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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

75
crates/runtime/src/mmap.rs
View File

@@ -41,7 +41,8 @@ impl Mmap {
/// Create a new `Mmap` pointing to at least `size` bytes of page-aligned accessible memory.
pub fn with_at_least(size: usize) -> Result<Self> {
let rounded_size = region::page::ceil(size);
let page_size = crate::page_size();
let rounded_size = (size + (page_size - 1)) & !(page_size - 1);
Self::accessible_reserved(rounded_size, rounded_size)
}
@@ -158,7 +159,7 @@ impl Mmap {
/// must be native page-size multiples.
#[cfg(not(target_os = "windows"))]
pub fn accessible_reserved(accessible_size: usize, mapping_size: usize) -> Result<Self> {
let page_size = region::page::size();
let page_size = crate::page_size();
assert_le!(accessible_size, mapping_size);
assert_eq!(mapping_size & (page_size - 1), 0);
assert_eq!(accessible_size & (page_size - 1), 0);
@@ -226,7 +227,7 @@ impl Mmap {
return Ok(Self::new());
}
let page_size = region::page::size();
let page_size = crate::page_size();
assert_le!(accessible_size, mapping_size);
assert_eq!(mapping_size & (page_size - 1), 0);
assert_eq!(accessible_size & (page_size - 1), 0);
@@ -278,16 +279,22 @@ impl Mmap {
/// `self`'s reserved memory.
#[cfg(not(target_os = "windows"))]
pub fn make_accessible(&mut self, start: usize, len: usize) -> Result<()> {
let page_size = region::page::size();
use rustix::mm::{mprotect, MprotectFlags};
let page_size = crate::page_size();
assert_eq!(start & (page_size - 1), 0);
assert_eq!(len & (page_size - 1), 0);
assert_le!(len, self.len);
assert_le!(start, self.len - len);
// Commit the accessible size.
let ptr = self.ptr as *const u8;
let ptr = self.ptr as *mut u8;
unsafe {
region::protect(ptr.add(start), len, region::Protection::READ_WRITE)?;
mprotect(
ptr.add(start).cast(),
len,
MprotectFlags::READ | MprotectFlags::WRITE,
)?;
}
Ok(())
@@ -303,7 +310,7 @@ impl Mmap {
use std::io;
use windows_sys::Win32::System::Memory::*;
let page_size = region::page::size();
let page_size = crate::page_size();
assert_eq!(start & (page_size - 1), 0);
assert_eq!(len & (page_size - 1), 0);
assert_le!(len, self.len);
@@ -370,11 +377,11 @@ impl Mmap {
assert!(range.end <= self.len());
assert!(range.start <= range.end);
assert!(
range.start % region::page::size() == 0,
range.start % crate::page_size() == 0,
"changing of protections isn't page-aligned",
);
let base = self.as_ptr().add(range.start);
let base = self.as_ptr().add(range.start) as *mut _;
let len = range.end - range.start;
// On Windows when we have a file mapping we need to specifically use
@@ -385,19 +392,23 @@ impl Mmap {
use std::io;
use windows_sys::Win32::System::Memory::*;
if self.file.is_some() {
let mut old = 0;
if VirtualProtect(base as *mut _, len, PAGE_WRITECOPY, &mut old) == 0 {
return Err(io::Error::last_os_error())
.context("failed to change pages to `PAGE_WRITECOPY`");
}
return Ok(());
let mut old = 0;
let result = if self.file.is_some() {
VirtualProtect(base, len, PAGE_WRITECOPY, &mut old)
} else {
VirtualProtect(base, len, PAGE_READWRITE, &mut old)
};
if result == 0 {
return Err(io::Error::last_os_error().into());
}
}
// If we're not on Windows or if we're on Windows with an anonymous
// mapping then we can use the `region` crate.
region::protect(base, len, region::Protection::READ_WRITE)?;
#[cfg(not(windows))]
{
use rustix::mm::{mprotect, MprotectFlags};
mprotect(base, len, MprotectFlags::READ | MprotectFlags::WRITE)?;
}
Ok(())
}
@@ -407,15 +418,29 @@ impl Mmap {
assert!(range.end <= self.len());
assert!(range.start <= range.end);
assert!(
range.start % region::page::size() == 0,
range.start % crate::page_size() == 0,
"changing of protections isn't page-aligned",
);
let base = self.as_ptr().add(range.start) as *mut _;
let len = range.end - range.start;
region::protect(
self.as_ptr().add(range.start),
range.end - range.start,
region::Protection::READ_EXECUTE,
)?;
#[cfg(windows)]
{
use std::io;
use windows_sys::Win32::System::Memory::*;
let mut old = 0;
let result = VirtualProtect(base, len, PAGE_EXECUTE_READ, &mut old);
if result == 0 {
return Err(io::Error::last_os_error().into());
}
}
#[cfg(not(windows))]
{
use rustix::mm::{mprotect, MprotectFlags};
mprotect(base, len, MprotectFlags::READ | MprotectFlags::EXEC)?;
}
Ok(())
}