xen/xmalloc: XMEM_POOL_POISON improvements

When in use, the spew:

  (XEN) Assertion '!memchr_inv(b->ptr.buffer + MIN_BLOCK_SIZE, POISON_BYTE, (b->size & BLOCK_SIZE_MASK) - MIN_BLOCK_SIZE)' failed at common/xmalloc_tlsf.c:246

is unweidly and likely meaningless to non-Xen developers.  Therefore:

 * Switch to IS_ENABLED().  There's no need for full #ifdef-ary.
 * Pull memchr_inv() out into the if(), and provide an error message which
   clearly states that corruption has been found.
 * XMEM_POOL_POISON can be enabled in release builds.  Use printk()+BUG() so
   it doesn't silently stop working when assertions are compiled out.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>

diff --git a/xen/common/xmalloc_tlsf.c b/xen/common/xmalloc_tlsf.c
index 349b31cb4cc134d75a0c6d56b6ecd4a512c00d3a..5e55fc463e7dbd35ee2a16cb4e85f62e3802efcd 100644 (file)
--- a/xen/common/xmalloc_tlsf.c
+++ b/xen/common/xmalloc_tlsf.c
@@ -249,11 +249,14 @@ static inline void EXTRACT_BLOCK(struct bhdr *b, struct xmem_pool *p, int fl,
     }
     b->ptr.free_ptr = (struct free_ptr) {NULL, NULL};
 
-#ifdef CONFIG_XMEM_POOL_POISON
-    if ( (b->size & BLOCK_SIZE_MASK) > MIN_BLOCK_SIZE )
-        ASSERT(!memchr_inv(b->ptr.buffer + MIN_BLOCK_SIZE, POISON_BYTE,
-                           (b->size & BLOCK_SIZE_MASK) - MIN_BLOCK_SIZE));
-#endif /* CONFIG_XMEM_POOL_POISON */
+    if ( IS_ENABLED(CONFIG_XMEM_POOL_POISON) &&
+         (b->size & BLOCK_SIZE_MASK) > MIN_BLOCK_SIZE &&
+         memchr_inv(b->ptr.buffer + MIN_BLOCK_SIZE, POISON_BYTE,
+                    (b->size & BLOCK_SIZE_MASK) - MIN_BLOCK_SIZE) )
+    {
+        printk(XENLOG_ERR "XMEM Pool corruption found");
+        BUG();
+    }
 }
 
 /**
@@ -261,11 +264,10 @@ static inline void EXTRACT_BLOCK(struct bhdr *b, struct xmem_pool *p, int fl,
  */
 static inline void INSERT_BLOCK(struct bhdr *b, struct xmem_pool *p, int fl, int sl)
 {
-#ifdef CONFIG_XMEM_POOL_POISON
-    if ( (b->size & BLOCK_SIZE_MASK) > MIN_BLOCK_SIZE )
+    if ( IS_ENABLED(CONFIG_XMEM_POOL_POISON) &&
+         (b->size & BLOCK_SIZE_MASK) > MIN_BLOCK_SIZE )
         memset(b->ptr.buffer + MIN_BLOCK_SIZE, POISON_BYTE,
                (b->size & BLOCK_SIZE_MASK) - MIN_BLOCK_SIZE);
-#endif /* CONFIG_XMEM_POOL_POISON */
 
     b->ptr.free_ptr = (struct free_ptr) {NULL, p->matrix[fl][sl]};
     if ( p->matrix[fl][sl] )