Re: [PATCH] public/io: xs_wire: Allow Xenstore to report EPERM

[Julien Grall]

Hi Jan,

On 27/06/2022 07:57, Jan Beulich wrote:
On 24.06.2022 18:51, Julien Grall wrote:
--- a/xen/include/public/io/xs_wire.h
+++ b/xen/include/public/io/xs_wire.h
@@ -76,6 +76,7 @@ static struct xsd_errors xsd_errors[]
  __attribute__((unused))
  #endif
      = {
+    XSD_ERROR(EPERM),
      XSD_ERROR(EINVAL),
      XSD_ERROR(EACCES),
      XSD_ERROR(EEXIST),

Inserting ahead of EINVAL looks to break xenstored_core.c:send_error(),

:(.

which - legitimately or not - assumes EINVAL to be first.

I am not sure who else is relying on this. So I would consider this to 
be bake in the ABI. I think the minimum is to add a BUILD_BUG_ON() in 
send_error().

I will also move EPERM towards the end (I added first because EPERM is 1).

Cheers,

--
Julien Grall