[S390] zcrypt: add support for large random numbers

This patch allows user space applications to access large amounts of
truly random data. The random data source is the build-in hardware
random number generator on the CEX2C cards.

Signed-off-by: Ralph Wuerthner <rwuerthn@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>

3 files changed, 326 insertions, 1 deletions

diff --git a/drivers/s390/crypto/zcrypt_api.c b/drivers/s390/crypto/zcrypt_api.c
index e3625a47a596..b2740ff2e615 100644
--- a/drivers/s390/crypto/zcrypt_api.c
+++ b/drivers/s390/crypto/zcrypt_api.c
@@ -36,6 +36,7 @@
 #include <linux/compat.h>
 #include <asm/atomic.h>
 #include <asm/uaccess.h>
+#include <linux/hw_random.h>
 
 #include "zcrypt_api.h"
 
@@ -52,6 +53,9 @@ static LIST_HEAD(zcrypt_device_list);
 static int zcrypt_device_count = 0;
 static atomic_t zcrypt_open_count = ATOMIC_INIT(0);
 
+static int zcrypt_rng_device_add(void);
+static void zcrypt_rng_device_remove(void);
+
 /**
  * Device attributes common for all crypto devices.
  */
@@ -216,6 +220,22 @@ int zcrypt_device_register(struct zcrypt_device *zdev)
         __zcrypt_increase_preference(zdev);
         zcrypt_device_count++;
         spin_unlock_bh(&zcrypt_device_lock);
+        if (zdev->ops->rng) {
+                rc = zcrypt_rng_device_add();
+                if (rc)
+                        goto out_unregister;
+        }
+        return 0;
+
+out_unregister:
+        spin_lock_bh(&zcrypt_device_lock);
+        zcrypt_device_count--;
+        list_del_init(&zdev->list);
+        spin_unlock_bh(&zcrypt_device_lock);
+        sysfs_remove_group(&zdev->ap_dev->device.kobj,
+                           &zcrypt_device_attr_group);
+        put_device(&zdev->ap_dev->device);
+        zcrypt_device_put(zdev);
 out:
         return rc;
 }
@@ -226,6 +246,8 @@ EXPORT_SYMBOL(zcrypt_device_register);
  */
 void zcrypt_device_unregister(struct zcrypt_device *zdev)
 {
+        if (zdev->ops->rng)
+                zcrypt_rng_device_remove();
         spin_lock_bh(&zcrypt_device_lock);
         zcrypt_device_count--;
         list_del_init(&zdev->list);
@@ -427,6 +449,37 @@ static long zcrypt_send_cprb(struct ica_xcRB *xcRB)
         return -ENODEV;
 }
 
+static long zcrypt_rng(char *buffer)
+{
+        struct zcrypt_device *zdev;
+        int rc;
+
+        spin_lock_bh(&zcrypt_device_lock);
+        list_for_each_entry(zdev, &zcrypt_device_list, list) {
+                if (!zdev->online || !zdev->ops->rng)
+                        continue;
+                zcrypt_device_get(zdev);
+                get_device(&zdev->ap_dev->device);
+                zdev->request_count++;
+                __zcrypt_decrease_preference(zdev);
+                if (try_module_get(zdev->ap_dev->drv->driver.owner)) {
+                        spin_unlock_bh(&zcrypt_device_lock);
+                        rc = zdev->ops->rng(zdev, buffer);
+                        spin_lock_bh(&zcrypt_device_lock);
+                        module_put(zdev->ap_dev->drv->driver.owner);
+                } else
+                        rc = -EAGAIN;
+                zdev->request_count--;
+                __zcrypt_increase_preference(zdev);
+                put_device(&zdev->ap_dev->device);
+                zcrypt_device_put(zdev);
+                spin_unlock_bh(&zcrypt_device_lock);
+                return rc;
+        }
+        spin_unlock_bh(&zcrypt_device_lock);
+        return -ENODEV;
+}
+
 static void zcrypt_status_mask(char status[AP_DEVICES])
 {
         struct zcrypt_device *zdev;
@@ -1041,6 +1094,73 @@ out:
         return count;
 }
 
+static int zcrypt_rng_device_count;
+static u32 *zcrypt_rng_buffer;
+static int zcrypt_rng_buffer_index;
+static DEFINE_MUTEX(zcrypt_rng_mutex);
+
+static int zcrypt_rng_data_read(struct hwrng *rng, u32 *data)
+{
+        int rc;
+
+        /**
+         * We don't need locking here because the RNG API guarantees serialized
+         * read method calls.
+         */
+        if (zcrypt_rng_buffer_index == 0) {
+                rc = zcrypt_rng((char *) zcrypt_rng_buffer);
+                if (rc < 0)
+                        return -EIO;
+                zcrypt_rng_buffer_index = rc / sizeof *data;
+        }
+        *data = zcrypt_rng_buffer[--zcrypt_rng_buffer_index];
+        return sizeof *data;
+}
+
+static struct hwrng zcrypt_rng_dev = {
+        .name           = "zcrypt",
+        .data_read      = zcrypt_rng_data_read,
+};
+
+static int zcrypt_rng_device_add(void)
+{
+        int rc = 0;
+
+        mutex_lock(&zcrypt_rng_mutex);
+        if (zcrypt_rng_device_count == 0) {
+                zcrypt_rng_buffer = (u32 *) get_zeroed_page(GFP_KERNEL);
+                if (!zcrypt_rng_buffer) {
+                        rc = -ENOMEM;
+                        goto out;
+                }
+                zcrypt_rng_buffer_index = 0;
+                rc = hwrng_register(&zcrypt_rng_dev);
+                if (rc)
+                        goto out_free;
+                zcrypt_rng_device_count = 1;
+        } else
+                zcrypt_rng_device_count++;
+        mutex_unlock(&zcrypt_rng_mutex);
+        return 0;
+
+out_free:
+        free_page((unsigned long) zcrypt_rng_buffer);
+out:
+        mutex_unlock(&zcrypt_rng_mutex);
+        return rc;
+}
+
+static void zcrypt_rng_device_remove(void)
+{
+        mutex_lock(&zcrypt_rng_mutex);
+        zcrypt_rng_device_count--;
+        if (zcrypt_rng_device_count == 0) {
+                hwrng_unregister(&zcrypt_rng_dev);
+                free_page((unsigned long) zcrypt_rng_buffer);
+        }
+        mutex_unlock(&zcrypt_rng_mutex);
+}
+
 /**
  * The module initialization code.
  */
diff --git a/drivers/s390/crypto/zcrypt_api.h b/drivers/s390/crypto/zcrypt_api.h
index de4877ee618f..0e948528a73a 100644
--- a/drivers/s390/crypto/zcrypt_api.h
+++ b/drivers/s390/crypto/zcrypt_api.h
@@ -100,6 +100,13 @@ struct ica_z90_status {
 #define ZCRYPT_CEX2C            5
 #define ZCRYPT_CEX2A            6
 
+/**
+ * Large random numbers are pulled in 4096 byte chunks from the crypto cards
+ * and stored in a page. Be carefull when increasing this buffer due to size
+ * limitations for AP requests.
+ */
+#define ZCRYPT_RNG_BUFFER_SIZE  4096
+
 struct zcrypt_device;
 
 struct zcrypt_ops {
@@ -107,6 +114,7 @@ struct zcrypt_ops {
         long (*rsa_modexpo_crt)(struct zcrypt_device *,
                                 struct ica_rsa_modexpo_crt *);
         long (*send_cprb)(struct zcrypt_device *, struct ica_xcRB *);
+        long (*rng)(struct zcrypt_device *, char *);
 };
 
 struct zcrypt_device {
diff --git a/drivers/s390/crypto/zcrypt_pcixcc.c b/drivers/s390/crypto/zcrypt_pcixcc.c
index 70b9ddc8cf9d..3674bfa82b65 100644
--- a/drivers/s390/crypto/zcrypt_pcixcc.c
+++ b/drivers/s390/crypto/zcrypt_pcixcc.c
@@ -356,6 +356,55 @@ static int XCRB_msg_to_type6CPRB_msgX(struct zcrypt_device *zdev,
 }
 
 /**
+ * Prepare a type6 CPRB message for random number generation
+ *
+ * @ap_dev: AP device pointer
+ * @ap_msg: pointer to AP message
+ */
+static void rng_type6CPRB_msgX(struct ap_device *ap_dev,
+                               struct ap_message *ap_msg,
+                               unsigned random_number_length)
+{
+        struct {
+                struct type6_hdr hdr;
+                struct CPRBX cprbx;
+                char function_code[2];
+                short int rule_length;
+                char rule[8];
+                short int verb_length;
+                short int key_length;
+        } __attribute__((packed)) *msg = ap_msg->message;
+        static struct type6_hdr static_type6_hdrX = {
+                .type           = 0x06,
+                .offset1        = 0x00000058,
+                .agent_id       = {'C', 'A'},
+                .function_code  = {'R', 'L'},
+                .ToCardLen1     = sizeof *msg - sizeof(msg->hdr),
+                .FromCardLen1   = sizeof *msg - sizeof(msg->hdr),
+        };
+        static struct CPRBX static_cprbx = {
+                .cprb_len       = 0x00dc,
+                .cprb_ver_id    = 0x02,
+                .func_id        = {0x54, 0x32},
+                .req_parml      = sizeof *msg - sizeof(msg->hdr) -
+                                  sizeof(msg->cprbx),
+                .rpl_msgbl      = sizeof *msg - sizeof(msg->hdr),
+        };
+
+        msg->hdr = static_type6_hdrX;
+        msg->hdr.FromCardLen2 = random_number_length,
+        msg->cprbx = static_cprbx;
+        msg->cprbx.rpl_datal = random_number_length,
+        msg->cprbx.domain = AP_QID_QUEUE(ap_dev->qid);
+        memcpy(msg->function_code, msg->hdr.function_code, 0x02);
+        msg->rule_length = 0x0a;
+        memcpy(msg->rule, "RANDOM  ", 8);
+        msg->verb_length = 0x02;
+        msg->key_length = 0x02;
+        ap_msg->length = sizeof *msg;
+}
+
+/**
  * Copy results from a type 86 ICA reply message back to user space.
  *
  * @zdev: crypto device pointer
@@ -509,6 +558,26 @@ static int convert_type86_xcrb(struct zcrypt_device *zdev,
         return 0;
 }
 
+static int convert_type86_rng(struct zcrypt_device *zdev,
+                          struct ap_message *reply,
+                          char *buffer)
+{
+        struct {
+                struct type86_hdr hdr;
+                struct type86_fmt2_ext fmt2;
+                struct CPRBX cprbx;
+        } __attribute__((packed)) *msg = reply->message;
+        char *data = reply->message;
+
+        if (msg->cprbx.ccp_rtcode != 0 || msg->cprbx.ccp_rscode != 0) {
+                PDEBUG("RNG response error on PCIXCC/CEX2C rc=%hu/rs=%hu\n",
+                       rc, rs);
+                return -EINVAL;
+        }
+        memcpy(buffer, data + msg->fmt2.offset2, msg->fmt2.count2);
+        return msg->fmt2.count2;
+}
+
 static int convert_response_ica(struct zcrypt_device *zdev,
                             struct ap_message *reply,
                             char __user *outputdata,
@@ -567,6 +636,31 @@ static int convert_response_xcrb(struct zcrypt_device *zdev,
         }
 }
 
+static int convert_response_rng(struct zcrypt_device *zdev,
+                                 struct ap_message *reply,
+                                 char *data)
+{
+        struct type86x_reply *msg = reply->message;
+
+        switch (msg->hdr.type) {
+        case TYPE82_RSP_CODE:
+        case TYPE88_RSP_CODE:
+                return -EINVAL;
+        case TYPE86_RSP_CODE:
+                if (msg->hdr.reply_code)
+                        return -EINVAL;
+                if (msg->cprbx.cprb_ver_id == 0x02)
+                        return convert_type86_rng(zdev, reply, data);
+                /* no break, incorrect cprb version is an unknown response */
+        default: /* Unknown response type, this should NEVER EVER happen */
+                PRINTK("Unrecognized Message Header: %08x%08x\n",
+                       *(unsigned int *) reply->message,
+                       *(unsigned int *) (reply->message+4));
+                zdev->online = 0;
+                return -EAGAIN; /* repeat the request on a different device. */
+        }
+}
+
 /**
  * This function is called from the AP bus code after a crypto request
  * "msg" has finished with the reply message "reply".
@@ -736,6 +830,42 @@ out_free:
 }
 
 /**
+ * The request distributor calls this function if it picked the PCIXCC/CEX2C
+ * device to generate random data.
+ * @zdev: pointer to zcrypt_device structure that identifies the
+ *        PCIXCC/CEX2C device to the request distributor
+ * @buffer: pointer to a memory page to return random data
+ */
+
+static long zcrypt_pcixcc_rng(struct zcrypt_device *zdev,
+                                    char *buffer)
+{
+        struct ap_message ap_msg;
+        struct response_type resp_type = {
+                .type = PCIXCC_RESPONSE_TYPE_XCRB,
+        };
+        int rc;
+
+        ap_msg.message = kmalloc(PCIXCC_MAX_XCRB_MESSAGE_SIZE, GFP_KERNEL);
+        if (!ap_msg.message)
+                return -ENOMEM;
+        ap_msg.psmid = (((unsigned long long) current->pid) << 32) +
+                                atomic_inc_return(&zcrypt_step);
+        ap_msg.private = &resp_type;
+        rng_type6CPRB_msgX(zdev->ap_dev, &ap_msg, ZCRYPT_RNG_BUFFER_SIZE);
+        init_completion(&resp_type.work);
+        ap_queue_message(zdev->ap_dev, &ap_msg);
+        rc = wait_for_completion_interruptible(&resp_type.work);
+        if (rc == 0)
+                rc = convert_response_rng(zdev, &ap_msg, buffer);
+        else
+                /* Signal pending. */
+                ap_cancel_message(zdev->ap_dev, &ap_msg);
+        kfree(ap_msg.message);
+        return rc;
+}
+
+/**
  * The crypto operations for a PCIXCC/CEX2C card.
  */
 static struct zcrypt_ops zcrypt_pcixcc_ops = {
@@ -744,6 +874,13 @@ static struct zcrypt_ops zcrypt_pcixcc_ops = {
         .send_cprb = zcrypt_pcixcc_send_cprb,
 };
 
+static struct zcrypt_ops zcrypt_pcixcc_with_rng_ops = {
+        .rsa_modexpo = zcrypt_pcixcc_modexpo,
+        .rsa_modexpo_crt = zcrypt_pcixcc_modexpo_crt,
+        .send_cprb = zcrypt_pcixcc_send_cprb,
+        .rng = zcrypt_pcixcc_rng,
+};
+
 /**
  * Micro-code detection function. Its sends a message to a pcixcc card
  * to find out the microcode level.
@@ -859,6 +996,58 @@ out_free:
 }
 
 /**
+ * Large random number detection function. Its sends a message to a pcixcc
+ * card to find out if large random numbers are supported.
+ * @ap_dev: pointer to the AP device.
+ *
+ * Returns 1 if large random numbers are supported, 0 if not and < 0 on error.
+ */
+static int zcrypt_pcixcc_rng_supported(struct ap_device *ap_dev)
+{
+        struct ap_message ap_msg;
+        unsigned long long psmid;
+        struct {
+                struct type86_hdr hdr;
+                struct type86_fmt2_ext fmt2;
+                struct CPRBX cprbx;
+        } __attribute__((packed)) *reply;
+        int rc, i;
+
+        ap_msg.message = (void *) get_zeroed_page(GFP_KERNEL);
+        if (!ap_msg.message)
+                return -ENOMEM;
+
+        rng_type6CPRB_msgX(ap_dev, &ap_msg, 4);
+        rc = ap_send(ap_dev->qid, 0x0102030405060708ULL, ap_msg.message,
+                     ap_msg.length);
+        if (rc)
+                goto out_free;
+
+        /* Wait for the test message to complete. */
+        for (i = 0; i < 2 * HZ; i++) {
+                msleep(1000 / HZ);
+                rc = ap_recv(ap_dev->qid, &psmid, ap_msg.message, 4096);
+                if (rc == 0 && psmid == 0x0102030405060708ULL)
+                        break;
+        }
+
+        if (i >= 2 * HZ) {
+                /* Got no answer. */
+                rc = -ENODEV;
+                goto out_free;
+        }
+
+        reply = ap_msg.message;
+        if (reply->cprbx.ccp_rtcode == 0 && reply->cprbx.ccp_rscode == 0)
+                rc = 1;
+        else
+                rc = 0;
+out_free:
+        free_page((unsigned long) ap_msg.message);
+        return rc;
+}
+
+/**
  * Probe function for PCIXCC/CEX2C cards. It always accepts the AP device
  * since the bus_match already checked the hardware type. The PCIXCC
  * cards come in two flavours: micro code level 2 and micro code level 3.
@@ -874,7 +1063,6 @@ static int zcrypt_pcixcc_probe(struct ap_device *ap_dev)
         if (!zdev)
                 return -ENOMEM;
         zdev->ap_dev = ap_dev;
-        zdev->ops = &zcrypt_pcixcc_ops;
         zdev->online = 1;
         if (ap_dev->device_type == AP_DEVICE_TYPE_PCIXCC) {
                 rc = zcrypt_pcixcc_mcl(ap_dev);
@@ -901,6 +1089,15 @@ static int zcrypt_pcixcc_probe(struct ap_device *ap_dev)
                 zdev->min_mod_size = PCIXCC_MIN_MOD_SIZE;
                 zdev->max_mod_size = PCIXCC_MAX_MOD_SIZE;
         }
+        rc = zcrypt_pcixcc_rng_supported(ap_dev);
+        if (rc < 0) {
+                zcrypt_device_free(zdev);
+                return rc;
+        }
+        if (rc)
+                zdev->ops = &zcrypt_pcixcc_with_rng_ops;
+        else
+                zdev->ops = &zcrypt_pcixcc_ops;
         ap_dev->reply = &zdev->reply;
         ap_dev->private = zdev;
         rc = zcrypt_device_register(zdev);