contrib/xz/src/xz/signals.c

   1 ///////////////////////////////////////////////////////////////////////////////
   2 //
   3 /// \file       signals.c
   4 /// \brief      Handling signals to abort operation
   5 //
   6 //  Author:     Lasse Collin
   7 //
   8 //  This file has been put into the public domain.
   9 //  You can do whatever you want with this file.
  10 //
  11 ///////////////////////////////////////////////////////////////////////////////
  12
  13 #include "private.h"
  14
  15
  16 volatile sig_atomic_t user_abort = false;
  17
  18
  19 #if !(defined(_WIN32) && !defined(__CYGWIN__))
  20
  21 /// If we were interrupted by a signal, we store the signal number so that
  22 /// we can raise that signal to kill the program when all cleanups have
  23 /// been done.
  24 static volatile sig_atomic_t exit_signal = 0;
  25
  26 /// Mask of signals for which have have established a signal handler to set
  27 /// user_abort to true.
  28 static sigset_t hooked_signals;
  29
  30 /// True once signals_init() has finished. This is used to skip blocking
  31 /// signals (with uninitialized hooked_signals) if signals_block() and
  32 /// signals_unblock() are called before signals_init() has been called.
  33 static bool signals_are_initialized = false;
  34
  35 /// signals_block() and signals_unblock() can be called recursively.
  36 static size_t signals_block_count = 0;
  37
  38
  39 static void
  40 signal_handler(int sig)
  41 {
  42         exit_signal = sig;
  43         user_abort = true;
  44         return;
  45 }
  46
  47
  48 extern void
  49 signals_init(void)
  50 {
  51         // List of signals for which we establish the signal handler.
  52         static const int sigs[] = {
  53                 SIGINT,
  54                 SIGTERM,
  55 #ifdef SIGHUP
  56                 SIGHUP,
  57 #endif
  58 #ifdef SIGPIPE
  59                 SIGPIPE,
  60 #endif
  61 #ifdef SIGXCPU
  62                 SIGXCPU,
  63 #endif
  64 #ifdef SIGXFSZ
  65                 SIGXFSZ,
  66 #endif
  67         };
  68
  69         // Mask of the signals for which we have established a signal handler.
  70         sigemptyset(&hooked_signals);
  71         for (size_t i = 0; i < ARRAY_SIZE(sigs); ++i)
  72                 sigaddset(&hooked_signals, sigs[i]);
  73
  74 #ifdef SIGALRM
  75         // Add also the signals from message.c to hooked_signals.
  76         for (size_t i = 0; message_progress_sigs[i] != 0; ++i)
  77                 sigaddset(&hooked_signals, message_progress_sigs[i]);
  78 #endif
  79
  80         struct sigaction sa;
  81
  82         // All the signals that we handle we also blocked while the signal
  83         // handler runs.
  84         sa.sa_mask = hooked_signals;
  85
  86         // Don't set SA_RESTART, because we want EINTR so that we can check
  87         // for user_abort and cleanup before exiting. We block the signals
  88         // for which we have established a handler when we don't want EINTR.
  89         sa.sa_flags = 0;
  90         sa.sa_handler = &signal_handler;
  91
  92         for (size_t i = 0; i < ARRAY_SIZE(sigs); ++i) {
  93                 // If the parent process has left some signals ignored,
  94                 // we don't unignore them.
  95                 struct sigaction old;
  96                 if (sigaction(sigs[i], NULL, &old) == 0
  97                                 && old.sa_handler == SIG_IGN)
  98                         continue;
  99
 100                 // Establish the signal handler.
 101                 if (sigaction(sigs[i], &sa, NULL))
 102                         message_signal_handler();
 103         }
 104
 105         signals_are_initialized = true;
 106
 107         return;
 108 }
 109
 110
 111 #ifndef __VMS
 112 extern void
 113 signals_block(void)
 114 {
 115         if (signals_are_initialized) {
 116                 if (signals_block_count++ == 0) {
 117                         const int saved_errno = errno;
 118                         mythread_sigmask(SIG_BLOCK, &hooked_signals, NULL);
 119                         errno = saved_errno;
 120                 }
 121         }
 122
 123         return;
 124 }
 125
 126
 127 extern void
 128 signals_unblock(void)
 129 {
 130         if (signals_are_initialized) {
 131                 assert(signals_block_count > 0);
 132
 133                 if (--signals_block_count == 0) {
 134                         const int saved_errno = errno;
 135                         mythread_sigmask(SIG_UNBLOCK, &hooked_signals, NULL);
 136                         errno = saved_errno;
 137                 }
 138         }
 139
 140         return;
 141 }
 142 #endif
 143
 144
 145 extern void
 146 signals_exit(void)
 147 {
 148         const int sig = exit_signal;
 149
 150         if (sig != 0) {
 151 #if defined(TUKLIB_DOSLIKE) || defined(__VMS)
 152                 // Don't raise(), set only exit status. This avoids
 153                 // printing unwanted message about SIGINT when the user
 154                 // presses C-c.
 155                 set_exit_status(E_ERROR);
 156 #else
 157                 struct sigaction sa;
 158                 sa.sa_handler = SIG_DFL;
 159                 sigfillset(&sa.sa_mask);
 160                 sa.sa_flags = 0;
 161                 sigaction(sig, &sa, NULL);
 162                 raise(exit_signal);
 163 #endif
 164         }
 165
 166         return;
 167 }
 168
 169 #else
 170
 171 // While Windows has some very basic signal handling functions as required
 172 // by C89, they are not really used, and e.g. SIGINT doesn't work exactly
 173 // the way it does on POSIX (Windows creates a new thread for the signal
 174 // handler). Instead, we use SetConsoleCtrlHandler() to catch user
 175 // pressing C-c, because that seems to be the recommended way to do it.
 176 //
 177 // NOTE: This doesn't work under MSYS. Trying with SIGINT doesn't work
 178 // either even if it appeared to work at first. So test using Windows
 179 // console window.
 180
 181 static BOOL WINAPI
 182 signal_handler(DWORD type lzma_attribute((__unused__)))
 183 {
 184         // Since we don't get a signal number which we could raise() at
 185         // signals_exit() like on POSIX, just set the exit status to
 186         // indicate an error, so that we cannot return with zero exit status.
 187         set_exit_status(E_ERROR);
 188         user_abort = true;
 189         return TRUE;
 190 }
 191
 192
 193 extern void
 194 signals_init(void)
 195 {
 196         if (!SetConsoleCtrlHandler(&signal_handler, TRUE))
 197                 message_signal_handler();
 198
 199         return;
 200 }
 201
 202 #endif