Added README-morello.md to describe the experimental port..

README-morello.md

@@ -0,0 +1,75 @@
+# Background
+
+This software is an experimental Morello port of protobuf 3.20.1.
+
+## Build instructions
+
+The official build instructions fori protobuf describe building with
+`bazel`, However, as a port of bazel is not currently distributed in binary
+form for CheriBSD protobuf can instead be built with autotools:
+
+```
+$ sh autogen.sh
+$ sh configure
+$ make
+$ sudo make install
+```
+
+## Testing
+
+### Unit testing
+
+Unit testing has been performed using `make check`:
+
+```
+$ make check 
+In-address space security exception (core dumped)
+FAIL: protobuf-test
+In-address space security exception (core dumped)
+FAIL: protobuf-lazy-descriptor-test
+PASS: protobuf-lite-test
+PASS: google/protobuf/compiler/zip_output_unittest.sh
+PASS: google/protobuf/io/gzip_stream_unittest.sh
+PASS: protobuf-lite-arena-test
+PASS: no-warning-test
+============================================================================
+Testsuite summary for Protocol Buffers 3.20.1
+============================================================================
+# TOTAL: 7
+# PASS:  5
+# SKIP:  0
+# XFAIL: 0
+# FAIL:  2
+# XPASS: 0
+# ERROR: 0
+============================================================================
+See src/test-suite.log
+Please report to [email protected]
+============================================================================
+```
+
+## Notes and Limitations
+
+The unit test `protbuf-lazy-descriptor-test` is currently crashes with a
+CHERI protection fault. As many of th unit tests are passing and the its function
+was suffficient to work gRPC this issue hasn't been investigated.
+
+Adaptations to nginx to the memory-safe CheriABI have been driven by:
+compiler warnings and errors, and dynamic testing. Where the compiler
+emits a warning or error we are able to rigorously review this and
+correct. However, some issues only manifest dynamically (at runtime),
+such as invalidation of capabilities by pointer arithmetic,
+non-blessed memory copies, or insufficient pointer alignment.
+Enhancements such as CHERI UBsan have modestly improved the ability to
+identify problems previously only found during dynamic testing. However,
+ we are still greatly reliant on dynamic testing. This testing is
+constrained by both the completeness of the test suites (which in some
+cases provide poor coverage) and the time available within the project
+to perform testing. Whilst it is know that errors remain outside the
+core http module we are not able to estimate what problems might
+remain beyond those resolved in the scope of the project.
+
+## Acknowledgement
+
+This work has been undertaken within DSTL contract
+ACC6036483: CHERI-based compartmentalisation for web services on Morello.