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platform_system_core/adb/shell_service.cpp
Elliott Hughes c15b17f1ac adb shell SIGWINCH support. 
Bug: http://b/19734542
Change-Id: Ic9404a132cb9c42cb6a378bcd4b3dea9188d0a44
2015-11-04 10:45:11 -08:00

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/*
* Copyright (C) 2015 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.
*/
// Functionality for launching and managing shell subprocesses.
//
// There are two types of subprocesses, PTY or raw. PTY is typically used for
// an interactive session, raw for non-interactive. There are also two methods
// of communication with the subprocess, passing raw data or using a simple
// protocol to wrap packets. The protocol allows separating stdout/stderr and
// passing the exit code back, but is not backwards compatible.
// ----------------+--------------------------------------
// Type Protocol | Exit code? Separate stdout/stderr?
// ----------------+--------------------------------------
// PTY No | No No
// Raw No | No No
// PTY Yes | Yes No
// Raw Yes | Yes Yes
// ----------------+--------------------------------------
//
// Non-protocol subprocesses work by passing subprocess stdin/out/err through
// a single pipe which is registered with a local socket in adbd. The local
// socket uses the fdevent loop to pass raw data between this pipe and the
// transport, which then passes data back to the adb client. Cleanup is done by
// waiting in a separate thread for the subprocesses to exit and then signaling
// a separate fdevent to close out the local socket from the main loop.
//
// ------------------+-------------------------+------------------------------
// Subprocess | adbd subprocess thread | adbd main fdevent loop
// ------------------+-------------------------+------------------------------
// | |
// stdin/out/err <-----------------------------> LocalSocket
// | | |
// | | Block on exit |
// | | * |
// v | * |
// Exit ---> Unblock |
// | | |
// | v |
// | Notify shell exit FD ---> Close LocalSocket
// ------------------+-------------------------+------------------------------
//
// The protocol requires the thread to intercept stdin/out/err in order to
// wrap/unwrap data with shell protocol packets.
//
// ------------------+-------------------------+------------------------------
// Subprocess | adbd subprocess thread | adbd main fdevent loop
// ------------------+-------------------------+------------------------------
// | |
// stdin/out <---> Protocol <---> LocalSocket
// stderr ---> Protocol ---> LocalSocket
// | | |
// v | |
// Exit ---> Exit code protocol ---> LocalSocket
// | | |
// | v |
// | Notify shell exit FD ---> Close LocalSocket
// ------------------+-------------------------+------------------------------
//
// An alternate approach is to put the protocol wrapping/unwrapping in the main
// fdevent loop, which has the advantage of being able to re-use the existing
// select() code for handling data streams. However, implementation turned out
// to be more complex due to partial reads and non-blocking I/O so this model
// was chosen instead.
#define TRACE_TAG SHELL
#include "sysdeps.h"
#include "shell_service.h"
#include <errno.h>
#include <pty.h>
#include <pwd.h>
#include <sys/select.h>
#include <termios.h>
#include <memory>
#include <base/logging.h>
#include <base/stringprintf.h>
#include <paths.h>
#include "adb.h"
#include "adb_io.h"
#include "adb_trace.h"
#include "adb_utils.h"
namespace {
void init_subproc_child()
{
setsid();
// Set OOM score adjustment to prevent killing
int fd = adb_open("/proc/self/oom_score_adj", O_WRONLY | O_CLOEXEC);
if (fd >= 0) {
adb_write(fd, "0", 1);
adb_close(fd);
} else {
D("adb: unable to update oom_score_adj");
}
}
// Reads from |fd| until close or failure.
std::string ReadAll(int fd) {
char buffer[512];
std::string received;
while (1) {
int bytes = adb_read(fd, buffer, sizeof(buffer));
if (bytes <= 0) {
break;
}
received.append(buffer, bytes);
}
return received;
}
// Helper to automatically close an FD when it goes out of scope.
class ScopedFd {
public:
ScopedFd() {}
~ScopedFd() { Reset(); }
void Reset(int fd=-1) {
if (fd != fd_) {
if (valid()) {
adb_close(fd_);
}
fd_ = fd;
}
}
int Release() {
int temp = fd_;
fd_ = -1;
return temp;
}
bool valid() const { return fd_ >= 0; }
int fd() const { return fd_; }
private:
int fd_ = -1;
DISALLOW_COPY_AND_ASSIGN(ScopedFd);
};
// Creates a socketpair and saves the endpoints to |fd1| and |fd2|.
bool CreateSocketpair(ScopedFd* fd1, ScopedFd* fd2) {
int sockets[2];
if (adb_socketpair(sockets) < 0) {
PLOG(ERROR) << "cannot create socket pair";
return false;
}
fd1->Reset(sockets[0]);
fd2->Reset(sockets[1]);
return true;
}
class Subprocess {
public:
Subprocess(const std::string& command, SubprocessType type,
SubprocessProtocol protocol);
~Subprocess();
const std::string& command() const { return command_; }
bool is_interactive() const { return command_.empty(); }
int local_socket_fd() const { return local_socket_sfd_.fd(); }
pid_t pid() const { return pid_; }
// Sets up FDs, forks a subprocess, starts the subprocess manager thread,
// and exec's the child. Returns false on failure.
bool ForkAndExec();
private:
// Opens the file at |pts_name|.
int OpenPtyChildFd(const char* pts_name, ScopedFd* error_sfd);
static void* ThreadHandler(void* userdata);
void PassDataStreams();
void WaitForExit();
ScopedFd* SelectLoop(fd_set* master_read_set_ptr,
fd_set* master_write_set_ptr);
// Input/output stream handlers. Success returns nullptr, failure returns
// a pointer to the failed FD.
ScopedFd* PassInput();
ScopedFd* PassOutput(ScopedFd* sfd, ShellProtocol::Id id);
const std::string command_;
SubprocessType type_;
SubprocessProtocol protocol_;
pid_t pid_ = -1;
ScopedFd local_socket_sfd_;
// Shell protocol variables.
ScopedFd stdinout_sfd_, stderr_sfd_, protocol_sfd_;
std::unique_ptr<ShellProtocol> input_, output_;
size_t input_bytes_left_ = 0;
DISALLOW_COPY_AND_ASSIGN(Subprocess);
};
Subprocess::Subprocess(const std::string& command, SubprocessType type,
SubprocessProtocol protocol)
: command_(command), type_(type), protocol_(protocol) {
}
Subprocess::~Subprocess() {
}
bool Subprocess::ForkAndExec() {
ScopedFd child_stdinout_sfd, child_stderr_sfd;
ScopedFd parent_error_sfd, child_error_sfd;
char pts_name[PATH_MAX];
// Create a socketpair for the fork() child to report any errors back to
// the parent. Since we use threads, logging directly from the child could
// create a race condition.
if (!CreateSocketpair(&parent_error_sfd, &child_error_sfd)) {
LOG(ERROR) << "failed to create pipe for subprocess error reporting";
}
if (type_ == SubprocessType::kPty) {
int fd;
pid_ = forkpty(&fd, pts_name, nullptr, nullptr);
stdinout_sfd_.Reset(fd);
} else {
if (!CreateSocketpair(&stdinout_sfd_, &child_stdinout_sfd)) {
return false;
}
// Raw subprocess + shell protocol allows for splitting stderr.
if (protocol_ == SubprocessProtocol::kShell &&
!CreateSocketpair(&stderr_sfd_, &child_stderr_sfd)) {
return false;
}
pid_ = fork();
}
if (pid_ == -1) {
PLOG(ERROR) << "fork failed";
return false;
}
if (pid_ == 0) {
// Subprocess child.
init_subproc_child();
if (type_ == SubprocessType::kPty) {
child_stdinout_sfd.Reset(OpenPtyChildFd(pts_name, &child_error_sfd));
}
dup2(child_stdinout_sfd.fd(), STDIN_FILENO);
dup2(child_stdinout_sfd.fd(), STDOUT_FILENO);
dup2(child_stderr_sfd.valid() ? child_stderr_sfd.fd() : child_stdinout_sfd.fd(),
STDERR_FILENO);
// exec doesn't trigger destructors, close the FDs manually.
stdinout_sfd_.Reset();
stderr_sfd_.Reset();
child_stdinout_sfd.Reset();
child_stderr_sfd.Reset();
parent_error_sfd.Reset();
close_on_exec(child_error_sfd.fd());
// TODO: $HOSTNAME? Normally bash automatically sets that, but mksh doesn't.
passwd* pw = getpwuid(getuid());
if (pw != nullptr) {
setenv("HOME", pw->pw_dir, 1);
setenv("LOGNAME", pw->pw_name, 1);
setenv("SHELL", pw->pw_shell, 1);
setenv("USER", pw->pw_name, 1);
}
if (is_interactive()) {
execl(_PATH_BSHELL, _PATH_BSHELL, "-", nullptr);
} else {
execl(_PATH_BSHELL, _PATH_BSHELL, "-c", command_.c_str(), nullptr);
}
WriteFdExactly(child_error_sfd.fd(), "exec '" _PATH_BSHELL "' failed");
child_error_sfd.Reset();
exit(-1);
}
// Subprocess parent.
D("subprocess parent: stdin/stdout FD = %d, stderr FD = %d",
stdinout_sfd_.fd(), stderr_sfd_.fd());
// Wait to make sure the subprocess exec'd without error.
child_error_sfd.Reset();
std::string error_message = ReadAll(parent_error_sfd.fd());
if (!error_message.empty()) {
LOG(ERROR) << error_message;
return false;
}
if (protocol_ == SubprocessProtocol::kNone) {
// No protocol: all streams pass through the stdinout FD and hook
// directly into the local socket for raw data transfer.
local_socket_sfd_.Reset(stdinout_sfd_.Release());
} else {
// Shell protocol: create another socketpair to intercept data.
if (!CreateSocketpair(&protocol_sfd_, &local_socket_sfd_)) {
return false;
}
D("protocol FD = %d", protocol_sfd_.fd());
input_.reset(new ShellProtocol(protocol_sfd_.fd()));
output_.reset(new ShellProtocol(protocol_sfd_.fd()));
if (!input_ || !output_) {
LOG(ERROR) << "failed to allocate shell protocol objects";
return false;
}
// Don't let reads/writes to the subprocess block our thread. This isn't
// likely but could happen under unusual circumstances, such as if we
// write a ton of data to stdin but the subprocess never reads it and
// the pipe fills up.
for (int fd : {stdinout_sfd_.fd(), stderr_sfd_.fd()}) {
if (fd >= 0) {
if (!set_file_block_mode(fd, false)) {
LOG(ERROR) << "failed to set non-blocking mode for fd " << fd;
return false;
}
}
}
}
if (!adb_thread_create(ThreadHandler, this)) {
PLOG(ERROR) << "failed to create subprocess thread";
return false;
}
return true;
}
int Subprocess::OpenPtyChildFd(const char* pts_name, ScopedFd* error_sfd) {
int child_fd = adb_open(pts_name, O_RDWR | O_CLOEXEC);
if (child_fd == -1) {
// Don't use WriteFdFmt; since we're in the fork() child we don't want
// to allocate any heap memory to avoid race conditions.
const char* messages[] = {"child failed to open pseudo-term slave ",
pts_name, ": ", strerror(errno)};
for (const char* message : messages) {
WriteFdExactly(error_sfd->fd(), message);
}
exit(-1);
}
if (!is_interactive()) {
termios tattr;
if (tcgetattr(child_fd, &tattr) == -1) {
WriteFdExactly(error_sfd->fd(), "tcgetattr failed");
exit(-1);
}
cfmakeraw(&tattr);
if (tcsetattr(child_fd, TCSADRAIN, &tattr) == -1) {
WriteFdExactly(error_sfd->fd(), "tcsetattr failed");
exit(-1);
}
}
return child_fd;
}
void* Subprocess::ThreadHandler(void* userdata) {
Subprocess* subprocess = reinterpret_cast<Subprocess*>(userdata);
adb_thread_setname(android::base::StringPrintf(
"shell srvc %d", subprocess->local_socket_fd()));
subprocess->PassDataStreams();
subprocess->WaitForExit();
D("deleting Subprocess for PID %d", subprocess->pid());
delete subprocess;
return nullptr;
}
void Subprocess::PassDataStreams() {
if (!protocol_sfd_.valid()) {
return;
}
// Start by trying to read from the protocol FD, stdout, and stderr.
fd_set master_read_set, master_write_set;
FD_ZERO(&master_read_set);
FD_ZERO(&master_write_set);
for (ScopedFd* sfd : {&protocol_sfd_, &stdinout_sfd_, &stderr_sfd_}) {
if (sfd->valid()) {
FD_SET(sfd->fd(), &master_read_set);
}
}
// Pass data until the protocol FD or both the subprocess pipes die, at
// which point we can't pass any more data.
while (protocol_sfd_.valid() &&
(stdinout_sfd_.valid() || stderr_sfd_.valid())) {
ScopedFd* dead_sfd = SelectLoop(&master_read_set, &master_write_set);
if (dead_sfd) {
D("closing FD %d", dead_sfd->fd());
FD_CLR(dead_sfd->fd(), &master_read_set);
FD_CLR(dead_sfd->fd(), &master_write_set);
if (dead_sfd == &protocol_sfd_) {
// Using SIGHUP is a decent general way to indicate that the
// controlling process is going away. If specific signals are
// needed (e.g. SIGINT), pass those through the shell protocol
// and only fall back on this for unexpected closures.
D("protocol FD died, sending SIGHUP to pid %d", pid_);
kill(pid_, SIGHUP);
}
dead_sfd->Reset();
}
}
}
namespace {
inline bool ValidAndInSet(const ScopedFd& sfd, fd_set* set) {
return sfd.valid() && FD_ISSET(sfd.fd(), set);
}
} // namespace
ScopedFd* Subprocess::SelectLoop(fd_set* master_read_set_ptr,
fd_set* master_write_set_ptr) {
fd_set read_set, write_set;
int select_n = std::max(std::max(protocol_sfd_.fd(), stdinout_sfd_.fd()),
stderr_sfd_.fd()) + 1;
ScopedFd* dead_sfd = nullptr;
// Keep calling select() and passing data until an FD closes/errors.
while (!dead_sfd) {
memcpy(&read_set, master_read_set_ptr, sizeof(read_set));
memcpy(&write_set, master_write_set_ptr, sizeof(write_set));
if (select(select_n, &read_set, &write_set, nullptr, nullptr) < 0) {
if (errno == EINTR) {
continue;
} else {
PLOG(ERROR) << "select failed, closing subprocess pipes";
stdinout_sfd_.Reset();
stderr_sfd_.Reset();
return nullptr;
}
}
// Read stdout, write to protocol FD.
if (ValidAndInSet(stdinout_sfd_, &read_set)) {
dead_sfd = PassOutput(&stdinout_sfd_, ShellProtocol::kIdStdout);
}
// Read stderr, write to protocol FD.
if (!dead_sfd && ValidAndInSet(stderr_sfd_, &read_set)) {
dead_sfd = PassOutput(&stderr_sfd_, ShellProtocol::kIdStderr);
}
// Read protocol FD, write to stdin.
if (!dead_sfd && ValidAndInSet(protocol_sfd_, &read_set)) {
dead_sfd = PassInput();
// If we didn't finish writing, block on stdin write.
if (input_bytes_left_) {
FD_CLR(protocol_sfd_.fd(), master_read_set_ptr);
FD_SET(stdinout_sfd_.fd(), master_write_set_ptr);
}
}
// Continue writing to stdin; only happens if a previous write blocked.
if (!dead_sfd && ValidAndInSet(stdinout_sfd_, &write_set)) {
dead_sfd = PassInput();
// If we finished writing, go back to blocking on protocol read.
if (!input_bytes_left_) {
FD_SET(protocol_sfd_.fd(), master_read_set_ptr);
FD_CLR(stdinout_sfd_.fd(), master_write_set_ptr);
}
}
} // while (!dead_sfd)
return dead_sfd;
}
ScopedFd* Subprocess::PassInput() {
// Only read a new packet if we've finished writing the last one.
if (!input_bytes_left_) {
if (!input_->Read()) {
// Read() uses ReadFdExactly() which sets errno to 0 on EOF.
if (errno != 0) {
PLOG(ERROR) << "error reading protocol FD "
<< protocol_sfd_.fd();
}
return &protocol_sfd_;
}
if (stdinout_sfd_.valid()) {
switch (input_->id()) {
case ShellProtocol::kIdWindowSizeChange:
int rows, cols, x_pixels, y_pixels;
if (sscanf(input_->data(), "%dx%d,%dx%d",
&rows, &cols, &x_pixels, &y_pixels) == 4) {
winsize ws;
ws.ws_row = rows;
ws.ws_col = cols;
ws.ws_xpixel = x_pixels;
ws.ws_ypixel = y_pixels;
ioctl(stdinout_sfd_.fd(), TIOCSWINSZ, &ws);
}
break;
case ShellProtocol::kIdStdin:
input_bytes_left_ = input_->data_length();
break;
case ShellProtocol::kIdCloseStdin:
if (type_ == SubprocessType::kRaw) {
if (adb_shutdown(stdinout_sfd_.fd(), SHUT_WR) == 0) {
return nullptr;
}
PLOG(ERROR) << "failed to shutdown writes to FD "
<< stdinout_sfd_.fd();
return &stdinout_sfd_;
} else {
// PTYs can't close just input, so rather than close the
// FD and risk losing subprocess output, leave it open.
// This only happens if the client starts a PTY shell
// non-interactively which is rare and unsupported.
// If necessary, the client can manually close the shell
// with `exit` or by killing the adb client process.
D("can't close input for PTY FD %d", stdinout_sfd_.fd());
}
break;
}
}
}
if (input_bytes_left_ > 0) {
int index = input_->data_length() - input_bytes_left_;
int bytes = adb_write(stdinout_sfd_.fd(), input_->data() + index,
input_bytes_left_);
if (bytes == 0 || (bytes < 0 && errno != EAGAIN)) {
if (bytes < 0) {
PLOG(ERROR) << "error reading stdin FD " << stdinout_sfd_.fd();
}
// stdin is done, mark this packet as finished and we'll just start
// dumping any further data received from the protocol FD.
input_bytes_left_ = 0;
return &stdinout_sfd_;
} else if (bytes > 0) {
input_bytes_left_ -= bytes;
}
}
return nullptr;
}
ScopedFd* Subprocess::PassOutput(ScopedFd* sfd, ShellProtocol::Id id) {
int bytes = adb_read(sfd->fd(), output_->data(), output_->data_capacity());
if (bytes == 0 || (bytes < 0 && errno != EAGAIN)) {
// read() returns EIO if a PTY closes; don't report this as an error,
// it just means the subprocess completed.
if (bytes < 0 && !(type_ == SubprocessType::kPty && errno == EIO)) {
PLOG(ERROR) << "error reading output FD " << sfd->fd();
}
return sfd;
}
if (bytes > 0 && !output_->Write(id, bytes)) {
if (errno != 0) {
PLOG(ERROR) << "error reading protocol FD " << protocol_sfd_.fd();
}
return &protocol_sfd_;
}
return nullptr;
}
void Subprocess::WaitForExit() {
int exit_code = 1;
D("waiting for pid %d", pid_);
while (true) {
int status;
if (pid_ == waitpid(pid_, &status, 0)) {
D("post waitpid (pid=%d) status=%04x", pid_, status);
if (WIFSIGNALED(status)) {
exit_code = 0x80 | WTERMSIG(status);
D("subprocess killed by signal %d", WTERMSIG(status));
break;
} else if (!WIFEXITED(status)) {
D("subprocess didn't exit");
break;
} else if (WEXITSTATUS(status) >= 0) {
exit_code = WEXITSTATUS(status);
D("subprocess exit code = %d", WEXITSTATUS(status));
break;
}
}
}
// If we have an open protocol FD send an exit packet.
if (protocol_sfd_.valid()) {
output_->data()[0] = exit_code;
if (output_->Write(ShellProtocol::kIdExit, 1)) {
D("wrote the exit code packet: %d", exit_code);
} else {
PLOG(ERROR) << "failed to write the exit code packet";
}
protocol_sfd_.Reset();
}
// Pass the local socket FD to the shell cleanup fdevent.
if (SHELL_EXIT_NOTIFY_FD >= 0) {
int fd = local_socket_sfd_.fd();
if (WriteFdExactly(SHELL_EXIT_NOTIFY_FD, &fd, sizeof(fd))) {
D("passed fd %d to SHELL_EXIT_NOTIFY_FD (%d) for pid %d",
fd, SHELL_EXIT_NOTIFY_FD, pid_);
// The shell exit fdevent now owns the FD and will close it once
// the last bit of data flushes through.
local_socket_sfd_.Release();
} else {
PLOG(ERROR) << "failed to write fd " << fd
<< " to SHELL_EXIT_NOTIFY_FD (" << SHELL_EXIT_NOTIFY_FD
<< ") for pid " << pid_;
}
}
}
} // namespace
int StartSubprocess(const char *name, SubprocessType type,
SubprocessProtocol protocol) {
D("starting %s subprocess (protocol=%s): '%s'",
type == SubprocessType::kRaw ? "raw" : "PTY",
protocol == SubprocessProtocol::kNone ? "none" : "shell", name);
Subprocess* subprocess = new Subprocess(name, type, protocol);
if (!subprocess) {
LOG(ERROR) << "failed to allocate new subprocess";
return -1;
}
if (!subprocess->ForkAndExec()) {
LOG(ERROR) << "failed to start subprocess";
delete subprocess;
return -1;
}
D("subprocess creation successful: local_socket_fd=%d, pid=%d",
subprocess->local_socket_fd(), subprocess->pid());
return subprocess->local_socket_fd();
}
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