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/*
* Copyright (C) 2012 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <ctype.h>
#include <elf.h>
#include <inttypes.h>
#include <link.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <vector>
#include "MapData.h"
// Format of /proc/<PID>/maps:
// 6f000000-6f01e000 rwxp 00000000 00:0c 16389419 /system/lib/libcomposer.so
static MapEntry* parse_line(char* line) {
uintptr_t start;
uintptr_t end;
uintptr_t offset;
int flags;
char permissions[5];
int name_pos;
if (sscanf(line, "%" PRIxPTR "-%" PRIxPTR " %4s %" PRIxPTR " %*x:%*x %*d %n", &start, &end,
permissions, &offset, &name_pos) < 2) {
return nullptr;
}
const char* name = line + name_pos;
size_t name_len = strlen(name);
if (name_len && name[name_len - 1] == '\n') {
name_len -= 1;
}
flags = 0;
if (permissions[0] == 'r') {
flags |= PROT_READ;
}
if (permissions[2] == 'x') {
flags |= PROT_EXEC;
}
MapEntry* entry = new MapEntry(start, end, offset, name, name_len, flags);
if (!(flags & PROT_READ)) {
// Any unreadable map will just get a zero load bias.
entry->load_bias = 0;
entry->init = true;
entry->valid = false;
}
return entry;
}
template <typename T>
static inline bool get_val(MapEntry* entry, uintptr_t addr, T* store) {
if (!(entry->flags & PROT_READ) || addr < entry->start || addr + sizeof(T) > entry->end) {
return false;
}
// Make sure the address is aligned properly.
if (addr & (sizeof(T) - 1)) {
return false;
}
*store = *reinterpret_cast<T*>(addr);
return true;
}
static bool valid_elf(MapEntry* entry) {
uintptr_t addr = entry->start;
uintptr_t end;
if (__builtin_add_overflow(addr, SELFMAG, &end) || end >= entry->end) {
return false;
}
return memcmp(reinterpret_cast<void*>(addr), ELFMAG, SELFMAG) == 0;
}
static void read_loadbias(MapEntry* entry) {
entry->load_bias = 0;
uintptr_t addr = entry->start;
ElfW(Ehdr) ehdr;
if (!get_val<ElfW(Half)>(entry, addr + offsetof(ElfW(Ehdr), e_phnum), &ehdr.e_phnum)) {
return;
}
if (!get_val<ElfW(Off)>(entry, addr + offsetof(ElfW(Ehdr), e_phoff), &ehdr.e_phoff)) {
return;
}
addr += ehdr.e_phoff;
for (size_t i = 0; i < ehdr.e_phnum; i++) {
ElfW(Phdr) phdr;
if (!get_val<ElfW(Word)>(entry, addr + offsetof(ElfW(Phdr), p_type), &phdr.p_type)) {
return;
}
if (!get_val<ElfW(Off)>(entry, addr + offsetof(ElfW(Phdr), p_offset), &phdr.p_offset)) {
return;
}
if (phdr.p_type == PT_LOAD && phdr.p_offset == entry->offset) {
if (!get_val<ElfW(Addr)>(entry, addr + offsetof(ElfW(Phdr), p_vaddr), &phdr.p_vaddr)) {
return;
}
entry->load_bias = phdr.p_vaddr;
return;
}
addr += sizeof(phdr);
}
}
static void inline init(MapEntry* entry) {
if (entry->init) {
return;
}
entry->init = true;
if (valid_elf(entry)) {
entry->valid = true;
read_loadbias(entry);
}
}
bool MapData::ReadMaps() {
FILE* fp = fopen("/proc/self/maps", "re");
if (fp == nullptr) {
return false;
}
std::vector<char> buffer(1024);
while (fgets(buffer.data(), buffer.size(), fp) != nullptr) {
MapEntry* entry = parse_line(buffer.data());
if (entry == nullptr) {
fclose(fp);
return false;
}
auto it = entries_.find(entry);
if (it == entries_.end()) {
entries_.insert(entry);
} else {
delete entry;
}
}
fclose(fp);
return true;
}
MapData::~MapData() {
for (auto* entry : entries_) {
delete entry;
}
entries_.clear();
}
// Find the containing map info for the PC.
const MapEntry* MapData::find(uintptr_t pc, uintptr_t* rel_pc) {
MapEntry pc_entry(pc);
std::lock_guard<std::mutex> lock(m_);
auto it = entries_.find(&pc_entry);
if (it == entries_.end()) {
ReadMaps();
}
it = entries_.find(&pc_entry);
if (it == entries_.end()) {
return nullptr;
}
MapEntry* entry = *it;
init(entry);
if (rel_pc != nullptr) {
// Need to check to see if this is a read-execute map and the read-only
// map is the previous one.
if (!entry->valid && it != entries_.begin()) {
MapEntry* prev_entry = *--it;
if (prev_entry->flags == PROT_READ && prev_entry->offset < entry->offset &&
prev_entry->name == entry->name) {
init(prev_entry);
if (prev_entry->valid) {
entry->elf_start_offset = prev_entry->offset;
*rel_pc = pc - entry->start + entry->offset + prev_entry->load_bias;
return entry;
}
}
}
*rel_pc = pc - entry->start + entry->load_bias;
}
return entry;
}
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