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/*
* Copyright (C) 2016 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.
*/
#include <elf.h>
#include <stdint.h>
#include <unwindstack/Memory.h>
#include <unwindstack/Regs.h>
#include "ArmExidx.h"
#include "ElfInterfaceArm.h"
#include "Machine.h"
namespace unwindstack {
bool ElfInterfaceArm::FindEntry(uint32_t pc, uint64_t* entry_offset) {
if (start_offset_ == 0 || total_entries_ == 0) {
return false;
}
// Need to subtract the load_bias from the pc.
if (pc < load_bias_) {
return false;
}
pc -= load_bias_;
size_t first = 0;
size_t last = total_entries_;
while (first < last) {
size_t current = (first + last) / 2;
uint32_t addr = addrs_[current];
if (addr == 0) {
if (!GetPrel31Addr(start_offset_ + current * 8, &addr)) {
return false;
}
addrs_[current] = addr;
}
if (pc == addr) {
*entry_offset = start_offset_ + current * 8;
return true;
}
if (pc < addr) {
last = current;
} else {
first = current + 1;
}
}
if (last != 0) {
*entry_offset = start_offset_ + (last - 1) * 8;
return true;
}
return false;
}
bool ElfInterfaceArm::GetPrel31Addr(uint32_t offset, uint32_t* addr) {
uint32_t data;
if (!memory_->Read32(offset, &data)) {
return false;
}
// Sign extend the value if necessary.
int32_t value = (static_cast<int32_t>(data) << 1) >> 1;
*addr = offset + value;
return true;
}
#if !defined(PT_ARM_EXIDX)
#define PT_ARM_EXIDX 0x70000001
#endif
bool ElfInterfaceArm::HandleType(uint64_t offset, uint32_t type) {
if (type != PT_ARM_EXIDX) {
return false;
}
Elf32_Phdr phdr;
if (!memory_->ReadField(offset, &phdr, &phdr.p_vaddr, sizeof(phdr.p_vaddr))) {
return true;
}
if (!memory_->ReadField(offset, &phdr, &phdr.p_memsz, sizeof(phdr.p_memsz))) {
return true;
}
// The load_bias_ should always be set by this time.
start_offset_ = phdr.p_vaddr - load_bias_;
total_entries_ = phdr.p_memsz / 8;
return true;
}
bool ElfInterfaceArm::Step(uint64_t pc, Regs* regs, Memory* process_memory) {
// Dwarf unwind information is precise about whether a pc is covered or not,
// but arm unwind information only has ranges of pc. In order to avoid
// incorrectly doing a bad unwind using arm unwind information for a
// different function, always try and unwind with the dwarf information first.
return ElfInterface32::Step(pc, regs, process_memory) || StepExidx(pc, regs, process_memory);
}
bool ElfInterfaceArm::StepExidx(uint64_t pc, Regs* regs, Memory* process_memory) {
RegsArm* regs_arm = reinterpret_cast<RegsArm*>(regs);
uint64_t entry_offset;
if (!FindEntry(pc, &entry_offset)) {
return false;
}
ArmExidx arm(regs_arm, memory_, process_memory);
arm.set_cfa(regs_arm->sp());
if (arm.ExtractEntryData(entry_offset) && arm.Eval()) {
// If the pc was not set, then use the LR registers for the PC.
if (!arm.pc_set()) {
regs_arm->set_pc((*regs_arm)[ARM_REG_LR]);
(*regs_arm)[ARM_REG_PC] = regs_arm->pc();
} else {
regs_arm->set_pc((*regs_arm)[ARM_REG_PC]);
}
regs_arm->set_sp(arm.cfa());
(*regs_arm)[ARM_REG_SP] = regs_arm->sp();
return true;
}
return false;
}
} // namespace unwindstack
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