Subject: Re: [PATCH 7/7] tee: replace tee_shm_alloc()

From: Tyler Hicks <[email-masked]>
Date: Wed, 9 Jun 2021 10:32:15 -0500

On 2021-06-09 12:23:24, Jens Wiklander wrote:
> tee_shm_alloc() is replaced by three new functions,
> 
> tee_shm_alloc_user_buf() - for user mode allocations, replacing passing
> the flags TEE_SHM_MAPPED | TEE_SHM_DMA_BUF
> 
> tee_shm_alloc_kernel_buf() - for kernel mode allocations, slightly
> optimized compared to using the flags TEE_SHM_MAPPED | TEE_SHM_DMA_BUF
> since we now can avoid using the dma-buf registration.
> 
> tee_shm_alloc_anon_kernel_buf() - for TEE driver internal use only
> allowing decoupling a shared memory object from its original
> tee_context.
> 
> This also makes the interface easier to use as we can get rid of the
> somewhat hard to use flags parameter.
> 
> The TEE subsystem and the TEE drivers are updated to use the new
> functions instead.
> 
> Signed-off-by: Jens Wiklander <[email-masked]>
> ---
>  drivers/tee/optee/call.c   |  16 ++--
>  drivers/tee/optee/core.c   |   4 +-
>  drivers/tee/optee/device.c |   5 +-
>  drivers/tee/optee/rpc.c    |   8 +-
>  drivers/tee/tee_core.c     |   2 +-
>  drivers/tee/tee_shm.c      | 186 +++++++++++++++++++++++++++----------
>  include/linux/tee_drv.h    |  19 +---
>  7 files changed, 156 insertions(+), 84 deletions(-)
> 
> diff --git a/drivers/tee/optee/call.c b/drivers/tee/optee/call.c
> index 6132cc8d014c..f31257649c0e 100644
> --- a/drivers/tee/optee/call.c
> +++ b/drivers/tee/optee/call.c
> @@ -183,8 +183,8 @@ static struct tee_shm *get_msg_arg(struct tee_context *ctx, size_t num_params,
>  	struct tee_shm *shm;
>  	struct optee_msg_arg *ma;
>  
> -	shm = tee_shm_alloc(ctx, OPTEE_MSG_GET_ARG_SIZE(num_params),
> -			    TEE_SHM_MAPPED);
> +	shm = tee_shm_alloc_anon_kernel_buf(ctx,
> +					    OPTEE_MSG_GET_ARG_SIZE(num_params));

The error handling in get_msg_arg() should be updated to call
tee_shm_free_anon_kernel_buf() instead of tee_shm_free().

>  	if (IS_ERR(shm))
>  		return shm;
>  
> @@ -281,7 +281,7 @@ int optee_open_session(struct tee_context *ctx,
>  		arg->ret_origin = msg_arg->ret_origin;
>  	}
>  out:
> -	tee_shm_free(shm);
> +	tee_shm_free_anon_kernel_buf(ctx, shm);
>  
>  	return rc;
>  }
> @@ -312,7 +312,7 @@ int optee_close_session(struct tee_context *ctx, u32 session)
>  	msg_arg->session = session;
>  	optee_do_call_with_arg(ctx, msg_parg);
>  
> -	tee_shm_free(shm);
> +	tee_shm_free_anon_kernel_buf(ctx, shm);
>  	return 0;
>  }
>  
> @@ -358,7 +358,7 @@ int optee_invoke_func(struct tee_context *ctx, struct tee_ioctl_invoke_arg *arg,
>  	arg->ret = msg_arg->ret;
>  	arg->ret_origin = msg_arg->ret_origin;
>  out:
> -	tee_shm_free(shm);
> +	tee_shm_free_anon_kernel_buf(ctx, shm);
>  	return rc;
>  }
>  
> @@ -386,7 +386,7 @@ int optee_cancel_req(struct tee_context *ctx, u32 cancel_id, u32 session)
>  	msg_arg->cancel_id = cancel_id;
>  	optee_do_call_with_arg(ctx, msg_parg);
>  
> -	tee_shm_free(shm);
> +	tee_shm_free_anon_kernel_buf(ctx, shm);
>  	return 0;
>  }
>  
> @@ -625,7 +625,7 @@ int optee_shm_register(struct tee_context *ctx, struct tee_shm *shm,
>  	    msg_arg->ret != TEEC_SUCCESS)
>  		rc = -EINVAL;
>  
> -	tee_shm_free(shm_arg);
> +	tee_shm_free_anon_kernel_buf(ctx, shm_arg);
>  out:
>  	optee_free_pages_list(pages_list, num_pages);
>  	return rc;
> @@ -650,7 +650,7 @@ int optee_shm_unregister(struct tee_context *ctx, struct tee_shm *shm)
>  	if (optee_do_call_with_arg(ctx, msg_parg) ||
>  	    msg_arg->ret != TEEC_SUCCESS)
>  		rc = -EINVAL;
> -	tee_shm_free(shm_arg);
> +	tee_shm_free_anon_kernel_buf(ctx, shm_arg);
>  	return rc;
>  }
>  
> diff --git a/drivers/tee/optee/core.c b/drivers/tee/optee/core.c
> index 0c287345f9fe..a15dc3881636 100644
> --- a/drivers/tee/optee/core.c
> +++ b/drivers/tee/optee/core.c
> @@ -277,7 +277,7 @@ static void optee_release(struct tee_context *ctx)
>  	if (!ctxdata)
>  		return;
>  
> -	shm = tee_shm_alloc(ctx, sizeof(struct optee_msg_arg), TEE_SHM_MAPPED);
> +	shm = tee_shm_alloc_anon_kernel_buf(ctx, sizeof(struct optee_msg_arg));
>  	if (!IS_ERR(shm)) {
>  		arg = tee_shm_get_va(shm, 0);
>  		/*
> @@ -305,7 +305,7 @@ static void optee_release(struct tee_context *ctx)
>  	kfree(ctxdata);
>  
>  	if (!IS_ERR(shm))
> -		tee_shm_free(shm);
> +		tee_shm_free_anon_kernel_buf(ctx, shm);
>  
>  	ctx->data = NULL;
>  
> diff --git a/drivers/tee/optee/device.c b/drivers/tee/optee/device.c
> index ec1d24693eba..5a5bf86b1b95 100644
> --- a/drivers/tee/optee/device.c
> +++ b/drivers/tee/optee/device.c
> @@ -113,10 +113,9 @@ static int __optee_enumerate_devices(u32 func)
>  	if (rc < 0 || !shm_size)
>  		goto out_sess;
>  
> -	device_shm = tee_shm_alloc(ctx, shm_size,
> -				   TEE_SHM_MAPPED | TEE_SHM_DMA_BUF);
> +	device_shm = tee_shm_alloc_kernel_buf(ctx, shm_size);

The error handling in the 'err' label needs to use
tee_shm_free_anon_kernel_buf() instead of tee_shm_free().

>  	if (IS_ERR(device_shm)) {
> -		pr_err("tee_shm_alloc failed\n");
> +		pr_err("tee_shm_alloc_kernel_buf failed\n");
>  		rc = PTR_ERR(device_shm);
>  		goto out_sess;
>  	}
> diff --git a/drivers/tee/optee/rpc.c b/drivers/tee/optee/rpc.c
> index 1849180b0278..9108aedb3eee 100644
> --- a/drivers/tee/optee/rpc.c
> +++ b/drivers/tee/optee/rpc.c
> @@ -314,7 +314,7 @@ static void handle_rpc_func_cmd_shm_alloc(struct tee_context *ctx,
>  		shm = cmd_alloc_suppl(ctx, sz);
>  		break;
>  	case OPTEE_RPC_SHM_TYPE_KERNEL:
> -		shm = tee_shm_alloc(ctx, sz, TEE_SHM_MAPPED);
> +		shm = tee_shm_alloc_anon_kernel_buf(ctx, sz);

The error handling in the 'bad' label still uses tee_shm_free(). I guess
it needs to do something like handle_rpc_func_cmd_shm_free()?

>  		break;
>  	default:
>  		arg->ret = TEEC_ERROR_BAD_PARAMETERS;
> @@ -424,7 +424,7 @@ static void handle_rpc_func_cmd_shm_free(struct tee_context *ctx,
>  		cmd_free_suppl(ctx, shm);
>  		break;
>  	case OPTEE_RPC_SHM_TYPE_KERNEL:
> -		tee_shm_free(shm);
> +		tee_shm_free_anon_kernel_buf(ctx, shm);
>  		break;
>  	default:
>  		arg->ret = TEEC_ERROR_BAD_PARAMETERS;
> @@ -502,7 +502,7 @@ void optee_handle_rpc(struct tee_context *ctx, struct optee_rpc_param *param,
>  
>  	switch (OPTEE_SMC_RETURN_GET_RPC_FUNC(param->a0)) {
>  	case OPTEE_SMC_RPC_FUNC_ALLOC:
> -		shm = tee_shm_alloc(ctx, param->a1, TEE_SHM_MAPPED);
> +		shm = tee_shm_alloc_anon_kernel_buf(ctx, param->a1);
>  		if (!IS_ERR(shm) && !tee_shm_get_pa(shm, 0, &pa)) {
>  			reg_pair_from_64(&param->a1, &param->a2, pa);
>  			reg_pair_from_64(&param->a4, &param->a5,
> @@ -516,7 +516,7 @@ void optee_handle_rpc(struct tee_context *ctx, struct optee_rpc_param *param,
>  		break;
>  	case OPTEE_SMC_RPC_FUNC_FREE:
>  		shm = reg_pair_to_ptr(param->a1, param->a2);
> -		tee_shm_free(shm);
> +		tee_shm_free_anon_kernel_buf(ctx, shm);
>  		break;
>  	case OPTEE_SMC_RPC_FUNC_FOREIGN_INTR:
>  		/*
> diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c
> index 480d294a23ab..4f5c7c17a434 100644
> --- a/drivers/tee/tee_core.c
> +++ b/drivers/tee/tee_core.c
> @@ -293,7 +293,7 @@ static int tee_ioctl_shm_alloc(struct tee_context *ctx,
>  	if (data.flags)
>  		return -EINVAL;
>  
> -	shm = tee_shm_alloc(ctx, data.size, TEE_SHM_MAPPED | TEE_SHM_DMA_BUF);
> +	shm = tee_shm_alloc_user_buf(ctx, data.size);
>  	if (IS_ERR(shm))
>  		return PTR_ERR(shm);
>  
> diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c
> index 63fce8d39d8b..d134e2778a3a 100644
> --- a/drivers/tee/tee_shm.c
> +++ b/drivers/tee/tee_shm.c
> @@ -96,25 +96,14 @@ static const struct dma_buf_ops tee_shm_dma_buf_ops = {
>  	.mmap = tee_shm_op_mmap,
>  };
>  
> -struct tee_shm *tee_shm_alloc(struct tee_context *ctx, size_t size, u32 flags)
> +static struct tee_shm *shm_alloc_helper(struct tee_context *ctx, size_t size,
> +					size_t align, u32 flags)
>  {
>  	struct tee_device *teedev = ctx->teedev;
>  	struct tee_shm *shm;
> -	size_t align;
>  	void *ret;
>  	int rc;
>  
> -	if (!(flags & TEE_SHM_MAPPED)) {
> -		dev_err(teedev->dev.parent,
> -			"only mapped allocations supported\n");
> -		return ERR_PTR(-EINVAL);
> -	}
> -
> -	if ((flags & ~(TEE_SHM_MAPPED | TEE_SHM_DMA_BUF))) {
> -		dev_err(teedev->dev.parent, "invalid shm flags 0x%x", flags);
> -		return ERR_PTR(-EINVAL);
> -	}
> -
>  	if (!tee_device_get(teedev))
>  		return ERR_PTR(-EINVAL);
>  
> @@ -131,17 +120,14 @@ struct tee_shm *tee_shm_alloc(struct tee_context *ctx, size_t size, u32 flags)
>  	}
>  
>  	shm->flags = flags | TEE_SHM_POOL;
> +
> +	/*
> +	 * We're assigning this as it is needed if the shm is to be
> +	 * registered. If this function returns OK then the caller expected
> +	 * to call teedev_ctx_get() or clear shm->ctx in case it's not
> +	 * needed any longer.
> +	 */
>  	shm->ctx = ctx;
> -	if (flags & TEE_SHM_DMA_BUF) {
> -		align = PAGE_SIZE;
> -		/*
> -		 * Request to register the shm in the pool allocator below
> -		 * if supported.
> -		 */
> -		shm->flags |= TEE_SHM_REGISTER;
> -	} else {
> -		align = 2 * sizeof(long);
> -	}
>  
>  	rc = teedev->pool->ops->alloc(teedev->pool, shm, size, align);
>  	if (rc) {
> @@ -149,48 +135,71 @@ struct tee_shm *tee_shm_alloc(struct tee_context *ctx, size_t size, u32 flags)
>  		goto err_kfree;
>  	}
>  
> +	return shm;
> +err_kfree:
> +	kfree(shm);
> +err_dev_put:
> +	tee_device_put(teedev);
> +	return ret;
> +}
>  
> -	if (flags & TEE_SHM_DMA_BUF) {
> -		DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
> +/**
> + * tee_shm_alloc_user_buf() - Allocate shared memory for user space
> + * @ctx:	Context that allocates the shared memory
> + * @size:	Requested size of shared memory
> + *
> + * Memory allocated as user space shared memory is automatically freed when
> + * the TEE file pointer is closed. The primary usage of this function is
> + * when the TEE driver doesn't support registering ordinary user space
> + * memory.
> + *
> + * @returns a pointer to 'struct tee_shm'
> + */
> +struct tee_shm *tee_shm_alloc_user_buf(struct tee_context *ctx, size_t size)
> +{
> +	u32 flags = TEE_SHM_MAPPED | TEE_SHM_DMA_BUF | TEE_SHM_REGISTER;

Why not TEE_SHM_USER_MAPPED instead of TEE_SHM_MAPPED here?

> +	struct tee_device *teedev = ctx->teedev;
> +	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
> +	struct tee_shm *shm;
> +	void *ret;
>  
> -		mutex_lock(&teedev->mutex);
> -		shm->id = idr_alloc(&teedev->idr, shm, 1, 0, GFP_KERNEL);
> -		mutex_unlock(&teedev->mutex);
> -		if (shm->id < 0) {
> -			ret = ERR_PTR(shm->id);
> -			goto err_pool_free;
> -		}
> +	shm = shm_alloc_helper(ctx, size, PAGE_SIZE, flags);
> +	if (IS_ERR(shm))
> +		return shm;
>  
> -		exp_info.ops = &tee_shm_dma_buf_ops;
> -		exp_info.size = shm->size;
> -		exp_info.flags = O_RDWR;
> -		exp_info.priv = shm;
> +	mutex_lock(&teedev->mutex);
> +	shm->id = idr_alloc(&teedev->idr, shm, 1, 0, GFP_KERNEL);
> +	mutex_unlock(&teedev->mutex);
> +	if (shm->id < 0) {
> +		ret = ERR_PTR(shm->id);
> +		goto err_pool_free;
> +	}
>  
> -		shm->dmabuf = dma_buf_export(&exp_info);
> -		if (IS_ERR(shm->dmabuf)) {
> -			ret = ERR_CAST(shm->dmabuf);
> -			goto err_rem;
> -		}
> +	exp_info.ops = &tee_shm_dma_buf_ops;
> +	exp_info.size = shm->size;
> +	exp_info.flags = O_RDWR;
> +	exp_info.priv = shm;
> +
> +	shm->dmabuf = dma_buf_export(&exp_info);
> +	if (IS_ERR(shm->dmabuf)) {
> +		ret = ERR_CAST(shm->dmabuf);
> +		goto err_rem;
>  	}
>  
>  	teedev_ctx_get(ctx);
> -
>  	return shm;
>  err_rem:
> -	if (flags & TEE_SHM_DMA_BUF) {
> -		mutex_lock(&teedev->mutex);
> -		idr_remove(&teedev->idr, shm->id);
> -		mutex_unlock(&teedev->mutex);
> -	}
> +	mutex_lock(&teedev->mutex);
> +	idr_remove(&teedev->idr, shm->id);
> +	mutex_unlock(&teedev->mutex);
>  err_pool_free:
>  	teedev->pool->ops->free(teedev->pool, shm);
> -err_kfree:
>  	kfree(shm);
> -err_dev_put:
>  	tee_device_put(teedev);
>  	return ret;
> +
>  }
> -EXPORT_SYMBOL_GPL(tee_shm_alloc);
> +EXPORT_SYMBOL_GPL(tee_shm_alloc_user_buf);
>  
>  /**
>   * tee_shm_alloc_kernel_buf() - Allocate shared memory for kernel buffer
> @@ -206,10 +215,85 @@ EXPORT_SYMBOL_GPL(tee_shm_alloc);
>   */
>  struct tee_shm *tee_shm_alloc_kernel_buf(struct tee_context *ctx, size_t size)
>  {
> -	return tee_shm_alloc(ctx, size, TEE_SHM_MAPPED | TEE_SHM_DMA_BUF);
> +	u32 flags = TEE_SHM_MAPPED | TEE_SHM_REGISTER;

Similar question as above... why not TEE_SHM_KERNEL_MAPPED instead of
TEE_SHM_MAPPED?

> +	struct tee_shm *shm;
> +
> +	shm = shm_alloc_helper(ctx, size, PAGE_SIZE, flags);
> +	if (IS_ERR(shm))
> +		return shm;
> +
> +	teedev_ctx_get(ctx);
> +	return shm;
>  }
>  EXPORT_SYMBOL_GPL(tee_shm_alloc_kernel_buf);
>  
> +/**
> + * tee_shm_alloc_anon_kernel_buf() - Allocate shared memory for anonymous
> + *				     kernel buffer
> + * @ctx:	Context that allocates the shared memory
> + * @size:	Requested size of shared memory
> + *
> + * This function returns similar shared memory as tee_shm_alloc_kernel_buf(),
> + * but with two differences:
> + * 1. The memory might not be registered in secure world
> + *    in case the driver supports passing memory not registered in advance.
> + * 2. The memory is not directly associated with the passed tee_context,
> + *    rather the tee_device used by the context.
> + *
> + * This function should normally only be used internally in the TEE
> + * drivers. The memory must later only be freed using
> + * tee_shm_free_anon_kernel_buf() with a tee_contex with the same internal
> + * tee_device as when the memory was allocated.
> + *
> + * This allows allocating the shared memory using one context which is
> + * destroyed while the memory continues to live and finally freed using
> + * another context.
> + *
> + * @returns a pointer to 'struct tee_shm'
> + */
> +struct tee_shm *tee_shm_alloc_anon_kernel_buf(struct tee_context *ctx,
> +					      size_t size)
> +{
> +	struct tee_shm *shm;
> +
> +	shm = shm_alloc_helper(ctx, size, sizeof(long) * 2, TEE_SHM_MAPPED);

The generic TEE_SHM_MAPPED is used here, as well.

Tyler

> +	if (IS_ERR(shm))
> +		return shm;
> +
> +	shm->ctx = NULL;
> +	return shm;
> +}
> +EXPORT_SYMBOL_GPL(tee_shm_alloc_anon_kernel_buf);
> +
> +/**
> + * tee_shm_free_anon_kernel_buf() - Free anonymous shared kernel memory
> + * @ctx:	Borrowed context when freeing the shared memory
> + * @shm:	Handle to shared memory to free
> + *
> + * This function must only be used to free a tee_shm allocated with
> + * tee_shm_alloc_anon_kernel_buf(). The passed @ctx has to have the same
> + * internal tee_device as was used by the tee_context passed when the
> + * memory was allocated.
> + */
> +void tee_shm_free_anon_kernel_buf(struct tee_context *ctx, struct tee_shm *shm)
> +{
> +	struct tee_device *teedev = ctx->teedev;
> +
> +	/*
> +	 * The anonymous kernel buffer isn't attached to any tee_context
> +	 * we're instead assigning the current tee_context temporarily.
> +	 * This is needed because an eventual call to unregister the shared
> +	 * memory might need a context. As long as this context uses the
> +	 * same tee_device as in the ctx in the call in
> +	 * tee_shm_alloc_anon_kernel_buf() above we are OK.
> +	 */
> +	shm->ctx = ctx;
> +	teedev->pool->ops->free(teedev->pool, shm);
> +	kfree(shm);
> +	tee_device_put(teedev);
> +}
> +EXPORT_SYMBOL_GPL(tee_shm_free_anon_kernel_buf);
> +
>  struct tee_shm *tee_shm_register(struct tee_context *ctx, unsigned long addr,
>  				 size_t length, u32 flags)
>  {
> diff --git a/include/linux/tee_drv.h b/include/linux/tee_drv.h
> index 58b319766f8e..11a4e556bdf9 100644
> --- a/include/linux/tee_drv.h
> +++ b/include/linux/tee_drv.h
> @@ -267,22 +267,11 @@ static inline void tee_shm_pool_free(struct tee_shm_pool *pool)
>   */
>  void *tee_get_drvdata(struct tee_device *teedev);
>  
> -/**
> - * tee_shm_alloc() - Allocate shared memory
> - * @ctx:	Context that allocates the shared memory
> - * @size:	Requested size of shared memory
> - * @flags:	Flags setting properties for the requested shared memory.
> - *
> - * Memory allocated as global shared memory is automatically freed when the
> - * TEE file pointer is closed. The @flags field uses the bits defined by
> - * TEE_SHM_* above. TEE_SHM_MAPPED must currently always be set. If
> - * TEE_SHM_DMA_BUF global shared memory will be allocated and associated
> - * with a dma-buf handle, else driver private memory.
> - *
> - * @returns a pointer to 'struct tee_shm'
> - */
> -struct tee_shm *tee_shm_alloc(struct tee_context *ctx, size_t size, u32 flags);
> +struct tee_shm *tee_shm_alloc_user_buf(struct tee_context *ctx, size_t size);
>  struct tee_shm *tee_shm_alloc_kernel_buf(struct tee_context *ctx, size_t size);
> +struct tee_shm *tee_shm_alloc_anon_kernel_buf(struct tee_context *ctx,
> +					      size_t size);
> +void tee_shm_free_anon_kernel_buf(struct tee_context *ctx, struct tee_shm *shm);
>  
>  /**
>   * tee_shm_register() - Register shared memory buffer
> -- 
> 2.31.1
> 

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