[xen stable-4.18] xen: Swap order of actions in the FREE*() macros

[patchbot@xxxxxxx]

commit bdda600406e5f5c35bcb17b2f9458e2138d7ad46
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Fri Feb 2 00:39:42 2024 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Tue Mar 12 15:55:52 2024 +0000

    xen: Swap order of actions in the FREE*() macros
    
    Wherever possible, it is a good idea to NULL out the visible reference to an
    object prior to freeing it.  The FREE*() macros already collect together 
both
    parts, making it easy to adjust.
    
    This has a marginal code generation improvement, as some of the calls to the
    free() function can be tailcall optimised.
    
    No functional change.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
    (cherry picked from commit c4f427ec879e7c0df6d44d02561e8bee838a293e)
---
 xen/include/xen/mm.h      | 3 ++-
 xen/include/xen/xmalloc.h | 7 ++++---
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/xen/include/xen/mm.h b/xen/include/xen/mm.h
index 8b9618609f..8bc5f4249d 100644
--- a/xen/include/xen/mm.h
+++ b/xen/include/xen/mm.h
@@ -91,8 +91,9 @@ bool scrub_free_pages(void);
 
 /* Free an allocation, and zero the pointer to it. */
 #define FREE_XENHEAP_PAGES(p, o) do { \
-    free_xenheap_pages(p, o);         \
+    void *_ptr_ = (p);                \
     (p) = NULL;                       \
+    free_xenheap_pages(_ptr_, o);     \
 } while ( false )
 #define FREE_XENHEAP_PAGE(p) FREE_XENHEAP_PAGES(p, 0)
 
diff --git a/xen/include/xen/xmalloc.h b/xen/include/xen/xmalloc.h
index 16979a117c..d857298011 100644
--- a/xen/include/xen/xmalloc.h
+++ b/xen/include/xen/xmalloc.h
@@ -66,9 +66,10 @@
 extern void xfree(void *);
 
 /* Free an allocation, and zero the pointer to it. */
-#define XFREE(p) do { \
-    xfree(p);         \
-    (p) = NULL;       \
+#define XFREE(p) do {                       \
+    void *_ptr_ = (p);                      \
+    (p) = NULL;                             \
+    xfree(_ptr_);                           \
 } while ( false )
 
 /* Underlying functions */
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.18