change system file

hc

2024-10-09 244b2c5ca8b14627e4a17755e5922221e121c771

 kernel/scripts/gcc-plugins/latent_entropy_plugin.c
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@@ -86,25 +86,31 @@
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 	.help		= "disable\tturn off latent entropy instrumentation\n",
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 };
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-static unsigned HOST_WIDE_INT seed;
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-/*
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- * get_random_seed() (this is a GCC function) generates the seed.
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- * This is a simple random generator without any cryptographic security because
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- * the entropy doesn't come from here.
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- */
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+static unsigned HOST_WIDE_INT deterministic_seed;
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+static unsigned HOST_WIDE_INT rnd_buf[32];
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+static size_t rnd_idx = ARRAY_SIZE(rnd_buf);
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+static int urandom_fd = -1;
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+
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 static unsigned HOST_WIDE_INT get_random_const(void)
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 {
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-	unsigned int i;
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-	unsigned HOST_WIDE_INT ret = 0;
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-
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-	for (i = 0; i < 8 * sizeof(ret); i++) {
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-		ret = (ret << 1) | (seed & 1);
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-		seed >>= 1;
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-		if (ret & 1)
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-			seed ^= 0xD800000000000000ULL;
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+	if (deterministic_seed) {
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+		unsigned HOST_WIDE_INT w = deterministic_seed;
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+		w ^= w << 13;
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+		w ^= w >> 7;
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+		w ^= w << 17;
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+		deterministic_seed = w;
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+		return deterministic_seed;
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 	}
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-	return ret;
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+	if (urandom_fd < 0) {
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+		urandom_fd = open("/dev/urandom", O_RDONLY);
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+		gcc_assert(urandom_fd >= 0);
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+	}
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+	if (rnd_idx >= ARRAY_SIZE(rnd_buf)) {
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+		gcc_assert(read(urandom_fd, rnd_buf, sizeof(rnd_buf)) == sizeof(rnd_buf));
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+		rnd_idx = 0;
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+	}
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+	return rnd_buf[rnd_idx++];
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 }
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 static tree tree_get_random_const(tree type)
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@@ -549,8 +555,6 @@
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 	tree type, id;
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 	int quals;
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-	seed = get_random_seed(false);
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-
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 	if (in_lto_p)
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 		return;
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@@ -585,6 +589,12 @@
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 	const struct plugin_argument * const argv = plugin_info->argv;
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 	int i;
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+	/*
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+	 * Call get_random_seed() with noinit=true, so that this returns
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+	 * 0 in the case where no seed has been passed via -frandom-seed.
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+	 */
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+	deterministic_seed = get_random_seed(true);
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+
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 	static const struct ggc_root_tab gt_ggc_r_gt_latent_entropy[] = {
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 		{
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 			.base = &latent_entropy_decl,