RE: [EXT] Re: [PATCH v7 5/5] firmware: imx: adds miscdev

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-----Original Message-----
From: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx> 
Sent: Monday, September 9, 2024 5:52 PM
To: Pankaj Gupta <pankaj.gupta@xxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>; Rob Herring <robh@xxxxxxxxxx>;
Krzysztof Kozlowski <krzk+dt@xxxxxxxxxx>; Conor Dooley
<conor+dt@xxxxxxxxxx>; Shawn Guo <shawnguo@xxxxxxxxxx>; Pengutronix Kernel
Team <kernel@xxxxxxxxxxxxxx>; Fabio Estevam <festevam@xxxxxxxxx>; Rob
Herring <robh+dt@xxxxxxxxxx>; linux-doc@xxxxxxxxxxxxxxx;
linux-kernel@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx;
imx@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Subject: [EXT] Re: [PATCH v7 5/5] firmware: imx: adds miscdev

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On Wed, Sep 04, 2024 at 04:21:21PM +0530, Pankaj Gupta wrote:
> Adds the driver for communication interface to secure-enclave, for 
> exchanging messages with NXP secure enclave HW IP(s) like EdgeLock 
> Enclave from:
> - User-Space Applications via character driver.
>
> ABI documentation for the NXP secure-enclave driver.
>
> User-space library using this driver:
> - i.MX Secure Enclave library:
>   -- URL: 
> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgith
> ub.com%2Fnxp-imx%2Fimx-secure-enclave.git&data=05%7C02%7Cpankaj.gupta%
> 40nxp.com%7Ca61c8211ef7548dfde0008dcd0ca0bec%7C686ea1d3bc2b4c6fa92cd99
> c5c301635%7C0%7C0%7C638614813421798949%7CUnknown%7CTWFpbGZsb3d8eyJWIjo
> iMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%
> 7C&sdata=DQ2%2Fv%2BuCZRlBD4xHiKwGOnicwv84g6rXZ2j%2BjMolt%2FE%3D&reserv
> ed=0,
> - i.MX Secure Middle-Ware:
>   -- URL: 
> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgith
> ub.com%2Fnxp-imx%2Fimx-smw.git&data=05%7C02%7Cpankaj.gupta%40nxp.com%7
> Ca61c8211ef7548dfde0008dcd0ca0bec%7C686ea1d3bc2b4c6fa92cd99c5c301635%7
> C0%7C0%7C638614813421814882%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMD
> AiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=TL
> 3gmQWdzNkseInz3DQ%2B4eOO1iMpgD8QYIldXIaKIgA%3D&reserved=0
>
> Signed-off-by: Pankaj Gupta <pankaj.gupta@xxxxxxx>
> ---
>  Documentation/ABI/testing/se-cdev   |  43 ++
>  drivers/firmware/imx/ele_base_msg.c |   8 +-
>  drivers/firmware/imx/ele_common.c   |  36 +-
>  drivers/firmware/imx/ele_common.h   |   6 +-
>  drivers/firmware/imx/se_ctrl.c      | 790
++++++++++++++++++++++++++++++++++++
>  drivers/firmware/imx/se_ctrl.h      |  52 +++
>  include/uapi/linux/se_ioctl.h       |  94 +++++
>  7 files changed, 1010 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/firmware/imx/ele_base_msg.c 
> b/drivers/firmware/imx/ele_base_msg.c
> index e3e570a25e85..ae200ce64100 100644
> --- a/drivers/firmware/imx/ele_base_msg.c
> +++ b/drivers/firmware/imx/ele_base_msg.c
> @@ -68,7 +68,7 @@ int ele_get_info(struct device *dev, struct ele_dev_info
*s_info)
>       tx_msg->data[0] = upper_32_bits(get_info_addr);
>       tx_msg->data[1] = lower_32_bits(get_info_addr);
>       tx_msg->data[2] = sizeof(*s_info);
> -     ret = ele_msg_send_rcv(priv,
> +     ret = ele_msg_send_rcv(priv->priv_dev_ctx,
>                              tx_msg,
>                              ELE_GET_INFO_REQ_MSG_SZ,
>                              rx_msg,
> @@ -150,7 +150,7 @@ int ele_ping(struct device *dev)
>               goto exit;
>       }
>
> -     ret = ele_msg_send_rcv(priv,
> +     ret = ele_msg_send_rcv(priv->priv_dev_ctx,
>                              tx_msg,
>                              ELE_PING_REQ_SZ,
>                              rx_msg,
> @@ -206,7 +206,7 @@ int ele_service_swap(struct device *dev,
>       tx_msg->data[3] = lower_32_bits(addr);
>       tx_msg->data[4] = se_add_msg_crc((uint32_t *)&tx_msg[0],
>
ELE_SERVICE_SWAP_REQ_MSG_SZ);
> -     ret = ele_msg_send_rcv(priv,
> +     ret = ele_msg_send_rcv(priv->priv_dev_ctx,
>                              tx_msg,
>                              ELE_SERVICE_SWAP_REQ_MSG_SZ,
>                              rx_msg,
> @@ -268,7 +268,7 @@ int ele_fw_authenticate(struct device *dev,
phys_addr_t addr)
>       tx_msg->data[0] = lower_32_bits(addr);
>       tx_msg->data[2] = addr;
>
> -     ret = ele_msg_send_rcv(priv,
> +     ret = ele_msg_send_rcv(priv->priv_dev_ctx,
>                              tx_msg,
>                              ELE_FW_AUTH_REQ_SZ,
>                              rx_msg,
> diff --git a/drivers/firmware/imx/ele_common.c 
> b/drivers/firmware/imx/ele_common.c
> index a06d7015d3f1..9114c3594567 100644
> --- a/drivers/firmware/imx/ele_common.c
> +++ b/drivers/firmware/imx/ele_common.c
> @@ -18,16 +18,18 @@ u32 se_add_msg_crc(u32 *msg, u32 msg_len)
>       return crc;
>  }
>
> -int ele_msg_rcv(struct se_if_priv *priv,
> +int ele_msg_rcv(struct se_if_device_ctx *dev_ctx,
>               struct se_clbk_handle *se_clbk_hdl)  {
> +     struct se_if_priv *priv = dev_ctx->priv;
>       int err = 0;
>
>       err = wait_event_interruptible(se_clbk_hdl->wq,
>
atomic_read(&se_clbk_hdl->pending_hdr) != 0);
>       if (err < 0)
>               dev_err(priv->dev,
> -                     "Err[0x%x]:Interrupted by signal.\n",
> +                     "%s: Err[0x%x]:Interrupted by signal.\n",
> +                     se_clbk_hdl->dev_ctx->devname,
>                       err);
>       else
>               err = se_clbk_hdl->rx_msg_sz; @@ -37,10 +39,11 @@ int 
> ele_msg_rcv(struct se_if_priv *priv,
>       return err;
>  }
>
> -int ele_msg_send(struct se_if_priv *priv,
> +int ele_msg_send(struct se_if_device_ctx *dev_ctx,
>                void *tx_msg,
>                int tx_msg_sz)
>  {
> +     struct se_if_priv *priv = dev_ctx->priv;
>       struct se_msg_hdr *header;
>       int err;
>
> @@ -53,7 +56,8 @@ int ele_msg_send(struct se_if_priv *priv,
>       if (header->size << 2 != tx_msg_sz) {
>               err = -EINVAL;
>               dev_err(priv->dev,
> -                     "User buf hdr: 0x%x, sz mismatced with input-sz (%d
!= %d).",
> +                     "%s: User buf hdr: 0x%x, sz mismatced with input-sz
(%d != %d).",
> +                     dev_ctx->devname,
>                       *(u32 *)header,
>                       header->size << 2, tx_msg_sz);
>               goto exit;
> @@ -62,7 +66,9 @@ int ele_msg_send(struct se_if_priv *priv,
>
>       err = mbox_send_message(priv->tx_chan, tx_msg);
>       if (err < 0) {
> -             dev_err(priv->dev, "Error: mbox_send_message failure.\n");
> +             dev_err(priv->dev,
> +                     "%s: Error: mbox_send_message failure.",
> +                     dev_ctx->devname);
>               return err;
>       }
>       err = tx_msg_sz;
> @@ -72,24 +78,26 @@ int ele_msg_send(struct se_if_priv *priv,  }
>
>  /* API used for send/receive blocking call. */ -int 
> ele_msg_send_rcv(struct se_if_priv *priv,
> +int ele_msg_send_rcv(struct se_if_device_ctx *dev_ctx,

> You are heavily patching a file you introduced just in the last patch.
[PG] There is no new file introduced in the whole patch-set series.

> It seems you have messed up while rebasing. Please cleanup.
[PG] Instead of " struct se_if_priv *priv" in 4/5, I have used " struct
se_if_device_ctx *dev_ctx", to have
Device-name printed.

> +static int se_ioctl_cmd_snd_rcv_rsp_handler(struct se_if_device_ctx
*dev_ctx,
> +                                         u64 arg) {
> +     struct se_if_priv *priv = dev_ctx->priv;
> +     struct se_ioctl_cmd_snd_rcv_rsp_info cmd_snd_rcv_rsp_info;
> +     struct se_api_msg *tx_msg __free(kfree) = NULL;
> +     struct se_api_msg *rx_msg __free(kfree) = NULL;
> +     int err = 0;
> +
> +     if (down_interruptible(&dev_ctx->fops_lock))
> +             return -EBUSY;
> +
> +     if (dev_ctx->status != SE_IF_CTX_OPENED) {
> +             err = -EINVAL;
> +             goto exit;
> +     }

> You don't need this. Just trust Linux that it won't call your
ioctl/read/write ops when the device is not opened.
Ok will remove this in V8.

> +
> +     if (copy_from_user(&cmd_snd_rcv_rsp_info, (u8 *)arg,
> +                        sizeof(cmd_snd_rcv_rsp_info))) {
> +             dev_err(dev_ctx->priv->dev,

> You have priv as a variable already, please use it throughout this
function.
Ok. Will correct this at every places in V8.

> +static ssize_t se_if_fops_read(struct file *fp, char __user *buf,
> +                            size_t size, loff_t *ppos) {
> +     struct se_if_device_ctx *dev_ctx = fp->private_data;
> +     struct se_if_priv *priv = dev_ctx->priv;
> +     int err;
> +
> +     dev_dbg(priv->dev,
> +             "%s: read to buf %p(%zu), ppos=%lld\n",
> +                     dev_ctx->miscdev.name,
> +                     buf, size, ((ppos) ? *ppos : 0));
> +
> +     if (down_interruptible(&dev_ctx->fops_lock))
> +             return -EBUSY;
> +
> +     if (dev_ctx->status != SE_IF_CTX_OPENED) {
> +             err = -EINVAL;
> +             goto exit;
> +     }
> +
> +     if (dev_ctx != priv->cmd_receiver_clbk_hdl.dev_ctx) {
> +             err = -EINVAL;
> +             goto exit;
> +     }
> +
> +     err = ele_msg_rcv(dev_ctx, &priv->cmd_receiver_clbk_hdl);
> +     if (err < 0) {
> +             dev_err(dev_ctx->priv->dev,
> +                             "%s: Err[0x%x]:Interrupted by signal.\n",
> +                             dev_ctx->devname, err);
> +             dev_err(dev_ctx->priv->dev,
> +                             "Current active dev-ctx count = %d.\n",
> +                             dev_ctx->priv->active_devctx_count);

> active_devctx_count is never used except for printing this message.
> I don't think it provides meaningful information for userspace. Just dorp
it.
[PG] Like to maintain the count of active dev_context. This will be later
useful for debugging and in case of suspend/resume scenarios.


> +     dma_free_coherent(priv->dev, MAX_DATA_SIZE_PER_USER,
> +                       se_shared_mem_mgmt->non_secure_mem.ptr,
> +                       se_shared_mem_mgmt->non_secure_mem.dma_addr);
> +
> +     se_shared_mem_mgmt->non_secure_mem.ptr = NULL;
> +     se_shared_mem_mgmt->non_secure_mem.dma_addr = 0;
> +     se_shared_mem_mgmt->non_secure_mem.size = 0;
> +     se_shared_mem_mgmt->non_secure_mem.pos = 0; }
> +
> +/* Need to copy the output data to user-device context.
> + */
> +int se_dev_ctx_cpy_out_data(struct se_shared_mem_mgmt_info 
> +*se_shared_mem_mgmt)

> Only used in this file. Make it static.
Ok. Accepted will correct in V8.

> +{
> +     struct se_if_device_ctx *dev_ctx = container_of(se_shared_mem_mgmt,
> +                                                     typeof(*dev_ctx),
> +                                                     
> +se_shared_mem_mgmt);

> This function is only ever called like:

> se_dev_ctx_cpy_out_data(&dev_ctx->se_shared_mem_mgmt);

> Instead of this back and forth you could pass a struct se_if_device_ctx *
directly.

Accepted. Will correct in V8.

> +static int add_b_desc_to_pending_list(void *shared_ptr_with_pos,
> +                            struct se_ioctl_setup_iobuf *io,
> +                            struct se_shared_mem_mgmt_info 
> +*se_shared_mem_mgmt) {
> +     struct se_buf_desc *b_desc = NULL;
> +
> +     b_desc = kzalloc(sizeof(*b_desc), GFP_KERNEL);
> +     if (!b_desc)
> +             return -ENOMEM;
> +
> +     if (b_desc) {

> b_desc is not NULL here.
Will correct this in V8.

> +             b_desc->shared_buf_ptr = shared_ptr_with_pos;
> +             b_desc->usr_buf_ptr = io->user_buf;
> +             b_desc->size = io->length;
> +
> +             if (io->flags & SE_IO_BUF_FLAGS_IS_INPUT) {
> +                     /*
> +                      * buffer is input:
> +                      * add an entry in the "pending input buffers" list
so
> +                      * that copied data can be cleaned from shared
memory
> +                      * later.
> +                      */
> +                     list_add_tail(&b_desc->link,
&se_shared_mem_mgmt->pending_in);
> +             } else {
> +                     /*
> +                      * buffer is output:
> +                      * add an entry in the "pending out buffers" list so
data
> +                      * can be copied to user space when receiving
Secure-Enclave
> +                      * response.
> +                      */
> +                     list_add_tail(&b_desc->link,
&se_shared_mem_mgmt->pending_out);
> +             }
> +     }
> +
> +
> +     return 0;
> +}
> +
> +/* Open a character device. */
> +static int se_if_fops_open(struct inode *nd, struct file *fp) {
> +     struct se_if_device_ctx *dev_ctx = container_of(fp->private_data,
> +                                                     struct
se_if_device_ctx,
> +                                                     miscdev);
> +     struct se_if_priv *priv = dev_ctx->priv;
> +     int err = 0;
> +
> +     priv->dev_ctx_mono_count++;
> +     err = init_device_context(priv,
> +                               priv->dev_ctx_mono_count ?
> +                                     priv->dev_ctx_mono_count
> +                                     : priv->dev_ctx_mono_count++,

> priv->dev_ctx_mono_count won't be 0 here as you just increased it.
[PG] In case it got wrap around to zero, then to avoid it open a device with
name appended with zero, hence incrementing it. 

> +                               &dev_ctx);
> +     if (err) {
> +             dev_err(priv->dev,
> +                     "Failed[0x%x] to create device contexts.\n",
> +                     err);
> +             goto exit;
> +     }
> +
> +     dev_ctx->status = SE_IF_CTX_OPENED;
> +
> +     fp->private_data = dev_ctx;
> +
> +exit:
> +     up(&dev_ctx->fops_lock);

> You never acquired this semaphore which is likely not what you want.
[PG] Agree. Will fix it in v8.

> +     return err;
> +}
> +
> +/* Close a character device. */
> +static int se_if_fops_close(struct inode *nd, struct file *fp) {
> +     struct se_if_device_ctx *dev_ctx = fp->private_data;
> +     struct se_if_priv *priv = dev_ctx->priv;
> +
> +     /* Avoid race if closed at the same time */
> +     if (down_trylock(&dev_ctx->fops_lock))
> +             return -EBUSY;
> +
> +     /* The device context has not been opened */
> +     if (dev_ctx->status != SE_IF_CTX_OPENED)
> +             goto exit;
> +
> +     /* check if this device was registered as command receiver. */
> +     if (priv->cmd_receiver_clbk_hdl.dev_ctx == dev_ctx) {

> This is racy. priv->cmd_receiver_clbk_hdl can be accessed by multiple
tasks without locking.

It is not accessed by multiple task. It is slave to the FW.
The "cmd_receiver_clbk_hdl.dev_ctx" can be only one per 'priv'.
This is accessed by Callback function only, to receive any command from FW. 
Not more than one such device, allowed to be opened.

> +             priv->cmd_receiver_clbk_hdl.dev_ctx = NULL;
> +             kfree(priv->cmd_receiver_clbk_hdl.rx_msg);
> +             priv->cmd_receiver_clbk_hdl.rx_msg = NULL;
> +             atomic_set(&priv->cmd_receiver_clbk_hdl.pending_hdr, 0);
> +     }
> +
> +     /* check if this device was registered as waiting response. */
> +     if (priv->waiting_rsp_clbk_hdl.dev_ctx == dev_ctx) {

> +             priv->waiting_rsp_clbk_hdl.dev_ctx = NULL;
> +             mutex_unlock(&priv->se_if_cmd_lock);

> This mutex will never be locked here. 

Accepted will correct in V8.

> +     }
> +
> +     se_dev_ctx_shared_mem_cleanup(&dev_ctx->se_shared_mem_mgmt);
> +     cleanup_se_shared_mem(&dev_ctx->se_shared_mem_mgmt);
> +     dev_ctx->status = SE_IF_CTX_FREE;
> +
> +     priv->active_devctx_count--;
> +     list_del(&dev_ctx->link);
> +exit:
> +     up(&dev_ctx->fops_lock);
> +     kfree(dev_ctx->devname);
> +     kfree(dev_ctx);
> +
> +     return 0;
> +}
> +
>  static void se_if_probe_cleanup(struct platform_device *pdev)  {
> +     struct se_if_device_ctx *dev_ctx, *t_dev_ctx;
>       struct device *dev = &pdev->dev;
>       struct se_if_priv *priv;
>
> @@ -247,6 +939,14 @@ static void se_if_probe_cleanup(struct
platform_device *pdev)
>               priv->imem.buf = NULL;
>       }
>
> +     list_for_each_entry_safe(dev_ctx, t_dev_ctx, &priv->dev_ctx_list,
link) {
> +             list_del(&dev_ctx->link);
> +             priv->active_devctx_count--;
> +     }

> The only place where this list is ever iterated over is here.
active_devctx_count is never used except for printing a message (see other
comment).
> Just drop this list.

Like to keep the active_devctx_count, for debugging the stale dev_ctx in the
system.
Will replace the dev_err with dev_dbg.

> +
> +     devm_remove_action(dev, if_misc_deregister,
&priv->priv_dev_ctx->miscdev);
> +     misc_deregister(&priv->priv_dev_ctx->miscdev);
> +
>       /* No need to check, if reserved memory is allocated
>        * before calling for its release. Or clearing the
>        * un-set bit.
> @@ -254,6 +954,87 @@ static void se_if_probe_cleanup(struct
platform_device *pdev)
>       of_reserved_mem_device_release(dev);
>  }
>
> +int init_device_context(struct se_if_priv *priv, int ch_id,
> +                     struct se_if_device_ctx **new_dev_ctx) {

> static.
Will remove it in V8.

> +     const struct se_if_node_info *info = priv->info;
> +     struct se_if_device_ctx *dev_ctx;
> +     int ret = 0;
> +
> +     if (ch_id)
> +             dev_ctx = kzalloc(sizeof(*dev_ctx), GFP_KERNEL);
> +     else
> +             dev_ctx = devm_kzalloc(priv->dev, sizeof(*dev_ctx), 
> + GFP_KERNEL);
> +
> +     if (!dev_ctx) {
> +             ret = -ENOMEM;
> +             return ret;
> +     }
> +
> +     dev_ctx->status = SE_IF_CTX_FREE;
> +     dev_ctx->priv = priv;
> +
> +     if (ch_id)
> +             dev_ctx->devname = kasprintf(GFP_KERNEL, "%s_ch%d",
> +                                          info->se_name, ch_id);
> +     else
> +             dev_ctx->devname = devm_kasprintf(priv->dev,
> +                                               GFP_KERNEL, "%s_ch%d",
> +                                               info->se_name, ch_id);
> +     if (!dev_ctx->devname) {
> +             ret = -ENOMEM;
> +             if (ch_id)
> +                     kfree(dev_ctx);
> +
> +             return ret;
> +     }
> +
> +     sema_init(&dev_ctx->fops_lock, 1);


> This semaphore only counts up to one in your code which basically makes it
a mutex. Just use a mutex instead.
Accepted. Will change in V8.


> +/* Private struct for each char device instance. */ struct 
> +se_if_device_ctx {
> +     struct se_if_priv *priv;
> +     struct miscdevice miscdev;
> +     const char *devname;
> +
> +     enum se_if_dev_ctx_status_t status;
> +     struct semaphore fops_lock;
> +
> +     struct se_shared_mem_mgmt_info se_shared_mem_mgmt;
> +     struct notifier_block se_notify;

> se_notify is never used.

This will be used in next platform/feature addition.
For now, it is not needed.
Accepted, will remove this in V8.

Sascha

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