wasmtime: first custom syscall demo

Cargo.toml

@@ -1,7 +1,9 @@
 [workspace]
 
 members = [
+    "common",
     "amd-sev",
     "wasmtime-basic",
     "wasmtime-native-embed",
+    "wasmtime-custom-syscall",
 ]

README.md

@@ -10,6 +10,9 @@ Compiling either a C or Rust program to WASM and running it natively using a Rus
 ## [Wasmtime - Rust native in WASM](wasmtime-native-embed)
 Running native Rust code in a WASM virtual machine without pre-compiling it.
 
+## [Wasmtime - Custom Syscalls](wasmtime-custom-syscall)
+Providing a custom syscall to a pre-compiled WASM binary written in Rust.
+
 ## Intel SGX
 A demonstration of remote attestation for an SGX enclave. The attesting enclave prepares a Report for the platform's
 Quoting Enclave, which verifies the Report and signs it with its Attestation Key, producing a Quote. The Quote is

common/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "common"
+version = "0.1.0"
+authors = ["Stefan Junker <[email protected]>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

common/src/lib.rs

@@ -0,0 +1 @@
+pub mod wasm;

common/src/wasm.rs

@@ -0,0 +1,86 @@
+pub mod enarx_syscalls {
+    use std::convert::TryInto;
+
+    #[link(wasm_import_module = "enarx_syscalls_stdio")]
+    extern "C" {
+        fn __print_str(ptr: *const u8, len: u64);
+    }
+
+    #[link(wasm_import_module = "enarx_syscalls_net")]
+    extern "C" {
+        fn __socket_udp_bind(ptr: *const u8, len: u64);
+
+        fn __socket_udp_receive(
+            data_ptr: *mut u8,
+            data_len: u64,
+            src_ptr: *mut u8,
+            src_len: u64,
+        ) -> u64;
+
+        fn __socket_udp_send_to(
+            data_ptr: *const u8,
+            data_len: u64,
+            dst_ptr: *const u8,
+            dst_len: u64,
+        ) -> u64;
+    }
+
+    fn _print_str(s: &str) {
+        unsafe { __print_str(s.as_ptr(), s.len().try_into().unwrap()) }
+    }
+
+    pub fn print(s: &str) {
+        _print_str(s)
+    }
+
+    pub fn println(s: &str) {
+        _print_str(&format!("{}\n", s));
+    }
+
+    pub fn socket_udp_bind(addr: &str) {
+        unsafe { __socket_udp_bind(addr.as_ptr(), addr.len().try_into().unwrap()) }
+    }
+
+    pub fn socket_udp_receive(content_buf: &mut [u8], source_buf: &mut [u8]) -> u64 {
+        unsafe {
+            __socket_udp_receive(
+                content_buf.as_mut_ptr(),
+                content_buf.len().try_into().unwrap(),
+                source_buf.as_mut_ptr(),
+                source_buf.len().try_into().unwrap(),
+            )
+        }
+    }
+
+    pub fn socket_udp_send_to(data: &[u8], dst: &[u8]) -> u64 {
+        unsafe {
+            __socket_udp_send_to(
+                data.as_ptr(),
+                data.len().try_into().unwrap(),
+                dst.as_ptr(),
+                dst.len().try_into().unwrap(),
+            )
+        }
+    }
+}
+
+pub mod wasmstr {
+    use std::convert::TryInto;
+
+    pub struct WasmStr(pub *const u8, pub u64);
+
+    impl WasmStr {
+        pub fn to_str(&self) -> &str {
+            self.into()
+        }
+    }
+
+    impl std::convert::From<&WasmStr> for &str {
+        fn from(wasm_string: &WasmStr) -> Self {
+            std::str::from_utf8(unsafe {
+                std::slice::from_raw_parts(wasm_string.0, wasm_string.1.try_into().unwrap())
+            })
+            .unwrap()
+        }
+    }
+}