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645 lines
13 KiB
645 lines
13 KiB
/* |
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* hw_random/core.c: HWRNG core API |
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* |
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* Copyright 2006 Michael Buesch <[email protected]> |
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* Copyright 2005 (c) MontaVista Software, Inc. |
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* |
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* Please read Documentation/admin-guide/hw_random.rst for details on use. |
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* |
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* This software may be used and distributed according to the terms |
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* of the GNU General Public License, incorporated herein by reference. |
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*/ |
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|
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#include <linux/delay.h> |
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#include <linux/device.h> |
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#include <linux/err.h> |
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#include <linux/fs.h> |
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#include <linux/hw_random.h> |
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#include <linux/kernel.h> |
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#include <linux/kthread.h> |
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#include <linux/sched/signal.h> |
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#include <linux/miscdevice.h> |
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#include <linux/module.h> |
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#include <linux/random.h> |
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#include <linux/sched.h> |
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#include <linux/slab.h> |
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#include <linux/uaccess.h> |
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#define RNG_MODULE_NAME "hw_random" |
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static struct hwrng *current_rng; |
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/* the current rng has been explicitly chosen by user via sysfs */ |
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static int cur_rng_set_by_user; |
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static struct task_struct *hwrng_fill; |
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/* list of registered rngs, sorted decending by quality */ |
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static LIST_HEAD(rng_list); |
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/* Protects rng_list and current_rng */ |
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static DEFINE_MUTEX(rng_mutex); |
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/* Protects rng read functions, data_avail, rng_buffer and rng_fillbuf */ |
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static DEFINE_MUTEX(reading_mutex); |
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static int data_avail; |
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static u8 *rng_buffer, *rng_fillbuf; |
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static unsigned short current_quality; |
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static unsigned short default_quality; /* = 0; default to "off" */ |
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module_param(current_quality, ushort, 0644); |
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MODULE_PARM_DESC(current_quality, |
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"current hwrng entropy estimation per 1024 bits of input"); |
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module_param(default_quality, ushort, 0644); |
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MODULE_PARM_DESC(default_quality, |
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"default entropy content of hwrng per 1024 bits of input"); |
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static void drop_current_rng(void); |
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static int hwrng_init(struct hwrng *rng); |
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static void start_khwrngd(void); |
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static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size, |
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int wait); |
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static size_t rng_buffer_size(void) |
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{ |
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return SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES; |
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} |
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static void add_early_randomness(struct hwrng *rng) |
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{ |
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int bytes_read; |
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size_t size = min_t(size_t, 16, rng_buffer_size()); |
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mutex_lock(&reading_mutex); |
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bytes_read = rng_get_data(rng, rng_buffer, size, 0); |
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mutex_unlock(&reading_mutex); |
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if (bytes_read > 0) |
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add_device_randomness(rng_buffer, bytes_read); |
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} |
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static inline void cleanup_rng(struct kref *kref) |
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{ |
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struct hwrng *rng = container_of(kref, struct hwrng, ref); |
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if (rng->cleanup) |
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rng->cleanup(rng); |
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complete(&rng->cleanup_done); |
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} |
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static int set_current_rng(struct hwrng *rng) |
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{ |
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int err; |
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BUG_ON(!mutex_is_locked(&rng_mutex)); |
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err = hwrng_init(rng); |
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if (err) |
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return err; |
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drop_current_rng(); |
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current_rng = rng; |
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return 0; |
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} |
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static void drop_current_rng(void) |
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{ |
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BUG_ON(!mutex_is_locked(&rng_mutex)); |
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if (!current_rng) |
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return; |
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/* decrease last reference for triggering the cleanup */ |
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kref_put(¤t_rng->ref, cleanup_rng); |
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current_rng = NULL; |
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} |
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/* Returns ERR_PTR(), NULL or refcounted hwrng */ |
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static struct hwrng *get_current_rng_nolock(void) |
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{ |
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if (current_rng) |
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kref_get(¤t_rng->ref); |
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return current_rng; |
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} |
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static struct hwrng *get_current_rng(void) |
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{ |
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struct hwrng *rng; |
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if (mutex_lock_interruptible(&rng_mutex)) |
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return ERR_PTR(-ERESTARTSYS); |
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rng = get_current_rng_nolock(); |
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mutex_unlock(&rng_mutex); |
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return rng; |
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} |
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static void put_rng(struct hwrng *rng) |
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{ |
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/* |
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* Hold rng_mutex here so we serialize in case they set_current_rng |
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* on rng again immediately. |
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*/ |
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mutex_lock(&rng_mutex); |
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if (rng) |
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kref_put(&rng->ref, cleanup_rng); |
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mutex_unlock(&rng_mutex); |
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} |
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static int hwrng_init(struct hwrng *rng) |
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{ |
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if (kref_get_unless_zero(&rng->ref)) |
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goto skip_init; |
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if (rng->init) { |
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int ret; |
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ret = rng->init(rng); |
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if (ret) |
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return ret; |
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} |
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kref_init(&rng->ref); |
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reinit_completion(&rng->cleanup_done); |
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skip_init: |
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current_quality = rng->quality ? : default_quality; |
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if (current_quality > 1024) |
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current_quality = 1024; |
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if (current_quality == 0 && hwrng_fill) |
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kthread_stop(hwrng_fill); |
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if (current_quality > 0 && !hwrng_fill) |
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start_khwrngd(); |
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return 0; |
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} |
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static int rng_dev_open(struct inode *inode, struct file *filp) |
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{ |
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/* enforce read-only access to this chrdev */ |
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if ((filp->f_mode & FMODE_READ) == 0) |
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return -EINVAL; |
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if (filp->f_mode & FMODE_WRITE) |
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return -EINVAL; |
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return 0; |
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} |
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static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size, |
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int wait) { |
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int present; |
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BUG_ON(!mutex_is_locked(&reading_mutex)); |
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if (rng->read) |
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return rng->read(rng, (void *)buffer, size, wait); |
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if (rng->data_present) |
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present = rng->data_present(rng, wait); |
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else |
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present = 1; |
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if (present) |
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return rng->data_read(rng, (u32 *)buffer); |
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return 0; |
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} |
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static ssize_t rng_dev_read(struct file *filp, char __user *buf, |
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size_t size, loff_t *offp) |
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{ |
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ssize_t ret = 0; |
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int err = 0; |
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int bytes_read, len; |
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struct hwrng *rng; |
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while (size) { |
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rng = get_current_rng(); |
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if (IS_ERR(rng)) { |
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err = PTR_ERR(rng); |
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goto out; |
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} |
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if (!rng) { |
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err = -ENODEV; |
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goto out; |
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} |
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if (mutex_lock_interruptible(&reading_mutex)) { |
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err = -ERESTARTSYS; |
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goto out_put; |
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} |
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if (!data_avail) { |
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bytes_read = rng_get_data(rng, rng_buffer, |
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rng_buffer_size(), |
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!(filp->f_flags & O_NONBLOCK)); |
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if (bytes_read < 0) { |
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err = bytes_read; |
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goto out_unlock_reading; |
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} |
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data_avail = bytes_read; |
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} |
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if (!data_avail) { |
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if (filp->f_flags & O_NONBLOCK) { |
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err = -EAGAIN; |
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goto out_unlock_reading; |
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} |
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} else { |
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len = data_avail; |
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if (len > size) |
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len = size; |
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data_avail -= len; |
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if (copy_to_user(buf + ret, rng_buffer + data_avail, |
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len)) { |
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err = -EFAULT; |
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goto out_unlock_reading; |
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} |
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size -= len; |
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ret += len; |
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} |
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mutex_unlock(&reading_mutex); |
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put_rng(rng); |
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if (need_resched()) |
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schedule_timeout_interruptible(1); |
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if (signal_pending(current)) { |
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err = -ERESTARTSYS; |
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goto out; |
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} |
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} |
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out: |
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return ret ? : err; |
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out_unlock_reading: |
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mutex_unlock(&reading_mutex); |
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out_put: |
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put_rng(rng); |
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goto out; |
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} |
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static const struct file_operations rng_chrdev_ops = { |
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.owner = THIS_MODULE, |
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.open = rng_dev_open, |
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.read = rng_dev_read, |
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.llseek = noop_llseek, |
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}; |
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static const struct attribute_group *rng_dev_groups[]; |
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static struct miscdevice rng_miscdev = { |
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.minor = HWRNG_MINOR, |
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.name = RNG_MODULE_NAME, |
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.nodename = "hwrng", |
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.fops = &rng_chrdev_ops, |
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.groups = rng_dev_groups, |
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}; |
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static int enable_best_rng(void) |
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{ |
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int ret = -ENODEV; |
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BUG_ON(!mutex_is_locked(&rng_mutex)); |
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/* rng_list is sorted by quality, use the best (=first) one */ |
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if (!list_empty(&rng_list)) { |
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struct hwrng *new_rng; |
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new_rng = list_entry(rng_list.next, struct hwrng, list); |
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ret = ((new_rng == current_rng) ? 0 : set_current_rng(new_rng)); |
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if (!ret) |
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cur_rng_set_by_user = 0; |
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} else { |
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drop_current_rng(); |
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cur_rng_set_by_user = 0; |
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ret = 0; |
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} |
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return ret; |
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} |
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static ssize_t rng_current_store(struct device *dev, |
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struct device_attribute *attr, |
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const char *buf, size_t len) |
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{ |
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int err; |
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struct hwrng *rng, *old_rng, *new_rng; |
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err = mutex_lock_interruptible(&rng_mutex); |
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if (err) |
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return -ERESTARTSYS; |
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old_rng = current_rng; |
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if (sysfs_streq(buf, "")) { |
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err = enable_best_rng(); |
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} else { |
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list_for_each_entry(rng, &rng_list, list) { |
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if (sysfs_streq(rng->name, buf)) { |
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cur_rng_set_by_user = 1; |
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err = set_current_rng(rng); |
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break; |
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} |
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} |
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} |
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new_rng = get_current_rng_nolock(); |
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mutex_unlock(&rng_mutex); |
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if (new_rng) { |
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if (new_rng != old_rng) |
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add_early_randomness(new_rng); |
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put_rng(new_rng); |
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} |
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return err ? : len; |
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} |
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static ssize_t rng_current_show(struct device *dev, |
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struct device_attribute *attr, |
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char *buf) |
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{ |
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ssize_t ret; |
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struct hwrng *rng; |
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rng = get_current_rng(); |
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if (IS_ERR(rng)) |
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return PTR_ERR(rng); |
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ret = snprintf(buf, PAGE_SIZE, "%s\n", rng ? rng->name : "none"); |
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put_rng(rng); |
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return ret; |
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} |
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static ssize_t rng_available_show(struct device *dev, |
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struct device_attribute *attr, |
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char *buf) |
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{ |
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int err; |
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struct hwrng *rng; |
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err = mutex_lock_interruptible(&rng_mutex); |
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if (err) |
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return -ERESTARTSYS; |
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buf[0] = '\0'; |
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list_for_each_entry(rng, &rng_list, list) { |
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strlcat(buf, rng->name, PAGE_SIZE); |
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strlcat(buf, " ", PAGE_SIZE); |
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} |
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strlcat(buf, "\n", PAGE_SIZE); |
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mutex_unlock(&rng_mutex); |
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return strlen(buf); |
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} |
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static ssize_t rng_selected_show(struct device *dev, |
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struct device_attribute *attr, |
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char *buf) |
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{ |
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return sysfs_emit(buf, "%d\n", cur_rng_set_by_user); |
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} |
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static DEVICE_ATTR_RW(rng_current); |
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static DEVICE_ATTR_RO(rng_available); |
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static DEVICE_ATTR_RO(rng_selected); |
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static struct attribute *rng_dev_attrs[] = { |
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&dev_attr_rng_current.attr, |
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&dev_attr_rng_available.attr, |
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&dev_attr_rng_selected.attr, |
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NULL |
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}; |
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ATTRIBUTE_GROUPS(rng_dev); |
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static void __exit unregister_miscdev(void) |
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{ |
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misc_deregister(&rng_miscdev); |
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} |
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static int __init register_miscdev(void) |
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{ |
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return misc_register(&rng_miscdev); |
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} |
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static int hwrng_fillfn(void *unused) |
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{ |
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long rc; |
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while (!kthread_should_stop()) { |
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struct hwrng *rng; |
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rng = get_current_rng(); |
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if (IS_ERR(rng) || !rng) |
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break; |
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mutex_lock(&reading_mutex); |
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rc = rng_get_data(rng, rng_fillbuf, |
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rng_buffer_size(), 1); |
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mutex_unlock(&reading_mutex); |
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put_rng(rng); |
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if (rc <= 0) { |
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pr_warn("hwrng: no data available\n"); |
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msleep_interruptible(10000); |
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continue; |
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} |
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/* Outside lock, sure, but y'know: randomness. */ |
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add_hwgenerator_randomness((void *)rng_fillbuf, rc, |
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rc * current_quality * 8 >> 10); |
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} |
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hwrng_fill = NULL; |
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return 0; |
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} |
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static void start_khwrngd(void) |
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{ |
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hwrng_fill = kthread_run(hwrng_fillfn, NULL, "hwrng"); |
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if (IS_ERR(hwrng_fill)) { |
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pr_err("hwrng_fill thread creation failed\n"); |
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hwrng_fill = NULL; |
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} |
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} |
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int hwrng_register(struct hwrng *rng) |
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{ |
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int err = -EINVAL; |
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struct hwrng *tmp; |
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struct list_head *rng_list_ptr; |
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bool is_new_current = false; |
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if (!rng->name || (!rng->data_read && !rng->read)) |
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goto out; |
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mutex_lock(&rng_mutex); |
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/* Must not register two RNGs with the same name. */ |
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err = -EEXIST; |
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list_for_each_entry(tmp, &rng_list, list) { |
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if (strcmp(tmp->name, rng->name) == 0) |
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goto out_unlock; |
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} |
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init_completion(&rng->cleanup_done); |
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complete(&rng->cleanup_done); |
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/* rng_list is sorted by decreasing quality */ |
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list_for_each(rng_list_ptr, &rng_list) { |
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tmp = list_entry(rng_list_ptr, struct hwrng, list); |
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if (tmp->quality < rng->quality) |
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break; |
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} |
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list_add_tail(&rng->list, rng_list_ptr); |
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if (!current_rng || |
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(!cur_rng_set_by_user && rng->quality > current_rng->quality)) { |
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/* |
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* Set new rng as current as the new rng source |
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* provides better entropy quality and was not |
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* chosen by userspace. |
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*/ |
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err = set_current_rng(rng); |
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if (err) |
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goto out_unlock; |
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/* to use current_rng in add_early_randomness() we need |
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* to take a ref |
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*/ |
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is_new_current = true; |
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kref_get(&rng->ref); |
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} |
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mutex_unlock(&rng_mutex); |
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if (is_new_current || !rng->init) { |
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/* |
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* Use a new device's input to add some randomness to |
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* the system. If this rng device isn't going to be |
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* used right away, its init function hasn't been |
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* called yet by set_current_rng(); so only use the |
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* randomness from devices that don't need an init callback |
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*/ |
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add_early_randomness(rng); |
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} |
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if (is_new_current) |
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put_rng(rng); |
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return 0; |
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out_unlock: |
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mutex_unlock(&rng_mutex); |
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out: |
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return err; |
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} |
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EXPORT_SYMBOL_GPL(hwrng_register); |
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void hwrng_unregister(struct hwrng *rng) |
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{ |
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struct hwrng *old_rng, *new_rng; |
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int err; |
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mutex_lock(&rng_mutex); |
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old_rng = current_rng; |
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list_del(&rng->list); |
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if (current_rng == rng) { |
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err = enable_best_rng(); |
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if (err) { |
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drop_current_rng(); |
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cur_rng_set_by_user = 0; |
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} |
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} |
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new_rng = get_current_rng_nolock(); |
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if (list_empty(&rng_list)) { |
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mutex_unlock(&rng_mutex); |
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if (hwrng_fill) |
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kthread_stop(hwrng_fill); |
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} else |
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mutex_unlock(&rng_mutex); |
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if (new_rng) { |
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if (old_rng != new_rng) |
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add_early_randomness(new_rng); |
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put_rng(new_rng); |
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} |
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wait_for_completion(&rng->cleanup_done); |
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} |
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EXPORT_SYMBOL_GPL(hwrng_unregister); |
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static void devm_hwrng_release(struct device *dev, void *res) |
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{ |
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hwrng_unregister(*(struct hwrng **)res); |
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} |
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static int devm_hwrng_match(struct device *dev, void *res, void *data) |
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{ |
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struct hwrng **r = res; |
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if (WARN_ON(!r || !*r)) |
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return 0; |
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return *r == data; |
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} |
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int devm_hwrng_register(struct device *dev, struct hwrng *rng) |
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{ |
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struct hwrng **ptr; |
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int error; |
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ptr = devres_alloc(devm_hwrng_release, sizeof(*ptr), GFP_KERNEL); |
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if (!ptr) |
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return -ENOMEM; |
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error = hwrng_register(rng); |
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if (error) { |
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devres_free(ptr); |
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return error; |
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} |
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*ptr = rng; |
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devres_add(dev, ptr); |
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return 0; |
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} |
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EXPORT_SYMBOL_GPL(devm_hwrng_register); |
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void devm_hwrng_unregister(struct device *dev, struct hwrng *rng) |
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{ |
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devres_release(dev, devm_hwrng_release, devm_hwrng_match, rng); |
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} |
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EXPORT_SYMBOL_GPL(devm_hwrng_unregister); |
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static int __init hwrng_modinit(void) |
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{ |
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int ret; |
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|
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/* kmalloc makes this safe for virt_to_page() in virtio_rng.c */ |
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rng_buffer = kmalloc(rng_buffer_size(), GFP_KERNEL); |
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if (!rng_buffer) |
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return -ENOMEM; |
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rng_fillbuf = kmalloc(rng_buffer_size(), GFP_KERNEL); |
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if (!rng_fillbuf) { |
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kfree(rng_buffer); |
|
return -ENOMEM; |
|
} |
|
|
|
ret = register_miscdev(); |
|
if (ret) { |
|
kfree(rng_fillbuf); |
|
kfree(rng_buffer); |
|
} |
|
|
|
return ret; |
|
} |
|
|
|
static void __exit hwrng_modexit(void) |
|
{ |
|
mutex_lock(&rng_mutex); |
|
BUG_ON(current_rng); |
|
kfree(rng_buffer); |
|
kfree(rng_fillbuf); |
|
mutex_unlock(&rng_mutex); |
|
|
|
unregister_miscdev(); |
|
} |
|
|
|
module_init(hwrng_modinit); |
|
module_exit(hwrng_modexit); |
|
|
|
MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver"); |
|
MODULE_LICENSE("GPL");
|
|
|