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// SPDX-License-Identifier: BSL-1.0
#include <errno.h>
#include <termios.h>
#include <signal.h>
#include <poll.h>
#include <sys/ioctl.h>
#include <stdatomic.h>
#include <string.h>
#include <sys/mman.h>
#include <unistd.h>
#ifndef nullptr
#define nullptr ((void*)0)
#endif
static void output(const char *s) {
(void)!write(2, s, strlen(s)); // ignore error, exiting soon anyway.
}
#define TTYRESCUE_FLAG_ATTACHED (1 << 0)
#define TTYRESCUE_FLAG_TERMIOS_SET (1 << 1)
struct termpaint_ipcseg {
atomic_int active;
atomic_int flags;
long termios_iflag;
long termios_oflag;
long termios_lflag;
long termios_vintr;
long termios_vmin;
long termios_vquit;
long termios_vstart;
long termios_vstop;
long termios_vsusp;
long termios_vtime;
};
int main(int argc, char** argv) {
(void) argc; (void) argv;
struct termpaint_ipcseg *ctlseg = mmap(0, 8048, PROT_READ | PROT_WRITE, MAP_SHARED, 3, 0);
close(3);
if (ctlseg == MAP_FAILED) {
output("ttyrescue: mmap failed. Abort.\n");
return 1;
}
atomic_fetch_or(&ctlseg->flags, TTYRESCUE_FLAG_ATTACHED);
sigset_t fullset;
sigfillset(&fullset);
sigprocmask(SIG_BLOCK, &fullset, NULL);
struct pollfd fds[1] = { { .fd = 0, .events = POLLIN } };
while (1) {
char buf[10];
ssize_t retval;
do {
retval = poll(fds, 1, -1);
} while (retval == -EINTR);
if (retval < 0) {
return 0;
}
retval = read(0, buf, 10);
if (retval == 0) {
// parent crashed
int offset = atomic_load(&ctlseg->active);
if (offset) {
output((char*)ctlseg + offset);
}
if (atomic_load(&ctlseg->flags) & TTYRESCUE_FLAG_TERMIOS_SET) {
if (tcgetpgrp(2) == getpgrp()) {
struct termios tattr;
if (tcgetattr(2, &tattr) >= 0) {
tattr.c_iflag = (tcflag_t)ctlseg->termios_iflag;
tattr.c_oflag = (tcflag_t)ctlseg->termios_oflag;
tattr.c_lflag = (tcflag_t)ctlseg->termios_lflag;
tattr.c_cc[VINTR] = (cc_t)ctlseg->termios_vintr;
tattr.c_cc[VMIN] = (cc_t)ctlseg->termios_vmin;
tattr.c_cc[VQUIT] = (cc_t)ctlseg->termios_vquit;
tattr.c_cc[VSTART] = (cc_t)ctlseg->termios_vstart;
tattr.c_cc[VSTOP] = (cc_t)ctlseg->termios_vstop;
tattr.c_cc[VSUSP] = (cc_t)ctlseg->termios_vsusp;
tattr.c_cc[VTIME] = (cc_t)ctlseg->termios_vtime;
tcsetattr(2, TCSAFLUSH, &tattr);
}
}
}
return 0;
}
if (retval < 0 && (errno == EAGAIN || errno == EWOULDBLOCK)) {
continue;
}
if (retval > 0) {
// clean close of parent
return 0;
}
}
return 0;
}
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