script: use signalfd() to catch signals

This is incomplete change.  Working command requires the subsequent
select() to poll() change as well.

Addresses: https://github.com/karelzak/util-linux/pull/62
CC: Wolfgang Richter <wolf@cs.cmu.edu>
CC: Ruediger Meier <ruediger.meier@ga-group.nl>
Signed-off-by: Sami Kerola <kerolasa@iki.fi>

diff --git a/term-utils/script.c b/term-utils/script.c
index acfa2fb51a762125c0ee165af1d628e3a2502a13..12abdd67431dbbfc89112724eecbe274579cd5b3 100644 (file)
--- a/term-utils/script.c
+++ b/term-utils/script.c
@@ -63,6 +63,8 @@
 #include <stddef.h>
 #include <sys/wait.h>
 #include <poll.h>
+#include <sys/signalfd.h>
+#include <assert.h>
 
 #include "closestream.h"
 #include "nls.h"
@@ -106,8 +108,8 @@ struct script_control {
         isterm:1,              /* is child process running as terminal */
         resized:1,             /* has terminal been resized */
         die:1;                 /* terminate program */
-       sigset_t block_mask;    /* signals that are blocked */
-       sigset_t unblock_mask;  /* original signal mask */
+       sigset_t sigset;        /* catch SIGCHLD and SIGWINCH with signalfd() */
+       int sigfd;              /* file descriptor for signalfd() */
 };
 struct script_control *gctl;   /* global control structure, used in signal handlers */
 
@@ -265,16 +267,13 @@ static void doinput(struct script_control *ctl)
 
        FD_ZERO(&readfds);
 
-       /* block SIGCHLD */
-       sigprocmask(SIG_SETMASK, &ctl->block_mask, &ctl->unblock_mask);
-
        while (!ctl->die) {
                FD_SET(STDIN_FILENO, &readfds);
 
                errno = 0;
                /* wait for input or signal (including SIGCHLD) */
                if ((cc = pselect(STDIN_FILENO + 1, &readfds, NULL, NULL, NULL,
-                                 &ctl->unblock_mask)) > 0) {
+                                 NULL)) > 0) {
 
                        if ((cc = read(STDIN_FILENO, ibuf, BUFSIZ)) > 0) {
                                if (write_all(ctl->master, ibuf, cc)) {
@@ -298,9 +297,6 @@ static void doinput(struct script_control *ctl)
                }
        }
 
-       /* unblock SIGCHLD */
-       sigprocmask(SIG_SETMASK, &ctl->unblock_mask, NULL);
-
        /* To be sure that we don't miss any data */
        wait_for_empty_fd(ctl, ctl->slave);
        wait_for_empty_fd(ctl, ctl->master);
@@ -369,29 +365,24 @@ static void dooutput(struct script_control *ctl)
        do {
                if (ctl->die || errsv == EINTR) {
                        struct pollfd fds[] = {
+                               {.fd = ctl->sigfd, .events = POLLIN | POLLERR | POLLHUP},
                                {.fd = ctl->master, .events = POLLIN}
                        };
                        if (poll(fds, 1, 50) <= 0)
                                break;
                }
 
-               /* block SIGCHLD */
-               sigprocmask(SIG_SETMASK, &ctl->block_mask, &ctl->unblock_mask);
-
                FD_SET(ctl->master, &readfds);
                errno = 0;
 
                /* wait for input or signal (including SIGCHLD) */
                if ((cc = pselect(ctl->master + 1, &readfds, NULL, NULL, NULL,
-                                 &ctl->unblock_mask)) > 0) {
+                                 NULL)) > 0) {
 
                        cc = read(ctl->master, obuf, sizeof(obuf));
                }
                errsv = errno;
 
-               /* unblock SIGCHLD */
-               sigprocmask(SIG_SETMASK, &ctl->unblock_mask, NULL);
-
                if (ctl->tflg)
                        gettimeofday(&tv, NULL);
 
@@ -582,7 +573,6 @@ int main(int argc, char **argv)
                .master = -1,
                0
        };
-       struct sigaction sa;
        int ch;
 
        enum { FORCE_OPTION = CHAR_MAX + 1 };
@@ -670,20 +660,16 @@ int main(int argc, char **argv)
 #ifdef HAVE_LIBUTEMPTER
        utempter_add_record(ctl.master, NULL);
 #endif
-       /* setup SIGCHLD handler */
-       sigemptyset(&sa.sa_mask);
-       sa.sa_flags = 0;
-       sa.sa_handler = sig_finish;
-       sigaction(SIGCHLD, &sa, NULL);
-
-       /* init mask for SIGCHLD */
-       sigprocmask(SIG_SETMASK, NULL, &ctl.block_mask);
-       sigaddset(&ctl.block_mask, SIGCHLD);
+       /* setup signal handler */
+       assert(sigemptyset(&ctl.sigset) == 0);
+       assert(sigaddset(&ctl.sigset, SIGCHLD) == 0);
+       assert(sigaddset(&ctl.sigset, SIGWINCH) == 0);
+       assert(sigprocmask(SIG_BLOCK, &ctl.sigset, NULL) == 0);
+       if ((ctl.sigfd = signalfd(-1, &ctl.sigset, 0)) < 0)
+               err(EXIT_FAILURE, _("cannot set signal handler"));
 
        fflush(stdout);
-       sigprocmask(SIG_SETMASK, &ctl.block_mask, &ctl.unblock_mask);
        ctl.child = fork();
-       sigprocmask(SIG_SETMASK, &ctl.unblock_mask, NULL);
 
        if (ctl.child < 0) {
                warn(_("fork failed"));
@@ -691,9 +677,7 @@ int main(int argc, char **argv)
        }
        if (ctl.child == 0) {
 
-               sigprocmask(SIG_SETMASK, &ctl.block_mask, NULL);
                ctl.subchild = ctl.child = fork();
-               sigprocmask(SIG_SETMASK, &ctl.unblock_mask, NULL);
 
                if (ctl.child < 0) {
                        warn(_("fork failed"));
@@ -703,9 +687,6 @@ int main(int argc, char **argv)
                        dooutput(&ctl);
                else
                        doshell(&ctl);
-       } else {
-               sa.sa_handler = resize;
-               sigaction(SIGWINCH, &sa, NULL);
        }
        doinput(&ctl);