Fix GET_MEM argument rounding in GC_scratch_alloc and similar

(Prevent abort in GC_unix_mmap_get_mem if the allocation size is not
a multiple of a page size.)

* backgraph.c (new_back_edges, push_in_progress): Use
ROUNDUP_PAGESIZE_IF_MMAP() to adjust GET_MEM() argument (when needed).
* headers.c (GC_scratch_alloc): Likewise.
* misc.c (GC_envfile_init): Likewise.
* include/private/gc_priv.h (ROUNDUP_PAGESIZE_IF_MMAP): New macro.
* include/private/gcconfig.h (MMAP_SUPPORTED): Move definition from
os_dep.c (as needed for ROUNDUP_PAGESIZE_IF_MMAP() definition).
* include/private/gcconfig.h (GET_MEM): Refine comment (regarding its
argument).

1 files changed, 4 insertions, 8 deletions

diff --git a/headers.c b/headers.c
index 69f15751..ea83378e 100644
--- a/headers.c
+++ b/headers.c
@@ -129,25 +129,21 @@ GC_INNER ptr_t GC_scratch_alloc(size_t bytes)
 
         if (bytes_to_get <= bytes) {
           /* Undo the damage, and get memory directly */
-            bytes_to_get = bytes;
-#           ifdef USE_MMAP
-                bytes_to_get = ROUNDUP_PAGESIZE(bytes_to_get);
-#           endif
+            bytes_to_get = ROUNDUP_PAGESIZE_IF_MMAP(bytes);
             result = (ptr_t)GET_MEM(bytes_to_get);
             GC_add_to_our_memory(result, bytes_to_get);
             scratch_free_ptr -= bytes;
             GC_scratch_last_end_ptr = result + bytes;
             return(result);
         }
+
+        bytes_to_get = ROUNDUP_PAGESIZE_IF_MMAP(bytes_to_get); /* for safety */
         result = (ptr_t)GET_MEM(bytes_to_get);
         GC_add_to_our_memory(result, bytes_to_get);
         if (result == 0) {
             WARN("Out of memory - trying to allocate less\n", 0);
             scratch_free_ptr -= bytes;
-            bytes_to_get = bytes;
-#           ifdef USE_MMAP
-                bytes_to_get = ROUNDUP_PAGESIZE(bytes_to_get);
-#           endif
+            bytes_to_get = ROUNDUP_PAGESIZE_IF_MMAP(bytes);
             result = (ptr_t)GET_MEM(bytes_to_get);
             GC_add_to_our_memory(result, bytes_to_get);
             return result;