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Remove dependency on the region crate (#4407)

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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.
This commit is contained in:
Alex Crichton
2022-07-07 16:28:25 -05:00
committed by GitHub
parent 9c43749dfe
commit 601e8f3094
14 changed files with 134 additions and 121 deletions
Download Patch File Download Diff File Expand all files Collapse all files

19
crates/runtime/src/instance/allocator/pooling.rs
View File

@@ -30,9 +30,6 @@ cfg_if::cfg_if! {
if #[cfg(windows)] {
mod windows;
use windows as imp;
} else if #[cfg(target_os = "linux")] {
mod linux;
use linux as imp;
} else {
mod unix;
use unix as imp;
@@ -217,7 +214,7 @@ impl InstancePool {
instance_limits: &InstanceLimits,
tunables: &Tunables,
) -> Result<Self> {
let page_size = region::page::size();
let page_size = crate::page_size();
let instance_size = round_up_to_pow2(instance_limits.size, mem::align_of::<Instance>());
@@ -692,7 +689,7 @@ impl MemoryPool {
};
assert!(
memory_size % region::page::size() == 0,
memory_size % crate::page_size() == 0,
"memory size {} is not a multiple of system page size",
memory_size
);
@@ -828,7 +825,7 @@ struct TablePool {
impl TablePool {
fn new(instance_limits: &InstanceLimits) -> Result<Self> {
let page_size = region::page::size();
let page_size = crate::page_size();
let table_size = round_up_to_pow2(
mem::size_of::<*mut u8>()
@@ -895,7 +892,9 @@ struct StackPool {
#[cfg(all(feature = "async", unix))]
impl StackPool {
fn new(instance_limits: &InstanceLimits, stack_size: usize) -> Result<Self> {
let page_size = region::page::size();
use rustix::mm::{mprotect, MprotectFlags};
let page_size = crate::page_size();
// Add a page to the stack size for the guard page when using fiber stacks
let stack_size = if stack_size == 0 {
@@ -921,7 +920,7 @@ impl StackPool {
for i in 0..max_instances {
// Make the stack guard page inaccessible
let bottom_of_stack = mapping.as_mut_ptr().add(i * stack_size);
region::protect(bottom_of_stack, page_size, region::Protection::NONE)
mprotect(bottom_of_stack.cast(), page_size, MprotectFlags::empty())
.context("failed to protect stack guard page")?;
}
}
@@ -1298,7 +1297,7 @@ mod test {
..Default::default()
})?;
let host_page_size = region::page::size();
let host_page_size = crate::page_size();
assert_eq!(pool.table_size, host_page_size);
assert_eq!(pool.max_tables, 4);
@@ -1335,7 +1334,7 @@ mod test {
1,
)?;
let native_page_size = region::page::size();
let native_page_size = crate::page_size();
assert_eq!(pool.stack_size, 2 * native_page_size);
assert_eq!(pool.max_instances, 10);
assert_eq!(pool.page_size, native_page_size);