adb: move shell service to a separate file.

Upcoming changes to the shell will require significant additions to
the subprocess code, and it will be cleaner if it's in a separate file.

The only functional change here is a new debug tag specifically for
the shell service. Everything else has been copied exactly as-is in
order to make it easier to determine what's changing in upcoming CLs.

Change-Id: I13bd4294059051ee10e0d0c6a06affd8eca62967
diff --git a/adb/shell_service.cpp b/adb/shell_service.cpp
new file mode 100644
index 0000000..6fdbbdb
--- /dev/null
+++ b/adb/shell_service.cpp
@@ -0,0 +1,227 @@
+/*
+ * 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.
+ */
+
+#define TRACE_TAG TRACE_SHELL
+
+#include "shell_service.h"
+
+#if !ADB_HOST
+
+#include <pty.h>
+#include <termios.h>
+
+#include <paths.h>
+
+#include "adb.h"
+#include "adb_io.h"
+#include "adb_trace.h"
+#include "sysdeps.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");
+    }
+}
+
+int create_subproc_pty(const char* cmd, const char* arg0, const char* arg1,
+                       pid_t* pid) {
+    D("create_subproc_pty(cmd=%s, arg0=%s, arg1=%s)", cmd, arg0, arg1);
+    char pts_name[PATH_MAX];
+    int ptm;
+    *pid = forkpty(&ptm, pts_name, nullptr, nullptr);
+    if (*pid == -1) {
+        printf("- fork failed: %s -\n", strerror(errno));
+        unix_close(ptm);
+        return -1;
+    }
+
+    if (*pid == 0) {
+        init_subproc_child();
+
+        int pts = unix_open(pts_name, O_RDWR | O_CLOEXEC);
+        if (pts == -1) {
+            fprintf(stderr, "child failed to open pseudo-term slave %s: %s\n",
+                    pts_name, strerror(errno));
+            unix_close(ptm);
+            exit(-1);
+        }
+
+        // arg0 is "-c" in batch mode and "-" in interactive mode.
+        if (strcmp(arg0, "-c") == 0) {
+            termios tattr;
+            if (tcgetattr(pts, &tattr) == -1) {
+                fprintf(stderr, "tcgetattr failed: %s\n", strerror(errno));
+                unix_close(pts);
+                unix_close(ptm);
+                exit(-1);
+            }
+
+            cfmakeraw(&tattr);
+            if (tcsetattr(pts, TCSADRAIN, &tattr) == -1) {
+                fprintf(stderr, "tcsetattr failed: %s\n", strerror(errno));
+                unix_close(pts);
+                unix_close(ptm);
+                exit(-1);
+            }
+        }
+
+        dup2(pts, STDIN_FILENO);
+        dup2(pts, STDOUT_FILENO);
+        dup2(pts, STDERR_FILENO);
+
+        unix_close(pts);
+        unix_close(ptm);
+
+        execl(cmd, cmd, arg0, arg1, nullptr);
+        fprintf(stderr, "- exec '%s' failed: %s (%d) -\n",
+                cmd, strerror(errno), errno);
+        exit(-1);
+    } else {
+        return ptm;
+    }
+}
+
+int create_subproc_raw(const char *cmd, const char *arg0, const char *arg1,
+                       pid_t *pid)
+{
+    D("create_subproc_raw(cmd=%s, arg0=%s, arg1=%s)", cmd, arg0, arg1);
+
+    // 0 is parent socket, 1 is child socket
+    int sv[2];
+    if (adb_socketpair(sv) < 0) {
+        printf("[ cannot create socket pair - %s ]\n", strerror(errno));
+        return -1;
+    }
+    D("socketpair: (%d,%d)", sv[0], sv[1]);
+
+    *pid = fork();
+    if (*pid < 0) {
+        printf("- fork failed: %s -\n", strerror(errno));
+        adb_close(sv[0]);
+        adb_close(sv[1]);
+        return -1;
+    }
+
+    if (*pid == 0) {
+        adb_close(sv[0]);
+        init_subproc_child();
+
+        dup2(sv[1], STDIN_FILENO);
+        dup2(sv[1], STDOUT_FILENO);
+        dup2(sv[1], STDERR_FILENO);
+
+        adb_close(sv[1]);
+
+        execl(cmd, cmd, arg0, arg1, NULL);
+        fprintf(stderr, "- exec '%s' failed: %s (%d) -\n",
+                cmd, strerror(errno), errno);
+        exit(-1);
+    } else {
+        adb_close(sv[1]);
+        return sv[0];
+    }
+}
+
+void subproc_waiter_service(int fd, void *cookie)
+{
+    pid_t pid = (pid_t) (uintptr_t) cookie;
+
+    D("entered. fd=%d of pid=%d", fd, pid);
+    while (true) {
+        int status;
+        pid_t p = waitpid(pid, &status, 0);
+        if (p == pid) {
+            D("fd=%d, post waitpid(pid=%d) status=%04x", fd, p, status);
+            if (WIFSIGNALED(status)) {
+                D("*** Killed by signal %d", WTERMSIG(status));
+                break;
+            } else if (!WIFEXITED(status)) {
+                D("*** Didn't exit!!. status %d", status);
+                break;
+            } else if (WEXITSTATUS(status) >= 0) {
+                D("*** Exit code %d", WEXITSTATUS(status));
+                break;
+            }
+         }
+    }
+    D("shell exited fd=%d of pid=%d err=%d", fd, pid, errno);
+    if (SHELL_EXIT_NOTIFY_FD >=0) {
+      int res;
+      res = WriteFdExactly(SHELL_EXIT_NOTIFY_FD, &fd, sizeof(fd)) ? 0 : -1;
+      D("notified shell exit via fd=%d for pid=%d res=%d errno=%d",
+        SHELL_EXIT_NOTIFY_FD, pid, res, errno);
+    }
+}
+
+}  // namespace
+
+// References to things in services.cpp. This is temporary just to make as few
+// modifications as possible while moving functionality into it's own file.
+// TODO(dpursell): remove these in the next CL.
+void *service_bootstrap_func(void *x);
+struct stinfo_duplicate {
+    void (*func)(int fd, void *cookie);
+    int fd;
+    void *cookie;
+};
+
+int StartSubprocess(const char *name, SubprocessType type) {
+    const char *arg0, *arg1;
+    if (*name == '\0') {
+        arg0 = "-";
+        arg1 = nullptr;
+    } else {
+        arg0 = "-c";
+        arg1 = name;
+    }
+
+    pid_t pid = -1;
+    int ret_fd;
+    if (type == SubprocessType::kPty) {
+        ret_fd = create_subproc_pty(_PATH_BSHELL, arg0, arg1, &pid);
+    } else {
+        ret_fd = create_subproc_raw(_PATH_BSHELL, arg0, arg1, &pid);
+    }
+    D("create_subproc ret_fd=%d pid=%d", ret_fd, pid);
+
+    stinfo_duplicate* sti = reinterpret_cast<stinfo_duplicate*>(malloc(sizeof(stinfo_duplicate)));
+    if(sti == 0) fatal("cannot allocate stinfo");
+    sti->func = subproc_waiter_service;
+    sti->cookie = (void*) (uintptr_t) pid;
+    sti->fd = ret_fd;
+
+    if (!adb_thread_create(service_bootstrap_func, sti)) {
+        free(sti);
+        adb_close(ret_fd);
+        fprintf(stderr, "cannot create service thread\n");
+        return -1;
+    }
+
+    D("service thread started, fd=%d pid=%d", ret_fd, pid);
+    return ret_fd;
+}
+
+#endif  // !ADB_HOST