Commit 58bea414 authored by Kees Cook's avatar Kees Cook
Browse files

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: default avatarKees Cook <keescook@chromium.org>
parent da7389ac

mm/page_alloc.c

+1 −1
Original line number Diff line number Diff line
@@ -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

+9 −10
Original line number Diff line number Diff line
@@ -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);

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