Merge tag 'random_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random

Pull randomness updates from Ted Ts'o:
 "Cleanups and bug fixes to /dev/random, add a new getrandom(2) system
  call, which is a superset of OpenBSD's getentropy(2) call, for use
  with userspace crypto libraries such as LibreSSL.

  Also add the ability to have a kernel thread to pull entropy from
  hardware rng devices into /dev/random"

* tag 'random_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random:
  hwrng: Pass entropy to add_hwgenerator_randomness() in bits, not bytes
  random: limit the contribution of the hw rng to at most half
  random: introduce getrandom(2) system call
  hw_random: fix sparse warning (NULL vs 0 for pointer)
  random: use registers from interrupted code for CPU's w/o a cycle counter
  hwrng: add per-device entropy derating
  hwrng: create filler thread
  random: add_hwgenerator_randomness() for feeding entropy from devices
  random: use an improved fast_mix() function
  random: clean up interrupt entropy accounting for archs w/o cycle counters
  random: only update the last_pulled time if we actually transferred entropy
  random: remove unneeded hash of a portion of the entropy pool
  random: always update the entropy pool under the spinlock

2 files changed, 252 insertions, 130 deletions

diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index c4419ea1ab07..6e02ec103cc7 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -38,6 +38,7 @@
 #include <linux/fs.h>
 #include <linux/sched.h>
 #include <linux/miscdevice.h>
+#include <linux/kthread.h>
 #include <linux/delay.h>
 #include <linux/slab.h>
 #include <linux/random.h>
@@ -50,10 +51,22 @@
 
 
 static struct hwrng *current_rng;
+static struct task_struct *hwrng_fill;
 static LIST_HEAD(rng_list);
 static DEFINE_MUTEX(rng_mutex);
 static int data_avail;
-static u8 *rng_buffer;
+static u8 *rng_buffer, *rng_fillbuf;
+static unsigned short current_quality;
+static unsigned short default_quality; /* = 0; default to "off" */
+
+module_param(current_quality, ushort, 0644);
+MODULE_PARM_DESC(current_quality,
+                 "current hwrng entropy estimation per mill");
+module_param(default_quality, ushort, 0644);
+MODULE_PARM_DESC(default_quality,
+                 "default entropy content of hwrng per mill");
+
+static void start_khwrngd(void);
 
 static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
                                int wait);
@@ -89,6 +102,15 @@ static inline int hwrng_init(struct hwrng *rng)
                         return ret;
         }
         add_early_randomness(rng);
+
+        current_quality = rng->quality ? : default_quality;
+        current_quality &= 1023;
+
+        if (current_quality == 0 && hwrng_fill)
+                kthread_stop(hwrng_fill);
+        if (current_quality > 0 && !hwrng_fill)
+                start_khwrngd();
+
         return 0;
 }
 
@@ -325,6 +347,36 @@ err_misc_dereg:
         goto out;
 }
 
+static int hwrng_fillfn(void *unused)
+{
+        long rc;
+
+        while (!kthread_should_stop()) {
+                if (!current_rng)
+                        break;
+                rc = rng_get_data(current_rng, rng_fillbuf,
+                                  rng_buffer_size(), 1);
+                if (rc <= 0) {
+                        pr_warn("hwrng: no data available\n");
+                        msleep_interruptible(10000);
+                        continue;
+                }
+                add_hwgenerator_randomness((void *)rng_fillbuf, rc,
+                                           rc * current_quality * 8 >> 10);
+        }
+        hwrng_fill = NULL;
+        return 0;
+}
+
+static void start_khwrngd(void)
+{
+        hwrng_fill = kthread_run(hwrng_fillfn, NULL, "hwrng");
+        if (hwrng_fill == ERR_PTR(-ENOMEM)) {
+                pr_err("hwrng_fill thread creation failed");
+                hwrng_fill = NULL;
+        }
+}
+
 int hwrng_register(struct hwrng *rng)
 {
         int err = -EINVAL;
@@ -343,6 +395,13 @@ int hwrng_register(struct hwrng *rng)
                 if (!rng_buffer)
                         goto out_unlock;
         }
+        if (!rng_fillbuf) {
+                rng_fillbuf = kmalloc(rng_buffer_size(), GFP_KERNEL);
+                if (!rng_fillbuf) {
+                        kfree(rng_buffer);
+                        goto out_unlock;
+                }
+        }
 
         /* Must not register two RNGs with the same name. */
         err = -EEXIST;
@@ -406,8 +465,11 @@ void hwrng_unregister(struct hwrng *rng)
                                 current_rng = NULL;
                 }
         }
-        if (list_empty(&rng_list))
+        if (list_empty(&rng_list)) {
                 unregister_miscdev();
+                if (hwrng_fill)
+                        kthread_stop(hwrng_fill);
+        }
 
         mutex_unlock(&rng_mutex);
 }
@@ -418,6 +480,7 @@ static void __exit hwrng_exit(void)
         mutex_lock(&rng_mutex);
         BUG_ON(current_rng);
         kfree(rng_buffer);
+        kfree(rng_fillbuf);
         mutex_unlock(&rng_mutex);
 }
 
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 71529e196b84..c18d41db83d8 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -250,6 +250,7 @@
 #include <linux/interrupt.h>
 #include <linux/mm.h>
 #include <linux/spinlock.h>
+#include <linux/kthread.h>
 #include <linux/percpu.h>
 #include <linux/cryptohash.h>
 #include <linux/fips.h>
@@ -257,6 +258,8 @@
 #include <linux/kmemcheck.h>
 #include <linux/workqueue.h>
 #include <linux/irq.h>
+#include <linux/syscalls.h>
+#include <linux/completion.h>
 
 #include <asm/processor.h>
 #include <asm/uaccess.h>
@@ -267,6 +270,8 @@
 #define CREATE_TRACE_POINTS
 #include <trace/events/random.h>
 
+/* #define ADD_INTERRUPT_BENCH */
+
 /*
  * Configuration information
  */
@@ -401,6 +406,7 @@ static struct poolinfo {
  */
 static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
 static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
+static DECLARE_WAIT_QUEUE_HEAD(urandom_init_wait);
 static struct fasync_struct *fasync;
 
 /**********************************************************************
@@ -481,9 +487,9 @@ static __u32 const twist_table[8] = {
  * the entropy is concentrated in the low-order bits.
  */
 static void _mix_pool_bytes(struct entropy_store *r, const void *in,
-                            int nbytes, __u8 out[64])
+                            int nbytes)
 {
-        unsigned long i, j, tap1, tap2, tap3, tap4, tap5;
+        unsigned long i, tap1, tap2, tap3, tap4, tap5;
         int input_rotate;
         int wordmask = r->poolinfo->poolwords - 1;
         const char *bytes = in;
@@ -495,9 +501,8 @@ static void _mix_pool_bytes(struct entropy_store *r, const void *in,
         tap4 = r->poolinfo->tap4;
         tap5 = r->poolinfo->tap5;
 
-        smp_rmb();
-        input_rotate = ACCESS_ONCE(r->input_rotate);
-        i = ACCESS_ONCE(r->add_ptr);
+        input_rotate = r->input_rotate;
+        i = r->add_ptr;
 
         /* mix one byte at a time to simplify size handling and churn faster */
         while (nbytes--) {
@@ -524,39 +529,33 @@ static void _mix_pool_bytes(struct entropy_store *r, const void *in,
                 input_rotate = (input_rotate + (i ? 7 : 14)) & 31;
         }
 
-        ACCESS_ONCE(r->input_rotate) = input_rotate;
-        ACCESS_ONCE(r->add_ptr) = i;
-        smp_wmb();
-
-        if (out)
-                for (j = 0; j < 16; j++)
-                        ((__u32 *)out)[j] = r->pool[(i - j) & wordmask];
+        r->input_rotate = input_rotate;
+        r->add_ptr = i;
 }
 
 static void __mix_pool_bytes(struct entropy_store *r, const void *in,
-                             int nbytes, __u8 out[64])
+                             int nbytes)
 {
         trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
-        _mix_pool_bytes(r, in, nbytes, out);
+        _mix_pool_bytes(r, in, nbytes);
 }
 
 static void mix_pool_bytes(struct entropy_store *r, const void *in,
-                           int nbytes, __u8 out[64])
+                           int nbytes)
 {
         unsigned long flags;
 
         trace_mix_pool_bytes(r->name, nbytes, _RET_IP_);
         spin_lock_irqsave(&r->lock, flags);
-        _mix_pool_bytes(r, in, nbytes, out);
+        _mix_pool_bytes(r, in, nbytes);
         spin_unlock_irqrestore(&r->lock, flags);
 }
 
 struct fast_pool {
         __u32           pool[4];
         unsigned long   last;
-        unsigned short  count;
-        unsigned char   rotate;
-        unsigned char   last_timer_intr;
+        unsigned short  reg_idx;
+        unsigned char   count;
 };
 
 /*
@@ -564,25 +563,29 @@ struct fast_pool {
  * collector.  It's hardcoded for an 128 bit pool and assumes that any
  * locks that might be needed are taken by the caller.
  */
-static void fast_mix(struct fast_pool *f, __u32 input[4])
+static void fast_mix(struct fast_pool *f)
 {
-        __u32           w;
-        unsigned        input_rotate = f->rotate;
-
-        w = rol32(input[0], input_rotate) ^ f->pool[0] ^ f->pool[3];
-        f->pool[0] = (w >> 3) ^ twist_table[w & 7];
-        input_rotate = (input_rotate + 14) & 31;
-        w = rol32(input[1], input_rotate) ^ f->pool[1] ^ f->pool[0];
-        f->pool[1] = (w >> 3) ^ twist_table[w & 7];
-        input_rotate = (input_rotate + 7) & 31;
-        w = rol32(input[2], input_rotate) ^ f->pool[2] ^ f->pool[1];
-        f->pool[2] = (w >> 3) ^ twist_table[w & 7];
-        input_rotate = (input_rotate + 7) & 31;
-        w = rol32(input[3], input_rotate) ^ f->pool[3] ^ f->pool[2];
-        f->pool[3] = (w >> 3) ^ twist_table[w & 7];
-        input_rotate = (input_rotate + 7) & 31;
-
-        f->rotate = input_rotate;
+        __u32 a = f->pool[0],   b = f->pool[1];
+        __u32 c = f->pool[2],   d = f->pool[3];
+
+        a += b;                 c += d;
+        b = rol32(a, 6);        d = rol32(c, 27);
+        d ^= a;                 b ^= c;
+
+        a += b;                 c += d;
+        b = rol32(a, 16);       d = rol32(c, 14);
+        d ^= a;                 b ^= c;
+
+        a += b;                 c += d;
+        b = rol32(a, 6);        d = rol32(c, 27);
+        d ^= a;                 b ^= c;
+
+        a += b;                 c += d;
+        b = rol32(a, 16);       d = rol32(c, 14);
+        d ^= a;                 b ^= c;
+
+        f->pool[0] = a;  f->pool[1] = b;
+        f->pool[2] = c;  f->pool[3] = d;
         f->count++;
 }
 
@@ -657,6 +660,7 @@ retry:
                 r->entropy_total = 0;
                 if (r == &nonblocking_pool) {
                         prandom_reseed_late();
+                        wake_up_interruptible(&urandom_init_wait);
                         pr_notice("random: %s pool is initialized\n", r->name);
                 }
         }
@@ -739,13 +743,13 @@ void add_device_randomness(const void *buf, unsigned int size)
 
         trace_add_device_randomness(size, _RET_IP_);
         spin_lock_irqsave(&input_pool.lock, flags);
-        _mix_pool_bytes(&input_pool, buf, size, NULL);
-        _mix_pool_bytes(&input_pool, &time, sizeof(time), NULL);
+        _mix_pool_bytes(&input_pool, buf, size);
+        _mix_pool_bytes(&input_pool, &time, sizeof(time));
         spin_unlock_irqrestore(&input_pool.lock, flags);
 
         spin_lock_irqsave(&nonblocking_pool.lock, flags);
-        _mix_pool_bytes(&nonblocking_pool, buf, size, NULL);
-        _mix_pool_bytes(&nonblocking_pool, &time, sizeof(time), NULL);
+        _mix_pool_bytes(&nonblocking_pool, buf, size);
+        _mix_pool_bytes(&nonblocking_pool, &time, sizeof(time));
         spin_unlock_irqrestore(&nonblocking_pool.lock, flags);
 }
 EXPORT_SYMBOL(add_device_randomness);
@@ -778,7 +782,7 @@ static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
         sample.cycles = random_get_entropy();
         sample.num = num;
         r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
-        mix_pool_bytes(r, &sample, sizeof(sample), NULL);
+        mix_pool_bytes(r, &sample, sizeof(sample));
 
         /*
          * Calculate number of bits of randomness we probably added.
@@ -835,6 +839,38 @@ EXPORT_SYMBOL_GPL(add_input_randomness);
 
 static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
 
+#ifdef ADD_INTERRUPT_BENCH
+static unsigned long avg_cycles, avg_deviation;
+
+#define AVG_SHIFT 8     /* Exponential average factor k=1/256 */
+#define FIXED_1_2 (1 << (AVG_SHIFT-1))
+
+static void add_interrupt_bench(cycles_t start)
+{
+        long delta = random_get_entropy() - start;
+
+        /* Use a weighted moving average */
+        delta = delta - ((avg_cycles + FIXED_1_2) >> AVG_SHIFT);
+        avg_cycles += delta;
+        /* And average deviation */
+        delta = abs(delta) - ((avg_deviation + FIXED_1_2) >> AVG_SHIFT);
+        avg_deviation += delta;
+}
+#else
+#define add_interrupt_bench(x)
+#endif
+
+static __u32 get_reg(struct fast_pool *f, struct pt_regs *regs)
+{
+        __u32 *ptr = (__u32 *) regs;
+
+        if (regs == NULL)
+                return 0;
+        if (f->reg_idx >= sizeof(struct pt_regs) / sizeof(__u32))
+                f->reg_idx = 0;
+        return *(ptr + f->reg_idx++);
+}
+
 void add_interrupt_randomness(int irq, int irq_flags)
 {
         struct entropy_store    *r;
@@ -842,55 +878,52 @@ void add_interrupt_randomness(int irq, int irq_flags)
         struct pt_regs          *regs = get_irq_regs();
         unsigned long           now = jiffies;
         cycles_t                cycles = random_get_entropy();
-        __u32                   input[4], c_high, j_high;
+        __u32                   c_high, j_high;
         __u64                   ip;
         unsigned long           seed;
-        int                     credit;
+        int                     credit = 0;
 
+        if (cycles == 0)
+                cycles = get_reg(fast_pool, regs);
         c_high = (sizeof(cycles) > 4) ? cycles >> 32 : 0;
         j_high = (sizeof(now) > 4) ? now >> 32 : 0;
-        input[0] = cycles ^ j_high ^ irq;
-        input[1] = now ^ c_high;
+        fast_pool->pool[0] ^= cycles ^ j_high ^ irq;
+        fast_pool->pool[1] ^= now ^ c_high;
         ip = regs ? instruction_pointer(regs) : _RET_IP_;
-        input[2] = ip;
-        input[3] = ip >> 32;
+        fast_pool->pool[2] ^= ip;
+        fast_pool->pool[3] ^= (sizeof(ip) > 4) ? ip >> 32 :
+                get_reg(fast_pool, regs);
 
-        fast_mix(fast_pool, input);
+        fast_mix(fast_pool);
+        add_interrupt_bench(cycles);
 
-        if ((fast_pool->count & 63) && !time_after(now, fast_pool->last + HZ))
+        if ((fast_pool->count < 64) &&
+            !time_after(now, fast_pool->last + HZ))
                 return;
 
-        fast_pool->last = now;
-
         r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
-        __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool), NULL);
+        if (!spin_trylock(&r->lock))
+                return;
 
-        /*
-         * If we don't have a valid cycle counter, and we see
-         * back-to-back timer interrupts, then skip giving credit for
-         * any entropy, otherwise credit 1 bit.
-         */
-        credit = 1;
-        if (cycles == 0) {
-                if (irq_flags & __IRQF_TIMER) {
-                        if (fast_pool->last_timer_intr)
-                                credit = 0;
-                        fast_pool->last_timer_intr = 1;
-                } else
-                        fast_pool->last_timer_intr = 0;
-        }
+        fast_pool->last = now;
+        __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool));
 
         /*
          * If we have architectural seed generator, produce a seed and
-         * add it to the pool.  For the sake of paranoia count it as
-         * 50% entropic.
+         * add it to the pool.  For the sake of paranoia don't let the
+         * architectural seed generator dominate the input from the
+         * interrupt noise.
          */
         if (arch_get_random_seed_long(&seed)) {
-                __mix_pool_bytes(r, &seed, sizeof(seed), NULL);
-                credit += sizeof(seed) * 4;
+                __mix_pool_bytes(r, &seed, sizeof(seed));
+                credit = 1;
         }
+        spin_unlock(&r->lock);
 
-        credit_entropy_bits(r, credit);
+        fast_pool->count = 0;
+
+        /* award one bit for the contents of the fast pool */
+        credit_entropy_bits(r, credit + 1);
 }
 
 #ifdef CONFIG_BLOCK
@@ -922,6 +955,11 @@ static ssize_t extract_entropy(struct entropy_store *r, void *buf,
 static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes);
 static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
 {
+        if (!r->pull ||
+            r->entropy_count >= (nbytes << (ENTROPY_SHIFT + 3)) ||
+            r->entropy_count > r->poolinfo->poolfracbits)
+                return;
+
         if (r->limit == 0 && random_min_urandom_seed) {
                 unsigned long now = jiffies;
 
@@ -930,10 +968,8 @@ static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
                         return;
                 r->last_pulled = now;
         }
-        if (r->pull &&
-            r->entropy_count < (nbytes << (ENTROPY_SHIFT + 3)) &&
-            r->entropy_count < r->poolinfo->poolfracbits)
-                _xfer_secondary_pool(r, nbytes);
+
+        _xfer_secondary_pool(r, nbytes);
 }
 
 static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
@@ -953,7 +989,7 @@ static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
                                   ENTROPY_BITS(r), ENTROPY_BITS(r->pull));
         bytes = extract_entropy(r->pull, tmp, bytes,
                                 random_read_wakeup_bits / 8, rsvd_bytes);
-        mix_pool_bytes(r, tmp, bytes, NULL);
+        mix_pool_bytes(r, tmp, bytes);
         credit_entropy_bits(r, bytes*8);
 }
 
@@ -1039,7 +1075,6 @@ static void extract_buf(struct entropy_store *r, __u8 *out)
                 unsigned long l[LONGS(20)];
         } hash;
         __u32 workspace[SHA_WORKSPACE_WORDS];
-        __u8 extract[64];
         unsigned long flags;
 
         /*
@@ -1068,15 +1103,9 @@ static void extract_buf(struct entropy_store *r, __u8 *out)
          * brute-forcing the feedback as hard as brute-forcing the
          * hash.
          */
-        __mix_pool_bytes(r, hash.w, sizeof(hash.w), extract);
+        __mix_pool_bytes(r, hash.w, sizeof(hash.w));
         spin_unlock_irqrestore(&r->lock, flags);
 
-        /*
-         * To avoid duplicates, we atomically extract a portion of the
-         * pool while mixing, and hash one final time.
-         */
-        sha_transform(hash.w, extract, workspace);
-        memset(extract, 0, sizeof(extract));
         memset(workspace, 0, sizeof(workspace));
 
         /*
@@ -1160,13 +1189,14 @@ static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
 {
         ssize_t ret = 0, i;
         __u8 tmp[EXTRACT_SIZE];
+        int large_request = (nbytes > 256);
 
         trace_extract_entropy_user(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
         xfer_secondary_pool(r, nbytes);
         nbytes = account(r, nbytes, 0, 0);
 
         while (nbytes) {
-                if (need_resched()) {
+                if (large_request && need_resched()) {
                         if (signal_pending(current)) {
                                 if (ret == 0)
                                         ret = -ERESTARTSYS;
@@ -1263,14 +1293,14 @@ static void init_std_data(struct entropy_store *r)
         unsigned long rv;
 
         r->last_pulled = jiffies;
-        mix_pool_bytes(r, &now, sizeof(now), NULL);
+        mix_pool_bytes(r, &now, sizeof(now));
         for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) {
                 if (!arch_get_random_seed_long(&rv) &&
                     !arch_get_random_long(&rv))
                         rv = random_get_entropy();
-                mix_pool_bytes(r, &rv, sizeof(rv), NULL);
+                mix_pool_bytes(r, &rv, sizeof(rv));
         }
-        mix_pool_bytes(r, utsname(), sizeof(*(utsname())), NULL);
+        mix_pool_bytes(r, utsname(), sizeof(*(utsname())));
 }
 
 /*
@@ -1309,39 +1339,8 @@ void rand_initialize_disk(struct gendisk *disk)
 }
 #endif
 
-/*
- * Attempt an emergency refill using arch_get_random_seed_long().
- *
- * As with add_interrupt_randomness() be paranoid and only
- * credit the output as 50% entropic.
- */
-static int arch_random_refill(void)
-{
-        const unsigned int nlongs = 64; /* Arbitrary number */
-        unsigned int n = 0;
-        unsigned int i;
-        unsigned long buf[nlongs];
-
-        if (!arch_has_random_seed())
-                return 0;
-
-        for (i = 0; i < nlongs; i++) {
-                if (arch_get_random_seed_long(&buf[n]))
-                        n++;
-        }
-
-        if (n) {
-                unsigned int rand_bytes = n * sizeof(unsigned long);
-
-                mix_pool_bytes(&input_pool, buf, rand_bytes, NULL);
-                credit_entropy_bits(&input_pool, rand_bytes*4);
-        }
-
-        return n;
-}
-
 static ssize_t
-random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
+_random_read(int nonblock, char __user *buf, size_t nbytes)
 {
         ssize_t n;
 
@@ -1360,12 +1359,7 @@ random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
                         return n;
 
                 /* Pool is (near) empty.  Maybe wait and retry. */
-
-                /* First try an emergency refill */
-                if (arch_random_refill())
-                        continue;
-
-                if (file->f_flags & O_NONBLOCK)
+                if (nonblock)
                         return -EAGAIN;
 
                 wait_event_interruptible(random_read_wait,
@@ -1377,6 +1371,12 @@ random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
 }
 
 static ssize_t
+random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
+{
+        return _random_read(file->f_flags & O_NONBLOCK, buf, nbytes);
+}
+
+static ssize_t
 urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
 {
         int ret;
@@ -1424,7 +1424,7 @@ write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
                 count -= bytes;
                 p += bytes;
 
-                mix_pool_bytes(r, buf, bytes, NULL);
+                mix_pool_bytes(r, buf, bytes);
                 cond_resched();
         }
 
@@ -1520,6 +1520,29 @@ const struct file_operations urandom_fops = {
         .llseek = noop_llseek,
 };
 
+SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count,
+                unsigned int, flags)
+{
+        if (flags & ~(GRND_NONBLOCK|GRND_RANDOM))
+                return -EINVAL;
+
+        if (count > INT_MAX)
+                count = INT_MAX;
+
+        if (flags & GRND_RANDOM)
+                return _random_read(flags & GRND_NONBLOCK, buf, count);
+
+        if (unlikely(nonblocking_pool.initialized == 0)) {
+                if (flags & GRND_NONBLOCK)
+                        return -EAGAIN;
+                wait_event_interruptible(urandom_init_wait,
+                                         nonblocking_pool.initialized);
+                if (signal_pending(current))
+                        return -ERESTARTSYS;
+        }
+        return urandom_read(NULL, buf, count, NULL);
+}
+
 /***************************************************************
  * Random UUID interface
  *
@@ -1663,6 +1686,22 @@ struct ctl_table random_table[] = {
                 .mode           = 0444,
                 .proc_handler   = proc_do_uuid,
         },
+#ifdef ADD_INTERRUPT_BENCH
+        {
+                .procname       = "add_interrupt_avg_cycles",
+                .data           = &avg_cycles,
+                .maxlen         = sizeof(avg_cycles),
+                .mode           = 0444,
+                .proc_handler   = proc_doulongvec_minmax,
+        },
+        {
+                .procname       = "add_interrupt_avg_deviation",
+                .data           = &avg_deviation,
+                .maxlen         = sizeof(avg_deviation),
+                .mode           = 0444,
+                .proc_handler   = proc_doulongvec_minmax,
+        },
+#endif
         { }
 };
 #endif  /* CONFIG_SYSCTL */
@@ -1719,3 +1758,23 @@ randomize_range(unsigned long start, unsigned long end, unsigned long len)
                 return 0;
         return PAGE_ALIGN(get_random_int() % range + start);
 }
+
+/* Interface for in-kernel drivers of true hardware RNGs.
+ * Those devices may produce endless random bits and will be throttled
+ * when our pool is full.
+ */
+void add_hwgenerator_randomness(const char *buffer, size_t count,
+                                size_t entropy)
+{
+        struct entropy_store *poolp = &input_pool;
+
+        /* Suspend writing if we're above the trickle threshold.
+         * We'll be woken up again once below random_write_wakeup_thresh,
+         * or when the calling thread is about to terminate.
+         */
+        wait_event_interruptible(random_write_wait, kthread_should_stop() ||
+                        ENTROPY_BITS(&input_pool) <= random_write_wakeup_bits);
+        mix_pool_bytes(poolp, buffer, count);
+        credit_entropy_bits(poolp, entropy);
+}
+EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);