Remove failure for bad mmap address hints.

src/trusted/service_runtime/sys_memory.c

Index: src/trusted/service_runtime/sys_memory.c
diff --git a/src/trusted/service_runtime/sys_memory.c b/src/trusted/service_runtime/sys_memory.c
index 7b0d7033d81a0b7192236b7dc312bb997d656b7a..08f4853a31cd07de7b586043554482f99d0aacd1 100644
--- a/src/trusted/service_runtime/sys_memory.c
+++ b/src/trusted/service_runtime/sys_memory.c
@@ -329,9 +329,15 @@ int32_t NaClSysMmapIntern(struct NaClApp        *nap,
    * granularity.  (Windows.)
    */
   if (!NaClIsAllocPageMultiple(usraddr)) {
-    NaClLog(2, "NaClSysMmap: address not allocation granularity aligned\n");
-    map_result = -NACL_ABI_EINVAL;
-    goto cleanup;
+    if (NACL_ABI_MAP_FIXED & flags) {

[Mark Seaborn, 2015/07/30 15:20:14]

Nit: use "(NACL_ABI_MAP_FIXED & flags) != 0"

NaCl style is not to implicitly convert to boolean.

[Sean Klein, 2015/07/30 16:04:29]

Done.

+      NaClLog(2, "NaClSysMmap: address not allocation granularity aligned\n");
+      map_result = -NACL_ABI_EINVAL;

[Mark Seaborn, 2015/07/30 15:20:14]

Is there a test case covering this code path?

[Sean Klein, 2015/07/30 16:04:29]

There is now (added to mem_test.cc).

+      goto cleanup;
+    } else {
+      /* Ignore the hint, as we do not need it. */

[Mark Seaborn, 2015/07/30 15:20:14]

So we use the hint if it's aligned but ignore it otherwise?

Why not just round the hint down to page size alignment when MAP_FIXED isn't
passed?  What does Linux do?

[Sean Klein, 2015/07/30 16:04:29]

Linux rounds the address to a minimum value, and then forces alignment -- I will
match the alignment behavior here.

+      NaClLog(2, "NaClSysMmap: ignoring misaligned hint address\n");
+      usraddr = 0;
+    }
   }
   /*
    * Offset should be non-negative (nacl_abi_off_t is signed).  This