cranelift

rust jit wasm webassembly runtime wasi cranelift sandbox wasmtime

Alex Crichton 7ce46043dc Add guard pages to the front of linear memories (#2977 ) * Add guard pages to the front of linear memories This commit implements a safety feature for Wasmtime to place guard pages before the allocation of all linear memories. Guard pages placed after linear memories are typically present for performance (at least) because it can help elide bounds checks. Guard pages before a linear memory, however, are never strictly needed for performance or features. The intention of a preceding guard page is to help insulate against bugs in Cranelift or other code generators, such as CVE-2021-32629. This commit adds a `Config::guard_before_linear_memory` configuration option, defaulting to `true`, which indicates whether guard pages should be present both before linear memories as well as afterwards. Guard regions continue to be controlled by `{static,dynamic}_memory_guard_size` methods. The implementation here affects both on-demand allocated memories as well as the pooling allocator for memories. For on-demand memories this adjusts the size of the allocation as well as adjusts the calculations for the base pointer of the wasm memory. For the pooling allocator this will place a singular extra guard region at the very start of the allocation for memories. Since linear memories in the pooling allocator are contiguous every memory already had a preceding guard region in memory, it was just the previous memory's guard region afterwards. Only the first memory needed this extra guard. I've attempted to write some tests to help test all this, but this is all somewhat tricky to test because the settings are pretty far away from the actual behavior. I think, though, that the tests added here should help cover various use cases and help us have confidence in tweaking the various `Config` settings beyond their defaults. Note that this also contains a semantic change where `InstanceLimits::memory_reservation_size` has been removed. Instead this field is now inferred from the `static_memory_maximum_size` and guard size settings. This should hopefully remove some duplication in these settings, canonicalizing on the guard-size/static-size settings as the way to control memory sizes and virtual reservations. * Update config docs * Fix a typo * Fix benchmark * Fix wasmtime-runtime tests * Fix some more tests * Try to fix uffd failing test * Review items * Tweak 32-bit defaults Makes the pooling allocator a bit more reasonable by default on 32-bit with these settings.		3 years ago
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instantiation	Implement simple benchmarks for instantiation.	4 years ago
.gitignore	Implement simple benchmarks for instantiation.	4 years ago
instantiation.rs	Implement RFC 11: Redesigning Wasmtime's APIs (#2897)	3 years ago
thread_eager_init.rs	Add guard pages to the front of linear memories (#2977)	3 years ago