Remove "unaligned" memory from fuzzing #11147
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This commit removes the configuration knob used during fuzzing to use a custom host memory which is always unaligned on the host. The original intention for this was to help catch issues related to alignment in the x64 backend about, for example, performing unaligned SSE loads correctly (as opposed to accidentally faulting on unaligned addresses). As shown in the test failures of bytecodealliance#11142, however, this is technically UB for other parts of Wasmtime that assume the heap addresses are always aligned. For example Wasmtime will create safe references in to a GC heap and GC heaps are also allocated with this same allocator, meaning that Rust-safe references are unaligned (which is UB). In practice I'm not aware of any actual issues this configuration option has ever discovered, and we've otherwise discovered alignment issues via normal fuzzing as well. Given that I think it's best to just jettison this entirely and stop trying to support it and/or tweak configuration to only use it when supported or similar.
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This commit removes the configuration knob used during fuzzing to use a custom host memory which is always unaligned on the host. The original intention for this was to help catch issues related to alignment in the x64 backend about, for example, performing unaligned SSE loads correctly (as opposed to accidentally faulting on unaligned addresses).
As shown in the test failures of #11142, however, this is technically UB for other parts of Wasmtime that assume the heap addresses are always aligned. For example Wasmtime will create safe references in to a GC heap and GC heaps are also allocated with this same allocator, meaning that Rust-safe references are unaligned (which is UB).
In practice I'm not aware of any actual issues this configuration option has ever discovered, and we've otherwise discovered alignment issues via normal fuzzing as well. Given that I think it's best to just jettison this entirely and stop trying to support it and/or tweak configuration to only use it when supported or similar.