Re: [PATCH] Add warning above get_ram_size

[Maxime Ripard <maxime.ripard@free-electrons.com>]

Hi Sascha,

Le 14/02/2013 12:35, Sascha Hauer a écrit :
> On Thu, Feb 14, 2013 at 10:40:38AM +0100, Maxime Ripard wrote:
>> Hi Sascha,
>>
>> Le 13/02/2013 18:16, Sascha Hauer a écrit :
>>> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
>>> ---
>>>  common/memsize.c |    3 +++
>>>  1 file changed, 3 insertions(+)
>>>
>>> diff --git a/common/memsize.c b/common/memsize.c
>>> index d149e41..ef6381b 100644
>>> --- a/common/memsize.c
>>> +++ b/common/memsize.c
>>> @@ -33,6 +33,9 @@
>>>   * Check memory range for valid RAM. A simple memory test determines
>>>   * the actually available RAM size between addresses `base' and
>>>   * `base + maxsize'.
>>> + *
>>> + * This function modifies the RAM. Do not use it if you're running from
>>> + * the RAM you are going to detect!
>>>   */
>>
>> Actually, I don't see how it modifies the RAM, at least permanently. The
>> values it erase are backed up, and there's no concurrency at barebox
>> level, so we are sure that the value saved will still be the one that
>> would need to be backed up at the end of the function, right?
> 
> Yes, it restores the values, but how do you make sure the function does
> not modify the instructions you are currently executing? You need bad
> luck to hit this, but sooner or later this will happen.

Ah, yes, this would be nasty indeed. Is there a way to know the end
address of barebox into RAM ? or the address it has been loaded to and
the size of its binary, so that we can just check the part that doesn't
hold barebox?

Maxime

-- 
Maxime Ripard, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com

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