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/*
Copyright (C) 2016 - 2016 Evan Teran
evan.teran@gmail.com
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "FeatureDetect.h"
#include "version.h"
#include <cstdint>
#include <fcntl.h>
#include <iomanip>
#include <iostream>
#include <string>
#include <sys/ptrace.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
namespace DebuggerCorePlugin {
namespace feature {
namespace {
// Custom class to work with files, since various wrappers
// appear to be unreliable to check whether writes succeeded
class File {
public:
explicit File(const std::string &filename) {
fd_ = ::open(filename.c_str(), O_RDWR);
success_ = fd_ != -1;
}
ssize_t write(const void *buf, size_t count) {
const ssize_t result = ::write(fd_, buf, count);
success_ = result != -1;
return result;
}
ssize_t read(void *buf, size_t count) {
const ssize_t result = ::read(fd_, buf, count);
success_ = result != -1;
return result;
}
off_t seekp(size_t offset) {
const off_t result = ::lseek(fd_, offset, SEEK_SET);
success_ = result != -1;
return result;
}
~File() {
close(fd_);
}
explicit operator bool() {
return success_;
}
private:
int fd_ = -1;
bool success_ = false;
};
/**
* @brief kill_child
* @param pid
*/
void kill_child(int pid) {
if (kill(pid, SIGKILL) == -1) {
perror("failed to kill child");
}
}
}
/**
* detects whether or not reads/writes through /proc/<pid>/mem work correctly
*
* @brief detect_proc_access
* @param read_broken
* @param write_broken
* @return
*/
bool detect_proc_access(bool *read_broken, bool *write_broken) {
switch (pid_t pid = fork()) {
case 0:
if (ptrace(PTRACE_TRACEME, 0, 0, 0) < 0) {
perror("child: PTRACE_TRACEME failed");
abort();
}
// force a signal
raise(SIGCONT);
for (;;) {
sleep(10);
}
abort();
case -1:
perror("fork");
return false;
default: {
int status;
if (waitpid(pid, &status, __WALL) == -1) {
perror("parent: waitpid failed");
kill_child(pid);
return false;
}
if (!WIFSTOPPED(status) || WSTOPSIG(status) != SIGCONT) {
std::cerr << "unexpected status returned by waitpid: 0x" << std::hex << status << "\n";
kill_child(pid);
return false;
}
File file("/proc/" + std::to_string(pid) + "/mem");
if (!file) {
perror("failed to open memory file");
kill_child(pid);
return false;
}
const auto pageAlignMask = ~(sysconf(_SC_PAGESIZE) - 1);
const auto addr = reinterpret_cast<uintptr_t>(&edb::version) & pageAlignMask;
file.seekp(addr);
if (!file) {
perror("failed to seek to address to read");
kill_child(pid);
return false;
}
int buf = 0x12345678;
{
file.read(&buf, sizeof(buf));
if (!file) {
*read_broken = true;
*write_broken = true;
kill_child(pid);
return false;
}
}
file.seekp(addr);
if (!file) {
perror("failed to seek to address to write");
kill_child(pid);
return false;
}
{
file.write(&buf, sizeof(buf));
if (!file) {
*read_broken = false;
*write_broken = true;
} else {
*read_broken = false;
*write_broken = false;
}
}
kill_child(pid);
return true;
}
}
}
}
}
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