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// SPDX-License-Identifier: BSL-1.0
#include <errno.h>
#include <termios.h>
#include <signal.h>
#include <stdatomic.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/select.h>
#include <sys/shm.h>
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
#ifndef nullptr
#define nullptr ((void*)0)
#endif
static char *restore;
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;
};
#ifndef TERMPAINT_RESCUE_EMBEDDED
int main(int argc, char** argv) {
(void) argc; (void) argv;
struct termpaint_ipcseg *ctlseg = nullptr;
#else
int termpaintp_rescue_embedded(struct termpaint_ipcseg *ctlseg) {
#endif
restore = getenv("TTYRESCUE_RESTORE");
if (!restore || *restore==0) {
output("This is an internal helper to ensure that the terminal is properly restored.\n");
output("There should be no need to call this manually.\n");
return 0;
}
int res;
res = isatty(0);
if (res || (errno != EINVAL && errno != ENOTTY && errno != EOPNOTSUPP)) {
output("Invalid invocation\n");
return 1;
}
res = fcntl(0, F_GETFL);
if (res == -1 || !(res & O_NONBLOCK)) {
output("Invalid invocation\n");
return 1;
}
res = isatty(1);
if (res || errno != EBADF) {
output("Invalid invocation\n");
return 1;
}
#ifndef TERMPAINT_RESCUE_EMBEDDED
if (getenv("TTYRESCUE_SHMFD")) {
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);
}
#endif
if (getenv("TTYRESCUE_SYSVSHMID")) {
#ifndef TERMPAINT_RESCUE_EMBEDDED
char *var = getenv("TTYRESCUE_SYSVSHMID");
char *end;
errno = 0;
long int val = strtol(var, &end, 10);
if (*end != '\0' || errno != 0) {
output("ttyrescue: Can't parse TTYRESCUE_SYSVSHMID. Abort.\n");
return 1;
}
ctlseg = shmat(val, nullptr, 0);
if (ctlseg == (void*)-1) {
output("ttyrescue: shmat failed. Abort.\n");
return 1;
}
atomic_fetch_or(&ctlseg->flags, TTYRESCUE_FLAG_ATTACHED);
#endif
(void)!write(0, "x", 1); // nothing much we can do about an error here, likely read below will error too and exit anyway.
}
sigset_t fullset;
sigfillset(&fullset);
sigprocmask(SIG_BLOCK, &fullset, NULL);
fd_set rfds;
fd_set efds;
FD_ZERO(&rfds);
FD_SET(0, &rfds);
FD_ZERO(&efds);
FD_SET(0, &efds);
while (1) {
char buf[10];
int retval = select(1, &rfds, NULL, &efds, NULL);
if (retval < 0) {
return 0;
}
retval = read(0, buf, 10);
if (retval == 0) {
// parent crashed
int offset = 0;
if (ctlseg) {
offset = atomic_load(&ctlseg->active);
}
if (offset) {
output((char*)ctlseg offset);
} else {
output(restore);
}
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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