Skip to content
master
Go to file
Code

Latest commit

 

Git stats

Files

Permalink
Failed to load latest commit information.
Type
Name
Latest commit message
Commit time
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
wa
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

README.md

wag is a WebAssembly compiler implemented as a Go package.

Features

  • The input is a wasm binary module.

  • The output is machine code.

  • It is only a compiler. A runtime environment for the compiled program, including all import functions, needs to be implemented separately. (But see wasys for an example runtime.)

  • Single-pass, fast ahead-of-time compilation. Early functions can be executed while the latter functions are still being compiled, even while the source is still being downloaded.

  • The generated code requires minimal runtime support; it's designed to be executed in an isolated environment. Calling standard library ABIs is not directly supported, but see wasys for an example which exposes syscalls as WebAssembly import functions.

  • Supports snapshot-and-restore across compiler versions and CPU architectures.

  • Supports breakpoint debugging via recompilation.

  • Cross-compilation is supported via Go build tags. If wagamd64 is specified, the x86-64 code generator is used regardless of host architecture, and CPU feature detection is disabled with pessimistic assumptions. Likewise for wagarm64 (but feature detection is not used for ARM64).

Status

  • Supports WebAssembly version 1 (wasm32). No wasm extensions are supported.

  • Supports x86-64 and ARM64 code generation.

  • Generated x86-64 code requires SSE4.1 ROUNDSS/ROUNDSD instructions.

Security

Spectre variant 1: Out-of-bounds linear memory access detection requires that addressable but unallocated memory is inaccessible. It naturally prevents conditional branch exploitation.

Spectre variant 2: On x86, Retpoline is used to protect the runtime environment (although user programs shouldn't be able to inject arbitrary addresses into the branch target buffer).

Testing

Requires Linux, Go, make, cmake, clang++ and libcapstone. About 75% of the WebAssembly spec testsuite is run, by first converting the tests to binary format:

  • git clone --recurse-submodules https://github.com/tsavola/wag.git
  • cd wag
  • make check

Screenshot #1

$ go get github.com/tsavola/wag/cmd/wasys
$ wasys -v $GOPATH/src/github.com/tsavola/wag/testdata/hello.wasm
import write(i32, i32, i32) i32
import openat(i32, i32, i32, i32) i32
import read(i32, i32, i32) i32
import close(i32) i32
import pipe2(i32, i32) i32
import _exit(i32)
hello, world

Screenshot #2

=== RUN   TestSnapshot
--- PASS: TestSnapshot (0.00s)
    snapshot_test.go:80: print output:
        10
        --- snapshotting ---
        current memory limit: 0x6a96051ca000
        current stack ptr:    0x6a960533ffc0
        globals+memory addr:  0x6a96051ba000
        stack addr:           0x6a960533f000
        globals+memory size:  65536
        memory size:          65536
        stack offset:         4032
        stacktrace:
        #1  func-3
        #2  func-2
        --- shot snapped ---
        20
    snapshot_test.go:88: resuming
    snapshot_test.go:100: print output:
        20
        30
        330
        40
        440
You can’t perform that action at this time.