Commit 68e4cd17e218 ("docs: deprecated.rst: Add zero-length and one-element
arrays") marks one-element and zero-length arrays as deprecated. Kernel
code should always use "flexible array members" instead.
The script warns about one-element and zero-length arrays in structs.
Cc: Kees Cook <[email protected]>
Cc: Gustavo A. R. Silva <[email protected]>
Signed-off-by: Denis Efremov <[email protected]>
---
Currently, it's just a draft. I've placed a number of questions in the
script and marked them as TODO. Kees, Gustavo, if you could help me with
my questions I think that this rule will be enough to close:
https://github.com/KSPP/linux/issues/76
BTW, I it's possible to not warn about files in uapi folder if
this is relevant. Do I need to do it in the script?
scripts/coccinelle/misc/flexible_array.cocci | 158 +++++++++++++++++++
1 file changed, 158 insertions(+)
create mode 100644 scripts/coccinelle/misc/flexible_array.cocci
diff --git a/scripts/coccinelle/misc/flexible_array.cocci b/scripts/coccinelle/misc/flexible_array.cocci
new file mode 100644
index 000000000000..1e7165c79e60
--- /dev/null
+++ b/scripts/coccinelle/misc/flexible_array.cocci
@@ -0,0 +1,158 @@
+// SPDX-License-Identifier: GPL-2.0-only
+///
+/// Zero-length and one-element arrays are deprecated, see
+/// Documentation/process/deprecated.rst
+/// Flexible-array members should be used instead.
+///
+//
+// Confidence: High
+// Copyright: (C) 2020 Denis Efremov ISPRAS.
+// Comments:
+// Options: --no-includes --include-headers
+
+virtual context
+virtual report
+virtual org
+virtual patch
+
+@r depends on !patch@
+identifier name, size, array;
+// TODO: We can additionally restrict size and array to:
+// identifier size =~ ".*(num|len|count|size|ncpus).*";
+// identifier array !~ ".*(pad|reserved).*";
+// Do we need it?
+type TS, TA;
+position p;
+@@
+
+(
+ // This will also match: typedef struct name { ...
+ // However nested structs are not matched, i.e.:
+ // struct name1 { struct name2 { int s; int a[0]; } st; int i; }
+ // will not be matched. Do we need to handle it?
+ struct name {
+ ... // TODO: Maybe simple ... is enough? It will match structs with a
+ TS size; // single field, e.g.
+ ... // https://elixir.bootlin.com/linux/v5.8/source/arch/arm/include/uapi/asm/setup.h#L127
+(
+* TA array@p[0];
+|
+ // TODO: It seems that there are exception cases for array[1], e.g.
+ // https://elixir.bootlin.com/linux/v5.8/source/arch/powerpc/boot/rs6000.h#L152
+ // https://elixir.bootlin.com/linux/v5.8/source/include/uapi/linux/cdrom.h#L292
+ // https://elixir.bootlin.com/linux/v5.8/source/drivers/net/wireless/ath/ath6kl/usb.c#L108
+ // We could either drop array[1] checking from this rule or
+ // restrict array name with regexp and add, for example, an "allowlist"
+ // with struct names where we allow this code pattern.
+ // TODO: How to handle: u8 data[1][MAXLEN_PSTR6]; ?
+* TA array@p[1];
+)
+ };
+|
+ struct {
+ ...
+ TS size;
+ ...
+(
+* TA array@p[0];
+|
+* TA array@p[1];
+)
+ };
+|
+ // TODO: do we need to handle unions?
+ union name {
+ ...
+ TS size;
+ ...
+(
+* TA array@p[0];
+|
+* TA array@p[1];
+)
+ };
+|
+ union {
+ ...
+ TS size;
+ ...
+(
+* TA array@p[0];
+|
+* TA array@p[1];
+)
+ };
+)
+
+// FIXME: Patch mode doesn't work as expected.
+// Coccinelle handles formatting incorrectly.
+// Patch mode in this rule should be disabled until
+// proper formatting will be supported.
+@depends on patch exists@
+identifier name, size, array;
+type TS, TA;
+@@
+
+(
+ struct name {
+ ...
+ TS size;
+ ...
+(
+- TA array[0];
+|
+- TA array[1];
+)
++ TA array[];
+ };
+|
+ struct {
+ ...
+ TS size;
+ ...
+(
+- TA array[0];
+|
+- TA array[1];
+)
++ TA array[];
+ };
+|
+ union name {
+ ...
+ TS size;
+ ...
+(
+- TA array[0];
+|
+- TA array[1];
+)
++ TA array[];
+ };
+|
+ union {
+ ...
+ TS size;
+ ...
+(
+- TA array[0];
+|
+- TA array[1];
+)
++ TA array[];
+ };
+)
+
+@script: python depends on report@
+p << r.p;
+@@
+
+msg = "WARNING: use flexible-array member instead"
+coccilib.report.print_report(p[0], msg)
+
+@script: python depends on org@
+p << r.p;
+@@
+
+msg = "WARNING: use flexible-array member instead"
+coccilib.org.print_todo(p, msg)
--
2.26.2
Hi Denis,
Thanks a lot for working on this. Please, see some comments below...
On 8/6/20 17:03, Denis Efremov wrote:
> Commit 68e4cd17e218 ("docs: deprecated.rst: Add zero-length and one-element
> arrays") marks one-element and zero-length arrays as deprecated. Kernel
> code should always use "flexible array members" instead.
>
> The script warns about one-element and zero-length arrays in structs.
>
> Cc: Kees Cook <[email protected]>
> Cc: Gustavo A. R. Silva <[email protected]>
> Signed-off-by: Denis Efremov <[email protected]>
> ---
>
> Currently, it's just a draft. I've placed a number of questions in the
> script and marked them as TODO. Kees, Gustavo, if you could help me with
> my questions I think that this rule will be enough to close:
> https://github.com/KSPP/linux/issues/76
>
> BTW, I it's possible to not warn about files in uapi folder if
> this is relevant. Do I need to do it in the script?
>
I think the script should warn about new additions of zero-length/one-element
arrays in UAPI.
> scripts/coccinelle/misc/flexible_array.cocci | 158 +++++++++++++++++++
> 1 file changed, 158 insertions(+)
> create mode 100644 scripts/coccinelle/misc/flexible_array.cocci
>
> diff --git a/scripts/coccinelle/misc/flexible_array.cocci b/scripts/coccinelle/misc/flexible_array.cocci
> new file mode 100644
> index 000000000000..1e7165c79e60
> --- /dev/null
> +++ b/scripts/coccinelle/misc/flexible_array.cocci
> @@ -0,0 +1,158 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +///
> +/// Zero-length and one-element arrays are deprecated, see
> +/// Documentation/process/deprecated.rst
> +/// Flexible-array members should be used instead.
> +///
> +//
> +// Confidence: High
> +// Copyright: (C) 2020 Denis Efremov ISPRAS.
> +// Comments:
> +// Options: --no-includes --include-headers
> +
> +virtual context
> +virtual report
> +virtual org
> +virtual patch
> +
> +@r depends on !patch@
> +identifier name, size, array;
> +// TODO: We can additionally restrict size and array to:
> +// identifier size =~ ".*(num|len|count|size|ncpus).*";
> +// identifier array !~ ".*(pad|reserved).*";
> +// Do we need it?
> +type TS, TA;
> +position p;
> +@@
> +
> +(
> + // This will also match: typedef struct name { ...
> + // However nested structs are not matched, i.e.:
> + // struct name1 { struct name2 { int s; int a[0]; } st; int i; }
> + // will not be matched. Do we need to handle it?
It's fine. I think this would be a different script. One that
exclusively look for all three: zero-length, one-element arrays
and flexible array members in nested structures because
"A structure containing a flexible array member, or a union
containing such a structure (possibly recursively), may not be
a member of a structure or an element of an array. (However
these uses are permitted by GCC as extensions.)"[1]
> + struct name {
> + ... // TODO: Maybe simple ... is enough? It will match structs with a
Yep; simple is always better at first. :)
> + TS size; // single field, e.g.
> + ... // https://elixir.bootlin.com/linux/v5.8/source/arch/arm/include/uapi/asm/setup.h#L127
> +(
> +* TA array@p[0];
> +|
> + // TODO: It seems that there are exception cases for array[1], e.g.
> + // https://elixir.bootlin.com/linux/v5.8/source/arch/powerpc/boot/rs6000.h#L152
> + // https://elixir.bootlin.com/linux/v5.8/source/include/uapi/linux/cdrom.h#L292
> + // https://elixir.bootlin.com/linux/v5.8/source/drivers/net/wireless/ath/ath6kl/usb.c#L108
> + // We could either drop array[1] checking from this rule or
> + // restrict array name with regexp and add, for example, an "allowlist"
> + // with struct names where we allow this code pattern.
> + // TODO: How to handle: u8 data[1][MAXLEN_PSTR6]; ?
> +* TA array@p[1];
> +)
> + };
> +|
> + struct {
> + ...
> + TS size;
> + ...
> +(
> +* TA array@p[0];
> +|
> +* TA array@p[1];
> +)
> + };
> +|
> + // TODO: do we need to handle unions?
Yep; we should warn about this in unions, too.
However, I think unions cannot have members with
incomplete type, so we should not suggest the use
of flexible-array members in unions, because
flexible arrays have incomplete type.
> + union name {
> + ...
> + TS size;
> + ...
> +(
> +* TA array@p[0];
> +|
> +* TA array@p[1];
> +)
> + };
> +|
> + union {
> + ...
> + TS size;
> + ...
> +(
> +* TA array@p[0];
> +|
> +* TA array@p[1];
> +)
> + };
> +)
> +
> +// FIXME: Patch mode doesn't work as expected.
> +// Coccinelle handles formatting incorrectly.
> +// Patch mode in this rule should be disabled until
> +// proper formatting will be supported.
> +@depends on patch exists@
> +identifier name, size, array;
> +type TS, TA;
> +@@
> +
> +(
> + struct name {
> + ...
> + TS size;
> + ...
> +(
> +- TA array[0];
> +|
> +- TA array[1];
> +)
> ++ TA array[];
> + };
> +|
> + struct {
> + ...
> + TS size;
> + ...
> +(
> +- TA array[0];
> +|
> +- TA array[1];
> +)
> ++ TA array[];
> + };
> +|
> + union name {
> + ...
> + TS size;
> + ...
> +(
> +- TA array[0];
> +|
> +- TA array[1];
> +)
> ++ TA array[];
> + };
> +|
> + union {
> + ...
> + TS size;
> + ...
> +(
> +- TA array[0];
> +|
> +- TA array[1];
> +)
> ++ TA array[];
This is not allowed, neither is GCC[2] nor in Clang[3].
> + };
> +)
> +
> +@script: python depends on report@
> +p << r.p;
> +@@
> +
> +msg = "WARNING: use flexible-array member instead"
> +coccilib.report.print_report(p[0], msg)
> +
> +@script: python depends on org@
> +p << r.p;
> +@@
> +
> +msg = "WARNING: use flexible-array member instead"
> +coccilib.org.print_todo(p, msg)
>
I wonder if it might be worth it to also point people to
the documentation in deprecated.rst (commit 68e4cd17e218
("docs: deprecated.rst: Add zero-length and one-element arrays")),
once helpdesk generates the official documentation for 5.9-rc1.
Thanks
--
Gustavo
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://godbolt.org/z/Kajd7e
[3] https://godbolt.org/z/dvKMYb
Commit 68e4cd17e218 ("docs: deprecated.rst: Add zero-length and one-element
arrays") marks one-element and zero-length arrays as deprecated. Kernel
code should always use "flexible array members" instead.
The script warns about one-element and zero-length arrays in structs.
Cc: Kees Cook <[email protected]>
Cc: Gustavo A. R. Silva <[email protected]>
Signed-off-by: Denis Efremov <[email protected]>
---
Changes in v2:
- all uapi headers are now filtered-out. Unfortunately, coccinelle
doesn't provide structure names in Location.current_element.
For structures the field is always "something_else". Thus, there is
no easy way to create a list of existing structures in uapi headers
and suppress the warning only for them, but not for the newly added
uapi structures.
- The pattern doesn't require 2+ fields in a structure/union anymore.
Now it also checks single field structures/unions.
- The pattern simplified and now uses disjuction in array elements
(Thanks, Markus)
- Unions are removed from patch mode
- one-element arrays are removed from patch mode. Correct patch may
involve turning the array to a simple field instead of a flexible
array.
On the current master branch, the rule generates:
- context: https://gist.github.com/evdenis/e2b4323491f9eff35376372df07f723c
- patch: https://gist.github.com/evdenis/46081da9d68ecefd07edc3769cebcf32
scripts/coccinelle/misc/flexible_array.cocci | 88 ++++++++++++++++++++
1 file changed, 88 insertions(+)
create mode 100644 scripts/coccinelle/misc/flexible_array.cocci
diff --git a/scripts/coccinelle/misc/flexible_array.cocci b/scripts/coccinelle/misc/flexible_array.cocci
new file mode 100644
index 000000000000..bf6dcda1783e
--- /dev/null
+++ b/scripts/coccinelle/misc/flexible_array.cocci
@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: GPL-2.0-only
+///
+/// Zero-length and one-element arrays are deprecated, see
+/// Documentation/process/deprecated.rst
+/// Flexible-array members should be used instead.
+///
+//
+// Confidence: High
+// Copyright: (C) 2020 Denis Efremov ISPRAS.
+// Comments:
+// Options: --no-includes --include-headers
+
+virtual context
+virtual report
+virtual org
+virtual patch
+
+@initialize:python@
+@@
+def relevant(positions):
+ for p in positions:
+ if "uapi" in p.file:
+ return False
+ return True
+
+@r depends on !patch@
+identifier name, array;
+type T;
+position p : script:python() { relevant(p) };
+@@
+
+(
+ struct name {
+ ...
+* T array@p[\(0\|1\)];
+ };
+|
+ struct {
+ ...
+* T array@p[\(0\|1\)];
+ };
+|
+ union name {
+ ...
+* T array@p[\(0\|1\)];
+ };
+|
+ union {
+ ...
+* T array@p[\(0\|1\)];
+ };
+)
+
+@depends on patch exists@
+identifier name, array;
+type T;
+position p : script:python() { relevant(p) };
+@@
+
+(
+ struct name {
+ ...
+ T array@p[
+- 0
+ ];
+ };
+|
+ struct {
+ ...
+ T array@p[
+- 0
+ ];
+ };
+)
+
+@script: python depends on report@
+p << r.p;
+@@
+
+msg = "WARNING: use flexible-array member instead"
+coccilib.report.print_report(p[0], msg)
+
+@script: python depends on org@
+p << r.p;
+@@
+
+msg = "WARNING: use flexible-array member instead"
+coccilib.org.print_todo(p, msg)
--
2.26.2
On Mon, 10 Aug 2020, Denis Efremov wrote:
> Commit 68e4cd17e218 ("docs: deprecated.rst: Add zero-length and one-element
> arrays") marks one-element and zero-length arrays as deprecated. Kernel
> code should always use "flexible array members" instead.
>
> The script warns about one-element and zero-length arrays in structs.
>
> Cc: Kees Cook <[email protected]>
> Cc: Gustavo A. R. Silva <[email protected]>
> Signed-off-by: Denis Efremov <[email protected]>
> ---
> Changes in v2:
> - all uapi headers are now filtered-out. Unfortunately, coccinelle
> doesn't provide structure names in Location.current_element.
> For structures the field is always "something_else". Thus, there is
> no easy way to create a list of existing structures in uapi headers
> and suppress the warning only for them, but not for the newly added
> uapi structures.
> - The pattern doesn't require 2+ fields in a structure/union anymore.
> Now it also checks single field structures/unions.
> - The pattern simplified and now uses disjuction in array elements
> (Thanks, Markus)
> - Unions are removed from patch mode
> - one-element arrays are removed from patch mode. Correct patch may
> involve turning the array to a simple field instead of a flexible
> array.
>
> On the current master branch, the rule generates:
> - context: https://gist.github.com/evdenis/e2b4323491f9eff35376372df07f723c
> - patch: https://gist.github.com/evdenis/46081da9d68ecefd07edc3769cebcf32
>
> scripts/coccinelle/misc/flexible_array.cocci | 88 ++++++++++++++++++++
> 1 file changed, 88 insertions(+)
> create mode 100644 scripts/coccinelle/misc/flexible_array.cocci
>
> diff --git a/scripts/coccinelle/misc/flexible_array.cocci b/scripts/coccinelle/misc/flexible_array.cocci
> new file mode 100644
> index 000000000000..bf6dcda1783e
> --- /dev/null
> +++ b/scripts/coccinelle/misc/flexible_array.cocci
> @@ -0,0 +1,88 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +///
> +/// Zero-length and one-element arrays are deprecated, see
> +/// Documentation/process/deprecated.rst
> +/// Flexible-array members should be used instead.
> +///
> +//
> +// Confidence: High
> +// Copyright: (C) 2020 Denis Efremov ISPRAS.
> +// Comments:
> +// Options: --no-includes --include-headers
> +
> +virtual context
> +virtual report
> +virtual org
> +virtual patch
> +
> +@initialize:python@
> +@@
> +def relevant(positions):
> + for p in positions:
> + if "uapi" in p.file:
> + return False
> + return True
> +
> +@r depends on !patch@
> +identifier name, array;
> +type T;
> +position p : script:python() { relevant(p) };
> +@@
> +
> +(
> + struct name {
> + ...
> +* T array@p[\(0\|1\)];
> + };
> +|
> + struct {
> + ...
> +* T array@p[\(0\|1\)];
> + };
> +|
> + union name {
> + ...
> +* T array@p[\(0\|1\)];
> + };
> +|
> + union {
> + ...
> +* T array@p[\(0\|1\)];
> + };
> +)
> +
> +@depends on patch exists@
exists is not necessary here. There are not multiple control-flow paths
through a structure declaration.
> +identifier name, array;
> +type T;
> +position p : script:python() { relevant(p) };
> +@@
> +
> +(
> + struct name {
> + ...
> + T array@p[
> +- 0
> + ];
> + };
> +|
> + struct {
> + ...
> + T array@p[
> +- 0
> + ];
> + };
> +)
> +
> +@script: python depends on report@
> +p << r.p;
> +@@
> +
> +msg = "WARNING: use flexible-array member instead"
> +coccilib.report.print_report(p[0], msg)
> +
> +@script: python depends on org@
> +p << r.p;
> +@@
> +
> +msg = "WARNING: use flexible-array member instead"
> +coccilib.org.print_todo(p, msg)
This should be coccilib.org.print_todo(p[0], msg)
julia
Hi,
On 9/12/20 5:43 PM, Julia Lawall wrote:
>
>
> On Mon, 10 Aug 2020, Denis Efremov wrote:
>
>> Commit 68e4cd17e218 ("docs: deprecated.rst: Add zero-length and one-element
>> arrays") marks one-element and zero-length arrays as deprecated. Kernel
>> code should always use "flexible array members" instead.
>>
>> The script warns about one-element and zero-length arrays in structs.
>>
>> Cc: Kees Cook <[email protected]>
>> Cc: Gustavo A. R. Silva <[email protected]>
>> Signed-off-by: Denis Efremov <[email protected]>
>> ---
>> Changes in v2:
>> - all uapi headers are now filtered-out. Unfortunately, coccinelle
>> doesn't provide structure names in Location.current_element.
>> For structures the field is always "something_else". Thus, there is
>> no easy way to create a list of existing structures in uapi headers
>> and suppress the warning only for them, but not for the newly added
>> uapi structures.
>> - The pattern doesn't require 2+ fields in a structure/union anymore.
>> Now it also checks single field structures/unions.
>> - The pattern simplified and now uses disjuction in array elements
>> (Thanks, Markus)
>> - Unions are removed from patch mode
>> - one-element arrays are removed from patch mode. Correct patch may
>> involve turning the array to a simple field instead of a flexible
>> array.
>>
>> On the current master branch, the rule generates:
>> - context: https://gist.github.com/evdenis/e2b4323491f9eff35376372df07f723c
>> - patch: https://gist.github.com/evdenis/46081da9d68ecefd07edc3769cebcf32
>>
>> scripts/coccinelle/misc/flexible_array.cocci | 88 ++++++++++++++++++++
>> 1 file changed, 88 insertions(+)
>> create mode 100644 scripts/coccinelle/misc/flexible_array.cocci
>>
>> diff --git a/scripts/coccinelle/misc/flexible_array.cocci b/scripts/coccinelle/misc/flexible_array.cocci
>> new file mode 100644
>> index 000000000000..bf6dcda1783e
>> --- /dev/null
>> +++ b/scripts/coccinelle/misc/flexible_array.cocci
>> @@ -0,0 +1,88 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +///
>> +/// Zero-length and one-element arrays are deprecated, see
>> +/// Documentation/process/deprecated.rst
>> +/// Flexible-array members should be used instead.
>> +///
>> +//
>> +// Confidence: High
>> +// Copyright: (C) 2020 Denis Efremov ISPRAS.
>> +// Comments:
>> +// Options: --no-includes --include-headers
>> +
>> +virtual context
>> +virtual report
>> +virtual org
>> +virtual patch
>> +
>> +@initialize:python@
>> +@@
>> +def relevant(positions):
>> + for p in positions:
>> + if "uapi" in p.file:
>> + return False
>> + return True
>> +
>> +@r depends on !patch@
>> +identifier name, array;
>> +type T;
>> +position p : script:python() { relevant(p) };
>> +@@
>> +
>> +(
>> + struct name {
>> + ...
>> +* T array@p[\(0\|1\)];
>> + };
>> +|
>> + struct {
>> + ...
>> +* T array@p[\(0\|1\)];
>> + };
>> +|
>> + union name {
>> + ...
>> +* T array@p[\(0\|1\)];
>> + };
>> +|
>> + union {
>> + ...
>> +* T array@p[\(0\|1\)];
>> + };
>> +)
>> +
>> +@depends on patch exists@
>
> exists is not necessary here. There are not multiple control-flow paths
> through a structure declaration.
>
>> +identifier name, array;
>> +type T;
>> +position p : script:python() { relevant(p) };
>> +@@
>> +
>> +(
>> + struct name {
>> + ...
>> + T array@p[
>> +- 0
>> + ];
>> + };
>> +|
>> + struct {
>> + ...
>> + T array@p[
>> +- 0
>> + ];
>> + };
>> +)
>> +
>> +@script: python depends on report@
>> +p << r.p;
>> +@@
>> +
>> +msg = "WARNING: use flexible-array member instead"
>> +coccilib.report.print_report(p[0], msg)
>> +
>> +@script: python depends on org@
>> +p << r.p;
>> +@@
>> +
>> +msg = "WARNING: use flexible-array member instead"
>> +coccilib.org.print_todo(p, msg)
>
> This should be coccilib.org.print_todo(p[0], msg)
>
Thanks, I will send v3 with fixes and proper links to online documentation.
Regards,
Denis
One-element and zero-length arrays are deprecated [1]. Kernel
code should always use "flexible array members" instead, except
for existing uapi definitions.
The script warns about one-element and zero-length arrays in structs.
[1] commit 68e4cd17e218 ("docs: deprecated.rst: Add zero-length and
one-element arrays")
Cc: Kees Cook <[email protected]>
Cc: Gustavo A. R. Silva <[email protected]>
Signed-off-by: Denis Efremov <[email protected]>
---
Changes in v2:
- all uapi headers are now filtered-out. Unfortunately, coccinelle
doesn't provide structure names in Location.current_element.
For structures the field is always "something_else". Thus, there is
no easy way to create a list of existing structures in uapi headers
and suppress the warning only for them, but not for the newly added
uapi structures.
- The pattern doesn't require 2+ fields in a structure/union anymore.
Now it also checks single field structures/unions.
- The pattern simplified and now uses disjuction in array elements
(Thanks, Markus)
- Unions are removed from patch mode
- one-element arrays are removed from patch mode. Correct patch may
involve turning the array to a simple field instead of a flexible
array.
Changes in v3:
- exists removed from "depends on patch"
- position argument fixed in org mode
- link to the online documentation added to the warning message
scripts/coccinelle/misc/flexible_array.cocci | 88 ++++++++++++++++++++
1 file changed, 88 insertions(+)
create mode 100644 scripts/coccinelle/misc/flexible_array.cocci
diff --git a/scripts/coccinelle/misc/flexible_array.cocci b/scripts/coccinelle/misc/flexible_array.cocci
new file mode 100644
index 000000000000..947fbaff82a9
--- /dev/null
+++ b/scripts/coccinelle/misc/flexible_array.cocci
@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: GPL-2.0-only
+///
+/// Zero-length and one-element arrays are deprecated, see
+/// Documentation/process/deprecated.rst
+/// Flexible-array members should be used instead.
+///
+//
+// Confidence: High
+// Copyright: (C) 2020 Denis Efremov ISPRAS.
+// Comments:
+// Options: --no-includes --include-headers
+
+virtual context
+virtual report
+virtual org
+virtual patch
+
+@initialize:python@
+@@
+def relevant(positions):
+ for p in positions:
+ if "uapi" in p.file:
+ return False
+ return True
+
+@r depends on !patch@
+identifier name, array;
+type T;
+position p : script:python() { relevant(p) };
+@@
+
+(
+ struct name {
+ ...
+* T array@p[\(0\|1\)];
+ };
+|
+ struct {
+ ...
+* T array@p[\(0\|1\)];
+ };
+|
+ union name {
+ ...
+* T array@p[\(0\|1\)];
+ };
+|
+ union {
+ ...
+* T array@p[\(0\|1\)];
+ };
+)
+
+@depends on patch@
+identifier name, array;
+type T;
+position p : script:python() { relevant(p) };
+@@
+
+(
+ struct name {
+ ...
+ T array@p[
+- 0
+ ];
+ };
+|
+ struct {
+ ...
+ T array@p[
+- 0
+ ];
+ };
+)
+
+@script: python depends on report@
+p << r.p;
+@@
+
+msg = "WARNING use flexible-array member instead (https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays)"
+coccilib.report.print_report(p[0], msg)
+
+@script: python depends on org@
+p << r.p;
+@@
+
+msg = "WARNING use flexible-array member instead (https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays)"
+coccilib.org.print_todo(p[0], msg)
--
2.26.2
On Mon, 21 Sep 2020, Denis Efremov wrote:
> One-element and zero-length arrays are deprecated [1]. Kernel
> code should always use "flexible array members" instead, except
> for existing uapi definitions.
>
> The script warns about one-element and zero-length arrays in structs.
>
> [1] commit 68e4cd17e218 ("docs: deprecated.rst: Add zero-length and
> one-element arrays")
>
> Cc: Kees Cook <[email protected]>
> Cc: Gustavo A. R. Silva <[email protected]>
> Signed-off-by: Denis Efremov <[email protected]>
Applied, thanks.
> ---
> Changes in v2:
> - all uapi headers are now filtered-out. Unfortunately, coccinelle
> doesn't provide structure names in Location.current_element.
> For structures the field is always "something_else". Thus, there is
> no easy way to create a list of existing structures in uapi headers
> and suppress the warning only for them, but not for the newly added
> uapi structures.
> - The pattern doesn't require 2+ fields in a structure/union anymore.
> Now it also checks single field structures/unions.
> - The pattern simplified and now uses disjuction in array elements
> (Thanks, Markus)
> - Unions are removed from patch mode
> - one-element arrays are removed from patch mode. Correct patch may
> involve turning the array to a simple field instead of a flexible
> array.
> Changes in v3:
> - exists removed from "depends on patch"
> - position argument fixed in org mode
> - link to the online documentation added to the warning message
>
> scripts/coccinelle/misc/flexible_array.cocci | 88 ++++++++++++++++++++
> 1 file changed, 88 insertions(+)
> create mode 100644 scripts/coccinelle/misc/flexible_array.cocci
>
> diff --git a/scripts/coccinelle/misc/flexible_array.cocci b/scripts/coccinelle/misc/flexible_array.cocci
> new file mode 100644
> index 000000000000..947fbaff82a9
> --- /dev/null
> +++ b/scripts/coccinelle/misc/flexible_array.cocci
> @@ -0,0 +1,88 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +///
> +/// Zero-length and one-element arrays are deprecated, see
> +/// Documentation/process/deprecated.rst
> +/// Flexible-array members should be used instead.
> +///
> +//
> +// Confidence: High
> +// Copyright: (C) 2020 Denis Efremov ISPRAS.
> +// Comments:
> +// Options: --no-includes --include-headers
> +
> +virtual context
> +virtual report
> +virtual org
> +virtual patch
> +
> +@initialize:python@
> +@@
> +def relevant(positions):
> + for p in positions:
> + if "uapi" in p.file:
> + return False
> + return True
> +
> +@r depends on !patch@
> +identifier name, array;
> +type T;
> +position p : script:python() { relevant(p) };
> +@@
> +
> +(
> + struct name {
> + ...
> +* T array@p[\(0\|1\)];
> + };
> +|
> + struct {
> + ...
> +* T array@p[\(0\|1\)];
> + };
> +|
> + union name {
> + ...
> +* T array@p[\(0\|1\)];
> + };
> +|
> + union {
> + ...
> +* T array@p[\(0\|1\)];
> + };
> +)
> +
> +@depends on patch@
> +identifier name, array;
> +type T;
> +position p : script:python() { relevant(p) };
> +@@
> +
> +(
> + struct name {
> + ...
> + T array@p[
> +- 0
> + ];
> + };
> +|
> + struct {
> + ...
> + T array@p[
> +- 0
> + ];
> + };
> +)
> +
> +@script: python depends on report@
> +p << r.p;
> +@@
> +
> +msg = "WARNING use flexible-array member instead (https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays)"
> +coccilib.report.print_report(p[0], msg)
> +
> +@script: python depends on org@
> +p << r.p;
> +@@
> +
> +msg = "WARNING use flexible-array member instead (https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays)"
> +coccilib.org.print_todo(p[0], msg)
> --
> 2.26.2
>
>