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[PATCH 2/4] x86/shadow: avoid sizeof(this_cpu(...))
- To: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Thu, 21 May 2026 17:15:50 +0200
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Teddy Astie <teddy.astie@xxxxxxxxxx>
- Delivery-date: Thu, 21 May 2026 15:15:54 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
Misra C:2012 rule 13.6 takes issue with RELOC_HIDE() uses inside sizeof(),
as used by this_cpu(). Latch the address of the per-CPU variable into a
local variable, and use that in the two sizeof().
No difference in generated code for 2- and 4-level code. There's a small
improvement for the 3-level case.
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
--- a/xen/arch/x86/mm/shadow/multi.c
+++ b/xen/arch/x86/mm/shadow/multi.c
@@ -2057,22 +2057,24 @@ static DEFINE_PER_CPU(guest_l1e_t, trace
static void cf_check trace_emulate_write_val(
const void *ptr, unsigned long vaddr, const void *src, unsigned int bytes)
{
- if ( bytes > sizeof(this_cpu(trace_emulate_write_val)) )
- bytes = sizeof(this_cpu(trace_emulate_write_val));
+ guest_l1e_t *pval = &this_cpu(trace_emulate_write_val);
+
+ if ( bytes > sizeof(*pval) )
+ bytes = sizeof(*pval);
#if GUEST_PAGING_LEVELS == 3
if ( vaddr == this_cpu(trace_emulate_initial_va) )
- memcpy(&this_cpu(trace_emulate_write_val), src, bytes);
+ memcpy(pval, src, bytes);
else if ( (vaddr & ~(GUEST_PTE_SIZE - 1)) ==
this_cpu(trace_emulate_initial_va) )
{
TRACE_SHADOW_PATH_FLAG(TRCE_SFLAG_EMULATE_FULL_PT);
- memcpy(&this_cpu(trace_emulate_write_val),
+ memcpy(pval,
(typeof(ptr))((unsigned long)ptr & ~(GUEST_PTE_SIZE - 1)),
GUEST_PTE_SIZE);
}
#else
- memcpy(&this_cpu(trace_emulate_write_val), src, bytes);
+ memcpy(pval, src, bytes);
#endif
}
#endif /* CONFIG_TRACEBUFFER */
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