From: Julia Lawall <julia.lawall@inria.fr>
To: Wen Yang <wenyang@linux.alibaba.com>
Cc: Michal Marek <michal.lkml@markovi.net>,
Gilles Muller <Gilles.Muller@lip6.fr>,
Nicolas Palix <nicolas.palix@imag.fr>,
Matthias Maennich <maennich@google.com>,
linux-kernel@vger.kernel.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
cocci@systeme.lip6.fr
Subject: Re: [Cocci] [PATCH v3] coccinelle: semantic patch to check for inappropriate do_div() calls
Date: Sat, 11 Jan 2020 16:36:28 +0100 (CET) [thread overview]
Message-ID: <alpine.DEB.2.21.2001111633130.2568@hadrien> (raw)
In-Reply-To: <20200110131526.60180-1-wenyang@linux.alibaba.com>
On Fri, 10 Jan 2020, Wen Yang wrote:
> do_div() does a 64-by-32 division.
> When the divisor is unsigned long, u64, or s64,
> do_div() truncates it to 32 bits, this means it
> can test non-zero and be truncated to zero for division.
> This semantic patch is inspired by Mateusz Guzik's patch:
> commit b0ab99e7736a ("sched: Fix possible divide by zero in avg_atom() calculation")
>
> Signed-off-by: Wen Yang <wenyang@linux.alibaba.com>
Acked-by: Julia Lawall <julia.lawall@inria.fr>
This looks good to me.
A small detail is that you don't need the parentheses in:
@r depends on (org || report)@
julia
> Cc: Julia Lawall <julia.lawall@inria.fr>
> Cc: Gilles Muller <Gilles.Muller@lip6.fr>
> Cc: Nicolas Palix <nicolas.palix@imag.fr>
> Cc: Michal Marek <michal.lkml@markovi.net>
> Cc: Matthias Maennich <maennich@google.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: cocci@systeme.lip6.fr
> Cc: linux-kernel@vger.kernel.org
> ---
> v3:
> - also filter out safe consts for context mode.
> - cleanup code.
>
> v2:
> - add a special case for constants and checking whether the value is obviously safe and no warning is needed.
> - fix 'WARNING:' twice in each case.
> - extend the warning to say "consider using div64_xxx instead".
>
> scripts/coccinelle/misc/do_div.cocci | 155 +++++++++++++++++++++++++++
> 1 file changed, 155 insertions(+)
> create mode 100644 scripts/coccinelle/misc/do_div.cocci
>
> diff --git a/scripts/coccinelle/misc/do_div.cocci b/scripts/coccinelle/misc/do_div.cocci
> new file mode 100644
> index 000000000000..79db083c5208
> --- /dev/null
> +++ b/scripts/coccinelle/misc/do_div.cocci
> @@ -0,0 +1,155 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/// do_div() does a 64-by-32 division.
> +/// When the divisor is long, unsigned long, u64, or s64,
> +/// do_div() truncates it to 32 bits, this means it can test
> +/// non-zero and be truncated to 0 for division on 64bit platforms.
> +///
> +//# This makes an effort to find those inappropriate do_div() calls.
> +//
> +// Confidence: Moderate
> +// Copyright: (C) 2020 Wen Yang, Alibaba.
> +// Comments:
> +// Options: --no-includes --include-headers
> +
> +virtual context
> +virtual org
> +virtual report
> +
> +@initialize:python@
> +@@
> +
> +def get_digit_type_and_value(str):
> + is_digit = False
> + value = 0
> +
> + try:
> + if (str.isdigit()):
> + is_digit = True
> + value = int(str, 0)
> + elif (str.upper().endswith('ULL')):
> + is_digit = True
> + value = int(str[:-3], 0)
> + elif (str.upper().endswith('LL')):
> + is_digit = True
> + value = int(str[:-2], 0)
> + elif (str.upper().endswith('UL')):
> + is_digit = True
> + value = int(str[:-2], 0)
> + elif (str.upper().endswith('L')):
> + is_digit = True
> + value = int(str[:-1], 0)
> + elif (str.upper().endswith('U')):
> + is_digit = True
> + value = int(str[:-1], 0)
> + except Exception as e:
> + print('Error:',e)
> + is_digit = False
> + value = 0
> + finally:
> + return is_digit, value
> +
> +def filter_out_safe_constants(str):
> + is_digit, value = get_digit_type_and_value(str)
> + if (is_digit):
> + if (value >= 0x100000000):
> + return True
> + else:
> + return False
> + else:
> + return True
> +
> +def construct_warnings(suggested_fun):
> + msg="WARNING: do_div() does a 64-by-32 division, please consider using %s instead."
> + return msg % suggested_fun
> +
> +@depends on context@
> +expression f;
> +long l: script:python() { filter_out_safe_constants(l) };
> +unsigned long ul : script:python() { filter_out_safe_constants(ul) };
> +u64 ul64 : script:python() { filter_out_safe_constants(ul64) };
> +s64 sl64 : script:python() { filter_out_safe_constants(sl64) };
> +
> +@@
> +(
> +* do_div(f, l);
> +|
> +* do_div(f, ul);
> +|
> +* do_div(f, ul64);
> +|
> +* do_div(f, sl64);
> +)
> +
> +@r depends on (org || report)@
> +expression f;
> +position p;
> +long l: script:python() { filter_out_safe_constants(l) };
> +unsigned long ul : script:python() { filter_out_safe_constants(ul) };
> +u64 ul64 : script:python() { filter_out_safe_constants(ul64) };
> +s64 sl64 : script:python() { filter_out_safe_constants(sl64) };
> +@@
> +(
> +do_div@p(f, l);
> +|
> +do_div@p(f, ul);
> +|
> +do_div@p(f, ul64);
> +|
> +do_div@p(f, sl64);
> +)
> +
> +@script:python depends on org@
> +p << r.p;
> +ul << r.ul;
> +@@
> +
> +coccilib.org.print_todo(p[0], construct_warnings("div64_ul"))
> +
> +@script:python depends on org@
> +p << r.p;
> +l << r.l;
> +@@
> +
> +coccilib.org.print_todo(p[0], construct_warnings("div64_long"))
> +
> +@script:python depends on org@
> +p << r.p;
> +ul64 << r.ul64;
> +@@
> +
> +coccilib.org.print_todo(p[0], construct_warnings("div64_u64"))
> +
> +@script:python depends on org@
> +p << r.p;
> +sl64 << r.sl64;
> +@@
> +
> +coccilib.org.print_todo(p[0], construct_warnings("div64_s64"))
> +
> +@script:python depends on report@
> +p << r.p;
> +ul << r.ul;
> +@@
> +
> +coccilib.report.print_report(p[0], construct_warnings("div64_ul"))
> +
> +@script:python depends on report@
> +p << r.p;
> +l << r.l;
> +@@
> +
> +coccilib.report.print_report(p[0], construct_warnings("div64_long"))
> +
> +@script:python depends on report@
> +p << r.p;
> +sl64 << r.sl64;
> +@@
> +
> +coccilib.report.print_report(p[0], construct_warnings("div64_s64"))
> +
> +@script:python depends on report@
> +p << r.p;
> +ul64 << r.ul64;
> +@@
> +
> +coccilib.report.print_report(p[0], construct_warnings("div64_u64"))
> --
> 2.23.0
>
>
_______________________________________________
Cocci mailing list
Cocci@systeme.lip6.fr
https://systeme.lip6.fr/mailman/listinfo/cocci
next prev parent reply other threads:[~2020-01-11 15:36 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-10 13:15 [Cocci] [PATCH v3] coccinelle: semantic patch to check for inappropriate do_div() calls Wen Yang
2020-01-10 16:35 ` Markus Elfring
2020-01-11 5:06 ` Wen Yang
2020-01-11 7:30 ` [Cocci] [v3] " Markus Elfring
2020-01-11 7:44 ` Julia Lawall
2020-01-11 8:03 ` Markus Elfring
2020-01-11 15:36 ` Julia Lawall [this message]
2020-01-12 8:30 ` [Cocci] [PATCH v3] " Markus Elfring
2020-01-12 8:42 ` Julia Lawall
2020-01-12 8:49 ` [Cocci] [v3] " Markus Elfring
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=alpine.DEB.2.21.2001111633130.2568@hadrien \
--to=julia.lawall@inria.fr \
--cc=Gilles.Muller@lip6.fr \
--cc=cocci@systeme.lip6.fr \
--cc=gregkh@linuxfoundation.org \
--cc=linux-kernel@vger.kernel.org \
--cc=maennich@google.com \
--cc=michal.lkml@markovi.net \
--cc=nicolas.palix@imag.fr \
--cc=tglx@linutronix.de \
--cc=wenyang@linux.alibaba.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).