docs(spmc): threat model document

Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
Change-Id: Ib5f443a6997239d6ba4655d7df6c3fc61d45f991

docs/resources/diagrams/plantuml/spm_dfd.puml

+/'
+ ' Copyright (c) 2021, Arm Limited. All rights reserved.
+ '
+ ' SPDX-License-Identifier: BSD-3-Clause
+ '/
+
+/'
+TF-A SPMC Data Flow Diagram
+'/
+
+@startuml
+digraph tfa_dfd {
+
+    # Allow arrows to end on cluster boundaries
+    compound=true
+
+    # Default settings for edges and nodes
+    edge [minlen=2 color="#8c1b07"]
+    node [fillcolor="#ffb866" style=filled shape=box fixedsize=true width=1.6 height=0.7]
+
+    # Nodes outside of the trust boundary
+    nsec [label="NS Client"]
+    ddr  [label="External memory (DDR)"]
+
+    # Trust boundary cluster
+    subgraph cluster_trusted {
+        graph [style=dashed color="#f22430"]
+
+        # HW IPs cluster
+        subgraph cluster_ip {
+            label ="Hardware IPs";
+            graph [style=filled color="#000000" fillcolor="#ffd29e"]
+
+            rank="same"
+            gic [label="GIC" width=1.2 height=0.5]
+            smmu [label="SMMU" width=1.2 height=0.5]
+            uart [label="UART" width=1.2 height=0.5]
+	    pe [label="PE" width=1.2 height=0.5]
+        }
+
+        # TF-A cluster
+        subgraph cluster_tfa {
+            label ="EL3 monitor";
+            graph [style=filled color="#000000" fillcolor="#faf9cd"]
+
+            bl31 [label="BL31" fillcolor="#ddffb3"];
+            spmd [label="SPMD" fillcolor="#ddffb3" height=1]
+        }
+
+        # SPMC cluster
+        subgraph cluster_spmc {
+            label ="SPMC";
+            graph [style=filled color="#000000" fillcolor="#faf9cd"]
+
+            spmc [label="SPMC" fillcolor="#ddffb3" height=1]
+        }
+	bl2 [label="BL2" width=1.2 height=0.5]
+    }
+
+    # Secure Partitions cluster
+    subgraph cluster_sp {
+        label ="Secure Partitions";
+        graph [style=filled color="#000000" fillcolor="#faf9cd"]
+
+        sp1 [label="SP1" fillcolor="#ddffb3" height=1]
+        sp2 [label="SP2" fillcolor="#ddffb3" height=1]
+        spn [label="SP..." fillcolor="#ddffb3" height=1]
+    }
+
+    # Interactions between nodes
+    sp1 -> spmc [dir="both" label="DF1"]
+    spmc -> spmd [dir="both" label="DF2"]
+    spmd -> nsec [dir="both" label="DF3"]
+    sp1 -> sp2 [dir="both" label="DF4"]
+    spmc -> smmu [lhead=cluster_spmc label="DF5"]
+    bl2 -> spmc [lhead=cluster_spmc label="DF6"]
+    bl2 -> spn [lhead=cluster_spmc label="DF6"]
+    sp1 -> ddr [dir="both"  label="DF7"]
+    spmc -> ddr [dir="both"  label="DF7"]
+}
+
+@enduml

docs/threat_model/index.rst

 Threat Model
-=============
+============
+
+Threat modeling is an important part of Secure Development Lifecycle (SDL)
+that helps us identify potential threats and mitigations affecting a system.
+
+In the next sections, we first give a description of the target of evaluation
+using a data flow diagram. Then we provide a list of threats we have identified
+based on the data flow diagram and potential threat mitigations.
 
 .. toctree::
    :maxdepth: 1
@@ -7,6 +14,7 @@ Threat Model
    :numbered:
 
    threat_model
+   threat_model_spm
 
 --------------
 

docs/threat_model/threat_model.rst

-*****************
+Generic threat model
+********************
+
+************************
 Introduction
-*****************
-Threat modeling is an important part of Secure Development Lifecycle (SDL)
-that helps us identify potential threats and mitigations affecting a system.
-
-This document provides a generic threat model for TF-A firmware. In the
-next sections, we first give a description of the target of evaluation
-using a data flow diagram. Then we provide a list of threats we have
-identified based on the data flow diagram and potential threat mitigations.
+************************
+This document provides a generic threat model for TF-A firmware.
 
 ************************
 Target of Evaluation