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android_system_core/adb/shell_service.cpp
Elliott Hughes 18ddf5c6a2 Pass $TERM to the device. 
Unfortunately, this isn't backwards-compatible with the current shell
protocol because we made unknown shell: arguments errors. We could try
to commit the change to make them just warnings first, but how would
we know when everyone was running adbd with that change? Bumping the
protocol version doesn't help because that only affects the code running
on the host. And although we could add another feature to the reported
features, since shell_v2 is still in development, that doesn't seem
worthwhile.

Bug: http://b/25601436
Change-Id: I12b81aa656cd25b91d14ef691dcbd2b7dab49535
2015-11-16 10:55:34 -08:00

676 lines
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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, const char* terminal_type,
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_;
const std::string terminal_type_;
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, const char* terminal_type,
SubprocessType type, SubprocessProtocol protocol)
: command_(command),
terminal_type_(terminal_type ? terminal_type : ""),
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 (!terminal_type_.empty()) {
setenv("TERM", terminal_type_.c_str(), 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, const char* terminal_type,
SubprocessType type, SubprocessProtocol protocol) {
D("starting %s subprocess (protocol=%s, TERM=%s): '%s'",
type == SubprocessType::kRaw ? "raw" : "PTY",
protocol == SubprocessProtocol::kNone ? "none" : "shell",
terminal_type, name);
Subprocess* subprocess = new Subprocess(name, terminal_type, 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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