logwrapper/logwrap.cpp - LeafOS-Project/android_system_core - Gitiles

 /*
  * Copyright (C) 2008 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 <fcntl.h>
 #include <libgen.h>
 #include <poll.h>
 #include <pthread.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/socket.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <unistd.h>

 #include <algorithm>

 #include <android-base/macros.h>
 #include <cutils/klog.h>
 #include <log/log.h>
 #include <logwrap/logwrap.h>

 static pthread_mutex_t fd_mutex = PTHREAD_MUTEX_INITIALIZER;
 // Protected by fd_mutex.  These signals must be blocked while modifying as well.
 static pid_t child_pid;
 static struct sigaction old_int;
 static struct sigaction old_quit;
 static struct sigaction old_hup;

 #define ERROR(fmt, args...)                         \
     do {                                            \
         fprintf(stderr, fmt, ##args);               \
         ALOG(LOG_ERROR, "logwrapper", fmt, ##args); \
     } while (0)

 #define FATAL_CHILD(fmt, args...) \
     do {                          \
         ERROR(fmt, ##args);       \
         _exit(-1);                \
     } while (0)

 #define MAX_KLOG_TAG 16

 /* This is a simple buffer that holds up to the first beginning_buf->buf_size
  * bytes of output from a command.
  */
 #define BEGINNING_BUF_SIZE 0x1000
 struct beginning_buf {
     char* buf;
     size_t alloc_len;
     /* buf_size is the usable space, which is one less than the allocated size */
     size_t buf_size;
     size_t used_len;
 };

 /* This is a circular buf that holds up to the last ending_buf->buf_size bytes
  * of output from a command after the first beginning_buf->buf_size bytes
  * (which are held in beginning_buf above).
  */
 #define ENDING_BUF_SIZE 0x1000
 struct ending_buf {
     char* buf;
     ssize_t alloc_len;
     /* buf_size is the usable space, which is one less than the allocated size */
     ssize_t buf_size;
     ssize_t used_len;
     /* read and write offsets into the circular buffer */
     int read;
     int write;
 };

 /* A structure to hold all the abbreviated buf data */
 struct abbr_buf {
     struct beginning_buf b_buf;
     struct ending_buf e_buf;
     int beginning_buf_full;
 };

 /* Collect all the various bits of info needed for logging in one place. */
 struct log_info {
     int log_target;
     char klog_fmt[MAX_KLOG_TAG * 2];
     const char* btag;
     bool abbreviated;
     FILE* fp;
     struct abbr_buf a_buf;
 };

 /* Forware declaration */
 static void add_line_to_abbr_buf(struct abbr_buf* a_buf, char* linebuf, int linelen);

 /* Return 0 on success, and 1 when full */
 static int add_line_to_linear_buf(struct beginning_buf* b_buf, char* line, ssize_t line_len) {
     int full = 0;

     if ((line_len + b_buf->used_len) > b_buf->buf_size) {
         full = 1;
     } else {
         /* Add to the end of the buf */
         memcpy(b_buf->buf + b_buf->used_len, line, line_len);
         b_buf->used_len += line_len;
     }

     return full;
 }

 static void add_line_to_circular_buf(struct ending_buf* e_buf, char* line, ssize_t line_len) {
     ssize_t free_len;
     ssize_t needed_space;
     int cnt;

     if (e_buf->buf == nullptr) {
         return;
     }

     if (line_len > e_buf->buf_size) {
         return;
     }

     free_len = e_buf->buf_size - e_buf->used_len;

     if (line_len > free_len) {
         /* remove oldest entries at read, and move read to make
          * room for the new string */
         needed_space = line_len - free_len;
         e_buf->read = (e_buf->read + needed_space) % e_buf->buf_size;
         e_buf->used_len -= needed_space;
     }

     /* Copy the line into the circular buffer, dealing with possible
      * wraparound.
      */
     cnt = std::min(line_len, e_buf->buf_size - e_buf->write);
     memcpy(e_buf->buf + e_buf->write, line, cnt);
     if (cnt < line_len) {
         memcpy(e_buf->buf, line + cnt, line_len - cnt);
     }
     e_buf->used_len += line_len;
     e_buf->write = (e_buf->write + line_len) % e_buf->buf_size;
 }

 /* Log directly to the specified log */
 static void do_log_line(struct log_info* log_info, const char* line) {
     if (log_info->log_target & LOG_KLOG) {
         klog_write(6, log_info->klog_fmt, line);
     }
     if (log_info->log_target & LOG_ALOG) {
         ALOG(LOG_INFO, log_info->btag, "%s", line);
     }
     if (log_info->log_target & LOG_FILE) {
         fprintf(log_info->fp, "%s\n", line);
     }
 }

 /* Log to either the abbreviated buf, or directly to the specified log
  * via do_log_line() above.
  */
 static void log_line(struct log_info* log_info, char* line, int len) {
     if (log_info->abbreviated) {
         add_line_to_abbr_buf(&log_info->a_buf, line, len);
     } else {
         do_log_line(log_info, line);
     }
 }

 /*
  * The kernel will take a maximum of 1024 bytes in any single write to
  * the kernel logging device file, so find and print each line one at
  * a time.  The allocated size for buf should be at least 1 byte larger
  * than buf_size (the usable size of the buffer) to make sure there is
  * room to temporarily stuff a null byte to terminate a line for logging.
  */
 static void print_buf_lines(struct log_info* log_info, char* buf, int buf_size) {
     char* line_start;
     char c;
     int i;

     line_start = buf;
     for (i = 0; i < buf_size; i++) {
         if (*(buf + i) == '\n') {
             /* Found a line ending, print the line and compute new line_start */
             /* Save the next char and replace with \0 */
             c = *(buf + i + 1);
             *(buf + i + 1) = '\0';
             do_log_line(log_info, line_start);
             /* Restore the saved char */
             *(buf + i + 1) = c;
             line_start = buf + i + 1;
         } else if (*(buf + i) == '\0') {
             /* The end of the buffer, print the last bit */
             do_log_line(log_info, line_start);
             break;
         }
     }
     /* If the buffer was completely full, and didn't end with a newline, just
      * ignore the partial last line.
      */
 }

 static void init_abbr_buf(struct abbr_buf* a_buf) {
     char* new_buf;

     memset(a_buf, 0, sizeof(struct abbr_buf));
     new_buf = static_cast<char*>(malloc(BEGINNING_BUF_SIZE));
     if (new_buf) {
         a_buf->b_buf.buf = new_buf;
         a_buf->b_buf.alloc_len = BEGINNING_BUF_SIZE;
         a_buf->b_buf.buf_size = BEGINNING_BUF_SIZE - 1;
     }
     new_buf = static_cast<char*>(malloc(ENDING_BUF_SIZE));
     if (new_buf) {
         a_buf->e_buf.buf = new_buf;
         a_buf->e_buf.alloc_len = ENDING_BUF_SIZE;
         a_buf->e_buf.buf_size = ENDING_BUF_SIZE - 1;
     }
 }

 static void free_abbr_buf(struct abbr_buf* a_buf) {
     free(a_buf->b_buf.buf);
     free(a_buf->e_buf.buf);
 }

 static void add_line_to_abbr_buf(struct abbr_buf* a_buf, char* linebuf, int linelen) {
     if (!a_buf->beginning_buf_full) {
         a_buf->beginning_buf_full = add_line_to_linear_buf(&a_buf->b_buf, linebuf, linelen);
     }
     if (a_buf->beginning_buf_full) {
         add_line_to_circular_buf(&a_buf->e_buf, linebuf, linelen);
     }
 }

 static void print_abbr_buf(struct log_info* log_info) {
     struct abbr_buf* a_buf = &log_info->a_buf;

     /* Add the abbreviated output to the kernel log */
     if (a_buf->b_buf.alloc_len) {
         print_buf_lines(log_info, a_buf->b_buf.buf, a_buf->b_buf.used_len);
     }

     /* Print an ellipsis to indicate that the buffer has wrapped or
      * is full, and some data was not logged.
      */
     if (a_buf->e_buf.used_len == a_buf->e_buf.buf_size) {
         do_log_line(log_info, "...\n");
     }

     if (a_buf->e_buf.used_len == 0) {
         return;
     }

     /* Simplest way to print the circular buffer is allocate a second buf
      * of the same size, and memcpy it so it's a simple linear buffer,
      * and then cal print_buf_lines on it */
     if (a_buf->e_buf.read < a_buf->e_buf.write) {
         /* no wrap around, just print it */
         print_buf_lines(log_info, a_buf->e_buf.buf + a_buf->e_buf.read, a_buf->e_buf.used_len);
     } else {
         /* The circular buffer will always have at least 1 byte unused,
          * so by allocating alloc_len here we will have at least
          * 1 byte of space available as required by print_buf_lines().
          */
         char* nbuf = static_cast<char*>(malloc(a_buf->e_buf.alloc_len));
         if (!nbuf) {
             return;
         }
         int first_chunk_len = a_buf->e_buf.buf_size - a_buf->e_buf.read;
         memcpy(nbuf, a_buf->e_buf.buf + a_buf->e_buf.read, first_chunk_len);
         /* copy second chunk */
         memcpy(nbuf + first_chunk_len, a_buf->e_buf.buf, a_buf->e_buf.write);
         print_buf_lines(log_info, nbuf, first_chunk_len + a_buf->e_buf.write);
         free(nbuf);
     }
 }

 static void signal_handler(int signal_num);

 static void block_signals(sigset_t* oldset) {
     sigset_t blockset;

     sigemptyset(&blockset);
     sigaddset(&blockset, SIGINT);
     sigaddset(&blockset, SIGQUIT);
     sigaddset(&blockset, SIGHUP);
     pthread_sigmask(SIG_BLOCK, &blockset, oldset);
 }

 static void unblock_signals(sigset_t* oldset) {
     pthread_sigmask(SIG_SETMASK, oldset, nullptr);
 }

 static void setup_signal_handlers(pid_t pid) {
     struct sigaction handler = {.sa_handler = signal_handler};

     child_pid = pid;
     sigaction(SIGINT, &handler, &old_int);
     sigaction(SIGQUIT, &handler, &old_quit);
     sigaction(SIGHUP, &handler, &old_hup);
 }

 static void restore_signal_handlers() {
     sigaction(SIGINT, &old_int, nullptr);
     sigaction(SIGQUIT, &old_quit, nullptr);
     sigaction(SIGHUP, &old_hup, nullptr);
     child_pid = 0;
 }

 static void signal_handler(int signal_num) {
     if (child_pid == 0 || kill(child_pid, signal_num) != 0) {
         restore_signal_handlers();
         raise(signal_num);
     }
 }

 static int parent(const char* tag, int parent_read, pid_t pid, int* chld_sts, int log_target,
                   bool abbreviated, const char* file_path, bool forward_signals) {
     int status = 0;
     char buffer[4096];
     struct pollfd poll_fds[] = {
             {
                     .fd = parent_read,
                     .events = POLLIN,
             },
     };
     int rc = 0;
     int fd;

     struct log_info log_info;

     int a = 0;  // start index of unprocessed data
     int b = 0;  // end index of unprocessed data
     int sz;
     bool found_child = false;
     // There is a very small chance that opening child_ptty in the child will fail, but in this case
     // POLLHUP will not be generated below.  Therefore, we use a 1 second timeout for poll() until
     // we receive a message from child_ptty.  If this times out, we call waitpid() with WNOHANG to
     // check the status of the child process and exit appropriately if it has terminated.
     bool received_messages = false;
     char tmpbuf[256];

     log_info.btag = basename(tag);
     if (!log_info.btag) {
         log_info.btag = tag;
     }

     if (abbreviated && (log_target == LOG_NONE)) {
         abbreviated = 0;
     }
     if (abbreviated) {
         init_abbr_buf(&log_info.a_buf);
     }

     if (log_target & LOG_KLOG) {
         snprintf(log_info.klog_fmt, sizeof(log_info.klog_fmt), "<6>%.*s: %%s\n", MAX_KLOG_TAG,
                  log_info.btag);
     }

     if ((log_target & LOG_FILE) && !file_path) {
         /* No file_path specified, clear the LOG_FILE bit */
         log_target &= ~LOG_FILE;
     }

     if (log_target & LOG_FILE) {
         fd = open(file_path, O_WRONLY | O_CREAT, 0664);
         if (fd < 0) {
             ERROR("Cannot log to file %s\n", file_path);
             log_target &= ~LOG_FILE;
         } else {
             lseek(fd, 0, SEEK_END);
             log_info.fp = fdopen(fd, "a");
         }
     }

     log_info.log_target = log_target;
     log_info.abbreviated = abbreviated;

     while (!found_child) {
         int timeout = received_messages ? -1 : 1000;
         if (TEMP_FAILURE_RETRY(poll(poll_fds, arraysize(poll_fds), timeout)) < 0) {
             ERROR("poll failed\n");
             rc = -1;
             goto err_poll;
         }

         if (poll_fds[0].revents & POLLIN) {
             received_messages = true;
             sz = TEMP_FAILURE_RETRY(read(parent_read, &buffer[b], sizeof(buffer) - 1 - b));

             sz += b;
             // Log one line at a time
             for (b = 0; b < sz; b++) {
                 if (buffer[b] == '\r') {
                     if (abbreviated) {
                         /* The abbreviated logging code uses newline as
                          * the line separator.  Lucikly, the pty layer
                          * helpfully cooks the output of the command
                          * being run and inserts a CR before NL.  So
                          * I just change it to NL here when doing
                          * abbreviated logging.
                          */
                         buffer[b] = '\n';
                     } else {
                         buffer[b] = '\0';
                     }
                 } else if (buffer[b] == '\n') {
                     buffer[b] = '\0';
                     log_line(&log_info, &buffer[a], b - a);
                     a = b + 1;
                 }
             }

             if (a == 0 && b == sizeof(buffer) - 1) {
                 // buffer is full, flush
                 buffer[b] = '\0';
                 log_line(&log_info, &buffer[a], b - a);
                 b = 0;
             } else if (a != b) {
                 // Keep left-overs
                 b -= a;
                 memmove(buffer, &buffer[a], b);
                 a = 0;
             } else {
                 a = 0;
                 b = 0;
             }
         }

         if (!received_messages || (poll_fds[0].revents & POLLHUP)) {
             int ret;
             sigset_t oldset;

             if (forward_signals) {
                 // Our signal handlers forward these signals to 'child_pid', but waitpid() may reap
                 // the child, so we must block these signals until we either 1) conclude that the
                 // child is still running or 2) determine the child has been reaped and we have
                 // reset the signals to their original disposition.
                 block_signals(&oldset);
             }

             int flags = (poll_fds[0].revents & POLLHUP) ? 0 : WNOHANG;
             ret = TEMP_FAILURE_RETRY(waitpid(pid, &status, flags));
             if (ret < 0) {
                 rc = errno;
                 ALOG(LOG_ERROR, "logwrap", "waitpid failed with %s\n", strerror(errno));
                 goto err_waitpid;
             }
             if (ret > 0) {
                 found_child = true;
             }

             if (forward_signals) {
                 if (found_child) {
                     restore_signal_handlers();
                 }
                 unblock_signals(&oldset);
             }
         }
     }

     if (chld_sts != nullptr) {
         *chld_sts = status;
     } else {
         if (WIFEXITED(status))
             rc = WEXITSTATUS(status);
         else
             rc = -ECHILD;
     }

     // Flush remaining data
     if (a != b) {
         buffer[b] = '\0';
         log_line(&log_info, &buffer[a], b - a);
     }

     /* All the output has been processed, time to dump the abbreviated output */
     if (abbreviated) {
         print_abbr_buf(&log_info);
     }

     if (WIFEXITED(status)) {
         if (WEXITSTATUS(status)) {
             snprintf(tmpbuf, sizeof(tmpbuf), "%s terminated by exit(%d)\n", log_info.btag,
                      WEXITSTATUS(status));
             do_log_line(&log_info, tmpbuf);
         }
     } else {
         if (WIFSIGNALED(status)) {
             snprintf(tmpbuf, sizeof(tmpbuf), "%s terminated by signal %d\n", log_info.btag,
                      WTERMSIG(status));
             do_log_line(&log_info, tmpbuf);
         } else if (WIFSTOPPED(status)) {
             snprintf(tmpbuf, sizeof(tmpbuf), "%s stopped by signal %d\n", log_info.btag,
                      WSTOPSIG(status));
             do_log_line(&log_info, tmpbuf);
         }
     }

 err_waitpid:
 err_poll:
     if (log_target & LOG_FILE) {
         fclose(log_info.fp); /* Also closes underlying fd */
     }
     if (abbreviated) {
         free_abbr_buf(&log_info.a_buf);
     }
     return rc;
 }

 static void child(int argc, const char* const* argv) {
     // create null terminated argv_child array
     char* argv_child[argc + 1];
     memcpy(argv_child, argv, argc * sizeof(char*));
     argv_child[argc] = nullptr;

     if (execvp(argv_child[0], argv_child)) {
         FATAL_CHILD("executing %s failed: %s\n", argv_child[0], strerror(errno));
     }
 }

 int logwrap_fork_execvp(int argc, const char* const* argv, int* status, bool forward_signals,
                         int log_target, bool abbreviated, const char* file_path) {
     pid_t pid;
     int parent_ptty;
     sigset_t oldset;
     int rc = 0;

     rc = pthread_mutex_lock(&fd_mutex);
     if (rc) {
         ERROR("failed to lock signal_fd mutex\n");
         goto err_lock;
     }

     /* Use ptty instead of socketpair so that STDOUT is not buffered */
     parent_ptty = TEMP_FAILURE_RETRY(posix_openpt(O_RDWR | O_CLOEXEC));
     if (parent_ptty < 0) {
         ERROR("Cannot create parent ptty\n");
         rc = -1;
         goto err_open;
     }

     char child_devname[64];
     if (grantpt(parent_ptty) || unlockpt(parent_ptty) ||
         ptsname_r(parent_ptty, child_devname, sizeof(child_devname)) != 0) {
         ERROR("Problem with /dev/ptmx\n");
         rc = -1;
         goto err_ptty;
     }

     if (forward_signals) {
         // Block these signals until we have the child pid and our signal handlers set up.
         block_signals(&oldset);
     }

     pid = fork();
     if (pid < 0) {
         ERROR("Failed to fork\n");
         rc = -1;
         goto err_fork;
     } else if (pid == 0) {
         pthread_mutex_unlock(&fd_mutex);
         if (forward_signals) {
             unblock_signals(&oldset);
         }

         setsid();

         int child_ptty = TEMP_FAILURE_RETRY(open(child_devname, O_RDWR | O_CLOEXEC));
         if (child_ptty < 0) {
             FATAL_CHILD("Cannot open child_ptty: %s\n", strerror(errno));
         }
         close(parent_ptty);

         dup2(child_ptty, 1);
         dup2(child_ptty, 2);
         close(child_ptty);

         child(argc, argv);
     } else {
         if (forward_signals) {
             setup_signal_handlers(pid);
             unblock_signals(&oldset);
         }

         rc = parent(argv[0], parent_ptty, pid, status, log_target, abbreviated, file_path,
                     forward_signals);

         if (forward_signals) {
             restore_signal_handlers();
         }
     }

 err_fork:
     if (forward_signals) {
         unblock_signals(&oldset);
     }
 err_ptty:
     close(parent_ptty);
 err_open:
     pthread_mutex_unlock(&fd_mutex);
 err_lock:
     return rc;
 }
	/*
	* Copyright (C) 2008 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 <fcntl.h>
	#include <libgen.h>
	#include <poll.h>
	#include <pthread.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <string.h>
	#include <sys/socket.h>
	#include <sys/types.h>
	#include <sys/wait.h>
	#include <unistd.h>

	#include <algorithm>

	#include <android-base/macros.h>
	#include <cutils/klog.h>
	#include <log/log.h>
	#include <logwrap/logwrap.h>

	static pthread_mutex_t fd_mutex = PTHREAD_MUTEX_INITIALIZER;
	// Protected by fd_mutex. These signals must be blocked while modifying as well.
	static pid_t child_pid;
	static struct sigaction old_int;
	static struct sigaction old_quit;
	static struct sigaction old_hup;

	#define ERROR(fmt, args...) \
	do { \
	fprintf(stderr, fmt, ##args); \
	ALOG(LOG_ERROR, "logwrapper", fmt, ##args); \
	} while (0)

	#define FATAL_CHILD(fmt, args...) \
	do { \
	ERROR(fmt, ##args); \
	_exit(-1); \
	} while (0)

	#define MAX_KLOG_TAG 16

	/* This is a simple buffer that holds up to the first beginning_buf->buf_size
	* bytes of output from a command.
	*/
	#define BEGINNING_BUF_SIZE 0x1000
	struct beginning_buf {
	char* buf;
	size_t alloc_len;
	/* buf_size is the usable space, which is one less than the allocated size */
	size_t buf_size;
	size_t used_len;
	};

	/* This is a circular buf that holds up to the last ending_buf->buf_size bytes
	* of output from a command after the first beginning_buf->buf_size bytes
	* (which are held in beginning_buf above).
	*/
	#define ENDING_BUF_SIZE 0x1000
	struct ending_buf {
	char* buf;
	ssize_t alloc_len;
	/* buf_size is the usable space, which is one less than the allocated size */
	ssize_t buf_size;
	ssize_t used_len;
	/* read and write offsets into the circular buffer */
	int read;
	int write;
	};

	/* A structure to hold all the abbreviated buf data */
	struct abbr_buf {
	struct beginning_buf b_buf;
	struct ending_buf e_buf;
	int beginning_buf_full;
	};

	/* Collect all the various bits of info needed for logging in one place. */
	struct log_info {
	int log_target;
	char klog_fmt[MAX_KLOG_TAG * 2];
	const char* btag;
	bool abbreviated;
	FILE* fp;
	struct abbr_buf a_buf;
	};

	/* Forware declaration */
	static void add_line_to_abbr_buf(struct abbr_buf* a_buf, char* linebuf, int linelen);

	/* Return 0 on success, and 1 when full */
	static int add_line_to_linear_buf(struct beginning_buf* b_buf, char* line, ssize_t line_len) {
	int full = 0;

	if ((line_len + b_buf->used_len) > b_buf->buf_size) {
	full = 1;
	} else {
	/* Add to the end of the buf */
	memcpy(b_buf->buf + b_buf->used_len, line, line_len);
	b_buf->used_len += line_len;
	}

	return full;
	}

	static void add_line_to_circular_buf(struct ending_buf* e_buf, char* line, ssize_t line_len) {
	ssize_t free_len;
	ssize_t needed_space;
	int cnt;

	if (e_buf->buf == nullptr) {
	return;
	}

	if (line_len > e_buf->buf_size) {
	return;
	}

	free_len = e_buf->buf_size - e_buf->used_len;

	if (line_len > free_len) {
	/* remove oldest entries at read, and move read to make
	* room for the new string */
	needed_space = line_len - free_len;
	e_buf->read = (e_buf->read + needed_space) % e_buf->buf_size;
	e_buf->used_len -= needed_space;
	}

	/* Copy the line into the circular buffer, dealing with possible
	* wraparound.
	*/
	cnt = std::min(line_len, e_buf->buf_size - e_buf->write);
	memcpy(e_buf->buf + e_buf->write, line, cnt);
	if (cnt < line_len) {
	memcpy(e_buf->buf, line + cnt, line_len - cnt);
	}
	e_buf->used_len += line_len;
	e_buf->write = (e_buf->write + line_len) % e_buf->buf_size;
	}

	/* Log directly to the specified log */
	static void do_log_line(struct log_info* log_info, const char* line) {
	if (log_info->log_target & LOG_KLOG) {
	klog_write(6, log_info->klog_fmt, line);
	}
	if (log_info->log_target & LOG_ALOG) {
	ALOG(LOG_INFO, log_info->btag, "%s", line);
	}
	if (log_info->log_target & LOG_FILE) {
	fprintf(log_info->fp, "%s\n", line);
	}
	}

	/* Log to either the abbreviated buf, or directly to the specified log
	* via do_log_line() above.
	*/
	static void log_line(struct log_info* log_info, char* line, int len) {
	if (log_info->abbreviated) {
	add_line_to_abbr_buf(&log_info->a_buf, line, len);
	} else {
	do_log_line(log_info, line);
	}
	}

	/*
	* The kernel will take a maximum of 1024 bytes in any single write to
	* the kernel logging device file, so find and print each line one at
	* a time. The allocated size for buf should be at least 1 byte larger
	* than buf_size (the usable size of the buffer) to make sure there is
	* room to temporarily stuff a null byte to terminate a line for logging.
	*/
	static void print_buf_lines(struct log_info* log_info, char* buf, int buf_size) {
	char* line_start;
	char c;
	int i;

	line_start = buf;
	for (i = 0; i < buf_size; i++) {
	if (*(buf + i) == '\n') {
	/* Found a line ending, print the line and compute new line_start */
	/* Save the next char and replace with \0 */
	c = *(buf + i + 1);
	*(buf + i + 1) = '\0';
	do_log_line(log_info, line_start);
	/* Restore the saved char */
	*(buf + i + 1) = c;
	line_start = buf + i + 1;
	} else if (*(buf + i) == '\0') {
	/* The end of the buffer, print the last bit */
	do_log_line(log_info, line_start);
	break;
	}
	}
	/* If the buffer was completely full, and didn't end with a newline, just
	* ignore the partial last line.
	*/
	}

	static void init_abbr_buf(struct abbr_buf* a_buf) {
	char* new_buf;

	memset(a_buf, 0, sizeof(struct abbr_buf));
	new_buf = static_cast<char*>(malloc(BEGINNING_BUF_SIZE));
	if (new_buf) {
	a_buf->b_buf.buf = new_buf;
	a_buf->b_buf.alloc_len = BEGINNING_BUF_SIZE;
	a_buf->b_buf.buf_size = BEGINNING_BUF_SIZE - 1;
	}
	new_buf = static_cast<char*>(malloc(ENDING_BUF_SIZE));
	if (new_buf) {
	a_buf->e_buf.buf = new_buf;
	a_buf->e_buf.alloc_len = ENDING_BUF_SIZE;
	a_buf->e_buf.buf_size = ENDING_BUF_SIZE - 1;
	}
	}

	static void free_abbr_buf(struct abbr_buf* a_buf) {
	free(a_buf->b_buf.buf);
	free(a_buf->e_buf.buf);
	}

	static void add_line_to_abbr_buf(struct abbr_buf* a_buf, char* linebuf, int linelen) {
	if (!a_buf->beginning_buf_full) {
	a_buf->beginning_buf_full = add_line_to_linear_buf(&a_buf->b_buf, linebuf, linelen);
	}
	if (a_buf->beginning_buf_full) {
	add_line_to_circular_buf(&a_buf->e_buf, linebuf, linelen);
	}
	}

	static void print_abbr_buf(struct log_info* log_info) {
	struct abbr_buf* a_buf = &log_info->a_buf;

	/* Add the abbreviated output to the kernel log */
	if (a_buf->b_buf.alloc_len) {
	print_buf_lines(log_info, a_buf->b_buf.buf, a_buf->b_buf.used_len);
	}

	/* Print an ellipsis to indicate that the buffer has wrapped or
	* is full, and some data was not logged.
	*/
	if (a_buf->e_buf.used_len == a_buf->e_buf.buf_size) {
	do_log_line(log_info, "...\n");
	}

	if (a_buf->e_buf.used_len == 0) {
	return;
	}

	/* Simplest way to print the circular buffer is allocate a second buf
	* of the same size, and memcpy it so it's a simple linear buffer,
	* and then cal print_buf_lines on it */
	if (a_buf->e_buf.read < a_buf->e_buf.write) {
	/* no wrap around, just print it */
	print_buf_lines(log_info, a_buf->e_buf.buf + a_buf->e_buf.read, a_buf->e_buf.used_len);
	} else {
	/* The circular buffer will always have at least 1 byte unused,
	* so by allocating alloc_len here we will have at least
	* 1 byte of space available as required by print_buf_lines().
	*/
	char* nbuf = static_cast<char*>(malloc(a_buf->e_buf.alloc_len));
	if (!nbuf) {
	return;
	}
	int first_chunk_len = a_buf->e_buf.buf_size - a_buf->e_buf.read;
	memcpy(nbuf, a_buf->e_buf.buf + a_buf->e_buf.read, first_chunk_len);
	/* copy second chunk */
	memcpy(nbuf + first_chunk_len, a_buf->e_buf.buf, a_buf->e_buf.write);
	print_buf_lines(log_info, nbuf, first_chunk_len + a_buf->e_buf.write);
	free(nbuf);
	}
	}

	static void signal_handler(int signal_num);

	static void block_signals(sigset_t* oldset) {
	sigset_t blockset;

	sigemptyset(&blockset);
	sigaddset(&blockset, SIGINT);
	sigaddset(&blockset, SIGQUIT);
	sigaddset(&blockset, SIGHUP);
	pthread_sigmask(SIG_BLOCK, &blockset, oldset);
	}

	static void unblock_signals(sigset_t* oldset) {
	pthread_sigmask(SIG_SETMASK, oldset, nullptr);
	}

	static void setup_signal_handlers(pid_t pid) {
	struct sigaction handler = {.sa_handler = signal_handler};

	child_pid = pid;
	sigaction(SIGINT, &handler, &old_int);
	sigaction(SIGQUIT, &handler, &old_quit);
	sigaction(SIGHUP, &handler, &old_hup);
	}

	static void restore_signal_handlers() {
	sigaction(SIGINT, &old_int, nullptr);
	sigaction(SIGQUIT, &old_quit, nullptr);
	sigaction(SIGHUP, &old_hup, nullptr);
	child_pid = 0;
	}

	static void signal_handler(int signal_num) {
	if (child_pid == 0 \|\| kill(child_pid, signal_num) != 0) {
	restore_signal_handlers();
	raise(signal_num);
	}
	}

	static int parent(const char* tag, int parent_read, pid_t pid, int* chld_sts, int log_target,
	bool abbreviated, const char* file_path, bool forward_signals) {
	int status = 0;
	char buffer[4096];
	struct pollfd poll_fds[] = {
	{
	.fd = parent_read,
	.events = POLLIN,
	},
	};
	int rc = 0;
	int fd;

	struct log_info log_info;

	int a = 0; // start index of unprocessed data
	int b = 0; // end index of unprocessed data
	int sz;
	bool found_child = false;
	// There is a very small chance that opening child_ptty in the child will fail, but in this case
	// POLLHUP will not be generated below. Therefore, we use a 1 second timeout for poll() until
	// we receive a message from child_ptty. If this times out, we call waitpid() with WNOHANG to
	// check the status of the child process and exit appropriately if it has terminated.
	bool received_messages = false;
	char tmpbuf[256];

	log_info.btag = basename(tag);
	if (!log_info.btag) {
	log_info.btag = tag;
	}

	if (abbreviated && (log_target == LOG_NONE)) {
	abbreviated = 0;
	}
	if (abbreviated) {
	init_abbr_buf(&log_info.a_buf);
	}

	if (log_target & LOG_KLOG) {
	snprintf(log_info.klog_fmt, sizeof(log_info.klog_fmt), "<6>%.*s: %%s\n", MAX_KLOG_TAG,
	log_info.btag);
	}

	if ((log_target & LOG_FILE) && !file_path) {
	/* No file_path specified, clear the LOG_FILE bit */
	log_target &= ~LOG_FILE;
	}

	if (log_target & LOG_FILE) {
	fd = open(file_path, O_WRONLY \| O_CREAT, 0664);
	if (fd < 0) {
	ERROR("Cannot log to file %s\n", file_path);
	log_target &= ~LOG_FILE;
	} else {
	lseek(fd, 0, SEEK_END);
	log_info.fp = fdopen(fd, "a");
	}
	}

	log_info.log_target = log_target;
	log_info.abbreviated = abbreviated;

	while (!found_child) {
	int timeout = received_messages ? -1 : 1000;
	if (TEMP_FAILURE_RETRY(poll(poll_fds, arraysize(poll_fds), timeout)) < 0) {
	ERROR("poll failed\n");
	rc = -1;
	goto err_poll;
	}

	if (poll_fds[0].revents & POLLIN) {
	received_messages = true;
	sz = TEMP_FAILURE_RETRY(read(parent_read, &buffer[b], sizeof(buffer) - 1 - b));

	sz += b;
	// Log one line at a time
	for (b = 0; b < sz; b++) {
	if (buffer[b] == '\r') {
	if (abbreviated) {
	/* The abbreviated logging code uses newline as
	* the line separator. Lucikly, the pty layer
	* helpfully cooks the output of the command
	* being run and inserts a CR before NL. So
	* I just change it to NL here when doing
	* abbreviated logging.
	*/
	buffer[b] = '\n';
	} else {
	buffer[b] = '\0';
	}
	} else if (buffer[b] == '\n') {
	buffer[b] = '\0';
	log_line(&log_info, &buffer[a], b - a);
	a = b + 1;
	}
	}

	if (a == 0 && b == sizeof(buffer) - 1) {
	// buffer is full, flush
	buffer[b] = '\0';
	log_line(&log_info, &buffer[a], b - a);
	b = 0;
	} else if (a != b) {
	// Keep left-overs
	b -= a;
	memmove(buffer, &buffer[a], b);
	a = 0;
	} else {
	a = 0;
	b = 0;
	}
	}

	if (!received_messages \|\| (poll_fds[0].revents & POLLHUP)) {
	int ret;
	sigset_t oldset;

	if (forward_signals) {
	// Our signal handlers forward these signals to 'child_pid', but waitpid() may reap
	// the child, so we must block these signals until we either 1) conclude that the
	// child is still running or 2) determine the child has been reaped and we have
	// reset the signals to their original disposition.
	block_signals(&oldset);
	}

	int flags = (poll_fds[0].revents & POLLHUP) ? 0 : WNOHANG;
	ret = TEMP_FAILURE_RETRY(waitpid(pid, &status, flags));
	if (ret < 0) {
	rc = errno;
	ALOG(LOG_ERROR, "logwrap", "waitpid failed with %s\n", strerror(errno));
	goto err_waitpid;
	}
	if (ret > 0) {
	found_child = true;
	}

	if (forward_signals) {
	if (found_child) {
	restore_signal_handlers();
	}
	unblock_signals(&oldset);
	}
	}
	}

	if (chld_sts != nullptr) {
	*chld_sts = status;
	} else {
	if (WIFEXITED(status))
	rc = WEXITSTATUS(status);
	else
	rc = -ECHILD;
	}

	// Flush remaining data
	if (a != b) {
	buffer[b] = '\0';
	log_line(&log_info, &buffer[a], b - a);
	}

	/* All the output has been processed, time to dump the abbreviated output */
	if (abbreviated) {
	print_abbr_buf(&log_info);
	}

	if (WIFEXITED(status)) {
	if (WEXITSTATUS(status)) {
	snprintf(tmpbuf, sizeof(tmpbuf), "%s terminated by exit(%d)\n", log_info.btag,
	WEXITSTATUS(status));
	do_log_line(&log_info, tmpbuf);
	}
	} else {
	if (WIFSIGNALED(status)) {
	snprintf(tmpbuf, sizeof(tmpbuf), "%s terminated by signal %d\n", log_info.btag,
	WTERMSIG(status));
	do_log_line(&log_info, tmpbuf);
	} else if (WIFSTOPPED(status)) {
	snprintf(tmpbuf, sizeof(tmpbuf), "%s stopped by signal %d\n", log_info.btag,
	WSTOPSIG(status));
	do_log_line(&log_info, tmpbuf);
	}
	}

	err_waitpid:
	err_poll:
	if (log_target & LOG_FILE) {
	fclose(log_info.fp); /* Also closes underlying fd */
	}
	if (abbreviated) {
	free_abbr_buf(&log_info.a_buf);
	}
	return rc;
	}

	static void child(int argc, const char* const* argv) {
	// create null terminated argv_child array
	char* argv_child[argc + 1];
	memcpy(argv_child, argv, argc * sizeof(char*));
	argv_child[argc] = nullptr;

	if (execvp(argv_child[0], argv_child)) {
	FATAL_CHILD("executing %s failed: %s\n", argv_child[0], strerror(errno));
	}
	}

	int logwrap_fork_execvp(int argc, const char* const* argv, int* status, bool forward_signals,
	int log_target, bool abbreviated, const char* file_path) {
	pid_t pid;
	int parent_ptty;
	sigset_t oldset;
	int rc = 0;

	rc = pthread_mutex_lock(&fd_mutex);
	if (rc) {
	ERROR("failed to lock signal_fd mutex\n");
	goto err_lock;
	}

	/* Use ptty instead of socketpair so that STDOUT is not buffered */
	parent_ptty = TEMP_FAILURE_RETRY(posix_openpt(O_RDWR \| O_CLOEXEC));
	if (parent_ptty < 0) {
	ERROR("Cannot create parent ptty\n");
	rc = -1;
	goto err_open;
	}

	char child_devname[64];
	if (grantpt(parent_ptty) \|\| unlockpt(parent_ptty) \|\|
	ptsname_r(parent_ptty, child_devname, sizeof(child_devname)) != 0) {
	ERROR("Problem with /dev/ptmx\n");
	rc = -1;
	goto err_ptty;
	}

	if (forward_signals) {
	// Block these signals until we have the child pid and our signal handlers set up.
	block_signals(&oldset);
	}

	pid = fork();
	if (pid < 0) {
	ERROR("Failed to fork\n");
	rc = -1;
	goto err_fork;
	} else if (pid == 0) {
	pthread_mutex_unlock(&fd_mutex);
	if (forward_signals) {
	unblock_signals(&oldset);
	}

	setsid();

	int child_ptty = TEMP_FAILURE_RETRY(open(child_devname, O_RDWR \| O_CLOEXEC));
	if (child_ptty < 0) {
	FATAL_CHILD("Cannot open child_ptty: %s\n", strerror(errno));
	}
	close(parent_ptty);

	dup2(child_ptty, 1);
	dup2(child_ptty, 2);
	close(child_ptty);

	child(argc, argv);
	} else {
	if (forward_signals) {
	setup_signal_handlers(pid);
	unblock_signals(&oldset);
	}

	rc = parent(argv[0], parent_ptty, pid, status, log_target, abbreviated, file_path,
	forward_signals);

	if (forward_signals) {
	restore_signal_handlers();
	}
	}

	err_fork:
	if (forward_signals) {
	unblock_signals(&oldset);
	}
	err_ptty:
	close(parent_ptty);
	err_open:
	pthread_mutex_unlock(&fd_mutex);
	err_lock:
	return rc;
	}