0e41861662
* Consume fuel during function execution This commit adds codegen infrastructure necessary to instrument wasm code to consume fuel as it executes. Currently nothing is really done with the fuel, but that'll come in later commits. The focus of this commit is to implement the codegen infrastructure necessary to consume fuel and account for fuel consumed correctly. * Periodically check remaining fuel in wasm JIT code This commit enables wasm code to periodically check to see if fuel has run out. When fuel runs out an intrinsic is called which can do what it needs to do in the result of fuel running out. For now a trap is thrown to have at least some semantics in synchronous stores, but another planned use for this feature is for asynchronous stores to periodically yield back to the host based on fuel running out. Checks for remaining fuel happen in the same locations as interrupt checks, which is to say the start of the function as well as loop headers. * Improve codegen by caching `*const VMInterrupts` The location of the shared interrupt value and fuel value is through a double-indirection on the vmctx (load through the vmctx and then load through that pointer). The second pointer in this chain, however, never changes, so we can alter codegen to account for this and remove some extraneous load instructions and hopefully reduce some register pressure even maybe. * Add tests fuel can abort infinite loops * More fuzzing with fuel Use fuel to time out modules in addition to time, using fuzz input to figure out which. * Update docs on trapping instructions * Fix doc links * Fix a fuzz test * Change setting fuel to adding fuel * Fix a doc link * Squelch some rustdoc warnings
68 lines
2.6 KiB
Rust
68 lines
2.6 KiB
Rust
/// Tunable parameters for WebAssembly compilation.
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#[derive(Clone, Hash)]
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pub struct Tunables {
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/// For static heaps, the size in wasm pages of the heap protected by bounds checking.
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pub static_memory_bound: u32,
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/// The size in bytes of the offset guard for static heaps.
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pub static_memory_offset_guard_size: u64,
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/// The size in bytes of the offset guard for dynamic heaps.
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pub dynamic_memory_offset_guard_size: u64,
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/// Whether or not to generate native DWARF debug information.
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pub generate_native_debuginfo: bool,
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/// Whether or not to retain DWARF sections in compiled modules.
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pub parse_wasm_debuginfo: bool,
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/// Whether or not to enable the ability to interrupt wasm code dynamically.
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///
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/// More info can be found about the implementation in
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/// crates/environ/src/cranelift.rs. Note that you can't interrupt host
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/// calls and interrupts are implemented through the `VMInterrupts`
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/// structure, or `InterruptHandle` in the `wasmtime` crate.
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pub interruptable: bool,
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/// Whether or not fuel is enabled for generated code, meaning that fuel
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/// will be consumed every time a wasm instruction is executed.
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pub consume_fuel: bool,
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}
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impl Default for Tunables {
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fn default() -> Self {
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Self {
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#[cfg(target_pointer_width = "32")]
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/// Size in wasm pages of the bound for static memories.
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static_memory_bound: 0x4000,
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#[cfg(target_pointer_width = "64")]
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/// Size in wasm pages of the bound for static memories.
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///
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/// When we allocate 4 GiB of address space, we can avoid the
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/// need for explicit bounds checks.
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static_memory_bound: 0x1_0000,
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#[cfg(target_pointer_width = "32")]
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/// Size in bytes of the offset guard for static memories.
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static_memory_offset_guard_size: 0x1_0000,
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#[cfg(target_pointer_width = "64")]
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/// Size in bytes of the offset guard for static memories.
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///
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/// Allocating 2 GiB of address space lets us translate wasm
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/// offsets into x86 offsets as aggressively as we can.
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static_memory_offset_guard_size: 0x8000_0000,
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/// Size in bytes of the offset guard for dynamic memories.
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///
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/// Allocate a small guard to optimize common cases but without
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/// wasting too much memory.
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dynamic_memory_offset_guard_size: 0x1_0000,
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generate_native_debuginfo: false,
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parse_wasm_debuginfo: true,
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interruptable: false,
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consume_fuel: false,
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}
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}
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}
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