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Subject: Re: [PATCH] lib: Add test module for CONFIG_DEBUG_VIRTUAL
To: "Luis R. Rodriguez" <mcgrof@kernel.org>,
        Juergen Gross <jgross@suse.com>
Cc: linux-kernel@vger.kernel.org, ard.biesheuvel@linaro.org,
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        Jeff Layton <jlayton@redhat.com>
References: <20170808164035.26725-1-f.fainelli@gmail.com>
 <20170808175708.GR27873@wotan.suse.de>
From: Florian Fainelli <f.fainelli@gmail.com>
Message-ID: <eabb661e-0442-b274-2c79-95bc52f2a79b@gmail.com>
Date: Tue, 8 Aug 2017 11:04:11 -0700
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On 08/08/2017 10:57 AM, Luis R. Rodriguez wrote:
> On Tue, Aug 08, 2017 at 09:40:26AM -0700, Florian Fainelli wrote:
>> Add a test module that allows testing that CONFIG_DEBUG_VIRTUAL works
>> correctly, at least that it can catch invalid calls to virt_to_phys()
>> against the non-linear kernel virtual address map.
>>
>> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
>> ---

>> +static int __init test_debug_virtual_init(void)
>> +{
>> +	phys_addr_t pa;
>> +	void *va;
>> +
>> +	va = (void *)VMALLOC_START;
>> +	pa = virt_to_phys(va);
>> +
>> +	pr_info("PA: %pa for VA: 0x%lx\n", &pa, (unsigned long)va);
>> +
>> +	foo = kzalloc(sizeof(*foo), GFP_KERNEL);
>> +	if (!foo)
>> +		return -ENOMEM;
>> +
>> +	pa = virt_to_phys(foo);
>> +	va = foo;
>> +	pr_info("PA: %pa for VA: 0x%lx\n", &pa, (unsigned long)va);
> 
> Should there be a tests here of some sort? When should this fail, why?

There is no test per-se, the kernel will produce warning with
CONFIG_DEBUG_VIRTUAL telling you that what you are doing is wrong.

> There is no docs on this self test, could one be added?

I suppose I could add one even though that just means pointing out the
code that produces the warning?
-- 
Florian