logwrapper: switch to signal handlers for SIGCHLD
Switch to a signal handler to monitor SIGCHLD. Also, clean up the exit path and log a warning when the previous SIGCHLD sigaction is not default or ignore. Change-Id: I7ef7daabee18d80e9e82fba3943cf1d03b504ae3
This commit is contained in:
Rom Lemarchand
parent
fa341f5b66
commit
0cc2cab6af
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@ -16,7 +16,7 @@
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#include <string.h>
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#include <sys/types.h>
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#include <sys/signalfd.h>
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#include <sys/socket.h>
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#include <signal.h>
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#include <poll.h>
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#include <sys/wait.h>
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@ -26,6 +26,7 @@
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#include <errno.h>
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#include <fcntl.h>
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#include <libgen.h>
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#include <stdbool.h>
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#include <logwrap/logwrap.h>
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#include "private/android_filesystem_config.h"
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@ -33,83 +34,104 @@
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#define ARRAY_SIZE(x) (sizeof(x) / sizeof(*(x)))
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static int fatal(const char *msg) {
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static int signal_fd_write;
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static void fatal(const char *msg) {
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fprintf(stderr, "%s", msg);
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ALOG(LOG_ERROR, "logwrapper", "%s", msg);
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return -1;
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}
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static int parent(const char *tag, int parent_read, int signal_fd, pid_t pid,
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int *chld_sts) {
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int status;
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int status = 0;
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char buffer[4096];
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struct pollfd poll_fds[] = {
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[0] = {
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.fd = parent_read,
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.events = POLLIN,
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},
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[1] = {
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.fd = signal_fd,
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.events = POLLIN,
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},
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[1] = {
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.fd = parent_read,
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.events = POLLIN,
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},
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};
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int rc = 0;
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sigset_t chldset;
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int a = 0; // start index of unprocessed data
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int b = 0; // end index of unprocessed data
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int sz;
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bool remote_hung = false;
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bool found_child = false;
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char *btag = basename(tag);
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if (!btag) btag = (char*) tag;
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while (1) {
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if (poll(poll_fds, ARRAY_SIZE(poll_fds), -1) <= 0) {
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return fatal("poll failed\n");
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sigemptyset(&chldset);
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sigaddset(&chldset, SIGCHLD);
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sigprocmask(SIG_UNBLOCK, &chldset, NULL);
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while (!found_child) {
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if (poll(poll_fds, remote_hung ? 1 : 2, -1) < 0) {
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if (errno == EINTR)
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continue;
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fatal("poll failed\n");
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rc = -1;
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goto err_poll;
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}
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if (poll_fds[0].revents & POLLIN) {
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sz = read(parent_read, &buffer[b], sizeof(buffer) - 1 - b);
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if (!remote_hung) {
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if (poll_fds[1].revents & POLLIN) {
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sz = read(parent_read, &buffer[b], sizeof(buffer) - 1 - b);
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sz += b;
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// Log one line at a time
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for (b = 0; b < sz; b++) {
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if (buffer[b] == '\r') {
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buffer[b] = '\0';
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} else if (buffer[b] == '\n') {
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sz += b;
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// Log one line at a time
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for (b = 0; b < sz; b++) {
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if (buffer[b] == '\r') {
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buffer[b] = '\0';
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} else if (buffer[b] == '\n') {
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buffer[b] = '\0';
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ALOG(LOG_INFO, btag, "%s", &buffer[a]);
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a = b + 1;
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}
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}
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if (a == 0 && b == sizeof(buffer) - 1) {
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// buffer is full, flush
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buffer[b] = '\0';
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ALOG(LOG_INFO, btag, "%s", &buffer[a]);
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a = b + 1;
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b = 0;
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} else if (a != b) {
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// Keep left-overs
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b -= a;
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memmove(buffer, &buffer[a], b);
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a = 0;
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} else {
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a = 0;
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b = 0;
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}
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}
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if (a == 0 && b == sizeof(buffer) - 1) {
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// buffer is full, flush
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buffer[b] = '\0';
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ALOG(LOG_INFO, btag, "%s", &buffer[a]);
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b = 0;
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} else if (a != b) {
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// Keep left-overs
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b -= a;
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memmove(buffer, &buffer[a], b);
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a = 0;
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} else {
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a = 0;
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b = 0;
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if (poll_fds[1].revents & POLLHUP) {
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remote_hung = true;
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}
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}
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if (poll_fds[1].revents & POLLIN) {
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struct signalfd_siginfo sfd_info;
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pid_t wpid;
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if (poll_fds[0].revents & POLLIN) {
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char tmp[32];
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int ret;
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// Clear all pending signals before reading the child's status
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while (read(signal_fd, &sfd_info, sizeof(sfd_info)) > 0) {
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if ((pid_t)sfd_info.ssi_pid != pid)
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ALOG(LOG_WARN, "logwrapper", "cleared SIGCHLD for pid %u\n",
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sfd_info.ssi_pid);
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read(signal_fd, tmp, sizeof(tmp));
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while (!found_child) {
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do {
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ret = waitpid(-1, &status, WNOHANG);
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} while (ret < 0 && errno == EINTR);
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if (ret <= 0)
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break;
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found_child = (pid == ret);
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}
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wpid = waitpid(pid, &status, WNOHANG);
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if (wpid > 0)
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break;
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}
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}
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@ -121,19 +143,20 @@ static int parent(const char *tag, int parent_read, int signal_fd, pid_t pid,
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if (WIFEXITED(status)) {
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if (WEXITSTATUS(status))
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ALOG(LOG_INFO, "logwrapper", "%s terminated by exit(%d)", tag,
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ALOG(LOG_INFO, "logwrapper", "%s terminated by exit(%d)", btag,
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WEXITSTATUS(status));
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} else if (WIFSIGNALED(status)) {
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ALOG(LOG_INFO, "logwrapper", "%s terminated by signal %d", tag,
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ALOG(LOG_INFO, "logwrapper", "%s terminated by signal %d", btag,
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WTERMSIG(status));
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} else if (WIFSTOPPED(status)) {
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ALOG(LOG_INFO, "logwrapper", "%s stopped by signal %d", tag,
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ALOG(LOG_INFO, "logwrapper", "%s stopped by signal %d", btag,
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WSTOPSIG(status));
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}
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if (chld_sts != NULL)
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*chld_sts = status;
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return 0;
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err_poll:
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return rc;
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}
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static void child(int argc, char* argv[]) {
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@ -149,40 +172,54 @@ static void child(int argc, char* argv[]) {
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}
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}
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void sigchld_handler(int sig) {
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write(signal_fd_write, &sig, 1);
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}
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int logwrap(int argc, char* argv[], int *status) {
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pid_t pid;
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int parent_ptty;
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int child_ptty;
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char *child_devname = NULL;
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sigset_t chldset;
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struct sigaction chldact;
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struct sigaction oldchldact;
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sigset_t blockset;
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sigset_t oldset;
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int sockets[2];
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int rc = 0;
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/* Use ptty instead of socketpair so that STDOUT is not buffered */
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parent_ptty = open("/dev/ptmx", O_RDWR);
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if (parent_ptty < 0) {
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return fatal("Cannot create parent ptty\n");
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fatal("Cannot create parent ptty\n");
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rc = -1;
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goto err_open;
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}
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if (grantpt(parent_ptty) || unlockpt(parent_ptty) ||
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((child_devname = (char*)ptsname(parent_ptty)) == 0)) {
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return fatal("Problem with /dev/ptmx\n");
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fatal("Problem with /dev/ptmx\n");
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rc = -1;
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goto err_ptty;
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}
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sigemptyset(&chldset);
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sigaddset(&chldset, SIGCHLD);
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sigprocmask(SIG_BLOCK, &chldset, NULL);
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sigemptyset(&blockset);
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sigaddset(&blockset, SIGCHLD);
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sigprocmask(SIG_BLOCK, &blockset, &oldset);
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pid = fork();
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if (pid < 0) {
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close(parent_ptty);
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sigprocmask(SIG_UNBLOCK, &chldset, NULL);
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return fatal("Failed to fork\n");
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fatal("Failed to fork\n");
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rc = -1;
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goto err_fork;
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} else if (pid == 0) {
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sigprocmask(SIG_SETMASK, &oldset, NULL);
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close(parent_ptty);
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sigprocmask(SIG_UNBLOCK, &chldset, NULL);
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child_ptty = open(child_devname, O_RDWR);
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if (child_ptty < 0) {
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return fatal("Problem with child ptty\n");
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fatal("Problem with child ptty\n");
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return -1;
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}
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// redirect stdout and stderr
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@ -191,35 +228,57 @@ int logwrap(int argc, char* argv[], int *status) {
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close(child_ptty);
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child(argc - 1, &argv[1]);
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return fatal("This should never happen\n");
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fatal("This should never happen\n");
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return -1;
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} else {
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int rc;
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int fd;
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memset(&chldact, 0, sizeof(chldact));
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chldact.sa_handler = sigchld_handler;
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chldact.sa_flags = SA_NOCLDSTOP;
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fd = signalfd(-1, &chldset, SFD_NONBLOCK);
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if (fd == -1) {
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sigaction(SIGCHLD, &chldact, &oldchldact);
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if ((!(oldchldact.sa_flags & SA_SIGINFO) &&
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oldchldact.sa_handler != SIG_DFL &&
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oldchldact.sa_handler != SIG_IGN) ||
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((oldchldact.sa_flags & SA_SIGINFO) &&
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oldchldact.sa_sigaction != NULL)) {
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ALOG(LOG_WARN, "logwrapper", "logwrap replaced the SIGCHLD "
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"handler and might cause interaction issues");
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}
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rc = socketpair(AF_UNIX, SOCK_STREAM, 0, sockets);
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if (rc == -1) {
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char msg[40];
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snprintf(msg, sizeof(msg), "signalfd failed: %d\n", errno);
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snprintf(msg, sizeof(msg), "socketpair failed: %d\n", errno);
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close(parent_ptty);
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sigprocmask(SIG_UNBLOCK, &chldset, NULL);
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return fatal(msg);
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fatal(msg);
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goto err_socketpair;
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}
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fcntl(sockets[0], F_SETFD, FD_CLOEXEC);
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fcntl(sockets[0], F_SETFL, O_NONBLOCK);
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fcntl(sockets[1], F_SETFD, FD_CLOEXEC);
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fcntl(sockets[1], F_SETFL, O_NONBLOCK);
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signal_fd_write = sockets[0];
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// switch user and group to "log"
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// this may fail if we are not root,
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// but in that case switching user/group is unnecessary
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setgid(AID_LOG);
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setuid(AID_LOG);
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rc = parent(argv[1], parent_ptty, fd, pid, status);
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close(parent_ptty);
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close(fd);
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sigprocmask(SIG_UNBLOCK, &chldset, NULL);
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return rc;
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rc = parent(argv[1], parent_ptty, sockets[1], pid, status);
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}
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close(sockets[0]);
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close(sockets[1]);
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err_socketpair:
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sigaction(SIGCHLD, &oldchldact, NULL);
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err_fork:
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sigprocmask(SIG_SETMASK, &oldset, NULL);
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err_ptty:
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close(parent_ptty);
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err_open:
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return rc;
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}
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