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Unified Diff: src/wasm/module-decoder.cc

Issue 2055783002: [wasm] Add functionality to decode a function offset table (Closed) Base URL: https://chromium.googlesource.com/v8/v8.git@print-ast-to-ostream
Patch Set: fix nit Created 4 years, 6 months ago
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Index: src/wasm/module-decoder.cc
diff --git a/src/wasm/module-decoder.cc b/src/wasm/module-decoder.cc
index 48f59cefa82bdf1d293da3eb529d4244e7dc2485..c753c63983267dff5182bd3306d43f47ebd4b84d 100644
--- a/src/wasm/module-decoder.cc
+++ b/src/wasm/module-decoder.cc
@@ -25,6 +25,8 @@ namespace wasm {
#define TRACE(...)
#endif
+namespace {
+
// The main logic for decoding the bytes of a module.
class ModuleDecoder : public Decoder {
public:
@@ -719,6 +721,45 @@ class FunctionError : public FunctionResult {
}
};
+Vector<const byte> FindSection(const byte* module_start, const byte* module_end,
+ WasmSection::Code code) {
+ Decoder decoder(module_start, module_end);
+
+ uint32_t magic_word = decoder.consume_u32("wasm magic");
+ if (magic_word != kWasmMagic) decoder.error("wrong magic word");
+
+ uint32_t magic_version = decoder.consume_u32("wasm version");
+ if (magic_version != kWasmVersion) decoder.error("wrong wasm version");
+
+ while (decoder.more() && decoder.ok()) {
+ // Read the section name.
+ int string_leb_length = 0;
+ uint32_t string_length =
+ decoder.consume_u32v(&string_leb_length, "section name length");
+ const byte* section_name_start = decoder.pc();
+ decoder.consume_bytes(string_length);
+ if (decoder.failed()) break;
+
+ WasmSection::Code section =
+ WasmSection::lookup(section_name_start, string_length);
+
+ // Read and check the section size.
+ int section_leb_length = 0;
+ uint32_t section_length =
+ decoder.consume_u32v(&section_leb_length, "section length");
+
+ const byte* section_start = decoder.pc();
+ decoder.consume_bytes(section_length);
+ if (section == code && decoder.ok()) {
+ return Vector<const uint8_t>(section_start, section_length);
+ }
+ }
+
+ return Vector<const uint8_t>();
+}
+
+} // namespace
+
ModuleResult DecodeWasmModule(Isolate* isolate, Zone* zone,
const byte* module_start, const byte* module_end,
bool verify_functions, ModuleOrigin origin) {
@@ -762,6 +803,34 @@ FunctionResult DecodeWasmFunction(Isolate* isolate, Zone* zone,
ModuleDecoder decoder(zone, function_start, function_end, kWasmOrigin);
return decoder.DecodeSingleFunction(module_env, function);
}
+
+FunctionOffsetsResult DecodeWasmFunctionOffsets(const byte* module_start,
+ const byte* module_end) {
+ Vector<const byte> code_section =
+ FindSection(module_start, module_end, WasmSection::Code::FunctionBodies);
+ Decoder decoder(code_section.start(), code_section.end());
+ if (!code_section.start()) decoder.error("no code section");
+
+ int length;
+ uint32_t functions_count = decoder.consume_u32v(&length, "functions count");
+ FunctionOffsets table;
+ // Take care of invalid input here.
+ if (functions_count < static_cast<unsigned>(code_section.length()) / 2)
+ table.reserve(functions_count);
+ int section_offset = static_cast<int>(code_section.start() - module_start);
+ DCHECK_LE(0, section_offset);
+ for (uint32_t i = 0; i < functions_count && decoder.ok(); i++) {
+ uint32_t size = decoder.consume_u32v(&length, "body size");
+ int offset = static_cast<int>(section_offset + decoder.pc_offset());
+ table.push_back(std::make_pair(offset, static_cast<int>(size)));
+ DCHECK(table.back().first >= 0 && table.back().second >= 0);
+ decoder.consume_bytes(size);
+ }
+ if (decoder.more()) decoder.error("unexpected additional bytes");
+
+ return decoder.toResult(std::move(table));
+}
+
} // namespace wasm
} // namespace internal
} // namespace v8
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