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Standards: Adds MISRA-C standard alignment docs
Docs introduces a table of known mandatory MISRA-C rules violation and cautions. The docs explain: - MISRA checks performed for TF-M in CI - Current state of MISRA-C code standard alignment in TF-M - Known mandatory MISRA rules violation and caution Signed-off-by: Mudit Sharma <[email protected]> Change-Id: Ie2b5a81ca4af4ea029cb3ff817aa2681685377a3 (cherry picked from commit 2b3f119)
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‎docs/contributing/index.rst‎

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Code review <code_review_guide>
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Maintainers and Owners <maintainers>
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issue_tracking
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coding_guide
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Coding guide <coding_guide>
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Documentation <doc_guidelines>
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Design proposal <tfm_design_proposal_guideline>
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MISRA-C <standards/misra>
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‎docs/contributing/standards/misra.rst‎

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################
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MISRA-C Standard
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################
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************
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Introduction
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************
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The project checks for MISRA-C violations and cautions in the code base by running the Eclair
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MISRA-C compliance tool as part of our CI process. The results for the daily job can be found at
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`TF-M Eclair daily CI pipeline`_.
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The project, is not fully MISRA-C compliant. However, it aims to be MISRA-C-friendly by:
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- Avoiding the introduction mandatory MISRA-C violations and cautions.
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- Running regular checks on the code base.
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- Analysing and documenting violations and cautions prompted by the Eclair MISRA-C static
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analyser. This can be useful for downstream consumer looking for MISRA-C compliance.
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While the project's intention is to keep violations and cautions to a minimum, it will not block new
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features, bug fixes, or improvements even if they introduce difficult-to-resolve cautions or
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violations. Currently, the project is not equipped with necessary fast-feedback-loop tooling to
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inform contributors about the MISRA-C violations/cautions they introduce. The project welcomes
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suggestions and contributions to better align with the MISRA-C standard.
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.. Note::
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In this document, `Caution` refers to a `caution report`_ generated by Eclair MISRA-C static
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analyser.
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***************
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Update schedule
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***************
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The analysis table for mandatory rules will be updated with every release. Currently, the table is
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up-to-date for release v2.2.0.
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************************************************************
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Assessment of mandatory MISRA-C rules violation and cautions
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************************************************************
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The following table presents an analysis of the violations and cautions of mandatory MISRA-C:2012
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rules report by Eclair.
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The reported violations cannot be easily resolved with the current code structure and are discussed
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further in the table. The project is not actively prioritizing their resolution; however, as
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mentioned earlier, it welcomes suggestions and contributions from the community.
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The community should proactively address any cautions that can be reasonably resolved. However, if
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resolving a caution does not positively affect code quality and readability, it may be safely
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ignored.
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+------------------------+-------------+------------------------+-------------------------+
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|MISRA-C rule Mandatory |Error Type |Rule definition |Explanation |
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+========================+=============+========================+=========================+
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|Rule 9.1 |Caution |The value of an object |Cautions are due to the |
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| | |with automatic storage |objects not being |
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| | |duration shall not be |explicitly initialised |
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| | |read before it has been |during declaration. In |
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| | |set |some of the cases the |
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| | | |address of the object |
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| | | |is passed to a function |
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| | | |to retrieve required |
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| | | |value which gives the |
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| | | |appearance that the |
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| | | |object is used |
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| | | |uninitialized. |
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+------------------------+-------------+------------------------+-------------------------+
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|Rule 17.4 |Violation |All exit paths from a |All violations are |
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| | |function with non-void |exactly the same case |
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| | |return type shall have |of having a naked |
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| | |an explicit 'return' |function with no C |
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| | |statement with an |return statement. This |
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| | |expression |cannot be resolved due |
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| | | |to the body of the |
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| | | |function being written |
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| | | |in assembly. |
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+------------------------+-------------+------------------------+-------------------------+
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|Rule 21.17 |Caution |Use of the string |Currently seen with |
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| | |handling functions from |`tfm_arch_init_context`. |
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| | |`<string.h>` shall not |It is used to clear the |
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| | |result in accesses |memory (stack) to be |
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| | |beyond the bounds of the|used to store program |
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| | |objects referenced by |context (as part of the |
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| | |their pointer parameters|context |
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| | | |initialisation). |
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| | | |Remember, stack grows |
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| | | |downwards - hence, |
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| | | |pointer is decremented |
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| | | |in the implementation. |
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+------------------------+-------------+------------------------+-------------------------+
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|Rule 21.18 |Caution |The `size_t` argument |Functions in TF-M use |
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| | |passed to any function |`<string.h>` functions |
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| | |in `<string.h>` shall |with buffers/objects |
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| | |have an appropriate |passed in by the |
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| | |value |caller. The functions |
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| | | |suspected by Eclair have |
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| | | |been double checked for |
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| | | |verifying size of |
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| | | |buffer/object before |
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| | | |using them. |
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+------------------------+-------------+------------------------+-------------------------+
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*****************************************************
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List of required MISRA-C rules violation and cautions
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*****************************************************
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The list of required MISRA-C rules violations can be found in \
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`TF-M Eclair daily CI pipeline`_ -> Last Successful Artefacts -> \
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index.html -> Report by issue strictness (Mandatory/Required/Advisory) (violations)
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.. _TF-M Eclair daily CI pipeline: https://ci.trustedfirmware.org/view/TF-M/job/tf-m-eclair-daily/
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.. _caution report: https://eclairit.com:3787/doc/index.html#term-caution-report
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--------------
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*SPDX-License-Identifier: BSD-3-Clause*
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*SPDX-FileCopyrightText: Copyright The TrustedFirmware-M Contributors*

‎docs/index.rst‎

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*Copyright (c) 2017-2022, Arm Limited. All rights reserved.*
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*SPDX-License-Identifier: BSD-3-Clause*
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*SPDX-FileCopyrightText: Copyright The TrustedFirmware-M Contributors*

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