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From: Wen Yang <wenyang@linux.alibaba.com>
To: Julia Lawall <Julia.Lawall@lip6.fr>
Cc: Wen Yang <wenyang@linux.alibaba.com>,
	Julia Lawall <julia.lawall@inria.fr>,
	Gilles Muller <Gilles.Muller@lip6.fr>,
	Nicolas Palix <nicolas.palix@imag.fr>,
	Michal Marek <michal.lkml@markovi.net>,
	Matthias Maennich <maennich@google.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Masahiro Yamada <yamada.masahiro@socionext.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	cocci@systeme.lip6.fr, linux-kernel@vger.kernel.org
Subject: [PATCH v2] coccinelle: semantic patch to check for inappropriate do_div() calls
Date: Wed,  8 Jan 2020 01:02:40 +0800	[thread overview]
Message-ID: <20200107170240.47207-1-wenyang@linux.alibaba.com> (raw)

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>
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
---
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 | 169 +++++++++++++++++++++++++++
 1 file changed, 169 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..0fd904b9157f
--- /dev/null
+++ b/scripts/coccinelle/misc/do_div.cocci
@@ -0,0 +1,169 @@
+// 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 construct_warnings(str, suggested_fun):
+    msg="WARNING: do_div() does a 64-by-32 division, please consider using %s instead."
+    is_digit, value = get_digit_type_and_value(str)
+    if (is_digit):
+        if (value >= 0x100000000):
+            return  msg %(suggested_fun)
+        else:
+            return None
+    else:
+        return  msg % suggested_fun
+
+@depends on context@
+expression f;
+long l;
+unsigned long ul;
+u64 ul64;
+s64 sl64;
+
+@@
+(
+* do_div(f, l);
+|
+* do_div(f, ul);
+|
+* do_div(f, ul64);
+|
+* do_div(f, sl64);
+)
+
+@r depends on (org || report)@
+expression f;
+long l;
+unsigned long ul;
+position p;
+u64 ul64;
+s64 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;
+@@
+
+warnings = construct_warnings(ul, "div64_ul")
+if warnings != None:
+   coccilib.org.print_todo(p[0], warnings)
+
+@script:python depends on org@
+p << r.p;
+l << r.l;
+@@
+
+warnings = construct_warnings(l, "div64_long")
+if warnings != None:
+   coccilib.org.print_todo(p[0], warnings)
+
+@script:python depends on org@
+p << r.p;
+ul64 << r.ul64;
+@@
+
+warnings = construct_warnings(ul64, "div64_u64")
+if warnings != None:
+   coccilib.org.print_todo(p[0], warnings)
+
+@script:python depends on org@
+p << r.p;
+sl64 << r.sl64;
+@@
+
+warnings = construct_warnings(sl64, "div64_s64")
+if warnings != None:
+   coccilib.org.print_todo(p[0], warnings)
+
+
+@script:python depends on report@
+p << r.p;
+ul << r.ul;
+@@
+
+warnings = construct_warnings(ul, "div64_ul")
+if warnings != None:
+   coccilib.report.print_report(p[0], warnings)
+
+@script:python depends on report@
+p << r.p;
+l << r.l;
+@@
+
+warnings = construct_warnings(l, "div64_long")
+if warnings != None:
+   coccilib.report.print_report(p[0], warnings)
+
+@script:python depends on report@
+p << r.p;
+sl64 << r.sl64;
+@@
+
+warnings = construct_warnings(sl64, "div64_s64")
+if warnings != None:
+   coccilib.report.print_report(p[0], warnings)
+
+@script:python depends on report@
+p << r.p;
+ul64 << r.ul64;
+@@
+
+warnings = construct_warnings(ul64, "div64_u64")
+if warnings != None:
+   coccilib.report.print_report(p[0], warnings)
-- 
2.23.0


WARNING: multiple messages have this Message-ID
From: Wen Yang <wenyang@linux.alibaba.com>
To: Julia Lawall <Julia.Lawall@lip6.fr>
Cc: Michal Marek <michal.lkml@markovi.net>,
	Wen Yang <wenyang@linux.alibaba.com>,
	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: [Cocci] [PATCH v2] coccinelle: semantic patch to check for inappropriate do_div() calls
Date: Wed,  8 Jan 2020 01:02:40 +0800	[thread overview]
Message-ID: <20200107170240.47207-1-wenyang@linux.alibaba.com> (raw)

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>
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
---
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 | 169 +++++++++++++++++++++++++++
 1 file changed, 169 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..0fd904b9157f
--- /dev/null
+++ b/scripts/coccinelle/misc/do_div.cocci
@@ -0,0 +1,169 @@
+// 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 construct_warnings(str, suggested_fun):
+    msg="WARNING: do_div() does a 64-by-32 division, please consider using %s instead."
+    is_digit, value = get_digit_type_and_value(str)
+    if (is_digit):
+        if (value >= 0x100000000):
+            return  msg %(suggested_fun)
+        else:
+            return None
+    else:
+        return  msg % suggested_fun
+
+@depends on context@
+expression f;
+long l;
+unsigned long ul;
+u64 ul64;
+s64 sl64;
+
+@@
+(
+* do_div(f, l);
+|
+* do_div(f, ul);
+|
+* do_div(f, ul64);
+|
+* do_div(f, sl64);
+)
+
+@r depends on (org || report)@
+expression f;
+long l;
+unsigned long ul;
+position p;
+u64 ul64;
+s64 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;
+@@
+
+warnings = construct_warnings(ul, "div64_ul")
+if warnings != None:
+   coccilib.org.print_todo(p[0], warnings)
+
+@script:python depends on org@
+p << r.p;
+l << r.l;
+@@
+
+warnings = construct_warnings(l, "div64_long")
+if warnings != None:
+   coccilib.org.print_todo(p[0], warnings)
+
+@script:python depends on org@
+p << r.p;
+ul64 << r.ul64;
+@@
+
+warnings = construct_warnings(ul64, "div64_u64")
+if warnings != None:
+   coccilib.org.print_todo(p[0], warnings)
+
+@script:python depends on org@
+p << r.p;
+sl64 << r.sl64;
+@@
+
+warnings = construct_warnings(sl64, "div64_s64")
+if warnings != None:
+   coccilib.org.print_todo(p[0], warnings)
+
+
+@script:python depends on report@
+p << r.p;
+ul << r.ul;
+@@
+
+warnings = construct_warnings(ul, "div64_ul")
+if warnings != None:
+   coccilib.report.print_report(p[0], warnings)
+
+@script:python depends on report@
+p << r.p;
+l << r.l;
+@@
+
+warnings = construct_warnings(l, "div64_long")
+if warnings != None:
+   coccilib.report.print_report(p[0], warnings)
+
+@script:python depends on report@
+p << r.p;
+sl64 << r.sl64;
+@@
+
+warnings = construct_warnings(sl64, "div64_s64")
+if warnings != None:
+   coccilib.report.print_report(p[0], warnings)
+
+@script:python depends on report@
+p << r.p;
+ul64 << r.ul64;
+@@
+
+warnings = construct_warnings(ul64, "div64_u64")
+if warnings != None:
+   coccilib.report.print_report(p[0], warnings)
-- 
2.23.0

_______________________________________________
Cocci mailing list
Cocci@systeme.lip6.fr
https://systeme.lip6.fr/mailman/listinfo/cocci

             reply	other threads:[~2020-01-07 17:03 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-07 17:02 Wen Yang [this message]
2020-01-07 17:02 ` [Cocci] [PATCH v2] coccinelle: semantic patch to check for inappropriate do_div() calls Wen Yang
2020-01-07 17:25 ` Julia Lawall
2020-01-07 17:25   ` [Cocci] " Julia Lawall
2020-01-10 13:11   ` Wen Yang
2020-01-10 13:11     ` [Cocci] " Wen Yang
2020-01-09 10:35 ` Markus Elfring
2020-01-09 10:35   ` [Cocci] " Markus Elfring
2020-01-09 10:35   ` Markus Elfring
2020-01-09 10:41   ` Julia Lawall
2020-01-09 10:41     ` [Cocci] " Julia Lawall
2020-01-09 10:41     ` Julia Lawall
2020-01-09 12:00     ` [v2] " Markus Elfring
2020-01-09 12:00       ` [Cocci] " Markus Elfring
2020-01-09 12:00       ` Markus Elfring
2020-01-09 12:04       ` Julia Lawall
2020-01-09 12:04         ` [Cocci] " Julia Lawall
2020-01-09 12:04         ` Julia Lawall
2020-01-09 12:14         ` Markus Elfring
2020-01-09 12:14           ` [Cocci] " Markus Elfring
2020-01-09 12:14           ` Markus Elfring
2020-01-09 12:17           ` Julia Lawall
2020-01-09 12:17             ` [Cocci] " Julia Lawall
2020-01-09 12:17             ` Julia Lawall
2020-01-09 12:21             ` Markus Elfring
2020-01-09 12:21               ` [Cocci] " Markus Elfring
2020-01-09 12:21               ` Markus Elfring
2020-01-10 10:00 ` [PATCH v2] " Markus Elfring
2020-01-10 10:00   ` [Cocci] " Markus Elfring
2020-01-10 10:00   ` Markus Elfring
2020-01-10 12:34   ` Julia Lawall
2020-01-10 12:34     ` [Cocci] " Julia Lawall
2020-01-10 12:34     ` Julia Lawall
2020-01-10 15:46     ` [v2] coccinelle: semantic code search " Markus Elfring
2020-01-10 15:46       ` [Cocci] " Markus Elfring
2020-01-10 15:46       ` Markus Elfring

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