1 files changed, 214 insertions, 0 deletions
diff --git a/src/grep/lib/c-stack.c b/src/grep/lib/c-stack.c
new file mode 100644
index 0000000..1965bdd
--- /dev/null
+++ b/src/grep/lib/c-stack.c
@@ -0,0 +1,214 @@
+/* Stack overflow handling.
+
+   Copyright (C) 2002, 2004, 2006, 2008-2021 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program 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
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+/* Written by Paul Eggert.  */
+
+/* NOTES:
+
+   A program that uses alloca, dynamic arrays, or large local
+   variables may extend the stack by more than a page at a time.  If
+   so, when the stack overflows the operating system may not detect
+   the overflow until the program uses the array, and this module may
+   incorrectly report a program error instead of a stack overflow.
+
+   To avoid this problem, allocate only small objects on the stack; a
+   program should be OK if it limits single allocations to a page or
+   less.  Allocate larger arrays in static storage, or on the heap
+   (e.g., with malloc).  Yes, this is a pain, but we don't know of any
+   better solution that is portable.
+
+   No attempt has been made to deal with multithreaded applications.  */
+
+#include <config.h>
+
+#include "c-stack.h"
+
+#include <errno.h>
+#include <inttypes.h>
+#include <signal.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#if DEBUG
+# include <stdio.h>
+#endif
+
+#include <sigsegv.h>
+
+#include "exitfail.h"
+#include "getprogname.h"
+#include "idx.h"
+#include "ignore-value.h"
+
+#include "gettext.h"
+#define _(msgid) gettext (msgid)
+
+#if HAVE_STACK_OVERFLOW_RECOVERY
+
+/* Storage for the alternate signal stack.
+   64 KiB is not too large for Gnulib-using apps, and is large enough
+   for all known platforms.  Smaller sizes may run into trouble.
+   For example, libsigsegv 2.6 through 2.8 have a bug where some
+   architectures use more than the Linux default of an 8 KiB alternate
+   stack when deciding if a fault was caused by stack overflow.  */
+static max_align_t alternate_signal_stack[(64 * 1024
+                                           + sizeof (max_align_t) - 1)
+                                          / sizeof (max_align_t)];
+
+/* The user-specified action to take when a SEGV-related program error
+   or stack overflow occurs.  */
+static _GL_ASYNC_SAFE void (* volatile segv_action) (int);
+
+/* Translated messages for program errors and stack overflow.  Do not
+   translate them in the signal handler, since gettext is not
+   async-signal-safe.  */
+static char const * volatile program_error_message;
+static char const * volatile stack_overflow_message;
+
+/* Output an error message, then exit with status EXIT_FAILURE if it
+   appears to have been a stack overflow, or with a core dump
+   otherwise.  This function is async-signal-safe.  */
+
+static char const * volatile progname;
+
+static _GL_ASYNC_SAFE _Noreturn void
+die (int signo)
+{
+  segv_action (signo);
+  char const *message = signo ? program_error_message : stack_overflow_message;
+
+  /* If the message is short, write it all at once to avoid
+     interleaving with other messages.  Avoid writev as it is not
+     documented to be async-signal-safe.  */
+  size_t prognamelen = strlen (progname);
+  size_t messagelen = strlen (message);
+  static char const separator[] = {':', ' '};
+  char buf[sizeof alternate_signal_stack / 16 + sizeof separator];
+  idx_t buflen;
+  if (prognamelen + messagelen < sizeof buf - sizeof separator)
+    {
+      char *p = mempcpy (buf, progname, prognamelen);
+      p = mempcpy (p, separator, sizeof separator);
+      p = mempcpy (p, message, messagelen);
+      *p++ = '\n';
+      buflen = p - buf;
+    }
+  else
+    {
+      ignore_value (write (STDERR_FILENO, progname, prognamelen));
+      ignore_value (write (STDERR_FILENO, separator, sizeof separator));
+      ignore_value (write (STDERR_FILENO, message, messagelen));
+      buf[0] = '\n';
+      buflen = 1;
+    }
+  ignore_value (write (STDERR_FILENO, buf, buflen));
+
+  if (! signo)
+    _exit (exit_failure);
+  raise (signo);
+  abort ();
+}
+
+static _GL_ASYNC_SAFE void
+null_action (int signo _GL_UNUSED)
+{
+}
+
+/* Pacify GCC 9.3.1, which otherwise would complain about segv_handler.  */
+# if 4 < __GNUC__ + (6 <= __GNUC_MINOR__)
+#  pragma GCC diagnostic ignored "-Wsuggest-attribute=pure"
+# endif
+
+/* Nonzero if general segv handler could not be installed.  */
+static volatile int segv_handler_missing;
+
+/* Handle a segmentation violation and exit if it cannot be stack
+   overflow.  This function is async-signal-safe.  */
+
+static _GL_ASYNC_SAFE int
+segv_handler (void *address _GL_UNUSED, int serious)
+{
+# if DEBUG
+  {
+    char buf[1024];
+    int saved_errno = errno;
+    ignore_value (write (STDERR_FILENO, buf,
+                         sprintf (buf, "segv_handler serious=%d\n", serious)));
+    errno = saved_errno;
+  }
+# endif
+
+  /* If this fault is not serious, return 0 to let the stack overflow
+     handler take a shot at it.  */
+  if (!serious)
+    return 0;
+  die (SIGSEGV);
+}
+
+/* Handle a segmentation violation that is likely to be a stack
+   overflow and exit.  This function is async-signal-safe.  */
+
+static _GL_ASYNC_SAFE _Noreturn void
+overflow_handler (int emergency, stackoverflow_context_t context _GL_UNUSED)
+{
+# if DEBUG
+  {
+    char buf[1024];
+    ignore_value (write (STDERR_FILENO, buf,
+                         sprintf (buf, ("overflow_handler emergency=%d"
+                                        " segv_handler_missing=%d\n"),
+                                  emergency, segv_handler_missing)));
+  }
+# endif
+
+  die ((!emergency || segv_handler_missing) ? 0 : SIGSEGV);
+}
+
+int
+c_stack_action (_GL_ASYNC_SAFE void (*action) (int))
+{
+  segv_action = action ? action : null_action;
+  program_error_message = _("program error");
+  stack_overflow_message = _("stack overflow");
+  progname = getprogname ();
+
+  /* Always install the overflow handler.  */
+  if (stackoverflow_install_handler (overflow_handler,
+                                     alternate_signal_stack,
+                                     sizeof alternate_signal_stack))
+    {
+      errno = ENOTSUP;
+      return -1;
+    }
+  /* Try installing a general handler; if it fails, then treat all
+     segv as stack overflow.  */
+  segv_handler_missing = sigsegv_install_handler (segv_handler);
+  return 0;
+}
+
+#else /* !HAVE_STACK_OVERFLOW_RECOVERY */
+
+int
+c_stack_action (_GL_ASYNC_SAFE void (*action) (int)  _GL_UNUSED)
+{
+  errno = ENOTSUP;
+  return -1;
+}
+
+#endif