linux-kernel - Re: [PATCH 4/4] test_printf: test printf family at runtime

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Date:	Mon, 28 Sep 2015 22:55:04 +0200
From:	Rasmus Villemoes <linux@...musvillemoes.dk>
To:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org,
	Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH 4/4] test_printf: test printf family at runtime

On Mon, Sep 28 2015, Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:

> On Fri, 2015-09-25 at 19:41 +0200, Rasmus Villemoes wrote:
>> This adds a simple module for testing the kernel's printf
>> facilities. Previously, some %p extensions have caused a wrong return
>> value in case the entire output didn't fit and/or been unusable in
>> kasprintf(). This should help catch such issues. Also, it should help
>> ensure that changes to the formatting algorithms don't break 
>> anything.
>> 
>> I'm not sure if we have a struct dentry or struct file lying around 
>> at
>> boot time or if we can fake one, but most %p extensions should be
>> testable, as should the ordinary number and string formatting.
>> 
>> The nature of vararg functions means we can't use a more conventional
>> table-driven approach.
>> 
>> For now, this is mostly a skeleton; contributions are very
>> welcome. Some tests are/will be slightly annoying to write, since the
>> expected output depends on stuff like CONFIG_*, sizeof(long), runtime
>> values etc.
>
> Few comments below.
>
>> +
>> +#define test(expect, fmt, ...)					\
>> +	__test(expect, strlen(expect), fmt, ##__VA_ARGS__)
>
> Would be __test_m[em] / __test_s[tr] to distinguish them by name?

Erh, no. The 'mem' version will only be used in a very few cases, and I
really want the simple name "test" for the common case.

> And might be inline function?

That'd make the vararg handling more cumbersome.

>> +static void __init
>> +test_basic(void)
>> +{
>> +	test("", "");
>> +	test("100%", "100%%");
>> +	test("xxx%yyy", "xxx%cyyy", '%');
>> +	__test("xxx\0yyy", 7, "xxx%cyyy", '\0');
>
> And such pieces will be look better
>
> __test_str("xxx%yyy", "xxx%cyyy", '%');
> __test_mem("xxx\0yyy", 7, "xxx%cyyy", '\0');

I don't agree. 

>> +
>> +static void __init
>> +netdev_features(void)
>> +{
>> +}
>> +
>> +
>
> Maybe commentary delimiter here and above where you have double empty
> line.

And say what? I can avoid double empty lines if they bother you.

>> +
>> +	return 0;
>
> Do we need this module in a memory?

I guess not. At first I thought it didn't really matter since all
functions and data are __init, but I suppose a little metadata would
stick around if loading is "successful". Will fix.

>> +
>> +MODULE_AUTHOR("Rasmus Villemoes <linux@...musvillemoes.dk>");
>> +MODULE_LICENSE("GPL");
>
> GPL or ?..

Honestly, I don't really care. Would you like BSD/GPL or what? I just
copied from the majority of MODULE_LICENSE() instances.

Rasmus
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