601e8f3094
This commit removes Wasmtime's dependency on the `region` crate. The motivation for this came about when I was updating dependencies and saw that `region` had a new major version at 3.0.0 as opposed to our currently used 2.3 track. In reviewing the use cases of `region` within Wasmtime I found two trends in particular which motivated this commit: * Some unix-specific areas of `wasmtime_runtime` use `rustix::mm::mprotect` instead of `region::protect` already. This means that the usage of `region::protect` for changing virtual memory protections was already inconsistent. * Many uses of `region::protect` were already in unix-specific regions which could make use of `rustix`. Overall I opted to remove the dependency on the `region` crate to avoid chasing its versions over time. Unix-specific changes of protections were easily changed to `rustix::mm::mprotect`. There were two locations where a windows/unix split is now required and I subjectively ruled "that seems ok". Finally removing `region` also meant that the "what is the current page size" query needed to be inlined into `wasmtime_runtime`, which I have also subjectively ruled "that seems fine". Finally one final refactoring here was that the `unix.rs` and `linux.rs` split for the pooling allocator was merged. These two files already only differed in one function so I slapped a `cfg_if!` in there to help reduce the duplication.
83 lines
2.5 KiB
Rust
83 lines
2.5 KiB
Rust
use anyhow::{Context, Result};
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use rustix::mm::{mprotect, MprotectFlags};
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fn decommit(addr: *mut u8, len: usize, protect: bool) -> Result<()> {
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if len == 0 {
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return Ok(());
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}
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unsafe {
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cfg_if::cfg_if! {
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if #[cfg(target_os = "linux")] {
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use rustix::mm::{madvise, Advice};
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if protect {
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mprotect(addr.cast(), len, MprotectFlags::empty())
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.context("failed to protect memory pages")?;
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}
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// On Linux, this is enough to cause the kernel to initialize
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// the pages to 0 on next access
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madvise(addr as _, len, Advice::LinuxDontNeed)
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.context("madvise failed to decommit: {}")?;
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} else {
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use rustix::mm::{mmap_anonymous, ProtFlags, MapFlags};
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// By creating a new mapping at the same location, this will
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// discard the mapping for the pages in the given range.
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// The new mapping will be to the CoW zero page, so this
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// effectively zeroes the pages.
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mmap_anonymous(
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addr as _,
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len,
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if protect {
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ProtFlags::empty()
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} else {
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ProtFlags::READ | ProtFlags::WRITE
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},
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MapFlags::PRIVATE | MapFlags::FIXED,
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)
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.context("mmap failed to remap pages: {}")?;
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}
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}
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}
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Ok(())
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}
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pub fn commit_memory_pages(addr: *mut u8, len: usize) -> Result<()> {
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if len == 0 {
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return Ok(());
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}
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// Just change the protection level to READ|WRITE
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unsafe {
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mprotect(addr.cast(), len, MprotectFlags::READ | MprotectFlags::WRITE)
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.context("failed to make linear memory pages read/write")
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}
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}
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pub fn decommit_memory_pages(addr: *mut u8, len: usize) -> Result<()> {
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decommit(addr, len, true)
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}
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pub fn commit_table_pages(_addr: *mut u8, _len: usize) -> Result<()> {
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// A no-op as table pages remain READ|WRITE
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Ok(())
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}
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pub fn decommit_table_pages(addr: *mut u8, len: usize) -> Result<()> {
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decommit(addr, len, false)
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}
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#[cfg(feature = "async")]
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pub fn commit_stack_pages(_addr: *mut u8, _len: usize) -> Result<()> {
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// A no-op as stack pages remain READ|WRITE
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Ok(())
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}
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#[cfg(feature = "async")]
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pub fn decommit_stack_pages(addr: *mut u8, len: usize) -> Result<()> {
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decommit(addr, len, false)
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}
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