signal/tst-minsigstksz-1.c

   1 /* Tests of signal delivery on an alternate stack (nonlethal).
   2    Copyright (C) 2019-2021 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <support/xsignal.h>
  20 #include <support/support.h>
  21 #include <support/check.h>
  22
  23 /* C2011 7.4.1.1p5 specifies that only the following operations are
  24    guaranteed to be well-defined inside an asynchronous signal handler:
  25      * any operation on a lock-free atomic object
  26      * assigning a value to an object declared as volatile sig_atomic_t
  27      * calling abort, _Exit, quick_exit, or signal
  28        * signal may only be called with its first argument equal to the
  29          number of the signal that caused the handler to be called
  30
  31    We use this list as a guideline for the set of operations that ought
  32    also to be safe in a _synchronous_ signal delivered on an alternate
  33    signal stack with only MINSIGSTKSZ bytes of space.
  34
  35    This test program tests all of the above operations that do not,
  36    one way or another, cause the program to be terminated.  */
  37
  38 /* We do not try to test atomic operations exhaustively, only a simple
  39    atomic counter increment.  This is only safe if atomic_[u]int is
  40    unconditionally lock-free.  */
  41 #ifdef __STDC_NO_ATOMICS__
  42 # define TEST_ATOMIC_OPS 0
  43 #else
  44 # include <stdatomic.h>
  45 # if ATOMIC_INT_LOCK_FREE != 2
  46 #  define TEST_ATOMIC_OPS 0
  47 # else
  48 #  define TEST_ATOMIC_OPS 1
  49 # endif
  50 #endif
  51
  52 static volatile sig_atomic_t signal_flag = 0;
  53 static volatile sig_atomic_t signal_err = 0;
  54 static void
  55 handler_set_flag (int unused)
  56 {
  57   signal_flag = 1;
  58 }
  59
  60 static void
  61 handler_set_flag_once (int sig)
  62 {
  63   signal_flag = 1;
  64   if (signal (sig, SIG_IGN) == SIG_ERR)
  65     /* It is not safe to call FAIL_EXIT1 here.  Set another flag instead.  */
  66     signal_err = 1;
  67 }
  68
  69 #if TEST_ATOMIC_OPS
  70 static atomic_uint signal_count = 0;
  71 static void
  72 handler_count_up_1 (int unused)
  73 {
  74   atomic_fetch_add (&signal_count, 1);
  75 }
  76 #endif
  77
  78 int
  79 do_test (void)
  80 {
  81   void *sstk = xalloc_sigstack (0);
  82   struct sigaction sa;
  83
  84   /* Test 1: setting a volatile sig_atomic_t flag.  */
  85   sa.sa_handler = handler_set_flag;
  86   sa.sa_flags   = SA_RESTART | SA_ONSTACK;
  87   sigfillset (&sa.sa_mask);
  88   if (sigaction (SIGUSR1, &sa, 0))
  89     FAIL_EXIT1 ("sigaction (SIGUSR1, handler_set_flag): %m\n");
  90
  91   TEST_VERIFY_EXIT (signal_flag == 0);
  92   raise (SIGUSR1);
  93   TEST_VERIFY_EXIT (signal_flag == 1);
  94   signal_flag = 0;
  95   raise (SIGUSR1);
  96   TEST_VERIFY_EXIT (signal_flag == 1);
  97   signal_flag = 0;
  98
  99   /* Test 1: setting a volatile sig_atomic_t flag and then ignoring
 100      further delivery of the signal. */
 101   sa.sa_handler = handler_set_flag_once;
 102   if (sigaction (SIGUSR1, &sa, 0))
 103     FAIL_EXIT1 ("sigaction (SIGUSR1, handler_set_flag_once): %m\n");
 104
 105   raise (SIGUSR1);
 106   TEST_VERIFY_EXIT (signal_flag == 1);
 107   /* Note: if signal_err is 1, a system call failed, but we can't
 108      report the error code because errno is indeterminate.  */
 109   TEST_VERIFY_EXIT (signal_err == 0);
 110
 111   signal_flag = 0;
 112   raise (SIGUSR1);
 113   TEST_VERIFY_EXIT (signal_flag == 0);
 114   TEST_VERIFY_EXIT (signal_err == 0);
 115
 116 #if TEST_ATOMIC_OPS
 117   sa.sa_handler = handler_count_up_1;
 118   if (sigaction (SIGUSR1, &sa, 0))
 119     FAIL_EXIT1 ("sigaction (SIGUSR1, handler_count_up_1): %m\n");
 120
 121   raise (SIGUSR1);
 122   TEST_VERIFY_EXIT (atomic_load (&signal_count) == 1);
 123   raise (SIGUSR1);
 124   TEST_VERIFY_EXIT (atomic_load (&signal_count) == 2);
 125 #endif
 126
 127   xfree_sigstack (sstk);
 128   return 0;
 129 }
 130
 131 #include <support/test-driver.c>