From 957f619382923be72835500f56e75d8bbe553892 Mon Sep 17 00:00:00 2001
From: Sverker Eriksson <sverker@erlang.org>
Date: Tue, 26 May 2015 20:12:08 +0200
Subject: erts: Fix magic binary alignment on 32-bit

Caused bus error on 32-bit sparc from unaligned 64-bit word in
binary_to_term trap context.

Also add _UNALIGNED_ magic macros to avoid double alignment padding
in NIF resources.
---
 erts/emulator/beam/erl_nif.c | 26 +++++++++++++++++---------
 1 file changed, 17 insertions(+), 9 deletions(-)

(limited to 'erts/emulator/beam/erl_nif.c')

diff --git a/erts/emulator/beam/erl_nif.c b/erts/emulator/beam/erl_nif.c
index 426a00304e..f42ccf23c2 100644
--- a/erts/emulator/beam/erl_nif.c
+++ b/erts/emulator/beam/erl_nif.c
@@ -1199,7 +1199,11 @@ typedef struct enif_resource_t
     struct enif_resource_type_t* type;
 #ifdef DEBUG
     erts_refc_t nif_refc;
+# ifdef ARCH_32
+    byte align__[4];
+# endif
 #endif
+
     char data[1];
 }ErlNifResource;
 
@@ -1375,7 +1379,7 @@ static void rollback_opened_resource_types(void)
 
 static void nif_resource_dtor(Binary* bin)
 {
-    ErlNifResource* resource = (ErlNifResource*) ERTS_MAGIC_BIN_DATA(bin);
+    ErlNifResource* resource = (ErlNifResource*) ERTS_MAGIC_BIN_UNALIGNED_DATA(bin);
     ErlNifResourceType* type = resource->type;
     ASSERT(ERTS_MAGIC_BIN_DESTRUCTOR(bin) == &nif_resource_dtor);
 
@@ -1396,8 +1400,10 @@ static void nif_resource_dtor(Binary* bin)
 
 void* enif_alloc_resource(ErlNifResourceType* type, size_t size)
 {
-    Binary* bin = erts_create_magic_binary(SIZEOF_ErlNifResource(size), &nif_resource_dtor);
-    ErlNifResource* resource = ERTS_MAGIC_BIN_DATA(bin);
+    Binary* bin = erts_create_magic_binary_x(SIZEOF_ErlNifResource(size),
+                                             &nif_resource_dtor,
+                                             1); /* unaligned */
+    ErlNifResource* resource = ERTS_MAGIC_BIN_UNALIGNED_DATA(bin);
 
     ASSERT(type->owner && type->next && type->prev); /* not allowed in load/upgrade */
     resource->type = type;
@@ -1412,7 +1418,7 @@ void* enif_alloc_resource(ErlNifResourceType* type, size_t size)
 void enif_release_resource(void* obj)
 {
     ErlNifResource* resource = DATA_TO_RESOURCE(obj);
-    ErtsBinary* bin = ERTS_MAGIC_BIN_FROM_DATA(resource);
+    ErtsBinary* bin = ERTS_MAGIC_BIN_FROM_UNALIGNED_DATA(resource);
 
     ASSERT(ERTS_MAGIC_BIN_DESTRUCTOR(bin) == &nif_resource_dtor);
 #ifdef DEBUG
@@ -1426,7 +1432,7 @@ void enif_release_resource(void* obj)
 void enif_keep_resource(void* obj)
 {
     ErlNifResource* resource = DATA_TO_RESOURCE(obj);
-    ErtsBinary* bin = ERTS_MAGIC_BIN_FROM_DATA(resource);
+    ErtsBinary* bin = ERTS_MAGIC_BIN_FROM_UNALIGNED_DATA(resource);
 
     ASSERT(ERTS_MAGIC_BIN_DESTRUCTOR(bin) == &nif_resource_dtor);
 #ifdef DEBUG
@@ -1438,7 +1444,7 @@ void enif_keep_resource(void* obj)
 ERL_NIF_TERM enif_make_resource(ErlNifEnv* env, void* obj)
 {
     ErlNifResource* resource = DATA_TO_RESOURCE(obj);
-    ErtsBinary* bin = ERTS_MAGIC_BIN_FROM_DATA(resource);
+    ErtsBinary* bin = ERTS_MAGIC_BIN_FROM_UNALIGNED_DATA(resource);
     Eterm* hp = alloc_heap(env,PROC_BIN_SIZE);
     return erts_mk_magic_binary_term(&hp, &MSO(env->proc), &bin->binary);
 }
@@ -1467,7 +1473,7 @@ int enif_get_resource(ErlNifEnv* env, ERL_NIF_TERM term, ErlNifResourceType* typ
 	return 0; / * Or should we allow "resource binaries" as handles? * /
     }*/
     mbin = pb->val;
-    resource = (ErlNifResource*) ERTS_MAGIC_BIN_DATA(mbin);
+    resource = (ErlNifResource*) ERTS_MAGIC_BIN_UNALIGNED_DATA(mbin);
     if (ERTS_MAGIC_BIN_DESTRUCTOR(mbin) != &nif_resource_dtor
 	|| resource->type != type) {	
 	return 0;
@@ -1479,8 +1485,8 @@ int enif_get_resource(ErlNifEnv* env, ERL_NIF_TERM term, ErlNifResourceType* typ
 size_t enif_sizeof_resource(void* obj)
 {
     ErlNifResource* resource = DATA_TO_RESOURCE(obj);
-    Binary* bin = &ERTS_MAGIC_BIN_FROM_DATA(resource)->binary;
-    return ERTS_MAGIC_BIN_DATA_SIZE(bin) - offsetof(ErlNifResource,data);
+    Binary* bin = &ERTS_MAGIC_BIN_FROM_UNALIGNED_DATA(resource)->binary;
+    return ERTS_MAGIC_BIN_UNALIGNED_DATA_SIZE(bin) - offsetof(ErlNifResource,data);
 }
 
 
@@ -2689,6 +2695,8 @@ erts_unload_nif(struct erl_module_nif* lib)
 
 void erl_nif_init()
 {
+    ERTS_CT_ASSERT((offsetof(ErlNifResource,data) % 8) == ERTS_MAGIC_BIN_BYTES_TO_ALIGN);
+
     resource_type_list.next = &resource_type_list;
     resource_type_list.prev = &resource_type_list;
     resource_type_list.dtor = NULL;
-- 
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