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/*
* Copyright 2017 WebAssembly Community Group participants
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
//
// Instruments the build with code to intercept all memory reads and writes.
// This can be useful in building tools that analyze memory access behaviour.
//
// The instrumentation is performed by calling an FFI with an ID for each
// memory access site. Load / store IDs share the same index space. The
// instrumentation wraps the evaluation of the address operand, therefore
// it executes before the load / store is executed. Note that Instrumentation
// code must return tha address argument.
//
// Loads: load(id, bytes, offset, address) => address
//
// Before:
// (i32.load8_s align=1 offset=2 (i32.const 3))
//
// After:
// (i32.load8_s align=1 offset=2
// (call $load
// (i32.const n) // ID
// (i32.const 1) // bytes
// (i32.const 2) // offset
// (i32.const 3) // address
// )
// )
//
// Stores: store(id, bytes, offset, address) => address
//
// Before:
// (i32.store8 align=1 offset=2 (i32.const 3) (i32.const 4))
//
// After:
// (i32.store16 align=1 offset=2
// (call $store
// (i32.const n) // ID
// (i32.const 1) // bytes
// (i32.const 2) // offset
// (i32.const 3) // address
// )
// (i32.const 4)
// )
#include <wasm.h>
#include <wasm-builder.h>
#include <pass.h>
#include "shared-constants.h"
#include "asmjs/shared-constants.h"
#include "asm_v_wasm.h"
namespace wasm {
Name load("load");
Name store("store");
// TODO: Add support for atomicRMW/cmpxchg
struct InstrumentMemory : public WalkerPass<PostWalker<InstrumentMemory>> {
void visitLoad(Load* curr) {
makeLoadCall(curr);
}
void visitStore(Store* curr) {
makeStoreCall(curr);
}
void addImport(Module *curr, Name name, std::string sig) {
auto import = new Import;
import->name = name;
import->module = INSTRUMENT;
import->base = name;
import->functionType = ensureFunctionType(sig, curr)->name;
import->kind = ExternalKind::Function;
curr->addImport(import);
}
void visitModule(Module *curr) {
addImport(curr, load, "iiiii");
addImport(curr, store, "iiiii");
}
private:
std::atomic<Index> id;
Expression* makeLoadCall(Load* curr) {
Builder builder(*getModule());
curr->ptr = builder.makeCallImport(load,
{ builder.makeConst(Literal(int32_t(id.fetch_add(1)))),
builder.makeConst(Literal(int32_t(curr->bytes))),
builder.makeConst(Literal(int32_t(curr->offset.addr))),
curr->ptr},
i32
);
return curr;
}
Expression* makeStoreCall(Store* curr) {
Builder builder(*getModule());
curr->ptr = builder.makeCallImport(store,
{ builder.makeConst(Literal(int32_t(id.fetch_add(1)))),
builder.makeConst(Literal(int32_t(curr->bytes))),
builder.makeConst(Literal(int32_t(curr->offset.addr))),
curr->ptr },
i32
);
return curr;
}
};
Pass *createInstrumentMemoryPass() {
return new InstrumentMemory();
}
} // namespace wasm
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