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random: order timer entropy functions below interrupt functions
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There are no code changes here; this is just a reordering of functions,
so that in subsequent commits, the timer entropy functions can call into
the interrupt ones.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
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Jason A. Donenfeld authored and Jason A. Donenfeld committed May 15, 2022
1 parent e85c0fc commit a4b5c26
Showing 1 changed file with 119 additions and 119 deletions.
238 changes: 119 additions & 119 deletions drivers/char/random.c
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Original file line number Diff line number Diff line change
Expand Up @@ -855,14 +855,14 @@ static void credit_init_bits(size_t nbits)
* the above entropy accumulation routines:
*
* void add_device_randomness(const void *buf, size_t size);
* void add_input_randomness(unsigned int type, unsigned int code,
* unsigned int value);
* void add_disk_randomness(struct gendisk *disk);
* void add_hwgenerator_randomness(const void *buffer, size_t count,
* size_t entropy);
* void add_bootloader_randomness(const void *buf, size_t size);
* void add_vmfork_randomness(const void *unique_vm_id, size_t size);
* void add_interrupt_randomness(int irq);
* void add_input_randomness(unsigned int type, unsigned int code,
* unsigned int value);
* void add_disk_randomness(struct gendisk *disk);
*
* add_device_randomness() adds data to the input pool that
* is likely to differ between two devices (or possibly even per boot).
Expand All @@ -872,19 +872,6 @@ static void credit_init_bits(size_t nbits)
* that might otherwise be identical and have very little entropy
* available to them (particularly common in the embedded world).
*
* add_input_randomness() uses the input layer interrupt timing, as well
* as the event type information from the hardware.
*
* add_disk_randomness() uses what amounts to the seek time of block
* layer request events, on a per-disk_devt basis, as input to the
* entropy pool. Note that high-speed solid state drives with very low
* seek times do not make for good sources of entropy, as their seek
* times are usually fairly consistent.
*
* The above two routines try to estimate how many bits of entropy
* to credit. They do this by keeping track of the first and second
* order deltas of the event timings.
*
* add_hwgenerator_randomness() is for true hardware RNGs, and will credit
* entropy as specified by the caller. If the entropy pool is full it will
* block until more entropy is needed.
Expand All @@ -902,6 +889,19 @@ static void credit_init_bits(size_t nbits)
* as inputs, it feeds the input pool roughly once a second or after 64
* interrupts, crediting 1 bit of entropy for whichever comes first.
*
* add_input_randomness() uses the input layer interrupt timing, as well
* as the event type information from the hardware.
*
* add_disk_randomness() uses what amounts to the seek time of block
* layer request events, on a per-disk_devt basis, as input to the
* entropy pool. Note that high-speed solid state drives with very low
* seek times do not make for good sources of entropy, as their seek
* times are usually fairly consistent.
*
* The last two routines try to estimate how many bits of entropy
* to credit. They do this by keeping track of the first and second
* order deltas of the event timings.
*
**********************************************************************/

static bool trust_cpu __ro_after_init = IS_ENABLED(CONFIG_RANDOM_TRUST_CPU);
Expand Down Expand Up @@ -1011,109 +1011,6 @@ void add_device_randomness(const void *buf, size_t size)
}
EXPORT_SYMBOL(add_device_randomness);

/* There is one of these per entropy source */
struct timer_rand_state {
unsigned long last_time;
long last_delta, last_delta2;
};

/*
* This function adds entropy to the entropy "pool" by using timing
* delays. It uses the timer_rand_state structure to make an estimate
* of how many bits of entropy this call has added to the pool.
*
* The number "num" is also added to the pool - it should somehow describe
* the type of event which just happened. This is currently 0-255 for
* keyboard scan codes, and 256 upwards for interrupts.
*/
static void add_timer_randomness(struct timer_rand_state *state, unsigned int num)
{
unsigned long entropy = random_get_entropy(), now = jiffies, flags;
long delta, delta2, delta3;

spin_lock_irqsave(&input_pool.lock, flags);
_mix_pool_bytes(&entropy, sizeof(entropy));
_mix_pool_bytes(&num, sizeof(num));
spin_unlock_irqrestore(&input_pool.lock, flags);

if (crng_ready())
return;

/*
* Calculate number of bits of randomness we probably added.
* We take into account the first, second and third-order deltas
* in order to make our estimate.
*/
delta = now - READ_ONCE(state->last_time);
WRITE_ONCE(state->last_time, now);

delta2 = delta - READ_ONCE(state->last_delta);
WRITE_ONCE(state->last_delta, delta);

delta3 = delta2 - READ_ONCE(state->last_delta2);
WRITE_ONCE(state->last_delta2, delta2);

if (delta < 0)
delta = -delta;
if (delta2 < 0)
delta2 = -delta2;
if (delta3 < 0)
delta3 = -delta3;
if (delta > delta2)
delta = delta2;
if (delta > delta3)
delta = delta3;

/*
* delta is now minimum absolute delta.
* Round down by 1 bit on general principles,
* and limit entropy estimate to 12 bits.
*/
credit_init_bits(min_t(unsigned int, fls(delta >> 1), 11));
}

void add_input_randomness(unsigned int type, unsigned int code,
unsigned int value)
{
static unsigned char last_value;
static struct timer_rand_state input_timer_state = { INITIAL_JIFFIES };

/* Ignore autorepeat and the like. */
if (value == last_value)
return;

last_value = value;
add_timer_randomness(&input_timer_state,
(type << 4) ^ code ^ (code >> 4) ^ value);
}
EXPORT_SYMBOL_GPL(add_input_randomness);

#ifdef CONFIG_BLOCK
void add_disk_randomness(struct gendisk *disk)
{
if (!disk || !disk->random)
return;
/* First major is 1, so we get >= 0x200 here. */
add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
}
EXPORT_SYMBOL_GPL(add_disk_randomness);

void rand_initialize_disk(struct gendisk *disk)
{
struct timer_rand_state *state;

/*
* If kzalloc returns null, we just won't use that entropy
* source.
*/
state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
if (state) {
state->last_time = INITIAL_JIFFIES;
disk->random = state;
}
}
#endif

/*
* Interface for in-kernel drivers of true hardware RNGs.
* Those devices may produce endless random bits and will be throttled
Expand Down Expand Up @@ -1309,6 +1206,109 @@ void add_interrupt_randomness(int irq)
}
EXPORT_SYMBOL_GPL(add_interrupt_randomness);

/* There is one of these per entropy source */
struct timer_rand_state {
unsigned long last_time;
long last_delta, last_delta2;
};

/*
* This function adds entropy to the entropy "pool" by using timing
* delays. It uses the timer_rand_state structure to make an estimate
* of how many bits of entropy this call has added to the pool.
*
* The number "num" is also added to the pool - it should somehow describe
* the type of event which just happened. This is currently 0-255 for
* keyboard scan codes, and 256 upwards for interrupts.
*/
static void add_timer_randomness(struct timer_rand_state *state, unsigned int num)
{
unsigned long entropy = random_get_entropy(), now = jiffies, flags;
long delta, delta2, delta3;

spin_lock_irqsave(&input_pool.lock, flags);
_mix_pool_bytes(&entropy, sizeof(entropy));
_mix_pool_bytes(&num, sizeof(num));
spin_unlock_irqrestore(&input_pool.lock, flags);

if (crng_ready())
return;

/*
* Calculate number of bits of randomness we probably added.
* We take into account the first, second and third-order deltas
* in order to make our estimate.
*/
delta = now - READ_ONCE(state->last_time);
WRITE_ONCE(state->last_time, now);

delta2 = delta - READ_ONCE(state->last_delta);
WRITE_ONCE(state->last_delta, delta);

delta3 = delta2 - READ_ONCE(state->last_delta2);
WRITE_ONCE(state->last_delta2, delta2);

if (delta < 0)
delta = -delta;
if (delta2 < 0)
delta2 = -delta2;
if (delta3 < 0)
delta3 = -delta3;
if (delta > delta2)
delta = delta2;
if (delta > delta3)
delta = delta3;

/*
* delta is now minimum absolute delta.
* Round down by 1 bit on general principles,
* and limit entropy estimate to 12 bits.
*/
credit_init_bits(min_t(unsigned int, fls(delta >> 1), 11));
}

void add_input_randomness(unsigned int type, unsigned int code,
unsigned int value)
{
static unsigned char last_value;
static struct timer_rand_state input_timer_state = { INITIAL_JIFFIES };

/* Ignore autorepeat and the like. */
if (value == last_value)
return;

last_value = value;
add_timer_randomness(&input_timer_state,
(type << 4) ^ code ^ (code >> 4) ^ value);
}
EXPORT_SYMBOL_GPL(add_input_randomness);

#ifdef CONFIG_BLOCK
void add_disk_randomness(struct gendisk *disk)
{
if (!disk || !disk->random)
return;
/* First major is 1, so we get >= 0x200 here. */
add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
}
EXPORT_SYMBOL_GPL(add_disk_randomness);

void rand_initialize_disk(struct gendisk *disk)
{
struct timer_rand_state *state;

/*
* If kzalloc returns null, we just won't use that entropy
* source.
*/
state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
if (state) {
state->last_time = INITIAL_JIFFIES;
disk->random = state;
}
}
#endif

struct entropy_timer_state {
unsigned long entropy;
struct timer_list timer;
Expand Down

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