From nobody Mon Feb 9 20:36:47 2026 Delivered-To: importer@patchew.org Received-SPF: pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) client-ip=192.237.175.120; envelope-from=xen-devel-bounces@lists.xenproject.org; helo=lists.xenproject.org; Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Return-Path: Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) by mx.zohomail.com with SMTPS id 1696232135848110.64618299258439; Mon, 2 Oct 2023 00:35:35 -0700 (PDT) Received: from list by lists.xenproject.org with outflank-mailman.611116.950523 (Exim 4.92) (envelope-from ) id 1qnDSR-0001AF-7a; Mon, 02 Oct 2023 07:35:11 +0000 Received: by outflank-mailman (output) from mailman id 611116.950523; Mon, 02 Oct 2023 07:35:11 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1qnDSR-0001A8-3R; Mon, 02 Oct 2023 07:35:11 +0000 Received: by outflank-mailman (input) for mailman id 611116; Mon, 02 Oct 2023 07:35:10 +0000 Received: from se1-gles-flk1-in.inumbo.com ([94.247.172.50] helo=se1-gles-flk1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1qnDSQ-0000vL-89 for xen-devel@lists.xenproject.org; Mon, 02 Oct 2023 07:35:10 +0000 Received: from support.bugseng.com (mail.bugseng.com [162.55.131.47]) by se1-gles-flk1.inumbo.com (Halon) with ESMTPS id 357a505c-60f6-11ee-9b0d-b553b5be7939; Mon, 02 Oct 2023 09:35:07 +0200 (CEST) Received: from nico.bugseng.com (unknown [147.123.100.131]) by support.bugseng.com (Postfix) with ESMTPSA id D73C94EE073D; Mon, 2 Oct 2023 09:35:06 +0200 (CEST) X-Outflank-Mailman: Message body and most headers restored to incoming version X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 357a505c-60f6-11ee-9b0d-b553b5be7939 From: Nicola Vetrini To: xen-devel@lists.xenproject.org Cc: sstabellini@kernel.org, michal.orzel@amd.com, xenia.ragiadakou@amd.com, ayan.kumar.halder@amd.com, consulting@bugseng.com, jbeulich@suse.com, andrew.cooper3@citrix.com, roger.pau@citrix.com, Nicola Vetrini , George Dunlap , Julien Grall , Wei Liu , Henry Wang Subject: [XEN PATCH v3 1/3] docs/misra: add documentation skeleton for MISRA C:2012 Dir 4.1 Date: Mon, 2 Oct 2023 09:34:48 +0200 Message-Id: <14df7c8c667f3852bcc1ffab3a3ce862284a8a0c.1696231870.git.nicola.vetrini@bugseng.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ZM-MESSAGEID: 1696232138465100003 Content-Type: text/plain; charset="utf-8" The aforementioned directive requires the project to supply documentation on the measures taken towards the minimization of run-time failures. The actual content of the documentation still needs feedback from the community. The 'rules.rst' file is updated accordingly to mention the newly added documentation. Signed-off-by: Nicola Vetrini Reviewed-by: Stefano Stabellini --- Changes in v2: - Incorporated suggestions from Stefano. Changes in v3: - Replaced two leftover entries. --- docs/misra/C-runtime-failures.rst | 210 ++++++++++++++++++++++++++++++ docs/misra/rules.rst | 7 + 2 files changed, 217 insertions(+) create mode 100644 docs/misra/C-runtime-failures.rst diff --git a/docs/misra/C-runtime-failures.rst b/docs/misra/C-runtime-failu= res.rst new file mode 100644 index 000000000000..77e04a2562b8 --- /dev/null +++ b/docs/misra/C-runtime-failures.rst @@ -0,0 +1,210 @@ +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D +Measures taken towards the minimization of Run-time failures in Xen +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D + +This document specifies which procedures and techinques are used troughout= the +Xen codebase to prevent or minimize the impact of certain classes of run-t= ime +errors that can occurr in the execution of a C program, due to the very mi= nimal +built-in checks that are present in the language. + +The presence of such documentation is requested by MISRA C:2012 Directive = 4.1, +whose headline states: "Run-time failures shall be minimized". + + +Documentation for MISRA C:2012 Dir 4.1: overflow +________________________________________________ + +Pervasive use of assertions and extensive test suite. + + +Documentation for MISRA C:2012 Dir 4.1: unexpected wrapping +___________________________________________________________ + +The only wrapping that is present in the code concerns +unsigned integers and they are all expected. + + +Documentation for MISRA C:2012 Dir 4.1: invalid shift +_____________________________________________________ + +Pervasive use of assertions and extensive test suite. + + +Documentation for MISRA C:2012 Dir 4.1: division/remainder by zero +__________________________________________________________________ + +The division or remainder operations in the project code ensure that +their second argument is never zero. + + +Documentation for MISRA C:2012 Dir 4.1: unsequenced side effects +________________________________________________________________ + +Code executed in interrupt handlers uses spinlocks or disables interrupts +at the right locations to avoid unsequenced side effects. + + +Documentation for MISRA C:2012 Dir 4.1: read from uninitialized automatic = object +__________________________________________________________________________= ______ + +The amount of dynamically allocated objects is limited at runtime in +static configurations. We make sure to initialize dynamically allocated +objects before reading them, and we utilize static analysis tools to +help check for that. + + +Documentation for MISRA C:2012 Dir 4.1: read from uninitialized allocated = object +__________________________________________________________________________= ______ + +Dynamically allocated storage is used in a controlled manner, to prevent t= he +access to uninitialized allocated storage. + + +Documentation for MISRA C:2012 Dir 4.1: write to string literal or const o= bject +__________________________________________________________________________= _____ + +The toolchain puts every string literal and const object into a read-only +section of memory. The hardware exception raised when a write is attempted +on such a memory section is correctly handled. + + +Documentation for MISRA C:2012 Dir 4.1: non-volatile access to volatile ob= ject +__________________________________________________________________________= ____ + +Volatile access is limited to registers that are always accessed +through macros or inline functions, or by limited code chunks that are onl= y used +to access a register. + + +Documentation for MISRA C:2012 Dir 4.1: access to dead allocated object +_______________________________________________________________________ + +Although dynamically allocated storage is used in the project, in safety +configurations its usage is very limited at runtime (it is "almost" only u= sed +at boot time). Coverity is regularly used to scan the code to detect non-f= reed +allocated objects. + + +Documentation for MISRA C:2012 Dir 4.1: access to dead automatic object +_______________________________________________________________________ + +Pointers to automatic variables are never returned, nor stored in +wider-scoped objects. No function does the same on any pointer +received as a parameter. + + +Documentation for MISRA C:2012 Dir 4.1: access to dead thread object +____________________________________________________________________ + +The program does not use per-thread variables. + + +Documentation for MISRA C:2012 Dir 4.1: access using null pointer +_________________________________________________________________ + +All possibly null pointers are checked before access. + + +Documentation for MISRA C:2012 Dir 4.1: access using invalid pointer +____________________________________________________________________ + +Usage of pointers is limited. Pointers passed as parameters are +always checked for validity. + + +Documentation for MISRA C:2012 Dir 4.1: access using out-of-bounds pointer +__________________________________________________________________________ + +Pointers are never used to access arrays without checking for the array si= ze +first. + + +Documentation for MISRA C:2012 Dir 4.1: access using unaligned pointer +______________________________________________________________________ + +Pointer conversion that may result in unaligned pointers are never used. + + +Documentation for MISRA C:2012 Dir 4.1: mistyped access to object +_________________________________________________________________ + +Pointer conversions that may result in mistyped accesses to objects +are never used. + + +Documentation for MISRA C:2012 Dir 4.1: mistyped access to function +___________________________________________________________________ + +This behaviour can arise, for instance, from: + +- incongruent declarations; +- functions having no prototypes; +- casts on function pointers. + +The project has adopted various compiler flags and MISRA rules to lessen t= he +likelihood of this event. + + +Documentation for MISRA C:2012 Dir 4.1: invalid pointer arithmetic +__________________________________________________________________ + +Pointer arithmetic is never used without checking object boundaries. + + +Documentation for MISRA C:2012 Dir 4.1: invalid pointer comparison +__________________________________________________________________ + +Pointers to different objects are never compared (except for pointers that= are +actually linker symbols, but those cases are deviated with a justification= ). + + +Documentation for MISRA C:2012 Dir 4.1: overlapping copy +________________________________________________________ + +The code never uses memcpy() to copy overlapping objects. The instances of +assignments involving overlapping objects are very limited and motivated. + + +Documentation for MISRA C:2012 Dir 4.1: invalid arguments to function +_____________________________________________________________________ + +Many parameters to functions are checked for validity; there is ongoing wo= rk to +make this true for all parameters. + + +Documentation for MISRA C:2012 Dir 4.1: returned function error +_______________________________________________________________ + +Many functions that may produce an error, do return a suitable status code +that is checked at each call site. There is ongoing work to make this true= for +all such functions. + + +Documentation for MISRA C:2012 Dir 4.1: tainted input +_____________________________________________________ + +All parameters of all functions in the extenal ABI are checked before being +used. + + +Documentation for MISRA C:2012 Dir 4.1: data race +_________________________________________________ + +Data that can be accessed concurrently from multiple threads and code exec= uted +by interrupt handlers is protected using spinlocks and other forms of lock= ing, +as appropriate. + + +Documentation for MISRA C:2012 Dir 4.1: invariant violation +___________________________________________________________ + +The extensive checks in the code ensure that any violation of a compile-ti= me +invariant will be detected prior to release builds, and violation of run-t= ime +invariants is extensively tested. In release builds the number of invarian= ts +is greatly reduced. + + +Documentation for MISRA C:2012 Dir 4.1: communication error +___________________________________________________________ + +This project does not involve any external communication. diff --git a/docs/misra/rules.rst b/docs/misra/rules.rst index a2fe01464eec..3139ca7ae6dd 100644 --- a/docs/misra/rules.rst +++ b/docs/misra/rules.rst @@ -49,6 +49,13 @@ maintainers if you want to suggest a change. - All source files shall compile without any compilation errors - =20 + * - `Dir 4.1 `_ + - Required + - Run-time failures shall be minimized + - The strategies adopted by Xen to prevent certain classes of runtime + failures is documented by + `C-runtime-failures.rst `_ + * - `Dir 4.7 `_ - Required - If a function returns error information then that error --=20 2.34.1