[Xen-devel] [PATCH v6 08/10] xen/arm: optee: add support for RPC commands

[Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>]

OP-TEE can issue multiple RPC requests. We are interested mostly in
request that asks NW to allocate/free shared memory for OP-TEE
needs, because mediator needs to do address translation in the same
way as it was done for shared buffers registered by NW.

OP-TEE can ask NW to allocate multiple buffers during the call.  We
know that if OP-TEE asks for another buffer, we can free pglist for
the previous one.

As mediator now accesses shared command buffer, we need to shadow
it in the same way, as we shadow request buffers for STD calls.
Earlier, we just passed address of this buffer to OP-TEE, but
now we need to read and write to it, so it should be shadowed.

Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@epam.com>
Acked-by: Julien Grall <julien.grall@arm.com>

---
 All the patches to optee.c should be merged together. They were
 split to ease up review. But they depend heavily on each other.

 Changes from v5:
 - There was change to RPC command names, because of different
   header file was used (see comments to patch 2 "xen/arm: optee:
   add OP-TEE header files"). This is non-functional change.

 Changes from v3:
 - return value of access_guest_memory_by_ipa() now checked
 - changed how information about shared buffer is stored in call
   context
 - domheap now used instead of xenheap
 - various coding style fixes

 Changes from v2:
 - Use access_guest_memory_by_ipa() instead of direct mapping
---
 xen/arch/arm/tee/optee.c | 230 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 223 insertions(+), 7 deletions(-)

diff --git a/xen/arch/arm/tee/optee.c b/xen/arch/arm/tee/optee.c
index d4888acd8d..28d34360fc 100644
--- a/xen/arch/arm/tee/optee.c
+++ b/xen/arch/arm/tee/optee.c
@@ -36,6 +36,7 @@
 #include <asm/tee/tee.h>
 #include <asm/tee/optee_msg.h>
 #include <asm/tee/optee_smc.h>
+#include <asm/tee/optee_rpc_cmd.h>
 
 /* Number of SMCs known to the mediator */
 #define OPTEE_MEDIATOR_SMC_COUNT   11
@@ -47,6 +48,9 @@
  */
 #define TEEC_ORIGIN_COMMS 0x00000002
 
+/* "Non-specific cause" as in GP TEE Client API Specification */
+#define TEEC_ERROR_GENERIC 0xFFFF0000
+
 /*
  * "Input parameters were invalid" as described
  * in GP TEE Client API Specification.
@@ -89,6 +93,7 @@ struct optee_std_call {
     paddr_t guest_arg_ipa;
     int optee_thread_id;
     int rpc_op;
+    uint64_t rpc_data_cookie;
     bool in_flight;
     register_t rpc_params[2];
 };
@@ -97,6 +102,9 @@ struct optee_std_call {
 struct shm_rpc {
     struct list_head list;
     struct page_info *guest_page;
+    struct page_info *xen_arg_pg;
+    struct optee_msg_arg *xen_arg;
+    gfn_t gfn;
     uint64_t cookie;
 };
 
@@ -350,10 +358,18 @@ static struct shm_rpc *allocate_and_pin_shm_rpc(struct optee_domain *ctx,
     if ( !shm_rpc )
         return ERR_PTR(-ENOMEM);
 
+    shm_rpc->xen_arg_pg = alloc_domheap_page(current->domain, 0);
+    if ( !shm_rpc->xen_arg_pg )
+    {
+        xfree(shm_rpc);
+        return ERR_PTR(-ENOMEM);
+    }
+
     /* This page will be shared with OP-TEE, so we need to pin it. */
     shm_rpc->guest_page = get_domain_ram_page(gfn);
     if ( !shm_rpc->guest_page )
         goto err;
+    shm_rpc->gfn = gfn;
 
     shm_rpc->cookie = cookie;
 
@@ -376,6 +392,8 @@ static struct shm_rpc *allocate_and_pin_shm_rpc(struct optee_domain *ctx,
     return shm_rpc;
 
 err:
+    free_domheap_page(shm_rpc->xen_arg_pg);
+
     if ( shm_rpc->guest_page )
         put_page(shm_rpc->guest_page);
     xfree(shm_rpc);
@@ -404,12 +422,32 @@ static void free_shm_rpc(struct optee_domain *ctx, uint64_t cookie)
     if ( !found )
         return;
 
+    free_domheap_page(shm_rpc->xen_arg_pg);
+
     ASSERT(shm_rpc->guest_page);
     put_page(shm_rpc->guest_page);
 
     xfree(shm_rpc);
 }
 
+static struct shm_rpc *find_shm_rpc(struct optee_domain *ctx, uint64_t cookie)
+{
+    struct shm_rpc *shm_rpc;
+
+    spin_lock(&ctx->lock);
+    list_for_each_entry( shm_rpc, &ctx->shm_rpc_list, list )
+    {
+        if ( shm_rpc->cookie == cookie )
+        {
+                spin_unlock(&ctx->lock);
+                return shm_rpc;
+        }
+    }
+    spin_unlock(&ctx->lock);
+
+    return NULL;
+}
+
 static struct optee_shm_buf *allocate_optee_shm_buf(struct optee_domain *ctx,
                                                     uint64_t cookie,
                                                     unsigned int pages_cnt,
@@ -931,10 +969,13 @@ static void free_shm_buffers(struct optee_domain *ctx,
 }
 
 /* Handle RPC return from OP-TEE */
-static void handle_rpc_return(struct arm_smccc_res *res,
-                              struct cpu_user_regs *regs,
-                              struct optee_std_call *call)
+static int handle_rpc_return(struct optee_domain *ctx,
+                             struct arm_smccc_res *res,
+                             struct cpu_user_regs *regs,
+                             struct optee_std_call *call)
 {
+    int ret = 0;
+
     call->rpc_op = OPTEE_SMC_RETURN_GET_RPC_FUNC(res->a0);
     call->rpc_params[0] = res->a1;
     call->rpc_params[1] = res->a2;
@@ -944,6 +985,51 @@ static void handle_rpc_return(struct arm_smccc_res *res,
     set_user_reg(regs, 1, res->a1);
     set_user_reg(regs, 2, res->a2);
     set_user_reg(regs, 3, res->a3);
+
+    if ( call->rpc_op == OPTEE_SMC_RPC_FUNC_CMD )
+    {
+        /* Copy RPC request from shadowed buffer to guest */
+        uint64_t cookie = regpair_to_uint64(get_user_reg(regs, 1),
+                                            get_user_reg(regs, 2));
+        struct shm_rpc *shm_rpc = find_shm_rpc(ctx, cookie);
+
+        if ( !shm_rpc )
+        {
+            /*
+             * This is a very exceptional situation: OP-TEE used
+             * cookie for unknown shared buffer. Something is very
+             * wrong there. We can't even report error back to OP-TEE,
+             * because there is no buffer where we can write return
+             * code. Luckily, OP-TEE sets default error code into that
+             * buffer before the call, expecting that normal world
+             * will overwrite it with actual result. So we can just
+             * continue the call.
+             */
+            gprintk(XENLOG_ERR, "Can't find SHM-RPC with cookie %lx\n", cookie);
+
+            return -ERESTART;
+        }
+
+        shm_rpc->xen_arg = __map_domain_page(shm_rpc->xen_arg_pg);
+
+        if ( access_guest_memory_by_ipa(current->domain,
+                        gfn_to_gaddr(shm_rpc->gfn),
+                        shm_rpc->xen_arg,
+                        OPTEE_MSG_GET_ARG_SIZE(shm_rpc->xen_arg->num_params),
+                        true) )
+        {
+            /*
+             * We were unable to propagate request to guest, so let's return
+             * back to OP-TEE.
+             */
+            shm_rpc->xen_arg->ret = TEEC_ERROR_GENERIC;
+            ret = -ERESTART;
+        }
+
+        unmap_domain_page(shm_rpc->xen_arg);
+    }
+
+    return ret;
 }
 
 /*
@@ -956,6 +1042,9 @@ static void handle_rpc_return(struct arm_smccc_res *res,
  * If call is complete - we need to return results with copy_std_request_back()
  * and then we will destroy the call context as it is not needed anymore.
  *
+ * In some rare cases we can't propagate RPC request back to guest, so we will
+ * restart the call, telling OP-TEE that request had failed.
+ *
  * Shared buffers should be handled in a special way.
  */
 static void do_call_with_arg(struct optee_domain *ctx,
@@ -971,7 +1060,16 @@ static void do_call_with_arg(struct optee_domain *ctx,
 
     if ( OPTEE_SMC_RETURN_IS_RPC(res.a0) )
     {
-        handle_rpc_return(&res, regs, call);
+        while ( handle_rpc_return(ctx, &res, regs, call)  == -ERESTART )
+        {
+            arm_smccc_smc(res.a0, res.a1, res.a2, res.a3, 0, 0, 0,
+                          OPTEE_CLIENT_ID(current->domain), &res);
+
+            if ( !OPTEE_SMC_RETURN_IS_RPC(res.a0) )
+                break;
+
+        }
+
         put_std_call(ctx, call);
 
         return;
@@ -1097,6 +1195,124 @@ err:
  * request from OP-TEE and wished to resume the interrupted standard
  * call.
  */
+static void handle_rpc_cmd_alloc(struct optee_domain *ctx,
+                                 struct cpu_user_regs *regs,
+                                 struct optee_std_call *call,
+                                 struct shm_rpc *shm_rpc)
+{
+    if ( shm_rpc->xen_arg->ret || shm_rpc->xen_arg->num_params != 1 )
+        return;
+
+    if ( shm_rpc->xen_arg->params[0].attr != (OPTEE_MSG_ATTR_TYPE_TMEM_OUTPUT |
+                                              OPTEE_MSG_ATTR_NONCONTIG) )
+    {
+        gdprintk(XENLOG_WARNING, "Invalid attrs for shared mem buffer: %lx\n",
+                 shm_rpc->xen_arg->params[0].attr);
+        return;
+    }
+
+    /* Free pg list for buffer */
+    if ( call->rpc_data_cookie )
+        free_optee_shm_buf_pg_list(ctx, call->rpc_data_cookie);
+
+    if ( !translate_noncontig(ctx, call, &shm_rpc->xen_arg->params[0]) )
+    {
+        call->rpc_data_cookie =
+            shm_rpc->xen_arg->params[0].u.tmem.shm_ref;
+    }
+    else
+    {
+        call->rpc_data_cookie = 0;
+        /*
+         * Okay, so there was problem with guest's buffer and we need
+         * to tell about this to OP-TEE.
+         */
+        shm_rpc->xen_arg->ret = TEEC_ERROR_GENERIC;
+        shm_rpc->xen_arg->num_params = 0;
+        /*
+         * TODO: With current implementation, OP-TEE will not issue
+         * RPC to free this buffer. Guest and OP-TEE will be out of
+         * sync: guest believes that it provided buffer to OP-TEE,
+         * while OP-TEE thinks of opposite. Ideally, we need to
+         * emulate RPC with OPTEE_MSG_RPC_CMD_SHM_FREE command.
+         */
+        gprintk(XENLOG_WARNING,
+                "translate_noncontig() failed, OP-TEE/guest state is out of sync.\n");
+    }
+}
+
+static void handle_rpc_cmd(struct optee_domain *ctx, struct cpu_user_regs *regs,
+                           struct optee_std_call *call)
+{
+    struct shm_rpc *shm_rpc;
+    uint64_t cookie;
+    size_t arg_size;
+
+    cookie = regpair_to_uint64(get_user_reg(regs, 1),
+                               get_user_reg(regs, 2));
+
+    shm_rpc = find_shm_rpc(ctx, cookie);
+
+    if ( !shm_rpc )
+    {
+        gdprintk(XENLOG_ERR, "Can't find SHM-RPC with cookie %lx\n", cookie);
+        return;
+    }
+
+    shm_rpc->xen_arg = __map_domain_page(shm_rpc->xen_arg_pg);
+
+    /* First, copy only header to read number of arguments */
+    if ( access_guest_memory_by_ipa(current->domain,
+                                    gfn_to_gaddr(shm_rpc->gfn),
+                                    shm_rpc->xen_arg,
+                                    sizeof(struct optee_msg_arg),
+                                    false) )
+    {
+        shm_rpc->xen_arg->ret = TEEC_ERROR_GENERIC;
+        goto out;
+    }
+
+    arg_size = OPTEE_MSG_GET_ARG_SIZE(shm_rpc->xen_arg->num_params);
+    if ( arg_size > OPTEE_MSG_NONCONTIG_PAGE_SIZE )
+    {
+        shm_rpc->xen_arg->ret = TEEC_ERROR_GENERIC;
+        goto out;
+    }
+
+    /* Read the whole command structure */
+    if ( access_guest_memory_by_ipa(current->domain, gfn_to_gaddr(shm_rpc->gfn),
+                                    shm_rpc->xen_arg, arg_size, false) )
+    {
+        shm_rpc->xen_arg->ret = TEEC_ERROR_GENERIC;
+        goto out;
+    }
+
+    switch (shm_rpc->xen_arg->cmd)
+    {
+    case OPTEE_RPC_CMD_GET_TIME:
+    case OPTEE_RPC_CMD_WAIT_QUEUE:
+    case OPTEE_RPC_CMD_SUSPEND:
+        break;
+    case OPTEE_RPC_CMD_SHM_ALLOC:
+        handle_rpc_cmd_alloc(ctx, regs, call, shm_rpc);
+        break;
+    case OPTEE_RPC_CMD_SHM_FREE:
+        free_optee_shm_buf(ctx, shm_rpc->xen_arg->params[0].u.value.b);
+        if ( call->rpc_data_cookie == shm_rpc->xen_arg->params[0].u.value.b )
+            call->rpc_data_cookie = 0;
+        break;
+    default:
+        break;
+    }
+
+out:
+    unmap_domain_page(shm_rpc->xen_arg);
+
+    do_call_with_arg(ctx, call, regs, OPTEE_SMC_CALL_RETURN_FROM_RPC, 0, 0,
+                     get_user_reg(regs, 3), 0, 0);
+
+}
+
 static void handle_rpc_func_alloc(struct optee_domain *ctx,
                                   struct cpu_user_regs *regs,
                                   struct optee_std_call *call)
@@ -1128,7 +1344,7 @@ static void handle_rpc_func_alloc(struct optee_domain *ctx,
         ptr = 0;
     }
     else
-        ptr = page_to_maddr(shm_rpc->guest_page);
+        ptr = page_to_maddr(shm_rpc->xen_arg_pg);
 
 out:
     uint64_to_regpair(&r1, &r2, ptr);
@@ -1174,8 +1390,8 @@ static void handle_rpc(struct optee_domain *ctx, struct cpu_user_regs *regs)
     case OPTEE_SMC_RPC_FUNC_FOREIGN_INTR:
         break;
     case OPTEE_SMC_RPC_FUNC_CMD:
-        /* TODO: Add handling */
-        break;
+        handle_rpc_cmd(ctx, regs, call);
+        return;
     }
 
     do_call_with_arg(ctx, call, regs, OPTEE_SMC_CALL_RETURN_FROM_RPC,
-- 
2.21.0

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