'p' does not appear to be hashed\n");
>>> --
>>> 2.14.1
>>>
next prev parent reply other threads:[~2018-06-22 21:50 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-04 11:37 [PATCH RESEND] lib/test_printf.c: call wait_for_random_bytes() before plain %p tests Thierry Escande
2018-06-05 12:43 ` Andy Shevchenko
2018-06-07 12:24 ` Petr Mladek
2018-06-07 18:47 ` Thierry Escande
2018-06-08 8:04 ` Petr Mladek
2018-06-08 9:07 ` Thierry Escande
2018-06-08 9:46 ` Andy Shevchenko
2018-06-08 10:32 ` Thierry Escande
2018-06-08 11:22 ` Petr Mladek
2018-06-08 11:28 ` Thierry Escande
2018-06-22 20:53 ` Steven Rostedt
2018-06-22 21:50 ` Thierry Escande [this message]
2018-06-25 7:50 ` Petr Mladek
2018-06-25 12:04 ` Petr Mladek
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