Re: [PATCH V2] mmc: block: Add new ioctl to send multi commands

[Grant Grundler]

On Fri, Sep 11, 2015 at 5:22 AM, Jon Hunter <jonathanh@xxxxxxxxxx> wrote:
> From: Seshagiri Holi <sholi@xxxxxxxxxx>
>
> Certain eMMC devices allow vendor specific device information to be read
> via a sequence of vendor commands. These vendor commands must be issued
> in sequence and an atomic fashion. One way to support this would be to
> add an ioctl function for sending a sequence of commands to the device
> atomically as proposed here. These multi commands are simple array of
> the existing mmc_ioc_cmd structure.
>
> The structure passed via the ioctl uses a __u64 pointer type to pass a
> pointer to the command list. The __u64 pointer type is used to ensure the
> pointer size is the same regardless of the address size used by user-space.
> The number of commands that can be passed is limited to 256 by the 8-bit
> type of the num_of_cmds member (which should be more than sufficient).
>
> Signed-off-by: Seshagiri Holi <sholi@xxxxxxxxxx>
> Cc: Arnd Bergmann <arnd@xxxxxxxx>
> Cc: Grant Grundler <grundler@xxxxxxxxxx>

Reviewed-by: Grant Grundler <grundler@xxxxxxxxxxxx>

One comment below. two actually. ;)

> Cc: Olof Johansson <olofj@xxxxxxxxxxxx>
> [ jonathanh@xxxxxxxxxx: Rebased on linux-next from v3.18. Changed
>   userspace pointer type for multi command to be a u64. Renamed
>   from combo commands to multi commands. Updated patch based upon
>   feedback review comments received. Updated commit message ]

I don't think the comment in '[]' needs to be in the commit message.
Ok to move it to where the V2 changes are listed?

> Signed-off-by: Jon Hunter <jonathanh@xxxxxxxxxx>
> ---
>
> V2 changes:
> - Updated changelog per Arnd's feedback
> - Moved mmc_put/get_card() outside of __mmc_blk_ioctl_cmd()
>
>  drivers/mmc/card/block.c       | 218 ++++++++++++++++++++++++++++++-----------
>  include/uapi/linux/mmc/ioctl.h |  22 ++++-
>  2 files changed, 184 insertions(+), 56 deletions(-)
>
> diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
> index c742cfd7674e..9bdbf1ea65ba 100644
> --- a/drivers/mmc/card/block.c
> +++ b/drivers/mmc/card/block.c
> @@ -387,6 +387,24 @@ out:
>         return ERR_PTR(err);
>  }
>
> +static int mmc_blk_ioctl_copy_to_user(struct mmc_ioc_cmd __user *ic_ptr,
> +                                     struct mmc_blk_ioc_data *idata)
> +{
> +       struct mmc_ioc_cmd *ic = &idata->ic;
> +
> +       if (copy_to_user(&(ic_ptr->response), ic->response,
> +                        sizeof(ic->response)))
> +               return -EFAULT;
> +
> +       if (!idata->ic.write_flag) {
> +               if (copy_to_user((void __user *)(unsigned long)ic->data_ptr,
> +                                idata->buf, idata->buf_bytes))
> +                       return -EFAULT;
> +       }
> +
> +       return 0;
> +}
> +
>  static int ioctl_rpmb_card_status_poll(struct mmc_card *card, u32 *status,
>                                        u32 retries_max)
>  {
> @@ -447,12 +465,9 @@ out:
>         return err;
>  }
>
> -static int mmc_blk_ioctl_cmd(struct block_device *bdev,
> -       struct mmc_ioc_cmd __user *ic_ptr)
> +static int __mmc_blk_ioctl_cmd(struct mmc_card *card, struct mmc_blk_data *md,
> +                              struct mmc_blk_ioc_data *idata)
>  {
> -       struct mmc_blk_ioc_data *idata;
> -       struct mmc_blk_data *md;
> -       struct mmc_card *card;
>         struct mmc_command cmd = {0};
>         struct mmc_data data = {0};
>         struct mmc_request mrq = {NULL};
> @@ -461,33 +476,12 @@ static int mmc_blk_ioctl_cmd(struct block_device *bdev,
>         int is_rpmb = false;
>         u32 status = 0;
>
> -       /*
> -        * The caller must have CAP_SYS_RAWIO, and must be calling this on the
> -        * whole block device, not on a partition.  This prevents overspray
> -        * between sibling partitions.
> -        */
> -       if ((!capable(CAP_SYS_RAWIO)) || (bdev != bdev->bd_contains))
> -               return -EPERM;
> -
> -       idata = mmc_blk_ioctl_copy_from_user(ic_ptr);
> -       if (IS_ERR(idata))
> -               return PTR_ERR(idata);
> -
> -       md = mmc_blk_get(bdev->bd_disk);
> -       if (!md) {
> -               err = -EINVAL;
> -               goto cmd_err;
> -       }
> +       if (!card || !md || !idata)
> +               return -EINVAL;
>
>         if (md->area_type & MMC_BLK_DATA_AREA_RPMB)
>                 is_rpmb = true;
>
> -       card = md->queue.card;
> -       if (IS_ERR(card)) {
> -               err = PTR_ERR(card);
> -               goto cmd_done;
> -       }
> -
>         cmd.opcode = idata->ic.opcode;
>         cmd.arg = idata->ic.arg;
>         cmd.flags = idata->ic.flags;
> @@ -530,23 +524,21 @@ static int mmc_blk_ioctl_cmd(struct block_device *bdev,
>
>         mrq.cmd = &cmd;
>
> -       mmc_get_card(card);
> -
>         err = mmc_blk_part_switch(card, md);
>         if (err)
> -               goto cmd_rel_host;
> +               return err;
>
>         if (idata->ic.is_acmd) {
>                 err = mmc_app_cmd(card->host, card);
>                 if (err)
> -                       goto cmd_rel_host;
> +                       return err;
>         }
>
>         if (is_rpmb) {
>                 err = mmc_set_blockcount(card, data.blocks,
>                         idata->ic.write_flag & (1 << 31));
>                 if (err)
> -                       goto cmd_rel_host;
> +                       return err;
>         }
>
>         if ((MMC_EXTRACT_INDEX_FROM_ARG(cmd.arg) == EXT_CSD_SANITIZE_START) &&
> @@ -557,7 +549,7 @@ static int mmc_blk_ioctl_cmd(struct block_device *bdev,
>                         pr_err("%s: ioctl_do_sanitize() failed. err = %d",
>                                __func__, err);
>
> -               goto cmd_rel_host;
> +               return err;
>         }
>
>         mmc_wait_for_req(card->host, &mrq);
> @@ -565,14 +557,12 @@ static int mmc_blk_ioctl_cmd(struct block_device *bdev,
>         if (cmd.error) {
>                 dev_err(mmc_dev(card->host), "%s: cmd error %d\n",
>                                                 __func__, cmd.error);
> -               err = cmd.error;
> -               goto cmd_rel_host;
> +               return cmd.error;
>         }
>         if (data.error) {
>                 dev_err(mmc_dev(card->host), "%s: data error %d\n",
>                                                 __func__, data.error);
> -               err = data.error;
> -               goto cmd_rel_host;
> +               return data.error;
>         }
>
>         /*
> @@ -582,18 +572,7 @@ static int mmc_blk_ioctl_cmd(struct block_device *bdev,
>         if (idata->ic.postsleep_min_us)
>                 usleep_range(idata->ic.postsleep_min_us, idata->ic.postsleep_max_us);
>
> -       if (copy_to_user(&(ic_ptr->response), cmd.resp, sizeof(cmd.resp))) {
> -               err = -EFAULT;
> -               goto cmd_rel_host;
> -       }
> -
> -       if (!idata->ic.write_flag) {
> -               if (copy_to_user((void __user *)(unsigned long) idata->ic.data_ptr,
> -                                               idata->buf, idata->buf_bytes)) {
> -                       err = -EFAULT;
> -                       goto cmd_rel_host;
> -               }
> -       }
> +       memcpy(&(idata->ic.response), cmd.resp, sizeof(cmd.resp));
>
>         if (is_rpmb) {
>                 /*
> @@ -607,9 +586,50 @@ static int mmc_blk_ioctl_cmd(struct block_device *bdev,
>                                         __func__, status, err);
>         }
>
> -cmd_rel_host:
> +       return err;
> +}
> +
> +static int mmc_blk_ioctl_cmd(struct block_device *bdev,
> +                            struct mmc_ioc_cmd __user *ic_ptr)
> +{
> +       struct mmc_blk_ioc_data *idata;
> +       struct mmc_blk_data *md;
> +       struct mmc_card *card;
> +       int err;
> +
> +       /*
> +        * The caller must have CAP_SYS_RAWIO, and must be calling this on the
> +        * whole block device, not on a partition.  This prevents overspray
> +        * between sibling partitions.
> +        */
> +       if ((!capable(CAP_SYS_RAWIO)) || (bdev != bdev->bd_contains))
> +               return -EPERM;
> +
> +       idata = mmc_blk_ioctl_copy_from_user(ic_ptr);
> +       if (IS_ERR(idata))
> +               return PTR_ERR(idata);
> +
> +       md = mmc_blk_get(bdev->bd_disk);
> +       if (!md) {
> +               err = -EINVAL;
> +               goto cmd_err;
> +       }
> +
> +       card = md->queue.card;
> +       if (IS_ERR(card)) {
> +               err = PTR_ERR(card);
> +               goto cmd_done;
> +       }
> +
> +       mmc_get_card(card);

Yeah, the double call in the ioc_multi_cmd case was irritating me too.

> +
> +       err = __mmc_blk_ioctl_cmd(card, md, idata);
> +
>         mmc_put_card(card);
>
> +       if (!err)
> +               err = mmc_blk_ioctl_copy_to_user(ic_ptr, idata);
> +
>  cmd_done:
>         mmc_blk_put(md);
>  cmd_err:
> @@ -618,13 +638,101 @@ cmd_err:
>         return err;
>  }
>
> +static int mmc_blk_ioctl_multi_cmd(struct block_device *bdev,
> +                                  struct mmc_ioc_multi_cmd __user *user)
> +{
> +       struct mmc_ioc_multi_cmd mcci = {0};
> +       struct mmc_blk_ioc_data **idata = NULL;
> +       struct mmc_ioc_cmd __user *cmds;
> +       struct mmc_card *card;
> +       struct mmc_blk_data *md;
> +       int i, err = -EFAULT;
> +       u8 n_cmds = 0;
> +
> +       /*
> +        * The caller must have CAP_SYS_RAWIO, and must be calling this on the
> +        * whole block device, not on a partition.  This prevents overspray
> +        * between sibling partitions.
> +        */
> +       if ((!capable(CAP_SYS_RAWIO)) || (bdev != bdev->bd_contains))
> +               return -EPERM;
> +
> +       if (copy_from_user(&mcci, user, sizeof(struct mmc_ioc_multi_cmd)))
> +               return -EFAULT;
> +
> +       if (!mcci.num_of_cmds) {
> +               err = -EINVAL;
> +               goto cmd_err;
> +       }
> +
> +       idata = kcalloc(mcci.num_of_cmds, sizeof(*idata), GFP_KERNEL);
> +       if (!idata) {
> +               err = -ENOMEM;
> +               goto cmd_err;
> +       }
> +
> +       cmds = (struct mmc_ioc_cmd __user *)(unsigned long)mcci.cmds_ptr;
> +       for (n_cmds = 0; n_cmds < mcci.num_of_cmds; n_cmds++) {
> +               idata[n_cmds] = mmc_blk_ioctl_copy_from_user(&cmds[n_cmds]);
> +               if (IS_ERR(idata[n_cmds])) {
> +                       err = PTR_ERR(idata[n_cmds]);
> +                       goto cmd_err;
> +               }
> +       }
> +
> +       md = mmc_blk_get(bdev->bd_disk);
> +       if (!md)
> +               goto cmd_err;
> +
> +       card = md->queue.card;
> +       if (IS_ERR(card)) {
> +               err = PTR_ERR(card);
> +               goto cmd_done;
> +       }
> +
> +       mmc_get_card(card);
> +
> +       for (i = 0; i < n_cmds; i++) {
> +               err = __mmc_blk_ioctl_cmd(card, md, idata[i]);
> +               if (err) {
> +                       mmc_put_card(card);
> +                       goto cmd_done;
> +               }
> +       }
> +
> +       mmc_put_card(card);
> +
> +       /* copy to user if data and response */
> +       for (i = 0; i < n_cmds; i++) {
> +               err = mmc_blk_ioctl_copy_to_user(&cmds[i], idata[i]);
> +               if (err)
> +                       break;
> +       }
> +
> +cmd_done:
> +       mmc_blk_put(md);
> +cmd_err:
> +       for (i = 0; i < n_cmds; i++) {
> +               kfree(idata[i]->buf);
> +               kfree(idata[i]);
> +       }
> +       kfree(idata);
> +       return err;
> +}
> +
>  static int mmc_blk_ioctl(struct block_device *bdev, fmode_t mode,
>         unsigned int cmd, unsigned long arg)
>  {
> -       int ret = -EINVAL;
> -       if (cmd == MMC_IOC_CMD)
> -               ret = mmc_blk_ioctl_cmd(bdev, (struct mmc_ioc_cmd __user *)arg);
> -       return ret;
> +       switch (cmd) {
> +       case MMC_IOC_CMD:
> +               return mmc_blk_ioctl_cmd(bdev,
> +                               (struct mmc_ioc_cmd __user *)arg);
> +       case MMC_IOC_MULTI_CMD:
> +               return mmc_blk_ioctl_multi_cmd(bdev,
> +                               (struct mmc_ioc_multi_cmd __user *)arg);
> +       default:
> +               return -EINVAL;
> +       }
>  }
>
>  #ifdef CONFIG_COMPAT
> diff --git a/include/uapi/linux/mmc/ioctl.h b/include/uapi/linux/mmc/ioctl.h
> index 1f5e68923929..420bd063ee45 100644
> --- a/include/uapi/linux/mmc/ioctl.h
> +++ b/include/uapi/linux/mmc/ioctl.h
> @@ -45,8 +45,28 @@ struct mmc_ioc_cmd {
>  };
>  #define mmc_ioc_cmd_set_data(ic, ptr) ic.data_ptr = (__u64)(unsigned long) ptr
>
> -#define MMC_IOC_CMD _IOWR(MMC_BLOCK_MAJOR, 0, struct mmc_ioc_cmd)
> +/**
> + * struct mmc_ioc_multi_cmd - multi command information
> + * @cmds_ptr: Address of the location where the list of commands resides
> + * @num_of_cmds: number of commands to send
> + */
> +struct mmc_ioc_multi_cmd {
> +       __u64 cmds_ptr;
> +       __u8 num_of_cmds;
>
> +       /*
> +        * Pad struct so it's size is a multiple of it's alignment.
> +        */
> +       __u8 __pad[7];
> +};

Is this the final structure or we going to adopt Arnd's suggestion for:
struct mmc_ioc_multi_cmd {
     __u64 num_of_cmds;
     struct mmc_ioc_cmd cmds[0];
}

After having slept on it, I like this better (feels "cleaner").

And "fgrep -R '[0];' /usr/include/linux" tells me this non-standard
gcc feature is already widely "visible" to user space compilers.

cheers,
grant

> +
> +#define MMC_IOC_CMD _IOWR(MMC_BLOCK_MAJOR, 0, struct mmc_ioc_cmd)
> +/*
> + * MMC_IOC_MULTI_CMD: Used to send an array of MMC commands described by
> + *     the structure mmc_ioc_multi_cmd. The MMC driver will issue all
> + *     commands in array in sequence to card.
> + */
> +#define MMC_IOC_MULTI_CMD _IOWR(MMC_BLOCK_MAJOR, 1, struct mmc_ioc_multi_cmd)
>  /*
>   * Since this ioctl is only meant to enhance (and not replace) normal access
>   * to the mmc bus device, an upper data transfer limit of MMC_IOC_MAX_BYTES
> --
> 2.1.4
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/