From: Marcelo Schmitt <marcelo.schmitt1@gmail.com> To: corbet@lwn.net, mchehab+huawei@kernel.org, dlatypov@google.com, davidgow@google.com Cc: linux-doc@vger.kernel.org, linux-sparse@vger.kernel.org, cocci@inria.fr, smatch@vger.kernel.org, linux-kernel@vger.kernel.org, skhan@linuxfoundation.org, dan.carpenter@oracle.com, julia.lawall@inria.fr Subject: [PATCH v3 2/2] Documentation: dev-tools: Enhance static analysis section with discussion Date: Wed, 30 Mar 2022 18:49:59 -0300 [thread overview] Message-ID: <62f461a20600b95e694016c4e5348ef2e260fa87.1648674305.git.marcelo.schmitt1@gmail.com> (raw) In-Reply-To: <cover.1648674305.git.marcelo.schmitt1@gmail.com> Enhance the static analysis tools section with a discussion on when to use each of them. This was mainly taken from Dan Carpenter and Julia Lawall's comments on a previous documentation patch for static analysis tools. Lore: https://lore.kernel.org/linux-doc/20220329090911.GX3293@kadam/T/#mb97770c8e938095aadc3ee08f4ac7fe32ae386e6 Signed-off-by: Marcelo Schmitt <marcelo.schmitt1@gmail.com> Acked-by: David Gow <davidgow@google.com> Cc: Dan Carpenter <dan.carpenter@oracle.com> Cc: Julia Lawall <julia.lawall@inria.fr> --- Change log v2 -> v3: - Changed the paragraph about Sparse to make it sound better (hopefully) - Minor adjusts to make the considerations about Coccinelle sound better and be precise Documentation/dev-tools/testing-overview.rst | 32 ++++++++++++++++++++ 1 file changed, 32 insertions(+) diff --git a/Documentation/dev-tools/testing-overview.rst b/Documentation/dev-tools/testing-overview.rst index b5e02dd3fd94..0aaf6ea53608 100644 --- a/Documentation/dev-tools/testing-overview.rst +++ b/Documentation/dev-tools/testing-overview.rst @@ -146,3 +146,35 @@ Documentation/dev-tools/coccinelle.rst documentation page for details. Beware, though, that static analysis tools suffer from **false positives**. Errors and warns need to be evaluated carefully before attempting to fix them. + +When to use Sparse and Smatch +----------------------------- + +Sparse does type checking, such as verifying that annotated variables do not +cause endianness bugs, detecting places that use ``__user`` pointers improperly, +and analyzing the compatibility of symbol initializers. + +Smatch does flow analysis and, if allowed to build the function database, it +also does cross function analysis. Smatch tries to answer questions like where +is this buffer allocated? How big is it? Can this index be controlled by the +user? Is this variable larger than that variable? + +It's generally easier to write checks in Smatch than it is to write checks in +Sparse. Nevertheless, there are some overlaps between Sparse and Smatch checks. + +Strong points of Smatch and Coccinelle +-------------------------------------- + +Coccinelle is probably the easiest for writing checks. It works before the +pre-processor so it's easier to check for bugs in macros using Coccinelle. +Coccinelle also creates patches for you, which no other tool does. + +For example, with Coccinelle you can do a mass conversion from +``kmalloc(x * size, GFP_KERNEL)`` to ``kmalloc_array(x, size, GFP_KERNEL)``, and +that's really useful. If you just created a Smatch warning and try to push the +work of converting on to the maintainers they would be annoyed. You'd have to +argue about each warning if can really overflow or not. + +Coccinelle does no analysis of variable values, which is the strong point of +Smatch. On the other hand, Coccinelle allows you to do simple things in a simple +way. -- 2.35.1
WARNING: multiple messages have this Message-ID (diff)
From: Marcelo Schmitt <marcelo.schmitt1@gmail.com> To: corbet@lwn.net, mchehab+huawei@kernel.org, dlatypov@google.com, davidgow@google.com Cc: linux-doc@vger.kernel.org, linux-sparse@vger.kernel.org, cocci@inria.fr, smatch@vger.kernel.org, linux-kernel@vger.kernel.org, skhan@linuxfoundation.org, dan.carpenter@oracle.com, julia.lawall@inria.fr Subject: [cocci] [PATCH v3 2/2] Documentation: dev-tools: Enhance static analysis section with discussion Date: Wed, 30 Mar 2022 18:49:59 -0300 [thread overview] Message-ID: <62f461a20600b95e694016c4e5348ef2e260fa87.1648674305.git.marcelo.schmitt1@gmail.com> (raw) In-Reply-To: <cover.1648674305.git.marcelo.schmitt1@gmail.com> Enhance the static analysis tools section with a discussion on when to use each of them. This was mainly taken from Dan Carpenter and Julia Lawall's comments on a previous documentation patch for static analysis tools. Lore: https://lore.kernel.org/linux-doc/20220329090911.GX3293@kadam/T/#mb97770c8e938095aadc3ee08f4ac7fe32ae386e6 Signed-off-by: Marcelo Schmitt <marcelo.schmitt1@gmail.com> Acked-by: David Gow <davidgow@google.com> Cc: Dan Carpenter <dan.carpenter@oracle.com> Cc: Julia Lawall <julia.lawall@inria.fr> --- Change log v2 -> v3: - Changed the paragraph about Sparse to make it sound better (hopefully) - Minor adjusts to make the considerations about Coccinelle sound better and be precise Documentation/dev-tools/testing-overview.rst | 32 ++++++++++++++++++++ 1 file changed, 32 insertions(+) diff --git a/Documentation/dev-tools/testing-overview.rst b/Documentation/dev-tools/testing-overview.rst index b5e02dd3fd94..0aaf6ea53608 100644 --- a/Documentation/dev-tools/testing-overview.rst +++ b/Documentation/dev-tools/testing-overview.rst @@ -146,3 +146,35 @@ Documentation/dev-tools/coccinelle.rst documentation page for details. Beware, though, that static analysis tools suffer from **false positives**. Errors and warns need to be evaluated carefully before attempting to fix them. + +When to use Sparse and Smatch +----------------------------- + +Sparse does type checking, such as verifying that annotated variables do not +cause endianness bugs, detecting places that use ``__user`` pointers improperly, +and analyzing the compatibility of symbol initializers. + +Smatch does flow analysis and, if allowed to build the function database, it +also does cross function analysis. Smatch tries to answer questions like where +is this buffer allocated? How big is it? Can this index be controlled by the +user? Is this variable larger than that variable? + +It's generally easier to write checks in Smatch than it is to write checks in +Sparse. Nevertheless, there are some overlaps between Sparse and Smatch checks. + +Strong points of Smatch and Coccinelle +-------------------------------------- + +Coccinelle is probably the easiest for writing checks. It works before the +pre-processor so it's easier to check for bugs in macros using Coccinelle. +Coccinelle also creates patches for you, which no other tool does. + +For example, with Coccinelle you can do a mass conversion from +``kmalloc(x * size, GFP_KERNEL)`` to ``kmalloc_array(x, size, GFP_KERNEL)``, and +that's really useful. If you just created a Smatch warning and try to push the +work of converting on to the maintainers they would be annoyed. You'd have to +argue about each warning if can really overflow or not. + +Coccinelle does no analysis of variable values, which is the strong point of +Smatch. On the other hand, Coccinelle allows you to do simple things in a simple +way. -- 2.35.1
next prev parent reply other threads:[~2022-03-30 21:50 UTC|newest] Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-03-30 21:49 [PATCH v3 0/2] Add a section for static analysis tools Marcelo Schmitt 2022-03-30 21:49 ` [cocci] " Marcelo Schmitt 2022-03-30 21:49 ` [PATCH v3 1/2] Documentation: dev-tools: " Marcelo Schmitt 2022-03-30 21:49 ` [cocci] " Marcelo Schmitt 2022-03-31 4:14 ` Dongliang Mu 2022-03-31 4:14 ` [cocci] " Dongliang Mu 2022-03-31 12:10 ` Marcelo Schmitt 2022-03-31 12:10 ` [cocci] " Marcelo Schmitt 2022-04-05 15:50 ` Jonathan Corbet 2022-04-05 15:50 ` Jonathan Corbet 2022-03-30 21:49 ` Marcelo Schmitt [this message] 2022-03-30 21:49 ` [cocci] [PATCH v3 2/2] Documentation: dev-tools: Enhance static analysis section with discussion Marcelo Schmitt 2022-04-01 0:22 ` David Gow 2022-04-01 0:22 ` [cocci] " David Gow 2022-03-31 2:09 ` [PATCH v3 0/2] Add a section for static analysis tools David Gow 2022-03-31 2:09 ` [cocci] " David Gow
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