latent_entropy: Fix wrong gcc code generation with 64 bit variables

The stack frame size could grow too large when the plugin used long long
on 32-bit architectures when the given function had too many basic blocks.

The gcc warning was:

drivers/pci/hotplug/ibmphp_ebda.c: In function 'ibmphp_access_ebda':
drivers/pci/hotplug/ibmphp_ebda.c:409:1: warning: the frame size of 1108 bytes is larger than 1024 bytes [-Wframe-larger-than=]

This switches latent_entropy from u64 to unsigned long.

Thanks to PaX Team and Emese Revfy for the patch.

Signed-off-by: Kees Cook <keescook@chromium.org>

mm/page_alloc.c

@@ -92,7 +92,7 @@ int _node_numa_mem_[MAX_NUMNODES];
 #endif
 
 #ifdef CONFIG_GCC_PLUGIN_LATENT_ENTROPY
-volatile u64 latent_entropy __latent_entropy;
+volatile unsigned long latent_entropy __latent_entropy;
 EXPORT_SYMBOL(latent_entropy);
 #endif
 

scripts/gcc-plugins/latent_entropy_plugin.c

@@ -340,7 +340,7 @@ static enum tree_code get_op(tree *rhs)
 		break;
 	}
 	if (rhs)
-		*rhs = build_int_cstu(unsigned_intDI_type_node, random_const);
+		*rhs = build_int_cstu(long_unsigned_type_node, random_const);
 	return op;
 }
 
@@ -372,7 +372,7 @@ static void __perturb_latent_entropy(gimple_stmt_iterator *gsi,
 	enum tree_code op;
 
 	/* 1. create temporary copy of latent_entropy */
-	temp = create_var(unsigned_intDI_type_node, "tmp_latent_entropy");
+	temp = create_var(long_unsigned_type_node, "temp_latent_entropy");
 
 	/* 2. read... */
 	add_referenced_var(latent_entropy_decl);
@@ -459,13 +459,13 @@ static void init_local_entropy(basic_block bb, tree local_entropy)
 	gsi_insert_before(&gsi, call, GSI_NEW_STMT);
 	update_stmt(call);
 
-	udi_frame_addr = fold_convert(unsigned_intDI_type_node, frame_addr);
+	udi_frame_addr = fold_convert(long_unsigned_type_node, frame_addr);
 	assign = gimple_build_assign(local_entropy, udi_frame_addr);
 	gsi_insert_after(&gsi, assign, GSI_NEW_STMT);
 	update_stmt(assign);
 
 	/* 3. create temporary copy of latent_entropy */
-	tmp = create_var(unsigned_intDI_type_node, "tmp_latent_entropy");
+	tmp = create_var(long_unsigned_type_node, "temp_latent_entropy");
 
 	/* 4. read the global entropy variable into local entropy */
 	add_referenced_var(latent_entropy_decl);
@@ -480,7 +480,7 @@ static void init_local_entropy(basic_block bb, tree local_entropy)
 	update_stmt(assign);
 
 	rand_cst = get_random_const();
-	rand_const = build_int_cstu(unsigned_intDI_type_node, rand_cst);
+	rand_const = build_int_cstu(long_unsigned_type_node, rand_cst);
 	op = get_op(NULL);
 	assign = create_assign(op, local_entropy, local_entropy, rand_const);
 	gsi_insert_after(&gsi, assign, GSI_NEW_STMT);
@@ -529,7 +529,7 @@ static unsigned int latent_entropy_execute(void)
 	}
 
 	/* 1. create the local entropy variable */
-	local_entropy = create_var(unsigned_intDI_type_node, "local_entropy");
+	local_entropy = create_var(long_unsigned_type_node, "local_entropy");
 
 	/* 2. initialize the local entropy variable */
 	init_local_entropy(bb, local_entropy);
@@ -561,10 +561,9 @@ static void latent_entropy_start_unit(void *gcc_data __unused,
 	if (in_lto_p)
 		return;
 
-	/* extern volatile u64 latent_entropy */
-	gcc_assert(TYPE_PRECISION(long_long_unsigned_type_node) == 64);
-	quals = TYPE_QUALS(long_long_unsigned_type_node) | TYPE_QUAL_VOLATILE;
-	type = build_qualified_type(long_long_unsigned_type_node, quals);
+	/* extern volatile unsigned long latent_entropy */
+	quals = TYPE_QUALS(long_unsigned_type_node) | TYPE_QUAL_VOLATILE;
+	type = build_qualified_type(long_unsigned_type_node, quals);
 	id = get_identifier("latent_entropy");
 	latent_entropy_decl = build_decl(UNKNOWN_LOCATION, VAR_DECL, id, type);