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* Option for host managed memory * Rename Allocator to MemoryCreator * Create LinearMemory and MemoryCreator traits in api * Leave only one as_ptr function in LinearMemory trait * Memory creator test * Update comments/docs for LinearMemory and MemoryCreator traits * Add guard page to the custom memory example * Remove mut from LinearMemory trait as_ptr * Host_memory_grow testpull/1477/head
Maciej Kot
5 years ago
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GitHub
GitHub
11 changed files with 356 additions and 17 deletions
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#[cfg(not(target_os = "windows"))] |
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mod not_for_windows { |
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use wasmtime::*; |
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use wasmtime_environ::{WASM_MAX_PAGES, WASM_PAGE_SIZE}; |
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use libc::c_void; |
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use libc::MAP_FAILED; |
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use libc::{mmap, mprotect, munmap}; |
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use libc::{sysconf, _SC_PAGESIZE}; |
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use libc::{MAP_ANON, MAP_PRIVATE, PROT_NONE, PROT_READ, PROT_WRITE}; |
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use std::cell::RefCell; |
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use std::io::Error; |
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use std::ptr::null_mut; |
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use std::sync::{Arc, Mutex}; |
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struct CustomMemory { |
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mem: *mut c_void, |
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size: usize, |
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used_wasm_pages: RefCell<u32>, |
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glob_page_counter: Arc<Mutex<u64>>, |
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} |
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impl CustomMemory { |
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unsafe fn new( |
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num_wasm_pages: u32, |
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max_wasm_pages: u32, |
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glob_counter: Arc<Mutex<u64>>, |
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) -> Self { |
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let page_size = sysconf(_SC_PAGESIZE) as usize; |
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let guard_size = page_size; |
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let size = max_wasm_pages as usize * WASM_PAGE_SIZE as usize + guard_size; |
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let used_size = num_wasm_pages as usize * WASM_PAGE_SIZE as usize; |
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assert_eq!(size % page_size, 0); // we rely on WASM_PAGE_SIZE being multiple of host page size
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let mem = mmap(null_mut(), size, PROT_NONE, MAP_PRIVATE | MAP_ANON, -1, 0); |
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assert_ne!(mem, MAP_FAILED, "mmap failed: {}", Error::last_os_error()); |
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let r = mprotect(mem, used_size, PROT_READ | PROT_WRITE); |
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assert_eq!(r, 0, "mprotect failed: {}", Error::last_os_error()); |
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*glob_counter.lock().unwrap() += num_wasm_pages as u64; |
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Self { |
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mem, |
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size, |
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used_wasm_pages: RefCell::new(num_wasm_pages), |
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glob_page_counter: glob_counter, |
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} |
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} |
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} |
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impl Drop for CustomMemory { |
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fn drop(&mut self) { |
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let n = *self.used_wasm_pages.borrow() as u64; |
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*self.glob_page_counter.lock().unwrap() -= n; |
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let r = unsafe { munmap(self.mem, self.size) }; |
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assert_eq!(r, 0, "munmap failed: {}", Error::last_os_error()); |
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} |
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} |
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unsafe impl LinearMemory for CustomMemory { |
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fn size(&self) -> u32 { |
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*self.used_wasm_pages.borrow() |
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} |
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fn grow(&self, delta: u32) -> Option<u32> { |
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let delta_size = (delta as usize).checked_mul(WASM_PAGE_SIZE as usize)?; |
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let prev_pages = *self.used_wasm_pages.borrow(); |
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let prev_size = (prev_pages as usize).checked_mul(WASM_PAGE_SIZE as usize)?; |
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let new_pages = prev_pages.checked_add(delta)?; |
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let new_size = (new_pages as usize).checked_mul(WASM_PAGE_SIZE as usize)?; |
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let guard_size = unsafe { sysconf(_SC_PAGESIZE) as usize }; |
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if new_size > self.size - guard_size { |
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return None; |
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} |
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unsafe { |
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let start = (self.mem as *mut u8).add(prev_size) as _; |
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let r = mprotect(start, delta_size, PROT_READ | PROT_WRITE); |
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assert_eq!(r, 0, "mprotect failed: {}", Error::last_os_error()); |
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} |
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*self.glob_page_counter.lock().unwrap() += delta as u64; |
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*self.used_wasm_pages.borrow_mut() = new_pages; |
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Some(prev_pages) |
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} |
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fn as_ptr(&self) -> *mut u8 { |
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self.mem as *mut u8 |
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} |
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} |
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struct CustomMemoryCreator { |
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pub num_created_memories: Mutex<usize>, |
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pub num_total_pages: Arc<Mutex<u64>>, |
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} |
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impl CustomMemoryCreator { |
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pub fn new() -> Self { |
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Self { |
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num_created_memories: Mutex::new(0), |
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num_total_pages: Arc::new(Mutex::new(0)), |
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} |
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} |
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} |
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unsafe impl MemoryCreator for CustomMemoryCreator { |
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fn new_memory(&self, ty: MemoryType) -> Result<Box<dyn LinearMemory>, String> { |
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let max = ty.limits().max().unwrap_or(WASM_MAX_PAGES); |
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unsafe { |
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let mem = Box::new(CustomMemory::new( |
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ty.limits().min(), |
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max, |
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self.num_total_pages.clone(), |
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)); |
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*self.num_created_memories.lock().unwrap() += 1; |
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Ok(mem) |
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} |
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} |
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} |
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#[test] |
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fn host_memory() -> anyhow::Result<()> { |
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let mem_creator = Arc::new(CustomMemoryCreator::new()); |
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let mut config = Config::default(); |
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config.with_host_memory(mem_creator.clone()); |
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let engine = Engine::new(&config); |
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let store = Store::new(&engine); |
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let module = Module::new( |
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&store, |
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r#" |
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(module |
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(memory (export "memory") 1) |
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) |
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"#, |
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)?; |
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Instance::new(&module, &[])?; |
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assert_eq!(*mem_creator.num_created_memories.lock().unwrap(), 1); |
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Ok(()) |
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} |
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#[test] |
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fn host_memory_grow() -> anyhow::Result<()> { |
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let mem_creator = Arc::new(CustomMemoryCreator::new()); |
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let mut config = Config::default(); |
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config.with_host_memory(mem_creator.clone()); |
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let engine = Engine::new(&config); |
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let store = Store::new(&engine); |
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let module = Module::new( |
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&store, |
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r#" |
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(module |
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(func $f (drop (memory.grow (i32.const 1)))) |
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(memory (export "memory") 1 2) |
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(start $f) |
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) |
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"#, |
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)?; |
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let instance1 = Instance::new(&module, &[])?; |
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let instance2 = Instance::new(&module, &[])?; |
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assert_eq!(*mem_creator.num_created_memories.lock().unwrap(), 2); |
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assert_eq!( |
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instance2 |
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.get_export("memory") |
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.unwrap() |
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.memory() |
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.unwrap() |
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.size(), |
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2 |
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); |
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// we take the lock outside the assert, so it won't get poisoned on assert failure
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let tot_pages = *mem_creator.num_total_pages.lock().unwrap(); |
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assert_eq!(tot_pages, 4); |
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drop(instance1); |
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let tot_pages = *mem_creator.num_total_pages.lock().unwrap(); |
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assert_eq!(tot_pages, 2); |
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Ok(()) |
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} |
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} |
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