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Implement interrupting wasm code, reimplement stack overflow (#1490) * Implement interrupting wasm code, reimplement stack overflow This commit is a relatively large change for wasmtime with two main goals: * Primarily this enables interrupting executing wasm code with a trap, preventing infinite loops in wasm code. Note that resumption of the wasm code is not a goal of this commit. * Additionally this commit reimplements how we handle stack overflow to ensure that host functions always have a reasonable amount of stack to run on. This fixes an issue where we might longjmp out of a host function, skipping destructors. Lots of various odds and ends end up falling out in this commit once the two goals above were implemented. The strategy for implementing this was also lifted from Spidermonkey and existing functionality inside of Cranelift. I've tried to write up thorough documentation of how this all works in `crates/environ/src/cranelift.rs` where gnarly-ish bits are. A brief summary of how this works is that each function and each loop header now checks to see if they're interrupted. Interrupts and the stack overflow check are actually folded into one now, where function headers check to see if they've run out of stack and the sentinel value used to indicate an interrupt, checked in loop headers, tricks functions into thinking they're out of stack. An interrupt is basically just writing a value to a location which is read by JIT code. When interrupts are delivered and what triggers them has been left up to embedders of the `wasmtime` crate. The `wasmtime::Store` type has a method to acquire an `InterruptHandle`, where `InterruptHandle` is a `Send` and `Sync` type which can travel to other threads (or perhaps even a signal handler) to get notified from. It's intended that this provides a good degree of flexibility when interrupting wasm code. Note though that this does have a large caveat where interrupts don't work when you're interrupting host code, so if you've got a host import blocking for a long time an interrupt won't actually be received until the wasm starts running again. Some fallout included from this change is: * Unix signal handlers are no longer registered with `SA_ONSTACK`. Instead they run on the native stack the thread was already using. This is possible since stack overflow isn't handled by hitting the guard page, but rather it's explicitly checked for in wasm now. Native stack overflow will continue to abort the process as usual. * Unix sigaltstack management is now no longer necessary since we don't use it any more. * Windows no longer has any need to reset guard pages since we no longer try to recover from faults on guard pages. * On all targets probestack intrinsics are disabled since we use a different mechanism for catching stack overflow. * The C API has been updated with interrupts handles. An example has also been added which shows off how to interrupt a module. Closes #139 Closes #860 Closes #900 * Update comment about magical interrupt value * Store stack limit as a global value, not a closure * Run rustfmt * Handle review comments * Add a comment about SA_ONSTACK * Use `usize` for type of `INTERRUPTED` * Parse human-readable durations * Bring back sigaltstack handling Allows libstd to print out stack overflow on failure still. * Add parsing and emission of stack limit-via-preamble * Fix new example for new apis * Fix host segfault test in release mode * Fix new doc example
5 years ago
//! Small example of how you can interrupt the execution of a wasm module to
//! ensure that it doesn't run for too long.
// You can execute this example with `cargo run --example interrupt`
use anyhow::Result;
use wasmtime::*;
fn main() -> Result<()> {
// Enable interruptable code via `Config` and then create an interrupt
// handle which we'll use later to interrupt running code.
Implement shared host functions. (#2625) * Implement defining host functions at the Config level. This commit introduces defining host functions at the `Config` rather than with `Func` tied to a `Store`. The intention here is to enable a host to define all of the functions once with a `Config` and then use a `Linker` (or directly with `Store::get_host_func`) to use the functions when instantiating a module. This should help improve the performance of use cases where a `Store` is short-lived and redefining the functions at every module instantiation is a noticeable performance hit. This commit adds `add_to_config` to the code generation for Wasmtime&#39;s `Wasi` type. The new method adds the WASI functions to the given config as host functions. This commit adds context functions to `Store`: `get` to get a context of a particular type and `set` to set the context on the store. For safety, `set` cannot replace an existing context value of the same type. `Wasi::set_context` was added to set the WASI context for a `Store` when using `Wasi::add_to_config`. * Add `Config::define_host_func_async`. * Make config &#34;async&#34; rather than store. This commit moves the concept of &#34;async-ness&#34; to `Config` rather than `Store`. Note: this is a breaking API change for anyone that&#39;s already adopted the new async support in Wasmtime. Now `Config::new_async` is used to create an &#34;async&#34; config and any `Store` associated with that config is inherently &#34;async&#34;. This is needed for async shared host functions to have some sanity check during their execution (async host functions, like &#34;async&#34; `Func`, need to be called with the &#34;async&#34; variants). * Update async function tests to smoke async shared host functions. This commit updates the async function tests to also smoke the shared host functions, plus `Func::wrap0_async`. This also changes the &#34;wrap async&#34; method names on `Config` to `wrap$N_host_func_async` to slightly better match what is on `Func`. * Move the instance allocator into `Engine`. This commit moves the instantiated instance allocator from `Config` into `Engine`. This makes certain settings in `Config` no longer order-dependent, which is how `Config` should ideally be. This also removes the confusing concept of the &#34;default&#34; instance allocator, instead opting to construct the on-demand instance allocator when needed. This does alter the semantics of the instance allocator as now each `Engine` gets its own instance allocator rather than sharing a single one between all engines created from a configuration. * Make `Engine::new` return `Result`. This is a breaking API change for anyone using `Engine::new`. As creating the pooling instance allocator may fail (likely cause is not enough memory for the provided limits), instead of panicking when creating an `Engine`, `Engine::new` now returns a `Result`. * Remove `Config::new_async`. This commit removes `Config::new_async` in favor of treating &#34;async support&#34; as any other setting on `Config`. The setting is `Config::async_support`. * Remove order dependency when defining async host functions in `Config`. This commit removes the order dependency where async support must be enabled on the `Config` prior to defining async host functions. The check is now delayed to when an `Engine` is created from the config. * Update WASI example to use shared `Wasi::add_to_config`. This commit updates the WASI example to use `Wasi::add_to_config`. As only a single store and instance are used in the example, it has no semantic difference from the previous example, but the intention is to steer users towards defining WASI on the config and only using `Wasi::add_to_linker` when more explicit scoping of the WASI context is required.
4 years ago
let engine = Engine::new(Config::new().interruptable(true))?;
let mut store = Store::new(&engine, ());
Implement interrupting wasm code, reimplement stack overflow (#1490) * Implement interrupting wasm code, reimplement stack overflow This commit is a relatively large change for wasmtime with two main goals: * Primarily this enables interrupting executing wasm code with a trap, preventing infinite loops in wasm code. Note that resumption of the wasm code is not a goal of this commit. * Additionally this commit reimplements how we handle stack overflow to ensure that host functions always have a reasonable amount of stack to run on. This fixes an issue where we might longjmp out of a host function, skipping destructors. Lots of various odds and ends end up falling out in this commit once the two goals above were implemented. The strategy for implementing this was also lifted from Spidermonkey and existing functionality inside of Cranelift. I&#39;ve tried to write up thorough documentation of how this all works in `crates/environ/src/cranelift.rs` where gnarly-ish bits are. A brief summary of how this works is that each function and each loop header now checks to see if they&#39;re interrupted. Interrupts and the stack overflow check are actually folded into one now, where function headers check to see if they&#39;ve run out of stack and the sentinel value used to indicate an interrupt, checked in loop headers, tricks functions into thinking they&#39;re out of stack. An interrupt is basically just writing a value to a location which is read by JIT code. When interrupts are delivered and what triggers them has been left up to embedders of the `wasmtime` crate. The `wasmtime::Store` type has a method to acquire an `InterruptHandle`, where `InterruptHandle` is a `Send` and `Sync` type which can travel to other threads (or perhaps even a signal handler) to get notified from. It&#39;s intended that this provides a good degree of flexibility when interrupting wasm code. Note though that this does have a large caveat where interrupts don&#39;t work when you&#39;re interrupting host code, so if you&#39;ve got a host import blocking for a long time an interrupt won&#39;t actually be received until the wasm starts running again. Some fallout included from this change is: * Unix signal handlers are no longer registered with `SA_ONSTACK`. Instead they run on the native stack the thread was already using. This is possible since stack overflow isn&#39;t handled by hitting the guard page, but rather it&#39;s explicitly checked for in wasm now. Native stack overflow will continue to abort the process as usual. * Unix sigaltstack management is now no longer necessary since we don&#39;t use it any more. * Windows no longer has any need to reset guard pages since we no longer try to recover from faults on guard pages. * On all targets probestack intrinsics are disabled since we use a different mechanism for catching stack overflow. * The C API has been updated with interrupts handles. An example has also been added which shows off how to interrupt a module. Closes #139 Closes #860 Closes #900 * Update comment about magical interrupt value * Store stack limit as a global value, not a closure * Run rustfmt * Handle review comments * Add a comment about SA_ONSTACK * Use `usize` for type of `INTERRUPTED` * Parse human-readable durations * Bring back sigaltstack handling Allows libstd to print out stack overflow on failure still. * Add parsing and emission of stack limit-via-preamble * Fix new example for new apis * Fix host segfault test in release mode * Fix new doc example
5 years ago
let interrupt_handle = store.interrupt_handle()?;
// Compile and instantiate a small example with an infinite loop.
let module = Module::from_file(&engine, "examples/interrupt.wat")?;
let instance = Instance::new(&mut store, &module, &[])?;
let run = instance.get_typed_func::<(), (), _>(&mut store, "run")?;
Implement interrupting wasm code, reimplement stack overflow (#1490) * Implement interrupting wasm code, reimplement stack overflow This commit is a relatively large change for wasmtime with two main goals: * Primarily this enables interrupting executing wasm code with a trap, preventing infinite loops in wasm code. Note that resumption of the wasm code is not a goal of this commit. * Additionally this commit reimplements how we handle stack overflow to ensure that host functions always have a reasonable amount of stack to run on. This fixes an issue where we might longjmp out of a host function, skipping destructors. Lots of various odds and ends end up falling out in this commit once the two goals above were implemented. The strategy for implementing this was also lifted from Spidermonkey and existing functionality inside of Cranelift. I&#39;ve tried to write up thorough documentation of how this all works in `crates/environ/src/cranelift.rs` where gnarly-ish bits are. A brief summary of how this works is that each function and each loop header now checks to see if they&#39;re interrupted. Interrupts and the stack overflow check are actually folded into one now, where function headers check to see if they&#39;ve run out of stack and the sentinel value used to indicate an interrupt, checked in loop headers, tricks functions into thinking they&#39;re out of stack. An interrupt is basically just writing a value to a location which is read by JIT code. When interrupts are delivered and what triggers them has been left up to embedders of the `wasmtime` crate. The `wasmtime::Store` type has a method to acquire an `InterruptHandle`, where `InterruptHandle` is a `Send` and `Sync` type which can travel to other threads (or perhaps even a signal handler) to get notified from. It&#39;s intended that this provides a good degree of flexibility when interrupting wasm code. Note though that this does have a large caveat where interrupts don&#39;t work when you&#39;re interrupting host code, so if you&#39;ve got a host import blocking for a long time an interrupt won&#39;t actually be received until the wasm starts running again. Some fallout included from this change is: * Unix signal handlers are no longer registered with `SA_ONSTACK`. Instead they run on the native stack the thread was already using. This is possible since stack overflow isn&#39;t handled by hitting the guard page, but rather it&#39;s explicitly checked for in wasm now. Native stack overflow will continue to abort the process as usual. * Unix sigaltstack management is now no longer necessary since we don&#39;t use it any more. * Windows no longer has any need to reset guard pages since we no longer try to recover from faults on guard pages. * On all targets probestack intrinsics are disabled since we use a different mechanism for catching stack overflow. * The C API has been updated with interrupts handles. An example has also been added which shows off how to interrupt a module. Closes #139 Closes #860 Closes #900 * Update comment about magical interrupt value * Store stack limit as a global value, not a closure * Run rustfmt * Handle review comments * Add a comment about SA_ONSTACK * Use `usize` for type of `INTERRUPTED` * Parse human-readable durations * Bring back sigaltstack handling Allows libstd to print out stack overflow on failure still. * Add parsing and emission of stack limit-via-preamble * Fix new example for new apis * Fix host segfault test in release mode * Fix new doc example
5 years ago
// Spin up a thread to send us an interrupt in a second
std::thread::spawn(move || {
std::thread::sleep(std::time::Duration::from_secs(1));
println!("Interrupting!");
interrupt_handle.interrupt();
});
println!("Entering infinite loop ...");
let trap = run.call(&mut store, ()).unwrap_err();
Implement interrupting wasm code, reimplement stack overflow (#1490) * Implement interrupting wasm code, reimplement stack overflow This commit is a relatively large change for wasmtime with two main goals: * Primarily this enables interrupting executing wasm code with a trap, preventing infinite loops in wasm code. Note that resumption of the wasm code is not a goal of this commit. * Additionally this commit reimplements how we handle stack overflow to ensure that host functions always have a reasonable amount of stack to run on. This fixes an issue where we might longjmp out of a host function, skipping destructors. Lots of various odds and ends end up falling out in this commit once the two goals above were implemented. The strategy for implementing this was also lifted from Spidermonkey and existing functionality inside of Cranelift. I&#39;ve tried to write up thorough documentation of how this all works in `crates/environ/src/cranelift.rs` where gnarly-ish bits are. A brief summary of how this works is that each function and each loop header now checks to see if they&#39;re interrupted. Interrupts and the stack overflow check are actually folded into one now, where function headers check to see if they&#39;ve run out of stack and the sentinel value used to indicate an interrupt, checked in loop headers, tricks functions into thinking they&#39;re out of stack. An interrupt is basically just writing a value to a location which is read by JIT code. When interrupts are delivered and what triggers them has been left up to embedders of the `wasmtime` crate. The `wasmtime::Store` type has a method to acquire an `InterruptHandle`, where `InterruptHandle` is a `Send` and `Sync` type which can travel to other threads (or perhaps even a signal handler) to get notified from. It&#39;s intended that this provides a good degree of flexibility when interrupting wasm code. Note though that this does have a large caveat where interrupts don&#39;t work when you&#39;re interrupting host code, so if you&#39;ve got a host import blocking for a long time an interrupt won&#39;t actually be received until the wasm starts running again. Some fallout included from this change is: * Unix signal handlers are no longer registered with `SA_ONSTACK`. Instead they run on the native stack the thread was already using. This is possible since stack overflow isn&#39;t handled by hitting the guard page, but rather it&#39;s explicitly checked for in wasm now. Native stack overflow will continue to abort the process as usual. * Unix sigaltstack management is now no longer necessary since we don&#39;t use it any more. * Windows no longer has any need to reset guard pages since we no longer try to recover from faults on guard pages. * On all targets probestack intrinsics are disabled since we use a different mechanism for catching stack overflow. * The C API has been updated with interrupts handles. An example has also been added which shows off how to interrupt a module. Closes #139 Closes #860 Closes #900 * Update comment about magical interrupt value * Store stack limit as a global value, not a closure * Run rustfmt * Handle review comments * Add a comment about SA_ONSTACK * Use `usize` for type of `INTERRUPTED` * Parse human-readable durations * Bring back sigaltstack handling Allows libstd to print out stack overflow on failure still. * Add parsing and emission of stack limit-via-preamble * Fix new example for new apis * Fix host segfault test in release mode * Fix new doc example
5 years ago
println!("trap received...");
assert!(trap.to_string().contains("wasm trap: interrupt"));
Implement interrupting wasm code, reimplement stack overflow (#1490) * Implement interrupting wasm code, reimplement stack overflow This commit is a relatively large change for wasmtime with two main goals: * Primarily this enables interrupting executing wasm code with a trap, preventing infinite loops in wasm code. Note that resumption of the wasm code is not a goal of this commit. * Additionally this commit reimplements how we handle stack overflow to ensure that host functions always have a reasonable amount of stack to run on. This fixes an issue where we might longjmp out of a host function, skipping destructors. Lots of various odds and ends end up falling out in this commit once the two goals above were implemented. The strategy for implementing this was also lifted from Spidermonkey and existing functionality inside of Cranelift. I&#39;ve tried to write up thorough documentation of how this all works in `crates/environ/src/cranelift.rs` where gnarly-ish bits are. A brief summary of how this works is that each function and each loop header now checks to see if they&#39;re interrupted. Interrupts and the stack overflow check are actually folded into one now, where function headers check to see if they&#39;ve run out of stack and the sentinel value used to indicate an interrupt, checked in loop headers, tricks functions into thinking they&#39;re out of stack. An interrupt is basically just writing a value to a location which is read by JIT code. When interrupts are delivered and what triggers them has been left up to embedders of the `wasmtime` crate. The `wasmtime::Store` type has a method to acquire an `InterruptHandle`, where `InterruptHandle` is a `Send` and `Sync` type which can travel to other threads (or perhaps even a signal handler) to get notified from. It&#39;s intended that this provides a good degree of flexibility when interrupting wasm code. Note though that this does have a large caveat where interrupts don&#39;t work when you&#39;re interrupting host code, so if you&#39;ve got a host import blocking for a long time an interrupt won&#39;t actually be received until the wasm starts running again. Some fallout included from this change is: * Unix signal handlers are no longer registered with `SA_ONSTACK`. Instead they run on the native stack the thread was already using. This is possible since stack overflow isn&#39;t handled by hitting the guard page, but rather it&#39;s explicitly checked for in wasm now. Native stack overflow will continue to abort the process as usual. * Unix sigaltstack management is now no longer necessary since we don&#39;t use it any more. * Windows no longer has any need to reset guard pages since we no longer try to recover from faults on guard pages. * On all targets probestack intrinsics are disabled since we use a different mechanism for catching stack overflow. * The C API has been updated with interrupts handles. An example has also been added which shows off how to interrupt a module. Closes #139 Closes #860 Closes #900 * Update comment about magical interrupt value * Store stack limit as a global value, not a closure * Run rustfmt * Handle review comments * Add a comment about SA_ONSTACK * Use `usize` for type of `INTERRUPTED` * Parse human-readable durations * Bring back sigaltstack handling Allows libstd to print out stack overflow on failure still. * Add parsing and emission of stack limit-via-preamble * Fix new example for new apis * Fix host segfault test in release mode * Fix new doc example
5 years ago
Ok(())
}