1) Improve getrandom and /dev/random's support for those arm64

architecture variants that have RNG instructions.
 
 2) Use batched output form CRNG instead of CPU's RNG instructions for
 better performance.
 
 3) Miscellaneous bug fixes.
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Merge tag 'random_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random

Pull /dev/random updates from Ted Ts'o:

 - Improve getrandom and /dev/random's support for those arm64
   architecture variants that have RNG instructions.

 - Use batched output from CRNG instead of CPU's RNG instructions for
   better performance.

 - Miscellaneous bug fixes.

* tag 'random_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random:
  random: avoid warnings for !CONFIG_NUMA builds
  random: fix data races at timer_rand_state
  random: always use batched entropy for get_random_u{32,64}
  random: Make RANDOM_TRUST_CPU depend on ARCH_RANDOM
  arm64: add credited/trusted RNG support
  random: add arch_get_random_*long_early()
  random: split primary/secondary crng init paths

arch/arm64/include/asm/archrandom.h

@@ -4,6 +4,8 @@
 
 #ifdef CONFIG_ARCH_RANDOM
 
+#include <linux/bug.h>
+#include <linux/kernel.h>
 #include <linux/random.h>
 #include <asm/cpufeature.h>
 
@@ -66,6 +68,18 @@ static inline bool __init __early_cpu_has_rndr(void)
 	return (ftr >> ID_AA64ISAR0_RNDR_SHIFT) & 0xf;
 }
 
+static inline bool __init __must_check
+arch_get_random_seed_long_early(unsigned long *v)
+{
+	WARN_ON(system_state != SYSTEM_BOOTING);
+
+	if (!__early_cpu_has_rndr())
+		return false;
+
+	return __arm64_rndr(v);
+}
+#define arch_get_random_seed_long_early arch_get_random_seed_long_early
+
 #else
 
 static inline bool __arm64_rndr(unsigned long *v) { return false; }

drivers/char/Kconfig

@@ -474,7 +474,7 @@ endmenu
 
 config RANDOM_TRUST_CPU
 	bool "Trust the CPU manufacturer to initialize Linux's CRNG"
-	depends on X86 || S390 || PPC
+	depends on ARCH_RANDOM
 	default n
 	help
 	Assume that CPU manufacturer (e.g., Intel or AMD for RDSEED or

drivers/char/random.c

@@ -781,27 +781,55 @@ static int __init parse_trust_cpu(char *arg)
 }
 early_param("random.trust_cpu", parse_trust_cpu);
 
-static void crng_initialize(struct crng_state *crng)
+static bool crng_init_try_arch(struct crng_state *crng)
 {
 	int		i;
-	int		arch_init = 1;
+	bool		arch_init = true;
 	unsigned long	rv;
 
-	memcpy(&crng->state[0], "expand 32-byte k", 16);
-	if (crng == &primary_crng)
-		_extract_entropy(&input_pool, &crng->state[4],
-				 sizeof(__u32) * 12, 0);
-	else
-		_get_random_bytes(&crng->state[4], sizeof(__u32) * 12);
 	for (i = 4; i < 16; i++) {
 		if (!arch_get_random_seed_long(&rv) &&
 		    !arch_get_random_long(&rv)) {
 			rv = random_get_entropy();
-			arch_init = 0;
+			arch_init = false;
 		}
 		crng->state[i] ^= rv;
 	}
-	if (trust_cpu && arch_init && crng == &primary_crng) {
+
+	return arch_init;
+}
+
+static bool __init crng_init_try_arch_early(struct crng_state *crng)
+{
+	int		i;
+	bool		arch_init = true;
+	unsigned long	rv;
+
+	for (i = 4; i < 16; i++) {
+		if (!arch_get_random_seed_long_early(&rv) &&
+		    !arch_get_random_long_early(&rv)) {
+			rv = random_get_entropy();
+			arch_init = false;
+		}
+		crng->state[i] ^= rv;
+	}
+
+	return arch_init;
+}
+
+static void __maybe_unused crng_initialize_secondary(struct crng_state *crng)
+{
+	memcpy(&crng->state[0], "expand 32-byte k", 16);
+	_get_random_bytes(&crng->state[4], sizeof(__u32) * 12);
+	crng_init_try_arch(crng);
+	crng->init_time = jiffies - CRNG_RESEED_INTERVAL - 1;
+}
+
+static void __init crng_initialize_primary(struct crng_state *crng)
+{
+	memcpy(&crng->state[0], "expand 32-byte k", 16);
+	_extract_entropy(&input_pool, &crng->state[4], sizeof(__u32) * 12, 0);
+	if (crng_init_try_arch_early(crng) && trust_cpu) {
 		invalidate_batched_entropy();
 		numa_crng_init();
 		crng_init = 2;
@@ -822,7 +850,7 @@ static void do_numa_crng_init(struct work_struct *work)
 		crng = kmalloc_node(sizeof(struct crng_state),
 				    GFP_KERNEL | __GFP_NOFAIL, i);
 		spin_lock_init(&crng->lock);
-		crng_initialize(crng);
+		crng_initialize_secondary(crng);
 		pool[i] = crng;
 	}
 	mb();
@@ -1142,14 +1170,14 @@ static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
 	 * We take into account the first, second and third-order deltas
 	 * in order to make our estimate.
 	 */
-	delta = sample.jiffies - state->last_time;
-	state->last_time = sample.jiffies;
+	delta = sample.jiffies - READ_ONCE(state->last_time);
+	WRITE_ONCE(state->last_time, sample.jiffies);
 
-	delta2 = delta - state->last_delta;
-	state->last_delta = delta;
+	delta2 = delta - READ_ONCE(state->last_delta);
+	WRITE_ONCE(state->last_delta, delta);
 
-	delta3 = delta2 - state->last_delta2;
-	state->last_delta2 = delta2;
+	delta3 = delta2 - READ_ONCE(state->last_delta2);
+	WRITE_ONCE(state->last_delta2, delta2);
 
 	if (delta < 0)
 		delta = -delta;
@@ -1771,7 +1799,7 @@ static void __init init_std_data(struct entropy_store *r)
 int __init rand_initialize(void)
 {
 	init_std_data(&input_pool);
-	crng_initialize(&primary_crng);
+	crng_initialize_primary(&primary_crng);
 	crng_global_init_time = jiffies;
 	if (ratelimit_disable) {
 		urandom_warning.interval = 0;
@@ -2149,11 +2177,11 @@ struct batched_entropy {
 
 /*
  * Get a random word for internal kernel use only. The quality of the random
- * number is either as good as RDRAND or as good as /dev/urandom, with the
- * goal of being quite fast and not depleting entropy. In order to ensure
+ * number is good as /dev/urandom, but there is no backtrack protection, with
+ * the goal of being quite fast and not depleting entropy. In order to ensure
  * that the randomness provided by this function is okay, the function
- * wait_for_random_bytes() should be called and return 0 at least once
- * at any point prior.
+ * wait_for_random_bytes() should be called and return 0 at least once at any
+ * point prior.
  */
 static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u64) = {
 	.batch_lock	= __SPIN_LOCK_UNLOCKED(batched_entropy_u64.lock),
@@ -2166,15 +2194,6 @@ u64 get_random_u64(void)
 	struct batched_entropy *batch;
 	static void *previous;
 
-#if BITS_PER_LONG == 64
-	if (arch_get_random_long((unsigned long *)&ret))
-		return ret;
-#else
-	if (arch_get_random_long((unsigned long *)&ret) &&
-	    arch_get_random_long((unsigned long *)&ret + 1))
-	    return ret;
-#endif
-
 	warn_unseeded_randomness(&previous);
 
 	batch = raw_cpu_ptr(&batched_entropy_u64);
@@ -2199,9 +2218,6 @@ u32 get_random_u32(void)
 	struct batched_entropy *batch;
 	static void *previous;
 
-	if (arch_get_random_int(&ret))
-		return ret;
-
 	warn_unseeded_randomness(&previous);
 
 	batch = raw_cpu_ptr(&batched_entropy_u32);

include/linux/random.h

@@ -7,6 +7,8 @@
 #ifndef _LINUX_RANDOM_H
 #define _LINUX_RANDOM_H
 
+#include <linux/bug.h>
+#include <linux/kernel.h>
 #include <linux/list.h>
 #include <linux/once.h>
 
@@ -185,6 +187,26 @@ static inline bool __must_check arch_get_random_seed_int(unsigned int *v)
 }
 #endif
 
+/*
+ * Called from the boot CPU during startup; not valid to call once
+ * secondary CPUs are up and preemption is possible.
+ */
+#ifndef arch_get_random_seed_long_early
+static inline bool __init arch_get_random_seed_long_early(unsigned long *v)
+{
+	WARN_ON(system_state != SYSTEM_BOOTING);
+	return arch_get_random_seed_long(v);
+}
+#endif
+
+#ifndef arch_get_random_long_early
+static inline bool __init arch_get_random_long_early(unsigned long *v)
+{
+	WARN_ON(system_state != SYSTEM_BOOTING);
+	return arch_get_random_long(v);
+}
+#endif
+
 /* Pseudo random number generator from numerical recipes. */
 static inline u32 next_pseudo_random32(u32 seed)
 {