[xen master] x86/shadow: avoid sizeof(this_cpu(...))

[patchbot@xxxxxxx]

commit 6621fa6708b8259c4b72bcb967a73fe1f4fb01ec
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Fri May 22 08:19:00 2026 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri May 22 08:19:00 2026 +0200

    x86/shadow: avoid sizeof(this_cpu(...))
    
    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>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/arch/x86/mm/shadow/multi.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/xen/arch/x86/mm/shadow/multi.c b/xen/arch/x86/mm/shadow/multi.c
index cc5e1c50d2..775cf4c39b 100644
--- 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_emulate_write_val);
 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 */
--
generated by git-patchbot for /home/xen/git/xen.git#master