From: Stephan Mueller Subject: [PATCH v4 2/6] random: Async and sync API for accessing kernel_pool Date: Sun, 03 May 2015 17:33:54 +0200 Message-ID: <1551132.jNO2hp8j9J@tachyon.chronox.de> References: <1626703.0h1HzJAx4d@tachyon.chronox.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Cc: Paul Bolle , Andreas Steffen , tytso@mit.edu, Sandy Harris , linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org To: herbert@gondor.apana.org.au Return-path: Received: from mail.eperm.de ([89.247.134.16]:34681 "EHLO mail.eperm.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750961AbbECPhz (ORCPT ); Sun, 3 May 2015 11:37:55 -0400 In-Reply-To: <1626703.0h1HzJAx4d@tachyon.chronox.de> Sender: linux-crypto-owner@vger.kernel.org List-ID: The kernel_pool is intended to be the in-kernel equivalent to the blocking_pool, i.e. requests for random data may be blocked if insufficient entropy is present. The added API calls provide a synchronous function call get_blocking_random_bytes where the caller is blocked. In addition, an asynchronous API call of get_blocking_random_bytes_cb is provided which returns immediately to the caller after submitting the request for random data. The caller-provided buffer that shall be filled with random data is filled up as available entropy permits. The caller may provide a callback function that is invoked once the request is completed. A third API call, get_blocking_random_bytes_cancel, is provided to cancel the random number gathering operation. CC: Andreas Steffen CC: Theodore Ts'o CC: Sandy Harris Signed-off-by: Stephan Mueller --- drivers/char/random.c | 123 +++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/random.h | 20 ++++++++ 2 files changed, 143 insertions(+) diff --git a/drivers/char/random.c b/drivers/char/random.c index 0b139dc..e9c0144 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1804,3 +1804,126 @@ void add_hwgenerator_randomness(const char *buffer, size_t count, credit_entropy_bits(poolp, entropy); } EXPORT_SYMBOL_GPL(add_hwgenerator_randomness); + +static bool get_blocking_random_bytes_term(bool *cancel) +{ + if (ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits) + return true; + return *cancel; +} + +/* + * Equivalent function to get_random_bytes with the difference that this + * function blocks the request in a similar fashion as random_read(), + * implementing a /dev/random device for in-kernel users. + * + * This function may sleep. + * + * @buf caller allocated buffer filled with random data + * @nbytes requested number of bytes -- buffer should be at least as big + * @cancel pointer to variable that can be used to cancel the collection + * operation. If this boolean is set to true, the collection operation + * is terminated immediately. When it is set to true during the + * collection loop, the collection is terminated immediately. + * + * return: positive value: obtained number of bytes on successful + * negative value: error code on error + */ +ssize_t get_blocking_random_bytes(void *buf, ssize_t nbytes, bool *cancel) +{ + ssize_t ret = 0; + + if (nbytes <= 0) + return nbytes; + BUG_ON(!buf); + + while (ret < nbytes) { + ssize_t round = 0; + ssize_t pull = min_t(ssize_t, (nbytes - ret), SEC_XFER_SIZE); + + if (*cancel) + return ret; + round = extract_entropy(&kernel_pool, (buf + ret), pull, 0, 0); + if (0 > round) + return round; + if (0 == round) + wait_event_interruptible(random_kernel_wait, + get_blocking_random_bytes_term(cancel)); + ret += round; + } + return ret; +} +EXPORT_SYMBOL(get_blocking_random_bytes); + +/* + * Immediate canceling the collection operation for the random_work + */ +void get_blocking_random_bytes_cancel(struct random_work *rw) +{ + rw->cancel = true; + wake_up_interruptible(&random_kernel_wait); + +} +EXPORT_SYMBOL(get_blocking_random_bytes_cancel); + +static void get_blocking_random_bytes_work(struct work_struct *work) +{ + struct random_work *rw = container_of(work, struct random_work, + rw_work); + ssize_t ret; + + ret = get_blocking_random_bytes(rw->rw_buf, rw->rw_len, &rw->cancel); + if (rw->rw_cb) + rw->rw_cb(rw->rw_buf, ret, rw->private); +} + +/* + * Asynchronous invocation of the blocking interface. The function + * queues the request in either the private work queue supplied with the + * wq argument or in the general work queue framework if wq is NULL. + * Once the request is completed or upon receiving an error, the callback + * function of cb is called, if not NULL, to inform the caller about the + * completion of its operation. + * + * Only if no work is pending, the pointers for the callback function + * or the output data can be changed. + * + * If a caller wants to cancel the work (e.g. in the module_exit function), + * simply call + * get_blocking_random_bytes_cancel(&my_random_work); + * cancel_work_sync(&my_random_work.rw_work); + * + * @wq pointer to private work queue or NULL - input + * @rw handle to the work queue frame - output + * @buf allocated buffer where random numbers are to be stored + * @nbytes size of buf and implicitly number of bytes requested + * @private pointer to data that is not processed by here, but handed to the + * callback function to allow the caller to maintain a state + * @cb callback function where + * * buf holds the pointer to buf will be supplied + * * buflen holds the length of the gathered random numbers or error code + * of the generation function. + * * private provides a reference to the private data pointer + */ +void get_blocking_random_bytes_cb(struct workqueue_struct *wq, + struct random_work *rw, + u8 *buf, ssize_t nbytes, void *private, + void (*cb)(void *buf, ssize_t buflen, + void *private)) +{ + BUG_ON(!cb); + if (!rw->cb) + INIT_WORK(&rw->rw_work, get_blocking_random_bytes_work); + if (!work_pending(&rw->rw_work)) { + rw->rw_buf = buf; + rw->rw_len = nbytes; + rw->private = private; + rw->rw_cb = cb; + rw->cancel = false; + | + if (wq) + queue_work(wq, &rw->rw_work); + else + schedule_work(&rw->rw_work); +} +EXPORT_SYMBOL(get_blocking_random_bytes_cb); diff --git a/include/linux/random.h b/include/linux/random.h index b05856e..960803b 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -7,6 +7,7 @@ #define _LINUX_RANDOM_H #include +#include extern void add_device_randomness(const void *, unsigned int); extern void add_input_randomness(unsigned int type, unsigned int code, @@ -112,4 +113,23 @@ static inline u32 next_pseudo_random32(u32 seed) return seed * 1664525 + 1013904223; } +/* API for asynchronous in-kernel operation */ +struct random_work { + struct work_struct rw_work; + u8 *rw_buf; + ssize_t rw_len; + void *private; + void (*rw_cb)(void *buf, ssize_t buflen, + void *private); + bool cancel; +}; + +ssize_t get_blocking_random_bytes(void *buf, ssize_t nbytes, bool *cancel); +void get_blocking_random_bytes_cancel(struct random_work *rw); +void get_blocking_random_bytes_cb(struct workqueue_struct *wq, + struct random_work *rw, + u8 *buf, ssize_t nbytes, void *private, + void (*cb)(void *buf, ssize_t buflen, + void *private)); + #endif /* _LINUX_RANDOM_H */ -- 2.1.0