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/*
* Copyright (C) 2013 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 <errno.h>
#include <stdint.h>
#include <string.h>
#include <sys/param.h>
#include <sys/ptrace.h>
#include <sys/types.h>
#include <ucontext.h>
#include <unistd.h>
#include <backtrace/Backtrace.h>
#include <backtrace/BacktraceMap.h>
#include "BacktraceLog.h"
#include "BacktracePtrace.h"
#if !defined(__APPLE__)
static bool PtraceRead(pid_t tid, uint64_t addr, word_t* out_value) {
// ptrace() returns -1 and sets errno when the operation fails.
// To disambiguate -1 from a valid result, we clear errno beforehand.
errno = 0;
*out_value = ptrace(PTRACE_PEEKTEXT, tid, reinterpret_cast<void*>(addr), nullptr);
if (*out_value == static_cast<word_t>(-1) && errno) {
return false;
}
return true;
}
#endif
bool BacktracePtrace::ReadWord(uint64_t ptr, word_t* out_value) {
#if defined(__APPLE__)
BACK_LOGW("MacOS does not support reading from another pid.");
return false;
#else
if (!VerifyReadWordArgs(ptr, out_value)) {
return false;
}
backtrace_map_t map;
FillInMap(ptr, &map);
if (!BacktraceMap::IsValid(map) || !(map.flags & PROT_READ)) {
return false;
}
return PtraceRead(Tid(), ptr, out_value);
#endif
}
size_t BacktracePtrace::Read(uint64_t addr, uint8_t* buffer, size_t bytes) {
#if defined(__APPLE__)
BACK_LOGW("MacOS does not support reading from another pid.");
return 0;
#else
backtrace_map_t map;
FillInMap(addr, &map);
if (!BacktraceMap::IsValid(map) || !(map.flags & PROT_READ)) {
return 0;
}
bytes = MIN(map.end - addr, bytes);
size_t bytes_read = 0;
word_t data_word;
size_t align_bytes = addr & (sizeof(word_t) - 1);
if (align_bytes != 0) {
if (!PtraceRead(Tid(), addr & ~(sizeof(word_t) - 1), &data_word)) {
return 0;
}
size_t copy_bytes = MIN(sizeof(word_t) - align_bytes, bytes);
memcpy(buffer, reinterpret_cast<uint8_t*>(&data_word) + align_bytes, copy_bytes);
addr += copy_bytes;
buffer += copy_bytes;
bytes -= copy_bytes;
bytes_read += copy_bytes;
}
size_t num_words = bytes / sizeof(word_t);
for (size_t i = 0; i < num_words; i++) {
if (!PtraceRead(Tid(), addr, &data_word)) {
return bytes_read;
}
memcpy(buffer, &data_word, sizeof(word_t));
buffer += sizeof(word_t);
addr += sizeof(word_t);
bytes_read += sizeof(word_t);
}
size_t left_over = bytes & (sizeof(word_t) - 1);
if (left_over) {
if (!PtraceRead(Tid(), addr, &data_word)) {
return bytes_read;
}
memcpy(buffer, &data_word, left_over);
bytes_read += left_over;
}
return bytes_read;
#endif
}
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