Use mmap for allocation (#190)
This commit is contained in:
Sergei Pepyakin
GitHub
parent
f29f301e6e
commit
1a6e5b30de
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@ -11,6 +11,8 @@ matrix:
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- rust: stable
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- rust: stable
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env: TARGET=armv7-unknown-linux-gnueabihf
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allow_failures:
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- rust: nightly
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install:
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- if [ "$TRAVIS_RUST_VERSION" == "nightly" ]; then rustup target add wasm32-unknown-unknown; fi
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@ -26,6 +28,8 @@ script:
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- if [ "$TRAVIS_RUST_VERSION" == "nightly" ]; then cargo check --benches --manifest-path=benches/Cargo.toml; fi
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# Make sure `no_std` version checks.
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- if [ "$TRAVIS_RUST_VERSION" == "nightly" ]; then cargo +nightly check --no-default-features --features core; fi
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# Check that `vec_memory` feature works.
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- cargo check --features vec_memory
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- travis_wait 60 ./test.sh
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- ./doc.sh
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@ -17,6 +17,7 @@ memory_units = "0.3.0"
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libm = { version = "0.1.2", optional = true }
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num-rational = "0.2.2"
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num-traits = "0.2.8"
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libc = "0.2.58"
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[dev-dependencies]
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assert_matches = "1.1"
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@ -37,6 +38,12 @@ core = [
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"wasmi-validation/core",
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"libm"
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]
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# Enforce using the linear memory implementation based on `Vec` instead of
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# mmap on unix systems.
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#
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# Useful for tests and if you need to minimize unsafe usage at the cost of performance on some
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# workloads.
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vec_memory = []
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[workspace]
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members = ["validation"]
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@ -0,0 +1,189 @@
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//! An implementation of a `ByteBuf` based on virtual memory.
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//!
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//! This implementation uses `mmap` on POSIX systems (and should use `VirtualAlloc` on windows).
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//! There are possibilities to improve the performance for the reallocating case by reserving
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//! memory up to maximum. This might be a problem for systems that don't have a lot of virtual
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//! memory (i.e. 32-bit platforms).
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use std::ptr::{self, NonNull};
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use std::slice;
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struct Mmap {
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/// The pointer that points to the start of the mapping.
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///
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/// This value doesn't change after creation.
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ptr: NonNull<u8>,
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/// The length of this mapping.
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///
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/// Cannot be more than `isize::max_value()`. This value doesn't change after creation.
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len: usize,
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}
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impl Mmap {
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/// Create a new mmap mapping
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///
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/// Returns `Err` if:
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/// - `len` should not exceed `isize::max_value()`
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/// - `len` should be greater than 0.
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/// - `mmap` returns an error (almost certainly means out of memory).
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fn new(len: usize) -> Result<Self, &'static str> {
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if len > isize::max_value() as usize {
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return Err("`len` should not exceed `isize::max_value()`");
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}
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if len == 0 {
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return Err("`len` should be greater than 0");
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}
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let ptr_or_err = unsafe {
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// Safety Proof:
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// There are not specific safety proofs are required for this call, since the call
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// by itself can't invoke any safety problems (however, misusing its result can).
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libc::mmap(
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// `addr` - let the system to choose the address at which to create the mapping.
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ptr::null_mut(),
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// the length of the mapping in bytes.
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len,
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// `prot` - protection flags: READ WRITE !EXECUTE
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libc::PROT_READ | libc::PROT_WRITE,
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// `flags`
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// `MAP_ANON` - mapping is not backed by any file and initial contents are
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// initialized to zero.
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// `MAP_PRIVATE` - the mapping is private to this process.
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libc::MAP_ANON | libc::MAP_PRIVATE,
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// `fildes` - a file descriptor. Pass -1 as this is required for some platforms
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// when the `MAP_ANON` is passed.
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-1,
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// `offset` - offset from the file.
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0,
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)
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};
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match ptr_or_err {
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// With the current parameters, the error can only be returned in case of insufficient
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// memory.
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libc::MAP_FAILED => Err("mmap returned an error"),
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_ => {
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let ptr = NonNull::new(ptr_or_err as *mut u8).ok_or("mmap returned 0")?;
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Ok(Self { ptr, len })
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}
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}
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}
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fn as_slice(&self) -> &[u8] {
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unsafe {
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// Safety Proof:
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// - Aliasing guarantees of `self.ptr` are not violated since `self` is the only owner.
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// - This pointer was allocated for `self.len` bytes and thus is a valid slice.
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// - `self.len` doesn't change throughout the lifetime of `self`.
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// - The value is returned valid for the duration of lifetime of `self`.
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// `self` cannot be destroyed while the returned slice is alive.
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// - `self.ptr` is of `NonNull` type and thus `.as_ptr()` can never return NULL.
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// - `self.len` cannot be larger than `isize::max_value()`.
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slice::from_raw_parts(self.ptr.as_ptr(), self.len)
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}
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}
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fn as_slice_mut(&mut self) -> &mut [u8] {
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unsafe {
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// Safety Proof:
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// - See the proof for `Self::as_slice`
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// - Additionally, it is not possible to obtain two mutable references for `self.ptr`
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slice::from_raw_parts_mut(self.ptr.as_ptr(), self.len)
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}
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}
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}
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impl Drop for Mmap {
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fn drop(&mut self) {
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let ret_val = unsafe {
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// Safety proof:
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// - `self.ptr` was allocated by a call to `mmap`.
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// - `self.len` was saved at the same time and it doesn't change throughout the lifetime
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// of `self`.
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libc::munmap(self.ptr.as_ptr() as *mut libc::c_void, self.len)
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};
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// There is no reason for `munmap` to fail to deallocate a private annonymous mapping
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// allocated by `mmap`.
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// However, for the cases when it actually fails prefer to fail, in order to not leak
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// and exhaust the virtual memory.
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assert_eq!(ret_val, 0, "munmap failed");
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}
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}
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pub struct ByteBuf {
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mmap: Option<Mmap>,
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}
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impl ByteBuf {
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pub fn new(len: usize) -> Result<Self, &'static str> {
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let mmap = if len == 0 {
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None
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} else {
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Some(Mmap::new(len)?)
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};
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Ok(Self { mmap })
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}
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pub fn realloc(&mut self, new_len: usize) -> Result<(), &'static str> {
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let new_mmap = if new_len == 0 {
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None
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} else {
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let mut new_mmap = Mmap::new(new_len)?;
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if let Some(cur_mmap) = self.mmap.take() {
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let src = cur_mmap.as_slice();
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let dst = new_mmap.as_slice_mut();
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let amount = src.len().min(dst.len());
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dst[..amount].copy_from_slice(&src[..amount]);
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}
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Some(new_mmap)
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};
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self.mmap = new_mmap;
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Ok(())
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}
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pub fn len(&self) -> usize {
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self.mmap.as_ref().map(|m| m.len).unwrap_or(0)
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}
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pub fn as_slice(&self) -> &[u8] {
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self.mmap.as_ref().map(|m| m.as_slice()).unwrap_or(&[])
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}
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pub fn as_slice_mut(&mut self) -> &mut [u8] {
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self.mmap
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.as_mut()
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.map(|m| m.as_slice_mut())
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.unwrap_or(&mut [])
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}
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pub fn erase(&mut self) -> Result<(), &'static str> {
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let len = self.len();
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if len > 0 {
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// The order is important.
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//
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// 1. First we clear, and thus drop, the current mmap if any.
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// 2. And then we create a new one.
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//
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// Otherwise we double the peak memory consumption.
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self.mmap = None;
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self.mmap = Some(Mmap::new(len)?);
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}
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Ok(())
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}
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}
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#[cfg(test)]
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mod tests {
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use super::ByteBuf;
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const PAGE_SIZE: usize = 4096;
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// This is not required since wasm memories can only grow but nice to have.
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#[test]
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fn byte_buf_shrink() {
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let mut byte_buf = ByteBuf::new(PAGE_SIZE * 3).unwrap();
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byte_buf.realloc(PAGE_SIZE * 2).unwrap();
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}
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}
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@ -12,6 +12,16 @@ use parity_wasm::elements::ResizableLimits;
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use value::LittleEndianConvert;
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use Error;
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#[cfg(all(unix, not(feature = "vec_memory")))]
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#[path = "mmap_bytebuf.rs"]
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mod bytebuf;
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#[cfg(any(not(unix), feature = "vec_memory"))]
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#[path = "vec_bytebuf.rs"]
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mod bytebuf;
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use self::bytebuf::ByteBuf;
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/// Size of a page of [linear memory][`MemoryInstance`] - 64KiB.
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///
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/// The size of a memory is always a integer multiple of a page size.
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@ -52,11 +62,10 @@ pub struct MemoryInstance {
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/// Memory limits.
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limits: ResizableLimits,
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/// Linear memory buffer with lazy allocation.
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buffer: RefCell<Vec<u8>>,
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buffer: RefCell<ByteBuf>,
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initial: Pages,
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current_size: Cell<usize>,
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maximum: Option<Pages>,
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lowest_used: Cell<u32>,
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}
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impl fmt::Debug for MemoryInstance {
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@ -126,23 +135,24 @@ impl MemoryInstance {
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validation::validate_memory(initial_u32, maximum_u32).map_err(Error::Memory)?;
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}
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let memory = MemoryInstance::new(initial, maximum);
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let memory = MemoryInstance::new(initial, maximum)?;
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Ok(MemoryRef(Rc::new(memory)))
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}
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/// Create new linear memory instance.
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fn new(initial: Pages, maximum: Option<Pages>) -> Self {
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fn new(initial: Pages, maximum: Option<Pages>) -> Result<Self, Error> {
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let limits = ResizableLimits::new(initial.0 as u32, maximum.map(|p| p.0 as u32));
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let initial_size: Bytes = initial.into();
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MemoryInstance {
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Ok(MemoryInstance {
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limits: limits,
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buffer: RefCell::new(Vec::with_capacity(4096)),
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buffer: RefCell::new(
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ByteBuf::new(initial_size.0).map_err(|err| Error::Memory(err.to_string()))?,
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),
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initial: initial,
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current_size: Cell::new(initial_size.0),
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maximum: maximum,
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lowest_used: Cell::new(u32::max_value()),
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}
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})
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}
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/// Return linear memory limits.
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@ -163,16 +173,6 @@ impl MemoryInstance {
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self.maximum
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}
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/// Returns lowest offset ever written or `u32::max_value()` if none.
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pub fn lowest_used(&self) -> u32 {
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self.lowest_used.get()
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}
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/// Resets tracked lowest offset.
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pub fn reset_lowest_used(&self, addr: u32) {
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self.lowest_used.set(addr)
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}
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/// Returns current linear memory size.
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///
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/// Maximum memory size cannot exceed `65536` pages or 4GiB.
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@ -193,13 +193,7 @@ impl MemoryInstance {
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/// );
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/// ```
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pub fn current_size(&self) -> Pages {
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Bytes(self.current_size.get()).round_up_to()
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}
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/// Returns current used memory size in bytes.
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/// This is one more than the highest memory address that had been written to.
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pub fn used_size(&self) -> Bytes {
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Bytes(self.buffer.borrow().len())
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Bytes(self.buffer.borrow().len()).round_up_to()
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}
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/// Get value from memory at given offset.
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@ -207,7 +201,10 @@ impl MemoryInstance {
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let mut buffer = self.buffer.borrow_mut();
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let region =
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self.checked_region(&mut buffer, offset as usize, ::core::mem::size_of::<T>())?;
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Ok(T::from_little_endian(&buffer[region.range()]).expect("Slice size is checked"))
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Ok(
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T::from_little_endian(&buffer.as_slice_mut()[region.range()])
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.expect("Slice size is checked"),
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)
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}
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/// Copy data from memory at given offset.
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@ -220,7 +217,7 @@ impl MemoryInstance {
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let mut buffer = self.buffer.borrow_mut();
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let region = self.checked_region(&mut buffer, offset as usize, size)?;
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Ok(buffer[region.range()].to_vec())
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Ok(buffer.as_slice_mut()[region.range()].to_vec())
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}
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/// Copy data from given offset in the memory into `target` slice.
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@ -232,7 +229,7 @@ impl MemoryInstance {
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let mut buffer = self.buffer.borrow_mut();
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let region = self.checked_region(&mut buffer, offset as usize, target.len())?;
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target.copy_from_slice(&buffer[region.range()]);
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target.copy_from_slice(&buffer.as_slice_mut()[region.range()]);
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Ok(())
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}
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@ -244,10 +241,7 @@ impl MemoryInstance {
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.checked_region(&mut buffer, offset as usize, value.len())?
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.range();
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if offset < self.lowest_used.get() {
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self.lowest_used.set(offset);
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}
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buffer[range].copy_from_slice(value);
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buffer.as_slice_mut()[range].copy_from_slice(value);
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Ok(())
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}
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@ -258,10 +252,7 @@ impl MemoryInstance {
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let range = self
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.checked_region(&mut buffer, offset as usize, ::core::mem::size_of::<T>())?
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.range();
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if offset < self.lowest_used.get() {
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self.lowest_used.set(offset);
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}
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value.into_little_endian(&mut buffer[range]);
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value.into_little_endian(&mut buffer.as_slice_mut()[range]);
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Ok(())
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}
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@ -295,19 +286,22 @@ impl MemoryInstance {
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}
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let new_buffer_length: Bytes = new_size.into();
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self.buffer
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.borrow_mut()
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.realloc(new_buffer_length.0)
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.map_err(|err| Error::Memory(err.to_string()))?;
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self.current_size.set(new_buffer_length.0);
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Ok(size_before_grow)
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}
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fn checked_region<B>(
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fn checked_region(
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&self,
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buffer: &mut B,
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buffer: &mut ByteBuf,
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offset: usize,
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size: usize,
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) -> Result<CheckedRegion, Error>
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where
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B: ::core::ops::DerefMut<Target = Vec<u8>>,
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{
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) -> Result<CheckedRegion, Error> {
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let end = offset.checked_add(size).ok_or_else(|| {
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Error::Memory(format!(
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"trying to access memory block of size {} from offset {}",
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@ -315,10 +309,6 @@ impl MemoryInstance {
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))
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})?;
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if end <= self.current_size.get() && buffer.len() < end {
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buffer.resize(end, 0);
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}
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if end > buffer.len() {
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return Err(Error::Memory(format!(
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"trying to access region [{}..{}] in memory [0..{}]",
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@ -334,17 +324,14 @@ impl MemoryInstance {
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})
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}
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fn checked_region_pair<B>(
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fn checked_region_pair(
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&self,
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buffer: &mut B,
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buffer: &mut ByteBuf,
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offset1: usize,
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size1: usize,
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offset2: usize,
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size2: usize,
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) -> Result<(CheckedRegion, CheckedRegion), Error>
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where
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B: ::core::ops::DerefMut<Target = Vec<u8>>,
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{
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) -> Result<(CheckedRegion, CheckedRegion), Error> {
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let end1 = offset1.checked_add(size1).ok_or_else(|| {
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Error::Memory(format!(
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"trying to access memory block of size {} from offset {}",
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@ -359,11 +346,6 @@ impl MemoryInstance {
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))
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})?;
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let max = cmp::max(end1, end2);
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if max <= self.current_size.get() && buffer.len() < max {
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buffer.resize(max, 0);
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}
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if end1 > buffer.len() {
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return Err(Error::Memory(format!(
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"trying to access region [{}..{}] in memory [0..{}]",
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|
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@ -407,14 +389,10 @@ impl MemoryInstance {
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let (read_region, write_region) =
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self.checked_region_pair(&mut buffer, src_offset, len, dst_offset, len)?;
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if dst_offset < self.lowest_used.get() as usize {
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self.lowest_used.set(dst_offset as u32);
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}
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unsafe {
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::core::ptr::copy(
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buffer[read_region.range()].as_ptr(),
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buffer[write_region.range()].as_mut_ptr(),
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||||
buffer.as_slice()[read_region.range()].as_ptr(),
|
||||
buffer.as_slice_mut()[write_region.range()].as_mut_ptr(),
|
||||
len,
|
||||
)
|
||||
}
|
||||
|
|
@ -450,14 +428,10 @@ 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 +467,7 @@ 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 +484,7 @@ 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 +499,28 @@ 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 +528,13 @@ 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 +548,21 @@ 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 +584,7 @@ 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 +697,7 @@ 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 +713,19 @@ 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]);
|
||||
});
|
||||
}
|
||||
|
|
@ -0,0 +1,39 @@
|
|||
//! An implementation of `ByteBuf` based on a plain `Vec`.
|
||||
|
||||
use alloc::prelude::v1::*;
|
||||
|
||||
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(())
|
||||
}
|
||||
}
|
||||
Loading…
Reference in New Issue