wasi: Implement random_get function

.editorconfig

@@ -0,0 +1,7 @@
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true

CONTRIBUTING.md

@@ -0,0 +1,70 @@
+# Contributing
+
+We welcome contributions from the community. Please read the following guidelines carefully to maximize the chances of your PR being merged.
+
+## Coding Style
+
+- To ensure your change passes format checks, use run `make check`. To format your files, you can run `make format`.
+- We follow standard Go table-driven tests and use the [`testify/require`](https://github.com/stretchr/testify#require-package) library to assert correctness. To verify all tests pass, you can run `make test`.
+
+## DCO
+
+We require DCO signoff line in every commit to this repo.
+
+The sign-off is a simple line at the end of the explanation for the
+patch, which certifies that you wrote it or otherwise have the right to
+pass it on as an open-source patch. The rules are pretty simple: if you
+can certify the below (from
+[developercertificate.org](https://developercertificate.org/)):
+
+```
+Developer Certificate of Origin
+Version 1.1
+Copyright (C) 2004, 2006 The Linux Foundation and its contributors.
+660 York Street, Suite 102,
+San Francisco, CA 94110 USA
+Everyone is permitted to copy and distribute verbatim copies of this
+license document, but changing it is not allowed.
+Developer's Certificate of Origin 1.1
+By making a contribution to this project, I certify that:
+(a) The contribution was created in whole or in part by me and I
+    have the right to submit it under the open source license
+    indicated in the file; or
+(b) The contribution is based upon previous work that, to the best
+    of my knowledge, is covered under an appropriate open source
+    license and I have the right under that license to submit that
+    work with modifications, whether created in whole or in part
+    by me, under the same open source license (unless I am
+    permitted to submit under a different license), as indicated
+    in the file; or
+(c) The contribution was provided directly to me by some other
+    person who certified (a), (b) or (c) and I have not modified
+    it.
+(d) I understand and agree that this project and the contribution
+    are public and that a record of the contribution (including all
+    personal information I submit with it, including my sign-off) is
+    maintained indefinitely and may be redistributed consistent with
+    this project or the open source license(s) involved.
+```
+
+then you just add a line to every git commit message:
+
+    Signed-off-by: Joe Smith <joe@gmail.com>
+
+using your real name (sorry, no pseudonyms or anonymous contributions.)
+
+You can add the sign off when creating the git commit via `git commit -s`.
+
+## Code Reviews
+
+* Indicate the priority of each comment, following this
+[feedback ladder](https://www.netlify.com/blog/2020/03/05/feedback-ladders-how-we-encode-code-reviews-at-netlify/).
+If none was indicated it will be treated as `[dust]`.
+* A single approval is sufficient to merge, except when the change cuts
+across several components; then it should be approved by at least one owner
+of each component. If a reviewer asks for changes in a PR they should be
+addressed before the PR is merged, even if another reviewer has already
+approved the PR.
+* During the review, address the comments and commit the changes _without_ squashing the commits.
+This facilitates incremental reviews since the reviewer does not go through all the code again to
+find out what has changed since the last review.

README.md

@@ -5,23 +5,40 @@ portability features like cross compilation. Import wazero and extend your Go ap
 language!
 
 ## Example
+
 Here's an example of using wazero to invoke a Fibonacci function included in a Wasm binary.
 
-While our [source for this](examples/testdata/fibonacci.go) is [TinyGo](https://tinygo.org/), it could have been written in
-another language that targets Wasm, such as Rust.
+While our [source for this](examples/testdata/fibonacci.go) is [TinyGo](https://tinygo.org/), it could have been written in another language that targets Wasm, such as AssemblyScript/C/C++/Rust/Zig.
 
 ```golang
+package main
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	"github.com/tetratelabs/wazero/wasi"
+	"github.com/tetratelabs/wazero/wasm"
+	"github.com/tetratelabs/wazero/wasm/binary"
+	"github.com/tetratelabs/wazero/wasm/interpreter"
+)
+
 func main() {
+	// Default context impl. by Go
+	ctx := context.Background()
 	// Read WebAssembly binary.
-	source, _ := os.ReadFile("fibonacci.wasm")
+	source, _ := os.ReadFile("examples/testdata/fibonacci.wasm")
 	// Decode the binary as WebAssembly module.
 	mod, _ := binary.DecodeModule(source)
 	// Initialize the execution environment called "store" with Interpreter-based engine.
 	store := wasm.NewStore(interpreter.NewEngine())
+	// To resolve WASI specific methods, such as `fd_write`
+	wasi.RegisterAPI(store)
 	// Instantiate the decoded module.
 	store.Instantiate(mod, "test")
 	// Execute the exported "fibonacci" function from the instantiated module.
-	ret, _, err := store.CallFunction("test", "fibonacci", 20)
+	ret, _, _ := store.CallFunction(ctx, "test", "fibonacci", 20)
 	// Give us the fibonacci number for 20, namely 6765!
 	fmt.Println(ret[0])
 }
@@ -58,4 +75,4 @@ Currently any performance optimization hasn't been done to this runtime yet, and
 
 However _theoretically speaking_, this project have the potential to compete with these state-of-the-art JIT-style runtimes. The rationale for that is it is well-know that [CGO is slow](https://github.com/golang/go/issues/19574). More specifically, if you make large amount of CGO calls which cross the boundary between Go and C (stack) space, then the usage of CGO could be a bottleneck.
 
-Since we can do JIT compilation purely in Go, this runtime could be the fastest one for some use cases where we have to make large amount of CGO calls (e.g. Proxy-Wasm host environment, or request-based plugin systems).
+Since we can do JIT compilation purely in Go, this runtime could be the fastest one for some use cases where we have to make large amount of CGO calls (e.g. Proxy-Wasm host environment, or request-based plugin systems).

tests/README.md

@@ -1,6 +1,9 @@
 This directory contains tests which use multiple packages. For example:
 
-- `bench` contains benchmark tests.
-- `codec` contains a test and benchmark on text and binary decoders.
-- `engine` contains variety of e2e tests, mainly to ensure the consistency in the behavior between engines.
-- `spectest` contains end-to-end tests with the [WebAssembly specification tests](https://github.com/WebAssembly/spec/tree/wg-1.0/test/core).
+* `bench` contains benchmark tests.
+* `codec` contains a test and benchmark on text and binary decoders.
+* `engine` contains variety of e2e tests, mainly to ensure the consistency in the behavior between engines.
+* `spectest` contains end-to-end tests with the [WebAssembly specification tests](https://github.com/WebAssembly/spec/tree/wg-1.0/test/core).
+
+*Note*: this doesn't contain WASI tests, as there's not yet an [official testsuite](https://github.com/WebAssembly/WASI/issues/9).
+Meanwhile, WASI functions are unit tested including via Text Format imports [here](../wasi/wasi_test.go)

wasi/testdata/random.wat

@@ -0,0 +1,24 @@
+;; This is a wat file to just export clock WASI API to the host environment for testing the APIs.
+;; This is currently separated as a wat file and pre-compiled because our text parser doesn't
+;; implement 'memory' yet. After it supports 'memory', we can remove this file and embed this
+;; wat file in the Go test code.
+;;
+;; Note: Although this is a raw wat file which should be moved under /tests/wasi in principle,
+;; this file is put here for now, because this is a temporary file until the parser supports
+;; the enough syntax, and this file will be embedded in unit test codes after that.
+(module
+  (import "wasi_snapshot_preview1" "random_get"
+    (func $wasi.random_get  (param $buf i32) (param $buf_len i32) (result (;errno;) i32)))
+  (memory 1)  ;; just an arbitrary size big enough for tests
+  (export "memory" (memory 0))
+  ;; Define wrapper functions instead of just exporting the imported WASI APIS for now
+  ;; because wazero's interpreter has a bug that it crashes when an imported-and-exported host function
+  ;; is called from the host environment, which will be fixed soon.
+  ;; After it's fixed, these wrapper functions are no longer necessary.
+  (func $random_get (param i32 i32) (result i32)
+        local.get 0
+        local.get 1
+        call $wasi.random_get
+        )
+  (export "random_get" (func $random_get))
+  )

wasi/wasi.go

@@ -1,12 +1,12 @@
 package wasi
 
 import (
+	crand "crypto/rand"
 	"encoding/binary"
 	"errors"
 	"io"
 	"io/fs"
 	"math"
-	"math/rand"
 	"os"
 	"reflect"
 	"time"
@@ -143,7 +143,24 @@ type API interface {
 	// TODO: ProcExit
 	// TODO: ProcRaise
 	// TODO: SchedYield
-	// TODO: RandomGet
+
+	// RandomGet is a WASI function that write random data in buffer (rand.Read()).
+	//
+	// * buf - is a offset to write random values
+	// * bufLen - size of random data in bytes
+	//
+	// For example, if `HostFunctionCallContext.Randomizer` initialized
+	// with random seed `rand.NewSource(42)`, we expect `ctx.Memory.Buffer` to contain:
+	//
+	//                             bufLen (5)
+	//                    +--------------------------+
+	//                    |                        	 |
+	//          []byte{?, 0x53, 0x8c, 0x7f, 0x96, 0xb1, ?}
+	//              buf --^
+	//
+	// See https://github.com/WebAssembly/WASI/blob/snapshot-01/phases/snapshot/docs.md#-random_getbuf-pointeru8-bufLen-size---errno
+	RandomGet(ctx *wasm.HostFunctionCallContext, buf, bufLen uint32) Errno
+
 	// TODO: SockRecv
 	// TODO: SockSend
 	// TODO: SockShutdown
@@ -154,6 +171,24 @@ const (
 	wasiSnapshotPreview1Name = "wasi_snapshot_preview1"
 )
 
+type RandomSource interface {
+	Read([]byte) (int, error)
+	Int31() (int32, error)
+}
+
+// Non-deterministic random source using crypto/rand
+type CryptoRandomSource struct{}
+
+func (c *CryptoRandomSource) Read(p []byte) (n int, err error) {
+	return crand.Read(p)
+}
+
+func (c *CryptoRandomSource) Int31() (v int32, err error) {
+	err = binary.Read(crand.Reader, binary.BigEndian, &v)
+
+	return v, err
+}
+
 type api struct {
 	args  *nullTerminatedStrings
 	stdin io.Reader
@@ -162,6 +197,7 @@ type api struct {
 	opened map[uint32]fileEntry
 	// timeNowUnixNano is mutable for testing
 	timeNowUnixNano func() uint64
+	randSource      RandomSource
 }
 
 func (a *api) register(store *wasm.Store) (err error) {
@@ -212,7 +248,7 @@ func (a *api) register(store *wasm.Store) (err error) {
 		{FunctionProcExit, proc_exit},
 		// TODO: FunctionProcRaise
 		// TODO: FunctionSchedYield
-		// TODO: FunctionRandomGet
+		{FunctionRandomGet, a.RandomGet},
 		// TODO: FunctionSockRecv
 		// TODO: FunctionSockSend
 		// TODO: FunctionSockShutdown
@@ -345,6 +381,7 @@ func newAPI(opts ...Option) *api {
 		timeNowUnixNano: func() uint64 {
 			return uint64(time.Now().UnixNano())
 		},
+		randSource: &CryptoRandomSource{},
 	}
 
 	// apply functional options
@@ -354,11 +391,16 @@ func newAPI(opts ...Option) *api {
 	return ret
 }
 
-func (a *api) randUnusedFD() uint32 {
-	fd := uint32(rand.Int31())
+func (a *api) randUnusedFD() (uint32, error) {
+	v, err := a.randSource.Int31()
+	if err != nil {
+		return 0, err
+	}
+
+	fd := uint32(v)
 	for {
 		if _, ok := a.opened[fd]; !ok {
-			return fd
+			return fd, nil
 		}
 		fd = (fd + 1) % (1 << 31)
 	}
@@ -412,7 +454,10 @@ func (a *api) path_open(ctx *wasm.HostFunctionCallContext, fd, dirFlags, pathPtr
 		}
 	}
 
-	newFD := a.randUnusedFD()
+	newFD, err := a.randUnusedFD()
+	if err != nil {
+		return ErrnoInval
+	}
 
 	a.opened[newFD] = fileEntry{
 		file: f,
@@ -503,6 +548,23 @@ func (a *api) fd_close(ctx *wasm.HostFunctionCallContext, fd uint32) (err Errno)
 	return ErrnoSuccess
 }
 
+// RandomGet implements API.RandomGet
+func (a *api) RandomGet(ctx *wasm.HostFunctionCallContext, buf uint32, bufLen uint32) (errno Errno) {
+	if !ctx.Memory.ValidateAddrRange(buf, uint64(bufLen)) {
+		return ErrnoInval
+	}
+
+	random_bytes := make([]byte, bufLen)
+	_, err := a.randSource.Read(random_bytes)
+	if err != nil {
+		return ErrnoInval
+	}
+
+	copy(ctx.Memory.Buffer[buf:buf+bufLen], random_bytes)
+
+	return ErrnoSuccess
+}
+
 func proc_exit(*wasm.HostFunctionCallContext, uint32) {
 	// TODO: implement
 }