bmalloc: Constify introspect function pointer table

https://bugs.webkit.org/show_bug.cgi?id=156936

Reviewed by Michael Saboff.

* bmalloc/Zone.cpp:
(bmalloc::Zone::Zone): Declaring this function pointer table const puts
it in the read-only section of the binary, providing a little hardening
against overwriting the function pointers at runtime. (We have to
const_cast when assigning because the API declares a pointer to non-const,
but we happen to know it will never try to write through that pointer.
This is not my favorite API.)


Canonical link: https://commits.webkit.org/175046@main
git-svn-id: https://svn.webkit.org/repository/webkit/trunk@199934 268f45cc-cd09-0410-ab3c-d52691b4dbfc

Source/bmalloc/ChangeLog

@@ -1,3 +1,18 @@
+2016-04-22  Geoffrey Garen  <ggaren@apple.com>
+
+        bmalloc: Constify introspect function pointer table
+        https://bugs.webkit.org/show_bug.cgi?id=156936
+
+        Reviewed by Michael Saboff.
+
+        * bmalloc/Zone.cpp:
+        (bmalloc::Zone::Zone): Declaring this function pointer table const puts
+        it in the read-only section of the binary, providing a little hardening
+        against overwriting the function pointers at runtime. (We have to
+        const_cast when assigning because the API declares a pointer to non-const,
+        but we happen to know it will never try to write through that pointer.
+        This is not my favorite API.)
+
 2016-04-19  Geoffrey Garen  <ggaren@apple.com>
 
         bmalloc: fix up overflow checks

Source/bmalloc/bmalloc/Zone.cpp

@@ -104,7 +104,7 @@ static kern_return_t enumerator(task_t task, void* context, unsigned type_mask,
 // The memory analysis API requires the contents of this struct to be a static
 // constant in the program binary. The leaks process will load this struct
 // out of the program binary (and not out of the running process).
-static malloc_introspection_t zoneIntrospect = {
+static const malloc_introspection_t zoneIntrospect = {
     .enumerator = bmalloc::enumerator,
     .good_size = bmalloc::good_size,
     .check = bmalloc::check,
@@ -119,7 +119,7 @@ Zone::Zone()
 {
     malloc_zone_t::size = &bmalloc::zoneSize;
     malloc_zone_t::zone_name = "WebKit Malloc";
-    malloc_zone_t::introspect = &bmalloc::zoneIntrospect;
+    malloc_zone_t::introspect = const_cast<malloc_introspection_t*>(&bmalloc::zoneIntrospect);
     malloc_zone_t::version = 4;
     malloc_zone_register(this);
 }