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https://github.com/fish-shell/fish-shell.git
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340c8490f6
fish's handling of terminal sizes is currently rather twisted. The
essential problem is that the terminal size may change at any point from a
SIGWINCH, and common_get_{width,height} may modify it and post variable
change events from arbitrary locations.
Tighten up the semantics. Assign responsibility for managing the tty size
to a new class, `termsize_container_t`. Rationalize locking and reentrancy.
Explicitly nail down the relationship between $COLUMNS/$LINES and the tty
size. The new semantics are: whatever changed most recently takes
precendence.
418 lines
12 KiB
C++
418 lines
12 KiB
C++
// The library for various signal related issues.
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#include "config.h" // IWYU pragma: keep
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#include <errno.h>
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#include <signal.h>
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#include <stdio.h>
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#ifdef HAVE_SIGINFO_H
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#include <siginfo.h>
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#endif
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#include <pthread.h>
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#include "common.h"
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#include "event.h"
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#include "fallback.h" // IWYU pragma: keep
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#include "parser.h"
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#include "proc.h"
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#include "reader.h"
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#include "signal.h"
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#include "termsize.h"
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#include "topic_monitor.h"
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#include "wutil.h" // IWYU pragma: keep
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/// Struct describing an entry for the lookup table used to convert between signal names and signal
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/// ids, etc.
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struct lookup_entry {
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/// Signal id.
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int signal;
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/// Signal name.
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const wchar_t *name;
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/// Signal description.
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const wchar_t *desc;
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};
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/// Lookup table used to convert between signal names and signal ids, etc.
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static const struct lookup_entry signal_table[] = {
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#ifdef SIGHUP
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{SIGHUP, L"SIGHUP", N_(L"Terminal hung up")},
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#endif
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#ifdef SIGINT
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{SIGINT, L"SIGINT", N_(L"Quit request from job control (^C)")},
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#endif
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#ifdef SIGQUIT
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{SIGQUIT, L"SIGQUIT", N_(L"Quit request from job control with core dump (^\\)")},
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#endif
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#ifdef SIGILL
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{SIGILL, L"SIGILL", N_(L"Illegal instruction")},
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#endif
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#ifdef SIGTRAP
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{SIGTRAP, L"SIGTRAP", N_(L"Trace or breakpoint trap")},
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#endif
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#ifdef SIGABRT
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{SIGABRT, L"SIGABRT", N_(L"Abort")},
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#endif
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#ifdef SIGBUS
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{SIGBUS, L"SIGBUS", N_(L"Misaligned address error")},
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#endif
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#ifdef SIGFPE
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{SIGFPE, L"SIGFPE", N_(L"Floating point exception")},
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#endif
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#ifdef SIGKILL
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{SIGKILL, L"SIGKILL", N_(L"Forced quit")},
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#endif
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#ifdef SIGUSR1
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{SIGUSR1, L"SIGUSR1", N_(L"User defined signal 1")},
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#endif
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#ifdef SIGUSR2
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{SIGUSR2, L"SIGUSR2", N_(L"User defined signal 2")},
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#endif
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#ifdef SIGSEGV
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{SIGSEGV, L"SIGSEGV", N_(L"Address boundary error")},
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#endif
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#ifdef SIGPIPE
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{SIGPIPE, L"SIGPIPE", N_(L"Broken pipe")},
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#endif
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#ifdef SIGALRM
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{SIGALRM, L"SIGALRM", N_(L"Timer expired")},
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#endif
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#ifdef SIGTERM
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{SIGTERM, L"SIGTERM", N_(L"Polite quit request")},
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#endif
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#ifdef SIGCHLD
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{SIGCHLD, L"SIGCHLD", N_(L"Child process status changed")},
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#endif
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#ifdef SIGCONT
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{SIGCONT, L"SIGCONT", N_(L"Continue previously stopped process")},
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#endif
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#ifdef SIGSTOP
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{SIGSTOP, L"SIGSTOP", N_(L"Forced stop")},
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#endif
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#ifdef SIGTSTP
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{SIGTSTP, L"SIGTSTP", N_(L"Stop request from job control (^Z)")},
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#endif
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#ifdef SIGTTIN
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{SIGTTIN, L"SIGTTIN", N_(L"Stop from terminal input")},
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#endif
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#ifdef SIGTTOU
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{SIGTTOU, L"SIGTTOU", N_(L"Stop from terminal output")},
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#endif
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#ifdef SIGURG
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{SIGURG, L"SIGURG", N_(L"Urgent socket condition")},
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#endif
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#ifdef SIGXCPU
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{SIGXCPU, L"SIGXCPU", N_(L"CPU time limit exceeded")},
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#endif
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#ifdef SIGXFSZ
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{SIGXFSZ, L"SIGXFSZ", N_(L"File size limit exceeded")},
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#endif
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#ifdef SIGVTALRM
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{SIGVTALRM, L"SIGVTALRM", N_(L"Virtual timer expired")},
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#endif
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#ifdef SIGPROF
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{SIGPROF, L"SIGPROF", N_(L"Profiling timer expired")},
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#endif
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#ifdef SIGWINCH
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{SIGWINCH, L"SIGWINCH", N_(L"Window size change")},
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#endif
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#ifdef SIGWIND
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{SIGWIND, L"SIGWIND", N_(L"Window size change")},
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#endif
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#ifdef SIGIO
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{SIGIO, L"SIGIO", N_(L"I/O on asynchronous file descriptor is possible")},
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#endif
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#ifdef SIGPWR
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{SIGPWR, L"SIGPWR", N_(L"Power failure")},
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#endif
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#ifdef SIGSYS
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{SIGSYS, L"SIGSYS", N_(L"Bad system call")},
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#endif
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#ifdef SIGINFO
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{SIGINFO, L"SIGINFO", N_(L"Information request")},
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#endif
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#ifdef SIGSTKFLT
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{SIGSTKFLT, L"SISTKFLT", N_(L"Stack fault")},
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#endif
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#ifdef SIGEMT
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{SIGEMT, L"SIGEMT", N_(L"Emulator trap")},
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#endif
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#ifdef SIGIOT
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{SIGIOT, L"SIGIOT", N_(L"Abort (Alias for SIGABRT)")},
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#endif
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#ifdef SIGUNUSED
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{SIGUNUSED, L"SIGUNUSED", N_(L"Unused signal")},
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#endif
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};
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/// Test if \c name is a string describing the signal named \c canonical.
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static int match_signal_name(const wchar_t *canonical, const wchar_t *name) {
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if (wcsncasecmp(name, L"sig", 3) == 0) name += 3;
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return wcscasecmp(canonical + 3, name) == 0;
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}
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int wcs2sig(const wchar_t *str) {
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for (const auto &data : signal_table) {
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if (match_signal_name(data.name, str)) {
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return data.signal;
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}
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}
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int res = fish_wcstoi(str);
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if (errno || res < 0) return -1;
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return res;
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}
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const wchar_t *sig2wcs(int sig) {
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for (const auto &data : signal_table) {
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if (data.signal == sig) {
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return data.name;
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}
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}
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return _(L"Unknown");
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}
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const wchar_t *signal_get_desc(int sig) {
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for (const auto &data : signal_table) {
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if (data.signal == sig) {
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return _(data.desc);
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}
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}
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return _(L"Unknown");
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}
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/// Store the "main" pid. This allows us to reliably determine if we are in a forked child.
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static const pid_t s_main_pid = getpid();
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/// It's possible that we receive a signal after we have forked, but before we have reset the signal
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/// handlers (or even run the pthread_atfork calls). In that event we will do something dumb like
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/// swallow SIGINT. Ensure that doesn't happen. Check if we are the main fish process; if not reset
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/// and re-raise the signal. \return whether we re-raised the signal.
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static bool reraise_if_forked_child(int sig) {
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// Don't use is_forked_child, that relies on atfork handlers which maybe have not run yet.
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if (getpid() == s_main_pid) {
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return false;
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}
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signal(sig, SIG_DFL);
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raise(sig);
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return true;
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}
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/// The single signal handler. By centralizing signal handling we ensure that we can never install
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/// the "wrong" signal handler (see #5969).
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static void fish_signal_handler(int sig, siginfo_t *info, void *context) {
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UNUSED(info);
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UNUSED(context);
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// Check if we are a forked child.
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if (reraise_if_forked_child(sig)) {
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return;
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}
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// Check if fish script cares about this.
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const bool observed = event_is_signal_observed(sig);
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if (observed) {
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event_enqueue_signal(sig);
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}
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// Do some signal-specific stuff.
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switch (sig) {
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#ifdef SIGWINCH
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case SIGWINCH:
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/// Respond to a winch signal by invalidating the terminal size.
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termsize_container_t::handle_winch();
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common_handle_winch(sig);
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break;
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#endif
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case SIGHUP:
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/// Respond to a hup signal by exiting, unless it is caught by a shellscript function,
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/// in which case we do nothing.
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if (!observed) {
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reader_force_exit();
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}
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topic_monitor_t::principal().post(topic_t::sighupint);
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break;
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case SIGTERM:
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/// Handle sigterm. The only thing we do is restore the front process ID, then die.
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restore_term_foreground_process_group_for_exit();
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signal(SIGTERM, SIG_DFL);
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raise(SIGTERM);
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break;
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case SIGINT:
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/// Interactive mode ^C handler. Respond to int signal by setting interrupted-flag and
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/// stopping all loops and conditionals.
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reader_handle_sigint();
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topic_monitor_t::principal().post(topic_t::sighupint);
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break;
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case SIGCHLD:
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// A child process stopped or exited.
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topic_monitor_t::principal().post(topic_t::sigchld);
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break;
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case SIGALRM:
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// We have a sigalarm handler that does nothing. This is used in the signal torture
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// test, to verify that we behave correctly when receiving lots of irrelevant signals.
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break;
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}
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}
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void signal_reset_handlers() {
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struct sigaction act;
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sigemptyset(&act.sa_mask);
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act.sa_flags = 0;
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act.sa_handler = SIG_DFL;
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for (const auto &data : signal_table) {
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if (data.signal == SIGHUP) {
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struct sigaction oact;
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sigaction(SIGHUP, nullptr, &oact);
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if (oact.sa_handler == SIG_IGN) continue;
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}
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sigaction(data.signal, &act, nullptr);
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}
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}
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static void set_interactive_handlers() {
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struct sigaction act, oact;
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act.sa_flags = 0;
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oact.sa_flags = 0;
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sigemptyset(&act.sa_mask);
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// Interactive mode. Ignore interactive signals. We are a shell, we know what is best for
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// the user.
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act.sa_handler = SIG_IGN;
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sigaction(SIGTSTP, &act, nullptr);
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sigaction(SIGTTOU, &act, nullptr);
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// We don't ignore SIGTTIN because we might send it to ourself.
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act.sa_sigaction = &fish_signal_handler;
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act.sa_flags = SA_SIGINFO;
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sigaction(SIGTTIN, &act, nullptr);
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// SIGTERM restores the terminal controlling process before dying.
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act.sa_sigaction = &fish_signal_handler;
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act.sa_flags = SA_SIGINFO;
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sigaction(SIGTERM, &act, nullptr);
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sigaction(SIGHUP, nullptr, &oact);
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if (oact.sa_handler == SIG_DFL) {
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act.sa_sigaction = &fish_signal_handler;
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act.sa_flags = SA_SIGINFO;
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sigaction(SIGHUP, &act, nullptr);
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}
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// SIGALARM as part of our signal torture test
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act.sa_sigaction = &fish_signal_handler;
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act.sa_flags = SA_SIGINFO;
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sigaction(SIGALRM, &act, nullptr);
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#ifdef SIGWINCH
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act.sa_sigaction = &fish_signal_handler;
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act.sa_flags = SA_SIGINFO;
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sigaction(SIGWINCH, &act, nullptr);
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#endif
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}
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/// Sets up appropriate signal handlers.
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void signal_set_handlers(bool interactive) {
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struct sigaction act;
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act.sa_flags = 0;
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sigemptyset(&act.sa_mask);
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// Ignore SIGPIPE. We'll detect failed writes and deal with them appropriately. We don't want
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// this signal interrupting other syscalls or terminating us.
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act.sa_sigaction = nullptr;
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act.sa_handler = SIG_IGN;
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sigaction(SIGPIPE, &act, nullptr);
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// Ignore SIGQUIT.
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act.sa_handler = SIG_IGN;
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sigaction(SIGQUIT, &act, nullptr);
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// Apply our SIGINT handler.
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act.sa_sigaction = &fish_signal_handler;
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act.sa_flags = SA_SIGINFO;
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sigaction(SIGINT, &act, nullptr);
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// Whether or not we're interactive we want SIGCHLD to not interrupt restartable syscalls.
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act.sa_flags = SA_SIGINFO;
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act.sa_sigaction = &fish_signal_handler;
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act.sa_flags = SA_SIGINFO | SA_RESTART;
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if (sigaction(SIGCHLD, &act, nullptr)) {
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wperror(L"sigaction");
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FATAL_EXIT();
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}
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if (interactive) {
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set_interactive_handlers();
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}
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}
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void signal_set_handlers_once(bool interactive) {
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static std::once_flag s_noninter_once;
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std::call_once(s_noninter_once, signal_set_handlers, false);
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static std::once_flag s_inter_once;
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if (interactive) std::call_once(s_inter_once, set_interactive_handlers);
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}
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void signal_handle(int sig) {
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struct sigaction act;
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// These should always be handled.
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if ((sig == SIGINT) || (sig == SIGQUIT) || (sig == SIGTSTP) || (sig == SIGTTIN) ||
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(sig == SIGTTOU) || (sig == SIGCHLD))
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return;
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act.sa_flags = 0;
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sigemptyset(&act.sa_mask);
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act.sa_flags = SA_SIGINFO;
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act.sa_sigaction = &fish_signal_handler;
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sigaction(sig, &act, nullptr);
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}
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void get_signals_with_handlers(sigset_t *set) {
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sigemptyset(set);
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for (const auto &data : signal_table) {
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struct sigaction act = {};
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sigaction(data.signal, nullptr, &act);
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// If SIGHUP is being ignored (e.g., because were were run via `nohup`) don't reset it.
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// We don't special case other signals because if they're being ignored that shouldn't
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// affect processes we spawn. They should get the default behavior for those signals.
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if (data.signal == SIGHUP && act.sa_handler == SIG_IGN) continue;
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if (act.sa_handler != SIG_DFL) sigaddset(set, data.signal);
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}
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}
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/// Ensure we did not inherit any blocked signals. See issue #3964.
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void signal_unblock_all() {
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sigset_t iset;
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sigemptyset(&iset);
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sigprocmask(SIG_SETMASK, &iset, nullptr);
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}
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sigint_checker_t::sigint_checker_t() {
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// Call check() to update our generation.
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check();
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}
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bool sigint_checker_t::check() {
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auto &tm = topic_monitor_t::principal();
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generation_t gen = tm.generation_for_topic(topic_t::sighupint);
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bool changed = this->gen_ != gen;
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this->gen_ = gen;
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return changed;
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}
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void sigint_checker_t::wait() const {
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auto &tm = topic_monitor_t::principal();
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generation_list_t gens{};
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gens[topic_t::sighupint] = this->gen_;
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tm.check(&gens, {topic_t::sighupint}, true /* wait */);
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}
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