enable docker ppp

hc

2023-12-09 95099d4622f8cb224d94e314c7a8e0df60b13f87

 kernel/arch/x86/kernel/cpu/rdrand.c
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@@ -1,23 +1,10 @@
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+// SPDX-License-Identifier: GPL-2.0-only
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 /*
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  * This file is part of the Linux kernel.
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  *
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  * Copyright (c) 2011, Intel Corporation
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  * Authors: Fenghua Yu <fenghua.yu@intel.com>,
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  *          H. Peter Anvin <hpa@linux.intel.com>
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- *
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- * This program is free software; you can redistribute it and/or modify it
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- * under the terms and conditions of the GNU General Public License,
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- * version 2, as published by the Free Software Foundation.
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- *
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- * This program is distributed in the hope it will be useful, but WITHOUT
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- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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- * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
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- * more details.
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- *
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- * You should have received a copy of the GNU General Public License along with
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- * this program; if not, write to the Free Software Foundation, Inc.,
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- * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
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- *
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  */
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9
 
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 #include <asm/processor.h>
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@@ -42,7 +29,8 @@
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 #ifdef CONFIG_ARCH_RANDOM
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 void x86_init_rdrand(struct cpuinfo_x86 *c)
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 {
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-	unsigned long tmp;
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+	unsigned int changed = 0;
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+	unsigned long tmp, prev;
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 	int i;
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 	if (!cpu_has(c, X86_FEATURE_RDRAND))
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@@ -55,5 +43,24 @@
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 			return;
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 		}
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 	}
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+
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+	/*
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+	 * Stupid sanity-check whether RDRAND does *actually* generate
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+	 * some at least random-looking data.
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+	 */
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+	prev = tmp;
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+	for (i = 0; i < SANITY_CHECK_LOOPS; i++) {
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+		if (rdrand_long(&tmp)) {
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+			if (prev != tmp)
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+				changed++;
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+
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+			prev = tmp;
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+		}
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+	}
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+
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+	if (WARN_ON_ONCE(!changed))
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+		pr_emerg(
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+"RDRAND gives funky smelling output, might consider not using it by booting with \"nordrand\"");
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+
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 }
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 #endif