1 /*
2 * Copyright (C) 2017 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include "slicer/tryblocks_encoder.h"
18
19 #include "slicer/chronometer.h"
20 #include "slicer/common.h"
21
22 namespace lir {
23
Visit(TryBlockEnd * try_end)24 bool TryBlocksEncoder::Visit(TryBlockEnd* try_end) {
25 const dex::u4 begin_offset = try_end->try_begin->offset;
26 const dex::u4 end_offset = try_end->offset;
27 SLICER_CHECK_GT(end_offset, begin_offset);
28 SLICER_CHECK_LT(end_offset - begin_offset, (1 << 16));
29
30 // generate the "try_item"
31 dex::TryBlock try_block = {};
32 try_block.start_addr = begin_offset;
33 try_block.insn_count = end_offset - begin_offset;
34 try_block.handler_off = handlers_.size();
35 tries_.Push(try_block);
36
37 // generate the "encoded_catch_handler"
38 dex::s4 catch_count = try_end->handlers.size();
39 handlers_.PushSLeb128(try_end->catch_all ? -catch_count : catch_count);
40 for (int catch_index = 0; catch_index < catch_count; ++catch_index) {
41 const CatchHandler& handler = try_end->handlers[catch_index];
42 // type_idx
43 handlers_.PushULeb128(handler.ir_type->orig_index);
44 // address
45 SLICER_CHECK_NE(handler.label->offset, kInvalidOffset);
46 handlers_.PushULeb128(handler.label->offset);
47 }
48 if (try_end->catch_all != nullptr) {
49 // address
50 SLICER_CHECK_NE(try_end->catch_all->offset, kInvalidOffset);
51 handlers_.PushULeb128(try_end->catch_all->offset);
52 }
53
54 return true;
55 }
56
Encode(ir::Code * ir_code,std::shared_ptr<ir::DexFile> dex_ir)57 void TryBlocksEncoder::Encode(ir::Code* ir_code, std::shared_ptr<ir::DexFile> dex_ir) {
58 SLICER_CHECK(handlers_.empty());
59 SLICER_CHECK(tries_.empty());
60
61 // first, count the number of try blocks
62 struct TryBlockEndVisitor : public Visitor {
63 int tries_count = 0;
64 bool Visit(TryBlockEnd* try_end) override {
65 ++tries_count;
66 return true;
67 }
68 };
69 TryBlockEndVisitor visitor;
70 for (auto instr : instructions_) {
71 instr->Accept(&visitor);
72 }
73 int tries_count = visitor.tries_count;
74 SLICER_CHECK_LT(tries_count, (1 << 16));
75
76 // no try blocks?
77 if (tries_count == 0) {
78 ir_code->try_blocks = {};
79 ir_code->catch_handlers = {};
80 return;
81 }
82
83 // "encoded_catch_handler_list.size"
84 handlers_.PushULeb128(tries_count);
85
86 // generate the try blocks & encoded catch handlers
87 //
88 // NOTE: try_item[tries_count] :
89 // "Elements of the array must be non-overlapping in range and
90 // in order from low to high address. This element is only present
91 // if tries_size is non-zero"
92 //
93 // NOTE: we're not de-duplicating catch_handlers
94 // (generate one catch_handler for each try block)
95 //
96 for (auto instr : instructions_) {
97 instr->Accept(this);
98 }
99 SLICER_CHECK(!tries_.empty());
100 SLICER_CHECK(!handlers_.empty());
101 tries_.Seal(1);
102 handlers_.Seal(1);
103
104 // update ir::Code
105 auto tries_ptr = tries_.ptr<const dex::TryBlock>(0);
106 ir_code->try_blocks = slicer::ArrayView<const dex::TryBlock>(tries_ptr, tries_count);
107 ir_code->catch_handlers = slicer::MemView(handlers_.data(), handlers_.size());
108
109 // attach the generated try/catch blocks to the dex IR
110 dex_ir->AttachBuffer(std::move(tries_));
111 dex_ir->AttachBuffer(std::move(handlers_));
112 }
113
114 } // namespace lir
115