
Build and Port WAMR vmcore (iwasm) for Linux SGX
================================================

Build WAMR vmcore (iwasm) for Linux SGX
---------------------------------------

First of all please install the [Intel SGX SDK](https://software.intel.com/en-us/sgx/sdk), v2.8 or later is required, and it is recommended to install the SDK to /opt/intel/sgxsdk.

After installing the dependencies, build the source code:
``` Bash
source <SGX_SDK dir>/environment
cd product-mini/platforms/linux-sgx/
mkdir build
cd build
cmake ..
make
```

This builds two libraries required by SGX application:
 - libvmlib.a for Enclave part
 - libvmlib_untrusted.a for App part

**Note:** WAMR provides some features which can be easily configured by passing options to cmake, please see [WAMR vmcore cmake building configurations](./build_wamr.md#wamr-vmcore-cmake-building-configurations) for the details. Currently in Linux SGX, fast interpreter, AOT, libc-builtin, libc-WASI and lib-pthread are enabled by default.

Then build the enclave sample:
``` Bash
source <SGX_SDK dir>/environment
cd enclave-sample
make
```

The binary file iwasm will be generated. To run the sample:

``` Bash
source <SGX_SDK dir>/environment
iwasm [-options] wasm_file [args...]
or:
iwasm [-options] aot_file [args...]
```

### Minimal build
The libc-WASI and lib-pthread features require a lot of ocalls, if you don't need so much ocalls in your application, you can use the `minimal` version

``` Bash
# replace the build files with minimal version
cd product-mini/platforms/linux-sgx/
cp CMakeLists_minimal.txt CMakeLists.txt
cp enclave-sample/Makefile_minimal enclave-sample/Makefile
cp enclave-sample/Enclave/Enclave_minimal.edl enclave-sample/Enclave/Enclave.edl
# follow the building process above
```

Port WAMR vmcore for Linux SGX
------------------------------

The enclave-sample creates a sample to embed wamr vmlib of Enclave part and App part to an SGX application. To port WAMR vmcore lib to SGX application, there are some steps to do:

**Step 1: Add "sgx_wamr.edl" and "sgx_pthread.edl" into EDL file, e.g. Enclave.edl:**
> This step is not required in minimal version

```bash
from "sgx_pthread.edl" import *;
from "sgx_wamr.edl" import *;
```

The sgx_wamr.edl is under ${WAMR_ROOT}/core/shared/platform/linux-sgx, so please **add it to the search path list** when generating Enclave_u.c and Enclave_t.c from Enclave.edl:

```bash
@cd App && $(SGX_EDGER8R) --untrusted ../Enclave/Enclave.edl \
        --search-path ../Enclave \
        --search-path $(SGX_SDK)/include \
        --search-path $(WAMR_ROOT)/core/shared/platform/linux-sgx
```

```bash
@cd Enclave && $(SGX_EDGER8R) --trusted ../Enclave/Enclave.edl \
        --search-path ../Enclave \
        --search-path $(SGX_SDK)/include \
        --search-path $(WAMR_ROOT)/core/shared/platform/linux-sgx
```

**Step 2: Link libvmlib.a to Enclave part and link libvmlib_untrusted.a to App part:**
> libvmlib_untrusted.a is not required in minimal version

```makefile
Enclave_Link_Flags := ... libvmlib.a ...
```

```makefile
App_Link_Flags := ... libvmlib_untrusted.a ...
```

**And link SGX pthread lib to Enclave part:**
> SGX pthread lib is not required in minimal version

```makefile
Enclave_Link_Flags := ... -lsgx_pthread ...
```

**Step 3: Add WAMR folders and SGX SDK folders to Enclave include path:**

```makefile
Enclave_Include_Paths := ... -I$(WAMR_ROOT)/core/iwasm/include \
                         -I$(WAMR_ROOT)/core/shared/utils \
                         -I$(WAMR_ROOT)/core/shared/platform/linux-sgx \
                         -I$(SGX_SDK)/include \
                         -I$(SGX_SDK)/include/tlibc \
                         -I$(SGX_SDK)/include/stlport
```

**Step 4: Configure reserved memory and thread info in file Enclave config file (e.g. Enclave.config.xml) to support WAMR AOT and multi-thread, e.g:**

```xml
<ReservedMemMaxSize>0x400000</ReservedMemMaxSize>
<ReservedMemExecutable>1</ReservedMemExecutable>
<TCSNum>10</TCSNum>
```

**Step 5: To support log output and os_printf() function in Enclave, please implement an ocall_print function, e.g. in Enclave.edl, add:**

```cpp
untrusted {
    void ocall_print([in, string]const char* str);
};
```

In App part, add:

```cpp
void
ocall_print(const char* str)
{
    printf("%s", str);
}
```

And in Enclave part, set the print function:

```cpp
#include "wasm_export.h"
#include "bh_platform.h"

extern "C" {
    typedef void (*os_print_function_t)(const char* message);
    extern void os_set_print_function(os_print_function_t pf);

    void
    enclave_print(const char *message)
    {
        ocall_print(message);
    }
}

// In the beginning of Enclave initialization, add:
os_set_print_function(enclave_print);
```

Embed WAMR vmcore in Linux SGX
------------------------------

Normally we can embed WAMR vmcore in Linux SGX by calling the vmcore exported API's, see [Embed WAMR guide](./embed_wamr.md) for the details. And the the ecall_iwasm_main() function in file Enclave.cpp of enclave-sample also provides sample to invoke wasm app main function with wasm file buffer:

```cpp
void
ecall_iwasm_main(uint8_t *wasm_file_buf, uint32_t wasm_file_size);
```

The enclave-sample also wraps an ecall function to receive commands from App to Enclave, and handle the commands in Enclave by calling the related WAMR vmcore API. The commands and related API's are:

```cpp
typedef enum EcallCmd {
    CMD_INIT_RUNTIME = 0,     /* wasm_runtime_init/full_init() */
    CMD_LOAD_MODULE,          /* wasm_runtime_load() */
    CMD_INSTANTIATE_MODULE,   /* wasm_runtime_instantiate() */
    CMD_LOOKUP_FUNCTION,      /* wasm_runtime_lookup_function() */
    CMD_CREATE_EXEC_ENV,      /* wasm_runtime_create_exec_env() */
    CMD_CALL_WASM,            /* wasm_runtime_call_wasm */
    CMD_EXEC_APP_FUNC,        /* wasm_application_execute_func() */
    CMD_EXEC_APP_MAIN,        /* wasm_application_execute_main() */
    CMD_GET_EXCEPTION,        /* wasm_runtime_get_exception() */
    CMD_DEINSTANTIATE_MODULE, /* wasm_runtime_deinstantiate() */
    CMD_UNLOAD_MODULE,        /* wasm_runtime_unload() */
    CMD_DESTROY_RUNTIME,      /* wasm_runtime_destroy() */
    CMD_SET_WASI_ARGS,        /* wasm_runtime_set_wasi_args() */
    CMD_SET_LOG_LEVEL,        /* bh_log_set_verbose_level() */
};
```

Others
------

- Please add "-sgx" option when generating AoT file for SGX platform, e.g.:

  ```bash
  wamrc -sgx -o test.aot test.wasm
  ```

- The default max heap size of Enclave is 16 MB, it might be not enough when executing some workloads, please modify it in Enclave/Enclave.config.xml with a larger size when exception was thrown:

  ```bash
  Exception: fail to enlarge memory.
  or
  Exception: allocate memory failed.
  ```

  Enclave/Enclave.config.xml, default max heap size is 16 MB:

  ```xml
  <HeapMaxSize>0x1000000</HeapMaxSize>
  ```

