maint/gnulib/lib/c-stack.c

/* */
This source file includes following definitions.
die
null_action
segv_handler
overflow_handler
c_stack_action
c_stack_action
   1 /* Stack overflow handling.
   2 
   3    Copyright (C) 2002, 2004, 2006, 2008-2021 Free Software Foundation, Inc.
   4 
   5    This program is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 3 of the License, or
   8    (at your option) any later version.
   9 
  10    This program 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
  13    GNU General Public License for more details.
  14 
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17 
  18 /* Written by Paul Eggert.  */
  19 
  20 /* NOTES:
  21 
  22    A program that uses alloca, dynamic arrays, or large local
  23    variables may extend the stack by more than a page at a time.  If
  24    so, when the stack overflows the operating system may not detect
  25    the overflow until the program uses the array, and this module may
  26    incorrectly report a program error instead of a stack overflow.
  27 
  28    To avoid this problem, allocate only small objects on the stack; a
  29    program should be OK if it limits single allocations to a page or
  30    less.  Allocate larger arrays in static storage, or on the heap
  31    (e.g., with malloc).  Yes, this is a pain, but we don't know of any
  32    better solution that is portable.
  33 
  34    No attempt has been made to deal with multithreaded applications.  */
  35 
  36 #include <config.h>
  37 
  38 #include "c-stack.h"
  39 
  40 #include <errno.h>
  41 #include <inttypes.h>
  42 #include <signal.h>
  43 #include <stddef.h>
  44 #include <stdlib.h>
  45 #include <string.h>
  46 #include <unistd.h>
  47 
  48 #if DEBUG
  49 # include <stdio.h>
  50 #endif
  51 
  52 #include <sigsegv.h>
  53 
  54 #include "exitfail.h"
  55 #include "getprogname.h"
  56 #include "idx.h"
  57 #include "ignore-value.h"
  58 
  59 #include "gettext.h"
  60 #define _(msgid) gettext (msgid)
  61 
  62 #if HAVE_STACK_OVERFLOW_RECOVERY
  63 
  64 /* Storage for the alternate signal stack.
  65    64 KiB is not too large for Gnulib-using apps, and is large enough
  66    for all known platforms.  Smaller sizes may run into trouble.
  67    For example, libsigsegv 2.6 through 2.8 have a bug where some
  68    architectures use more than the Linux default of an 8 KiB alternate
  69    stack when deciding if a fault was caused by stack overflow.  */
  70 static max_align_t alternate_signal_stack[(64 * 1024
  71                                            + sizeof (max_align_t) - 1)
  72                                           / sizeof (max_align_t)];
  73 
  74 /* The user-specified action to take when a SEGV-related program error
  75    or stack overflow occurs.  */
  76 static _GL_ASYNC_SAFE void (* volatile segv_action) (int);
  77 
  78 /* Translated messages for program errors and stack overflow.  Do not
  79    translate them in the signal handler, since gettext is not
  80    async-signal-safe.  */
  81 static char const * volatile program_error_message;
  82 static char const * volatile stack_overflow_message;
  83 
  84 /* Output an error message, then exit with status EXIT_FAILURE if it
  85    appears to have been a stack overflow, or with a core dump
  86    otherwise.  This function is async-signal-safe.  */
  87 
  88 static char const * volatile progname;
  89 
  90 static _GL_ASYNC_SAFE _Noreturn void
  91 die (int signo)
     /*  */
  92 {
  93   segv_action (signo);
  94   char const *message = signo ? program_error_message : stack_overflow_message;
  95 
  96   /* If the message is short, write it all at once to avoid
  97      interleaving with other messages.  Avoid writev as it is not
  98      documented to be async-signal-safe.  */
  99   size_t prognamelen = strlen (progname);
 100   size_t messagelen = strlen (message);
 101   static char const separator[] = {':', ' '};
 102   char buf[sizeof alternate_signal_stack / 16 + sizeof separator];
 103   idx_t buflen;
 104   if (prognamelen + messagelen < sizeof buf - sizeof separator)
 105     {
 106       char *p = mempcpy (buf, progname, prognamelen);
 107       p = mempcpy (p, separator, sizeof separator);
 108       p = mempcpy (p, message, messagelen);
 109       *p++ = '\n';
 110       buflen = p - buf;
 111     }
 112   else
 113     {
 114       ignore_value (write (STDERR_FILENO, progname, prognamelen));
 115       ignore_value (write (STDERR_FILENO, separator, sizeof separator));
 116       ignore_value (write (STDERR_FILENO, message, messagelen));
 117       buf[0] = '\n';
 118       buflen = 1;
 119     }
 120   ignore_value (write (STDERR_FILENO, buf, buflen));
 121 
 122   if (! signo)
 123     _exit (exit_failure);
 124   raise (signo);
 125   abort ();
 126 }
 127 
 128 static _GL_ASYNC_SAFE void
 129 null_action (_GL_UNUSED int signo)
     /*  */
 130 {
 131 }
 132 
 133 /* Pacify GCC 9.3.1, which otherwise would complain about segv_handler.  */
 134 # if 4 < __GNUC__ + (6 <= __GNUC_MINOR__)
 135 #  pragma GCC diagnostic ignored "-Wsuggest-attribute=pure"
 136 # endif
 137 
 138 /* Nonzero if general segv handler could not be installed.  */
 139 static volatile int segv_handler_missing;
 140 
 141 /* Handle a segmentation violation and exit if it cannot be stack
 142    overflow.  This function is async-signal-safe.  */
 143 
 144 static _GL_ASYNC_SAFE int
 145 segv_handler (_GL_UNUSED void *address, int serious)
     /*  */
 146 {
 147 # if DEBUG
 148   {
 149     char buf[1024];
 150     int saved_errno = errno;
 151     ignore_value (write (STDERR_FILENO, buf,
 152                          sprintf (buf, "segv_handler serious=%d\n", serious)));
 153     errno = saved_errno;
 154   }
 155 # endif
 156 
 157   /* If this fault is not serious, return 0 to let the stack overflow
 158      handler take a shot at it.  */
 159   if (!serious)
 160     return 0;
 161   die (SIGSEGV);
 162 }
 163 
 164 /* Handle a segmentation violation that is likely to be a stack
 165    overflow and exit.  This function is async-signal-safe.  */
 166 
 167 static _GL_ASYNC_SAFE _Noreturn void
 168 overflow_handler (int emergency, _GL_UNUSED stackoverflow_context_t context)
     /*  */
 169 {
 170 # if DEBUG
 171   {
 172     char buf[1024];
 173     ignore_value (write (STDERR_FILENO, buf,
 174                          sprintf (buf, ("overflow_handler emergency=%d"
 175                                         " segv_handler_missing=%d\n"),
 176                                   emergency, segv_handler_missing)));
 177   }
 178 # endif
 179 
 180   die ((!emergency || segv_handler_missing) ? 0 : SIGSEGV);
 181 }
 182 
 183 int
 184 c_stack_action (_GL_ASYNC_SAFE void (*action) (int))
     /*  */
 185 {
 186   segv_action = action ? action : null_action;
 187   program_error_message = _("program error");
 188   stack_overflow_message = _("stack overflow");
 189   progname = getprogname ();
 190 
 191   /* Always install the overflow handler.  */
 192   if (stackoverflow_install_handler (overflow_handler,
 193                                      alternate_signal_stack,
 194                                      sizeof alternate_signal_stack))
 195     {
 196       errno = ENOTSUP;
 197       return -1;
 198     }
 199   /* Try installing a general handler; if it fails, then treat all
 200      segv as stack overflow.  */
 201   segv_handler_missing = sigsegv_install_handler (segv_handler);
 202   return 0;
 203 }
 204 
 205 #else /* !HAVE_STACK_OVERFLOW_RECOVERY */
 206 
 207 int
 208 c_stack_action (_GL_ASYNC_SAFE void (*action) (_GL_UNUSED int) )
     /*  */
 209 {
 210   errno = ENOTSUP;
 211   return -1;
 212 }
 213 
 214 #endif
/* */
root/maint/gnulib/lib/c-stack.c

DEFINITIONS
