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04fc29c7e1
The code can be patched if it should not be executed any longer. The code can be now patched at other location than at entry, the requirement is still that patching code does not overwrite an inlined object. Intrinsic methods that do not have a fall through cannot be patched. Review URL: https://codereview.chromium.org//11783066 git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@16897 260f80e4-7a28-3924-810f-c04153c831b5
86 lines
3 KiB
C++
86 lines
3 KiB
C++
// Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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#include "vm/code_patcher.h"
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#include "vm/instructions.h"
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#include "vm/object.h"
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namespace dart {
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static void SwapCode(intptr_t num_bytes, char* a, char* b) {
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for (intptr_t i = 0; i < num_bytes; i++) {
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char tmp = *a;
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*a = *b;
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*b = tmp;
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a++;
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b++;
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}
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}
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// The patch code buffer contains the jmp code which will be inserted at
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// entry point.
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void CodePatcher::PatchEntry(const Code& code) {
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const uword patch_addr = code.GetPcForDeoptId(Isolate::kNoDeoptId,
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PcDescriptors::kEntryPatch);
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JumpPattern jmp_entry(patch_addr);
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ASSERT(!jmp_entry.IsValid());
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const uword patch_buffer = code.GetPatchCodePc();
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ASSERT(patch_buffer != 0);
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JumpPattern jmp_patch(patch_buffer);
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ASSERT(jmp_patch.IsValid());
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const uword jump_target = jmp_patch.TargetAddress();
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SwapCode(jmp_patch.pattern_length_in_bytes(),
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reinterpret_cast<char*>(patch_addr),
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reinterpret_cast<char*>(patch_buffer));
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jmp_entry.SetTargetAddress(jump_target);
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}
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// The entry point is a jmp instruction, the patch code buffer contains
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// original code, the entry point contains the jump instruction.
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void CodePatcher::RestoreEntry(const Code& code) {
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const uword patch_addr = code.GetPcForDeoptId(Isolate::kNoDeoptId,
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PcDescriptors::kEntryPatch);
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JumpPattern jmp_entry(patch_addr);
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ASSERT(jmp_entry.IsValid());
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const uword jump_target = jmp_entry.TargetAddress();
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const uword patch_buffer = code.GetPatchCodePc();
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ASSERT(patch_buffer != 0);
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// 'patch_buffer' contains original entry code.
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JumpPattern jmp_patch(patch_buffer);
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ASSERT(!jmp_patch.IsValid());
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SwapCode(jmp_patch.pattern_length_in_bytes(),
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reinterpret_cast<char*>(patch_addr),
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reinterpret_cast<char*>(patch_buffer));
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ASSERT(jmp_patch.IsValid());
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jmp_patch.SetTargetAddress(jump_target);
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}
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bool CodePatcher::CodeIsPatchable(const Code& code) {
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const uword patch_addr = code.GetPcForDeoptId(Isolate::kNoDeoptId,
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PcDescriptors::kEntryPatch);
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// kEntryPatch may not exist which means the function is not patchable.
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if (patch_addr == 0) {
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return true;
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}
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JumpPattern jmp_entry(patch_addr);
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if (code.Size() < (jmp_entry.pattern_length_in_bytes() * 2)) {
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return false;
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}
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const uword limit = patch_addr + jmp_entry.pattern_length_in_bytes();
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// Check no object stored between patch_addr .. limit.
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for (intptr_t i = 0; i < code.pointer_offsets_length(); i++) {
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const uword obj_start = code.GetPointerOffsetAt(i) + code.EntryPoint();
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const uword obj_end = obj_start + kWordSize;
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if ((obj_start < limit) && (obj_end > patch_addr)) {
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return false;
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}
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}
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return true;
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}
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} // namespace dart
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