linux-hardening - Re: [PATCH -next v3 01/10] coccinelle: Add rules to find str_true

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Message-ID: <952c42aa-001f-42f0-8ec5-eb7e592b2629@huawei.com>
Date: Mon, 23 Sep 2024 15:00:49 +0800
From: Hongbo Li <lihongbo22@...wei.com>
To: Julia Lawall <julia.lawall@...ia.fr>
CC: <kees@...nel.org>, <andy@...nel.org>, <nicolas.palix@...g.fr>,
	<linux-hardening@...r.kernel.org>, <cocci@...ia.fr>
Subject: Re: [PATCH -next v3 01/10] coccinelle: Add rules to find
 str_true_false() replacements



On 2024/9/19 14:25, Julia Lawall wrote:
> 
> 
> On Wed, 11 Sep 2024, Hongbo Li wrote:
> 
>> After str_true_false() has been introduced in the tree,
>> we can add rules for finding places where str_true_false()
>> can be used. A simple test can find over 10 locations.
>>
>> Signed-off-by: Hongbo Li <lihongbo22@...wei.com>
>> ---
>>   scripts/coccinelle/api/string_choices.cocci | 19 +++++++++++++++++++
>>   1 file changed, 19 insertions(+)
>>
>> diff --git a/scripts/coccinelle/api/string_choices.cocci b/scripts/coccinelle/api/string_choices.cocci
>> index 5e729f187f22..6942ad7c4224 100644
>> --- a/scripts/coccinelle/api/string_choices.cocci
>> +++ b/scripts/coccinelle/api/string_choices.cocci
>> @@ -85,3 +85,22 @@ e << str_down_up_r.E;
>>   @@
>>
>>   coccilib.report.print_report(p[0], "opportunity for str_down_up(%s)" % e)
>> +
>> +@..._true_false depends on patch@
>> +expression E;
>> +@@
>> +-      ((E) ? "true" : "false")
>> ++      str_true_false(E)
>> +
>> +@..._true_false_r depends on !patch exists@
>> +expression E;
>> +position P;
>> +@@
>> +*      ((E@P) ? "true" : "false")
> 
> Hello,
> 
> The semantic patch is quite slow.  Actually it tests a large number of
> cases, eg where the parentheses are present and where they are not.
> 
> A small optimization is possible in the non-patch case.  The outer
> parentheses are not needed, because you will already get the same
> information whether they are there or not.
> 
> In contrast, for the patch case, the outer parentheses are needed, because
> if they are there we want to remove them, since they are not needed for
> the function call.
> 
> Could you update the depends on !patch cases to remove the outer
> parentheses?
> 

You mean in non-patch case, we could just write like the following?:

+@..._true_false_r depends on !patch exists@
+expression E;
+position P;
+@@
+*      (E@P) ? "true" : "false"

I have tested in my machine. The impact of this parenthesis on 
performance is very minimal.

With parentheses, the time on driver/ costs:

real	1m41.696s
user	85m24.069s
sys	1m8.891s

Without parentheses, the time on driver/ costs:

real	1m40.438s
user	85m53.987s
sys	1m7.981s


Thanks,
Hongbo

> Also, just one patch would be fine.  There are many changes, but they are
> all sort of the same, so it would be easier just to see them all at once.
> 
> thanks,
> julia
> 
> 
>> +
>> +@...ipt:python depends on report@
>> +p << str_true_false_r.P;
>> +e << str_true_false_r.E;
>> +@@
>> +
>> +coccilib.report.print_report(p[0], "opportunity for str_true_false(%s)" % e)
>> --
>> 2.34.1
>>
>>