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glibc/signal/signal.h
H.J. Lu 6c57d32048 sysconf: Add _SC_MINSIGSTKSZ/_SC_SIGSTKSZ [BZ #20305] 
Add _SC_MINSIGSTKSZ for the minimum signal stack size derived from
AT_MINSIGSTKSZ, which is the minimum number of bytes of free stack
space required in order to gurantee successful, non-nested handling
of a single signal whose handler is an empty function, and _SC_SIGSTKSZ
which is the suggested minimum number of bytes of stack space required
for a signal stack.

If AT_MINSIGSTKSZ isn't available, sysconf (_SC_MINSIGSTKSZ) returns
MINSIGSTKSZ.  On Linux/x86 with XSAVE, the signal frame used by kernel
is composed of the following areas and laid out as:

 ------------------------------
 | alignment padding          |
 ------------------------------
 | xsave buffer               |
 ------------------------------
 | fsave header (32-bit only) |
 ------------------------------
 | siginfo + ucontext         |
 ------------------------------

Compute AT_MINSIGSTKSZ value as size of xsave buffer + size of fsave
header (32-bit only) + size of siginfo and ucontext + alignment padding.

If _SC_SIGSTKSZ_SOURCE or _GNU_SOURCE are defined, MINSIGSTKSZ and SIGSTKSZ
are redefined as

/* Default stack size for a signal handler: sysconf (SC_SIGSTKSZ).  */
 # undef SIGSTKSZ
 # define SIGSTKSZ sysconf (_SC_SIGSTKSZ)

/* Minimum stack size for a signal handler: SIGSTKSZ.  */
 # undef MINSIGSTKSZ
 # define MINSIGSTKSZ SIGSTKSZ

Compilation will fail if the source assumes constant MINSIGSTKSZ or
SIGSTKSZ.

The reason for not simply increasing the kernel's MINSIGSTKSZ #define
(apart from the fact that it is rarely used, due to glibc's shadowing
definitions) was that userspace binaries will have baked in the old
value of the constant and may be making assumptions about it.

For example, the type (char [MINSIGSTKSZ]) changes if this #define
changes.  This could be a problem if an newly built library tries to
memcpy() or dump such an object defined by and old binary.
Bounds-checking and the stack sizes passed to things like sigaltstack()
and makecontext() could similarly go wrong.
2021-02-01 11:00:52 -08:00

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/* Copyright (C) 1991-2021 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
/*
* ISO C99 Standard: 7.14 Signal handling <signal.h>
*/
#ifndef _SIGNAL_H
#define _SIGNAL_H
#include <features.h>
__BEGIN_DECLS
#include <bits/types.h>
#include <bits/signum-generic.h>
#include <bits/types/sig_atomic_t.h>
#if defined __USE_POSIX
#include <bits/types/sigset_t.h>
#endif
#if defined __USE_XOPEN || defined __USE_XOPEN2K
# ifndef __pid_t_defined
typedef __pid_t pid_t;
# define __pid_t_defined
#endif
#ifdef __USE_XOPEN
# endif
# ifndef __uid_t_defined
typedef __uid_t uid_t;
# define __uid_t_defined
# endif
#endif /* Unix98 */
#ifdef __USE_POSIX199309
/* We need `struct timespec' later on. */
# include <bits/types/struct_timespec.h>
#endif
#if defined __USE_POSIX199309 || defined __USE_XOPEN_EXTENDED
# include <bits/types/siginfo_t.h>
# include <bits/siginfo-consts.h>
#endif
#ifdef __USE_MISC
# include <bits/types/sigval_t.h>
#endif
#ifdef __USE_POSIX199309
# include <bits/types/sigevent_t.h>
# include <bits/sigevent-consts.h>
#endif
/* Type of a signal handler. */
typedef void (*__sighandler_t) (int);
/* The X/Open definition of `signal' specifies the SVID semantic. Use
the additional function `sysv_signal' when X/Open compatibility is
requested. */
extern __sighandler_t __sysv_signal (int __sig, __sighandler_t __handler)
__THROW;
#ifdef __USE_GNU
extern __sighandler_t sysv_signal (int __sig, __sighandler_t __handler)
__THROW;
#endif
/* Set the handler for the signal SIG to HANDLER, returning the old
handler, or SIG_ERR on error.
By default `signal' has the BSD semantic. */
#ifdef __USE_MISC
extern __sighandler_t signal (int __sig, __sighandler_t __handler)
__THROW;
#else
/* Make sure the used `signal' implementation is the SVID version. */
# ifdef __REDIRECT_NTH
extern __sighandler_t __REDIRECT_NTH (signal,
(int __sig, __sighandler_t __handler),
__sysv_signal);
# else
# define signal __sysv_signal
# endif
#endif
#if defined __USE_XOPEN_EXTENDED && !defined __USE_XOPEN2K8
/* The X/Open definition of `signal' conflicts with the BSD version.
So they defined another function `bsd_signal'. */
extern __sighandler_t bsd_signal (int __sig, __sighandler_t __handler)
__THROW;
#endif
/* Send signal SIG to process number PID. If PID is zero,
send SIG to all processes in the current process's process group.
If PID is < -1, send SIG to all processes in process group - PID. */
#ifdef __USE_POSIX
extern int kill (__pid_t __pid, int __sig) __THROW;
#endif /* Use POSIX. */
#if defined __USE_MISC || defined __USE_XOPEN_EXTENDED
/* Send SIG to all processes in process group PGRP.
If PGRP is zero, send SIG to all processes in
the current process's process group. */
extern int killpg (__pid_t __pgrp, int __sig) __THROW;
#endif /* Use misc || X/Open Unix. */
/* Raise signal SIG, i.e., send SIG to yourself. */
extern int raise (int __sig) __THROW;
#ifdef __USE_MISC
/* SVID names for the same things. */
extern __sighandler_t ssignal (int __sig, __sighandler_t __handler)
__THROW;
extern int gsignal (int __sig) __THROW;
#endif /* Use misc. */
#ifdef __USE_XOPEN2K8
/* Print a message describing the meaning of the given signal number. */
extern void psignal (int __sig, const char *__s);
/* Print a message describing the meaning of the given signal information. */
extern void psiginfo (const siginfo_t *__pinfo, const char *__s);
#endif /* POSIX 2008. */
/* The `sigpause' function in X/Open defines the argument as the
signal number. This requires redirecting to another function
because the default version in glibc uses an old BSD interface.
This function is a cancellation point and therefore not marked with
__THROW. */
#ifdef __USE_XOPEN_EXTENDED
# ifdef __GNUC__
extern int sigpause (int __sig) __asm__ ("__xpg_sigpause")
__attribute_deprecated_msg__ ("Use the sigsuspend function instead");
# else
extern int __sigpause (int __sig_or_mask, int __is_sig);
/* Remove a signal from the signal mask and suspend the process. */
# define sigpause(sig) __sigpause ((sig), 1)
# endif
#endif
#ifdef __USE_MISC
/* None of the following functions should be used anymore. They are here
only for compatibility. A single word (`int') is not guaranteed to be
enough to hold a complete signal mask and therefore these functions
simply do not work in many situations. Use `sigprocmask' instead. */
/* Compute mask for signal SIG. */
# define sigmask(sig) \
__glibc_macro_warning ("sigmask is deprecated") \
((int)(1u << ((sig) - 1)))
/* Block signals in MASK, returning the old mask. */
extern int sigblock (int __mask) __THROW __attribute_deprecated__;
/* Set the mask of blocked signals to MASK, returning the old mask. */
extern int sigsetmask (int __mask) __THROW __attribute_deprecated__;
/* Return currently selected signal mask. */
extern int siggetmask (void) __THROW __attribute_deprecated__;
#endif /* Use misc. */
#ifdef __USE_MISC
# define NSIG _NSIG
#endif
#ifdef __USE_GNU
typedef __sighandler_t sighandler_t;
#endif
/* 4.4 BSD uses the name `sig_t' for this. */
#ifdef __USE_MISC
typedef __sighandler_t sig_t;
#endif
#ifdef __USE_POSIX
/* Clear all signals from SET. */
extern int sigemptyset (sigset_t *__set) __THROW __nonnull ((1));
/* Set all signals in SET. */
extern int sigfillset (sigset_t *__set) __THROW __nonnull ((1));
/* Add SIGNO to SET. */
extern int sigaddset (sigset_t *__set, int __signo) __THROW __nonnull ((1));
/* Remove SIGNO from SET. */
extern int sigdelset (sigset_t *__set, int __signo) __THROW __nonnull ((1));
/* Return 1 if SIGNO is in SET, 0 if not. */
extern int sigismember (const sigset_t *__set, int __signo)
__THROW __nonnull ((1));
# ifdef __USE_GNU
/* Return non-empty value is SET is not empty. */
extern int sigisemptyset (const sigset_t *__set) __THROW __nonnull ((1));
/* Build new signal set by combining the two inputs set using logical AND. */
extern int sigandset (sigset_t *__set, const sigset_t *__left,
const sigset_t *__right) __THROW __nonnull ((1, 2, 3));
/* Build new signal set by combining the two inputs set using logical OR. */
extern int sigorset (sigset_t *__set, const sigset_t *__left,
const sigset_t *__right) __THROW __nonnull ((1, 2, 3));
# endif /* GNU */
/* Get the system-specific definitions of `struct sigaction'
and the `SA_*' and `SIG_*'. constants. */
# include <bits/sigaction.h>
/* Get and/or change the set of blocked signals. */
extern int sigprocmask (int __how, const sigset_t *__restrict __set,
sigset_t *__restrict __oset) __THROW;
/* Change the set of blocked signals to SET,
wait until a signal arrives, and restore the set of blocked signals.
This function is a cancellation point and therefore not marked with
__THROW. */
extern int sigsuspend (const sigset_t *__set) __nonnull ((1));
/* Get and/or set the action for signal SIG. */
extern int sigaction (int __sig, const struct sigaction *__restrict __act,
struct sigaction *__restrict __oact) __THROW;
/* Put in SET all signals that are blocked and waiting to be delivered. */
extern int sigpending (sigset_t *__set) __THROW __nonnull ((1));
# ifdef __USE_POSIX199506
/* Select any of pending signals from SET or wait for any to arrive.
This function is a cancellation point and therefore not marked with
__THROW. */
extern int sigwait (const sigset_t *__restrict __set, int *__restrict __sig)
__nonnull ((1, 2));
# endif /* Use POSIX 1995. */
# ifdef __USE_POSIX199309
/* Select any of pending signals from SET and place information in INFO.
This function is a cancellation point and therefore not marked with
__THROW. */
extern int sigwaitinfo (const sigset_t *__restrict __set,
siginfo_t *__restrict __info) __nonnull ((1));
/* Select any of pending signals from SET and place information in INFO.
Wait the time specified by TIMEOUT if no signal is pending.
This function is a cancellation point and therefore not marked with
__THROW. */
extern int sigtimedwait (const sigset_t *__restrict __set,
siginfo_t *__restrict __info,
const struct timespec *__restrict __timeout)
__nonnull ((1));
/* Send signal SIG to the process PID. Associate data in VAL with the
signal. */
extern int sigqueue (__pid_t __pid, int __sig, const union sigval __val)
__THROW;
# endif /* Use POSIX 199306. */
#endif /* Use POSIX. */
#ifdef __USE_MISC
/* Get machine-dependent `struct sigcontext' and signal subcodes. */
# include <bits/sigcontext.h>
/* Restore the state saved in SCP. */
extern int sigreturn (struct sigcontext *__scp) __THROW;
#endif /* Use misc. */
#if defined __USE_XOPEN_EXTENDED || defined __USE_XOPEN2K8
# define __need_size_t
# include <stddef.h>
# include <bits/types/stack_t.h>
# if defined __USE_XOPEN || defined __USE_XOPEN2K8
/* This will define `ucontext_t' and `mcontext_t'. */
# include <sys/ucontext.h>
# endif
#endif /* Use POSIX.1-2008 or X/Open Unix. */
#if defined __USE_XOPEN_EXTENDED || defined __USE_MISC
/* If INTERRUPT is nonzero, make signal SIG interrupt system calls
(causing them to fail with EINTR); if INTERRUPT is zero, make system
calls be restarted after signal SIG. */
extern int siginterrupt (int __sig, int __interrupt) __THROW
__attribute_deprecated_msg__ ("Use sigaction with SA_RESTART instead");
# include <bits/sigstack.h>
# include <bits/sigstksz.h>
# include <bits/ss_flags.h>
/* Alternate signal handler stack interface.
This interface should always be preferred over `sigstack'. */
extern int sigaltstack (const stack_t *__restrict __ss,
stack_t *__restrict __oss) __THROW;
#endif /* __USE_XOPEN_EXTENDED || __USE_MISC */
#if ((defined __USE_XOPEN_EXTENDED && !defined __USE_XOPEN2K8) \
|| defined __USE_MISC)
# include <bits/types/struct_sigstack.h>
#endif
#if ((defined __USE_XOPEN_EXTENDED && !defined __USE_XOPEN2K) \
|| defined __USE_MISC)
/* Run signals handlers on the stack specified by SS (if not NULL).
If OSS is not NULL, it is filled in with the old signal stack status.
This interface is obsolete and on many platform not implemented. */
extern int sigstack (struct sigstack *__ss, struct sigstack *__oss)
__THROW __attribute_deprecated__;
#endif
#ifdef __USE_XOPEN_EXTENDED
/* Simplified interface for signal management. */
/* Add SIG to the calling process' signal mask. */
extern int sighold (int __sig) __THROW
__attribute_deprecated_msg__ ("Use the sigprocmask function instead");
/* Remove SIG from the calling process' signal mask. */
extern int sigrelse (int __sig) __THROW
__attribute_deprecated_msg__ ("Use the sigprocmask function instead");
/* Set the disposition of SIG to SIG_IGN. */
extern int sigignore (int __sig) __THROW
__attribute_deprecated_msg__ ("Use the signal function instead");
/* Set the disposition of SIG. */
extern __sighandler_t sigset (int __sig, __sighandler_t __disp) __THROW
__attribute_deprecated_msg__
("Use the signal and sigprocmask functions instead");
#endif
#if defined __USE_POSIX199506 || defined __USE_UNIX98
/* Some of the functions for handling signals in threaded programs must
be defined here. */
# include <bits/pthreadtypes.h>
# include <bits/sigthread.h>
#endif /* use Unix98 */
/* The following functions are used internally in the C library and in
other code which need deep insights. */
/* Return number of available real-time signal with highest priority. */
extern int __libc_current_sigrtmin (void) __THROW;
/* Return number of available real-time signal with lowest priority. */
extern int __libc_current_sigrtmax (void) __THROW;
#define SIGRTMIN (__libc_current_sigrtmin ())
#define SIGRTMAX (__libc_current_sigrtmax ())
/* System-specific extensions. */
#include <bits/signal_ext.h>
__END_DECLS
#endif /* not signal.h */
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