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native.rs
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92 lines (78 loc) · 2.75 KB
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use std::{io::Write, sync::Arc};
use anyhow::Context;
use libloading::Library;
use tempfile::{NamedTempFile, TempPath};
use crate::context::{PluginContext, PluginPtrMut};
/// A native plugin loaded from a shared library
pub struct NativePlugin {
/// The tempfile containing the shared library.
tempfile: TempPath,
/// The plugin's shared library.
library: Library,
/// The plugin's exported quill_setup function.
///
/// Parameters:
/// 1. Host context pointer
/// 2. Pointer to bincode-encoded vtable
/// 3. Length of bincode-encoded vtable
enable: unsafe extern "C" fn(*const u8, *const u8, usize),
/// The plugin's exported quill_run_system function.
///
/// Parameters:
/// 1. Plugin data pointer for this system
run_system: unsafe extern "C" fn(*mut u8),
}
impl NativePlugin {
pub fn load(module: &[u8]) -> anyhow::Result<Self> {
// Libraries have to be loaded from files, so
// we'll create a tempfile containing the module bytes.
let mut tempfile = NamedTempFile::new()?;
tempfile.write_all(module)?;
tempfile.flush()?;
let path = tempfile.into_temp_path();
// SAFETY: Library::new() is unsafe because
// the loaded module can execute arbitrary
// code. Since native plugins are trusted,
// this is sound.
let library = unsafe { Library::new(&path)? };
// SAFETY: these functions will not be accessed after the plugin is unloaded.
let enable = unsafe {
*library
.get("quill_setup".as_bytes())
.context("plugin is missing quill_setup export")?
};
let run_system = unsafe {
*library
.get("quill_run_system".as_bytes())
.context("plugin is missing quill_run_system export")?
};
Ok(Self {
tempfile: path,
library,
enable,
run_system,
})
}
pub fn enable(&self, context: Arc<PluginContext>) {
let vtable = self.generate_vtable();
let context_ptr = Arc::as_ptr(&context);
// Ensure context stays alive
std::mem::forget(context);
// SAFETY: we assume the plugin is sound.
unsafe {
(self.enable)(
context_ptr.cast::<u8>(),
vtable.as_ptr(),
vtable.len() as usize,
)
}
}
fn generate_vtable(&self) -> Vec<u8> {
let vtable = crate::host_calls::generate_vtable();
bincode::serialize(&vtable).expect("can't serialize vtable")
}
pub fn run_system(&self, data: PluginPtrMut<u8>) {
// SAFETY: we assume the plugin is sound.
unsafe { (self.run_system)(data.as_native()) }
}
}