fix wasmtime sample

samples/wasmtime/README.md

@@ -2,20 +2,33 @@
 
 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:
+By default, *wasmtime-go* comes with a library that makes direct syscalls.
+EGo only supports syscall via libc.
+To this end, build the wasmtime library with libc backend:
+
 ```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
+git clone -bv15.0.1 --depth=1 https://github.com/bytecodealliance/wasmtime
+cd wasmtime
+git submodule update --init --depth=1
+RUSTFLAGS=--cfg=rustix_use_libc cargo build --release -p wasmtime-c-api
+cd ..
+```
+
+Tell the Go compiler to use it:
+
+```sh
+CGO_LDFLAGS=wasmtime/target/release/libwasmtime.a 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 ...

samples/wasmtime/c.go

@@ -1,9 +1,19 @@
 package main
 
+// The wasmtime library links a few symbols that are not available in EGo, but it's sufficient to provide stub implementations of them.
+
 /*
 #cgo LDFLAGS: -static-libgcc
 int gnu_get_libc_version() { return 0; }
 int __register_atfork() { return 0; }
 int __res_init() { return -1; }
+
+// TODO remove with next EGo release that supports this syscall
+#include <time.h>
+int clock_getres(int clockid, struct timespec* res) {
+	res->tv_sec = 0;
+	res->tv_nsec = 4000000;
+	return 0;
+}
 */
 import "C"

samples/wasmtime/enclave.json

@@ -1,12 +1,9 @@
 {
- "exe": "wasmtime_sample",
- "key": "private.pem",
- "debug": true,
- "heapSize": 512,
- "executableHeap": false,
- "productID": 1,
- "securityVersion": 1,
- "mounts": null,
- "env": null,
- "files": null
-}
+    "exe": "wasmtime_sample",
+    "key": "private.pem",
+    "debug": true,
+    "heapSize": 512,
+    "executableHeap": true,
+    "productID": 1,
+    "securityVersion": 1
+}

samples/wasmtime/go.mod

@@ -1,5 +1,5 @@
 module wasmtime_sample
 
-go 1.17
+go 1.18
 
 require github.com/bytecodealliance/wasmtime-go/v15 v15.0.0

samples/wasmtime/go.sum

@@ -1,10 +1,6 @@
 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=