[PATCH 2/3] optee: add FF-A capability OPTEE_FFA_SEC_CAP_ARG_OFFSET

From: Jens Wiklander
Date: Tue Mar 01 2022 - 14:50:08 EST


Adds the secure capability OPTEE_FFA_SEC_CAP_ARG_OFFSET to indicate that
OP-TEE with FF-A can support an argument struct at a non-zero offset into
a passed shared memory object.

Signed-off-by: Jens Wiklander <jens.wiklander@xxxxxxxxxx>
---
drivers/tee/optee/ffa_abi.c | 17 +++++++++++++++--
drivers/tee/optee/optee_ffa.h | 12 +++++++++++-
2 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/drivers/tee/optee/ffa_abi.c b/drivers/tee/optee/ffa_abi.c
index 7686f7020616..cc863aaefcd9 100644
--- a/drivers/tee/optee/ffa_abi.c
+++ b/drivers/tee/optee/ffa_abi.c
@@ -615,12 +615,21 @@ static int optee_ffa_do_call_with_arg(struct tee_context *ctx,
.data0 = OPTEE_FFA_YIELDING_CALL_WITH_ARG,
.data1 = (u32)shm->sec_world_id,
.data2 = (u32)(shm->sec_world_id >> 32),
- .data3 = shm->offset,
+ .data3 = 0,
};
struct optee_msg_arg *arg;
unsigned int rpc_arg_offs;
struct optee_msg_arg *rpc_arg;

+ /*
+ * The shared memory object has to start on a page when passed as
+ * an argument struct. This is also what the shm pool allocator
+ * returns, but check this before calling secure world to catch
+ * eventual errors early in case something changes.
+ */
+ if (shm->offset)
+ return -EINVAL;
+
arg = tee_shm_get_va(shm, 0);
if (IS_ERR(arg))
return PTR_ERR(arg);
@@ -678,6 +687,7 @@ static bool optee_ffa_api_is_compatbile(struct ffa_device *ffa_dev,

static bool optee_ffa_exchange_caps(struct ffa_device *ffa_dev,
const struct ffa_dev_ops *ops,
+ u32 *sec_caps,
unsigned int *rpc_param_count)
{
struct ffa_send_direct_data data = { OPTEE_FFA_EXCHANGE_CAPABILITIES };
@@ -694,6 +704,7 @@ static bool optee_ffa_exchange_caps(struct ffa_device *ffa_dev,
}

*rpc_param_count = (u8)data.data1;
+ *sec_caps = data.data2;

return true;
}
@@ -777,6 +788,7 @@ static int optee_ffa_probe(struct ffa_device *ffa_dev)
struct tee_device *teedev;
struct tee_context *ctx;
struct optee *optee;
+ u32 sec_caps;
int rc;

ffa_ops = ffa_dev_ops_get(ffa_dev);
@@ -788,7 +800,8 @@ static int optee_ffa_probe(struct ffa_device *ffa_dev)
if (!optee_ffa_api_is_compatbile(ffa_dev, ffa_ops))
return -EINVAL;

- if (!optee_ffa_exchange_caps(ffa_dev, ffa_ops, &rpc_param_count))
+ if (!optee_ffa_exchange_caps(ffa_dev, ffa_ops, &sec_caps,
+ &rpc_param_count))
return -EINVAL;

optee = kzalloc(sizeof(*optee), GFP_KERNEL);
diff --git a/drivers/tee/optee/optee_ffa.h b/drivers/tee/optee/optee_ffa.h
index ee3a03fc392c..97266243deaa 100644
--- a/drivers/tee/optee/optee_ffa.h
+++ b/drivers/tee/optee/optee_ffa.h
@@ -81,8 +81,16 @@
* as the second MSG arg struct for
* OPTEE_FFA_YIELDING_CALL_WITH_ARG.
* Bit[31:8]: Reserved (MBZ)
- * w5-w7: Note used (MBZ)
+ * w5: Bitfield of secure world capabilities OPTEE_FFA_SEC_CAP_* below,
+ * unused bits MBZ.
+ * w6-w7: Not used (MBZ)
+ */
+/*
+ * Secure world supports giving an offset into the argument shared memory
+ * object, see also OPTEE_FFA_YIELDING_CALL_WITH_ARG
*/
+#define OPTEE_FFA_SEC_CAP_ARG_OFFSET BIT(0)
+
#define OPTEE_FFA_EXCHANGE_CAPABILITIES OPTEE_FFA_BLOCKING_CALL(2)

/*
@@ -112,6 +120,8 @@
* OPTEE_MSG_GET_ARG_SIZE(num_params) follows a struct optee_msg_arg
* for RPC, this struct has reserved space for the number of RPC
* parameters as returned by OPTEE_FFA_EXCHANGE_CAPABILITIES.
+ * MBZ unless the bit OPTEE_FFA_SEC_CAP_ARG_OFFSET is received with
+ * OPTEE_FFA_EXCHANGE_CAPABILITIES.
* w7: Not used (MBZ)
* Resume from RPC. Register usage:
* w3: Service ID, OPTEE_FFA_YIELDING_CALL_RESUME
--
2.31.1