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Date: Mon, 15 Mar 2021 10:29:10 +0100
From: Jens Wiklander <jens.wiklander@...aro.org>
To: Rijo Thomas <Rijo-john.Thomas@....com>
Cc: Dan Carpenter <dan.carpenter@...cle.com>,
Devaraj Rangasamy <Devaraj.Rangasamy@....com>,
op-tee@...ts.trustedfirmware.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tee: amdtee: unload TA only when its refcount becomes 0
On Sun, Mar 07, 2021 at 12:05:01PM +0530, Rijo Thomas wrote:
> Same Trusted Application (TA) can be loaded in multiple TEE contexts.
>
> If it is a single instance TA, the TA should not get unloaded from AMD
> Secure Processor, while it is still in use in another TEE context.
>
> Therefore reference count TA and unload it when the count becomes zero.
>
> Fixes: 757cc3e9ff1d ("tee: add AMD-TEE driver")
> Reviewed-by: Devaraj Rangasamy <Devaraj.Rangasamy@....com>
> Signed-off-by: Rijo Thomas <Rijo-john.Thomas@....com>
> ---
> drivers/tee/amdtee/amdtee_private.h | 13 +++++
> drivers/tee/amdtee/call.c | 73 +++++++++++++++++++++++++++--
> drivers/tee/amdtee/core.c | 15 +++---
> 3 files changed, 92 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/tee/amdtee/amdtee_private.h b/drivers/tee/amdtee/amdtee_private.h
> index 337c8d82f74e..6d0f7062bb87 100644
> --- a/drivers/tee/amdtee/amdtee_private.h
> +++ b/drivers/tee/amdtee/amdtee_private.h
> @@ -21,6 +21,7 @@
> #define TEEC_SUCCESS 0x00000000
> #define TEEC_ERROR_GENERIC 0xFFFF0000
> #define TEEC_ERROR_BAD_PARAMETERS 0xFFFF0006
> +#define TEEC_ERROR_OUT_OF_MEMORY 0xFFFF000C
> #define TEEC_ERROR_COMMUNICATION 0xFFFF000E
>
> #define TEEC_ORIGIN_COMMS 0x00000002
> @@ -93,6 +94,18 @@ struct amdtee_shm_data {
> u32 buf_id;
> };
>
> +/**
> + * struct amdtee_ta_data - Keeps track of all TAs loaded in AMD Secure
> + * Processor
> + * @ta_handle: Handle to TA loaded in TEE
> + * @refcount: Reference count for the loaded TA
> + */
> +struct amdtee_ta_data {
> + struct list_head list_node;
> + u32 ta_handle;
> + u32 refcount;
> +};
> +
> #define LOWER_TWO_BYTE_MASK 0x0000FFFF
>
> /**
> diff --git a/drivers/tee/amdtee/call.c b/drivers/tee/amdtee/call.c
> index 096dd4d92d39..e10601417ea3 100644
> --- a/drivers/tee/amdtee/call.c
> +++ b/drivers/tee/amdtee/call.c
> @@ -121,15 +121,69 @@ static int amd_params_to_tee_params(struct tee_param *tee, u32 count,
> return ret;
> }
>
> +static DEFINE_MUTEX(ta_refcount_mutex);
> +static struct list_head ta_list = LIST_HEAD_INIT(ta_list);
> +
> +static u32 get_ta_refcount(u32 ta_handle)
> +{
> + struct amdtee_ta_data *ta_data;
> + u32 count = 0;
> +
> + /* Caller must hold a mutex */
> + list_for_each_entry(ta_data, &ta_list, list_node)
> + if (ta_data->ta_handle == ta_handle)
> + return ++ta_data->refcount;
> +
> + ta_data = kzalloc(sizeof(*ta_data), GFP_KERNEL);
> + if (ta_data) {
> + ta_data->ta_handle = ta_handle;
> + ta_data->refcount = 1;
> + count = ta_data->refcount;
> + list_add(&ta_data->list_node, &ta_list);
> + }
> +
> + return count;
> +}
> +
> +static u32 put_ta_refcount(u32 ta_handle)
> +{
> + struct amdtee_ta_data *ta_data;
> + u32 count = 0;
> +
> + /* Caller must hold a mutex */
> + list_for_each_entry(ta_data, &ta_list, list_node)
> + if (ta_data->ta_handle == ta_handle) {
> + count = --ta_data->refcount;
> + if (count == 0) {
> + list_del(&ta_data->list_node);
> + kfree(ta_data);
> + break;
> + }
> + }
> +
> + return count;
> +}
> +
> int handle_unload_ta(u32 ta_handle)
> {
> struct tee_cmd_unload_ta cmd = {0};
> - u32 status;
> + u32 status, count;
> int ret;
>
> if (!ta_handle)
> return -EINVAL;
>
> + mutex_lock(&ta_refcount_mutex);
> +
> + count = put_ta_refcount(ta_handle);
> +
> + if (count) {
> + pr_debug("unload ta: not unloading %u count %u\n",
> + ta_handle, count);
> + ret = -EBUSY;
> + goto unlock;
> + }
> +
> cmd.ta_handle = ta_handle;
>
> ret = psp_tee_process_cmd(TEE_CMD_ID_UNLOAD_TA, (void *)&cmd,
> @@ -137,8 +191,12 @@ int handle_unload_ta(u32 ta_handle)
> if (!ret && status != 0) {
> pr_err("unload ta: status = 0x%x\n", status);
> ret = -EBUSY;
> + } else {
> + pr_debug("unloaded ta handle %u\n", ta_handle);
> }
>
> +unlock:
> + mutex_unlock(&ta_refcount_mutex);
> return ret;
> }
>
> @@ -357,14 +415,23 @@ int handle_load_ta(void *data, u32 size, struct tee_ioctl_open_session_arg *arg)
> cmd.low_addr = lower_32_bits(blob);
> cmd.size = size;
>
> + mutex_lock(&ta_refcount_mutex);
> +
> ret = psp_tee_process_cmd(TEE_CMD_ID_LOAD_TA, (void *)&cmd,
> sizeof(cmd), &arg->ret);
> if (ret) {
> arg->ret_origin = TEEC_ORIGIN_COMMS;
> arg->ret = TEEC_ERROR_COMMUNICATION;
> - } else {
> - set_session_id(cmd.ta_handle, 0, &arg->session);
> + } else if (arg->ret == TEEC_SUCCESS) {
> + ret = get_ta_refcount(cmd.ta_handle);
> + if (!ret) {
If this occurs, how is the TA unloaded from secure world?
Thanks,
Jens
> + arg->ret_origin = TEEC_ORIGIN_COMMS;
> + arg->ret = TEEC_ERROR_OUT_OF_MEMORY;
> + } else {
> + set_session_id(cmd.ta_handle, 0, &arg->session);
> + }
> }
> + mutex_unlock(&ta_refcount_mutex);
>
> pr_debug("load TA: TA handle = 0x%x, RO = 0x%x, ret = 0x%x\n",
> cmd.ta_handle, arg->ret_origin, arg->ret);
> diff --git a/drivers/tee/amdtee/core.c b/drivers/tee/amdtee/core.c
> index 8a6a8f30bb42..da6b88e80dc0 100644
> --- a/drivers/tee/amdtee/core.c
> +++ b/drivers/tee/amdtee/core.c
> @@ -59,10 +59,9 @@ static void release_session(struct amdtee_session *sess)
> continue;
>
> handle_close_session(sess->ta_handle, sess->session_info[i]);
> + handle_unload_ta(sess->ta_handle);
> }
>
> - /* Unload Trusted Application once all sessions are closed */
> - handle_unload_ta(sess->ta_handle);
> kfree(sess);
> }
>
> @@ -224,8 +223,6 @@ static void destroy_session(struct kref *ref)
> struct amdtee_session *sess = container_of(ref, struct amdtee_session,
> refcount);
>
> - /* Unload the TA from TEE */
> - handle_unload_ta(sess->ta_handle);
> mutex_lock(&session_list_mutex);
> list_del(&sess->list_node);
> mutex_unlock(&session_list_mutex);
> @@ -238,7 +235,7 @@ int amdtee_open_session(struct tee_context *ctx,
> {
> struct amdtee_context_data *ctxdata = ctx->data;
> struct amdtee_session *sess = NULL;
> - u32 session_info;
> + u32 session_info, ta_handle;
> size_t ta_size;
> int rc, i;
> void *ta;
> @@ -259,11 +256,14 @@ int amdtee_open_session(struct tee_context *ctx,
> if (arg->ret != TEEC_SUCCESS)
> goto out;
>
> + ta_handle = get_ta_handle(arg->session);
> +
> mutex_lock(&session_list_mutex);
> sess = alloc_session(ctxdata, arg->session);
> mutex_unlock(&session_list_mutex);
>
> if (!sess) {
> + handle_unload_ta(ta_handle);
> rc = -ENOMEM;
> goto out;
> }
> @@ -277,6 +277,7 @@ int amdtee_open_session(struct tee_context *ctx,
>
> if (i >= TEE_NUM_SESSIONS) {
> pr_err("reached maximum session count %d\n", TEE_NUM_SESSIONS);
> + handle_unload_ta(ta_handle);
> kref_put(&sess->refcount, destroy_session);
> rc = -ENOMEM;
> goto out;
> @@ -289,12 +290,13 @@ int amdtee_open_session(struct tee_context *ctx,
> spin_lock(&sess->lock);
> clear_bit(i, sess->sess_mask);
> spin_unlock(&sess->lock);
> + handle_unload_ta(ta_handle);
> kref_put(&sess->refcount, destroy_session);
> goto out;
> }
>
> sess->session_info[i] = session_info;
> - set_session_id(sess->ta_handle, i, &arg->session);
> + set_session_id(ta_handle, i, &arg->session);
> out:
> free_pages((u64)ta, get_order(ta_size));
> return rc;
> @@ -329,6 +331,7 @@ int amdtee_close_session(struct tee_context *ctx, u32 session)
>
> /* Close the session */
> handle_close_session(ta_handle, session_info);
> + handle_unload_ta(ta_handle);
>
> kref_put(&sess->refcount, destroy_session);
>
> --
> 2.17.1
>
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