[PATCH v2] docs/misra: add rule 2.1 exceptions

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

From: Stefano Stabellini <stefano.stabellini@xxxxxxx>

During the discussions that led to the acceptance of Rule 2.1, we
decided on a few exceptions that were not properly recorded in
rules.rst. Add them now.

Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxx>
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
---
Note that safe.json and the codebase are not yet updated with an
appropriate tag for BUG, panic and friends.

v2:
- fix typo in commit message
- use "only referenced from assembly"
- use "Deliberate unreachability caused by"
- add "See safe.json"
- add acked-by (although I also added "See safe.json")
---
 docs/misra/rules.rst | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/docs/misra/rules.rst b/docs/misra/rules.rst
index 8f0e4d3f25..4f33ed4ba6 100644
--- a/docs/misra/rules.rst
+++ b/docs/misra/rules.rst
@@ -106,7 +106,18 @@ maintainers if you want to suggest a change.
    * - `Rule 2.1 
<https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_02_01_1.c>`_
      - Required
      - A project shall not contain unreachable code
-     -
+     - The following are allowed:
+         - Invariantly constant conditions, e.g. if(IS_ENABLED(CONFIG_HVM)) { 
S; }
+         - Switch with a controlling value statically determined not to
+           match one or more case statements
+         - Functions that are intended to be referenced only from
+           assembly code (e.g. 'do_trap_fiq')
+         - Deliberate unreachability caused by certain macros/functions,
+           e.g. BUG, assert_failed, panic, etc. See safe.json.
+         - asm-offsets.c, as they are not linked deliberately, because
+           they are used to generate definitions for asm modules
+         - Declarations without initializer are safe, as they are not
+           executed
 
    * - `Rule 2.6 
<https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_02_06.c>`_
      - Advisory
-- 
2.25.1