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Re: [XEN PATCH v3] xen: introduce function type bug_fn_t.



On 17/11/23 11:12, Julien Grall wrote:
Hi Federico,

On 17/11/2023 08:28, Federico Serafini wrote:
Introduce function type bug_fn_t. This improves readability and helps
to validate that the function passed to run_in_exception_handle() has
the expected prototype.
Hmmm... I read the second part as you will validate the type in run_in_exception_handle(). But I can't find such change. How about:

"and could be used to help validating that ..."

No need to send a new revision for that. I can do it on commit.


Use the newly-intoduced type to address a violation of MISRA
C:2012 Rule 8.2.

Suggested-by: Julien Grall <julien@xxxxxxx>
Signed-off-by: Federico Serafini <federico.serafini@xxxxxxxxxxx>

Acked-by: Julien Grall <jgrall@xxxxxxxxxx>

---
  xen/arch/arm/traps.c  | 2 +-
  xen/include/xen/bug.h | 5 +++--
  2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index ce89f16404..8492e2b7bb 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -1236,7 +1236,7 @@ int do_bug_frame(const struct cpu_user_regs *regs, vaddr_t pc)
      if ( id == BUGFRAME_run_fn )
      {
-        void (*fn)(const struct cpu_user_regs *) = (void *)regs->BUG_FN_REG;
+        bug_fn_t *fn = (void *)regs->BUG_FN_REG;
          fn(regs);
          return 0;
diff --git a/xen/include/xen/bug.h b/xen/include/xen/bug.h
index e8a4eea71a..cb5138410e 100644
--- a/xen/include/xen/bug.h
+++ b/xen/include/xen/bug.h
@@ -99,6 +99,9 @@ struct bug_frame {
  #endif
+struct cpu_user_regs;
+typedef void bug_fn_t(const struct cpu_user_regs *regs);
+

If your aim is to validate the type in run_in_exception_handler(), then this is defined too late. You will need to define it before "asm/bug.h" is included so arch-specific implementations of run_in_exception_handler can use it.

Note that for Arm we are using a macro, but others may use a static inline.

Thanks for the information!

--
Federico Serafini, M.Sc.

Software Engineer, BUGSENG (http://bugseng.com)



 


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