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

Sumit Garg
2025-04-01T08:46:24Z

On Tue, Mar 25, 2025 at 12:17:20PM +0100, Jens Wiklander wrote:
> Hi Sumit,
>
> On Tue, Mar 25, 2025 at 7:50 AM Sumit Garg <sumit.garg@kernel.org> wrote:
> >
> > Hi Jens,
> >
> > On Wed, Mar 05, 2025 at 02:04:12PM +0100, Jens Wiklander wrote:
> > > From: Etienne Carriere <etienne.carriere@linaro.org>
> > >
> > > 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.

Let's try to reframe this commit message to say that new ioctl allows to
register DMA buffers allocated from restricted/protected heaps with TEE
subsystem.

> > >
> > > 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@linaro.org>
> > > Signed-off-by: Olivier Masse <olivier.masse@nxp.com>
> > > Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
> > > ---
> > > 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.

Okay, that's fair enough. Lets take this new IOCTL approach then.

>
>
> > 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) {

This check is already done within tee_shm_get_parent_shm(), is it
redundant here?

> > > + 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;

This looks more of a refactoring, can we split it as a separate commit?

> > > 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.

This seems a bit complicated, can we rather inline this API as I can't
see any other current user?

-Sumit

> > > + */
> > > + 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
> > >