fix no_std building

* Avoid temporary allocation when push locals during function invocation.

* Extend value stack for all locals at once.

.gitignore

@@ -3,3 +3,4 @@
 **/*.rs.bk
 Cargo.lock
 spec/target
+.idea

.travis.yml

@@ -26,6 +26,8 @@ script:
 - if [ "$TRAVIS_RUST_VERSION" == "nightly" ]; then cargo check --benches --manifest-path=benches/Cargo.toml; fi
 # Make sure `no_std` version checks.
 - if [ "$TRAVIS_RUST_VERSION" == "nightly" ]; then cargo +nightly check --no-default-features --features core; fi
+# Check that `vec_memory` feature works.
+- cargo check --features vec_memory
 - travis_wait 60 ./test.sh
 - ./doc.sh
 
@@ -38,7 +40,17 @@ after_success: |
   ghp-import -n target/doc &&
   git push -fq https://${GH_TOKEN}@github.com/${TRAVIS_REPO_SLUG}.git gh-pages
 
-cache: cargo
+cache:
+  # Don't use `cache: cargo` since it adds the `target` directory and that can be huge.
+  # Saving and loading this directory dwarfes actual compilation and test times. But what is more
+  # important, is that travis timeouts the build since the job doesn't produce any output for more
+  # than 10 minutes.
+  #
+  # So we just cache ~/.cargo directory
+  directories:
+    - /home/travis/.cargo
 before_cache:
   # Travis can't cache files that are not readable by "others"
   - chmod -R a+r $HOME/.cargo
+  # According to the Travis CI docs for building Rust project this is done by,
+  - rm -rf /home/travis/.cargo/registry

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "wasmi"
-version = "0.4.5"
+version = "0.5.1"
 authors = ["Nikolay Volf <nikvolf@gmail.com>", "Svyatoslav Nikolsky <svyatonik@yandex.ru>", "Sergey Pepyakin <s.pepyakin@gmail.com>"]
 license = "MIT/Apache-2.0"
 readme = "README.md"
@@ -11,17 +11,17 @@ keywords = ["wasm", "webassembly", "bytecode", "interpreter"]
 exclude = [ "/res/*", "/tests/*", "/fuzz/*", "/benches/*" ]
 
 [dependencies]
-wasmi-validation = { version = "0.1", path = "validation", default-features = false }
-parity-wasm = { version = "0.31", default-features = false }
+wasmi-validation = { version = "0.2", path = "validation", default-features = false }
+parity-wasm = { version = "0.40.1", default-features = false }
 memory_units = "0.3.0"
 libm = { version = "0.1.2", optional = true }
-num-rational = "0.2.2"
-num-traits = "0.2.8"
+num-rational = { version = "0.2.2", default-features = false }
+num-traits = { version = "0.2.8", default-features = false }
 
 [dev-dependencies]
 assert_matches = "1.1"
 rand = "0.4.2"
-wabt = "0.6"
+wabt = "0.9"
 
 [features]
 default = ["std"]
@@ -30,13 +30,22 @@ std = [
     "parity-wasm/std",
     "wasmi-validation/std",
     "num-rational/std",
+    "num-rational/bigint-std",
     "num-traits/std"
 ]
 # Enable for no_std support
 core = [
+    # `core` doesn't support vec_memory
+    "vec_memory",
     "wasmi-validation/core",
     "libm"
 ]
+# Enforce using the linear memory implementation based on `Vec` instead of
+# mmap on unix systems.
+#
+# Useful for tests and if you need to minimize unsafe usage at the cost of performance on some
+# workloads.
+vec_memory = []
 
 [workspace]
 members = ["validation"]

README.md

@@ -26,8 +26,8 @@ This crate supports `no_std` environments.
 Enable the `core` feature and disable default features:
 ```toml
 [dependencies]
-parity-wasm = {
-	version = "0.31",
+wasmi = {
+	version = "*",
 	default-features = false,
 	features = "core"
 }

benches/Cargo.toml

@@ -6,7 +6,7 @@ authors = ["Sergey Pepyakin <s.pepyakin@gmail.com>"]
 [dependencies]
 wasmi = { path = ".." }
 assert_matches = "1.2"
-wabt = "0.6"
+wabt = "0.9"
 
 [profile.bench]
 debug = true

benches/src/lib.rs

@@ -13,7 +13,7 @@ use wasmi::{ImportsBuilder, Module, ModuleInstance, NopExternals, RuntimeValue};
 use test::Bencher;
 
 // Load a module from a file.
-fn load_from_file(filename: &str) -> Result<Module, Box<error::Error>> {
+fn load_from_file(filename: &str) -> Result<Module, Box<dyn error::Error>> {
 	use std::io::prelude::*;
 	let mut file = File::open(filename)?;
 	let mut buf = Vec::new();

benches/wasm-kernel/src/lib.rs

@@ -33,7 +33,7 @@ pub extern "C" fn prepare_tiny_keccak() -> *const TinyKeccakTestData {
 }
 
 #[no_mangle]
-pub extern "C" fn bench_tiny_keccak(test_data: *const TinyKeccakTestData) {
+pub extern "C" fn bench_tiny_keccak(test_data: *mut TinyKeccakTestData) {
 	unsafe {
 		let mut keccak = Keccak::new_keccak256();
 		keccak.update((*test_data).data);

fuzz/Cargo.toml

@@ -10,7 +10,7 @@ cargo-fuzz = true
 
 [dependencies]
 wasmi = { path = ".." }
-wabt = "0.6.0"
+wabt = "0.9"
 wasmparser = "0.14.1"
 tempdir = "0.3.6"
 

hfuzz/Cargo.toml

@@ -7,4 +7,4 @@ authors = ["Sergey Pepyakin <s.pepyakin@gmail.com>"]
 honggfuzz = "=0.5.9" # Strict equal since hfuzz requires dep and cmd versions to match.
 wasmi = { path = ".." }
 tempdir = "0.3.6"
-wabt = "0.6.0"
+wabt = "0.9"

src/func.rs

@@ -1,6 +1,8 @@
-#[allow(unused_imports)]
-use alloc::prelude::v1::*;
-use alloc::rc::{Rc, Weak};
+use alloc::{
+    borrow::Cow,
+    rc::{Rc, Weak},
+    vec::Vec,
+};
 use core::fmt;
 use host::Externals;
 use isa;
@@ -194,12 +196,13 @@ impl FuncInstance {
     /// [`resume_execution`]: struct.FuncInvocation.html#method.resume_execution
     pub fn invoke_resumable<'args>(
         func: &FuncRef,
-        args: &'args [RuntimeValue],
+        args: impl Into<Cow<'args, [RuntimeValue]>>,
     ) -> Result<FuncInvocation<'args>, Trap> {
+        let args = args.into();
         check_function_args(func.signature(), &args)?;
         match *func.as_internal() {
             FuncInstanceInternal::Internal { .. } => {
-                let interpreter = Interpreter::new(func, args, None)?;
+                let interpreter = Interpreter::new(func, &*args, None)?;
                 Ok(FuncInvocation {
                     kind: FuncInvocationKind::Internal(interpreter),
                 })
@@ -256,7 +259,7 @@ pub struct FuncInvocation<'args> {
 enum FuncInvocationKind<'args> {
     Internal(Interpreter),
     Host {
-        args: &'args [RuntimeValue],
+        args: Cow<'args, [RuntimeValue]>,
         host_func_index: usize,
         finished: bool,
     },
@@ -303,7 +306,7 @@ impl<'args> FuncInvocation<'args> {
                     return Err(ResumableError::AlreadyStarted);
                 }
                 *finished = true;
-                Ok(externals.invoke_index(*host_func_index, args.clone().into())?)
+                Ok(externals.invoke_index(*host_func_index, args.as_ref().into())?)
             }
         }
     }

src/host.rs

@@ -114,11 +114,11 @@ pub trait HostError: 'static + ::core::fmt::Display + ::core::fmt::Debug + Send
     }
 }
 
-impl HostError {
+impl dyn HostError {
     /// Attempt to downcast this `HostError` to a concrete type by reference.
     pub fn downcast_ref<T: HostError>(&self) -> Option<&T> {
         if self.__private_get_type_id__() == TypeId::of::<T>() {
-            unsafe { Some(&*(self as *const HostError as *const T)) }
+            unsafe { Some(&*(self as *const dyn HostError as *const T)) }
         } else {
             None
         }
@@ -128,7 +128,7 @@ impl HostError {
     /// reference.
     pub fn downcast_mut<T: HostError>(&mut self) -> Option<&mut T> {
         if self.__private_get_type_id__() == TypeId::of::<T>() {
-            unsafe { Some(&mut *(self as *mut HostError as *mut T)) }
+            unsafe { Some(&mut *(self as *mut dyn HostError as *mut T)) }
         } else {
             None
         }
@@ -257,5 +257,5 @@ mod tests {
     }
 
     // Tests that `HostError` trait is object safe.
-    fn _host_error_is_object_safe(_: &HostError) {}
+    fn _host_error_is_object_safe(_: &dyn HostError) {}
 }

src/imports.rs

@@ -1,7 +1,4 @@
-#[allow(unused_imports)]
-use alloc::prelude::v1::*;
-
-use alloc::collections::BTreeMap;
+use alloc::{collections::BTreeMap, string::String};
 
 use func::FuncRef;
 use global::GlobalRef;
@@ -103,7 +100,7 @@ pub trait ImportResolver {
 /// [`ImportResolver`]: trait.ImportResolver.html
 /// [`ModuleImportResolver`]: trait.ModuleImportResolver.html
 pub struct ImportsBuilder<'a> {
-    modules: BTreeMap<String, &'a ModuleImportResolver>,
+    modules: BTreeMap<String, &'a dyn ModuleImportResolver>,
 }
 
 impl<'a> Default for ImportsBuilder<'a> {
@@ -124,7 +121,7 @@ impl<'a> ImportsBuilder<'a> {
     pub fn with_resolver<N: Into<String>>(
         mut self,
         name: N,
-        resolver: &'a ModuleImportResolver,
+        resolver: &'a dyn ModuleImportResolver,
     ) -> Self {
         self.modules.insert(name.into(), resolver);
         self
@@ -133,11 +130,15 @@ impl<'a> ImportsBuilder<'a> {
     /// Register an resolver by a name.
     ///
     /// Mutable borrowed version.
-    pub fn push_resolver<N: Into<String>>(&mut self, name: N, resolver: &'a ModuleImportResolver) {
+    pub fn push_resolver<N: Into<String>>(
+        &mut self,
+        name: N,
+        resolver: &'a dyn ModuleImportResolver,
+    ) {
         self.modules.insert(name.into(), resolver);
     }
 
-    fn resolver(&self, name: &str) -> Option<&ModuleImportResolver> {
+    fn resolver(&self, name: &str) -> Option<&dyn ModuleImportResolver> {
         self.modules.get(name).cloned()
     }
 }

src/isa.rs

@@ -67,8 +67,7 @@
 //! - Reserved immediates are ignored for `call_indirect`, `current_memory`, `grow_memory`.
 //!
 
-#[allow(unused_imports)]
-use alloc::prelude::v1::*;
+use alloc::vec::Vec;
 
 /// Should we keep a value before "discarding" a stack frame?
 ///

src/lib.rs

@@ -96,8 +96,6 @@
 
 #![warn(missing_docs)]
 #![cfg_attr(not(feature = "std"), no_std)]
-//// alloc is required in no_std
-#![cfg_attr(not(feature = "std"), feature(alloc, alloc_prelude))]
 
 #[cfg(not(feature = "std"))]
 #[macro_use]
@@ -119,8 +117,11 @@ extern crate parity_wasm;
 
 extern crate wasmi_validation as validation;
 
-#[allow(unused_imports)]
-use alloc::prelude::v1::*;
+use alloc::{
+    boxed::Box,
+    string::{String, ToString},
+    vec::Vec,
+};
 use core::fmt;
 #[cfg(feature = "std")]
 use std::error;
@@ -239,7 +240,7 @@ pub enum TrapKind {
     /// Typically returned from an implementation of [`Externals`].
     ///
     /// [`Externals`]: trait.Externals.html
-    Host(Box<host::HostError>),
+    Host(Box<dyn host::HostError>),
 }
 
 impl TrapKind {
@@ -273,7 +274,7 @@ pub enum Error {
     /// Trap.
     Trap(Trap),
     /// Custom embedder error.
-    Host(Box<host::HostError>),
+    Host(Box<dyn host::HostError>),
 }
 
 impl Error {
@@ -285,7 +286,7 @@ impl Error {
     /// [`Host`]: enum.Error.html#variant.Host
     /// [`Trap`]: enum.Error.html#variant.Trap
     /// [`TrapKind::Host`]: enum.TrapKind.html#variant.Host
-    pub fn as_host_error(&self) -> Option<&host::HostError> {
+    pub fn as_host_error(&self) -> Option<&dyn host::HostError> {
         match *self {
             Error::Host(ref host_err) => Some(&**host_err),
             Error::Trap(ref trap) => match *trap.kind() {

src/memory/mmap_bytebuf.rs

@@ -0,0 +1,189 @@
+//! An implementation of a `ByteBuf` based on virtual memory.
+//!
+//! This implementation uses `mmap` on POSIX systems (and should use `VirtualAlloc` on windows).
+//! There are possibilities to improve the performance for the reallocating case by reserving
+//! memory up to maximum. This might be a problem for systems that don't have a lot of virtual
+//! memory (i.e. 32-bit platforms).
+
+use std::ptr::{self, NonNull};
+use std::slice;
+
+struct Mmap {
+    /// The pointer that points to the start of the mapping.
+    ///
+    /// This value doesn't change after creation.
+    ptr: NonNull<u8>,
+    /// The length of this mapping.
+    ///
+    /// Cannot be more than `isize::max_value()`. This value doesn't change after creation.
+    len: usize,
+}
+
+impl Mmap {
+    /// Create a new mmap mapping
+    ///
+    /// Returns `Err` if:
+    /// - `len` should not exceed `isize::max_value()`
+    /// - `len` should be greater than 0.
+    /// - `mmap` returns an error (almost certainly means out of memory).
+    fn new(len: usize) -> Result<Self, &'static str> {
+        if len > isize::max_value() as usize {
+            return Err("`len` should not exceed `isize::max_value()`");
+        }
+        if len == 0 {
+            return Err("`len` should be greater than 0");
+        }
+
+        let ptr_or_err = unsafe {
+            // Safety Proof:
+            // There are not specific safety proofs are required for this call, since the call
+            // by itself can't invoke any safety problems (however, misusing its result can).
+            libc::mmap(
+                // `addr` - let the system to choose the address at which to create the mapping.
+                ptr::null_mut(),
+                // the length of the mapping in bytes.
+                len,
+                // `prot` - protection flags: READ WRITE !EXECUTE
+                libc::PROT_READ | libc::PROT_WRITE,
+                // `flags`
+                // `MAP_ANON` - mapping is not backed by any file and initial contents are
+                // initialized to zero.
+                // `MAP_PRIVATE` - the mapping is private to this process.
+                libc::MAP_ANON | libc::MAP_PRIVATE,
+                // `fildes` - a file descriptor. Pass -1 as this is required for some platforms
+                // when the `MAP_ANON` is passed.
+                -1,
+                // `offset` - offset from the file.
+                0,
+            )
+        };
+
+        match ptr_or_err {
+            // With the current parameters, the error can only be returned in case of insufficient
+            // memory.
+            libc::MAP_FAILED => Err("mmap returned an error"),
+            _ => {
+                let ptr = NonNull::new(ptr_or_err as *mut u8).ok_or("mmap returned 0")?;
+                Ok(Self { ptr, len })
+            }
+        }
+    }
+
+    fn as_slice(&self) -> &[u8] {
+        unsafe {
+            // Safety Proof:
+            // - Aliasing guarantees of `self.ptr` are not violated since `self` is the only owner.
+            // - This pointer was allocated for `self.len` bytes and thus is a valid slice.
+            // - `self.len` doesn't change throughout the lifetime of `self`.
+            // - The value is returned valid for the duration of lifetime of `self`.
+            //   `self` cannot be destroyed while the returned slice is alive.
+            // - `self.ptr` is of `NonNull` type and thus `.as_ptr()` can never return NULL.
+            // - `self.len` cannot be larger than `isize::max_value()`.
+            slice::from_raw_parts(self.ptr.as_ptr(), self.len)
+        }
+    }
+
+    fn as_slice_mut(&mut self) -> &mut [u8] {
+        unsafe {
+            // Safety Proof:
+            // - See the proof for `Self::as_slice`
+            // - Additionally, it is not possible to obtain two mutable references for `self.ptr`
+            slice::from_raw_parts_mut(self.ptr.as_ptr(), self.len)
+        }
+    }
+}
+
+impl Drop for Mmap {
+    fn drop(&mut self) {
+        let ret_val = unsafe {
+            // Safety proof:
+            // - `self.ptr` was allocated by a call to `mmap`.
+            // - `self.len` was saved at the same time and it doesn't change throughout the lifetime
+            //   of `self`.
+            libc::munmap(self.ptr.as_ptr() as *mut libc::c_void, self.len)
+        };
+
+        // There is no reason for `munmap` to fail to deallocate a private annonymous mapping
+        // allocated by `mmap`.
+        // However, for the cases when it actually fails prefer to fail, in order to not leak
+        // and exhaust the virtual memory.
+        assert_eq!(ret_val, 0, "munmap failed");
+    }
+}
+
+pub struct ByteBuf {
+    mmap: Option<Mmap>,
+}
+
+impl ByteBuf {
+    pub fn new(len: usize) -> Result<Self, &'static str> {
+        let mmap = if len == 0 {
+            None
+        } else {
+            Some(Mmap::new(len)?)
+        };
+        Ok(Self { mmap })
+    }
+
+    pub fn realloc(&mut self, new_len: usize) -> Result<(), &'static str> {
+        let new_mmap = if new_len == 0 {
+            None
+        } else {
+            let mut new_mmap = Mmap::new(new_len)?;
+            if let Some(cur_mmap) = self.mmap.take() {
+                let src = cur_mmap.as_slice();
+                let dst = new_mmap.as_slice_mut();
+                let amount = src.len().min(dst.len());
+                dst[..amount].copy_from_slice(&src[..amount]);
+            }
+            Some(new_mmap)
+        };
+
+        self.mmap = new_mmap;
+        Ok(())
+    }
+
+    pub fn len(&self) -> usize {
+        self.mmap.as_ref().map(|m| m.len).unwrap_or(0)
+    }
+
+    pub fn as_slice(&self) -> &[u8] {
+        self.mmap.as_ref().map(|m| m.as_slice()).unwrap_or(&[])
+    }
+
+    pub fn as_slice_mut(&mut self) -> &mut [u8] {
+        self.mmap
+            .as_mut()
+            .map(|m| m.as_slice_mut())
+            .unwrap_or(&mut [])
+    }
+
+    pub fn erase(&mut self) -> Result<(), &'static str> {
+        let len = self.len();
+        if len > 0 {
+            // The order is important.
+            //
+            // 1. First we clear, and thus drop, the current mmap if any.
+            // 2. And then we create a new one.
+            //
+            // Otherwise we double the peak memory consumption.
+            self.mmap = None;
+            self.mmap = Some(Mmap::new(len)?);
+        }
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::ByteBuf;
+
+    const PAGE_SIZE: usize = 4096;
+
+    // This is not required since wasm memories can only grow but nice to have.
+    #[test]
+    fn byte_buf_shrink() {
+        let mut byte_buf = ByteBuf::new(PAGE_SIZE * 3).unwrap();
+        byte_buf.realloc(PAGE_SIZE * 2).unwrap();
+    }
+}

src/memory/mod.rs

@@ -1,6 +1,4 @@
-#[allow(unused_imports)]
-use alloc::prelude::v1::*;
-use alloc::rc::Rc;
+use alloc::{rc::Rc, string::ToString, vec::Vec};
 use core::{
     cell::{Cell, RefCell},
     cmp, fmt,
@@ -12,6 +10,16 @@ use parity_wasm::elements::ResizableLimits;
 use value::LittleEndianConvert;
 use Error;
 
+#[cfg(all(unix, not(feature = "vec_memory")))]
+#[path = "mmap_bytebuf.rs"]
+mod bytebuf;
+
+#[cfg(any(not(unix), feature = "vec_memory"))]
+#[path = "vec_bytebuf.rs"]
+mod bytebuf;
+
+use self::bytebuf::ByteBuf;
+
 /// Size of a page of [linear memory][`MemoryInstance`] - 64KiB.
 ///
 /// The size of a memory is always a integer multiple of a page size.
@@ -52,11 +60,10 @@ pub struct MemoryInstance {
     /// Memory limits.
     limits: ResizableLimits,
     /// Linear memory buffer with lazy allocation.
-    buffer: RefCell<Vec<u8>>,
+    buffer: RefCell<ByteBuf>,
     initial: Pages,
     current_size: Cell<usize>,
     maximum: Option<Pages>,
-    lowest_used: Cell<u32>,
 }
 
 impl fmt::Debug for MemoryInstance {
@@ -126,23 +133,24 @@ impl MemoryInstance {
             validation::validate_memory(initial_u32, maximum_u32).map_err(Error::Memory)?;
         }
 
-        let memory = MemoryInstance::new(initial, maximum);
+        let memory = MemoryInstance::new(initial, maximum)?;
         Ok(MemoryRef(Rc::new(memory)))
     }
 
     /// Create new linear memory instance.
-    fn new(initial: Pages, maximum: Option<Pages>) -> Self {
+    fn new(initial: Pages, maximum: Option<Pages>) -> Result<Self, Error> {
         let limits = ResizableLimits::new(initial.0 as u32, maximum.map(|p| p.0 as u32));
 
         let initial_size: Bytes = initial.into();
-        MemoryInstance {
+        Ok(MemoryInstance {
             limits: limits,
-            buffer: RefCell::new(Vec::with_capacity(4096)),
+            buffer: RefCell::new(
+                ByteBuf::new(initial_size.0).map_err(|err| Error::Memory(err.to_string()))?,
+            ),
             initial: initial,
             current_size: Cell::new(initial_size.0),
             maximum: maximum,
-            lowest_used: Cell::new(u32::max_value()),
-        }
+        })
     }
 
     /// Return linear memory limits.
@@ -163,16 +171,6 @@ impl MemoryInstance {
         self.maximum
     }
 
-    /// Returns lowest offset ever written or `u32::max_value()` if none.
-    pub fn lowest_used(&self) -> u32 {
-        self.lowest_used.get()
-    }
-
-    /// Resets tracked lowest offset.
-    pub fn reset_lowest_used(&self, addr: u32) {
-        self.lowest_used.set(addr)
-    }
-
     /// Returns current linear memory size.
     ///
     /// Maximum memory size cannot exceed `65536` pages or 4GiB.
@@ -193,13 +191,7 @@ impl MemoryInstance {
     /// );
     /// ```
     pub fn current_size(&self) -> Pages {
-        Bytes(self.current_size.get()).round_up_to()
-    }
-
-    /// Returns current used memory size in bytes.
-    /// This is one more than the highest memory address that had been written to.
-    pub fn used_size(&self) -> Bytes {
-        Bytes(self.buffer.borrow().len())
+        Bytes(self.buffer.borrow().len()).round_up_to()
     }
 
     /// Get value from memory at given offset.
@@ -207,7 +199,10 @@ impl MemoryInstance {
         let mut buffer = self.buffer.borrow_mut();
         let region =
             self.checked_region(&mut buffer, offset as usize, ::core::mem::size_of::<T>())?;
-        Ok(T::from_little_endian(&buffer[region.range()]).expect("Slice size is checked"))
+        Ok(
+            T::from_little_endian(&buffer.as_slice_mut()[region.range()])
+                .expect("Slice size is checked"),
+        )
     }
 
     /// Copy data from memory at given offset.
@@ -220,7 +215,7 @@ impl MemoryInstance {
         let mut buffer = self.buffer.borrow_mut();
         let region = self.checked_region(&mut buffer, offset as usize, size)?;
 
-        Ok(buffer[region.range()].to_vec())
+        Ok(buffer.as_slice_mut()[region.range()].to_vec())
     }
 
     /// Copy data from given offset in the memory into `target` slice.
@@ -232,7 +227,7 @@ impl MemoryInstance {
         let mut buffer = self.buffer.borrow_mut();
         let region = self.checked_region(&mut buffer, offset as usize, target.len())?;
 
-        target.copy_from_slice(&buffer[region.range()]);
+        target.copy_from_slice(&buffer.as_slice_mut()[region.range()]);
 
         Ok(())
     }
@@ -244,10 +239,7 @@ impl MemoryInstance {
             .checked_region(&mut buffer, offset as usize, value.len())?
             .range();
 
-        if offset < self.lowest_used.get() {
-            self.lowest_used.set(offset);
-        }
-        buffer[range].copy_from_slice(value);
+        buffer.as_slice_mut()[range].copy_from_slice(value);
 
         Ok(())
     }
@@ -258,10 +250,7 @@ impl MemoryInstance {
         let range = self
             .checked_region(&mut buffer, offset as usize, ::core::mem::size_of::<T>())?
             .range();
-        if offset < self.lowest_used.get() {
-            self.lowest_used.set(offset);
-        }
-        value.into_little_endian(&mut buffer[range]);
+        value.into_little_endian(&mut buffer.as_slice_mut()[range]);
         Ok(())
     }
 
@@ -295,19 +284,22 @@ impl MemoryInstance {
         }
 
         let new_buffer_length: Bytes = new_size.into();
+        self.buffer
+            .borrow_mut()
+            .realloc(new_buffer_length.0)
+            .map_err(|err| Error::Memory(err.to_string()))?;
+
         self.current_size.set(new_buffer_length.0);
+
         Ok(size_before_grow)
     }
 
-    fn checked_region<B>(
+    fn checked_region(
         &self,
-        buffer: &mut B,
+        buffer: &mut ByteBuf,
         offset: usize,
         size: usize,
-    ) -> Result<CheckedRegion, Error>
-    where
-        B: ::core::ops::DerefMut<Target = Vec<u8>>,
-    {
+    ) -> Result<CheckedRegion, Error> {
         let end = offset.checked_add(size).ok_or_else(|| {
             Error::Memory(format!(
                 "trying to access memory block of size {} from offset {}",
@@ -315,10 +307,6 @@ impl MemoryInstance {
             ))
         })?;
 
-        if end <= self.current_size.get() && buffer.len() < end {
-            buffer.resize(end, 0);
-        }
-
         if end > buffer.len() {
             return Err(Error::Memory(format!(
                 "trying to access region [{}..{}] in memory [0..{}]",
@@ -334,17 +322,14 @@ impl MemoryInstance {
         })
     }
 
-    fn checked_region_pair<B>(
+    fn checked_region_pair(
         &self,
-        buffer: &mut B,
+        buffer: &mut ByteBuf,
         offset1: usize,
         size1: usize,
         offset2: usize,
         size2: usize,
-    ) -> Result<(CheckedRegion, CheckedRegion), Error>
-    where
-        B: ::core::ops::DerefMut<Target = Vec<u8>>,
-    {
+    ) -> Result<(CheckedRegion, CheckedRegion), Error> {
         let end1 = offset1.checked_add(size1).ok_or_else(|| {
             Error::Memory(format!(
                 "trying to access memory block of size {} from offset {}",
@@ -359,11 +344,6 @@ impl MemoryInstance {
             ))
         })?;
 
-        let max = cmp::max(end1, end2);
-        if max <= self.current_size.get() && buffer.len() < max {
-            buffer.resize(max, 0);
-        }
-
         if end1 > buffer.len() {
             return Err(Error::Memory(format!(
                 "trying to access region [{}..{}] in memory [0..{}]",
@@ -407,14 +387,10 @@ impl MemoryInstance {
         let (read_region, write_region) =
             self.checked_region_pair(&mut buffer, src_offset, len, dst_offset, len)?;
 
-        if dst_offset < self.lowest_used.get() as usize {
-            self.lowest_used.set(dst_offset as u32);
-        }
-
         unsafe {
             ::core::ptr::copy(
-                buffer[read_region.range()].as_ptr(),
-                buffer[write_region.range()].as_mut_ptr(),
+                buffer.as_slice()[read_region.range()].as_ptr(),
+                buffer.as_slice_mut()[write_region.range()].as_mut_ptr(),
                 len,
             )
         }
@@ -450,14 +426,10 @@ impl MemoryInstance {
             )));
         }
 
-        if dst_offset < self.lowest_used.get() as usize {
-            self.lowest_used.set(dst_offset as u32);
-        }
-
         unsafe {
             ::core::ptr::copy_nonoverlapping(
-                buffer[read_region.range()].as_ptr(),
-                buffer[write_region.range()].as_mut_ptr(),
+                buffer.as_slice()[read_region.range()].as_ptr(),
+                buffer.as_slice_mut()[write_region.range()].as_mut_ptr(),
                 len,
             )
         }
@@ -493,11 +465,7 @@ impl MemoryInstance {
             .checked_region(&mut dst_buffer, dst_offset, len)?
             .range();
 
-        if dst_offset < dst.lowest_used.get() as usize {
-            dst.lowest_used.set(dst_offset as u32);
-        }
-
-        dst_buffer[dst_range].copy_from_slice(&src_buffer[src_range]);
+        dst_buffer.as_slice_mut()[dst_range].copy_from_slice(&src_buffer.as_slice()[src_range]);
 
         Ok(())
     }
@@ -514,11 +482,7 @@ impl MemoryInstance {
 
         let range = self.checked_region(&mut buffer, offset, len)?.range();
 
-        if offset < self.lowest_used.get() as usize {
-            self.lowest_used.set(offset as u32);
-        }
-
-        for val in &mut buffer[range] {
+        for val in &mut buffer.as_slice_mut()[range] {
             *val = new_val
         }
         Ok(())
@@ -533,18 +497,28 @@ impl MemoryInstance {
         self.clear(offset, 0, len)
     }
 
+    /// Set every byte in the entire linear memory to 0, preserving its size.
+    ///
+    /// Might be useful for some optimization shenanigans.
+    pub fn erase(&self) -> Result<(), Error> {
+        self.buffer
+            .borrow_mut()
+            .erase()
+            .map_err(|err| Error::Memory(err.to_string()))
+    }
+
     /// Provides direct access to the underlying memory buffer.
     ///
     /// # Panics
     ///
     /// Any call that requires write access to memory (such as [`set`], [`clear`], etc) made within
-    /// the closure will panic. Note that the buffer size may be arbitraty. Proceed with caution.
+    /// the closure will panic.
     ///
     /// [`set`]: #method.get
     /// [`clear`]: #method.set
     pub fn with_direct_access<R, F: FnOnce(&[u8]) -> R>(&self, f: F) -> R {
         let buf = self.buffer.borrow();
-        f(&*buf)
+        f(buf.as_slice())
     }
 
     /// Provides direct mutable access to the underlying memory buffer.
@@ -552,15 +526,13 @@ impl MemoryInstance {
     /// # Panics
     ///
     /// Any calls that requires either read or write access to memory (such as [`get`], [`set`], [`copy`], etc) made
-    /// within the closure will panic. Note that the buffer size may be arbitraty.
-    /// The closure may however resize it. Proceed with caution.
+    /// within the closure will panic. Proceed with caution.
     ///
     /// [`get`]: #method.get
     /// [`set`]: #method.set
-    /// [`copy`]: #method.copy
-    pub fn with_direct_access_mut<R, F: FnOnce(&mut Vec<u8>) -> R>(&self, f: F) -> R {
+    pub fn with_direct_access_mut<R, F: FnOnce(&mut [u8]) -> R>(&self, f: F) -> R {
         let mut buf = self.buffer.borrow_mut();
-        f(&mut buf)
+        f(buf.as_slice_mut())
     }
 }
 
@@ -574,29 +546,21 @@ mod tests {
 
     #[test]
     fn alloc() {
-        #[cfg(target_pointer_width = "64")]
-        let fixtures = &[
+        let mut fixtures = vec![
             (0, None, true),
             (0, Some(0), true),
             (1, None, true),
             (1, Some(1), true),
             (0, Some(1), true),
             (1, Some(0), false),
-            (0, Some(65536), true),
+        ];
+
+        #[cfg(target_pointer_width = "64")]
+        fixtures.extend(&[
             (65536, Some(65536), true),
             (65536, Some(0), false),
             (65536, None, true),
-        ];
-
-        #[cfg(target_pointer_width = "32")]
-        let fixtures = &[
-            (0, None, true),
-            (0, Some(0), true),
-            (1, None, true),
-            (1, Some(1), true),
-            (0, Some(1), true),
-            (1, Some(0), false),
-        ];
+        ]);
 
         for (index, &(initial, maybe_max, expected_ok)) in fixtures.iter().enumerate() {
             let initial: Pages = Pages(initial);
@@ -618,7 +582,7 @@ mod tests {
     }
 
     fn create_memory(initial_content: &[u8]) -> MemoryInstance {
-        let mem = MemoryInstance::new(Pages(1), Some(Pages(1)));
+        let mem = MemoryInstance::new(Pages(1), Some(Pages(1))).unwrap();
         mem.set(0, initial_content)
             .expect("Successful initialize the memory");
         mem
@@ -731,7 +695,7 @@ mod tests {
 
     #[test]
     fn get_into() {
-        let mem = MemoryInstance::new(Pages(1), None);
+        let mem = MemoryInstance::new(Pages(1), None).unwrap();
         mem.set(6, &[13, 17, 129])
             .expect("memory set should not fail");
 
@@ -747,11 +711,19 @@ mod tests {
         let mem = MemoryInstance::alloc(Pages(1), None).unwrap();
         mem.set(100, &[0]).expect("memory set should not fail");
         mem.with_direct_access_mut(|buf| {
-            assert_eq!(buf.len(), 101);
+            assert_eq!(
+                buf.len(),
+                65536,
+                "the buffer length is expected to be 1 page long"
+            );
             buf[..10].copy_from_slice(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
         });
         mem.with_direct_access(|buf| {
-            assert_eq!(buf.len(), 101);
+            assert_eq!(
+                buf.len(),
+                65536,
+                "the buffer length is expected to be 1 page long"
+            );
             assert_eq!(&buf[..10], &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
         });
     }

src/memory/vec_bytebuf.rs

@@ -0,0 +1,39 @@
+//! An implementation of `ByteBuf` based on a plain `Vec`.
+
+use alloc::vec::Vec;
+
+pub struct ByteBuf {
+    buf: Vec<u8>,
+}
+
+impl ByteBuf {
+    pub fn new(len: usize) -> Result<Self, &'static str> {
+        let mut buf = Vec::new();
+        buf.resize(len, 0u8);
+        Ok(Self { buf })
+    }
+
+    pub fn realloc(&mut self, new_len: usize) -> Result<(), &'static str> {
+        self.buf.resize(new_len, 0u8);
+        Ok(())
+    }
+
+    pub fn len(&self) -> usize {
+        self.buf.len()
+    }
+
+    pub fn as_slice(&self) -> &[u8] {
+        self.buf.as_ref()
+    }
+
+    pub fn as_slice_mut(&mut self) -> &mut [u8] {
+        self.buf.as_mut()
+    }
+
+    pub fn erase(&mut self) -> Result<(), &'static str> {
+        for v in &mut self.buf {
+            *v = 0;
+        }
+        Ok(())
+    }
+}

src/module.rs

@@ -1,6 +1,9 @@
-#[allow(unused_imports)]
-use alloc::prelude::v1::*;
-use alloc::rc::Rc;
+use alloc::{
+    borrow::ToOwned,
+    rc::Rc,
+    string::{String, ToString},
+    vec::Vec,
+};
 use core::cell::RefCell;
 use core::fmt;
 use Trap;
@@ -418,7 +421,11 @@ impl ModuleInstance {
             .map(|es| es.entries())
             .unwrap_or(&[])
         {
-            let offset_val = match eval_init_expr(element_segment.offset(), &module_ref) {
+            let offset = element_segment
+                .offset()
+                .as_ref()
+                .expect("passive segments are rejected due to validation");
+            let offset_val = match eval_init_expr(offset, &module_ref) {
                 RuntimeValue::I32(v) => v as u32,
                 _ => panic!("Due to validation elem segment offset should evaluate to i32"),
             };
@@ -447,7 +454,11 @@ impl ModuleInstance {
         }
 
         for data_segment in module.data_section().map(|ds| ds.entries()).unwrap_or(&[]) {
-            let offset_val = match eval_init_expr(data_segment.offset(), &module_ref) {
+            let offset = data_segment
+                .offset()
+                .as_ref()
+                .expect("passive segments are rejected due to validation");
+            let offset_val = match eval_init_expr(offset, &module_ref) {
                 RuntimeValue::I32(v) => v as u32,
                 _ => panic!("Due to validation data segment offset should evaluate to i32"),
             };

src/prepare/compile.rs

@@ -1,5 +1,4 @@
-#[allow(unused_imports)]
-use alloc::prelude::v1::*;
+use alloc::{string::String, vec::Vec};
 
 use parity_wasm::elements::{BlockType, FuncBody, Instruction};
 
@@ -252,13 +251,14 @@ impl Compiler {
                 );
                 self.sink.emit_br_nez(target);
             }
-            BrTable(ref table, default) => {
+            BrTable(ref br_table_data) => {
                 // At this point, the condition value is at the top of the stack.
                 // But at the point of actual jump the condition will already be
                 // popped off.
                 let value_stack_height = context.value_stack.len().saturating_sub(1);
 
-                let targets = table
+                let targets = br_table_data
+                    .table
                     .iter()
                     .map(|depth| {
                         require_target(
@@ -270,7 +270,7 @@ impl Compiler {
                     })
                     .collect::<Result<Vec<_>, _>>();
                 let default_target = require_target(
-                    default,
+                    br_table_data.default,
                     value_stack_height,
                     &context.frame_stack,
                     &self.label_stack,

src/prepare/mod.rs

@@ -1,5 +1,4 @@
-#[allow(unused_imports)]
-use alloc::prelude::v1::*;
+use alloc::vec::Vec;
 
 use crate::{
     isa,

src/runner.rs

@@ -1,5 +1,4 @@
-#[allow(unused_imports)]
-use alloc::prelude::v1::*;
+use alloc::{boxed::Box, vec::Vec};
 use core::fmt;
 use core::ops;
 use core::{u32, usize};
@@ -1290,14 +1289,8 @@ impl FunctionContext {
         debug_assert!(!self.is_initialized);
 
         let num_locals = locals.iter().map(|l| l.count() as usize).sum();
-        let locals = vec![Default::default(); num_locals];
 
-        // TODO: Replace with extend.
-        for local in locals {
-            value_stack
-                .push(local)
-                .map_err(|_| TrapKind::StackOverflow)?;
-        }
+        value_stack.extend(num_locals)?;
 
         self.is_initialized = true;
         Ok(())
@@ -1443,6 +1436,18 @@ impl ValueStack {
         Ok(())
     }
 
+    fn extend(&mut self, len: usize) -> Result<(), TrapKind> {
+        let cells = self
+            .buf
+            .get_mut(self.sp..self.sp + len)
+            .ok_or_else(|| TrapKind::StackOverflow)?;
+        for cell in cells {
+            *cell = Default::default();
+        }
+        self.sp += len;
+        Ok(())
+    }
+
     #[inline]
     fn len(&self) -> usize {
         self.sp
@@ -1493,6 +1498,22 @@ impl StackRecycler {
         }
     }
 
+    /// Clears any values left on the stack to avoid
+    /// leaking them to future export invocations.
+    ///
+    /// This is a secondary defense to prevent modules from
+    /// exploiting faulty stack handling in the interpreter.
+    ///
+    /// Do note that there are additional channels that
+    /// can leak information into an untrusted module.
+    pub fn clear(&mut self) {
+        if let Some(buf) = &mut self.value_stack_buf {
+            for cell in buf.iter_mut() {
+                *cell = RuntimeValueInternal(0);
+            }
+        }
+    }
+
     fn recreate_value_stack(this: &mut Option<&mut Self>) -> ValueStack {
         let limit = this
             .as_ref()
@@ -1526,10 +1547,6 @@ impl StackRecycler {
     }
 
     pub(crate) fn recycle(&mut self, mut interpreter: Interpreter) {
-        for cell in interpreter.value_stack.buf.iter_mut() {
-            *cell = RuntimeValueInternal(0);
-        }
-
         interpreter.call_stack.buf.clear();
 
         self.value_stack_buf = Some(interpreter.value_stack.buf);

src/table.rs

@@ -1,6 +1,4 @@
-#[allow(unused_imports)]
-use alloc::prelude::v1::*;
-use alloc::rc::Rc;
+use alloc::{rc::Rc, vec::Vec};
 use core::cell::RefCell;
 use core::fmt;
 use core::u32;

src/tests/host.rs

@@ -285,7 +285,7 @@ fn resume_call_host_func() {
     let export = instance.export_by_name("test").unwrap();
     let func_instance = export.as_func().unwrap();
 
-    let mut invocation = FuncInstance::invoke_resumable(&func_instance, &[]).unwrap();
+    let mut invocation = FuncInstance::invoke_resumable(&func_instance, &[][..]).unwrap();
     let result = invocation.start_execution(&mut env);
     match result {
         Err(ResumableError::Trap(_)) => {}
@@ -330,7 +330,7 @@ fn resume_call_host_func_type_mismatch() {
         let export = instance.export_by_name("test").unwrap();
         let func_instance = export.as_func().unwrap();
 
-        let mut invocation = FuncInstance::invoke_resumable(&func_instance, &[]).unwrap();
+        let mut invocation = FuncInstance::invoke_resumable(&func_instance, &[][..]).unwrap();
         let result = invocation.start_execution(&mut env);
         match result {
             Err(ResumableError::Trap(_)) => {}

src/value.rs

@@ -368,6 +368,7 @@ impl WrapInto<F32> for F64 {
 macro_rules! impl_try_truncate_into {
     (@primitive $from: ident, $into: ident, $to_primitive:path) => {
         impl TryTruncateInto<$into, TrapKind> for $from {
+            #[cfg(feature = "std")]
             fn try_truncate_into(self) -> Result<$into, TrapKind> {
                 // Casting from a float to an integer will round the float towards zero
                 num_rational::BigRational::from_float(self)
@@ -375,6 +376,23 @@ macro_rules! impl_try_truncate_into {
                     .and_then(|val| $to_primitive(&val))
                     .ok_or(TrapKind::InvalidConversionToInt)
             }
+            #[cfg(not(feature = "std"))]
+            fn try_truncate_into(self) -> Result<$into, TrapKind> {
+                // Casting from a float to an integer will round the float towards zero
+                // NOTE: currently this will cause Undefined Behavior if the rounded value cannot be represented by the
+                // target integer type. This includes Inf and NaN. This is a bug and will be fixed.
+                if self.is_nan() || self.is_infinite() {
+                    return Err(TrapKind::InvalidConversionToInt);
+                }
+
+                // range check
+                let result = self as $into;
+                if result as $from != self.trunc() {
+                    return Err(TrapKind::InvalidConversionToInt);
+                }
+
+                Ok(self as $into)
+            }
         }
     };
     (@wrapped $from:ident, $intermediate:ident, $into:ident) => {
@@ -819,15 +837,6 @@ impl_integer!(u32);
 impl_integer!(i64);
 impl_integer!(u64);
 
-// Use std float functions in std environment.
-// And libm's implementation in no_std
-#[cfg(feature = "std")]
-macro_rules! call_math {
-    ($op:ident, $e:expr, $fXX:ident, $FXXExt:ident) => {
-        $fXX::$op($e)
-    };
-}
-#[cfg(not(feature = "std"))]
 macro_rules! call_math {
     ($op:ident, $e:expr, $fXX:ident, $FXXExt:ident) => {
         ::libm::$FXXExt::$op($e)

tests/spec/run.rs

@@ -18,6 +18,7 @@ fn spec_to_runtime_value(val: Value<u32, u64>) -> RuntimeValue {
         Value::I64(v) => RuntimeValue::I64(v),
         Value::F32(v) => RuntimeValue::F32(v.into()),
         Value::F64(v) => RuntimeValue::F64(v.into()),
+        Value::V128(_) => panic!("v128 is not supported"),
     }
 }
 

validation/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "wasmi-validation"
-version = "0.1.0"
+version = "0.2.0"
 authors = ["Parity Technologies <admin@parity.io>"]
 edition = "2018"
 license = "MIT/Apache-2.0"
@@ -8,7 +8,7 @@ repository = "https://github.com/paritytech/wasmi"
 description = "Wasm code validator"
 
 [dependencies]
-parity-wasm = { version = "0.31", default-features = false }
+parity-wasm = { version = "0.40.1", default-features = false }
 
 [dev-dependencies]
 assert_matches = "1.1"

validation/src/context.rs

@@ -1,6 +1,5 @@
 use crate::Error;
-#[allow(unused_imports)]
-use alloc::prelude::v1::*;
+use alloc::vec::Vec;
 use parity_wasm::elements::{
     BlockType, FunctionType, GlobalType, MemoryType, TableType, ValueType,
 };

validation/src/func.rs

@@ -1,6 +1,3 @@
-#[allow(unused_imports)]
-use alloc::prelude::v1::*;
-
 use crate::{
     context::ModuleContext, stack::StackWithLimit, util::Locals, Error, FuncValidator,
     DEFAULT_MEMORY_INDEX, DEFAULT_TABLE_INDEX,
@@ -269,8 +266,8 @@ impl<'a> FunctionValidationContext<'a> {
             BrIf(depth) => {
                 self.validate_br_if(depth)?;
             }
-            BrTable(ref table, default) => {
-                self.validate_br_table(table, default)?;
+            BrTable(ref br_table_data) => {
+                self.validate_br_table(&*br_table_data.table, br_table_data.default)?;
                 make_top_frame_polymorphic(&mut self.value_stack, &mut self.frame_stack);
             }
             Return => {

validation/src/lib.rs

@@ -2,8 +2,6 @@
 // #![warn(missing_docs)]
 
 #![cfg_attr(not(feature = "std"), no_std)]
-//// alloc is required in no_std
-#![cfg_attr(not(feature = "std"), feature(alloc, alloc_prelude))]
 
 #[cfg(not(feature = "std"))]
 #[macro_use]
@@ -21,8 +19,7 @@ pub const DEFAULT_TABLE_INDEX: u32 = 0;
 /// Maximal number of pages that a wasm instance supports.
 pub const LINEAR_MEMORY_MAX_PAGES: u32 = 65536;
 
-#[allow(unused_imports)]
-use alloc::prelude::v1::*;
+use alloc::{string::String, vec::Vec};
 use core::fmt;
 #[cfg(feature = "std")]
 use std::error;
@@ -322,7 +319,11 @@ pub fn validate_module<V: Validator>(module: &Module) -> Result<V::Output, Error
     if let Some(data_section) = module.data_section() {
         for data_segment in data_section.entries() {
             context.require_memory(data_segment.index())?;
-            let init_ty = expr_const_type(data_segment.offset(), context.globals())?;
+            let offset = data_segment
+                .offset()
+                .as_ref()
+                .ok_or_else(|| Error("passive memory segments are not supported".into()))?;
+            let init_ty = expr_const_type(&offset, context.globals())?;
             if init_ty != ValueType::I32 {
                 return Err(Error("segment offset should return I32".into()));
             }
@@ -333,8 +334,11 @@ pub fn validate_module<V: Validator>(module: &Module) -> Result<V::Output, Error
     if let Some(element_section) = module.elements_section() {
         for element_segment in element_section.entries() {
             context.require_table(element_segment.index())?;
-
-            let init_ty = expr_const_type(element_segment.offset(), context.globals())?;
+            let offset = element_segment
+                .offset()
+                .as_ref()
+                .ok_or_else(|| Error("passive element segments are not supported".into()))?;
+            let init_ty = expr_const_type(&offset, context.globals())?;
             if init_ty != ValueType::I32 {
                 return Err(Error("segment offset should return I32".into()));
             }

validation/src/stack.rs

@@ -1,5 +1,4 @@
-#[allow(unused_imports)]
-use alloc::prelude::v1::*;
+use alloc::{string::String, vec::Vec};
 
 use core::fmt;
 #[cfg(feature = "std")]

validation/src/util.rs

@@ -1,6 +1,5 @@
 use crate::Error;
-#[allow(unused_imports)]
-use alloc::prelude::v1::*;
+use alloc::string::String;
 use parity_wasm::elements::{Local, ValueType};
 
 #[cfg(test)]