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[package]
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name = "wasmtime-fuzz"
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version = "0.0.0"
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edition.workspace = true
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publish = false
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[package.metadata]
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cargo-fuzz = true
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[dependencies]
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anyhow = { workspace = true }
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once_cell = { workspace = true }
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cranelift-codegen = { workspace = true, features = ["incremental-cache"] }
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cranelift-reader = { workspace = true }
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cranelift-wasm = { workspace = true }
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cranelift-filetests = { workspace = true }
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cranelift-interpreter = { workspace = true }
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cranelift-fuzzgen = { workspace = true }
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libfuzzer-sys = { version = "0.4.0", features = ["arbitrary-derive"] }
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target-lexicon = { workspace = true }
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smallvec = { workspace = true }
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wasmtime = { workspace = true }
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wasmtime-fuzzing = { workspace = true }
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component-test-util = { workspace = true }
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component-fuzz-util = { workspace = true }
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[build-dependencies]
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anyhow = { workspace = true }
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proc-macro2 = "1.0"
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arbitrary = { version = "1.1.0", features = ["derive"] }
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rand = { version = "0.8.0" }
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quote = "1.0"
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component-fuzz-util = { workspace = true }
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[features]
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default = ['fuzz-spec-interpreter']
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fuzz-spec-interpreter = ['wasmtime-fuzzing/fuzz-spec-interpreter']
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[[bin]]
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name = "compile"
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path = "fuzz_targets/compile.rs"
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test = false
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doc = false
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[[bin]]
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name = "instantiate"
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path = "fuzz_targets/instantiate.rs"
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test = false
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doc = false
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[[bin]]
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name = "api_calls"
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path = "fuzz_targets/api_calls.rs"
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test = false
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doc = false
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[[bin]]
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name = "differential"
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path = "fuzz_targets/differential.rs"
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test = false
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doc = false
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[[bin]]
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name = "spectests"
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path = "fuzz_targets/spectests.rs"
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test = false
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doc = false
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[[bin]]
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name = "table_ops"
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path = "fuzz_targets/table_ops.rs"
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test = false
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doc = false
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`wasmtime`: Implement fast Wasm stack walking (#4431)
* Always preserve frame pointers in Wasmtime
This allows us to efficiently and simply capture Wasm stacks without maintaining
and synchronizing any safety-critical side tables between the compiler and the
runtime.
* wasmtime: Implement fast Wasm stack walking
Why do we want Wasm stack walking to be fast? Because we capture stacks whenever
there is a trap and traps actually happen fairly frequently with short-lived
programs and WASI's `exit`.
Previously, we would rely on generating the system unwind info (e.g.
`.eh_frame`) and using the system unwinder (via the `backtrace`crate) to walk
the full stack and filter out any non-Wasm stack frames. This can,
unfortunately, be slow for two primary reasons:
1. The system unwinder is doing `O(all-kinds-of-frames)` work rather than
`O(wasm-frames)` work.
2. System unwind info and the system unwinder need to be much more general than
a purpose-built stack walker for Wasm needs to be. It has to handle any kind of
stack frame that any compiler might emit where as our Wasm frames are emitted by
Cranelift and always have frame pointers. This translates into implementation
complexity and general overhead. There can also be unnecessary-for-our-use-cases
global synchronization and locks involved, further slowing down stack walking in
the presence of multiple threads trying to capture stacks in parallel.
This commit introduces a purpose-built stack walker for traversing just our Wasm
frames. To find all the sequences of Wasm-to-Wasm stack frames, and ignore
non-Wasm stack frames, we keep a linked list of `(entry stack pointer, exit
frame pointer)` pairs. This linked list is maintained via Wasm-to-host and
host-to-Wasm trampolines. Within a sequence of Wasm-to-Wasm calls, we can use
frame pointers (which Cranelift preserves) to find the next older Wasm frame on
the stack, and we keep doing this until we reach the entry stack pointer,
meaning that the next older frame will be a host frame.
The trampolines need to avoid a couple stumbling blocks. First, they need to be
compiled ahead of time, since we may not have access to a compiler at
runtime (e.g. if the `cranelift` feature is disabled) but still want to be able
to call functions that have already been compiled and get stack traces for those
functions. Usually this means we would compile the appropriate trampolines
inside `Module::new` and the compiled module object would hold the
trampolines. However, we *also* need to support calling host functions that are
wrapped into `wasmtime::Func`s and there doesn't exist *any* ahead-of-time
compiled module object to hold the appropriate trampolines:
```rust
// Define a host function.
let func_type = wasmtime::FuncType::new(
vec![wasmtime::ValType::I32],
vec![wasmtime::ValType::I32],
);
let func = Func::new(&mut store, func_type, |_, params, results| {
// ...
Ok(())
});
// Call that host function.
let mut results = vec![wasmtime::Val::I32(0)];
func.call(&[wasmtime::Val::I32(0)], &mut results)?;
```
Therefore, we define one host-to-Wasm trampoline and one Wasm-to-host trampoline
in assembly that work for all Wasm and host function signatures. These
trampolines are careful to only use volatile registers, avoid touching any
register that is an argument in the calling convention ABI, and tail call to the
target callee function. This allows forwarding any set of arguments and any
returns to and from the callee, while also allowing us to maintain our linked
list of Wasm stack and frame pointers before transferring control to the
callee. These trampolines are not used in Wasm-to-Wasm calls, only when crossing
the host-Wasm boundary, so they do not impose overhead on regular calls. (And if
using one trampoline for all host-Wasm boundary crossing ever breaks branch
prediction enough in the CPU to become any kind of bottleneck, we can do fun
things like have multiple copies of the same trampoline and choose a random copy
for each function, sharding the functions across branch predictor entries.)
Finally, this commit also ends the use of a synthetic `Module` and allocating a
stubbed out `VMContext` for host functions. Instead, we define a
`VMHostFuncContext` with its own magic value, similar to `VMComponentContext`,
specifically for host functions.
<h2>Benchmarks</h2>
<h3>Traps and Stack Traces</h3>
Large improvements to taking stack traces on traps, ranging from shaving off 64%
to 99.95% of the time it used to take.
<details>
```
multi-threaded-traps/0 time: [2.5686 us 2.5808 us 2.5934 us]
thrpt: [0.0000 elem/s 0.0000 elem/s 0.0000 elem/s]
change:
time: [-85.419% -85.153% -84.869%] (p = 0.00 < 0.05)
thrpt: [+560.90% +573.56% +585.84%]
Performance has improved.
Found 8 outliers among 100 measurements (8.00%)
4 (4.00%) high mild
4 (4.00%) high severe
multi-threaded-traps/1 time: [2.9021 us 2.9167 us 2.9322 us]
thrpt: [341.04 Kelem/s 342.86 Kelem/s 344.58 Kelem/s]
change:
time: [-91.455% -91.294% -91.096%] (p = 0.00 < 0.05)
thrpt: [+1023.1% +1048.6% +1070.3%]
Performance has improved.
Found 6 outliers among 100 measurements (6.00%)
1 (1.00%) high mild
5 (5.00%) high severe
multi-threaded-traps/2 time: [2.9996 us 3.0145 us 3.0295 us]
thrpt: [660.18 Kelem/s 663.47 Kelem/s 666.76 Kelem/s]
change:
time: [-94.040% -93.910% -93.762%] (p = 0.00 < 0.05)
thrpt: [+1503.1% +1542.0% +1578.0%]
Performance has improved.
Found 5 outliers among 100 measurements (5.00%)
5 (5.00%) high severe
multi-threaded-traps/4 time: [5.5768 us 5.6052 us 5.6364 us]
thrpt: [709.68 Kelem/s 713.63 Kelem/s 717.25 Kelem/s]
change:
time: [-93.193% -93.121% -93.052%] (p = 0.00 < 0.05)
thrpt: [+1339.2% +1353.6% +1369.1%]
Performance has improved.
multi-threaded-traps/8 time: [8.6408 us 9.1212 us 9.5438 us]
thrpt: [838.24 Kelem/s 877.08 Kelem/s 925.84 Kelem/s]
change:
time: [-94.754% -94.473% -94.202%] (p = 0.00 < 0.05)
thrpt: [+1624.7% +1709.2% +1806.1%]
Performance has improved.
multi-threaded-traps/16 time: [10.152 us 10.840 us 11.545 us]
thrpt: [1.3858 Melem/s 1.4760 Melem/s 1.5761 Melem/s]
change:
time: [-97.042% -96.823% -96.577%] (p = 0.00 < 0.05)
thrpt: [+2821.5% +3048.1% +3281.1%]
Performance has improved.
Found 1 outliers among 100 measurements (1.00%)
1 (1.00%) high mild
many-modules-registered-traps/1
time: [2.6278 us 2.6361 us 2.6447 us]
thrpt: [378.11 Kelem/s 379.35 Kelem/s 380.55 Kelem/s]
change:
time: [-85.311% -85.108% -84.909%] (p = 0.00 < 0.05)
thrpt: [+562.65% +571.51% +580.76%]
Performance has improved.
Found 9 outliers among 100 measurements (9.00%)
3 (3.00%) high mild
6 (6.00%) high severe
many-modules-registered-traps/8
time: [2.6294 us 2.6460 us 2.6623 us]
thrpt: [3.0049 Melem/s 3.0235 Melem/s 3.0425 Melem/s]
change:
time: [-85.895% -85.485% -85.022%] (p = 0.00 < 0.05)
thrpt: [+567.63% +588.95% +608.95%]
Performance has improved.
Found 8 outliers among 100 measurements (8.00%)
3 (3.00%) high mild
5 (5.00%) high severe
many-modules-registered-traps/64
time: [2.6218 us 2.6329 us 2.6452 us]
thrpt: [24.195 Melem/s 24.308 Melem/s 24.411 Melem/s]
change:
time: [-93.629% -93.551% -93.470%] (p = 0.00 < 0.05)
thrpt: [+1431.4% +1450.6% +1469.5%]
Performance has improved.
Found 3 outliers among 100 measurements (3.00%)
3 (3.00%) high mild
many-modules-registered-traps/512
time: [2.6569 us 2.6737 us 2.6923 us]
thrpt: [190.17 Melem/s 191.50 Melem/s 192.71 Melem/s]
change:
time: [-99.277% -99.268% -99.260%] (p = 0.00 < 0.05)
thrpt: [+13417% +13566% +13731%]
Performance has improved.
Found 4 outliers among 100 measurements (4.00%)
4 (4.00%) high mild
many-modules-registered-traps/4096
time: [2.7258 us 2.7390 us 2.7535 us]
thrpt: [1.4876 Gelem/s 1.4955 Gelem/s 1.5027 Gelem/s]
change:
time: [-99.956% -99.955% -99.955%] (p = 0.00 < 0.05)
thrpt: [+221417% +223380% +224881%]
Performance has improved.
Found 2 outliers among 100 measurements (2.00%)
1 (1.00%) high mild
1 (1.00%) high severe
many-stack-frames-traps/1
time: [1.4658 us 1.4719 us 1.4784 us]
thrpt: [676.39 Kelem/s 679.38 Kelem/s 682.21 Kelem/s]
change:
time: [-90.368% -89.947% -89.586%] (p = 0.00 < 0.05)
thrpt: [+860.23% +894.72% +938.21%]
Performance has improved.
Found 8 outliers among 100 measurements (8.00%)
5 (5.00%) high mild
3 (3.00%) high severe
many-stack-frames-traps/8
time: [2.4772 us 2.4870 us 2.4973 us]
thrpt: [3.2034 Melem/s 3.2167 Melem/s 3.2294 Melem/s]
change:
time: [-85.550% -85.370% -85.199%] (p = 0.00 < 0.05)
thrpt: [+575.65% +583.51% +592.03%]
Performance has improved.
Found 8 outliers among 100 measurements (8.00%)
4 (4.00%) high mild
4 (4.00%) high severe
many-stack-frames-traps/64
time: [10.109 us 10.171 us 10.236 us]
thrpt: [6.2525 Melem/s 6.2925 Melem/s 6.3309 Melem/s]
change:
time: [-78.144% -77.797% -77.336%] (p = 0.00 < 0.05)
thrpt: [+341.22% +350.38% +357.55%]
Performance has improved.
Found 7 outliers among 100 measurements (7.00%)
5 (5.00%) high mild
2 (2.00%) high severe
many-stack-frames-traps/512
time: [126.16 us 126.54 us 126.96 us]
thrpt: [4.0329 Melem/s 4.0461 Melem/s 4.0583 Melem/s]
change:
time: [-65.364% -64.933% -64.453%] (p = 0.00 < 0.05)
thrpt: [+181.32% +185.17% +188.71%]
Performance has improved.
Found 4 outliers among 100 measurements (4.00%)
4 (4.00%) high severe
```
</details>
<h3>Calls</h3>
There is, however, a small regression in raw Wasm-to-host and host-to-Wasm call
performance due the new trampolines. It seems to be on the order of about 2-10
nanoseconds per call, depending on the benchmark.
I believe this regression is ultimately acceptable because
1. this overhead will be vastly dominated by whatever work a non-nop callee
actually does,
2. we will need these trampolines, or something like them, when implementing the
Wasm exceptions proposal to do things like translate Wasm's exceptions into
Rust's `Result`s,
3. and because the performance improvements to trapping and capturing stack
traces are of such a larger magnitude than this call regressions.
<details>
```
sync/no-hook/host-to-wasm - typed - nop
time: [28.683 ns 28.757 ns 28.844 ns]
change: [+16.472% +17.183% +17.904%] (p = 0.00 < 0.05)
Performance has regressed.
Found 10 outliers among 100 measurements (10.00%)
1 (1.00%) low mild
4 (4.00%) high mild
5 (5.00%) high severe
sync/no-hook/host-to-wasm - untyped - nop
time: [42.515 ns 42.652 ns 42.841 ns]
change: [+12.371% +14.614% +17.462%] (p = 0.00 < 0.05)
Performance has regressed.
Found 11 outliers among 100 measurements (11.00%)
1 (1.00%) high mild
10 (10.00%) high severe
sync/no-hook/host-to-wasm - unchecked - nop
time: [33.936 ns 34.052 ns 34.179 ns]
change: [+25.478% +26.938% +28.369%] (p = 0.00 < 0.05)
Performance has regressed.
Found 9 outliers among 100 measurements (9.00%)
7 (7.00%) high mild
2 (2.00%) high severe
sync/no-hook/host-to-wasm - typed - nop-params-and-results
time: [34.290 ns 34.388 ns 34.502 ns]
change: [+40.802% +42.706% +44.526%] (p = 0.00 < 0.05)
Performance has regressed.
Found 13 outliers among 100 measurements (13.00%)
5 (5.00%) high mild
8 (8.00%) high severe
sync/no-hook/host-to-wasm - untyped - nop-params-and-results
time: [62.546 ns 62.721 ns 62.919 ns]
change: [+2.5014% +3.6319% +4.8078%] (p = 0.00 < 0.05)
Performance has regressed.
Found 12 outliers among 100 measurements (12.00%)
2 (2.00%) high mild
10 (10.00%) high severe
sync/no-hook/host-to-wasm - unchecked - nop-params-and-results
time: [42.609 ns 42.710 ns 42.831 ns]
change: [+20.966% +22.282% +23.475%] (p = 0.00 < 0.05)
Performance has regressed.
Found 11 outliers among 100 measurements (11.00%)
4 (4.00%) high mild
7 (7.00%) high severe
sync/hook-sync/host-to-wasm - typed - nop
time: [29.546 ns 29.675 ns 29.818 ns]
change: [+20.693% +21.794% +22.836%] (p = 0.00 < 0.05)
Performance has regressed.
Found 5 outliers among 100 measurements (5.00%)
3 (3.00%) high mild
2 (2.00%) high severe
sync/hook-sync/host-to-wasm - untyped - nop
time: [45.448 ns 45.699 ns 45.961 ns]
change: [+17.204% +18.514% +19.590%] (p = 0.00 < 0.05)
Performance has regressed.
Found 14 outliers among 100 measurements (14.00%)
4 (4.00%) high mild
10 (10.00%) high severe
sync/hook-sync/host-to-wasm - unchecked - nop
time: [34.334 ns 34.437 ns 34.558 ns]
change: [+23.225% +24.477% +25.886%] (p = 0.00 < 0.05)
Performance has regressed.
Found 12 outliers among 100 measurements (12.00%)
5 (5.00%) high mild
7 (7.00%) high severe
sync/hook-sync/host-to-wasm - typed - nop-params-and-results
time: [36.594 ns 36.763 ns 36.974 ns]
change: [+41.967% +47.261% +52.086%] (p = 0.00 < 0.05)
Performance has regressed.
Found 12 outliers among 100 measurements (12.00%)
3 (3.00%) high mild
9 (9.00%) high severe
sync/hook-sync/host-to-wasm - untyped - nop-params-and-results
time: [63.541 ns 63.831 ns 64.194 ns]
change: [-4.4337% -0.6855% +2.7134%] (p = 0.73 > 0.05)
No change in performance detected.
Found 8 outliers among 100 measurements (8.00%)
6 (6.00%) high mild
2 (2.00%) high severe
sync/hook-sync/host-to-wasm - unchecked - nop-params-and-results
time: [43.968 ns 44.169 ns 44.437 ns]
change: [+18.772% +21.802% +24.623%] (p = 0.00 < 0.05)
Performance has regressed.
Found 15 outliers among 100 measurements (15.00%)
3 (3.00%) high mild
12 (12.00%) high severe
async/no-hook/host-to-wasm - typed - nop
time: [4.9612 us 4.9743 us 4.9889 us]
change: [+9.9493% +11.911% +13.502%] (p = 0.00 < 0.05)
Performance has regressed.
Found 10 outliers among 100 measurements (10.00%)
6 (6.00%) high mild
4 (4.00%) high severe
async/no-hook/host-to-wasm - untyped - nop
time: [5.0030 us 5.0211 us 5.0439 us]
change: [+10.841% +11.873% +12.977%] (p = 0.00 < 0.05)
Performance has regressed.
Found 10 outliers among 100 measurements (10.00%)
3 (3.00%) high mild
7 (7.00%) high severe
async/no-hook/host-to-wasm - typed - nop-params-and-results
time: [4.9273 us 4.9468 us 4.9700 us]
change: [+4.7381% +6.8445% +8.8238%] (p = 0.00 < 0.05)
Performance has regressed.
Found 14 outliers among 100 measurements (14.00%)
5 (5.00%) high mild
9 (9.00%) high severe
async/no-hook/host-to-wasm - untyped - nop-params-and-results
time: [5.1151 us 5.1338 us 5.1555 us]
change: [+9.5335% +11.290% +13.044%] (p = 0.00 < 0.05)
Performance has regressed.
Found 16 outliers among 100 measurements (16.00%)
3 (3.00%) high mild
13 (13.00%) high severe
async/hook-sync/host-to-wasm - typed - nop
time: [4.9330 us 4.9394 us 4.9467 us]
change: [+10.046% +11.038% +12.035%] (p = 0.00 < 0.05)
Performance has regressed.
Found 12 outliers among 100 measurements (12.00%)
5 (5.00%) high mild
7 (7.00%) high severe
async/hook-sync/host-to-wasm - untyped - nop
time: [5.0073 us 5.0183 us 5.0310 us]
change: [+9.3828% +10.565% +11.752%] (p = 0.00 < 0.05)
Performance has regressed.
Found 8 outliers among 100 measurements (8.00%)
3 (3.00%) high mild
5 (5.00%) high severe
async/hook-sync/host-to-wasm - typed - nop-params-and-results
time: [4.9610 us 4.9839 us 5.0097 us]
change: [+9.0857% +11.513% +14.359%] (p = 0.00 < 0.05)
Performance has regressed.
Found 13 outliers among 100 measurements (13.00%)
7 (7.00%) high mild
6 (6.00%) high severe
async/hook-sync/host-to-wasm - untyped - nop-params-and-results
time: [5.0995 us 5.1272 us 5.1617 us]
change: [+9.3600% +11.506% +13.809%] (p = 0.00 < 0.05)
Performance has regressed.
Found 10 outliers among 100 measurements (10.00%)
6 (6.00%) high mild
4 (4.00%) high severe
async-pool/no-hook/host-to-wasm - typed - nop
time: [2.4242 us 2.4316 us 2.4396 us]
change: [+7.8756% +8.8803% +9.8346%] (p = 0.00 < 0.05)
Performance has regressed.
Found 8 outliers among 100 measurements (8.00%)
5 (5.00%) high mild
3 (3.00%) high severe
async-pool/no-hook/host-to-wasm - untyped - nop
time: [2.5102 us 2.5155 us 2.5210 us]
change: [+12.130% +13.194% +14.270%] (p = 0.00 < 0.05)
Performance has regressed.
Found 12 outliers among 100 measurements (12.00%)
4 (4.00%) high mild
8 (8.00%) high severe
async-pool/no-hook/host-to-wasm - typed - nop-params-and-results
time: [2.4203 us 2.4310 us 2.4440 us]
change: [+4.0380% +6.3623% +8.7534%] (p = 0.00 < 0.05)
Performance has regressed.
Found 14 outliers among 100 measurements (14.00%)
5 (5.00%) high mild
9 (9.00%) high severe
async-pool/no-hook/host-to-wasm - untyped - nop-params-and-results
time: [2.5501 us 2.5593 us 2.5700 us]
change: [+8.8802% +10.976% +12.937%] (p = 0.00 < 0.05)
Performance has regressed.
Found 16 outliers among 100 measurements (16.00%)
5 (5.00%) high mild
11 (11.00%) high severe
async-pool/hook-sync/host-to-wasm - typed - nop
time: [2.4135 us 2.4190 us 2.4254 us]
change: [+8.3640% +9.3774% +10.435%] (p = 0.00 < 0.05)
Performance has regressed.
Found 11 outliers among 100 measurements (11.00%)
6 (6.00%) high mild
5 (5.00%) high severe
async-pool/hook-sync/host-to-wasm - untyped - nop
time: [2.5172 us 2.5248 us 2.5357 us]
change: [+11.543% +12.750% +13.982%] (p = 0.00 < 0.05)
Performance has regressed.
Found 8 outliers among 100 measurements (8.00%)
1 (1.00%) high mild
7 (7.00%) high severe
async-pool/hook-sync/host-to-wasm - typed - nop-params-and-results
time: [2.4214 us 2.4353 us 2.4532 us]
change: [+1.5158% +5.0872% +8.6765%] (p = 0.00 < 0.05)
Performance has regressed.
Found 15 outliers among 100 measurements (15.00%)
2 (2.00%) high mild
13 (13.00%) high severe
async-pool/hook-sync/host-to-wasm - untyped - nop-params-and-results
time: [2.5499 us 2.5607 us 2.5748 us]
change: [+10.146% +12.459% +14.919%] (p = 0.00 < 0.05)
Performance has regressed.
Found 18 outliers among 100 measurements (18.00%)
3 (3.00%) high mild
15 (15.00%) high severe
sync/no-hook/wasm-to-host - nop - typed
time: [6.6135 ns 6.6288 ns 6.6452 ns]
change: [+37.927% +38.837% +39.869%] (p = 0.00 < 0.05)
Performance has regressed.
Found 7 outliers among 100 measurements (7.00%)
2 (2.00%) high mild
5 (5.00%) high severe
sync/no-hook/wasm-to-host - nop-params-and-results - typed
time: [15.930 ns 15.993 ns 16.067 ns]
change: [+3.9583% +5.6286% +7.2430%] (p = 0.00 < 0.05)
Performance has regressed.
Found 12 outliers among 100 measurements (12.00%)
11 (11.00%) high mild
1 (1.00%) high severe
sync/no-hook/wasm-to-host - nop - untyped
time: [20.596 ns 20.640 ns 20.690 ns]
change: [+4.3293% +5.2047% +6.0935%] (p = 0.00 < 0.05)
Performance has regressed.
Found 10 outliers among 100 measurements (10.00%)
5 (5.00%) high mild
5 (5.00%) high severe
sync/no-hook/wasm-to-host - nop-params-and-results - untyped
time: [42.659 ns 42.882 ns 43.159 ns]
change: [-2.1466% -0.5079% +1.2554%] (p = 0.58 > 0.05)
No change in performance detected.
Found 15 outliers among 100 measurements (15.00%)
1 (1.00%) high mild
14 (14.00%) high severe
sync/no-hook/wasm-to-host - nop - unchecked
time: [10.671 ns 10.691 ns 10.713 ns]
change: [+83.911% +87.620% +92.062%] (p = 0.00 < 0.05)
Performance has regressed.
Found 9 outliers among 100 measurements (9.00%)
2 (2.00%) high mild
7 (7.00%) high severe
sync/no-hook/wasm-to-host - nop-params-and-results - unchecked
time: [11.136 ns 11.190 ns 11.263 ns]
change: [-29.719% -28.446% -27.029%] (p = 0.00 < 0.05)
Performance has improved.
Found 14 outliers among 100 measurements (14.00%)
4 (4.00%) high mild
10 (10.00%) high severe
sync/hook-sync/wasm-to-host - nop - typed
time: [6.7964 ns 6.8087 ns 6.8226 ns]
change: [+21.531% +24.206% +27.331%] (p = 0.00 < 0.05)
Performance has regressed.
Found 14 outliers among 100 measurements (14.00%)
4 (4.00%) high mild
10 (10.00%) high severe
sync/hook-sync/wasm-to-host - nop-params-and-results - typed
time: [15.865 ns 15.921 ns 15.985 ns]
change: [+4.8466% +6.3330% +7.8317%] (p = 0.00 < 0.05)
Performance has regressed.
Found 16 outliers among 100 measurements (16.00%)
3 (3.00%) high mild
13 (13.00%) high severe
sync/hook-sync/wasm-to-host - nop - untyped
time: [21.505 ns 21.587 ns 21.677 ns]
change: [+8.0908% +9.1943% +10.254%] (p = 0.00 < 0.05)
Performance has regressed.
Found 8 outliers among 100 measurements (8.00%)
4 (4.00%) high mild
4 (4.00%) high severe
sync/hook-sync/wasm-to-host - nop-params-and-results - untyped
time: [44.018 ns 44.128 ns 44.261 ns]
change: [-1.4671% -0.0458% +1.2443%] (p = 0.94 > 0.05)
No change in performance detected.
Found 14 outliers among 100 measurements (14.00%)
5 (5.00%) high mild
9 (9.00%) high severe
sync/hook-sync/wasm-to-host - nop - unchecked
time: [11.264 ns 11.326 ns 11.387 ns]
change: [+80.225% +81.659% +83.068%] (p = 0.00 < 0.05)
Performance has regressed.
Found 6 outliers among 100 measurements (6.00%)
3 (3.00%) high mild
3 (3.00%) high severe
sync/hook-sync/wasm-to-host - nop-params-and-results - unchecked
time: [11.816 ns 11.865 ns 11.920 ns]
change: [-29.152% -28.040% -26.957%] (p = 0.00 < 0.05)
Performance has improved.
Found 14 outliers among 100 measurements (14.00%)
8 (8.00%) high mild
6 (6.00%) high severe
async/no-hook/wasm-to-host - nop - typed
time: [6.6221 ns 6.6385 ns 6.6569 ns]
change: [+43.618% +44.755% +45.965%] (p = 0.00 < 0.05)
Performance has regressed.
Found 13 outliers among 100 measurements (13.00%)
6 (6.00%) high mild
7 (7.00%) high severe
async/no-hook/wasm-to-host - nop-params-and-results - typed
time: [15.884 ns 15.929 ns 15.983 ns]
change: [+3.5987% +5.2053% +6.7846%] (p = 0.00 < 0.05)
Performance has regressed.
Found 16 outliers among 100 measurements (16.00%)
3 (3.00%) high mild
13 (13.00%) high severe
async/no-hook/wasm-to-host - nop - untyped
time: [20.615 ns 20.702 ns 20.821 ns]
change: [+6.9799% +8.1212% +9.2819%] (p = 0.00 < 0.05)
Performance has regressed.
Found 10 outliers among 100 measurements (10.00%)
2 (2.00%) high mild
8 (8.00%) high severe
async/no-hook/wasm-to-host - nop-params-and-results - untyped
time: [41.956 ns 42.207 ns 42.521 ns]
change: [-4.3057% -2.7730% -1.2428%] (p = 0.00 < 0.05)
Performance has improved.
Found 14 outliers among 100 measurements (14.00%)
3 (3.00%) high mild
11 (11.00%) high severe
async/no-hook/wasm-to-host - nop - unchecked
time: [10.440 ns 10.474 ns 10.513 ns]
change: [+83.959% +85.826% +87.541%] (p = 0.00 < 0.05)
Performance has regressed.
Found 11 outliers among 100 measurements (11.00%)
5 (5.00%) high mild
6 (6.00%) high severe
async/no-hook/wasm-to-host - nop-params-and-results - unchecked
time: [11.476 ns 11.512 ns 11.554 ns]
change: [-29.857% -28.383% -26.978%] (p = 0.00 < 0.05)
Performance has improved.
Found 12 outliers among 100 measurements (12.00%)
1 (1.00%) low mild
6 (6.00%) high mild
5 (5.00%) high severe
async/no-hook/wasm-to-host - nop - async-typed
time: [26.427 ns 26.478 ns 26.532 ns]
change: [+6.5730% +7.4676% +8.3983%] (p = 0.00 < 0.05)
Performance has regressed.
Found 9 outliers among 100 measurements (9.00%)
2 (2.00%) high mild
7 (7.00%) high severe
async/no-hook/wasm-to-host - nop-params-and-results - async-typed
time: [28.557 ns 28.693 ns 28.880 ns]
change: [+1.9099% +3.7332% +5.9731%] (p = 0.00 < 0.05)
Performance has regressed.
Found 15 outliers among 100 measurements (15.00%)
1 (1.00%) high mild
14 (14.00%) high severe
async/hook-sync/wasm-to-host - nop - typed
time: [6.7488 ns 6.7630 ns 6.7784 ns]
change: [+19.935% +22.080% +23.683%] (p = 0.00 < 0.05)
Performance has regressed.
Found 9 outliers among 100 measurements (9.00%)
4 (4.00%) high mild
5 (5.00%) high severe
async/hook-sync/wasm-to-host - nop-params-and-results - typed
time: [15.928 ns 16.031 ns 16.149 ns]
change: [+5.5188% +6.9567% +8.3839%] (p = 0.00 < 0.05)
Performance has regressed.
Found 11 outliers among 100 measurements (11.00%)
9 (9.00%) high mild
2 (2.00%) high severe
async/hook-sync/wasm-to-host - nop - untyped
time: [21.930 ns 22.114 ns 22.296 ns]
change: [+4.6674% +7.7588% +10.375%] (p = 0.00 < 0.05)
Performance has regressed.
Found 4 outliers among 100 measurements (4.00%)
3 (3.00%) high mild
1 (1.00%) high severe
async/hook-sync/wasm-to-host - nop-params-and-results - untyped
time: [42.684 ns 42.858 ns 43.081 ns]
change: [-5.2957% -3.4693% -1.6217%] (p = 0.00 < 0.05)
Performance has improved.
Found 14 outliers among 100 measurements (14.00%)
2 (2.00%) high mild
12 (12.00%) high severe
async/hook-sync/wasm-to-host - nop - unchecked
time: [11.026 ns 11.053 ns 11.086 ns]
change: [+70.751% +72.378% +73.961%] (p = 0.00 < 0.05)
Performance has regressed.
Found 10 outliers among 100 measurements (10.00%)
5 (5.00%) high mild
5 (5.00%) high severe
async/hook-sync/wasm-to-host - nop-params-and-results - unchecked
time: [11.840 ns 11.900 ns 11.982 ns]
change: [-27.977% -26.584% -24.887%] (p = 0.00 < 0.05)
Performance has improved.
Found 18 outliers among 100 measurements (18.00%)
3 (3.00%) high mild
15 (15.00%) high severe
async/hook-sync/wasm-to-host - nop - async-typed
time: [27.601 ns 27.709 ns 27.882 ns]
change: [+8.1781% +9.1102% +10.030%] (p = 0.00 < 0.05)
Performance has regressed.
Found 11 outliers among 100 measurements (11.00%)
2 (2.00%) low mild
3 (3.00%) high mild
6 (6.00%) high severe
async/hook-sync/wasm-to-host - nop-params-and-results - async-typed
time: [28.955 ns 29.174 ns 29.413 ns]
change: [+1.1226% +3.0366% +5.1126%] (p = 0.00 < 0.05)
Performance has regressed.
Found 13 outliers among 100 measurements (13.00%)
7 (7.00%) high mild
6 (6.00%) high severe
async-pool/no-hook/wasm-to-host - nop - typed
time: [6.5626 ns 6.5733 ns 6.5851 ns]
change: [+40.561% +42.307% +44.514%] (p = 0.00 < 0.05)
Performance has regressed.
Found 9 outliers among 100 measurements (9.00%)
5 (5.00%) high mild
4 (4.00%) high severe
async-pool/no-hook/wasm-to-host - nop-params-and-results - typed
time: [15.820 ns 15.886 ns 15.969 ns]
change: [+4.1044% +5.7928% +7.7122%] (p = 0.00 < 0.05)
Performance has regressed.
Found 17 outliers among 100 measurements (17.00%)
4 (4.00%) high mild
13 (13.00%) high severe
async-pool/no-hook/wasm-to-host - nop - untyped
time: [20.481 ns 20.521 ns 20.566 ns]
change: [+6.7962% +7.6950% +8.7612%] (p = 0.00 < 0.05)
Performance has regressed.
Found 11 outliers among 100 measurements (11.00%)
6 (6.00%) high mild
5 (5.00%) high severe
async-pool/no-hook/wasm-to-host - nop-params-and-results - untyped
time: [41.834 ns 41.998 ns 42.189 ns]
change: [-3.8185% -2.2687% -0.7541%] (p = 0.01 < 0.05)
Change within noise threshold.
Found 13 outliers among 100 measurements (13.00%)
3 (3.00%) high mild
10 (10.00%) high severe
async-pool/no-hook/wasm-to-host - nop - unchecked
time: [10.353 ns 10.380 ns 10.414 ns]
change: [+82.042% +84.591% +87.205%] (p = 0.00 < 0.05)
Performance has regressed.
Found 7 outliers among 100 measurements (7.00%)
4 (4.00%) high mild
3 (3.00%) high severe
async-pool/no-hook/wasm-to-host - nop-params-and-results - unchecked
time: [11.123 ns 11.168 ns 11.228 ns]
change: [-30.813% -29.285% -27.874%] (p = 0.00 < 0.05)
Performance has improved.
Found 12 outliers among 100 measurements (12.00%)
11 (11.00%) high mild
1 (1.00%) high severe
async-pool/no-hook/wasm-to-host - nop - async-typed
time: [27.442 ns 27.528 ns 27.638 ns]
change: [+7.5215% +9.9795% +12.266%] (p = 0.00 < 0.05)
Performance has regressed.
Found 18 outliers among 100 measurements (18.00%)
3 (3.00%) high mild
15 (15.00%) high severe
async-pool/no-hook/wasm-to-host - nop-params-and-results - async-typed
time: [29.014 ns 29.148 ns 29.312 ns]
change: [+2.0227% +3.4722% +4.9047%] (p = 0.00 < 0.05)
Performance has regressed.
Found 7 outliers among 100 measurements (7.00%)
6 (6.00%) high mild
1 (1.00%) high severe
async-pool/hook-sync/wasm-to-host - nop - typed
time: [6.7916 ns 6.8116 ns 6.8325 ns]
change: [+20.937% +22.050% +23.281%] (p = 0.00 < 0.05)
Performance has regressed.
Found 11 outliers among 100 measurements (11.00%)
5 (5.00%) high mild
6 (6.00%) high severe
async-pool/hook-sync/wasm-to-host - nop-params-and-results - typed
time: [15.917 ns 15.975 ns 16.051 ns]
change: [+4.6404% +6.4217% +8.3075%] (p = 0.00 < 0.05)
Performance has regressed.
Found 16 outliers among 100 measurements (16.00%)
5 (5.00%) high mild
11 (11.00%) high severe
async-pool/hook-sync/wasm-to-host - nop - untyped
time: [21.558 ns 21.612 ns 21.679 ns]
change: [+8.1158% +9.1409% +10.217%] (p = 0.00 < 0.05)
Performance has regressed.
Found 9 outliers among 100 measurements (9.00%)
2 (2.00%) high mild
7 (7.00%) high severe
async-pool/hook-sync/wasm-to-host - nop-params-and-results - untyped
time: [42.475 ns 42.614 ns 42.775 ns]
change: [-6.3613% -4.4709% -2.7647%] (p = 0.00 < 0.05)
Performance has improved.
Found 18 outliers among 100 measurements (18.00%)
3 (3.00%) high mild
15 (15.00%) high severe
async-pool/hook-sync/wasm-to-host - nop - unchecked
time: [11.150 ns 11.195 ns 11.247 ns]
change: [+74.424% +77.056% +79.811%] (p = 0.00 < 0.05)
Performance has regressed.
Found 14 outliers among 100 measurements (14.00%)
3 (3.00%) high mild
11 (11.00%) high severe
async-pool/hook-sync/wasm-to-host - nop-params-and-results - unchecked
time: [11.639 ns 11.695 ns 11.760 ns]
change: [-30.212% -29.023% -27.954%] (p = 0.00 < 0.05)
Performance has improved.
Found 15 outliers among 100 measurements (15.00%)
7 (7.00%) high mild
8 (8.00%) high severe
async-pool/hook-sync/wasm-to-host - nop - async-typed
time: [27.480 ns 27.712 ns 27.984 ns]
change: [+2.9764% +6.5061% +9.8914%] (p = 0.00 < 0.05)
Performance has regressed.
Found 8 outliers among 100 measurements (8.00%)
6 (6.00%) high mild
2 (2.00%) high severe
async-pool/hook-sync/wasm-to-host - nop-params-and-results - async-typed
time: [29.218 ns 29.380 ns 29.600 ns]
change: [+5.2283% +7.7247% +10.822%] (p = 0.00 < 0.05)
Performance has regressed.
Found 16 outliers among 100 measurements (16.00%)
2 (2.00%) high mild
14 (14.00%) high severe
```
</details>
* Add s390x support for frame pointer-based stack walking
* wasmtime: Allow `Caller::get_export` to get all exports
* fuzzing: Add a fuzz target to check that our stack traces are correct
We generate Wasm modules that keep track of their own stack as they call and
return between functions, and then we periodically check that if the host
captures a backtrace, it matches what the Wasm module has recorded.
* Remove VM offsets for `VMHostFuncContext` since it isn't used by JIT code
* Add doc comment with stack walking implementation notes
* Document the extra state that can be passed to `wasmtime_runtime::Backtrace` methods
* Add extensive comments for stack walking function
* Factor architecture-specific bits of stack walking out into modules
* Initialize store-related fields in a vmctx to null when there is no store yet
Rather than leaving them as uninitialized data.
* Use `set_callee` instead of manually setting the vmctx field
* Use a more informative compile error message for unsupported architectures
* Document unsafety of `prepare_host_to_wasm_trampoline`
* Use `bti c` instead of `hint #34` in inline aarch64 assembly
* Remove outdated TODO comment
* Remove setting of `last_wasm_exit_fp` in `set_jit_trap`
This is no longer needed as the value is plumbed through to the backtrace code
directly now.
* Only set the stack limit once, in the face of re-entrancy into Wasm
* Add comments for s390x-specific stack walking bits
* Use the helper macro for all libcalls
If we forget to use it, and then trigger a GC from the libcall, that means we
could miss stack frames when walking the stack, fail to find live GC refs, and
then get use after free bugs. Much less risky to always use the helper macro
that takes care of all of that for us.
* Use the `asm_sym!` macro in Wasm-to-libcall trampolines
This macro handles the macOS-specific underscore prefix stuff for us.
* wasmtime: add size and align to `externref` assertion error message
* Extend the `stacks` fuzzer to have host frames in between Wasm frames
This way we get one or more contiguous sequences of Wasm frames on the stack,
instead of exactly one.
* Add documentation for aarch64-specific backtrace helpers
* Clarify that we only support little-endian aarch64 in trampoline comment
* Use `.machine z13` in s390x assembly file
Since apparently our CI machines have pretty old assemblers that don't have
`.machine z14`. This should be fine though since these trampolines don't make
use of anything that is introduced in z14.
* Fix aarch64 build
* Fix macOS build
* Document the `asm_sym!` macro
* Add windows support to the `wasmtime-asm-macros` crate
* Add windows support to host<--->Wasm trampolines
* Fix trap handler build on windows
* Run `rustfmt` on s390x trampoline source file
* Temporarily disable some assertions about a trap's backtrace in the component model tests
Follow up to re-enable this and fix the associated issue:
https://github.com/bytecodealliance/wasmtime/issues/4535
* Refactor libcall definitions with less macros
This refactors the `libcall!` macro to use the
`foreach_builtin_function!` macro to define all of the trampolines.
Additionally the macro surrounding each libcall itself is no longer
necessary and helps avoid too many macros.
* Use `VMOpaqueContext::from_vm_host_func_context` in `VMHostFuncContext::new`
* Move `backtrace` module to be submodule of `traphandlers`
This avoids making some things `pub(crate)` in `traphandlers` that really
shouldn't be.
* Fix macOS aarch64 build
* Use "i64" instead of "word" in aarch64-specific file
* Save/restore entry SP and exit FP/return pointer in the face of panicking imported host functions
Also clean up assertions surrounding our saved entry/exit registers.
* Put "typed" vs "untyped" in the same position of call benchmark names
Regardless if we are doing wasm-to-host or host-to-wasm
* Fix stacks test case generator build for new `wasm-encoder`
* Fix build for s390x
* Expand libcalls in s390x asm
* Disable more parts of component tests now that backtrace assertions are a bit tighter
* Remove assertion that can maybe fail on s390x
Co-authored-by: Ulrich Weigand <ulrich.weigand@de.ibm.com>
Co-authored-by: Alex Crichton <alex@alexcrichton.com>
2 years ago
|
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|
[[bin]]
|
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|
name = "stacks"
|
|
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|
path = "fuzz_targets/stacks.rs"
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test = false
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doc = false
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[[bin]]
|
Refactor fuzzing configuration and sometimes disable debug verifier. (#3664)
* fuzz: Refactor Wasmtime's fuzz targets
A recent fuzz bug found is related to timing out when compiling a
module. This timeout, however, is predominately because Cranelift's
debug verifier is enabled and taking up over half the compilation time.
I wanted to fix this by disabling the verifier when input modules might
have a lot of functions, but this was pretty difficult to implement.
Over time we've grown a number of various fuzzers. Most are
`wasm-smith`-based at this point but there's various entry points for
configuring the wasm-smith module, the wasmtime configuration, etc. I've
historically gotten quite lost in trying to change defaults and feeling
like I have to touch a lot of different places. This is the motivation
for this commit, simplifying fuzzer default configuration.
This commit removes the ability to create a default `Config` for
fuzzing, instead only supporting generating a configuration via
`Arbitrary`. This then involved refactoring all targets and fuzzers to
ensure that configuration is generated through `Arbitrary`. This should
actually expand the coverage of some existing fuzz targets since
`Arbitrary for Config` will tweak options that don't affect runtime,
such as memory configuration or jump veneers.
All existing fuzz targets are refactored to use this new method of
configuration. Some fuzz targets were also shuffled around or
reimplemented:
* `compile` - this now directly calls `Module::new` to skip all the
fuzzing infrastructure. This is mostly done because this fuzz target
isn't too interesting and is largely just seeing what happens when
things are thrown at the wall for Wasmtime.
* `instantiate-maybe-invalid` - this fuzz target now skips instantiation
and instead simply goes into `Module::new` like the `compile` target.
The rationale behind this is that most modules won't instantiate
anyway and this fuzz target is primarily fuzzing the compiler. This
skips having to generate arbitrary configuration since
wasm-smith-generated-modules (or valid ones at least) aren't used
here.
* `instantiate` - this fuzz target was removed. In general this fuzz
target isn't too interesting in isolation. Almost everything it deals
with likely won't pass compilation and is covered by the `compile`
fuzz target, and otherwise interesting modules being instantiated can
all theoretically be created by `wasm-smith` anyway.
* `instantiate-wasm-smith` and `instantiate-swarm` - these were both merged
into a new `instantiate` target (replacing the old one from above).
There wasn't really much need to keep these separate since they really
only differed at this point in methods of timeout. Otherwise we much
more heavily use `SwarmConfig` than wasm-smith's built-in options.
The intention is that we should still have basically the same coverage
of fuzzing as before, if not better because configuration is now
possible on some targets. Additionally there is one centralized point of
configuration for fuzzing for wasmtime, `Arbitrary for ModuleConfig`.
This internally creates an arbitrary `SwarmConfig` from `wasm-smith` and
then further tweaks it for Wasmtime's needs, such as enabling various
wasm proposals by default. In the future enabling a wasm proposal on
fuzzing should largely just be modifying this one trait implementation.
* fuzz: Sometimes disable the cranelift debug verifier
This commit disables the cranelift debug verifier if the input wasm
module might be "large" for the definition of "more than 10 functions".
While fuzzing we disable threads (set them to 1) and enable the
cranelift debug verifier. Coupled with a 20-30x slowdown this means that
a module with the maximum number of functions, 100, gives:
60x / 100 functions / 30x slowdown = 20ms
With only 20 milliseconds per function this is even further halved by
the `differential` fuzz target compiling a module twice, which means
that, when compiling with a normal release mode Wasmtime, if any
function takes more than 10ms to compile then it's a candidate for
timing out while fuzzing. Given that the cranelift debug verifier can
more than double compilation time in fuzzing mode this actually means
that the real time budget for function compilation is more like 4ms.
The `wasm-smith` crate can pretty easily generate a large function that
takes 4ms to compile, and then when that function is multiplied 100x in
the `differential` fuzz target we trivially time out the fuzz target.
The hope of this commit is to buy back half our budget by disabling the
debug verifier for modules that may have many functions. Further
refinements can be implemented in the future such as limiting functions
for just the differential target as well.
* Fix the single-function-module fuzz configuration
* Tweak how features work in differential fuzzing
* Disable everything for baseline differential fuzzing
* Enable selectively for each engine afterwards
* Also forcibly enable reference types and bulk memory for spec tests
* Log wasms when compiling
* Add reference types support to v8 fuzzer
* Fix timeouts via fuel
The default store has "infinite" fuel so that needs to be consumed
before fuel is added back in.
* Remove fuzzing-specific tests
These no longer compile and also haven't been added to in a long time.
Most of the time a reduced form of original the fuzz test case is added
when a fuzz bug is fixed.
3 years ago
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name = "compile-maybe-invalid"
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path = "fuzz_targets/compile-maybe-invalid.rs"
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test = false
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doc = false
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[[bin]]
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name = "cranelift-fuzzgen"
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path = "fuzz_targets/cranelift-fuzzgen.rs"
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test = false
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doc = false
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[[bin]]
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name = "instantiate-many"
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path = "fuzz_targets/instantiate-many.rs"
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test = false
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doc = false
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[[bin]]
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name = "component_api"
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path = "fuzz_targets/component_api.rs"
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test = false
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doc = false
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Implement an incremental compilation cache for Cranelift (#4551)
This is the implementation of https://github.com/bytecodealliance/wasmtime/issues/4155, using the "inverted API" approach suggested by @cfallin (thanks!) in Cranelift, and trait object to provide a backend for an all-included experience in Wasmtime.
After the suggestion of Chris, `Function` has been split into mostly two parts:
- on the one hand, `FunctionStencil` contains all the fields required during compilation, and that act as a compilation cache key: if two function stencils are the same, then the result of their compilation (`CompiledCodeBase<Stencil>`) will be the same. This makes caching trivial, as the only thing to cache is the `FunctionStencil`.
- on the other hand, `FunctionParameters` contain the... function parameters that are required to finalize the result of compilation into a `CompiledCode` (aka `CompiledCodeBase<Final>`) with proper final relocations etc., by applying fixups and so on.
Most changes are here to accomodate those requirements, in particular that `FunctionStencil` should be `Hash`able to be used as a key in the cache:
- most source locations are now relative to a base source location in the function, and as such they're encoded as `RelSourceLoc` in the `FunctionStencil`. This required changes so that there's no need to explicitly mark a `SourceLoc` as the base source location, it's automatically detected instead the first time a non-default `SourceLoc` is set.
- user-defined external names in the `FunctionStencil` (aka before this patch `ExternalName::User { namespace, index }`) are now references into an external table of `UserExternalNameRef -> UserExternalName`, present in the `FunctionParameters`, and must be explicitly declared using `Function::declare_imported_user_function`.
- some refactorings have been made for function names:
- `ExternalName` was used as the type for a `Function`'s name; while it thus allowed `ExternalName::Libcall` in this place, this would have been quite confusing to use it there. Instead, a new enum `UserFuncName` is introduced for this name, that's either a user-defined function name (the above `UserExternalName`) or a test case name.
- The future of `ExternalName` is likely to become a full reference into the `FunctionParameters`'s mapping, instead of being "either a handle for user-defined external names, or the thing itself for other variants". I'm running out of time to do this, and this is not trivial as it implies touching ISLE which I'm less familiar with.
The cache computes a sha256 hash of the `FunctionStencil`, and uses this as the cache key. No equality check (using `PartialEq`) is performed in addition to the hash being the same, as we hope that this is sufficient data to avoid collisions.
A basic fuzz target has been introduced that tries to do the bare minimum:
- check that a function successfully compiled and cached will be also successfully reloaded from the cache, and returns the exact same function.
- check that a trivial modification in the external mapping of `UserExternalNameRef -> UserExternalName` hits the cache, and that other modifications don't hit the cache.
- This last check is less efficient and less likely to happen, so probably should be rethought a bit.
Thanks to both @alexcrichton and @cfallin for your very useful feedback on Zulip.
Some numbers show that for a large wasm module we're using internally, this is a 20% compile-time speedup, because so many `FunctionStencil`s are the same, even within a single module. For a group of modules that have a lot of code in common, we get hit rates up to 70% when they're used together. When a single function changes in a wasm module, every other function is reloaded; that's still slower than I expect (between 10% and 50% of the overall compile time), so there's likely room for improvement.
Fixes #4155.
2 years ago
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[[bin]]
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name = "cranelift-icache"
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path = "fuzz_targets/cranelift-icache.rs"
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test = false
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doc = false
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