Setup bazel to build a WASM version of the attestation library

Right now the rust code is wholly a placeholder, this CR just sets up all the bazel logic needed. Bug-Id: Change-Id: Id451b4163bfbf66f70f12b6c3b9cb0a4bfbb113c
project-oak · Jul 15, 2024 · 5811410 · 5811410
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diff --git a/oak_attestation_explain_wasm/BUILD b/oak_attestation_explain_wasm/BUILD
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+# Copyright 2020 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+load("@rules_rust//rust:defs.bzl", "rust_shared_library")
+
+package(
+    default_visibility = ["//visibility:public"],
+    licenses = ["notice"],
+)
+
+rust_shared_library(
+    name = "oak_attestation_explain_wasm",
+    srcs = glob(["src/*.rs"]),
+    platform = "//:wasm32-unknown-unknown",
+)
+
+exports_files(["index.html"])
diff --git a/oak_attestation_explain_wasm/README.MD b/oak_attestation_explain_wasm/README.MD
@@ -0,0 +1 @@
+Web version of the Oak attestation explaination tool, via WASM.
diff --git a/oak_attestation_explain_wasm/index.html b/oak_attestation_explain_wasm/index.html
@@ -0,0 +1,20 @@
+<!doctype html>
+<html>
+  <head>
+    <title>WASM Test</title>
+  </head>
+
+  <body>
+    <script>
+      const importObj = {};
+      (async () => {
+        const response = await fetch('./oak_attestation_explain_wasm.wasm');
+        const { instance } = await WebAssembly.instantiateStreaming(
+          response,
+          importObj,
+        );
+        console.log(instance.exports.nth_prime(10));
+      })();
+    </script>
+  </body>
+</html>
diff --git a/oak_attestation_explain_wasm/src/lib.rs b/oak_attestation_explain_wasm/src/lib.rs
@@ -0,0 +1,79 @@
+//
+// Copyright 2022 The Project Oak Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+// TODO: b/351012006 - Load the attestation library.
+// Right now this is just a placeholder for WASM logic without generated
+// bindings. From: https://surma.dev/things/rust-to-webassembly/
+
+#![no_std]
+extern crate alloc;
+use alloc::{alloc::Layout, vec::Vec};
+use core::{alloc::GlobalAlloc, cell::UnsafeCell};
+
+const ARENA_SIZE: usize = 128 * 1024;
+
+#[repr(C, align(32))]
+struct SimpleAllocator {
+    arena: UnsafeCell<[u8; ARENA_SIZE]>,
+    head: UnsafeCell<usize>,
+}
+
+impl SimpleAllocator {
+    const fn new() -> Self {
+        SimpleAllocator { arena: UnsafeCell::new([0; ARENA_SIZE]), head: UnsafeCell::new(0) }
+    }
+}
+
+unsafe impl Sync for SimpleAllocator {}
+
+#[global_allocator]
+static ALLOCATOR: SimpleAllocator = SimpleAllocator::new();
+
+unsafe impl GlobalAlloc for SimpleAllocator {
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        let size = layout.size();
+        let align = layout.align();
+        let idx = (*self.head.get()).next_multiple_of(align);
+        *self.head.get() = idx + size;
+        let arena: &mut [u8; ARENA_SIZE] = &mut (*self.arena.get());
+        match arena.get_mut(idx) {
+            Some(item) => item as *mut u8,
+            _ => core::ptr::null_mut(),
+        }
+    }
+
+    unsafe fn dealloc(&self, _ptr: *mut u8, _layout: Layout) {
+        /* lol */
+    }
+}
+
+#[panic_handler]
+fn panic(_panic: &core::panic::PanicInfo<'_>) -> ! {
+    core::arch::wasm32::unreachable()
+}
+
+#[no_mangle]
+pub extern "C" fn nth_prime(n: usize) -> usize {
+    let mut primes: Vec<usize> = Vec::new();
+    let mut current = 2;
+    while primes.len() < n {
+        if !primes.iter().any(|prime| current % prime == 0) {
+            primes.push(current);
+        }
+        current += 1;
+    }
+    primes.into_iter().last().unwrap_or(0)
+}
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		Web version of the Oak attestation explaination tool, via WASM.