MISRA C Directive 4.10 states that "Precautions shall be taken in order
to prevent the contents of a header file being included more than
once".

Add a SAF tag to the existing comment on top of cpufeatures.h.
Add a header inclusion guard to compile.h.

Update ECLAIR configuration to:
- extend existing deviation to other comments explicitly saying a file
  is intended for multiple inclusion;
- extend existing deviation to other autogenerated files;
- tag the guidelines as clean.

Update deviations.rst accordingly.

Signed-off-by: Federico Serafini <federico.serafini@bugseng.com>
Signed-off-by: Stefano Stabellini <stefano.stabellini@amd.com>
---
Changes in v3:
- fix copy/paste error in process-banner.sed
- fix comment in cpufeatures.h so that ECLAIR picks it up properly
- remove xlat.h deviation thanks to Jan's patch

Now it is fully tested and working as the ECLAIR runner is back online.

Changes in v2:
- merge the two "Generated file, do not edit!" deviations into one
- change cpufeatures.h deviation to SAF
- remove compile.h deviation and change compile.h.in instead
---

diff --git a/automation/eclair_analysis/ECLAIR/deviations.ecl b/automation/eclair_analysis/ECLAIR/deviations.ecl
index 9c67358d46..8ec1b85350 100644
--- a/automation/eclair_analysis/ECLAIR/deviations.ecl
+++ b/automation/eclair_analysis/ECLAIR/deviations.ecl
@@ -72,11 +72,15 @@ they are not instances of commented-out code."
 -config=MC3A2.D4.3,reports+={deliberate, "any_area(any_loc(file(arm64_bitops))&&context(name(int_clear_mask16)))"}
 -doc_end
 
--doc_begin="Files that are intended to be included more than once do not need to
-conform to the directive."
+-doc_begin="Files that are intended to be included more than once (and have
+a comment that says this explicitly) do not need to conform to the directive."
 -config=MC3A2.D4.10,reports+={safe, "first_area(text(^/\\* This file is intended to be included multiple times\\. \\*/$, begin-4))"}
--config=MC3A2.D4.10,reports+={safe, "first_area(text(^/\\* Generated file, do not edit! \\*/$, begin-3))"}
--config=MC3A2.D4.10,reports+={safe, "all_area(all_loc(file(^xen/include/generated/autoconf.h$)))"}
+-config=MC3A2.D4.10,reports+={safe, "first_area(text(^/\\* Generated file, do not edit! \\*/$, begin-3...begin-2))"}
+-doc_end
+
+-doc_begin="Autogenerated files that do not need to conform to the directive."
+-config=MC3A2.D4.10,reports+={safe, "all_area(all_loc(file(^xen/include/generated/autoconf\\.h$)))"}
+-config=MC3A2.D4.10,reports+={safe, "all_area(all_loc(file(^xen/arch/(arm||x86)/include/generated/asm/.*$)))"}
 -doc_end
 
 -doc_begin="Including multiple times a .c file is safe because every function or data item
diff --git a/automation/eclair_analysis/ECLAIR/tagging.ecl b/automation/eclair_analysis/ECLAIR/tagging.ecl
index f9da5d5f4d..b95f07feb0 100644
--- a/automation/eclair_analysis/ECLAIR/tagging.ecl
+++ b/automation/eclair_analysis/ECLAIR/tagging.ecl
@@ -23,6 +23,7 @@
 "MC3A2.D1.1||
 MC3A2.D2.1||
 MC3A2.D4.1||
+MC3A2.D4.10||
 MC3A2.D4.11||
 MC3A2.D4.14||
 MC3A2.R1.1||
diff --git a/docs/misra/deviations.rst b/docs/misra/deviations.rst
index fe0b1e10a2..fd7a18983d 100644
--- a/docs/misra/deviations.rst
+++ b/docs/misra/deviations.rst
@@ -30,6 +30,19 @@ Deviations related to MISRA C:2012 Directives:
        not to add an additional encapsulation layer.
      - Tagged as `deliberate` for ECLAIR.
 
+   * - D4.10
+     - Files that are intended to be included more than once (and have
+       a comment that says this explicitly) do not need to conform to the
+       directive.
+     - Tagged as `safe` for ECLAIR.
+
+   * - D4.10
+     - There are autogenerated files that do not need to comply to the
+       directive.
+     - Tagged as `safe` for ECLAIR. Such files are:
+        - xen/include/generated/autoconf.h
+        - xen/arch/{arm,x86}/include/generated/asm/\*
+
    * - D4.10
      - Including multiple times a .c file is safe because every function or data item
        it defines would in (the common case) be already defined.
diff --git a/xen/arch/x86/include/asm/cpufeatures.h b/xen/arch/x86/include/asm/cpufeatures.h
index 9e3ed21c02..bd1f00f5d2 100644
--- a/xen/arch/x86/include/asm/cpufeatures.h
+++ b/xen/arch/x86/include/asm/cpufeatures.h
@@ -1,6 +1,6 @@
-/*
- * Explicitly intended for multiple inclusion.
- */
+/* This file is intended to be included multiple times. */
+/*#ifndef X86_CPUFEATURES_H */
+/*#define X86_CPUFEATURES_H */
 
 #include <xen/lib/x86/cpuid-autogen.h>
 
@@ -63,3 +63,5 @@ XEN_CPUFEATURE(USE_VMCALL,        X86_SYNTH(30)) /* Use VMCALL instead of VMMCAL
 
 /* Total number of capability words, inc synth and bug words. */
 #define NCAPINTS (FSCAPINTS + X86_NR_SYNTH + X86_NR_BUG) /* N 32-bit words worth of info */
+
+/*#endif X86_CPUFEATURES_H */
diff --git a/xen/include/xen/compile.h.in b/xen/include/xen/compile.h.in
index 3151d1e7d1..9206341ba6 100644
--- a/xen/include/xen/compile.h.in
+++ b/xen/include/xen/compile.h.in
@@ -1,3 +1,6 @@
+#ifndef XEN_COMPILE_H
+#define XEN_COMPILE_H
+
 #define XEN_COMPILE_DATE	"@@date@@"
 #define XEN_COMPILE_TIME	"@@time@@"
 #define XEN_COMPILE_BY		"@@whoami@@"
diff --git a/xen/tools/process-banner.sed b/xen/tools/process-banner.sed
index 56c76558bc..4cf3f9a116 100755
--- a/xen/tools/process-banner.sed
+++ b/xen/tools/process-banner.sed
@@ -12,3 +12,8 @@ s_(.*)_"\1\\n"_
 
 # Trailing \ on all but the final line.
 $!s_$_ \\_
+
+# Append closing header guard
+$a\
+\
+#endif /* XEN_COMPILE_H */

On 04.06.2025 03:11, Stefano Stabellini wrote:
> MISRA C Directive 4.10 states that "Precautions shall be taken in order
> to prevent the contents of a header file being included more than
> once".
> 
> Add a SAF tag to the existing comment on top of cpufeatures.h.
> Add a header inclusion guard to compile.h.
> 
> Update ECLAIR configuration to:
> - extend existing deviation to other comments explicitly saying a file
>   is intended for multiple inclusion;
> - extend existing deviation to other autogenerated files;
> - tag the guidelines as clean.
> 
> Update deviations.rst accordingly.
> 
> Signed-off-by: Federico Serafini <federico.serafini@bugseng.com>
> Signed-off-by: Stefano Stabellini <stefano.stabellini@amd.com>
> ---
> Changes in v3:
> - fix copy/paste error in process-banner.sed
> - fix comment in cpufeatures.h so that ECLAIR picks it up properly
> - remove xlat.h deviation thanks to Jan's patch

With this in mind, ...

> --- a/docs/misra/deviations.rst
> +++ b/docs/misra/deviations.rst
> @@ -30,6 +30,19 @@ Deviations related to MISRA C:2012 Directives:
>         not to add an additional encapsulation layer.
>       - Tagged as `deliberate` for ECLAIR.
>  
> +   * - D4.10
> +     - Files that are intended to be included more than once (and have
> +       a comment that says this explicitly) do not need to conform to the
> +       directive.
> +     - Tagged as `safe` for ECLAIR.
> +
> +   * - D4.10
> +     - There are autogenerated files that do not need to comply to the
> +       directive.
> +     - Tagged as `safe` for ECLAIR. Such files are:
> +        - xen/include/generated/autoconf.h
> +        - xen/arch/{arm,x86}/include/generated/asm/\*

... why not deal with at least the latter (we may not want to fiddle with kconfig
sources) as well?

Jan

On Wed, 4 Jun 2025, Jan Beulich wrote:
> On 04.06.2025 03:11, Stefano Stabellini wrote:
> > MISRA C Directive 4.10 states that "Precautions shall be taken in order
> > to prevent the contents of a header file being included more than
> > once".
> > 
> > Add a SAF tag to the existing comment on top of cpufeatures.h.
> > Add a header inclusion guard to compile.h.
> > 
> > Update ECLAIR configuration to:
> > - extend existing deviation to other comments explicitly saying a file
> >   is intended for multiple inclusion;
> > - extend existing deviation to other autogenerated files;
> > - tag the guidelines as clean.
> > 
> > Update deviations.rst accordingly.
> > 
> > Signed-off-by: Federico Serafini <federico.serafini@bugseng.com>
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@amd.com>
> > ---
> > Changes in v3:
> > - fix copy/paste error in process-banner.sed
> > - fix comment in cpufeatures.h so that ECLAIR picks it up properly
> > - remove xlat.h deviation thanks to Jan's patch
> 
> With this in mind, ...
> 
> > --- a/docs/misra/deviations.rst
> > +++ b/docs/misra/deviations.rst
> > @@ -30,6 +30,19 @@ Deviations related to MISRA C:2012 Directives:
> >         not to add an additional encapsulation layer.
> >       - Tagged as `deliberate` for ECLAIR.
> >  
> > +   * - D4.10
> > +     - Files that are intended to be included more than once (and have
> > +       a comment that says this explicitly) do not need to conform to the
> > +       directive.
> > +     - Tagged as `safe` for ECLAIR.
> > +
> > +   * - D4.10
> > +     - There are autogenerated files that do not need to comply to the
> > +       directive.
> > +     - Tagged as `safe` for ECLAIR. Such files are:
> > +        - xen/include/generated/autoconf.h
> > +        - xen/arch/{arm,x86}/include/generated/asm/\*
> 
> ... why not deal with at least the latter (we may not want to fiddle with kconfig
> sources) as well?

Is this what you had in mind?
https://lore.kernel.org/xen-devel/alpine.DEB.2.22.394.2506041605090.2495561@ubuntu-linux-20-04-desktop/