/*---------------------------------------------------------------------------- -- -- -- FLORIST (FSU Implementation of POSIX.5) COMPONENTS -- -- -- -- -- -- C - P O S I X - S I G N A L S . C -- -- -- -- -- -- Copyright (c) 1998 Florida State University (FSU), All Rights -- -- Reserved. -- -- -- -- This file is a component of FLORIST, an implementation of an Ada API -- -- for the POSIX OS services, for use with the GNAT Ada compiler and -- -- the FSU Gnu Ada Runtime Library (GNARL). The interface is intended -- -- to be close to that specified in IEEE STD 1003.5: 1990 and IEEE STD -- -- 1003.5b: 1996. -- -- -- -- FLORIST is free software; you can redistribute it and/or modify it -- -- under terms of the GNU General Public License as published by the -- -- Free Software Foundation; either version 2, or (at your option) any -- -- later version. FLORIST is distributed in the hope that it will be -- -- useful, but WITHOUT ANY WARRANTY; without even the implied warranty -- -- of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU -- -- General Public License for more details. You should have received a -- -- copy of the GNU General Public License distributed with GNARL; see -- -- file COPYING. If not, write to the Free Software Foundation, 59 -- -- Temple Place - Suite 330, Boston, MA 02111-1307, USA -- -- -- -- As a special exception, if other files instantiate generics from this -- -- unit, or you link this unit with other files to produce an executable, -- -- this unit does not by itself cause the resulting executable to be -- -- covered by the GNU General Public License. This exception does not -- -- however invalidate any other reasons why the executable file might be -- -- covered by the GNU Public License. -- -- -- ----------------------------------------------------------------------------*/ /* file: c-posix-signals.c ======================= [$Revision: 1.6 $] This program generates the file posix-implementation-ok_signals.ads, which is an Ada package specification that defines a list of signals that seem to work correctly with sigwait(). The test is to mask a given signal, then use kill () to send the signal to the current process, then call sigwait () to receive the signal. The observed behavior for some signals is that the process hangs on sigwait, notably for signals whose default action is to ignore the signal or stop the process. In order to allow testing of more than one signal, the program tries to recover if sigwait() hangs. The first attempt was to use alarm() to arrange for another signal to be delivered, if sigwait() did not receive the tested signal within one second. This seemed to have worked for SIGCHLD and SIGCONT, i.e. the signals whose default action is to ignore them. It did not seem to work for SIGSTOP, SITTSTP, SIGTTIN, SIGTTOU, whose default action is to stop the process. In order to recover for these cases, we moved the test of sigwait() into a child process, and arranged for the parent process to send SIGCONT to the child if it stops. This seems to solve the problem. When linking this test don't forget to use "-lpthread", or the appropriate thread library. */ #define _POSIX_C_SOURCE 199506L #define _REENTRANT #define _POSIX_C_SIGNALS_C #include "pconfig.h" #include #include #include #include #include #include #include #include #include /* Uncomment the following only for debugging. */ /* #define DEBUG */ int sigs [] = { 0, #ifdef SIG32 SIG32, #endif #ifdef SIGABRT SIGABRT, #endif #ifdef SIGALRM SIGALRM, #endif #ifdef SIGBUS SIGBUS, #endif #ifdef SIGCANCEL SIGCANCEL, #endif #ifdef SIGCHLD SIGCHLD, #endif #ifdef SIGCLD SIGCLD, #endif #ifdef SIGCONT SIGCONT, #endif #ifdef SIGEMT SIGEMT, #endif #ifdef SIGFPE SIGFPE, #endif #ifdef SIGFREEZE SIGFREEZE, #endif #ifdef SIGHUP SIGHUP, #endif #ifdef SIGILL SIGILL, #endif #ifdef SIGINT SIGINT, #endif #ifdef SIGIO SIGIO, #endif #ifdef SIGIOT SIGIOT, #endif #ifdef SIGKILL SIGKILL, #endif #ifdef SIGLOST SIGLOST, #endif #ifdef SIGLWP SIGLWP, #endif #ifdef SIGPIPE SIGPIPE, #endif #ifdef SIGPOLL SIGPOLL, #endif #ifdef SIGPROF SIGPROF, #endif #ifdef SIGQUIT SIGQUIT, #endif #ifdef SIGSEGV SIGSEGV, #endif #ifdef SIGSTKFLT SIGSTKFLT, #endif #ifdef SIGSYS SIGSYS, #endif #ifdef SIGTERM SIGTERM, #endif #ifdef SIGUSR1 SIGUSR1, #endif #ifdef SIGUSR2 SIGUSR2, #endif #ifdef SIGTRAP SIGTRAP, #endif #ifdef SIGSTOP SIGSTOP, #endif #ifdef SIGTHAW SIGTHAW, #endif #ifdef SIGTSTP SIGTSTP, #endif #ifdef SIGTTIN SIGTTIN, #endif #ifdef SIGTTOU SIGTTOU, #endif #ifdef SIGPWR SIGPWR, #endif #ifdef SIGURG SIGURG, #endif #ifdef SIGUNUSED SIGUNUSED, #endif #ifdef SIGVTALRM SIGVTALRM, #endif #ifdef SIGWAITING SIGWAITING, #endif #ifdef SIGWINCH SIGWINCH, #endif #ifdef SIGXCPU SIGXCPU, #endif #ifdef SIGXFSZ SIGXFSZ, #endif 0}; char *signames [] = { "SIGNONE", #ifdef SIG32 "SIG32", #endif #ifdef SIGABRT "SIGABRT", #endif #ifdef SIGALRM "SIGALRM", #endif #ifdef SIGBUS "SIGBUS", #endif #ifdef SIGCANCEL "SIGCANCEL", #endif #ifdef SIGCHLD "SIGCHLD", #endif #ifdef SIGCLD "SIGCLD", #endif #ifdef SIGCONT "SIGCONT", #endif #ifdef SIGEMT "SIGEMT", #endif #ifdef SIGFPE "SIGFPE", #endif #ifdef SIGFREEZE "SIGFREEZE", #endif #ifdef SIGHUP "SIGHUP", #endif #ifdef SIGILL "SIGILL", #endif #ifdef SIGINT "SIGINT", #endif #ifdef SIGIO "SIGIO", #endif #ifdef SIGIOT "SIGIOT", #endif #ifdef SIGKILL "SIGKILL", #endif #ifdef SIGLOST "SIGLOST", #endif #ifdef SIGLWP "SIGLWP", #endif #ifdef SIGPIPE "SIGPIPE", #endif #ifdef SIGPOLL "SIGPOLL", #endif #ifdef SIGPROF "SIGPROF", #endif #ifdef SIGQUIT "SIGQUIT", #endif #ifdef SIGSEGV "SIGSEGV", #endif #ifdef SIGSTKFLT "SIGSTKFLT", #endif #ifdef SIGSYS "SIGSYS", #endif #ifdef SIGTERM "SIGTERM", #endif #ifdef SIGUSR1 "SIGUSR1", #endif #ifdef SIGUSR2 "SIGUSR2", #endif #ifdef SIGTRAP "SIGTRAP", #endif #ifdef SIGSTOP "SIGSTOP", #endif #ifdef SIGTHAW "SIGTHAW", #endif #ifdef SIGTSTP "SIGTSTP", #endif #ifdef SIGTTIN "SIGTTIN", #endif #ifdef SIGTTOU "SIGTTOU", #endif #ifdef SIGPWR "SIGPWR", #endif #ifdef SIGURG "SIGURG", #endif #ifdef SIGUNUSED "SIGUNUSED", #endif #ifdef SIGVTALRM "SIGVTALRM", #endif #ifdef SIGWAITING "SIGWAITING", #endif #ifdef SIGWINCH "SIGWINCH", #endif #ifdef SIGXCPU "SIGXCPU", #endif #ifdef SIGXFSZ "SIGXFSZ", #endif "SIGNONE"}; int namedsigs = sizeof (sigs) / sizeof (int); int nsigs; int *oksigs; int *oksigs_nodefault; int *oksigs_stop; void comment (char const *msg) { #ifdef DEBUG fprintf (stderr, "%s\n", msg); fflush (stderr); #endif } void handler (int sig) { if (sig == SIGALRM) { comment ("==> in handler for SIGALRM"); } else { comment ("==> in handler: unexpected signal"); exit (-1); } } void handler_parent (int sig) { if (sig == SIGALRM) { comment ("==> PARENT: in handler for SIGALRM"); } else { comment ("==> PARENT: in handler: unexpected signal"); kill (0, SIGKILL); exit (-1); } } void print_package (int *oksigs, int *oksigs_nodefault, int *oksigs_stop) { int sig; FILE *fp; fprintf (stderr,"creating package POSIX.Implementation.OK_Signals\n"); if (! (fp = fopen ("posix-implementation-ok_signals.ads", "w"))) { perror ("posix-implemenation-ok_signals.ads"); exit (-1); } fprintf (fp, "package POSIX.Implementation.OK_Signals is\n"); fprintf (fp, "\n"); fprintf (fp, " -- OK (Sig) = True iff we can use Sig" " with sigwait ().\n\n"); fprintf (fp, " OK : constant array (0 .. %d) of Boolean :=\n", nsigs - 1); fprintf (fp, " ("); for (sig = 0; sig < nsigs; sig++) { if (oksigs_nodefault[sig] == 1) fprintf (fp, " True"); else fprintf (fp, "False"); if (sig == nsigs - 1) fprintf (fp, ");\n"); else if (sig % 10 == 9) fprintf (fp, ",\n "); else fprintf (fp, ", "); } fprintf (fp, "\n"); fprintf (fp, " -- Default_Is_Ignore (Sig) = True iff we need to" " override the default\n"); fprintf (fp, " -- treatment of Sig with a do-nothing handler" " before we try to\n"); fprintf (fp, " -- use sigwait() with it.\n\n"); fprintf (fp, " Default_Is_Ignore : constant array" " (0 .. %d) of Boolean :=\n", nsigs - 1); fprintf (fp, " ("); for (sig = 0; sig < nsigs; sig++) { if ((oksigs[sig] != 1) && (oksigs_nodefault[sig] == 1)) fprintf (fp, " True"); else fprintf (fp, "False"); if (sig == nsigs - 1) fprintf (fp, ");\n"); else if (sig % 10 == 9) fprintf (fp, ",\n "); else fprintf (fp, ", "); } fprintf (fp, "\n -- Default_Is_Stop (Sig) = True iff the default" " action of Sig\n -- is to stop the process.\n\n"); fprintf (fp, " Default_Is_Stop : constant array (0 .. %d)" " of Boolean :=\n", nsigs - 1); fprintf (fp, " ("); for (sig = 0; sig < nsigs; sig++) { if (oksigs_stop[sig] == 1) fprintf (fp, " True"); else fprintf (fp, "False"); if (sig == nsigs - 1) fprintf (fp, ");\n"); else if (sig % 10 == 9) fprintf (fp, ",\n "); else fprintf (fp, ", "); } fprintf (fp, "\nend POSIX.Implementation.OK_Signals;\n"); fclose (fp); } int guess_nsigs () { /* Try to find out the range of valid signals. We have not yet discovered a portable C way of doing this. We assume the range starts at 0 and is continuous up to some limit. We need this becuase we want to represent sets of signals as Boolean arrays. We considered using sigset_t directly, and would have liked to do so, but had two problems: (1) sigset_t apparently allows the use of dynamically allocated memory (2) we could not figure out how to check for signal validity; in particular, we needed a way to check for whether a given signal is reserved by the Ada runtime system. */ sigset_t set; int sig; int result; int last_good = -1; int first_bad = -1; sigfillset (&set); for (sig = 0; sig < 1024; sig++) { result = sigismember (&set, sig); if (result == 1) { last_good = sig; } else if ((result == -1) && (first_bad == -1)) { if (sig == 0) { fprintf (stderr, "WARNING: C library problem? " "sigfillset does not include zero\n"); } else first_bad = sig; } } if (last_good == 1023) fprintf (stderr, "WARNING: signal range estimate probably too small\n"); if (first_bad < last_good) { fprintf (stderr, "WARNING: signal range estimate may be invalid\n"); last_good = first_bad - 1; } return last_good + 1; } void parent_process(pid_t child, int *oksigs, int sig) { /* Monitor the child process until it terminates. If the child process stops, wake it up. If the child process dies via signal, restart it and tell it to skip the last signal it was trying. */ pid_t ret; int status; struct sigaction act; act.sa_flags = 0; act.sa_handler = handler_parent; if (sigaction (SIGALRM, &act, NULL)) perror ("sigaction (handler_parent)"); while (1) { alarm (30); comment (" PARENT: awaiting child status"); fflush (stderr); ret = waitpid ( (pid_t) -1, &status, WUNTRACED); fflush (stderr); if (ret == -1) { if (errno == EINTR) { comment (" PARENT: timed out, sending SIGCONT"); fflush (stderr); kill (child, SIGCONT); alarm (0); sleep (1); continue; } comment (" PARENT: waitpid failed"); kill (0, SIGKILL); exit (-1); } if (ret != child) { comment (" PARENT: unknown child"); kill (0, SIGKILL); exit (-1); } if (WIFSTOPPED (status)) { oksigs_stop [sig] = 1; comment (" PARENT: sending SIGCONT to stopped child"); kill (child, SIGCONT); alarm (0); sleep (1); continue; } if (WIFEXITED (status)) { if (WEXITSTATUS (status) != 1) comment (" PARENT: child exited abnormally"); else { oksigs [sig] = 1; comment (" PARENT: child exited normally"); } return; } if (WIFSIGNALED (status)) { comment(" PARENT: child killed by signal"); fprintf (stderr, "child process killed by signal %d\n", WTERMSIG (status)); return; } comment (" PARENT: invalid child status %x"); kill (0, SIGKILL); exit (-1); } } void test_signal (int nodefaults, int signal) { struct sigaction act; int sig; sigset_t set, oset; int ret; act.sa_flags = 0; act.sa_handler = handler; #ifdef LYNX_SIGTHREADKILL_HACK /* Attempting to test SIGTHREADKILL on LynxOS will kill both the child and the parent process: The call to sigaction fails and falls through to kill (0, SIGKILL). This code works around a problem specific to LynxOS, where signal 24 is reserved by the user space portion of the pthreads implementation. It should be replaced by a general mechanism for skipping problematic signals. */ if (signal == SIGTHREADKILL) { fprintf (stderr, "Reserved by C library.\n"); fflush (stderr); exit (-1); } #endif /* LYNX_SIGTHREADKILL_HACK */ if (sigaction (signal, &act, NULL)) { if (errno == EINVAL) { fprintf (stderr, "cannot be caught\n"); fflush (stderr); exit (-1); } else { fprintf (stderr, " *** sigaction: %s\n", strerror (errno)); fflush (stderr); kill (0, SIGKILL); exit (-1); } } if (! nodefaults) { act.sa_handler = SIG_IGN; if (sigaction (signal, &act, NULL)) { if (errno == EINVAL) { fprintf (stderr, "cannot be ignored\n"); fflush (stderr); exit (-1); } else { fprintf (stderr, " *** sigaction: %s\n", strerror (errno)); fflush (stderr); kill (0, SIGKILL); exit (-1); } } } if (! nodefaults) { act.sa_handler = SIG_DFL; if (sigaction (signal, &act, NULL)) { fprintf (stderr, " *** sigaction: %s\n", strerror (errno)); fflush (stderr); kill (0, SIGKILL); exit (-1); } } if (sigemptyset (&set)) perror ("sigemptyset"); if (sigaddset (&set, signal)) perror ("sigaddset"); if (sigaddset (&set, SIGALRM)) perror ("sigaddset"); comment (" masking signal"); if ((ret = pthread_sigmask (SIG_BLOCK, &set, NULL))) fprintf (stderr, " *** pthread_sigmask (SIG_BLOCK): %s\n", strerror (ret)); if ((ret = pthread_sigmask (SIG_BLOCK, &set, &oset))) fprintf (stderr, " *** pthread_sigmask (SIG_BLOCK 2): %s\n", strerror (ret)); if (sigismember (&oset, signal) == 0) { /* we are unable to mask this signal */ fprintf (stderr, "cannot be masked.\n"); exit (-1); } comment (" sending signal to self"); if (kill (getpid (), signal)) perror ("kill"); comment (" setting one second timeout"); alarm (1); comment (" doing sigwait"); #ifndef _CMA_OS_ if (ret = sigwait (&set, &sig)) { #else ret = sigwait (&set); if (ret == -1) ret = errno; else { sig = ret; ret = 0; } if (ret) { #endif fprintf (stderr, "*** sigwait: %s\n", strerror (ret)); } else if (sig == signal) { fprintf (stderr, "works OK.\n"); exit (1); /* signal is OK */ } else if (sig == SIGALRM) { fprintf (stderr, "*** timed out\n"); } else { fprintf (stderr, "*** wrong signal: %d\n", sig); } exit (-1); } void test_signals (int nodefaults, int *oksigs) { /* Test each signal, to see if it works with sigwait(). If nodefault != 0 then override the default treatment by installing a dummy handler. */ int i; int signal; pid_t child; if (nodefaults) fprintf (stderr, "testing signals without default treatments\n"); else fprintf (stderr, "testing signals with default treatments\n"); for (signal = 1; signal < nsigs; signal++) { for (i = 0; i < namedsigs; i++) if (sigs[i] == signal) break; if (i < namedsigs) fprintf (stderr, "testing signal: %2d %10s ...", signal, signames[i]); else fprintf (stderr, "testing signal: %2d ...", signal); fflush (stderr); if ((child = fork ())) parent_process (child, oksigs, signal); else { test_signal (nodefaults, signal); fprintf (stderr, "*** should never return ***"); exit (-1); } } } int main (int argc, char *argv[]){ int i; struct sigaction act; nsigs = guess_nsigs(); fprintf (stderr, "nsigs: %d\n", nsigs); oksigs = (int *) malloc (nsigs * sizeof (int)); oksigs_nodefault = (int *) malloc (nsigs * sizeof (int)); oksigs_stop = (int *) malloc (nsigs * sizeof (int)); for (i = 0; i < nsigs; i++) oksigs[i] = oksigs_nodefault[i] = oksigs_stop[i]= 0; act.sa_flags = 0; act.sa_handler = handler; if (sigaction (SIGALRM, &act, NULL)) perror ("sigaction (handler)"); #ifdef DEBUG comment ("sending 3 SIGALRM's, to test handler"); fflush (stderr); kill (getpid (), SIGALRM); kill (getpid (), SIGALRM); kill (getpid (), SIGALRM); #endif test_signals (0, oksigs); test_signals (1, oksigs_nodefault); print_package (oksigs, oksigs_nodefault, oksigs_stop); fprintf (stderr, "done.\n"); return 0; }