Implement extensible syscall interface for wasm

Author: Diggsey

src/etc/wasm32-shim.js

@@ -28,14 +28,76 @@ let m = new WebAssembly.Module(buffer);
 
 let memory = null;
 
+function viewstruct(data, fields) {
+  return new Uint32Array(memory.buffer).subarray(data/4, data/4 + fields);
+}
+
 function copystr(a, b) {
-  if (memory === null) {
-    return null
-  }
-  let view = new Uint8Array(memory.buffer).slice(a, a + b);
+  let view = new Uint8Array(memory.buffer).subarray(a, a + b);
   return String.fromCharCode.apply(null, view);
 }
 
+function syscall_write([fd, ptr, len]) {
+  let s = copystr(ptr, len);
+  switch (fd) {
+    case 1: process.stdout.write(s); break;
+    case 2: process.stderr.write(s); break;
+  }
+}
+
+function syscall_exit([code]) {
+  process.exit(code);
+}
+
+function syscall_args(params) {
+  let [ptr, len] = params;
+
+  // Calculate total required buffer size
+  let totalLen = -1;
+  for (let i = 2; i < process.argv.length; ++i) {
+    totalLen += Buffer.byteLength(process.argv[i]) + 1;
+  }
+  if (totalLen < 0) { totalLen = 0; }
+  params[2] = totalLen;
+
+  // If buffer is large enough, copy data
+  if (len >= totalLen) {
+    let view = new Uint8Array(memory.buffer);
+    for (let i = 2; i < process.argv.length; ++i) {
+      let value = process.argv[i];
+      Buffer.from(value).copy(view, ptr);
+      ptr += Buffer.byteLength(process.argv[i]) + 1;
+    }
+  }
+}
+
+function syscall_getenv(params) {
+  let [keyPtr, keyLen, valuePtr, valueLen] = params;
+
+  let key = copystr(keyPtr, keyLen);
+  let value = process.env[key];
+
+  if (value == null) {
+    params[4] = 0xFFFFFFFF;
+  } else {
+    let view = new Uint8Array(memory.buffer);
+    let totalLen = Buffer.byteLength(value);
+    params[4] = totalLen;
+    if (valueLen >= totalLen) {
+      Buffer.from(value).copy(view, valuePtr);
+    }
+  }
+}
+
+function syscall_time(params) {
+  let t = Date.now();
+  let secs = Math.floor(t / 1000);
+  let millis = t % 1000;
+  params[1] = Math.floor(secs / 0x100000000);
+  params[2] = secs % 0x100000000;
+  params[3] = Math.floor(millis * 1000000);
+}
+
 let imports = {};
 imports.env = {
   // These are generated by LLVM itself for various intrinsic calls. Hopefully
@@ -48,68 +110,25 @@ imports.env = {
   log10: Math.log10,
   log10f: Math.log10,
 
-  // These are called in src/libstd/sys/wasm/stdio.rs and are used when
-  // debugging is enabled.
-  rust_wasm_write_stdout: function(a, b) {
-    let s = copystr(a, b);
-    if (s !== null) {
-      process.stdout.write(s);
-    }
-  },
-  rust_wasm_write_stderr: function(a, b) {
-    let s = copystr(a, b);
-    if (s !== null) {
-      process.stderr.write(s);
-    }
-  },
-
-  // These are called in src/libstd/sys/wasm/args.rs and are used when
-  // debugging is enabled.
-  rust_wasm_args_count: function() {
-    if (memory === null)
-      return 0;
-    return process.argv.length - 2;
-  },
-  rust_wasm_args_arg_size: function(i) {
-    return Buffer.byteLength(process.argv[i + 2]);
-  },
-  rust_wasm_args_arg_fill: function(idx, ptr) {
-    let arg = process.argv[idx + 2];
-    let view = new Uint8Array(memory.buffer);
-    Buffer.from(arg).copy(view, ptr);
-  },
-
-  // These are called in src/libstd/sys/wasm/os.rs and are used when
-  // debugging is enabled.
-  rust_wasm_getenv_len: function(a, b) {
-    let key = copystr(a, b);
-    if (key === null) {
-      return -1;
+  rust_wasm_syscall: function(index, data) {
+    switch (index) {
+      case 1: syscall_write(viewstruct(data, 3)); return true;
+      case 2: syscall_exit(viewstruct(data, 1)); return true;
+      case 3: syscall_args(viewstruct(data, 3)); return true;
+      case 4: syscall_getenv(viewstruct(data, 5)); return true;
+      case 6: syscall_time(viewstruct(data, 4)); return true;
+      default:
+        console.log("Unsupported syscall: " + index);
+        return false;
     }
-    if (!(key in process.env)) {
-      return -1;
-    }
-    return Buffer.byteLength(process.env[key]);
-  },
-  rust_wasm_getenv_data: function(a, b, ptr) {
-    let key = copystr(a, b);
-    let value = process.env[key];
-    let view = new Uint8Array(memory.buffer);
-    Buffer.from(value).copy(view, ptr);
-  },
-};
-
-let module_imports = WebAssembly.Module.imports(m);
-
-for (var i = 0; i < module_imports.length; i++) {
-  let imp = module_imports[i];
-  if (imp.module != 'env') {
-    continue
   }
-  if (imp.name == 'memory' && imp.kind == 'memory') {
-    memory = new WebAssembly.Memory({initial: 20});
-    imports.env.memory = memory;
-  }
-}
+};
 
 let instance = new WebAssembly.Instance(m, imports);
+memory = instance.exports.memory;
+try {
+  instance.exports.main();
+} catch (e) {
+  console.error(e);
+  process.exit(101);
+}

src/librustc_trans/back/write.rs

@@ -824,9 +824,7 @@ fn binaryen_assemble(cgcx: &CodegenContext,
     if cgcx.debuginfo != config::NoDebugInfo {
         options.debuginfo(true);
     }
-    if cgcx.crate_types.contains(&config::CrateTypeExecutable) {
-        options.start("main");
-    }
+
     options.stack(1024 * 1024);
     options.import_memory(cgcx.wasm_import_memory);
     let assembled = input.and_then(|input| {
@@ -1452,7 +1450,7 @@ fn start_executing_work(tcx: TyCtxt,
         target_pointer_width: tcx.sess.target.target.target_pointer_width.clone(),
         binaryen_linker: tcx.sess.linker_flavor() == LinkerFlavor::Binaryen,
         debuginfo: tcx.sess.opts.debuginfo,
-        wasm_import_memory: wasm_import_memory,
+        wasm_import_memory,
         assembler_cmd,
     };
 

src/libstd/Cargo.toml

@@ -48,3 +48,4 @@ jemalloc = ["alloc_jemalloc"]
 force_alloc_system = []
 panic-unwind = ["panic_unwind"]
 profiler = ["profiler_builtins"]
+wasm_syscall = []

src/libstd/sys/wasm/args.rs

@@ -10,8 +10,8 @@
 
 use ffi::OsString;
 use marker::PhantomData;
-use mem;
 use vec;
+use sys::ArgsSysCall;
 
 pub unsafe fn init(_argc: isize, _argv: *const *const u8) {
     // On wasm these should always be null, so there's nothing for us to do here
@@ -21,38 +21,10 @@ pub unsafe fn cleanup() {
 }
 
 pub fn args() -> Args {
-    // When the runtime debugging is enabled we'll link to some extra runtime
-    // functions to actually implement this. These are for now just implemented
-    // in a node.js script but they're off by default as they're sort of weird
-    // in a web-wasm world.
-    if !super::DEBUG {
-        return Args {
-            iter: Vec::new().into_iter(),
-            _dont_send_or_sync_me: PhantomData,
-        }
-    }
-
-    // You'll find the definitions of these in `src/etc/wasm32-shim.js`. These
-    // are just meant for debugging and should not be relied on.
-    extern {
-        fn rust_wasm_args_count() -> usize;
-        fn rust_wasm_args_arg_size(a: usize) -> usize;
-        fn rust_wasm_args_arg_fill(a: usize, ptr: *mut u8);
-    }
-
-    unsafe {
-        let cnt = rust_wasm_args_count();
-        let mut v = Vec::with_capacity(cnt);
-        for i in 0..cnt {
-            let n = rust_wasm_args_arg_size(i);
-            let mut data = vec![0; n];
-            rust_wasm_args_arg_fill(i, data.as_mut_ptr());
-            v.push(mem::transmute::<Vec<u8>, OsString>(data));
-        }
-        Args {
-            iter: v.into_iter(),
-            _dont_send_or_sync_me: PhantomData,
-        }
+    let v = ArgsSysCall::perform();
+    Args {
+        iter: v.into_iter(),
+        _dont_send_or_sync_me: PhantomData,
     }
 }