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* More use of `anyhow`.
* Change `make_accessible` into `protect_linear_memory` to better demonstrate
  what it is used for; this will make the uffd implementation make a little
  more sense.
* Remove `create_memory_map` in favor of just creating the `Mmap` instances in
  the pooling allocator. This also removes the need for `MAP_NORESERVE` in the
  uffd implementation.
* Moar comments.
* Remove `BasePointerIterator` in favor of `impl Iterator`.
* The uffd implementation now only monitors linear memory pages and will only
  receive faults on pages that could potentially be accessible and never on a
  statically known guard page.
* Stop allocating memory or table pools if the maximum limit of the memory or
  table is 0.
This commit is contained in:
Peter Huene
2021-03-04 14:01:42 -08:00
parent a464465e2f
commit ff840b3d3b
11 changed files with 484 additions and 500 deletions
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14
crates/runtime/src/instance.rs
View File

@@ -67,10 +67,10 @@ pub(crate) struct Instance {
/// Hosts can store arbitrary per-instance information here.
host_state: Box<dyn Any>,
/// Stores guard page faults in memory relating to the instance.
/// This is used for the pooling allocator with uffd enabled on Linux.
/// Stores linear memory guard page faults for the pooling allocator with uffd enabled.
/// These pages need to be reset after the signal handler generates the out-of-bounds trap.
#[cfg(all(feature = "uffd", target_os = "linux"))]
guard_page_faults: RefCell<Vec<(*mut u8, usize, unsafe fn(*mut u8, usize) -> bool)>>,
guard_page_faults: RefCell<Vec<(*mut u8, usize, fn(*mut u8, usize) -> anyhow::Result<()>)>>,
/// Additional context used by compiled wasm code. This field is last, and
/// represents a dynamically-sized array that extends beyond the nominal
@@ -821,7 +821,7 @@ impl Instance {
&self,
page_addr: *mut u8,
size: usize,
reset: unsafe fn(*mut u8, usize) -> bool,
reset: fn(*mut u8, usize) -> anyhow::Result<()>,
) {
self.guard_page_faults
.borrow_mut()
@@ -837,11 +837,7 @@ impl Instance {
pub(crate) fn reset_guard_pages(&self) -> anyhow::Result<()> {
let mut faults = self.guard_page_faults.borrow_mut();
for (addr, len, reset) in faults.drain(..) {
unsafe {
if !reset(addr, len) {
anyhow::bail!("failed to reset previously faulted memory guard page");
}
}
reset(addr, len)?;
}
Ok(())

6
crates/runtime/src/instance/allocator.rs
View File

@@ -549,8 +549,10 @@ impl OnDemandInstanceAllocator {
let mut memories: PrimaryMap<DefinedMemoryIndex, _> =
PrimaryMap::with_capacity(module.memory_plans.len() - num_imports);
for plan in &module.memory_plans.values().as_slice()[num_imports..] {
memories
.push(Memory::new_dynamic(plan, creator).map_err(InstantiationError::Resource)?);
memories.push(
Memory::new_dynamic(plan, creator)
.map_err(|e| InstantiationError::Resource(e.to_string()))?,
);
}
Ok(memories)
}

350
crates/runtime/src/instance/allocator/pooling.rs
View File

@@ -31,9 +31,7 @@ cfg_if::cfg_if! {
} else if #[cfg(all(feature = "uffd", target_os = "linux"))] {
mod uffd;
use uffd as imp;
use imp::PageFaultHandler;
use super::{check_init_bounds, initialize_tables};
use wasmtime_environ::MemoryInitialization;
use imp::initialize_memory_pool;
} else if #[cfg(target_os = "linux")] {
mod linux;
use linux as imp;
@@ -43,7 +41,10 @@ cfg_if::cfg_if! {
}
}
use imp::{create_memory_map, decommit, make_accessible};
use imp::{
commit_memory_pages, commit_stack_pages, commit_table_pages, decommit_memory_pages,
decommit_stack_pages, decommit_table_pages,
};
fn round_up_to_pow2(n: usize, to: usize) -> usize {
debug_assert!(to > 0);
@@ -272,9 +273,9 @@ impl Default for InstanceLimits {
Self {
count: 1000,
#[cfg(target_pointer_width = "32")]
memory_reservation_size: 0xA00000,
memory_reservation_size: 10 * (1 << 20), // 10 MiB,
#[cfg(target_pointer_width = "64")]
memory_reservation_size: 0x180000000,
memory_reservation_size: 6 * (1 << 30), // 6 GiB,
}
}
}
@@ -305,45 +306,6 @@ impl Default for PoolingAllocationStrategy {
}
}
// Used to iterate the base address of instance memories and tables.
struct BasePointerIterator {
base: *mut u8,
current: usize,
num: usize,
size: usize,
}
impl BasePointerIterator {
fn new(base: *mut u8, num: usize, size: usize) -> Self {
Self {
base,
current: 0,
num,
size,
}
}
}
impl Iterator for BasePointerIterator {
type Item = *mut u8;
fn next(&mut self) -> Option<Self::Item> {
let current = self.current;
if current == self.num {
return None;
}
self.current += 1;
Some(unsafe { self.base.add(current * self.size) })
}
fn size_hint(&self) -> (usize, Option<usize>) {
let remaining = self.num - self.current;
(remaining, Some(remaining))
}
}
/// Represents a pool of maximal `Instance` structures.
///
/// Each index in the pool provides enough space for a maximal `Instance`
@@ -395,8 +357,11 @@ impl InstancePool {
.checked_mul(max_instances)
.ok_or_else(|| anyhow!("total size of instance data exceeds addressable memory"))?;
let mapping = Mmap::accessible_reserved(allocation_size, allocation_size)
.context("failed to create instance pool mapping")?;
let pool = Self {
mapping: create_memory_map(allocation_size, allocation_size)?,
mapping,
offsets,
instance_size,
max_instances,
@@ -414,15 +379,18 @@ impl InstancePool {
Ok(pool)
}
fn initialize(&self, index: usize, module: &Arc<Module>) {
unsafe fn instance(&self, index: usize) -> &mut Instance {
debug_assert!(index < self.max_instances);
&mut *(self.mapping.as_mut_ptr().add(index * self.instance_size) as *mut Instance)
}
fn initialize(&self, index: usize, module: &Arc<Module>) {
unsafe {
let instance_ptr = self.mapping.as_mut_ptr().add(index * self.instance_size);
let instance = self.instance(index);
// Write a default instance with preallocated memory/table map storage to the ptr
std::ptr::write(
instance_ptr as _,
instance as _,
Instance {
module: module.clone(),
offsets: self.offsets,
@@ -456,9 +424,7 @@ impl InstancePool {
let host_state = std::mem::replace(&mut req.host_state, Box::new(()));
unsafe {
debug_assert!(index < self.max_instances);
let instance =
&mut *(self.mapping.as_mut_ptr().add(index * self.instance_size) as *mut Instance);
let instance = self.instance(index);
instance.module = req.module.clone();
instance.offsets = VMOffsets::new(
@@ -490,47 +456,40 @@ impl InstancePool {
let index = (addr - base) / self.instance_size;
debug_assert!(index < self.max_instances);
unsafe {
// Decommit any linear memories that were used
for (mem, base) in (*handle.instance)
.memories
.values()
.zip(self.memories.get(index))
{
let size = (mem.size() * WASM_PAGE_SIZE) as usize;
if size > 0 {
decommit(base, size);
}
}
let instance = unsafe { &mut *handle.instance };
// Decommit any tables that were used
let table_element_size = max_table_element_size();
for (table, base) in (*handle.instance)
.tables
.values()
.zip(self.tables.get(index))
{
let size = round_up_to_pow2(
table.size() as usize * table_element_size,
self.tables.page_size,
);
if size > 0 {
decommit(base, size);
}
}
// Drop the host state
(*handle.instance).host_state = Box::new(());
// Decommit any linear memories that were used
for (mem, base) in instance.memories.values().zip(self.memories.get(index)) {
let size = (mem.size() * WASM_PAGE_SIZE) as usize;
decommit_memory_pages(base, size).unwrap();
}
{
self.free_list.lock().unwrap().push(index);
instance.memories.clear();
instance.dropped_data.borrow_mut().clear();
// Decommit any tables that were used
let table_element_size = max_table_element_size();
for (table, base) in instance.tables.values().zip(self.tables.get(index)) {
let size = round_up_to_pow2(
table.size() as usize * table_element_size,
self.tables.page_size,
);
decommit_table_pages(base, size).unwrap();
}
instance.tables.clear();
instance.dropped_elements.borrow_mut().clear();
// Drop any host state
instance.host_state = Box::new(());
self.free_list.lock().unwrap().push(index);
}
fn set_instance_memories(
instance: &mut Instance,
mut memories: BasePointerIterator,
mut memories: impl Iterator<Item = *mut u8>,
max_pages: u32,
) -> Result<(), InstantiationError> {
let module = instance.module.as_ref();
@@ -541,19 +500,24 @@ impl InstancePool {
.reset_guard_pages()
.map_err(|e| InstantiationError::Resource(e.to_string()))?;
instance.memories.clear();
debug_assert!(instance.memories.is_empty());
for plan in
(&module.memory_plans.values().as_slice()[module.num_imported_memories..]).iter()
{
instance.memories.push(
Memory::new_static(plan, memories.next().unwrap(), max_pages, make_accessible)
.map_err(InstantiationError::Resource)?,
Memory::new_static(
plan,
memories.next().unwrap(),
max_pages,
commit_memory_pages,
)
.map_err(|e| InstantiationError::Resource(e.to_string()))?,
);
}
let mut dropped_data = instance.dropped_data.borrow_mut();
dropped_data.clear();
debug_assert!(dropped_data.is_empty());
dropped_data.resize(module.passive_data.len());
Ok(())
@@ -561,22 +525,18 @@ impl InstancePool {
fn set_instance_tables(
instance: &mut Instance,
mut tables: BasePointerIterator,
mut tables: impl Iterator<Item = *mut u8>,
max_elements: u32,
) -> Result<(), InstantiationError> {
let module = instance.module.as_ref();
instance.tables.clear();
debug_assert!(instance.tables.is_empty());
for plan in (&module.table_plans.values().as_slice()[module.num_imported_tables..]).iter() {
let base = tables.next().unwrap();
// Make the table data accessible
if unsafe { !make_accessible(base, max_elements as usize * max_table_element_size()) } {
return Err(InstantiationError::Resource(
"failed to make instance memory accessible".into(),
));
}
commit_table_pages(base, max_elements as usize * max_table_element_size())
.map_err(|e| InstantiationError::Resource(e.to_string()))?;
instance
.tables
@@ -584,7 +544,7 @@ impl InstancePool {
}
let mut dropped_elements = instance.dropped_elements.borrow_mut();
dropped_elements.clear();
debug_assert!(dropped_elements.is_empty());
dropped_elements.resize(module.passive_elements.len());
Ok(())
@@ -623,8 +583,31 @@ struct MemoryPool {
impl MemoryPool {
fn new(module_limits: &ModuleLimits, instance_limits: &InstanceLimits) -> Result<Self> {
let memory_size = usize::try_from(instance_limits.memory_reservation_size)
.map_err(|_| anyhow!("memory reservation size exceeds addressable memory"))?;
// The maximum module memory page count cannot exceed 65536 pages
if module_limits.memory_pages > 0x10000 {
bail!(
"module memory page limit of {} exceeds the maximum of 65536",
module_limits.memory_pages
);
}
// The maximum module memory page count cannot exceed the memory reservation size
if (module_limits.memory_pages * WASM_PAGE_SIZE) as u64
> instance_limits.memory_reservation_size
{
bail!(
"module memory page limit of {} pages exceeds the memory reservation size limit of {} bytes",
module_limits.memory_pages,
instance_limits.memory_reservation_size
);
}
let memory_size = if module_limits.memory_pages > 0 {
usize::try_from(instance_limits.memory_reservation_size)
.map_err(|_| anyhow!("memory reservation size exceeds addressable memory"))?
} else {
0
};
debug_assert!(
memory_size % region::page::size() == 0,
@@ -642,25 +625,36 @@ impl MemoryPool {
anyhow!("total size of memory reservation exceeds addressable memory")
})?;
Ok(Self {
mapping: create_memory_map(0, allocation_size)?,
// Create a completely inaccessible region to start
let mapping = Mmap::accessible_reserved(0, allocation_size)
.context("failed to create memory pool mapping")?;
let pool = Self {
mapping,
memory_size,
max_memories,
max_instances,
max_wasm_pages: module_limits.memory_pages,
})
};
// uffd support requires some special setup for the memory pool
#[cfg(all(feature = "uffd", target_os = "linux"))]
initialize_memory_pool(&pool)?;
Ok(pool)
}
fn get(&self, instance_index: usize) -> BasePointerIterator {
fn get(&self, instance_index: usize) -> impl Iterator<Item = *mut u8> {
debug_assert!(instance_index < self.max_instances);
let base = unsafe {
let base: *mut u8 = unsafe {
self.mapping
.as_mut_ptr()
.add(instance_index * self.memory_size * self.max_memories) as _
};
BasePointerIterator::new(base, self.max_memories, self.memory_size)
let size = self.memory_size;
(0..self.max_memories).map(move |i| unsafe { base.add(i * size) })
}
}
@@ -668,9 +662,6 @@ impl MemoryPool {
///
/// Each instance index into the pool returns an iterator over the base addresses
/// of the instance's tables.
///
/// The userfault handler relies on how tables are stored in the mapping,
/// so make sure the uffd implementation is kept up-to-date.
#[derive(Debug)]
struct TablePool {
mapping: Mmap,
@@ -685,12 +676,16 @@ impl TablePool {
fn new(module_limits: &ModuleLimits, instance_limits: &InstanceLimits) -> Result<Self> {
let page_size = region::page::size();
let table_size = round_up_to_pow2(
max_table_element_size()
.checked_mul(module_limits.table_elements as usize)
.ok_or_else(|| anyhow!("table size exceeds addressable memory"))?,
page_size,
);
let table_size = if module_limits.table_elements > 0 {
round_up_to_pow2(
max_table_element_size()
.checked_mul(module_limits.table_elements as usize)
.ok_or_else(|| anyhow!("table size exceeds addressable memory"))?,
page_size,
)
} else {
0
};
let max_instances = instance_limits.count as usize;
let max_tables = module_limits.tables as usize;
@@ -700,26 +695,30 @@ impl TablePool {
.and_then(|c| c.checked_mul(max_instances))
.ok_or_else(|| anyhow!("total size of instance tables exceeds addressable memory"))?;
let mapping = Mmap::accessible_reserved(allocation_size, allocation_size)
.context("failed to create table pool mapping")?;
Ok(Self {
mapping: create_memory_map(0, allocation_size)?,
mapping,
table_size,
max_tables,
max_instances,
page_size: region::page::size(),
page_size,
max_elements: module_limits.table_elements,
})
}
fn get(&self, instance_index: usize) -> BasePointerIterator {
fn get(&self, instance_index: usize) -> impl Iterator<Item = *mut u8> {
debug_assert!(instance_index < self.max_instances);
let base = unsafe {
let base: *mut u8 = unsafe {
self.mapping
.as_mut_ptr()
.add(instance_index * self.table_size * self.max_tables) as _
};
BasePointerIterator::new(base, self.max_tables, self.table_size)
let size = self.table_size;
(0..self.max_tables).map(move |i| unsafe { base.add(i * size) })
}
}
@@ -733,9 +732,6 @@ impl TablePool {
///
/// The top of the stack (starting stack pointer) is returned when a stack is allocated
/// from the pool.
///
/// The userfault handler relies on how stacks are stored in the mapping,
/// so make sure the uffd implementation is kept up-to-date.
#[derive(Debug)]
struct StackPool {
mapping: Mmap,
@@ -765,15 +761,18 @@ impl StackPool {
.checked_mul(max_instances)
.ok_or_else(|| anyhow!("total size of execution stacks exceeds addressable memory"))?;
let mapping = create_memory_map(allocation_size, allocation_size)?;
let mapping = Mmap::accessible_reserved(allocation_size, allocation_size)
.context("failed to create stack pool mapping")?;
// Set up the stack guard pages
unsafe {
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)
.context("failed to protect stack guard page")?;
if allocation_size > 0 {
unsafe {
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)
.context("failed to protect stack guard page")?;
}
}
}
@@ -804,8 +803,19 @@ impl StackPool {
debug_assert!(index < self.max_instances);
unsafe {
// The top (end) of the stack should be returned
Ok(self.mapping.as_mut_ptr().add((index + 1) * self.stack_size))
// Remove the guard page from the size
let size_without_guard = self.stack_size - self.page_size;
let bottom_of_stack = self
.mapping
.as_mut_ptr()
.add((index * self.stack_size) + self.page_size);
commit_stack_pages(bottom_of_stack, size_without_guard)
.map_err(|e| FiberStackError::Resource(e.to_string()))?;
// The top of the stack should be returned
Ok(bottom_of_stack.add(size_without_guard))
}
}
@@ -826,18 +836,16 @@ impl StackPool {
let index = (start_of_stack - base) / self.stack_size;
debug_assert!(index < self.max_instances);
decommit(bottom_of_stack, stack_size);
decommit_stack_pages(bottom_of_stack, stack_size).unwrap();
{
self.free_list.lock().unwrap().push(index);
}
self.free_list.lock().unwrap().push(index);
}
}
}
/// Implements the pooling instance allocator.
///
/// This allocator interinally maintains pools of instances, memories, tables, and stacks.
/// This allocator internally maintains pools of instances, memories, tables, and stacks.
///
/// Note: the resource pools are manually dropped so that the fault handler terminates correctly.
#[derive(Debug)]
@@ -845,10 +853,11 @@ pub struct PoolingInstanceAllocator {
strategy: PoolingAllocationStrategy,
module_limits: ModuleLimits,
instance_limits: InstanceLimits,
// This is manually drop so that the pools unmap their memory before the page fault handler drops.
instances: mem::ManuallyDrop<InstancePool>,
stacks: mem::ManuallyDrop<StackPool>,
stacks: StackPool,
#[cfg(all(feature = "uffd", target_os = "linux"))]
_fault_handler: PageFaultHandler,
_fault_handler: imp::PageFaultHandler,
}
impl PoolingInstanceAllocator {
@@ -874,37 +883,18 @@ impl PoolingInstanceAllocator {
instance_limits.memory_reservation_size =
min(instance_limits.memory_reservation_size, 0x200000000);
// The maximum module memory page count cannot exceed 65536 pages
if module_limits.memory_pages > 0x10000 {
bail!(
"module memory page limit of {} exceeds the maximum of 65536",
module_limits.memory_pages
);
}
// The maximum module memory page count cannot exceed the memory reservation size
if (module_limits.memory_pages * WASM_PAGE_SIZE) as u64
> instance_limits.memory_reservation_size
{
bail!(
"module memory page limit of {} pages exeeds the memory reservation size limit of {} bytes",
module_limits.memory_pages,
instance_limits.memory_reservation_size
);
}
let instances = InstancePool::new(&module_limits, &instance_limits)?;
let stacks = StackPool::new(&instance_limits, stack_size)?;
#[cfg(all(feature = "uffd", target_os = "linux"))]
let _fault_handler = PageFaultHandler::new(&instances)?;
let _fault_handler = imp::PageFaultHandler::new(&instances)?;
Ok(Self {
strategy,
module_limits,
instance_limits,
instances: mem::ManuallyDrop::new(instances),
stacks: mem::ManuallyDrop::new(stacks),
stacks,
#[cfg(all(feature = "uffd", target_os = "linux"))]
_fault_handler,
})
@@ -917,7 +907,6 @@ impl Drop for PoolingInstanceAllocator {
// This ensures that any fault handler thread monitoring the pool memory terminates
unsafe {
mem::ManuallyDrop::drop(&mut self.instances);
mem::ManuallyDrop::drop(&mut self.stacks);
}
}
}
@@ -963,13 +952,13 @@ unsafe impl InstanceAllocator for PoolingInstanceAllocator {
cfg_if::cfg_if! {
if #[cfg(all(feature = "uffd", target_os = "linux"))] {
match &instance.module.memory_initialization {
MemoryInitialization::Paged{ out_of_bounds, .. } => {
wasmtime_environ::MemoryInitialization::Paged{ out_of_bounds, .. } => {
if !is_bulk_memory {
check_init_bounds(instance)?;
super::check_init_bounds(instance)?;
}
// Initialize the tables
initialize_tables(instance)?;
super::initialize_tables(instance)?;
// Don't initialize the memory; the fault handler will back the pages when accessed
@@ -1312,21 +1301,6 @@ mod test {
assert_eq!(strat.next(1), 0);
}
#[test]
fn test_base_pointer_iterator() {
let mut iter = BasePointerIterator::new(std::ptr::null_mut(), 5, 3);
assert_eq!(iter.next(), Some(0usize as _));
assert_eq!(iter.next(), Some(3usize as _));
assert_eq!(iter.next(), Some(6usize as _));
assert_eq!(iter.next(), Some(9usize as _));
assert_eq!(iter.next(), Some(12usize as _));
assert_eq!(iter.next(), None);
let mut iter = BasePointerIterator::new(std::ptr::null_mut(), 0, 10);
assert_eq!(iter.next(), None);
}
#[cfg(target_pointer_width = "64")]
#[test]
fn test_instance_pool() -> Result<()> {
@@ -1341,11 +1315,11 @@ mod test {
memories: 1,
globals: 0,
table_elements: 10,
memory_pages: 10,
memory_pages: 1,
};
let instance_limits = InstanceLimits {
count: 3,
memory_reservation_size: 4096,
memory_reservation_size: WASM_PAGE_SIZE as u64,
};
let instances = InstancePool::new(&module_limits, &instance_limits)?;
@@ -1366,7 +1340,7 @@ mod test {
assert_eq!(instances.instance_size, 4096);
assert_eq!(instances.max_instances, 3);
assert_eq!(&*instances.free_list.lock().unwrap(), &[0, 1, 2],);
assert_eq!(&*instances.free_list.lock().unwrap(), &[0, 1, 2]);
let mut handles = Vec::new();
let module = Arc::new(Module::default());
@@ -1397,7 +1371,7 @@ mod test {
);
}
assert_eq!(&*instances.free_list.lock().unwrap(), &[],);
assert_eq!(&*instances.free_list.lock().unwrap(), &[]);
match instances.allocate(
PoolingAllocationStrategy::NextAvailable,
@@ -1425,7 +1399,7 @@ mod test {
instances.deallocate(&handle);
}
assert_eq!(&*instances.free_list.lock().unwrap(), &[2, 1, 0],);
assert_eq!(&*instances.free_list.lock().unwrap(), &[2, 1, 0]);
Ok(())
}
@@ -1445,7 +1419,7 @@ mod test {
memories: 3,
globals: 0,
table_elements: 0,
memory_pages: 10,
memory_pages: 1,
},
&InstanceLimits {
count: 5,
@@ -1456,7 +1430,7 @@ mod test {
assert_eq!(pool.memory_size, WASM_PAGE_SIZE as usize);
assert_eq!(pool.max_memories, 3);
assert_eq!(pool.max_instances, 5);
assert_eq!(pool.max_wasm_pages, 10);
assert_eq!(pool.max_wasm_pages, 1);
let base = pool.mapping.as_ptr() as usize;
@@ -1554,7 +1528,7 @@ mod test {
stacks.push(stack);
}
assert_eq!(&*pool.free_list.lock().unwrap(), &[],);
assert_eq!(&*pool.free_list.lock().unwrap(), &[]);
match pool
.allocate(PoolingAllocationStrategy::NextAvailable)
@@ -1632,7 +1606,7 @@ mod test {
)
.map_err(|e| e.to_string())
.expect_err("expected a failure constructing instance allocator"),
"module memory page limit of 2 pages exeeds the memory reservation size limit of 65536 bytes"
"module memory page limit of 2 pages exceeds the memory reservation size limit of 65536 bytes"
);
}

67
crates/runtime/src/instance/allocator/pooling/linux.rs
View File

@@ -1,23 +1,58 @@
use crate::Mmap;
use anyhow::{anyhow, Result};
use anyhow::{bail, Context, Result};
pub unsafe fn make_accessible(addr: *mut u8, len: usize) -> bool {
region::protect(addr, len, region::Protection::READ_WRITE).is_ok()
fn decommit(addr: *mut u8, len: usize, protect: bool) -> Result<()> {
if len == 0 {
return Ok(());
}
unsafe {
if protect {
region::protect(addr, len, region::Protection::NONE)
.context("failed to protect memory pages")?;
}
// On Linux, this is enough to cause the kernel to initialize the pages to 0 on next access
if libc::madvise(addr as _, len, libc::MADV_DONTNEED) != 0 {
bail!(
"madvise failed to decommit: {}",
std::io::Error::last_os_error()
);
}
}
Ok(())
}
pub unsafe fn decommit(addr: *mut u8, len: usize) {
region::protect(addr, len, region::Protection::NONE).unwrap();
pub fn commit_memory_pages(addr: *mut u8, len: usize) -> Result<()> {
if len == 0 {
return Ok(());
}
// On Linux, this is enough to cause the kernel to initialize the pages to 0 on next access
assert_eq!(
libc::madvise(addr as _, len, libc::MADV_DONTNEED),
0,
"madvise failed to mark pages as missing: {}",
std::io::Error::last_os_error()
);
// Just change the protection level to READ|WRITE
unsafe {
region::protect(addr, len, region::Protection::READ_WRITE)
.context("failed to make linear memory pages read/write")
}
}
pub fn create_memory_map(accessible_size: usize, mapping_size: usize) -> Result<Mmap> {
Mmap::accessible_reserved(accessible_size, mapping_size)
.map_err(|e| anyhow!("failed to allocate pool memory: {}", e))
pub fn decommit_memory_pages(addr: *mut u8, len: usize) -> Result<()> {
decommit(addr, len, true)
}
pub fn commit_table_pages(_addr: *mut u8, _len: usize) -> Result<()> {
// A no-op as table pages remain READ|WRITE
Ok(())
}
pub fn decommit_table_pages(addr: *mut u8, len: usize) -> Result<()> {
decommit(addr, len, false)
}
pub fn commit_stack_pages(_addr: *mut u8, _len: usize) -> Result<()> {
// A no-op as stack pages remain READ|WRITE
Ok(())
}
pub fn decommit_stack_pages(addr: *mut u8, len: usize) -> Result<()> {
decommit(addr, len, false)
}

346
crates/runtime/src/instance/allocator/pooling/uffd.rs
View File

@@ -16,11 +16,10 @@
//! 1. A user fault file descriptor is created to monitor specific areas of the address space.
//! 2. A thread is spawned to continually read events from the user fault file descriptor.
//! 3. When a page fault event is received, the handler thread calculates where the fault occurred:
//! a) If the fault occurs on a table page, it is handled by zeroing the page.
//! b) If the fault occurs on a linear memory page, it is handled by either copying the page from
//! a) If the fault occurs on a linear memory page, it is handled by either copying the page from
//! initialization data or zeroing it.
//! c) If the fault occurs on a guard page, the protection level of the guard page is changed to
//! force the kernel to signal SIGSEV on the next retry. The faulting page is recorded so the
//! b) If the fault occurs on a guard page, the protection level of the guard page is changed to
//! force the kernel to signal SIGBUS on the next retry. The faulting page is recorded so the
//! protection level can be reset in the future.
//! 4. Faults to address space relating to an instance may occur from both Wasmtime (e.g. instance
//! initialization) or from WebAssembly code (e.g. reading from or writing to linear memory),
@@ -31,80 +30,103 @@
//!
//! This feature requires a Linux kernel 4.11 or newer to use.
use super::InstancePool;
use crate::{instance::Instance, Mmap};
use super::{InstancePool, MemoryPool};
use crate::instance::Instance;
use anyhow::{bail, Context, Result};
use std::ptr;
use std::thread;
use userfaultfd::{Event, FeatureFlags, IoctlFlags, Uffd, UffdBuilder};
use wasmtime_environ::{entity::EntityRef, wasm::DefinedMemoryIndex, MemoryInitialization};
const WASM_PAGE_SIZE: usize = wasmtime_environ::WASM_PAGE_SIZE as usize;
pub unsafe fn make_accessible(_addr: *mut u8, _len: usize) -> bool {
// A no-op when userfaultfd is used
true
}
pub unsafe fn reset_guard_page(addr: *mut u8, len: usize) -> bool {
// Guard pages are READ_WRITE with uffd until faulted
region::protect(addr, len, region::Protection::READ_WRITE).is_ok()
}
pub unsafe fn decommit(addr: *mut u8, len: usize) {
// Use MADV_DONTNEED to mark the pages as missing
// This will cause a missing page fault for next access on any page in the given range
assert_eq!(
libc::madvise(addr as _, len, libc::MADV_DONTNEED),
0,
"madvise failed to mark pages as missing: {}",
std::io::Error::last_os_error()
);
}
pub fn create_memory_map(_accessible_size: usize, mapping_size: usize) -> Result<Mmap> {
// Allocate a single read-write region at once
// As writable pages need to count towards commit charge, use MAP_NORESERVE to override.
// This implies that the kernel is configured to allow overcommit or else this allocation
// will almost certainly fail without a plethora of physical memory to back the allocation.
// The consequence of not reserving is that our process may segfault on any write to a memory
// page that cannot be backed (i.e. out of memory conditions).
if mapping_size == 0 {
return Ok(Mmap::new());
fn decommit(addr: *mut u8, len: usize) -> Result<()> {
if len == 0 {
return Ok(());
}
unsafe {
let ptr = libc::mmap(
ptr::null_mut(),
mapping_size,
libc::PROT_READ | libc::PROT_WRITE,
libc::MAP_PRIVATE | libc::MAP_ANON | libc::MAP_NORESERVE,
-1,
0,
);
if ptr as isize == -1_isize {
// On Linux, this is enough to cause the kernel to initialize the pages to 0 on next access
if libc::madvise(addr as _, len, libc::MADV_DONTNEED) != 0 {
bail!(
"failed to allocate pool memory: mmap failed with {}",
"madvise failed to decommit: {}",
std::io::Error::last_os_error()
);
}
}
Ok(Mmap::from_raw(ptr as usize, mapping_size))
Ok(())
}
pub fn commit_memory_pages(_addr: *mut u8, _len: usize) -> Result<()> {
// A no-op as memory pages remain READ|WRITE with uffd
Ok(())
}
pub fn decommit_memory_pages(addr: *mut u8, len: usize) -> Result<()> {
decommit(addr, len)
}
pub fn commit_table_pages(_addr: *mut u8, _len: usize) -> Result<()> {
// A no-op as table pages remain READ|WRITE
Ok(())
}
pub fn decommit_table_pages(addr: *mut u8, len: usize) -> Result<()> {
decommit(addr, len)
}
pub fn commit_stack_pages(_addr: *mut u8, _len: usize) -> Result<()> {
// A no-op as stack pages remain READ|WRITE
Ok(())
}
pub fn decommit_stack_pages(addr: *mut u8, len: usize) -> Result<()> {
decommit(addr, len)
}
/// This is used to initialize the memory pool when uffd is enabled.
///
/// Without uffd, all of the memory pool's pages are initially protected with `NONE` to treat the entire
/// range as guard pages. When an instance is created, the initial pages of the memory are
/// changed to `READ_WRITE`.
///
/// With uffd, however, the potentially accessible pages of the each linear memory are made `READ_WRITE` and
/// the page fault handler will detect an out of bounds access and treat the page, temporarily,
/// as a guard page.
///
/// This me
pub(super) fn initialize_memory_pool(pool: &MemoryPool) -> Result<()> {
if pool.memory_size == 0 || pool.max_wasm_pages == 0 {
return Ok(());
}
for i in 0..pool.max_instances {
for base in pool.get(i) {
unsafe {
region::protect(
base as _,
pool.max_wasm_pages as usize * WASM_PAGE_SIZE,
region::Protection::READ_WRITE,
)
.context("failed to initialize memory pool for uffd")?;
}
}
}
Ok(())
}
/// This is used to reset a linear memory's guard page back to read-write as the page might be accessible
/// again in the future depending on how the linear memory grows.
fn reset_guard_page(addr: *mut u8, len: usize) -> Result<()> {
unsafe {
region::protect(addr, len, region::Protection::READ_WRITE)
.context("failed to reset guard page")
}
}
/// Represents a location of a page fault within monitored regions of memory.
enum AddressLocation<'a> {
/// The address location is in a WebAssembly table page.
/// The fault handler will zero the page as tables are initialized at instantiation-time.
TablePage {
/// The address of the page being accessed.
page_addr: *mut u8,
/// The length of the page being accessed.
len: usize,
},
enum FaultLocation<'a> {
/// The address location is in a WebAssembly linear memory page.
/// The fault handler will copy the pages from initialization data if necessary.
MemoryPage {
@@ -121,12 +143,12 @@ enum AddressLocation<'a> {
},
}
/// Used to resolve fault addresses to address locations.
/// Used to resolve fault addresses to a location.
///
/// This implementation relies heavily on how the various resource pools utilize their memory.
/// This implementation relies heavily on how the linear memory pool organizes its memory.
///
/// `usize` is used here instead of pointers to keep this `Send` as it gets sent to the handler thread.
struct AddressLocator {
struct FaultLocator {
instances_start: usize,
instance_size: usize,
max_instances: usize,
@@ -134,19 +156,13 @@ struct AddressLocator {
memories_end: usize,
memory_size: usize,
max_memories: usize,
tables_start: usize,
tables_end: usize,
table_size: usize,
page_size: usize,
}
impl AddressLocator {
impl FaultLocator {
fn new(instances: &InstancePool) -> Self {
let instances_start = instances.mapping.as_ptr() as usize;
let memories_start = instances.memories.mapping.as_ptr() as usize;
let memories_end = memories_start + instances.memories.mapping.len();
let tables_start = instances.tables.mapping.as_ptr() as usize;
let tables_end = tables_start + instances.tables.mapping.len();
// Should always have instances
debug_assert!(instances_start != 0);
@@ -159,10 +175,6 @@ impl AddressLocator {
memories_end,
memory_size: instances.memories.memory_size,
max_memories: instances.memories.max_memories,
tables_start,
tables_end,
table_size: instances.tables.table_size,
page_size: instances.tables.page_size,
}
}
@@ -174,7 +186,7 @@ impl AddressLocator {
///
/// Of course a stray faulting memory access from a thread that does not own
/// the instance might introduce a race, but this implementation considers
/// such to be a serious bug.
/// such to be a serious soundness bug not originating in this code.
///
/// If the assumption holds true, accessing the instance data from the handler thread
/// should, in theory, be safe.
@@ -183,8 +195,8 @@ impl AddressLocator {
&*((self.instances_start + (index * self.instance_size)) as *const Instance)
}
unsafe fn get_location(&self, addr: usize) -> Option<AddressLocation> {
// Check for a memory location
unsafe fn locate(&self, addr: usize) -> Option<FaultLocation> {
// Check for a linear memory location
if addr >= self.memories_start && addr < self.memories_end {
let index = (addr - self.memories_start) / self.memory_size;
let memory_index = DefinedMemoryIndex::new(index % self.max_memories);
@@ -200,7 +212,7 @@ impl AddressLocator {
}
});
return Some(AddressLocation::MemoryPage {
return Some(FaultLocation::MemoryPage {
page_addr: (memory_start + page_index * WASM_PAGE_SIZE) as _,
len: WASM_PAGE_SIZE,
instance,
@@ -209,19 +221,6 @@ impl AddressLocator {
});
}
// Check for a table location
if addr >= self.tables_start && addr < self.tables_end {
let index = (addr - self.tables_start) / self.table_size;
let table_start = self.tables_start + (index * self.table_size);
let table_offset = addr - table_start;
let page_index = table_offset / self.page_size;
return Some(AddressLocation::TablePage {
page_addr: (table_start + (page_index * self.page_size)) as _,
len: self.page_size,
});
}
None
}
}
@@ -231,9 +230,9 @@ impl AddressLocator {
/// Because the region being monitored is protected read-write, this needs to set the
/// protection level to `NONE` before waking the page.
///
/// This will cause the kernel to raise a SIGSEGV when retrying the fault.
/// This will cause the kernel to raise a SIGBUS when retrying the fault.
unsafe fn wake_guard_page_access(uffd: &Uffd, page_addr: *const u8, len: usize) -> Result<()> {
// Set the page to NONE to induce a SIGSEGV for the access on the next retry
// Set the page to NONE to induce a SIGBUS for the access on the next retry
region::protect(page_addr, len, region::Protection::NONE)
.context("failed to change guard page protection")?;
@@ -288,22 +287,11 @@ unsafe fn initialize_wasm_page(
unsafe fn handle_page_fault(
uffd: &Uffd,
locator: &AddressLocator,
locator: &FaultLocator,
addr: *mut std::ffi::c_void,
) -> Result<()> {
match locator.get_location(addr as usize) {
Some(AddressLocation::TablePage { page_addr, len }) => {
log::trace!(
"handling fault in table at address {:p} on page {:p}",
addr,
page_addr,
);
// Tables are always initialized upon instantiation, so zero the page
uffd.zeropage(page_addr as _, len, true)
.context("failed to zero table page")?;
}
Some(AddressLocation::MemoryPage {
match locator.locate(addr as usize) {
Some(FaultLocation::MemoryPage {
page_addr,
len,
instance,
@@ -340,7 +328,7 @@ unsafe fn handle_page_fault(
Ok(())
}
fn handler_thread(uffd: Uffd, locator: AddressLocator, mut registrations: usize) -> Result<()> {
fn fault_handler_thread(uffd: Uffd, locator: FaultLocator) -> Result<()> {
loop {
match uffd.read_event().expect("failed to read event") {
Some(Event::Unmap { start, end }) => {
@@ -348,13 +336,8 @@ fn handler_thread(uffd: Uffd, locator: AddressLocator, mut registrations: usize)
let (start, end) = (start as usize, end as usize);
if (start == locator.memories_start && end == locator.memories_end)
|| (start == locator.tables_start && end == locator.tables_end)
{
registrations -= 1;
if registrations == 0 {
break;
}
if start == locator.memories_start && end == locator.memories_end {
break;
} else {
panic!("unexpected memory region unmapped");
}
@@ -385,53 +368,39 @@ impl PageFaultHandler {
.create()
.context("failed to create user fault descriptor")?;
// Register the ranges with the userfault fd
let mut registrations = 0;
for (start, len) in &[
(
instances.memories.mapping.as_ptr() as usize,
instances.memories.mapping.len(),
),
(
instances.tables.mapping.as_ptr() as usize,
instances.tables.mapping.len(),
),
] {
if *start == 0 || *len == 0 {
continue;
}
// Register the linear memory pool with the userfault fd
let start = instances.memories.mapping.as_ptr();
let len = instances.memories.mapping.len();
let thread = if !start.is_null() && len > 0 {
let ioctls = uffd
.register(*start as _, *len)
.register(start as _, len)
.context("failed to register user fault range")?;
if !ioctls.contains(IoctlFlags::WAKE | IoctlFlags::COPY | IoctlFlags::ZEROPAGE) {
bail!(
"required user fault ioctls not supported; found: {:?}",
"required user fault ioctls not supported by the kernel; found: {:?}",
ioctls,
);
}
registrations += 1;
}
let thread = if registrations == 0 {
log::trace!("user fault handling disabled as there are no regions to monitor");
None
} else {
log::trace!(
"user fault handling enabled on {} memory regions",
registrations
"user fault handling enabled on linear memory pool at {:p} with size {}",
start,
len
);
let locator = AddressLocator::new(&instances);
let locator = FaultLocator::new(&instances);
Some(
thread::Builder::new()
.name("page fault handler".into())
.spawn(move || handler_thread(uffd, locator, registrations))
.spawn(move || fault_handler_thread(uffd, locator))
.context("failed to spawn page fault handler thread")?,
)
} else {
log::trace!("user fault handling disabled as there is no linear memory pool");
None
};
Ok(Self { thread })
@@ -442,7 +411,7 @@ impl Drop for PageFaultHandler {
fn drop(&mut self) {
// The handler thread should terminate once all monitored regions of memory are unmapped.
// The pooling instance allocator ensures that the regions are unmapped prior to dropping
// the user fault handler.
// the page fault handler.
if let Some(thread) = self.thread.take() {
thread
.join()
@@ -456,15 +425,12 @@ impl Drop for PageFaultHandler {
mod test {
use super::*;
use crate::{
table::max_table_element_size, Imports, InstanceAllocationRequest, InstanceLimits,
ModuleLimits, PoolingAllocationStrategy, VMSharedSignatureIndex,
Imports, InstanceAllocationRequest, InstanceLimits, ModuleLimits,
PoolingAllocationStrategy, VMSharedSignatureIndex,
};
use std::ptr;
use std::sync::Arc;
use wasmtime_environ::{
entity::PrimaryMap,
wasm::{Memory, Table, TableElementType, WasmType},
MemoryPlan, MemoryStyle, Module, TablePlan, TableStyle,
};
use wasmtime_environ::{entity::PrimaryMap, wasm::Memory, MemoryPlan, MemoryStyle, Module};
#[cfg(target_pointer_width = "64")]
#[test]
@@ -476,10 +442,10 @@ mod test {
imported_globals: 0,
types: 0,
functions: 0,
tables: 3,
tables: 0,
memories: 2,
globals: 0,
table_elements: 1000,
table_elements: 0,
memory_pages: 2,
};
let instance_limits = InstanceLimits {
@@ -490,7 +456,7 @@ mod test {
let instances =
InstancePool::new(&module_limits, &instance_limits).expect("should allocate");
let locator = AddressLocator::new(&instances);
let locator = FaultLocator::new(&instances);
assert_eq!(locator.instances_start, instances.mapping.as_ptr() as usize);
assert_eq!(locator.instance_size, 4096);
@@ -505,21 +471,10 @@ mod test {
);
assert_eq!(locator.memory_size, WASM_PAGE_SIZE * 10);
assert_eq!(locator.max_memories, 2);
assert_eq!(
locator.tables_start,
instances.tables.mapping.as_ptr() as usize
);
assert_eq!(
locator.tables_end,
locator.tables_start + instances.tables.mapping.len()
);
assert_eq!(locator.table_size, 8192);
unsafe {
assert!(locator.get_location(0).is_none());
assert!(locator
.get_location(std::cmp::max(locator.memories_end, locator.tables_end))
.is_none());
assert!(locator.locate(0).is_none());
assert!(locator.locate(locator.memories_end).is_none());
let mut module = Module::new();
@@ -535,25 +490,13 @@ mod test {
});
}
for _ in 0..module_limits.tables {
module.table_plans.push(TablePlan {
table: Table {
wasm_ty: WasmType::FuncRef,
ty: TableElementType::Func,
minimum: 800,
maximum: Some(900),
},
style: TableStyle::CallerChecksSignature,
});
}
module_limits.validate(&module).expect("should validate");
let mut handles = Vec::new();
let module = Arc::new(module);
let finished_functions = &PrimaryMap::new();
// Allocate the maximum number of instances with the maxmimum number of memories and tables
// Allocate the maximum number of instances with the maximum number of memories
for _ in 0..instances.max_instances {
handles.push(
instances
@@ -570,9 +513,9 @@ mod test {
},
lookup_shared_signature: &|_| VMSharedSignatureIndex::default(),
host_state: Box::new(()),
interrupts: std::ptr::null(),
externref_activations_table: std::ptr::null_mut(),
stack_map_registry: std::ptr::null_mut(),
interrupts: ptr::null(),
externref_activations_table: ptr::null_mut(),
stack_map_registry: ptr::null_mut(),
},
)
.expect("instance should allocate"),
@@ -587,8 +530,8 @@ mod test {
+ (memory_index * locator.memory_size);
// Test for access to first page
match locator.get_location(memory_start + 10000) {
Some(AddressLocation::MemoryPage {
match locator.locate(memory_start + 10000) {
Some(FaultLocation::MemoryPage {
page_addr,
len,
instance: _,
@@ -604,8 +547,8 @@ mod test {
}
// Test for access to second page
match locator.get_location(memory_start + 1024 + WASM_PAGE_SIZE) {
Some(AddressLocation::MemoryPage {
match locator.locate(memory_start + 1024 + WASM_PAGE_SIZE) {
Some(FaultLocation::MemoryPage {
page_addr,
len,
instance: _,
@@ -621,8 +564,8 @@ mod test {
}
// Test for guard page
match locator.get_location(memory_start + 10 + 9 * WASM_PAGE_SIZE) {
Some(AddressLocation::MemoryPage {
match locator.locate(memory_start + 10 + 9 * WASM_PAGE_SIZE) {
Some(FaultLocation::MemoryPage {
page_addr,
len,
instance: _,
@@ -639,33 +582,6 @@ mod test {
}
}
// Validate table locations
for instance_index in 0..instances.max_instances {
for table_index in 0..instances.tables.max_tables {
let table_start = locator.tables_start
+ (instance_index * locator.table_size * instances.tables.max_tables)
+ (table_index * locator.table_size);
// Check for an access of index 107 (first page)
match locator.get_location(table_start + (107 * max_table_element_size())) {
Some(AddressLocation::TablePage { page_addr, len }) => {
assert_eq!(page_addr, table_start as _);
assert_eq!(len, locator.page_size);
}
_ => panic!("expected a table page location"),
}
// Check for an access of index 799 (second page)
match locator.get_location(table_start + (799 * max_table_element_size())) {
Some(AddressLocation::TablePage { page_addr, len }) => {
assert_eq!(page_addr, (table_start + locator.page_size) as _);
assert_eq!(len, locator.page_size);
}
_ => panic!("expected a table page location"),
}
}
}
for handle in handles.drain(..) {
instances.deallocate(&handle);
}

69
crates/runtime/src/instance/allocator/pooling/unix.rs
View File

@@ -1,27 +1,64 @@
use crate::Mmap;
use anyhow::{anyhow, Result};
use anyhow::{bail, Context, Result};
pub unsafe fn make_accessible(addr: *mut u8, len: usize) -> bool {
region::protect(addr, len, region::Protection::READ_WRITE).is_ok()
}
fn decommit(addr: *mut u8, len: usize, protect: bool) -> Result<()> {
if len == 0 {
return Ok(());
}
pub unsafe fn decommit(addr: *mut u8, len: usize) {
assert_eq!(
if unsafe {
libc::mmap(
addr as _,
len,
libc::PROT_NONE,
if protect {
libc::PROT_NONE
} else {
libc::PROT_READ | libc::PROT_WRITE
},
libc::MAP_PRIVATE | libc::MAP_ANON | libc::MAP_FIXED,
-1,
0,
) as *mut u8,
addr,
"mmap failed to remap pages: {}",
std::io::Error::last_os_error()
);
) as *mut u8
} != addr
{
bail!(
"mmap failed to remap pages: {}",
std::io::Error::last_os_error()
);
}
Ok(())
}
pub fn create_memory_map(accessible_size: usize, mapping_size: usize) -> Result<Mmap> {
Mmap::accessible_reserved(accessible_size, mapping_size)
.map_err(|e| anyhow!("failed to allocate pool memory: {}", e))
pub fn commit_memory_pages(addr: *mut u8, len: usize) -> Result<()> {
if len == 0 {
return Ok(());
}
// Just change the protection level to READ|WRITE
unsafe {
region::protect(addr, len, region::Protection::READ_WRITE)
.context("failed to make linear memory pages read/write")
}
}
pub fn decommit_memory_pages(addr: *mut u8, len: usize) -> Result<()> {
decommit(addr, len, true)
}
pub fn commit_table_pages(_addr: *mut u8, _len: usize) -> Result<()> {
// A no-op as table pages remain READ|WRITE
Ok(())
}
pub fn decommit_table_pages(addr: *mut u8, len: usize) -> Result<()> {
decommit(addr, len, false)
}
pub fn commit_stack_pages(_addr: *mut u8, _len: usize) -> Result<()> {
// A no-op as stack pages remain READ|WRITE
Ok(())
}
pub fn decommit_stack_pages(addr: *mut u8, len: usize) -> Result<()> {
decommit(addr, len, false)
}

61
crates/runtime/src/instance/allocator/pooling/windows.rs
View File

@@ -1,22 +1,55 @@
use crate::Mmap;
use anyhow::{anyhow, Result};
use anyhow::{bail, Result};
use winapi::um::memoryapi::{VirtualAlloc, VirtualFree};
use winapi::um::winnt::{MEM_COMMIT, MEM_DECOMMIT, PAGE_READWRITE};
pub unsafe fn make_accessible(addr: *mut u8, len: usize) -> bool {
// This doesn't use the `region` crate because the memory needs to be committed
!VirtualAlloc(addr as _, len, MEM_COMMIT, PAGE_READWRITE).is_null()
pub fn commit(addr: *mut u8, len: usize) -> Result<()> {
if len == 0 {
return Ok(());
}
// Memory needs to be committed, so don't use the `region` crate
if unsafe { VirtualAlloc(addr as _, len, MEM_COMMIT, PAGE_READWRITE).is_null() } {
bail!("failed to commit memory as read/write");
}
Ok(())
}
pub unsafe fn decommit(addr: *mut u8, len: usize) {
assert!(
VirtualFree(addr as _, len, MEM_DECOMMIT) != 0,
"failed to decommit memory pages: {}",
std::io::Error::last_os_error()
);
pub fn decommit(addr: *mut u8, len: usize) -> Result<()> {
if len == 0 {
return Ok(());
}
if unsafe { VirtualFree(addr as _, len, MEM_DECOMMIT) } == 0 {
bail!(
"failed to decommit memory pages: {}",
std::io::Error::last_os_error()
);
}
Ok(())
}
pub fn create_memory_map(accessible_size: usize, mapping_size: usize) -> Result<Mmap> {
Mmap::accessible_reserved(accessible_size, mapping_size)
.map_err(|e| anyhow!("failed to allocate pool memory: {}", e))
pub fn commit_memory_pages(addr: *mut u8, len: usize) -> Result<()> {
commit(addr, len)
}
pub fn decommit_memory_pages(addr: *mut u8, len: usize) -> Result<()> {
decommit(addr, len)
}
pub fn commit_table_pages(addr: *mut u8, len: usize) -> Result<()> {
commit(addr, len)
}
pub fn decommit_table_pages(addr: *mut u8, len: usize) -> Result<()> {
decommit(addr, len)
}
pub fn commit_stack_pages(addr: *mut u8, len: usize) -> Result<()> {
commit(addr, len)
}
pub fn decommit_stack_pages(addr: *mut u8, len: usize) -> Result<()> {
decommit(addr, len)
}

30
crates/runtime/src/memory.rs
View File

@@ -4,6 +4,7 @@
use crate::mmap::Mmap;
use crate::vmcontext::VMMemoryDefinition;
use anyhow::Result;
use more_asserts::{assert_ge, assert_le};
use std::cell::{Cell, RefCell};
use std::cmp::min;
@@ -13,7 +14,7 @@ use wasmtime_environ::{MemoryPlan, MemoryStyle, WASM_MAX_PAGES, WASM_PAGE_SIZE};
/// A memory allocator
pub trait RuntimeMemoryCreator: Send + Sync {
/// Create new RuntimeLinearMemory
fn new_memory(&self, plan: &MemoryPlan) -> Result<Box<dyn RuntimeLinearMemory>, String>;
fn new_memory(&self, plan: &MemoryPlan) -> Result<Box<dyn RuntimeLinearMemory>>;
}
/// A default memory allocator used by Wasmtime
@@ -21,8 +22,8 @@ pub struct DefaultMemoryCreator;
impl RuntimeMemoryCreator for DefaultMemoryCreator {
/// Create new MmapMemory
fn new_memory(&self, plan: &MemoryPlan) -> Result<Box<dyn RuntimeLinearMemory>, String> {
Ok(Box::new(MmapMemory::new(plan)?) as Box<dyn RuntimeLinearMemory>)
fn new_memory(&self, plan: &MemoryPlan) -> Result<Box<dyn RuntimeLinearMemory>> {
Ok(Box::new(MmapMemory::new(plan)?) as _)
}
}
@@ -65,7 +66,7 @@ struct WasmMmap {
impl MmapMemory {
/// Create a new linear memory instance with specified minimum and maximum number of wasm pages.
pub fn new(plan: &MemoryPlan) -> Result<Self, String> {
pub fn new(plan: &MemoryPlan) -> Result<Self> {
// `maximum` cannot be set to more than `65536` pages.
assert_le!(plan.memory.minimum, WASM_MAX_PAGES);
assert!(plan.memory.maximum.is_none() || plan.memory.maximum.unwrap() <= WASM_MAX_PAGES);
@@ -177,7 +178,7 @@ enum MemoryStorage {
base: *mut u8,
size: Cell<u32>,
maximum: u32,
make_accessible: unsafe fn(*mut u8, usize) -> bool,
make_accessible: fn(*mut u8, usize) -> Result<()>,
},
Dynamic(Box<dyn RuntimeLinearMemory>),
}
@@ -189,10 +190,7 @@ pub struct Memory {
impl Memory {
/// Create a new dynamic (movable) memory instance for the specified plan.
pub fn new_dynamic(
plan: &MemoryPlan,
creator: &dyn RuntimeMemoryCreator,
) -> Result<Self, String> {
pub fn new_dynamic(plan: &MemoryPlan, creator: &dyn RuntimeMemoryCreator) -> Result<Self> {
Ok(Self {
storage: MemoryStorage::Dynamic(creator.new_memory(plan)?),
})
@@ -203,14 +201,10 @@ impl Memory {
plan: &MemoryPlan,
base: *mut u8,
maximum: u32,
make_accessible: unsafe fn(*mut u8, usize) -> bool,
) -> Result<Self, String> {
make_accessible: fn(*mut u8, usize) -> Result<()>,
) -> Result<Self> {
if plan.memory.minimum > 0 {
if unsafe {
!make_accessible(base, plan.memory.minimum as usize * WASM_PAGE_SIZE as usize)
} {
return Err("memory cannot be made accessible".into());
}
make_accessible(base, plan.memory.minimum as usize * WASM_PAGE_SIZE as usize)?;
}
Ok(Self {
@@ -258,9 +252,7 @@ impl Memory {
let start = usize::try_from(old_size).unwrap() * WASM_PAGE_SIZE as usize;
let len = usize::try_from(delta).unwrap() * WASM_PAGE_SIZE as usize;
if unsafe { !make_accessible(base.add(start), len) } {
return None;
}
make_accessible(unsafe { base.add(start) }, len).ok()?;
size.set(new_size);

34
crates/runtime/src/mmap.rs
View File

@@ -1,6 +1,7 @@
//! Low-level abstraction for allocating and managing zero-filled pages
//! of memory.
use anyhow::{bail, Result};
use more_asserts::assert_le;
use more_asserts::assert_lt;
use std::io;
@@ -38,7 +39,7 @@ 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, String> {
pub fn with_at_least(size: usize) -> Result<Self> {
let page_size = region::page::size();
let rounded_size = round_up_to_page_size(size, page_size);
Self::accessible_reserved(rounded_size, rounded_size)
@@ -48,10 +49,7 @@ impl Mmap {
/// within a reserved mapping of `mapping_size` bytes. `accessible_size` and `mapping_size`
/// must be native page-size multiples.
#[cfg(not(target_os = "windows"))]
pub fn accessible_reserved(
accessible_size: usize,
mapping_size: usize,
) -> Result<Self, String> {
pub fn accessible_reserved(accessible_size: usize, mapping_size: usize) -> Result<Self> {
let page_size = region::page::size();
assert_le!(accessible_size, mapping_size);
assert_eq!(mapping_size & (page_size - 1), 0);
@@ -76,7 +74,7 @@ impl Mmap {
)
};
if ptr as isize == -1_isize {
return Err(io::Error::last_os_error().to_string());
bail!("mmap failed: {}", io::Error::last_os_error());
}
Self {
@@ -96,7 +94,7 @@ impl Mmap {
)
};
if ptr as isize == -1_isize {
return Err(io::Error::last_os_error().to_string());
bail!("mmap failed: {}", io::Error::last_os_error());
}
let mut result = Self {
@@ -117,10 +115,7 @@ impl Mmap {
/// within a reserved mapping of `mapping_size` bytes. `accessible_size` and `mapping_size`
/// must be native page-size multiples.
#[cfg(target_os = "windows")]
pub fn accessible_reserved(
accessible_size: usize,
mapping_size: usize,
) -> Result<Self, String> {
pub fn accessible_reserved(accessible_size: usize, mapping_size: usize) -> Result<Self> {
use winapi::um::memoryapi::VirtualAlloc;
use winapi::um::winnt::{MEM_COMMIT, MEM_RESERVE, PAGE_NOACCESS, PAGE_READWRITE};
@@ -144,7 +139,7 @@ impl Mmap {
)
};
if ptr.is_null() {
return Err(io::Error::last_os_error().to_string());
bail!("VirtualAlloc failed: {}", io::Error::last_os_error());
}
Self {
@@ -156,7 +151,7 @@ impl Mmap {
let ptr =
unsafe { VirtualAlloc(ptr::null_mut(), mapping_size, MEM_RESERVE, PAGE_NOACCESS) };
if ptr.is_null() {
return Err(io::Error::last_os_error().to_string());
bail!("VirtualAlloc failed: {}", io::Error::last_os_error());
}
let mut result = Self {
@@ -177,7 +172,7 @@ impl Mmap {
/// `start` and `len` must be native page-size multiples and describe a range within
/// `self`'s reserved memory.
#[cfg(not(target_os = "windows"))]
pub fn make_accessible(&mut self, start: usize, len: usize) -> Result<(), String> {
pub fn make_accessible(&mut self, start: usize, len: usize) -> Result<()> {
let page_size = region::page::size();
assert_eq!(start & (page_size - 1), 0);
assert_eq!(len & (page_size - 1), 0);
@@ -186,15 +181,18 @@ impl Mmap {
// Commit the accessible size.
let ptr = self.ptr as *const u8;
unsafe { region::protect(ptr.add(start), len, region::Protection::READ_WRITE) }
.map_err(|e| e.to_string())
unsafe {
region::protect(ptr.add(start), len, region::Protection::READ_WRITE)?;
}
Ok(())
}
/// Make the memory starting at `start` and extending for `len` bytes accessible.
/// `start` and `len` must be native page-size multiples and describe a range within
/// `self`'s reserved memory.
#[cfg(target_os = "windows")]
pub fn make_accessible(&mut self, start: usize, len: usize) -> Result<(), String> {
pub fn make_accessible(&mut self, start: usize, len: usize) -> Result<()> {
use winapi::ctypes::c_void;
use winapi::um::memoryapi::VirtualAlloc;
use winapi::um::winnt::{MEM_COMMIT, PAGE_READWRITE};
@@ -216,7 +214,7 @@ impl Mmap {
}
.is_null()
{
return Err(io::Error::last_os_error().to_string());
bail!("VirtualAlloc failed: {}", io::Error::last_os_error());
}
Ok(())