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Re: [XEN PATCH 2/4] x86/emulate: move a variable declaration to address MISRA C:2012 Rule 5.3
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
- Date: Thu, 27 Jul 2023 17:35:42 +0200
- Cc: sstabellini@xxxxxxxxxx, michal.orzel@xxxxxxx, xenia.ragiadakou@xxxxxxx, ayan.kumar.halder@xxxxxxx, consulting@xxxxxxxxxxx, Paul Durrant <paul@xxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Thu, 27 Jul 2023 15:35:49 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 27/07/23 17:31, Jan Beulich wrote:
On 27.07.2023 17:22, Nicola Vetrini wrote:
On 27/07/23 17:06, Jan Beulich wrote:
On 27.07.2023 12:48, Nicola Vetrini wrote:
--- a/xen/arch/x86/hvm/emulate.c
+++ b/xen/arch/x86/hvm/emulate.c
@@ -2024,15 +2024,15 @@ static int cf_check hvmemul_rep_stos(
switch ( p2mt )
{
- unsigned long bytes;
char *buf;
default:
/* Allocate temporary buffer. */
for ( ; ; )
{
- bytes = *reps * bytes_per_rep;
- buf = xmalloc_bytes(bytes);
+ unsigned long bytes_tmp;
+ bytes_tmp = *reps * bytes_per_rep;
+ buf = xmalloc_bytes(bytes_tmp);
if ( buf || *reps <= 1 )
break;
*reps >>= 1;
This wants dealing with differently - the outer scope variable is unused
(only written to) afaics. Eliminating it will, aiui, address another
violation at the same time. And then the same in hvmemul_rep_movs(), just
that there the variable itself needs to survive. I guess I'll make a
patch ...
Wouldn't this code at line ~2068 be possibly affected by writing to
bytes, if the outer variable is used?
Which outer variable? I'm suggesting to drop that (see the patch that
I've sent already).
Jan
/* Adjust address for reverse store. */
if ( df )
gpa -= bytes - bytes_per_rep;
rc = hvm_copy_to_guest_phys(gpa, buf, bytes, curr);
You're right about the other violation (R2.1)
I see, sorry for the noise.
--
Nicola Vetrini, BSc
Software Engineer, BUGSENG srl (https://bugseng.com)
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