1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
use super::operators::{Frame, OperatorValidator, OperatorValidatorAllocations};
use crate::{BinaryReader, Result, ValType, VisitOperator};
use crate::{FunctionBody, Operator, WasmFeatures, WasmModuleResources};

/// Resources necessary to perform validation of a function.
///
/// This structure is created by
/// [`Validator::code_section_entry`](crate::Validator::code_section_entry) and
/// is created per-function in a WebAssembly module. This structure is suitable
/// for sending to other threads while the original
/// [`Validator`](crate::Validator) continues processing other functions.
pub struct FuncToValidate<T> {
    resources: T,
    index: u32,
    ty: u32,
    features: WasmFeatures,
}

impl<T: WasmModuleResources> FuncToValidate<T> {
    /// Creates a new function to validate which will have the specified
    /// configuration parameters:
    ///
    /// * `index` - the core wasm function index being validated
    /// * `ty` - the core wasm type index of the function being validated,
    ///   defining the results and parameters to the function.
    /// * `resources` - metadata and type information about the module that
    ///   this function is validated within.
    /// * `features` - enabled WebAssembly features.
    pub fn new(index: u32, ty: u32, resources: T, features: &WasmFeatures) -> FuncToValidate<T> {
        FuncToValidate {
            resources,
            index,
            ty,
            features: *features,
        }
    }

    /// Converts this [`FuncToValidate`] into a [`FuncValidator`] using the
    /// `allocs` provided.
    ///
    /// This method, in conjunction with [`FuncValidator::into_allocations`],
    /// provides a means to reuse allocations across validation of each
    /// individual function. Note that it is also sufficient to call this
    /// method with `Default::default()` if no prior allocations are
    /// available.
    ///
    /// # Panics
    ///
    /// If a `FuncToValidate` was created with an invalid `ty` index then this
    /// function will panic.
    pub fn into_validator(self, allocs: FuncValidatorAllocations) -> FuncValidator<T> {
        let FuncToValidate {
            resources,
            index,
            ty,
            features,
        } = self;
        let validator =
            OperatorValidator::new_func(ty, 0, &features, &resources, allocs.0).unwrap();
        FuncValidator {
            validator,
            resources,
            index,
        }
    }
}

/// Validation context for a WebAssembly function.
///
/// This is a finalized validator which is ready to process a [`FunctionBody`].
/// This is created from the [`FuncToValidate::into_validator`] method.
pub struct FuncValidator<T> {
    validator: OperatorValidator,
    resources: T,
    index: u32,
}

/// External handle to the internal allocations used during function validation.
///
/// This is created with either the `Default` implementation or with
/// [`FuncValidator::into_allocations`]. It is then passed as an argument to
/// [`FuncToValidate::into_validator`] to provide a means of reusing allocations
/// between each function.
#[derive(Default)]
pub struct FuncValidatorAllocations(OperatorValidatorAllocations);

impl<T: WasmModuleResources> FuncValidator<T> {
    /// Convenience function to validate an entire function's body.
    ///
    /// You may not end up using this in final implementations because you'll
    /// often want to interleave validation with parsing.
    pub fn validate(&mut self, body: &FunctionBody<'_>) -> Result<()> {
        let mut reader = body.get_binary_reader();
        self.read_locals(&mut reader)?;
        reader.allow_memarg64(self.validator.features.memory64);
        while !reader.eof() {
            reader.visit_operator(self)??;
        }
        self.finish(reader.original_position())
    }

    /// Reads the local definitions from the given `BinaryReader`, often sourced
    /// from a `FunctionBody`.
    ///
    /// This function will automatically advance the `BinaryReader` forward,
    /// leaving reading operators up to the caller afterwards.
    pub fn read_locals(&mut self, reader: &mut BinaryReader<'_>) -> Result<()> {
        for _ in 0..reader.read_var_u32()? {
            let offset = reader.original_position();
            let cnt = reader.read_var_u32()?;
            let ty = reader.read_val_type()?;
            self.define_locals(offset, cnt, ty)?;
        }
        Ok(())
    }

    /// Defines locals into this validator.
    ///
    /// This should be used if the application is already reading local
    /// definitions and there's no need to re-parse the function again.
    pub fn define_locals(&mut self, offset: usize, count: u32, ty: ValType) -> Result<()> {
        self.validator.define_locals(offset, count, ty)
    }

    /// Validates the next operator in a function.
    ///
    /// This functions is expected to be called once-per-operator in a
    /// WebAssembly function. Each operator's offset in the original binary and
    /// the operator itself are passed to this function to provide more useful
    /// error messages.
    pub fn op(&mut self, offset: usize, operator: &Operator<'_>) -> Result<()> {
        self.validator
            .with_resources(&self.resources)
            .visit_operator(offset, operator)
    }

    /// Function that must be called after the last opcode has been processed.
    ///
    /// This will validate that the function was properly terminated with the
    /// `end` opcode. If this function is not called then the function will not
    /// be properly validated.
    ///
    /// The `offset` provided to this function will be used as a position for an
    /// error if validation fails.
    pub fn finish(&mut self, offset: usize) -> Result<()> {
        self.validator.finish(offset)
    }

    /// Returns the underlying module resources that this validator is using.
    pub fn resources(&self) -> &T {
        &self.resources
    }

    /// The index of the function within the module's function index space that
    /// is being validated.
    pub fn index(&self) -> u32 {
        self.index
    }

    /// Returns the number of defined local variables in the function.
    pub fn len_locals(&self) -> u32 {
        self.validator.locals.len_locals()
    }

    /// Returns the type of the local variable at the given `index` if any.
    pub fn get_local_type(&self, index: u32) -> Option<ValType> {
        self.validator.locals.get(index)
    }

    /// Get the current height of the operand stack.
    ///
    /// This returns the height of the whole operand stack for this function,
    /// not just for the current control frame.
    pub fn operand_stack_height(&self) -> u32 {
        self.validator.operand_stack_height() as u32
    }

    /// Returns the optional value type of the value operand at the given
    /// `depth` from the top of the operand stack.
    ///
    /// - Returns `None` if the `depth` is out of bounds.
    /// - Returns `Some(None)` if there is a value with unknown type
    /// at the given `depth`.
    ///
    /// # Note
    ///
    /// A `depth` of 0 will refer to the last operand on the stack.
    pub fn get_operand_type(&self, depth: usize) -> Option<Option<ValType>> {
        self.validator.peek_operand_at(depth)
    }

    /// Returns the number of frames on the control flow stack.
    ///
    /// This returns the height of the whole control stack for this function,
    /// not just for the current control frame.
    pub fn control_stack_height(&self) -> u32 {
        self.validator.control_stack_height() as u32
    }

    /// Returns a shared reference to the control flow [`Frame`] of the
    /// control flow stack at the given `depth` if any.
    ///
    /// Returns `None` if the `depth` is out of bounds.
    ///
    /// # Note
    ///
    /// A `depth` of 0 will refer to the last frame on the stack.
    pub fn get_control_frame(&self, depth: usize) -> Option<&Frame> {
        self.validator.get_frame(depth)
    }

    /// Consumes this validator and returns the underlying allocations that
    /// were used during the validation process.
    ///
    /// The returned value here can be paired with
    /// [`FuncToValidate::into_validator`] to reuse the allocations already
    /// created by this validator.
    pub fn into_allocations(self) -> FuncValidatorAllocations {
        FuncValidatorAllocations(self.validator.into_allocations())
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::WasmFuncType;

    struct EmptyResources;

    impl WasmModuleResources for EmptyResources {
        type FuncType = EmptyFuncType;

        fn table_at(&self, _at: u32) -> Option<crate::TableType> {
            todo!()
        }
        fn memory_at(&self, _at: u32) -> Option<crate::MemoryType> {
            todo!()
        }
        fn tag_at(&self, _at: u32) -> Option<&Self::FuncType> {
            todo!()
        }
        fn global_at(&self, _at: u32) -> Option<crate::GlobalType> {
            todo!()
        }
        fn func_type_at(&self, _type_idx: u32) -> Option<&Self::FuncType> {
            Some(&EmptyFuncType)
        }
        fn type_of_function(&self, _func_idx: u32) -> Option<&Self::FuncType> {
            todo!()
        }
        fn element_type_at(&self, _at: u32) -> Option<ValType> {
            todo!()
        }
        fn element_count(&self) -> u32 {
            todo!()
        }
        fn data_count(&self) -> Option<u32> {
            todo!()
        }
        fn is_function_referenced(&self, _idx: u32) -> bool {
            todo!()
        }
    }

    struct EmptyFuncType;

    impl WasmFuncType for EmptyFuncType {
        fn len_inputs(&self) -> usize {
            0
        }
        fn len_outputs(&self) -> usize {
            0
        }
        fn input_at(&self, _at: u32) -> Option<ValType> {
            todo!()
        }
        fn output_at(&self, _at: u32) -> Option<ValType> {
            todo!()
        }
    }

    #[test]
    fn operand_stack_height() {
        let mut v = FuncToValidate::new(0, 0, EmptyResources, &Default::default())
            .into_validator(Default::default());

        // Initially zero values on the stack.
        assert_eq!(v.operand_stack_height(), 0);

        // Pushing a constant value makes use have one value on the stack.
        assert!(v.op(0, &Operator::I32Const { value: 0 }).is_ok());
        assert_eq!(v.operand_stack_height(), 1);

        // Entering a new control block does not affect the stack height.
        assert!(v
            .op(
                1,
                &Operator::Block {
                    ty: crate::BlockType::Empty
                }
            )
            .is_ok());
        assert_eq!(v.operand_stack_height(), 1);

        // Pushing another constant value makes use have two values on the stack.
        assert!(v.op(2, &Operator::I32Const { value: 99 }).is_ok());
        assert_eq!(v.operand_stack_height(), 2);
    }
}

macro_rules! define_visit_operator {
    ($(@$proposal:ident $op:ident $({ $($arg:ident: $argty:ty),* })? => $visit:ident)*) => {
        $(
            fn $visit(&mut self, offset: usize $($(,$arg: $argty)*)?) -> Result<()> {
                self.validator.with_resources(&self.resources)
                    .$visit(offset $($(,$arg)*)?)
            }
        )*
    }
}

#[allow(unused_variables)]
impl<'a, T> VisitOperator<'a> for FuncValidator<T>
where
    T: WasmModuleResources,
{
    type Output = Result<()>;

    for_each_operator!(define_visit_operator);
}