Merge branch 'x86-rdrand-for-linus' of git://git.kernel.org/pub/scm/l…

…inux/kernel/git/tip/tip * 'x86-rdrand-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86, random: Verify RDRAND functionality and allow it to be disabled x86, random: Architectural inlines to get random integers with RDRAND random: Add support for architectural random hooks Fix up trivial conflicts in drivers/char/random.c: the architectural random hooks touched "get_random_int()" that was simplified to use MD5 and not do the keyptr thing any more (see commit 6e5714e: "net: Compute protocol sequence numbers and fragment IDs using MD5").
torvalds · Oct 28, 2011 · 8e6d539 · 8e6d539
2 parents 8237eb9 + 49d859d
commit 8e6d539
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diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
@@ -1797,6 +1797,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 
 	noresidual	[PPC] Don't use residual data on PReP machines.
 
+	nordrand	[X86] Disable the direct use of the RDRAND
+			instruction even if it is supported by the
+			processor.  RDRAND is still available to user
+			space applications.
+
 	noresume	[SWSUSP] Disables resume and restores original swap
 			space.
 

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
@@ -1454,6 +1454,15 @@ config ARCH_USES_PG_UNCACHED
 	def_bool y
 	depends on X86_PAT
 
+config ARCH_RANDOM
+	def_bool y
+	prompt "x86 architectural random number generator" if EXPERT
+	---help---
+	  Enable the x86 architectural RDRAND instruction
+	  (Intel Bull Mountain technology) to generate random numbers.
+	  If supported, this is a high bandwidth, cryptographically
+	  secure hardware random number generator.
+
 config EFI
 	bool "EFI runtime service support"
 	depends on ACPI

diff --git a/arch/x86/include/asm/archrandom.h b/arch/x86/include/asm/archrandom.h
@@ -0,0 +1,75 @@
+/*
+ * This file is part of the Linux kernel.
+ *
+ * Copyright (c) 2011, Intel Corporation
+ * Authors: Fenghua Yu <fenghua.yu@intel.com>,
+ *          H. Peter Anvin <hpa@linux.intel.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+
+#ifndef ASM_X86_ARCHRANDOM_H
+#define ASM_X86_ARCHRANDOM_H
+
+#include <asm/processor.h>
+#include <asm/cpufeature.h>
+#include <asm/alternative.h>
+#include <asm/nops.h>
+
+#define RDRAND_RETRY_LOOPS	10
+
+#define RDRAND_INT	".byte 0x0f,0xc7,0xf0"
+#ifdef CONFIG_X86_64
+# define RDRAND_LONG	".byte 0x48,0x0f,0xc7,0xf0"
+#else
+# define RDRAND_LONG	RDRAND_INT
+#endif
+
+#ifdef CONFIG_ARCH_RANDOM
+
+#define GET_RANDOM(name, type, rdrand, nop)			\
+static inline int name(type *v)					\
+{								\
+	int ok;							\
+	alternative_io("movl $0, %0\n\t"			\
+		       nop,					\
+		       "\n1: " rdrand "\n\t"			\
+		       "jc 2f\n\t"				\
+		       "decl %0\n\t"                            \
+		       "jnz 1b\n\t"                             \
+		       "2:",                                    \
+		       X86_FEATURE_RDRAND,                      \
+		       ASM_OUTPUT2("=r" (ok), "=a" (*v)),       \
+		       "0" (RDRAND_RETRY_LOOPS));		\
+	return ok;						\
+}
+
+#ifdef CONFIG_X86_64
+
+GET_RANDOM(arch_get_random_long, unsigned long, RDRAND_LONG, ASM_NOP5);
+GET_RANDOM(arch_get_random_int, unsigned int, RDRAND_INT, ASM_NOP4);
+
+#else
+
+GET_RANDOM(arch_get_random_long, unsigned long, RDRAND_LONG, ASM_NOP3);
+GET_RANDOM(arch_get_random_int, unsigned int, RDRAND_INT, ASM_NOP3);
+
+#endif /* CONFIG_X86_64 */
+
+#endif  /* CONFIG_ARCH_RANDOM */
+
+extern void x86_init_rdrand(struct cpuinfo_x86 *c);
+
+#endif /* ASM_X86_ARCHRANDOM_H */
diff --git a/arch/x86/kernel/cpu/Makefile b/arch/x86/kernel/cpu/Makefile
@@ -15,6 +15,7 @@ CFLAGS_common.o		:= $(nostackp)
 obj-y			:= intel_cacheinfo.o scattered.o topology.o
 obj-y			+= proc.o capflags.o powerflags.o common.o
 obj-y			+= vmware.o hypervisor.o sched.o mshyperv.o
+obj-y			+= rdrand.o
 
 obj-$(CONFIG_X86_32)	+= bugs.o
 obj-$(CONFIG_X86_64)	+= bugs_64.o

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
@@ -15,6 +15,7 @@
 #include <asm/stackprotector.h>
 #include <asm/perf_event.h>
 #include <asm/mmu_context.h>
+#include <asm/archrandom.h>
 #include <asm/hypervisor.h>
 #include <asm/processor.h>
 #include <asm/sections.h>
@@ -860,6 +861,7 @@ static void __cpuinit identify_cpu(struct cpuinfo_x86 *c)
 #endif
 
 	init_hypervisor(c);
+	x86_init_rdrand(c);
 
 	/*
 	 * Clear/Set all flags overriden by options, need do it

diff --git a/arch/x86/kernel/cpu/rdrand.c b/arch/x86/kernel/cpu/rdrand.c
@@ -0,0 +1,73 @@
+/*
+ * This file is part of the Linux kernel.
+ *
+ * Copyright (c) 2011, Intel Corporation
+ * Authors: Fenghua Yu <fenghua.yu@intel.com>,
+ *          H. Peter Anvin <hpa@linux.intel.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+
+#include <asm/processor.h>
+#include <asm/archrandom.h>
+#include <asm/sections.h>
+
+static int __init x86_rdrand_setup(char *s)
+{
+	setup_clear_cpu_cap(X86_FEATURE_RDRAND);
+	return 1;
+}
+__setup("nordrand", x86_rdrand_setup);
+
+/* We can't use arch_get_random_long() here since alternatives haven't run */
+static inline int rdrand_long(unsigned long *v)
+{
+	int ok;
+	asm volatile("1: " RDRAND_LONG "\n\t"
+		     "jc 2f\n\t"
+		     "decl %0\n\t"
+		     "jnz 1b\n\t"
+		     "2:"
+		     : "=r" (ok), "=a" (*v)
+		     : "0" (RDRAND_RETRY_LOOPS));
+	return ok;
+}
+
+/*
+ * Force a reseed cycle; we are architecturally guaranteed a reseed
+ * after no more than 512 128-bit chunks of random data.  This also
+ * acts as a test of the CPU capability.
+ */
+#define RESEED_LOOP ((512*128)/sizeof(unsigned long))
+
+void __cpuinit x86_init_rdrand(struct cpuinfo_x86 *c)
+{
+#ifdef CONFIG_ARCH_RANDOM
+	unsigned long tmp;
+	int i, count, ok;
+
+	if (!cpu_has(c, X86_FEATURE_RDRAND))
+		return;		/* Nothing to do */
+
+	for (count = i = 0; i < RESEED_LOOP; i++) {
+		ok = rdrand_long(&tmp);
+		if (ok)
+			count++;
+	}
+
+	if (count != RESEED_LOOP)
+		clear_cpu_cap(c, X86_FEATURE_RDRAND);
+#endif
+}
diff --git a/drivers/char/random.c b/drivers/char/random.c
@@ -932,7 +932,21 @@ static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
  */
 void get_random_bytes(void *buf, int nbytes)
 {
-	extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0);
+	char *p = buf;
+
+	while (nbytes) {
+		unsigned long v;
+		int chunk = min(nbytes, (int)sizeof(unsigned long));
+
+		if (!arch_get_random_long(&v))
+			break;
+
+		memcpy(buf, &v, chunk);
+		p += chunk;
+		nbytes -= chunk;
+	}
+
+	extract_entropy(&nonblocking_pool, p, nbytes, 0, 0);
 }
 EXPORT_SYMBOL(get_random_bytes);
 
@@ -1318,9 +1332,14 @@ late_initcall(random_int_secret_init);
 DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash);
 unsigned int get_random_int(void)
 {
-	__u32 *hash = get_cpu_var(get_random_int_hash);
+	__u32 *hash;
 	unsigned int ret;
 
+	if (arch_get_random_int(&ret))
+		return ret;
+
+	hash = get_cpu_var(get_random_int_hash);
+
 	hash[0] += current->pid + jiffies + get_cycles();
 	md5_transform(hash, random_int_secret);
 	ret = hash[0];

diff --git a/include/linux/random.h b/include/linux/random.h
@@ -91,6 +91,19 @@ static inline void prandom32_seed(struct rnd_state *state, u64 seed)
 	state->s3 = __seed(i, 15);
 }
 
+#ifdef CONFIG_ARCH_RANDOM
+# include <asm/archrandom.h>
+#else
+static inline int arch_get_random_long(unsigned long *v)
+{
+	return 0;
+}
+static inline int arch_get_random_int(unsigned int *v)
+{
+	return 0;
+}
+#endif
+
 #endif /* __KERNEL___ */
 
 #endif /* _LINUX_RANDOM_H */