malloc: Use memsize instead of CHUNK_AVAILABLE_SIZE

This is a pure refactoring change that does not affect behaviour.

The CHUNK_AVAILABLE_SIZE name was unclear, the memsize name tries to
follow the existing convention of mem denoting the allocation that is
handed out to the user, while chunk is its internally used container.

The user owned memory for a given chunk starts at chunk2mem(p) and
the size is memsize(p).  It is not valid to use on dumped heap chunks.

Moved the definition next to other chunk and mem related macros.

Reviewed-by: DJ Delorie <dj@redhat.com>

2 files changed, 24 insertions, 26 deletions

diff --git a/malloc/hooks.c b/malloc/hooks.c
index 9474e19..b82ff57 100644
--- a/malloc/hooks.c
+++ b/malloc/hooks.c
@@ -102,7 +102,7 @@ malloc_check_get_size (mchunkptr p)
 
   assert (using_malloc_checking == 1);
 
-  for (size = CHUNK_AVAILABLE_SIZE (p) - 1;
+  for (size = CHUNK_HDR_SZ + memsize (p) - 1;
        (c = *SAFE_CHAR_OFFSET (p, size)) != magic;
        size -= c)
     {
@@ -130,7 +130,7 @@ mem2mem_check (void *ptr, size_t req_sz)
 
   p = mem2chunk (ptr);
   magic = magicbyte (p);
-  max_sz = CHUNK_AVAILABLE_SIZE (p) - CHUNK_HDR_SZ;
+  max_sz = memsize (p);
 
   for (i = max_sz - 1; i > req_sz; i -= block_sz)
     {
@@ -175,7 +175,7 @@ mem2chunk_check (void *mem, unsigned char **magic_p)
                                next_chunk (prev_chunk (p)) != p)))
         return NULL;
 
-      for (sz = CHUNK_AVAILABLE_SIZE (p) - 1;
+      for (sz = CHUNK_HDR_SZ + memsize (p) - 1;
 	   (c = *SAFE_CHAR_OFFSET (p, sz)) != magic;
 	   sz -= c)
         {
@@ -200,7 +200,7 @@ mem2chunk_check (void *mem, unsigned char **magic_p)
           ((prev_size (p) + sz) & page_mask) != 0)
         return NULL;
 
-      for (sz = CHUNK_AVAILABLE_SIZE (p) - 1;
+      for (sz = CHUNK_HDR_SZ + memsize (p) - 1;
 	   (c = *SAFE_CHAR_OFFSET (p, sz)) != magic;
 	   sz -= c)
         {
@@ -279,8 +279,7 @@ free_check (void *mem, const void *caller)
   else
     {
       /* Mark the chunk as belonging to the library again.  */
-      (void)tag_region (chunk2rawmem (p), CHUNK_AVAILABLE_SIZE (p)
-                                         - CHUNK_HDR_SZ);
+      (void)tag_region (chunk2rawmem (p), memsize (p));
       _int_free (&main_arena, p, 1);
       __libc_lock_unlock (main_arena.mutex);
     }
diff --git a/malloc/malloc.c b/malloc/malloc.c
index 80e4eb6..a2c550d 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -1331,18 +1331,6 @@ nextchunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    MINSIZE :                                                      \
    ((req) + SIZE_SZ + MALLOC_ALIGN_MASK) & ~MALLOC_ALIGN_MASK)
 
-/* Available size of chunk.  This is the size of the real usable data
-   in the chunk, plus the chunk header.  Note: If memory tagging is
-   enabled the layout changes to accomodate the granule size, this is
-   wasteful for small allocations so not done by default.  The logic
-   does not work if chunk headers are not granule aligned.  */
-_Static_assert (__MTAG_GRANULE_SIZE <= CHUNK_HDR_SZ,
-		"memory tagging is not supported with large granule.");
-#define CHUNK_AVAILABLE_SIZE(p)                                       \
-  (__MTAG_GRANULE_SIZE > SIZE_SZ && __glibc_unlikely (mtag_enabled) ? \
-    chunksize (p) :                                                   \
-    chunksize (p) + (chunk_is_mmapped (p) ? 0 : SIZE_SZ))
-
 /* Check if REQ overflows when padded and aligned and if the resulting value
    is less than PTRDIFF_T.  Returns TRUE and the requested size or MINSIZE in
    case the value is less than MINSIZE on SZ or false if any of the previous
@@ -1465,14 +1453,26 @@ checked_request2size (size_t req, size_t *sz) __nonnull (1)
 #pragma GCC poison mchunk_size
 #pragma GCC poison mchunk_prev_size
 
+/* This is the size of the real usable data in the chunk.  Not valid for
+   dumped heap chunks.  */
+#define memsize(p)                                                    \
+  (__MTAG_GRANULE_SIZE > SIZE_SZ && __glibc_unlikely (mtag_enabled) ? \
+    chunksize (p) - CHUNK_HDR_SZ :                                    \
+    chunksize (p) - CHUNK_HDR_SZ + (chunk_is_mmapped (p) ? 0 : SIZE_SZ))
+
+/* If memory tagging is enabled the layout changes to accomodate the granule
+   size, this is wasteful for small allocations so not done by default.
+   Both the chunk header and user data has to be granule aligned.  */
+_Static_assert (__MTAG_GRANULE_SIZE <= CHUNK_HDR_SZ,
+		"memory tagging is not supported with large granule.");
+
 static __always_inline void *
 tag_new_usable (void *ptr)
 {
   if (__glibc_unlikely (mtag_enabled) && ptr)
     {
       mchunkptr cp = mem2chunk(ptr);
-      ptr = __libc_mtag_tag_region (__libc_mtag_new_tag (ptr),
-				    CHUNK_AVAILABLE_SIZE (cp) - CHUNK_HDR_SZ);
+      ptr = __libc_mtag_tag_region (__libc_mtag_new_tag (ptr), memsize (cp));
     }
   return ptr;
 }
@@ -3316,8 +3316,7 @@ __libc_free (void *mem)
       MAYBE_INIT_TCACHE ();
 
       /* Mark the chunk as belonging to the library again.  */
-      (void)tag_region (chunk2rawmem (p),
-			CHUNK_AVAILABLE_SIZE (p) - CHUNK_HDR_SZ);
+      (void)tag_region (chunk2rawmem (p), memsize (p));
 
       ar_ptr = arena_for_chunk (p);
       _int_free (ar_ptr, p, 0);
@@ -3459,7 +3458,7 @@ __libc_realloc (void *oldmem, size_t bytes)
       newp = __libc_malloc (bytes);
       if (newp != NULL)
         {
-	  size_t sz = CHUNK_AVAILABLE_SIZE (oldp) - CHUNK_HDR_SZ;
+	  size_t sz = memsize (oldp);
 	  memcpy (newp, oldmem, sz);
 	  (void) tag_region (chunk2rawmem (oldp), sz);
           _int_free (ar_ptr, oldp, 0);
@@ -3675,7 +3674,7 @@ __libc_calloc (size_t n, size_t elem_size)
      regardless of MORECORE_CLEARS, so we zero the whole block while
      doing so.  */
   if (__glibc_unlikely (mtag_enabled))
-    return tag_new_zero_region (mem, CHUNK_AVAILABLE_SIZE (p) - CHUNK_HDR_SZ);
+    return tag_new_zero_region (mem, memsize (p));
 
   INTERNAL_SIZE_T csz = chunksize (p);
 
@@ -4863,7 +4862,7 @@ _int_realloc(mstate av, mchunkptr oldp, INTERNAL_SIZE_T oldsize,
           else
             {
 	      void *oldmem = chunk2rawmem (oldp);
-	      size_t sz = CHUNK_AVAILABLE_SIZE (oldp) - CHUNK_HDR_SZ;
+	      size_t sz = memsize (oldp);
 	      (void) tag_region (oldmem, sz);
 	      newmem = tag_new_usable (newmem);
 	      memcpy (newmem, oldmem, sz);
@@ -5110,7 +5109,7 @@ musable (void *mem)
 	    result = chunksize (p) - CHUNK_HDR_SZ;
 	}
       else if (inuse (p))
-	result = CHUNK_AVAILABLE_SIZE (p) - CHUNK_HDR_SZ;
+	result = memsize (p);
 
       return result;
     }