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authorLinus Torvalds <torvalds@linux-foundation.org>2014-08-06 08:16:24 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-08-06 08:16:24 -0700
commitf4f142ed4ef835709c7e6d12eaca10d190bcebed (patch)
treea0bc6850239fe3551bb67f5707bfef153ac437fe /drivers/char/random.c
parentbb2cbf5e9367d8598fecd0c48dead69560750223 (diff)
parente02b876597777ab26288dd2611a97b597d14d661 (diff)
downloadleg-kernel-f4f142ed4ef835709c7e6d12eaca10d190bcebed.tar.gz
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
Diffstat (limited to 'drivers/char/random.c')
-rw-r--r--drivers/char/random.c315
1 files changed, 187 insertions, 128 deletions
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);