[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [XEN PATCH v3] xen: replace occurrences of SAF-1-safe with asmlinkage attribute



Hi Nicola,

On 23/11/2023 09:25, Nicola Vetrini wrote:
On 2023-11-23 09:57, Jan Beulich wrote:
On 16.11.2023 10:08, Nicola Vetrini wrote:
The comment-based justifications for MISRA C:2012 Rule 8.4 are replaced
by the asmlinkage pseudo-attribute, for the sake of uniformity.

Add missing 'xen/compiler.h' #include-s where needed.

The text in docs/misra/deviations.rst and docs/misra/safe.json
is modified to reflect this change.

Signed-off-by: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
---
This patch should be applied after patch 2 of this series.
The request made by Julien to update the wording is
contained in the present patch.

Along with this request he supplied you with an ack. Did you drop that
for a particular reason, or did you simply forget to record it here?


I forgot and added it in a reply.

--- a/xen/arch/x86/boot/reloc.c
+++ b/xen/arch/x86/boot/reloc.c
@@ -28,6 +28,7 @@ asm (

 #include "defs.h"

+#include <xen/compiler.h>
 #include <xen/kconfig.h>
 #include <xen/multiboot.h>
 #include <xen/multiboot2.h>
@@ -348,9 +349,8 @@ static multiboot_info_t *mbi2_reloc(uint32_t mbi_in, uint32_t video_out)
     return mbi_out;
 }

-/* SAF-1-safe */
-void *__stdcall reloc(uint32_t magic, uint32_t in, uint32_t trampoline,
-                      uint32_t video_info)
+void *asmlinkage __stdcall reloc(uint32_t magic, uint32_t in,
+                                 uint32_t trampoline, uint32_t video_info)
 {

One purpose of asmlinkage is to possibly alter the default C calling convention to some more easy to use in assembly code. At least over a period of time Linux for example used that on ix86. If we decided to do something like this, there
would be a collision with __stdcall. Hence I'm not convinced we can put
asmlinkage here. At which point the complete removal of SAF-1-safe also would
need dropping.


Ok, so we can keep SAF-1 here and below and leave the wording in deviations.rst and safe.sjon as is.

I guess you mean without this patch applied and not including my proposed rewording (i.e. to deprecated SAF-1)?

If so, then we are back to the initial concern I raised. We would have two ways to address the deviation. From a user perspective, it would be unclear which one should be used.

In particular, I would rather favor asmlinkage whenever it is possible and only use SAF-1 when it is not possible to use it (like here).

Another possibility would be to deviate __stdcall like we do for asmlinkage (I will let Jan confirm if this is desirable). With this approach, there is less ambiguity when to use either of them.

Cheers,

--
Julien Grall



 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.