Add Readme for PCL code sample

Signed-off-by: Yu Ding <dingelish@gmail.com>

Author: dingelish

samplecode/pcl/Readme.md

@@ -1,2 +1,41 @@
 # Protected Code Launch Sample
 
+This code sample shows how to use PCL in Rust-SGX.
+
+`pcl-user` contains logic of the user side, who wants to load encrypted enclave on a remote SGX-enabled machine.
+
+`encrypted-hello` is the code user wants to protect. It is encrypted during building process. The encryption key is dynamically generated.
+
+`pcl-seal` is a remote SGX app. It contains a sealing enclave which is in charge of storing the encryption key and provide it to the PCL API.
+
+## Build and Run
+
+To build, just type `make` and everything should be fine.
+
+To run, please put your IAS registration files (client.key, client.crt and spid.txt) in under `pcl_seal/bin/`. Then
+
+```
+$ cd pcl-seal/bin
+$ ./app
+```
+
+In another terminal, start the pcl-user app:
+
+```
+$ cd pcl-user
+$ cargo run
+```
+
+Next you'll see `pcl-seal` starts getting a report from Intel and establishes a RA-based TLS channel with `pcl-user` and gets sealed key provisioned and stored in `SgxFile`. At last, `pcl-seal` will launch the `encrypted-hello` enclave and finally print the hello message.
+
+```
+Entering get_sealed_pcl_key
+SgxFs read success: 68F6DEF27C33F248864A74D9607EA6B3
+get_sealed_pcl_key 040002000000...(suppressed)
+[+] Home dir is /root
+[-] Open token file /root/payload.token error! Will create one.
+[+] Init Enclave Successful 3!
+This is a normal world string passed into Enclave!
+This is a in-Enclave Rust string!
+[+] Done!
+```