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>

2 files changed, 10 insertions, 11 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2b3bf6767d54..1b10c14de5db 100644
--- a/mm/page_alloc.c
+++ b/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
 
diff --git a/scripts/gcc-plugins/latent_entropy_plugin.c b/scripts/gcc-plugins/latent_entropy_plugin.c
index 9d3d4adf3be8..8160f1c1b56e 100644
--- a/scripts/gcc-plugins/latent_entropy_plugin.c
+++ b/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);