diff options
Diffstat (limited to 'drivers/crypto/atmel-sha204a.c')
| -rw-r--r-- | drivers/crypto/atmel-sha204a.c | 258 |
1 files changed, 258 insertions, 0 deletions
diff --git a/drivers/crypto/atmel-sha204a.c b/drivers/crypto/atmel-sha204a.c new file mode 100644 index 000000000..21a84c29c --- /dev/null +++ b/drivers/crypto/atmel-sha204a.c @@ -0,0 +1,258 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Microchip / Atmel SHA204A (I2C) driver. + * + * Copyright (c) 2019 Linaro, Ltd. <ard.biesheuvel@linaro.org> + */ + +#include <linux/delay.h> +#include <linux/device.h> +#include <linux/err.h> +#include <linux/errno.h> +#include <linux/i2c.h> +#include <linux/init.h> +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/scatterlist.h> +#include <linux/slab.h> +#include <linux/string.h> +#include <linux/sysfs.h> +#include <linux/workqueue.h> +#include "atmel-i2c.h" + +/* + * According to review by Bill Cox [1], the ATSHA204 has very low entropy. + * [1] https://www.metzdowd.com/pipermail/cryptography/2014-December/023858.html + */ +static const unsigned short atsha204_quality = 1; + +static void atmel_sha204a_rng_done(struct atmel_i2c_work_data *work_data, + void *areq, int status) +{ + struct atmel_i2c_client_priv *i2c_priv = work_data->ctx; + struct hwrng *rng = areq; + + if (status) { + dev_warn_ratelimited(&i2c_priv->client->dev, + "i2c transaction failed (%d)\n", + status); + kfree_sensitive(work_data); + atomic_dec(&i2c_priv->tfm_count); + return; + } + + rng->priv = (unsigned long)work_data; + atomic_dec(&i2c_priv->tfm_count); +} + +static int atmel_sha204a_rng_read_nonblocking(struct hwrng *rng, void *data, + size_t max) +{ + struct atmel_i2c_client_priv *i2c_priv; + struct atmel_i2c_work_data *work_data; + + i2c_priv = container_of(rng, struct atmel_i2c_client_priv, hwrng); + + /* keep maximum 1 asynchronous read in flight at any time */ + if (!atomic_add_unless(&i2c_priv->tfm_count, 1, 1)) + return 0; + + if (rng->priv) { + work_data = (struct atmel_i2c_work_data *)rng->priv; + max = min(RANDOM_RSP_SIZE - CMD_OVERHEAD_SIZE, max); + memcpy(data, &work_data->cmd.data[RSP_DATA_IDX], max); + rng->priv = 0; + } else { + work_data = kmalloc_obj(*work_data, GFP_ATOMIC); + if (!work_data) { + atomic_dec(&i2c_priv->tfm_count); + return -ENOMEM; + } + work_data->ctx = i2c_priv; + work_data->client = i2c_priv->client; + + max = 0; + } + + atmel_i2c_init_random_cmd(&work_data->cmd); + atmel_i2c_enqueue(work_data, atmel_sha204a_rng_done, rng); + + return max; +} + +static int atmel_sha204a_rng_read(struct hwrng *rng, void *data, size_t max, + bool wait) +{ + struct atmel_i2c_client_priv *i2c_priv; + struct atmel_i2c_cmd cmd; + int ret; + + if (!wait) + return atmel_sha204a_rng_read_nonblocking(rng, data, max); + + i2c_priv = container_of(rng, struct atmel_i2c_client_priv, hwrng); + + atmel_i2c_init_random_cmd(&cmd); + + ret = atmel_i2c_send_receive(i2c_priv->client, &cmd); + if (ret) + goto out; + + max = min(RANDOM_RSP_SIZE - CMD_OVERHEAD_SIZE, max); + memcpy(data, &cmd.data[RSP_DATA_IDX], max); + ret = max; + +out: + memzero_explicit(&cmd, sizeof(cmd)); + return ret; +} + +static int atmel_sha204a_otp_read(struct i2c_client *client, u16 addr, u8 *otp) +{ + struct atmel_i2c_cmd cmd; + int ret; + + ret = atmel_i2c_init_read_otp_cmd(&cmd, addr); + if (ret < 0) { + dev_err(&client->dev, "failed, invalid otp address %04X\n", + addr); + return ret; + } + + ret = atmel_i2c_send_receive(client, &cmd); + if (ret < 0) { + dev_err(&client->dev, "failed to read otp at %04X\n", addr); + return ret; + } + + if (cmd.data[0] == 0xff) { + dev_err(&client->dev, "failed, device not ready\n"); + return -EIO; + } + + memcpy(otp, cmd.data+1, 4); + + return ret; +} + +static ssize_t otp_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + u16 addr; + u8 otp[OTP_ZONE_SIZE]; + struct i2c_client *client = to_i2c_client(dev); + ssize_t len = 0; + int i, ret; + + for (addr = 0; addr < OTP_ZONE_SIZE / 4; addr++) { + ret = atmel_sha204a_otp_read(client, addr, otp + addr * 4); + if (ret < 0) { + dev_err(dev, "failed to read otp zone\n"); + return ret; + } + } + + for (i = 0; i < OTP_ZONE_SIZE; i++) + len += sysfs_emit_at(buf, len, "%02X", otp[i]); + len += sysfs_emit_at(buf, len, "\n"); + return len; +} +static DEVICE_ATTR_RO(otp); + +static struct attribute *atmel_sha204a_attrs[] = { + &dev_attr_otp.attr, + NULL +}; + +static const struct attribute_group atmel_sha204a_groups = { + .name = "atsha204a", + .attrs = atmel_sha204a_attrs, +}; + +static int atmel_sha204a_probe(struct i2c_client *client) +{ + struct atmel_i2c_client_priv *i2c_priv; + const unsigned short *quality; + int ret; + + ret = atmel_i2c_probe(client); + if (ret) + return ret; + + i2c_priv = i2c_get_clientdata(client); + + memset(&i2c_priv->hwrng, 0, sizeof(i2c_priv->hwrng)); + + i2c_priv->hwrng.name = dev_name(&client->dev); + i2c_priv->hwrng.read = atmel_sha204a_rng_read; + + quality = i2c_get_match_data(client); + if (quality) + i2c_priv->hwrng.quality = *quality; + + ret = devm_hwrng_register(&client->dev, &i2c_priv->hwrng); + if (ret) { + dev_err(&client->dev, "failed to register RNG (%d)\n", ret); + return ret; + } + + ret = sysfs_create_group(&client->dev.kobj, &atmel_sha204a_groups); + if (ret) { + dev_err(&client->dev, "failed to create sysfs group (%d)\n", ret); + return ret; + } + + return ret; +} + +static void atmel_sha204a_remove(struct i2c_client *client) +{ + struct atmel_i2c_client_priv *i2c_priv = i2c_get_clientdata(client); + + sysfs_remove_group(&client->dev.kobj, &atmel_sha204a_groups); + devm_hwrng_unregister(&client->dev, &i2c_priv->hwrng); + atmel_i2c_flush_queue(); + + kfree_sensitive((void *)i2c_priv->hwrng.priv); +} + +static const struct of_device_id atmel_sha204a_dt_ids[] = { + { .compatible = "atmel,atsha204" }, + { .compatible = "atmel,atsha204a" }, + { } +}; +MODULE_DEVICE_TABLE(of, atmel_sha204a_dt_ids); + +static const struct i2c_device_id atmel_sha204a_id[] = { + { .name = "atsha204", .driver_data = (kernel_ulong_t)&atsha204_quality }, + { .name = "atsha204a", .driver_data = (kernel_ulong_t)NULL }, + { } +}; +MODULE_DEVICE_TABLE(i2c, atmel_sha204a_id); + +static struct i2c_driver atmel_sha204a_driver = { + .probe = atmel_sha204a_probe, + .remove = atmel_sha204a_remove, + .id_table = atmel_sha204a_id, + + .driver.name = "atmel-sha204a", + .driver.of_match_table = atmel_sha204a_dt_ids, +}; + +static int __init atmel_sha204a_init(void) +{ + return i2c_add_driver(&atmel_sha204a_driver); +} + +static void __exit atmel_sha204a_exit(void) +{ + atmel_i2c_flush_queue(); + i2c_del_driver(&atmel_sha204a_driver); +} + +module_init(atmel_sha204a_init); +module_exit(atmel_sha204a_exit); + +MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>"); +MODULE_DESCRIPTION("Microchip / Atmel SHA204A (I2C) driver"); +MODULE_LICENSE("GPL v2"); |