[XEN PATCH v2] xen/compiler: deviate the inline macro for MISRA C Rule 20.4

[Nicola Vetrini <nicola.vetrini@bugseng.com>]

Rule 20.4 states: "A macro shall not be defined with the same name
as a keyword".

Defining this macro with the same name as the inline keyword
allows for additionally checking that out-of-lined static inline
functions end up in the correct section while minimizing churn and
has a positive impact on the overall safety. See [1] for additional
context on the motivation of this deviation.

No functional change.

[1] https://lore.kernel.org/xen-devel/adaa6d55-266d-4df8-8967-9340080d17e4@citrix.com/

Signed-off-by: Nicola Vetrini <nicola.vetrini@bugseng.com>
---
Changes in v2:
- Rephrased SAF comment to be more general and added exact motivation
  for the redefinition of "inline" in deviation.rst.
---
 docs/misra/deviations.rst  | 6 ++++++
 docs/misra/safe.json       | 8 ++++++++
 xen/include/xen/compiler.h | 1 +
 3 files changed, 15 insertions(+)

diff --git a/docs/misra/deviations.rst b/docs/misra/deviations.rst
index 123c78e20a01..f8b40dd1e461 100644
--- a/docs/misra/deviations.rst
+++ b/docs/misra/deviations.rst
@@ -322,6 +322,12 @@ Deviations related to MISRA C:2012 Rules:
          - /\* Fallthrough \*/
          - /\* Fallthrough. \*/
 
+   * - R20.4
+     -  The override of the keyword \"inline\" in xen/compiler.h is present so
+        that section contents checks pass when the compiler chooses not to
+        inline a particular function.
+     - Comment-based deviation.
+
    * - R20.7
      - Code violating Rule 20.7 is safe when macro parameters are used:
        (1) as function arguments;
diff --git a/docs/misra/safe.json b/docs/misra/safe.json
index 952324f85cf9..d361d0e65ceb 100644
--- a/docs/misra/safe.json
+++ b/docs/misra/safe.json
@@ -28,6 +28,14 @@
         },
         {
             "id": "SAF-3-safe",
+            "analyser": {
+                "eclair": "MC3R1.R20.4"
+            },
+            "name": "MC3R1.R20.4: allow the definition of a macro with the same name as a keyword in some special cases",
+            "text": "The definition of a macro with the same name as a keyword can be useful in certain configurations to improve the guarantees that can be provided by Xen. See docs/misra/deviations.rst for a precise rationale for all such cases."
+        },
+        {
+            "id": "SAF-4-safe",
             "analyser": {},
             "name": "Sentinel",
             "text": "Next ID to be used"
diff --git a/xen/include/xen/compiler.h b/xen/include/xen/compiler.h
index 16d554f2a593..fc87a2edad7f 100644
--- a/xen/include/xen/compiler.h
+++ b/xen/include/xen/compiler.h
@@ -82,6 +82,7 @@
  * inline functions not expanded inline get placed in .init.text.
  */
 #include <xen/init.h>
+/* SAF-3-safe MISRA C Rule 20.4: allow section checks to pass when not inlined */
 #define inline inline __init
 #endif
 
-- 
2.34.1