Implement malloc_info(3).

Expose jemalloc stats through the malloc_info(3) interface.

Bug: 16874689
Change-Id: I4358ac283002e60ff161107028d1a3fb1e9afb0a
diff --git a/libc/bionic/dlmalloc.c b/libc/bionic/dlmalloc.c
index e89c5d1..fdb1b26 100644
--- a/libc/bionic/dlmalloc.c
+++ b/libc/bionic/dlmalloc.c
@@ -16,6 +16,7 @@
 
 #include "dlmalloc.h"
 
+#include "malloc.h"
 #include "private/bionic_prctl.h"
 #include "private/libc_logging.h"
 
@@ -54,3 +55,25 @@
   prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, map, length, "libc_malloc");
   return map;
 }
+
+// Since dlmalloc isn't the default, we'll leave this unimplemented for now. If
+// we decide we need it later, we can fill it in.
+size_t __mallinfo_narenas() {
+  return 0;
+}
+
+size_t __mallinfo_nbins() {
+  return 0;
+}
+
+struct mallinfo __mallinfo_arena_info(size_t) {
+  struct mallinfo mi;
+  memset(&mi, 0, sizeof(mi));
+  return mi;
+}
+
+struct mallinfo __mallinfo_bin_info(size_t, size_t) {
+  struct mallinfo mi;
+  memset(&mi, 0, sizeof(mi));
+  return mi;
+}