linux-kernel - Re: [PATCH v2] lib/test_printf.c: call wait_for_random

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Message-ID: <7c23d47c-3380-f28f-bab9-fa5dcc1a93f4@linaro.org>
Date:   Wed, 13 Jun 2018 18:42:36 +0200
From:   Thierry Escande <thierry.escande@...aro.org>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        David Miller <davem@...emloft.net>,
        Petr Mladek <pmladek@...e.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        "Tobin C . Harding" <me@...in.cc>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] lib/test_printf.c: call wait_for_random_bytes() before
 plain %p tests



On 13/06/2018 18:30, Andy Shevchenko wrote:
> On Wed, Jun 13, 2018 at 5:59 PM, Thierry Escande
> <thierry.escande@...aro.org> wrote:
>> On 13/06/2018 13:22, Andy Shevchenko wrote:
>>>
>>> On Wed, Jun 13, 2018 at 12:29 PM, Thierry Escande
>>> <thierry.escande@...aro.org> 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.
>>>> Since we cannot wait for the crng to be initialized for an undefined
>>>> time, both plain 'p' tests now accept the string "(ptrval)" as a valid
>>>> result and print a warning message.
>>>
>>>
>>> There are two possibilities:
>>>    1. (ptrval) for 32-bit case
>>>    2. (____ptrval____) for 64-bit case.
>>
>>
>>  From lib/vsprintf.c, ptr_to_id() puts "(ptrval)" into the buffer, then it
>> gets left-padded with spaces by widen_string().
> 
> Which kernel version you are trying to fix?
> 
> What I see for a long time in linux-next:
> 
> static char *ptr_to_id(char *buf, char *end, void *ptr, struct printf_spec spec)
> {
>          const char *str = sizeof(ptr) == 8 ? "(____ptrval____)" : "(ptrval)";
> ...
> 
> brought by the commit 91efafb1dd8f ("lib/vsprintf: Replace space with
> '_' before crng is ready").

I missed that one as it's not in v4.17. My bad.

Regards,
Thierry