Re: [PATCH v6 06/10] tee: new ioctl to a register tee_shm from a dmabuf file descriptor

[Jens Wiklander]

Hi Sumit,

On Tue, Mar 25, 2025 at 7:50 AM Sumit Garg <sumit.garg@xxxxxxxxxx> wrote:
>
> Hi Jens,
>
> On Wed, Mar 05, 2025 at 02:04:12PM +0100, Jens Wiklander wrote:
> > From: Etienne Carriere <etienne.carriere@xxxxxxxxxx>
> >
> > Enable userspace to create a tee_shm object that refers to a dmabuf
> > reference.
> >
> > Userspace registers the dmabuf file descriptor as in a tee_shm object.
> > The registration is completed with a tee_shm file descriptor returned to
> > userspace.
> >
> > Userspace is free to close the dmabuf file descriptor now since all the
> > resources are now held via the tee_shm object.
> >
> > Closing the tee_shm file descriptor will release all resources used by the
> > tee_shm object.
> >
> > This change only support dmabuf references that relates to physically
> > contiguous memory buffers.
> >
> > New tee_shm flag to identify tee_shm objects built from a registered
> > dmabuf, TEE_SHM_DMA_BUF.
> >
> > Signed-off-by: Etienne Carriere <etienne.carriere@xxxxxxxxxx>
> > Signed-off-by: Olivier Masse <olivier.masse@xxxxxxx>
> > Signed-off-by: Jens Wiklander <jens.wiklander@xxxxxxxxxx>
> > ---
> >  drivers/tee/tee_core.c    | 145 ++++++++++++++++++++++++++-----------
> >  drivers/tee/tee_private.h |   1 +
> >  drivers/tee/tee_shm.c     | 146 ++++++++++++++++++++++++++++++++++++--
> >  include/linux/tee_core.h  |   1 +
> >  include/linux/tee_drv.h   |  10 +++
> >  include/uapi/linux/tee.h  |  29 ++++++++
> >  6 files changed, 288 insertions(+), 44 deletions(-)
> >
>
> I am still trying to find if we really need a separate IOCTL to register
> DMA heap with TEE subsystem. Can't we initialize tee_shm as a member of
> struct tee_heap_buffer in tee_dma_heap_alloc() where the allocation
> happens?

No, that's not possible since we don't have a tee_context availble so
we can't assign an ID that userspace can use for this shm object.

We could add new attribute types TEE_IOCTL_PARAM_ATTR_TYPE_MEMFD_*,
but it's a bit more complicated than that since we'd also need to
update for the life cycle.


> We can always find a reference back to tee_shm object from DMA
> buffer.

Yes

Cheers,
Jens

>
> -Sumit
>
> > diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c
> > index 685afcaa3ea1..3a71643766d5 100644
> > --- a/drivers/tee/tee_core.c
> > +++ b/drivers/tee/tee_core.c
> > @@ -353,6 +353,103 @@ tee_ioctl_shm_register(struct tee_context *ctx,
> >       return ret;
> >  }
> >
> > +static int
> > +tee_ioctl_shm_register_fd(struct tee_context *ctx,
> > +                       struct tee_ioctl_shm_register_fd_data __user *udata)
> > +{
> > +     struct tee_ioctl_shm_register_fd_data data;
> > +     struct tee_shm *shm;
> > +     long ret;
> > +
> > +     if (copy_from_user(&data, udata, sizeof(data)))
> > +             return -EFAULT;
> > +
> > +     /* Currently no input flags are supported */
> > +     if (data.flags)
> > +             return -EINVAL;
> > +
> > +     shm = tee_shm_register_fd(ctx, data.fd);
> > +     if (IS_ERR(shm))
> > +             return -EINVAL;
> > +
> > +     data.id = shm->id;
> > +     data.flags = shm->flags;
> > +     data.size = shm->size;
> > +
> > +     if (copy_to_user(udata, &data, sizeof(data)))
> > +             ret = -EFAULT;
> > +     else
> > +             ret = tee_shm_get_fd(shm);
> > +
> > +     /*
> > +      * When user space closes the file descriptor the shared memory
> > +      * should be freed or if tee_shm_get_fd() failed then it will
> > +      * be freed immediately.
> > +      */
> > +     tee_shm_put(shm);
> > +     return ret;
> > +}
> > +
> > +static int param_from_user_memref(struct tee_context *ctx,
> > +                               struct tee_param_memref *memref,
> > +                               struct tee_ioctl_param *ip)
> > +{
> > +     struct tee_shm *shm;
> > +     size_t offs = 0;
> > +
> > +     /*
> > +      * If a NULL pointer is passed to a TA in the TEE,
> > +      * the ip.c IOCTL parameters is set to TEE_MEMREF_NULL
> > +      * indicating a NULL memory reference.
> > +      */
> > +     if (ip->c != TEE_MEMREF_NULL) {
> > +             /*
> > +              * If we fail to get a pointer to a shared
> > +              * memory object (and increase the ref count)
> > +              * from an identifier we return an error. All
> > +              * pointers that has been added in params have
> > +              * an increased ref count. It's the callers
> > +              * responibility to do tee_shm_put() on all
> > +              * resolved pointers.
> > +              */
> > +             shm = tee_shm_get_from_id(ctx, ip->c);
> > +             if (IS_ERR(shm))
> > +                     return PTR_ERR(shm);
> > +
> > +             /*
> > +              * Ensure offset + size does not overflow
> > +              * offset and does not overflow the size of
> > +              * the referred shared memory object.
> > +              */
> > +             if ((ip->a + ip->b) < ip->a ||
> > +                 (ip->a + ip->b) > shm->size) {
> > +                     tee_shm_put(shm);
> > +                     return -EINVAL;
> > +             }
> > +
> > +             if (shm->flags & TEE_SHM_DMA_BUF) {
> > +                     struct tee_shm *parent_shm;
> > +
> > +                     parent_shm = tee_shm_get_parent_shm(shm, &offs);
> > +                     if (parent_shm) {
> > +                             tee_shm_put(shm);
> > +                             shm = parent_shm;
> > +                     }
> > +             }
> > +     } else if (ctx->cap_memref_null) {
> > +             /* Pass NULL pointer to OP-TEE */
> > +             shm = NULL;
> > +     } else {
> > +             return -EINVAL;
> > +     }
> > +
> > +     memref->shm_offs = ip->a + offs;
> > +     memref->size = ip->b;
> > +     memref->shm = shm;
> > +
> > +     return 0;
> > +}
> > +
> >  static int params_from_user(struct tee_context *ctx, struct tee_param *params,
> >                           size_t num_params,
> >                           struct tee_ioctl_param __user *uparams)
> > @@ -360,8 +457,8 @@ static int params_from_user(struct tee_context *ctx, struct tee_param *params,
> >       size_t n;
> >
> >       for (n = 0; n < num_params; n++) {
> > -             struct tee_shm *shm;
> >               struct tee_ioctl_param ip;
> > +             int rc;
> >
> >               if (copy_from_user(&ip, uparams + n, sizeof(ip)))
> >                       return -EFAULT;
> > @@ -384,45 +481,10 @@ static int params_from_user(struct tee_context *ctx, struct tee_param *params,
> >               case TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_INPUT:
> >               case TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_OUTPUT:
> >               case TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_INOUT:
> > -                     /*
> > -                      * If a NULL pointer is passed to a TA in the TEE,
> > -                      * the ip.c IOCTL parameters is set to TEE_MEMREF_NULL
> > -                      * indicating a NULL memory reference.
> > -                      */
> > -                     if (ip.c != TEE_MEMREF_NULL) {
> > -                             /*
> > -                              * If we fail to get a pointer to a shared
> > -                              * memory object (and increase the ref count)
> > -                              * from an identifier we return an error. All
> > -                              * pointers that has been added in params have
> > -                              * an increased ref count. It's the callers
> > -                              * responibility to do tee_shm_put() on all
> > -                              * resolved pointers.
> > -                              */
> > -                             shm = tee_shm_get_from_id(ctx, ip.c);
> > -                             if (IS_ERR(shm))
> > -                                     return PTR_ERR(shm);
> > -
> > -                             /*
> > -                              * Ensure offset + size does not overflow
> > -                              * offset and does not overflow the size of
> > -                              * the referred shared memory object.
> > -                              */
> > -                             if ((ip.a + ip.b) < ip.a ||
> > -                                 (ip.a + ip.b) > shm->size) {
> > -                                     tee_shm_put(shm);
> > -                                     return -EINVAL;
> > -                             }
> > -                     } else if (ctx->cap_memref_null) {
> > -                             /* Pass NULL pointer to OP-TEE */
> > -                             shm = NULL;
> > -                     } else {
> > -                             return -EINVAL;
> > -                     }
> > -
> > -                     params[n].u.memref.shm_offs = ip.a;
> > -                     params[n].u.memref.size = ip.b;
> > -                     params[n].u.memref.shm = shm;
> > +                     rc = param_from_user_memref(ctx, &params[n].u.memref,
> > +                                                 &ip);
> > +                     if (rc)
> > +                             return rc;
> >                       break;
> >               default:
> >                       /* Unknown attribute */
> > @@ -827,6 +889,8 @@ static long tee_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
> >               return tee_ioctl_shm_alloc(ctx, uarg);
> >       case TEE_IOC_SHM_REGISTER:
> >               return tee_ioctl_shm_register(ctx, uarg);
> > +     case TEE_IOC_SHM_REGISTER_FD:
> > +             return tee_ioctl_shm_register_fd(ctx, uarg);
> >       case TEE_IOC_OPEN_SESSION:
> >               return tee_ioctl_open_session(ctx, uarg);
> >       case TEE_IOC_INVOKE:
> > @@ -1288,3 +1352,4 @@ MODULE_AUTHOR("Linaro");
> >  MODULE_DESCRIPTION("TEE Driver");
> >  MODULE_VERSION("1.0");
> >  MODULE_LICENSE("GPL v2");
> > +MODULE_IMPORT_NS("DMA_BUF");
> > diff --git a/drivers/tee/tee_private.h b/drivers/tee/tee_private.h
> > index 6c6ff5d5eed2..aad7f6c7e0f0 100644
> > --- a/drivers/tee/tee_private.h
> > +++ b/drivers/tee/tee_private.h
> > @@ -24,6 +24,7 @@ void teedev_ctx_put(struct tee_context *ctx);
> >  struct tee_shm *tee_shm_alloc_user_buf(struct tee_context *ctx, size_t size);
> >  struct tee_shm *tee_shm_register_user_buf(struct tee_context *ctx,
> >                                         unsigned long addr, size_t length);
> > +struct tee_shm *tee_shm_get_parent_shm(struct tee_shm *shm, size_t *offs);
> >
> >  int tee_heap_update_from_dma_buf(struct tee_device *teedev,
> >                                struct dma_buf *dmabuf, size_t *offset,
> > diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c
> > index daf6e5cfd59a..8b79918468b5 100644
> > --- a/drivers/tee/tee_shm.c
> > +++ b/drivers/tee/tee_shm.c
> > @@ -4,6 +4,7 @@
> >   */
> >  #include <linux/anon_inodes.h>
> >  #include <linux/device.h>
> > +#include <linux/dma-buf.h>
> >  #include <linux/idr.h>
> >  #include <linux/io.h>
> >  #include <linux/mm.h>
> > @@ -15,6 +16,16 @@
> >  #include <linux/highmem.h>
> >  #include "tee_private.h"
> >
> > +/* extra references appended to shm object for registered shared memory */
> > +struct tee_shm_dmabuf_ref {
> > +     struct tee_shm shm;
> > +     size_t offset;
> > +     struct dma_buf *dmabuf;
> > +     struct dma_buf_attachment *attach;
> > +     struct sg_table *sgt;
> > +     struct tee_shm *parent_shm;
> > +};
> > +
> >  static void shm_put_kernel_pages(struct page **pages, size_t page_count)
> >  {
> >       size_t n;
> > @@ -45,7 +56,23 @@ static void release_registered_pages(struct tee_shm *shm)
> >
> >  static void tee_shm_release(struct tee_device *teedev, struct tee_shm *shm)
> >  {
> > -     if (shm->flags & TEE_SHM_POOL) {
> > +     struct tee_shm *parent_shm = NULL;
> > +     void *p = shm;
> > +
> > +     if (shm->flags & TEE_SHM_DMA_BUF) {
> > +             struct tee_shm_dmabuf_ref *ref;
> > +
> > +             ref = container_of(shm, struct tee_shm_dmabuf_ref, shm);
> > +             parent_shm = ref->parent_shm;
> > +             p = ref;
> > +             if (ref->attach) {
> > +                     dma_buf_unmap_attachment(ref->attach, ref->sgt,
> > +                                              DMA_BIDIRECTIONAL);
> > +
> > +                     dma_buf_detach(ref->dmabuf, ref->attach);
> > +             }
> > +             dma_buf_put(ref->dmabuf);
> > +     } else if (shm->flags & TEE_SHM_POOL) {
> >               teedev->pool->ops->free(teedev->pool, shm);
> >       } else if (shm->flags & TEE_SHM_DYNAMIC) {
> >               int rc = teedev->desc->ops->shm_unregister(shm->ctx, shm);
> > @@ -57,9 +84,10 @@ static void tee_shm_release(struct tee_device *teedev, struct tee_shm *shm)
> >               release_registered_pages(shm);
> >       }
> >
> > -     teedev_ctx_put(shm->ctx);
> > +     if (shm->ctx)
> > +             teedev_ctx_put(shm->ctx);
> >
> > -     kfree(shm);
> > +     kfree(p);
> >
> >       tee_device_put(teedev);
> >  }
> > @@ -169,7 +197,7 @@ struct tee_shm *tee_shm_alloc_user_buf(struct tee_context *ctx, size_t size)
> >   * tee_client_invoke_func(). The memory allocated is later freed with a
> >   * call to tee_shm_free().
> >   *
> > - * @returns a pointer to 'struct tee_shm'
> > + * @returns a pointer to 'struct tee_shm' on success, and ERR_PTR on failure
> >   */
> >  struct tee_shm *tee_shm_alloc_kernel_buf(struct tee_context *ctx, size_t size)
> >  {
> > @@ -179,6 +207,116 @@ struct tee_shm *tee_shm_alloc_kernel_buf(struct tee_context *ctx, size_t size)
> >  }
> >  EXPORT_SYMBOL_GPL(tee_shm_alloc_kernel_buf);
> >
> > +struct tee_shm *tee_shm_register_fd(struct tee_context *ctx, int fd)
> > +{
> > +     struct tee_shm_dmabuf_ref *ref;
> > +     int rc;
> > +
> > +     if (!tee_device_get(ctx->teedev))
> > +             return ERR_PTR(-EINVAL);
> > +
> > +     teedev_ctx_get(ctx);
> > +
> > +     ref = kzalloc(sizeof(*ref), GFP_KERNEL);
> > +     if (!ref) {
> > +             rc = -ENOMEM;
> > +             goto err_put_tee;
> > +     }
> > +
> > +     refcount_set(&ref->shm.refcount, 1);
> > +     ref->shm.ctx = ctx;
> > +     ref->shm.id = -1;
> > +     ref->shm.flags = TEE_SHM_DMA_BUF;
> > +
> > +     ref->dmabuf = dma_buf_get(fd);
> > +     if (IS_ERR(ref->dmabuf)) {
> > +             rc = PTR_ERR(ref->dmabuf);
> > +             goto err_kfree_ref;
> > +     }
> > +
> > +     rc = tee_heap_update_from_dma_buf(ctx->teedev, ref->dmabuf,
> > +                                       &ref->offset, &ref->shm,
> > +                                       &ref->parent_shm);
> > +     if (!rc)
> > +             goto out;
> > +     if (rc != -EINVAL)
> > +             goto err_put_dmabuf;
> > +
> > +     ref->attach = dma_buf_attach(ref->dmabuf, &ctx->teedev->dev);
> > +     if (IS_ERR(ref->attach)) {
> > +             rc = PTR_ERR(ref->attach);
> > +             goto err_put_dmabuf;
> > +     }
> > +
> > +     ref->sgt = dma_buf_map_attachment(ref->attach, DMA_BIDIRECTIONAL);
> > +     if (IS_ERR(ref->sgt)) {
> > +             rc = PTR_ERR(ref->sgt);
> > +             goto err_detach;
> > +     }
> > +
> > +     if (sg_nents(ref->sgt->sgl) != 1) {
> > +             rc = PTR_ERR(ref->sgt->sgl);
> > +             goto err_unmap_attachement;
> > +     }
> > +
> > +     ref->shm.paddr = page_to_phys(sg_page(ref->sgt->sgl));
> > +     ref->shm.size = ref->sgt->sgl->length;
> > +
> > +out:
> > +     mutex_lock(&ref->shm.ctx->teedev->mutex);
> > +     ref->shm.id = idr_alloc(&ref->shm.ctx->teedev->idr, &ref->shm,
> > +                             1, 0, GFP_KERNEL);
> > +     mutex_unlock(&ref->shm.ctx->teedev->mutex);
> > +     if (ref->shm.id < 0) {
> > +             rc = ref->shm.id;
> > +             if (ref->attach)
> > +                     goto err_unmap_attachement;
> > +             goto err_put_dmabuf;
> > +     }
> > +
> > +     return &ref->shm;
> > +
> > +err_unmap_attachement:
> > +     dma_buf_unmap_attachment(ref->attach, ref->sgt, DMA_BIDIRECTIONAL);
> > +err_detach:
> > +     dma_buf_detach(ref->dmabuf, ref->attach);
> > +err_put_dmabuf:
> > +     dma_buf_put(ref->dmabuf);
> > +err_kfree_ref:
> > +     kfree(ref);
> > +err_put_tee:
> > +     teedev_ctx_put(ctx);
> > +     tee_device_put(ctx->teedev);
> > +
> > +     return ERR_PTR(rc);
> > +}
> > +EXPORT_SYMBOL_GPL(tee_shm_register_fd);
> > +
> > +struct tee_shm *tee_shm_get_parent_shm(struct tee_shm *shm, size_t *offs)
> > +{
> > +     struct tee_shm *parent_shm = NULL;
> > +
> > +     if (shm->flags & TEE_SHM_DMA_BUF) {
> > +             struct tee_shm_dmabuf_ref *ref;
> > +
> > +             ref = container_of(shm, struct tee_shm_dmabuf_ref, shm);
> > +             if (ref->parent_shm) {
> > +                     /*
> > +                      * the shm already has one reference to
> > +                      * ref->parent_shm so we should be clear of 0.
> > +                      * We're getting another reference since the caller
> > +                      * of this function expects to put the returned
> > +                      * parent_shm when it's done with it.
> > +                      */
> > +                     parent_shm = ref->parent_shm;
> > +                     refcount_inc(&parent_shm->refcount);
> > +                     *offs = ref->offset;
> > +             }
> > +     }
> > +
> > +     return parent_shm;
> > +}
> > +
> >  /**
> >   * tee_shm_alloc_priv_buf() - Allocate shared memory for a privately shared
> >   *                         kernel buffer
> > diff --git a/include/linux/tee_core.h b/include/linux/tee_core.h
> > index 16ef078247ae..6bd833b6d0e1 100644
> > --- a/include/linux/tee_core.h
> > +++ b/include/linux/tee_core.h
> > @@ -28,6 +28,7 @@
> >  #define TEE_SHM_USER_MAPPED  BIT(1)  /* Memory mapped in user space */
> >  #define TEE_SHM_POOL         BIT(2)  /* Memory allocated from pool */
> >  #define TEE_SHM_PRIV         BIT(3)  /* Memory private to TEE driver */
> > +#define TEE_SHM_DMA_BUF              BIT(4)  /* Memory with dma-buf handle */
> >
> >  #define TEE_DEVICE_FLAG_REGISTERED   0x1
> >  #define TEE_MAX_DEV_NAME_LEN         32
> > diff --git a/include/linux/tee_drv.h b/include/linux/tee_drv.h
> > index a54c203000ed..824f1251de60 100644
> > --- a/include/linux/tee_drv.h
> > +++ b/include/linux/tee_drv.h
> > @@ -116,6 +116,16 @@ struct tee_shm *tee_shm_alloc_kernel_buf(struct tee_context *ctx, size_t size);
> >  struct tee_shm *tee_shm_register_kernel_buf(struct tee_context *ctx,
> >                                           void *addr, size_t length);
> >
> > +/**
> > + * tee_shm_register_fd() - Register shared memory from file descriptor
> > + *
> > + * @ctx:     Context that allocates the shared memory
> > + * @fd:              Shared memory file descriptor reference
> > + *
> > + * @returns a pointer to 'struct tee_shm' on success, and ERR_PTR on failure
> > + */
> > +struct tee_shm *tee_shm_register_fd(struct tee_context *ctx, int fd);
> > +
> >  /**
> >   * tee_shm_free() - Free shared memory
> >   * @shm:     Handle to shared memory to free
> > diff --git a/include/uapi/linux/tee.h b/include/uapi/linux/tee.h
> > index d0430bee8292..1f9a4ac2b211 100644
> > --- a/include/uapi/linux/tee.h
> > +++ b/include/uapi/linux/tee.h
> > @@ -118,6 +118,35 @@ struct tee_ioctl_shm_alloc_data {
> >  #define TEE_IOC_SHM_ALLOC    _IOWR(TEE_IOC_MAGIC, TEE_IOC_BASE + 1, \
> >                                    struct tee_ioctl_shm_alloc_data)
> >
> > +/**
> > + * struct tee_ioctl_shm_register_fd_data - Shared memory registering argument
> > + * @fd:              [in] File descriptor identifying the shared memory
> > + * @size:    [out] Size of shared memory to allocate
> > + * @flags:   [in] Flags to/from allocation.
> > + * @id:              [out] Identifier of the shared memory
> > + *
> > + * The flags field should currently be zero as input. Updated by the call
> > + * with actual flags as defined by TEE_IOCTL_SHM_* above.
> > + * This structure is used as argument for TEE_IOC_SHM_REGISTER_FD below.
> > + */
> > +struct tee_ioctl_shm_register_fd_data {
> > +     __s64 fd;
> > +     __u64 size;
> > +     __u32 flags;
> > +     __s32 id;
> > +};
> > +
> > +/**
> > + * TEE_IOC_SHM_REGISTER_FD - register a shared memory from a file descriptor
> > + *
> > + * Returns a file descriptor on success or < 0 on failure
> > + *
> > + * The returned file descriptor refers to the shared memory object in kernel
> > + * land. The shared memory is freed when the descriptor is closed.
> > + */
> > +#define TEE_IOC_SHM_REGISTER_FD      _IOWR(TEE_IOC_MAGIC, TEE_IOC_BASE + 8, \
> > +                                  struct tee_ioctl_shm_register_fd_data)
> > +
> >  /**
> >   * struct tee_ioctl_buf_data - Variable sized buffer
> >   * @buf_ptr: [in] A __user pointer to a buffer
> > --
> > 2.43.0
> >