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/*
* Copyright (C) 2017 The Android Open Source Project
*
* 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.
*/
#ifndef ART_RUNTIME_INTERPRETER_CFI_ASM_SUPPORT_H_
#define ART_RUNTIME_INTERPRETER_CFI_ASM_SUPPORT_H_
#if !defined(__APPLE__)
/*
* Define the DEX PC (memory address of the currently interpreted bytecode)
* within the CFI stream of the current function (stored in .eh_frame).
* This allows libunwind to detect that the frame is in the interpreter,
* and to resolve the memory address into human readable Java method name.
* The CFI instruction is recognised by the magic bytes in the expression
* (we push magic "DEX1" constant on the DWARF stack and drop it again).
*
* As with any other CFI opcode, the expression needs to be associated with
* a register. Any caller-save register will do as those are unused in CFI.
* Better solution would be to store the expression in Android-specific
* DWARF register (CFI registers don't have to correspond to real hardware
* registers), however, gdb handles any unknown registers very poorly.
* Similarly, we could also use some of the user-defined opcodes defined
* in the DWARF specification, but gdb doesn't support those either.
*
* The DEX PC is generally advanced in the middle of the bytecode handler,
* which will result in the reported DEX PC to be off by an instruction.
* Therefore the macro allows adding/subtracting an offset to compensate.
* TODO: Add the offsets to handlers to get line-accurate DEX PC reporting.
*/
#define CFI_DEFINE_DEX_PC_WITH_OFFSET(tmpReg, dexReg, dexOffset) .cfi_escape \
0x16 /* DW_CFA_val_expression */, tmpReg, 0x09 /* size */, \
0x0c /* DW_OP_const4u */, 0x44, 0x45, 0x58, 0x31, /* magic = "DEX1" */ \
0x13 /* DW_OP_drop */, \
0x92 /* DW_OP_bregx */, dexReg, (dexOffset & 0x7F) /* 1-byte SLEB128 */
#define CFI_DEFINE_CFA_DEREF(reg, offset, size) .cfi_escape \
0x0f /* DW_CFA_expression */, 6 /* size */, \
0x92 /* bregx */, reg, (offset & 0x7F), \
0x06 /* DW_OP_DEREF */, \
0x23 /* DW_OP_plus_uconst */, size
#else
// Mac OS doesn't like cfi_* directives.
#define CFI_DEFINE_DEX_PC_WITH_OFFSET(tmpReg, dexReg, dexOffset)
#define CFI_DEFINE_CFA_DEREF(reg, offset)
#endif
#endif // ART_RUNTIME_INTERPRETER_CFI_ASM_SUPPORT_H_
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