47490b4383
* Use rsix to make system calls in Wasmtime. `rsix` is a system call wrapper crate that we use in `wasi-common`, which can provide the following advantages in the rest of Wasmtime: - It eliminates some `unsafe` blocks in Wasmtime's code. There's still an `unsafe` block in the library, but this way, the `unsafe` is factored out and clearly scoped. - And, it makes error handling more consistent, factoring out code for checking return values and `io::Error::last_os_error()`, and code that does `errno::set_errno(0)`. This doesn't cover *all* system calls; `rsix` doesn't implement signal-handling APIs, and this doesn't cover calls made through `std` or crates like `userfaultfd`, `rand`, and `region`.
57 lines
1.5 KiB
Rust
57 lines
1.5 KiB
Rust
use anyhow::{Context, Result};
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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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if protect {
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region::protect(addr, len, region::Protection::NONE)
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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 the pages to 0 on next access
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rsix::io::madvise(addr as _, len, rsix::io::Advice::LinuxDontNeed)
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.context("madvise failed to decommit: {}")?;
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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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region::protect(addr, len, region::Protection::READ_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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