signal.cpp

/** \file signal.c

The library for various signal related issues

*/

#include "config.h"


#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <signal.h>
#include <dirent.h>
#include <unistd.h>
#include <errno.h>

#ifdef HAVE_SIGINFO_H
#include <siginfo.h>
#endif

#include "common.h"
#include "fallback.h"
#include "util.h"

#include "wutil.h"
#include "signal.h"
#include "event.h"
#include "reader.h"
#include "proc.h"


/**
   Struct describing an entry for the lookup table used to convert
   between signal names and signal ids, etc.
*/
struct lookup_entry
{
    /**
       Signal id
    */
    int signal;
    /**
       Signal name
    */
    const wchar_t *name;
    /**
       Signal description
    */
    const wchar_t *desc;
};

/**
   The number of signal blocks in place. Increased by signal_block, decreased by signal_unblock.
*/
static int block_count=0;


/**
   Lookup table used to convert between signal names and signal ids,
   etc.
*/
static const struct lookup_entry lookup[] =
{
#ifdef SIGHUP
    {
        SIGHUP,
        L"SIGHUP",
        N_(L"Terminal hung up")
    }
    ,
#endif
#ifdef SIGINT
    {
        SIGINT,
        L"SIGINT",
        N_(L"Quit request from job control (^C)")
    }
    ,
#endif
#ifdef SIGQUIT
    {
        SIGQUIT,
        L"SIGQUIT",
        N_(L"Quit request from job control with core dump (^\\)")
    }
    ,
#endif
#ifdef SIGILL
    {
        SIGILL,
        L"SIGILL",
        N_(L"Illegal instruction")
    }
    ,
#endif
#ifdef SIGTRAP
    {
        SIGTRAP,
        L"SIGTRAP",
        N_(L"Trace or breakpoint trap")
    }
    ,
#endif
#ifdef SIGABRT
    {
        SIGABRT,
        L"SIGABRT",
        N_(L"Abort")
    }
    ,
#endif
#ifdef SIGBUS
    {
        SIGBUS,
        L"SIGBUS",
        N_(L"Misaligned address error")
    }
    ,
#endif
#ifdef SIGFPE
    {
        SIGFPE,
        L"SIGFPE",
        N_(L"Floating point exception")
    }
    ,
#endif
#ifdef SIGKILL
    {
        SIGKILL,
        L"SIGKILL",
        N_(L"Forced quit")
    }
    ,
#endif
#ifdef SIGUSR1
    {
        SIGUSR1,
        L"SIGUSR1",
        N_(L"User defined signal 1")
    }
    ,
#endif
#ifdef SIGUSR2
    {
        SIGUSR2, L"SIGUSR2",
        N_(L"User defined signal 2")
    }
    ,
#endif
#ifdef SIGSEGV
    {
        SIGSEGV,
        L"SIGSEGV",
        N_(L"Address boundary error")
    }
    ,
#endif
#ifdef SIGPIPE
    {
        SIGPIPE,
        L"SIGPIPE",
        N_(L"Broken pipe")
    }
    ,
#endif
#ifdef SIGALRM
    {
        SIGALRM,
        L"SIGALRM",
        N_(L"Timer expired")
    }
    ,
#endif
#ifdef SIGTERM
    {
        SIGTERM,
        L"SIGTERM",
        N_(L"Polite quit request")
    }
    ,
#endif
#ifdef SIGCHLD
    {
        SIGCHLD,
        L"SIGCHLD",
        N_(L"Child process status changed")
    }
    ,
#endif
#ifdef SIGCONT
    {
        SIGCONT,
        L"SIGCONT",
        N_(L"Continue previously stopped process")
    }
    ,
#endif
#ifdef SIGSTOP
    {
        SIGSTOP,
        L"SIGSTOP",
        N_(L"Forced stop")
    }
    ,
#endif
#ifdef SIGTSTP
    {
        SIGTSTP,
        L"SIGTSTP",
        N_(L"Stop request from job control (^Z)")
    }
    ,
#endif
#ifdef SIGTTIN
    {
        SIGTTIN,
        L"SIGTTIN",
        N_(L"Stop from terminal input")
    }
    ,
#endif
#ifdef SIGTTOU
    {
        SIGTTOU,
        L"SIGTTOU",
        N_(L"Stop from terminal output")
    }
    ,
#endif
#ifdef SIGURG
    {
        SIGURG,
        L"SIGURG",
        N_(L"Urgent socket condition")
    }
    ,
#endif
#ifdef SIGXCPU
    {
        SIGXCPU,
        L"SIGXCPU",
        N_(L"CPU time limit exceeded")
    }
    ,
#endif
#ifdef SIGXFSZ
    {
        SIGXFSZ,
        L"SIGXFSZ",
        N_(L"File size limit exceeded")
    }
    ,
#endif
#ifdef SIGVTALRM
    {
        SIGVTALRM,
        L"SIGVTALRM",
        N_(L"Virtual timer expired")
    }
    ,
#endif
#ifdef SIGPROF
    {
        SIGPROF,
        L"SIGPROF",
        N_(L"Profiling timer expired")
    }
    ,
#endif
#ifdef SIGWINCH
    {
        SIGWINCH,
        L"SIGWINCH",
        N_(L"Window size change")
    }
    ,
#endif
#ifdef SIGWIND
    {
        SIGWIND,
        L"SIGWIND",
        N_(L"Window size change")
    }
    ,
#endif
#ifdef SIGIO
    {
        SIGIO,
        L"SIGIO",
        N_(L"I/O on asynchronous file descriptor is possible")
    }
    ,
#endif
#ifdef SIGPWR
    {
        SIGPWR,
        L"SIGPWR",
        N_(L"Power failure")
    }
    ,
#endif
#ifdef SIGSYS
    {
        SIGSYS,
        L"SIGSYS",
        N_(L"Bad system call")
    }
    ,
#endif
#ifdef SIGINFO
    {
        SIGINFO,
        L"SIGINFO",
        N_(L"Information request")
    }
    ,
#endif
#ifdef SIGSTKFLT
    {
        SIGSTKFLT,
        L"SISTKFLT",
        N_(L"Stack fault")
    }
    ,
#endif
#ifdef SIGEMT
    {
        SIGEMT,
        L"SIGEMT",
        N_(L"Emulator trap")
    }
    ,
#endif
#ifdef SIGIOT
    {
        SIGIOT,
        L"SIGIOT",
        N_(L"Abort (Alias for SIGABRT)")
    }
    ,
#endif
#ifdef SIGUNUSED
    {
        SIGUNUSED,
        L"SIGUNUSED",
        N_(L"Unused signal")
    }
    ,
#endif
    {
        0,
        0,
        0
    }
}
;


/**
   Test if \c name is a string describing the signal named \c canonical.
*/
static int match_signal_name(const wchar_t *canonical,
                             const wchar_t *name)
{
    if (wcsncasecmp(name, L"sig", 3)==0)
        name +=3;

    return wcscasecmp(canonical+3,name) == 0;
}


int wcs2sig(const wchar_t *str)
{
    int i;
    wchar_t *end=0;

    for (i=0; lookup[i].desc ; i++)
    {
        if (match_signal_name(lookup[i].name, str))
        {
            return lookup[i].signal;
        }
    }
    errno=0;
    int res = fish_wcstoi(str, &end, 10);
    if (!errno && res>=0 && !*end)
        return res;

    return -1;
}


const wchar_t *sig2wcs(int sig)
{
    int i;

    for (i=0; lookup[i].desc ; i++)
    {
        if (lookup[i].signal == sig)
        {
            return lookup[i].name;
        }
    }

    return _(L"Unknown");
}

const wchar_t *signal_get_desc(int sig)
{
    int i;

    for (i=0; lookup[i].desc ; i++)
    {
        if (lookup[i].signal == sig)
        {
            return _(lookup[i].desc);
        }
    }

    return _(L"Unknown");
}

/**
   Standard signal handler
*/
static void default_handler(int signal, siginfo_t *info, void *context)
{
    if (event_is_signal_observed(signal))
    {
        event_fire_signal(signal);
    }
}

/**
   Respond to a winch signal by checking the terminal size
*/
static void handle_winch(int sig, siginfo_t *info, void *context)
{
    common_handle_winch(sig);
    default_handler(sig, 0, 0);
}

/**
   Respond to a hup signal by exiting, unless it is caught by a
   shellscript function, in which case we do nothing.
*/
static void handle_hup(int sig, siginfo_t *info, void *context)
{
    if (event_is_signal_observed(SIGHUP))
    {
        default_handler(sig, 0, 0);
    }
    else
    {
        reader_exit(1, 1);
    }
}

/** Handle sigterm. The only thing we do is restore the front process ID, then die. */
static void handle_term(int sig, siginfo_t *info, void *context)
{
    restore_term_foreground_process_group();
    signal(SIGTERM, SIG_DFL);
    raise(SIGTERM);
}

/**
   Interactive mode ^C handler. Respond to int signal by setting
   interrupted-flag and stopping all loops and conditionals.
*/
static void handle_int(int sig, siginfo_t *info, void *context)
{
    reader_handle_int(sig);
    default_handler(sig, info, context);
}

/**
   sigchld handler. Does notification and calls the handler in proc.c
*/
static void handle_chld(int sig, siginfo_t *info, void *context)
{
    job_handle_signal(sig, info, context);
    default_handler(sig, info, context);
}

void signal_reset_handlers()
{
    int i;

    struct sigaction act;
    sigemptyset(& act.sa_mask);
    act.sa_flags=0;
    act.sa_handler=SIG_DFL;

    for (i=0; lookup[i].desc ; i++)
    {
        sigaction(lookup[i].signal, &act, 0);
    }
}


/**
   Sets appropriate signal handlers.
*/
void signal_set_handlers()
{
    struct sigaction act;

    if (get_is_interactive() == -1)
        return;

    sigemptyset(& act.sa_mask);
    act.sa_flags=SA_SIGINFO;
    act.sa_sigaction = &default_handler;

    /*
      First reset everything to a use default_handler, a function
      whose sole action is to fire of an event
    */
    sigaction(SIGINT, &act, 0);
    sigaction(SIGQUIT, &act, 0);
    sigaction(SIGTSTP, &act, 0);
    sigaction(SIGTTIN, &act, 0);
    sigaction(SIGTTOU, &act, 0);
    sigaction(SIGCHLD, &act, 0);

    /*
      Ignore sigpipe, it is generated if fishd dies, but we can
      recover.
    */
    sigaction(SIGPIPE, &act, 0);

    if (get_is_interactive())
    {
        /*
           Interactive mode. Ignore interactive signals.  We are a
           shell, we know whats best for the user. ;-)
        */

        act.sa_handler=SIG_IGN;

        sigaction(SIGINT, &act, 0);
        sigaction(SIGQUIT, &act, 0);
        sigaction(SIGTSTP, &act, 0);
        sigaction(SIGTTIN, &act, 0);
        sigaction(SIGTTOU, &act, 0);

        act.sa_sigaction = &handle_int;
        act.sa_flags = SA_SIGINFO;
        if (sigaction(SIGINT, &act, 0))
        {
            wperror(L"sigaction");
            FATAL_EXIT();
        }

        act.sa_sigaction = &handle_chld;
        act.sa_flags = SA_SIGINFO;
        if (sigaction(SIGCHLD, &act, 0))
        {
            wperror(L"sigaction");
            FATAL_EXIT();
        }

#ifdef SIGWINCH
        act.sa_flags = SA_SIGINFO;
        act.sa_sigaction= &handle_winch;
        if (sigaction(SIGWINCH, &act, 0))
        {
            wperror(L"sigaction");
            FATAL_EXIT();
        }
#endif

        act.sa_flags = SA_SIGINFO;
        act.sa_sigaction= &handle_hup;
        if (sigaction(SIGHUP, &act, 0))
        {
            wperror(L"sigaction");
            FATAL_EXIT();
        }

        // SIGTERM restores the terminal controlling process before dying
        act.sa_flags = SA_SIGINFO;
        act.sa_sigaction= &handle_term;
        if (sigaction(SIGTERM, &act, 0))
        {
            wperror(L"sigaction");
            FATAL_EXIT();
        }

    }
    else
    {
        /*
          Non-interactive. Ignore interrupt, check exit status of
          processes to determine result instead.
        */
        act.sa_handler=SIG_IGN;

        sigaction(SIGINT, &act, 0);
        sigaction(SIGQUIT, &act, 0);

        act.sa_handler=SIG_DFL;

        act.sa_sigaction = &handle_chld;
        act.sa_flags = SA_SIGINFO;
        if (sigaction(SIGCHLD, &act, 0))
        {
            wperror(L"sigaction");
            exit_without_destructors(1);
        }
    }

}

void signal_handle(int sig, int do_handle)
{
    struct sigaction act;

    /*
      These should always be handled
    */
    if ((sig == SIGINT) ||
            (sig == SIGQUIT) ||
            (sig == SIGTSTP) ||
            (sig == SIGTTIN) ||
            (sig == SIGTTOU) ||
            (sig == SIGCHLD))
        return;

    sigemptyset(&act.sa_mask);
    if (do_handle)
    {
        act.sa_flags = SA_SIGINFO;
        act.sa_sigaction = &default_handler;
    }
    else
    {
        act.sa_flags = 0;
        act.sa_handler = SIG_DFL;
    }

    sigaction(sig, &act, 0);
}

void get_signals_with_handlers(sigset_t *set)
{
    sigemptyset(set);
    for (int i=0; lookup[i].desc ; i++)
    {
        struct sigaction act = {};
        sigaction(lookup[i].signal, NULL, &act);
        if (act.sa_handler != SIG_DFL)
            sigaddset(set, lookup[i].signal);
    }
}

void signal_block()
{
    ASSERT_IS_MAIN_THREAD();
    sigset_t chldset;

    if (!block_count)
    {
        sigfillset(&chldset);
        VOMIT_ON_FAILURE(pthread_sigmask(SIG_BLOCK, &chldset, NULL));
    }

    block_count++;
//	debug( 0, L"signal block level increased to %d", block_count );
}

void signal_unblock()
{
    ASSERT_IS_MAIN_THREAD();
    sigset_t chldset;

    block_count--;

    if (block_count < 0)
    {
        debug(0, _(L"Signal block mismatch"));
        bugreport();
        FATAL_EXIT();
    }

    if (!block_count)
    {
        sigfillset(&chldset);
        VOMIT_ON_FAILURE(pthread_sigmask(SIG_UNBLOCK, &chldset, 0));
    }
//	debug( 0, L"signal block level decreased to %d", block_count );
}

bool signal_is_blocked()
{
    return !!block_count;
}