(feat): add wasmtime sample

Author: dhruvinparikh

samples/wasmtime/README.md

@@ -0,0 +1,26 @@
+# Wasmtime sample
+
+This sample shows how to run WebAssembly inside EGo using [Wasmtime](https://pkg.go.dev/github.com/bytecodealliance/wasmtime-go).
+
+By default, *wasmtime-go* comes with a shared library. EGo only supports static linking. To this end, download the wasmtime static library and tell the Go compiler to use it:
+```sh
+mkdir wasmtime
+wget -O- https://github.com/bytecodealliance/wasmtime/releases/download/v15.0.0/wasmtime-v15.0.0-x86_64-linux-c-api.tar.xz | tar xvJf - -C ./wasmtime --strip-components=1
+CGO_CFLAGS="-I$PWD/wasmtime/include" CGO_LDFLAGS="$PWD/wasmtime/lib/libwasmtime.a -ldl -lm -static-libgcc" ego-go build
+```
+
+Then you can sign and run as usual:
+```sh
+ego sign wasmtime_sample
+ego run wasmtime_sample
+```
+
+You should see an output similar to:
+```
+[erthost] loading enclave ...
+[erthost] entering enclave ...
+[ego] starting application ...
+Results of `sum`: 3
+```
+
+Note that `executableHeap` is enabled in `enclave.json` so that Wasmtime can JIT-compile the WebAssembly.

samples/wasmtime/c.go

@@ -0,0 +1,9 @@
+package main
+
+/*
+#cgo LDFLAGS: -static-libgcc
+int gnu_get_libc_version() { return 0; }
+int __register_atfork() { return 0; }
+int __res_init() { return -1; }
+*/
+import "C"

samples/wasmtime/enclave.json

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+{
+ "exe": "wasmtime_sample",
+ "key": "private.pem",
+ "debug": true,
+ "heapSize": 512,
+ "executableHeap": false,
+ "productID": 1,
+ "securityVersion": 1,
+ "mounts": null,
+ "env": null,
+ "files": null
+}

samples/wasmtime/go.mod

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+module wasmtime_sample
+
+go 1.17
+
+require github.com/bytecodealliance/wasmtime-go/v15 v15.0.0

samples/wasmtime/go.sum

@@ -0,0 +1,10 @@
+github.com/bytecodealliance/wasmtime-go/v15 v15.0.0 h1:4R2MpSPPbtSxqdsOTvsMn1pnwdEhzbDGMao6LUUSLv4=
+github.com/bytecodealliance/wasmtime-go/v15 v15.0.0/go.mod h1:m6vB/SsM+pnJkVHmO1wzHYUeYtciltTKuxuvkR8pYcY=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/testify v1.8.0 h1:pSgiaMZlXftHpm5L7V1+rVB+AZJydKsMxsQBIJw4PKk=
+github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

samples/wasmtime/main.go

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+package main
+
+import (
+	"fmt"
+
+	"github.com/bytecodealliance/wasmtime-go/v15"
+)
+
+// https://pkg.go.dev/github.com/bytecodealliance/wasmtime-go#example-Config-Fuel
+func main() {
+	// Let's assume we don't have WebAssembly bytes at hand. We
+	// will write WebAssembly manually.
+	wasmBytes, err := wasmtime.Wat2Wasm(`
+	(module
+	  (type (func (param i32 i32) (result i32)))
+	  (func (type 0)
+	    local.get 0
+	    local.get 1
+	    i32.add)
+	  (export "sum" (func 0)))
+`)
+	if err != nil {
+		fmt.Println("Failed to parse WebAssembly code:", err)
+		return
+	}
+
+	engine := wasmtime.NewEngine()
+	
+	module, err := wasmtime.NewModule(engine, wasmBytes)
+	if err != nil {
+		fmt.Println("failed to compile module ",err)
+	}
+
+	linker := wasmtime.NewLinker(engine)
+	err = linker.DefineWasi()
+	if err != nil {
+		fmt.Println("failed to define wasi ",err)
+	}
+
+	wasiConfig := wasmtime.NewWasiConfig()
+
+	store := wasmtime.NewStore(engine)
+	store.SetWasi(wasiConfig)
+
+	instance,err := linker.Instantiate(store, module)
+	if err != nil {
+		fmt.Println("failed to instantiate ",err)
+	}
+
+	sumFunc := instance.GetFunc(store,"sum")
+	if sumFunc != nil {
+		result ,err := sumFunc.Call(store,1,2)
+		if err != nil {
+			fmt.Println("failed to call sum ",err)
+		}
+		fmt.Println("Results of `sum`:", result)
+	}
+}