trap.c

android-w.song.android.widget

/* trap.c -- Not the trap command, but useful functions for manipulating
   those objects.  The trap command is in builtins/trap.def. */

/* Copyright (C) 1987-2010 Free Software Foundation, Inc.

   This file is part of GNU Bash, the Bourne Again SHell.

   Bash 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.

   Bash 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 Bash.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "config.h"

#if defined (HAVE_UNISTD_H)
#  include <unistd.h>
#endif

#include "bashtypes.h"
#include "bashansi.h"

#include <stdio.h>
#include <errno.h>

#include "bashintl.h"

#include "trap.h"

#include "shell.h"
#include "flags.h"
#include "input.h"	/* for save_token_state, restore_token_state */
#include "jobs.h"
#include "signames.h"
#include "builtins.h"
#include "builtins/common.h"
#include "builtins/builtext.h"

#ifndef errno
extern int errno;
#endif

/* Flags which describe the current handling state of a signal. */
#define SIG_INHERITED   0x0	/* Value inherited from parent. */
#define SIG_TRAPPED     0x1	/* Currently trapped. */
#define SIG_HARD_IGNORE 0x2	/* Signal was ignored on shell entry. */
#define SIG_SPECIAL     0x4	/* Treat this signal specially. */
#define SIG_NO_TRAP     0x8	/* Signal cannot be trapped. */
#define SIG_INPROGRESS	0x10	/* Signal handler currently executing. */
#define SIG_CHANGED	0x20	/* Trap value changed in trap handler. */
#define SIG_IGNORED	0x40	/* The signal is currently being ignored. */

#define SPECIAL_TRAP(s)	((s) == EXIT_TRAP || (s) == DEBUG_TRAP || (s) == ERROR_TRAP || (s) == RETURN_TRAP)

/* An array of such flags, one for each signal, describing what the
   shell will do with a signal.  DEBUG_TRAP == NSIG; some code below
   assumes this. */
static int sigmodes[BASH_NSIG];

static void free_trap_command __P((int));
static void change_signal __P((int, char *));

static void get_original_signal __P((int));

static int _run_trap_internal __P((int, char *));

static void free_trap_string __P((int));
static void reset_signal __P((int));
static void restore_signal __P((int));
static void reset_or_restore_signal_handlers __P((sh_resetsig_func_t *));

/* Variables used here but defined in other files. */
extern int last_command_exit_value;
extern int line_number;

extern char *this_command_name;
extern sh_builtin_func_t *this_shell_builtin;
extern procenv_t wait_intr_buf;
extern int return_catch_flag, return_catch_value;
extern int subshell_level;
extern WORD_LIST *subst_assign_varlist;

/* The list of things to do originally, before we started trapping. */
SigHandler *original_signals[NSIG];

/* For each signal, a slot for a string, which is a command to be
   executed when that signal is recieved.  The slot can also contain
   DEFAULT_SIG, which means do whatever you were going to do before
   you were so rudely interrupted, or IGNORE_SIG, which says ignore
   this signal. */
char *trap_list[BASH_NSIG];

/* A bitmap of signals received for which we have trap handlers. */
int pending_traps[NSIG];

/* Set to the number of the signal we're running the trap for + 1.
   Used in execute_cmd.c and builtins/common.c to clean up when
   parse_and_execute does not return normally after executing the
   trap command (e.g., when `return' is executed in the trap command). */
int running_trap;

/* Set to last_command_exit_value before running a trap. */
int trap_saved_exit_value;

/* The (trapped) signal received while executing in the `wait' builtin */
int wait_signal_received;

#define GETORIGSIG(sig) \
  do { \
    original_signals[sig] = (SigHandler *)set_signal_handler (sig, SIG_DFL); \
    set_signal_handler (sig, original_signals[sig]); \
    if (original_signals[sig] == SIG_IGN) \
      sigmodes[sig] |= SIG_HARD_IGNORE; \
  } while (0)

#define SETORIGSIG(sig,handler) \
  do { \
    original_signals[sig] = handler; \
    if (original_signals[sig] == SIG_IGN) \
      sigmodes[sig] |= SIG_HARD_IGNORE; \
  } while (0)

#define GET_ORIGINAL_SIGNAL(sig) \
  if (sig && sig < NSIG && original_signals[sig] == IMPOSSIBLE_TRAP_HANDLER) \
    GETORIGSIG(sig)

void
initialize_traps ()
{
  register int i;

  initialize_signames();

  trap_list[EXIT_TRAP] = trap_list[DEBUG_TRAP] = trap_list[ERROR_TRAP] = trap_list[RETURN_TRAP] = (char *)NULL;
  sigmodes[EXIT_TRAP] = sigmodes[DEBUG_TRAP] = sigmodes[ERROR_TRAP] = sigmodes[RETURN_TRAP] = SIG_INHERITED;
  original_signals[EXIT_TRAP] = IMPOSSIBLE_TRAP_HANDLER;

  for (i = 1; i < NSIG; i++)
    {
      pending_traps[i] = 0;
      trap_list[i] = (char *)DEFAULT_SIG;
      sigmodes[i] = SIG_INHERITED;	/* XXX - only set, not used */
      original_signals[i] = IMPOSSIBLE_TRAP_HANDLER;
    }

  /* Show which signals are treated specially by the shell. */
#if defined (SIGCHLD)
  GETORIGSIG (SIGCHLD);
  sigmodes[SIGCHLD] |= (SIG_SPECIAL | SIG_NO_TRAP);
#endif /* SIGCHLD */

  GETORIGSIG (SIGINT);
  sigmodes[SIGINT] |= SIG_SPECIAL;

#if defined (__BEOS__)
  /* BeOS sets SIGINT to SIG_IGN! */
  original_signals[SIGINT] = SIG_DFL;
  sigmodes[SIGINT] &= ~SIG_HARD_IGNORE;
#endif

  GETORIGSIG (SIGQUIT);
  sigmodes[SIGQUIT] |= SIG_SPECIAL;

  if (interactive)
    {
      GETORIGSIG (SIGTERM);
      sigmodes[SIGTERM] |= SIG_SPECIAL;
    }
}

#ifdef INCLUDE_UNUSED
/* Return a printable representation of the trap handler for SIG. */
static char *
trap_handler_string (sig)
     int sig;
{
  if (trap_list[sig] == (char *)DEFAULT_SIG)
    return "DEFAULT_SIG";
  else if (trap_list[sig] == (char *)IGNORE_SIG)
    return "IGNORE_SIG";
  else if (trap_list[sig] == (char *)IMPOSSIBLE_TRAP_HANDLER)
    return "IMPOSSIBLE_TRAP_HANDLER";
  else if (trap_list[sig])
    return trap_list[sig];
  else
    return "NULL";
}
#endif

/* Return the print name of this signal. */
char *
signal_name (sig)
     int sig;
{
  char *ret;

  /* on cygwin32, signal_names[sig] could be null */
  ret = (sig >= BASH_NSIG || sig < 0 || signal_names[sig] == NULL)
	? _("invalid signal number")
	: signal_names[sig];

  return ret;
}

/* Turn a string into a signal number, or a number into
   a signal number.  If STRING is "2", "SIGINT", or "INT",
   then (int)2 is returned.  Return NO_SIG if STRING doesn't
   contain a valid signal descriptor. */
int
decode_signal (string, flags)
     char *string;
     int flags;
{
  intmax_t sig;
  char *name;

  if (legal_number (string, &sig))
    return ((sig >= 0 && sig < NSIG) ? (int)sig : NO_SIG);

  /* A leading `SIG' may be omitted. */
  for (sig = 0; sig < BASH_NSIG; sig++)
    {
      name = signal_names[sig];
      if (name == 0 || name[0] == '\0')
	continue;

      /* Check name without the SIG prefix first case sensitivly or
	 insensitively depending on whether flags includes DSIG_NOCASE */
      if (STREQN (name, "SIG", 3))
	{
	  name += 3;

	  if ((flags & DSIG_NOCASE) && strcasecmp (string, name) == 0)
	    return ((int)sig);
	  else if ((flags & DSIG_NOCASE) == 0 && strcmp (string, name) == 0)
	    return ((int)sig);
	  /* If we can't use the `SIG' prefix to match, punt on this
	     name now. */
	  else if ((flags & DSIG_SIGPREFIX) == 0)
	    continue;
	}

      /* Check name with SIG prefix case sensitively or insensitively
	 depending on whether flags includes DSIG_NOCASE */
      name = signal_names[sig];
      if ((flags & DSIG_NOCASE) && strcasecmp (string, name) == 0)
	return ((int)sig);
      else if ((flags & DSIG_NOCASE) == 0 && strcmp (string, name) == 0)
	return ((int)sig);
    }

  return (NO_SIG);
}

/* Non-zero when we catch a trapped signal. */
static int catch_flag;

void
run_pending_traps ()
{
  register int sig;
  int old_exit_value, *token_state;
  WORD_LIST *save_subst_varlist;
#if defined (ARRAY_VARS)
  ARRAY *ps;
#endif

  if (catch_flag == 0)		/* simple optimization */
    return;

  catch_flag = 0;

  /* Preserve $? when running trap. */
  old_exit_value = last_command_exit_value;
#if defined (ARRAY_VARS)
  ps = save_pipestatus_array ();
#endif

  for (sig = 1; sig < NSIG; sig++)
    {
      /* XXX this could be made into a counter by using
	 while (pending_traps[sig]--) instead of the if statement. */
      if (pending_traps[sig])
	{
#if defined (HAVE_POSIX_SIGNALS)
	  sigset_t set, oset;

	  sigemptyset (&set);
	  sigemptyset (&oset);

	  sigaddset (&set, sig);
	  sigprocmask (SIG_BLOCK, &set, &oset);
#else
#  if defined (HAVE_BSD_SIGNALS)
	  int oldmask = sigblock (sigmask (sig));
#  endif
#endif /* HAVE_POSIX_SIGNALS */

	  if (sig == SIGINT)
	    {
	      run_interrupt_trap ();
	      CLRINTERRUPT;
	    }
#if defined (JOB_CONTROL) && defined (SIGCHLD)
	  else if (sig == SIGCHLD &&
		   trap_list[SIGCHLD] != (char *)IMPOSSIBLE_TRAP_HANDLER &&
		   (sigmodes[SIGCHLD] & SIG_INPROGRESS) == 0)
	    {
	      run_sigchld_trap (pending_traps[sig]);	/* use as counter */
	    }
#endif
	  else if (trap_list[sig] == (char *)DEFAULT_SIG ||
		   trap_list[sig] == (char *)IGNORE_SIG ||
		   trap_list[sig] == (char *)IMPOSSIBLE_TRAP_HANDLER)
	    {
	      /* This is possible due to a race condition.  Say a bash
		 process has SIGTERM trapped.  A subshell is spawned
		 using { list; } & and the parent does something and kills
		 the subshell with SIGTERM.  It's possible for the subshell
		 to set pending_traps[SIGTERM] to 1 before the code in
		 execute_cmd.c eventually calls restore_original_signals
		 to reset the SIGTERM signal handler in the subshell.  The
		 next time run_pending_traps is called, pending_traps[SIGTERM]
		 will be 1, but the trap handler in trap_list[SIGTERM] will
		 be invalid (probably DEFAULT_SIG, but it could be IGNORE_SIG).
		 Unless we catch this, the subshell will dump core when
		 trap_list[SIGTERM] == DEFAULT_SIG, because DEFAULT_SIG is
		 usually 0x0. */
	      internal_warning (_("run_pending_traps: bad value in trap_list[%d]: %p"),
				sig, trap_list[sig]);
	      if (trap_list[sig] == (char *)DEFAULT_SIG)
		{
		  internal_warning (_("run_pending_traps: signal handler is SIG_DFL, resending %d (%s) to myself"), sig, signal_name (sig));
		  kill (getpid (), sig);
		}
	    }
	  else
	    {
	      token_state = save_token_state ();
	      save_subst_varlist = subst_assign_varlist;
	      subst_assign_varlist = 0;

	      parse_and_execute (savestring (trap_list[sig]), "trap", SEVAL_NONINT|SEVAL_NOHIST|SEVAL_RESETLINE);
	      restore_token_state (token_state);
	      free (token_state);

	      subst_assign_varlist = save_subst_varlist;
	    }

	  pending_traps[sig] = 0;

#if defined (HAVE_POSIX_SIGNALS)
	  sigprocmask (SIG_SETMASK, &oset, (sigset_t *)NULL);
#else
#  if defined (HAVE_BSD_SIGNALS)
	  sigsetmask (oldmask);
#  endif
#endif /* POSIX_VERSION */
	}
    }

#if defined (ARRAY_VARS)
  restore_pipestatus_array (ps);
#endif
  last_command_exit_value = old_exit_value;
}