2 files changed, 48 insertions, 21 deletions

diff --git a/scripts/gcc-plugins/latent_entropy_plugin.c b/scripts/gcc-plugins/latent_entropy_plugin.c
index cbe1d6c4b1a5..c84bef1d2895 100644
--- a/scripts/gcc-plugins/latent_entropy_plugin.c
+++ b/scripts/gcc-plugins/latent_entropy_plugin.c
@@ -86,25 +86,31 @@ static struct plugin_info latent_entropy_plugin_info = {
 	.help		= "disable\tturn off latent entropy instrumentation\n",
 };
 
-static unsigned HOST_WIDE_INT seed;
-/*
- * get_random_seed() (this is a GCC function) generates the seed.
- * This is a simple random generator without any cryptographic security because
- * the entropy doesn't come from here.
- */
+static unsigned HOST_WIDE_INT deterministic_seed;
+static unsigned HOST_WIDE_INT rnd_buf[32];
+static size_t rnd_idx = ARRAY_SIZE(rnd_buf);
+static int urandom_fd = -1;
+
 static unsigned HOST_WIDE_INT get_random_const(void)
 {
-	unsigned int i;
-	unsigned HOST_WIDE_INT ret = 0;
-
-	for (i = 0; i < 8 * sizeof(ret); i++) {
-		ret = (ret << 1) | (seed & 1);
-		seed >>= 1;
-		if (ret & 1)
-			seed ^= 0xD800000000000000ULL;
+	if (deterministic_seed) {
+		unsigned HOST_WIDE_INT w = deterministic_seed;
+		w ^= w << 13;
+		w ^= w >> 7;
+		w ^= w << 17;
+		deterministic_seed = w;
+		return deterministic_seed;
 	}
 
-	return ret;
+	if (urandom_fd < 0) {
+		urandom_fd = open("/dev/urandom", O_RDONLY);
+		gcc_assert(urandom_fd >= 0);
+	}
+	if (rnd_idx >= ARRAY_SIZE(rnd_buf)) {
+		gcc_assert(read(urandom_fd, rnd_buf, sizeof(rnd_buf)) == sizeof(rnd_buf));
+		rnd_idx = 0;
+	}
+	return rnd_buf[rnd_idx++];
 }
 
 static tree tree_get_random_const(tree type)
@@ -549,8 +555,6 @@ static void latent_entropy_start_unit(void *gcc_data __unused,
 	tree type, id;
 	int quals;
 
-	seed = get_random_seed(false);
-
 	if (in_lto_p)
 		return;
 
@@ -585,6 +589,12 @@ __visible int plugin_init(struct plugin_name_args *plugin_info,
 	const struct plugin_argument * const argv = plugin_info->argv;
 	int i;
 
+	/*
+	 * Call get_random_seed() with noinit=true, so that this returns
+	 * 0 in the case where no seed has been passed via -frandom-seed.
+	 */
+	deterministic_seed = get_random_seed(true);
+
 	static const struct ggc_root_tab gt_ggc_r_gt_latent_entropy[] = {
 		{
 			.base = &latent_entropy_decl,
diff --git a/scripts/gcc-plugins/stackleak_plugin.c b/scripts/gcc-plugins/stackleak_plugin.c
index dbd37460c573..f46abb315010 100644
--- a/scripts/gcc-plugins/stackleak_plugin.c
+++ b/scripts/gcc-plugins/stackleak_plugin.c
@@ -262,6 +262,23 @@ static unsigned int stackleak_cleanup_execute(void)
 	return 0;
 }
 
+/*
+ * STRING_CST may or may not be NUL terminated:
+ * https://gcc.gnu.org/onlinedocs/gccint/Constant-expressions.html
+ */
+static inline bool string_equal(tree node, const char *string, int length)
+{
+	if (TREE_STRING_LENGTH(node) < length)
+		return false;
+	if (TREE_STRING_LENGTH(node) > length + 1)
+		return false;
+	if (TREE_STRING_LENGTH(node) == length + 1 &&
+	    TREE_STRING_POINTER(node)[length] != '\0')
+		return false;
+	return !memcmp(TREE_STRING_POINTER(node), string, length);
+}
+#define STRING_EQUAL(node, str)	string_equal(node, str, strlen(str))
+
 static bool stackleak_gate(void)
 {
 	tree section;
@@ -271,13 +288,13 @@ static bool stackleak_gate(void)
 	if (section && TREE_VALUE(section)) {
 		section = TREE_VALUE(TREE_VALUE(section));
 
-		if (!strncmp(TREE_STRING_POINTER(section), ".init.text", 10))
+		if (STRING_EQUAL(section, ".init.text"))
 			return false;
-		if (!strncmp(TREE_STRING_POINTER(section), ".devinit.text", 13))
+		if (STRING_EQUAL(section, ".devinit.text"))
 			return false;
-		if (!strncmp(TREE_STRING_POINTER(section), ".cpuinit.text", 13))
+		if (STRING_EQUAL(section, ".cpuinit.text"))
 			return false;
-		if (!strncmp(TREE_STRING_POINTER(section), ".meminit.text", 13))
+		if (STRING_EQUAL(section, ".meminit.text"))
 			return false;
 	}