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/* Implementing POSIX.1 signals under the Hurd.
Copyright (C) 1993-2014 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
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
<>. */
#ifndef _HURD_SIGNAL_H
#define _HURD_SIGNAL_H 1
#include <features.h>
/* Make sure <signal.h> is going to define NSIG. */
#ifndef __USE_GNU
#error "Must have `_GNU_SOURCE' feature test macro to use this file"
#define __need_size_t
#define __need_NULL
#include <stddef.h>
#include <mach/mach_types.h>
#include <mach/port.h>
#include <mach/message.h>
#include <hurd/hurd_types.h>
#include <signal.h>
#include <errno.h>
#include <hurd/msg.h>
#include <cthreads.h> /* For `struct mutex'. */
#include <setjmp.h> /* For `jmp_buf'. */
#include <spin-lock.h>
#include <hurd/threadvar.h> /* We cache sigstate in a threadvar. */
struct hurd_signal_preemptor; /* <hurd/sigpreempt.h> */
/* Full details of a signal. */
struct hurd_signal_detail
/* Codes from origination Mach exception_raise message. */
integer_t exc, exc_code, exc_subcode;
/* Sigcode as passed or computed from exception codes. */
integer_t code;
/* Error code as passed or extracted from exception codes. */
error_t error;
/* Per-thread signal state. */
struct hurd_sigstate
spin_lock_t critical_section_lock; /* Held if in critical section. */
spin_lock_t lock; /* Locks most of the rest of the structure. */
thread_t thread;
struct hurd_sigstate *next; /* Linked-list of thread sigstates. */
sigset_t blocked; /* What signals are blocked. */
sigset_t pending; /* Pending signals, possibly blocked. */
struct sigaction actions[NSIG];
struct sigaltstack sigaltstack;
/* Chain of thread-local signal preemptors; see <hurd/sigpreempt.h>.
Each element of this chain is in local stack storage, and the chain
parallels the stack: the head of this chain is in the innermost
stack frame, and each next element in an outermore frame. */
struct hurd_signal_preemptor *preemptors;
/* For each signal that may be pending, the details to deliver it with. */
struct hurd_signal_detail pending_data[NSIG];
/* If `suspended' is set when this thread gets a signal,
the signal thread sends an empty message to it. */
mach_port_t suspended;
/* The following members are not locked. They are used only by this
thread, or by the signal thread with this thread suspended. */
volatile mach_port_t intr_port; /* Port interruptible RPC was sent on. */
/* If this is not null, the thread is in sigreturn awaiting delivery of
pending signals. This context (the machine-dependent portions only)
will be passed to sigreturn after running the handler for a pending
signal, instead of examining the thread state. */
struct sigcontext *context;
/* This is the head of the thread's list of active resources; see
<hurd/userlink.h> for details. This member is only used by the
thread itself, and always inside a critical section. */
struct hurd_userlink *active_resources;
/* These are locked normally. */
int cancel; /* Flag set by hurd_thread_cancel. */
void (*cancel_hook) (void); /* Called on cancellation. */
/* Linked list of states of all threads whose state has been asked for. */
extern struct hurd_sigstate *_hurd_sigstates;
extern struct mutex _hurd_siglock; /* Locks _hurd_sigstates. */
/* Get the sigstate of a given thread, taking its lock. */
extern struct hurd_sigstate *_hurd_thread_sigstate (thread_t);
/* Get the sigstate of the current thread.
This uses a per-thread variable to optimize the lookup. */
extern struct hurd_sigstate *_hurd_self_sigstate (void)
/* This declaration tells the compiler that the value is constant.
We assume this won't be called twice from the same stack frame
by different threads. */
__attribute__ ((__const__));
#define _HURD_SIGNAL_H_EXTERN_INLINE __extern_inline
_HURD_SIGNAL_H_EXTERN_INLINE struct hurd_sigstate *
_hurd_self_sigstate (void)
struct hurd_sigstate **location =
(void *) __hurd_threadvar_location (_HURD_THREADVAR_SIGSTATE);
if (*location == NULL)
*location = _hurd_thread_sigstate (__mach_thread_self ());
return *location;
/* Thread listening on our message port; also called the "signal thread". */
extern thread_t _hurd_msgport_thread;
/* Our message port. We hold the receive right and _hurd_msgport_thread
listens for messages on it. We also hold a send right, for convenience. */
extern mach_port_t _hurd_msgport;
/* Thread to receive process-global signals. */
extern thread_t _hurd_sigthread;
/* Resource limit on core file size. Enforced by hurdsig.c. */
extern int _hurd_core_limit;
/* Critical sections.
A critical section is a section of code which cannot safely be interrupted
to run a signal handler; for example, code that holds any lock cannot be
interrupted lest the signal handler try to take the same lock and
deadlock result. */
_hurd_critical_section_lock (void)
struct hurd_sigstate **location =
(void *) __hurd_threadvar_location (_HURD_THREADVAR_SIGSTATE);
struct hurd_sigstate *ss = *location;
if (ss == NULL)
/* The thread variable is unset; this must be the first time we've
asked for it. In this case, the critical section flag cannot
possible already be set. Look up our sigstate structure the slow
way; this locks the sigstate lock. */
ss = *location = _hurd_thread_sigstate (__mach_thread_self ());
__spin_unlock (&ss->lock);
if (! __spin_try_lock (&ss->critical_section_lock))
/* We are already in a critical section, so do nothing. */
return NULL;
/* With the critical section lock held no signal handler will run.
Return our sigstate pointer; this will be passed to
_hurd_critical_section_unlock to unlock it. */
return ss;
_hurd_critical_section_unlock (void *our_lock)
if (our_lock == NULL)
/* The critical section lock was held when we began. Do nothing. */
/* It was us who acquired the critical section lock. Unlock it. */
struct hurd_sigstate *ss = our_lock;
sigset_t pending;
__spin_lock (&ss->lock);
__spin_unlock (&ss->critical_section_lock);
pending = ss->pending & ~ss->blocked;
__spin_unlock (&ss->lock);
if (! __sigisemptyset (&pending))
/* There are unblocked signals pending, which weren't
delivered because we were in the critical section.
Tell the signal thread to deliver them now. */
__msg_sig_post (_hurd_msgport, 0, 0, __mach_task_self ());
/* Convenient macros for simple uses of critical sections.
These two must be used as a pair at the same C scoping level. */
{ void *__hurd_critical__ = _hurd_critical_section_lock ()
_hurd_critical_section_unlock (__hurd_critical__); } while (0)
/* Initialize the signal code, and start the signal thread.
Arguments give the "init ints" from exec_startup. */
extern void _hurdsig_init (const int *intarray, size_t intarraysize);
/* Initialize proc server-assisted fault recovery for the signal thread. */
extern void _hurdsig_fault_init (void);
/* Raise a signal as described by SIGNO an DETAIL, on the thread whose
sigstate SS points to. If SS is a null pointer, this instead affects
the calling thread. */
extern void _hurd_raise_signal (struct hurd_sigstate *ss, int signo,
const struct hurd_signal_detail *detail);
/* Translate a Mach exception into a signal (machine-dependent). */
extern void _hurd_exception2signal (struct hurd_signal_detail *detail,
int *signo);
/* Make the thread described by SS take the signal described by SIGNO and
DETAIL. If the process is traced, this will in fact stop with a SIGNO
as the stop signal unless UNTRACED is nonzero. When the signal can be
considered delivered, sends a sig_post reply message on REPLY_PORT
indicating success. SS is not locked. */
extern void _hurd_internal_post_signal (struct hurd_sigstate *ss,
int signo,
struct hurd_signal_detail *detail,
mach_port_t reply_port,
mach_msg_type_name_t reply_port_type,
int untraced);
/* Set up STATE and SS to handle signal SIGNO by running HANDLER. If
RPC_WAIT is nonzero, the thread needs to wait for a pending RPC to
finish before running the signal handler. The handler is passed SIGNO,
SIGCODE, and the returned `struct sigcontext' (which resides on the
stack the handler will use, and which describes the state of the thread
encoded in STATE before running the handler). */
struct machine_thread_all_state;
extern struct sigcontext *
_hurd_setup_sighandler (struct hurd_sigstate *ss, __sighandler_t handler,
int signo, struct hurd_signal_detail *detail,
int rpc_wait, struct machine_thread_all_state *state);
/* Function run by the signal thread to receive from the signal port. */
extern void _hurd_msgport_receive (void);
/* Set up STATE with a thread state that, when resumed, is
like `longjmp (_hurd_sigthread_fault_env, 1)'. */
extern void _hurd_initialize_fault_recovery_state (void *state);
/* Set up STATE to do the equivalent of `longjmp (ENV, VAL);'. */
extern void _hurd_longjmp_thread_state (void *state, jmp_buf env, int value);
/* Function run for SIGINFO when its action is SIG_DFL and the current
process is the session leader. */
extern void _hurd_siginfo_handler (int);
/* Replacement for mach_msg used in RPCs to provide Hurd interruption
semantics. Args are all the same as for mach_msg. intr-rpc.h arranges
for this version to be used automatically by the RPC stubs the library
builds in place of the normal mach_msg. */
error_t _hurd_intr_rpc_mach_msg (mach_msg_header_t *msg,
mach_msg_option_t option,
mach_msg_size_t send_size,
mach_msg_size_t rcv_size,
mach_port_t rcv_name,
mach_msg_timeout_t timeout,
mach_port_t notify);
/* Milliseconds to wait for an interruptible RPC to return after
`interrupt_operation'. */
extern mach_msg_timeout_t _hurd_interrupted_rpc_timeout;
/* Mask of signals that cannot be caught, blocked, or ignored. */
#define _SIG_CANT_MASK (__sigmask (SIGSTOP) | __sigmask (SIGKILL))
/* Do an RPC to a process's message port.
Each argument is an expression which returns an error code; each
expression may be evaluated several times. FETCH_MSGPORT_EXPR should
fetch the appropriate message port and store it in the local variable
`msgport'; it will be deallocated after use. FETCH_REFPORT_EXPR should
fetch the appropriate message port and store it in the local variable
`refport' (if no reference port is needed in the call, then
FETCH_REFPORT_EXPR should be simply KERN_SUCCESS or 0); if
DEALLOC_REFPORT evaluates to nonzero it will be deallocated after use,
otherwise the FETCH_REFPORT_EXPR must take care of user references to
`refport'. RPC_EXPR should perform the desired RPC operation using
`msgport' and `refport'.
The reason for the complexity is that a process's message port and
reference port may change between fetching those ports and completing an
RPC using them (usually they change only when a process execs). The RPC
will fail with MACH_SEND_INVALID_DEST if the msgport dies before we can
send the RPC request; or with MIG_SERVER_DIED if the msgport was
destroyed after we sent the RPC request but before it was serviced. In
either of these cases, we retry the entire operation, discarding the old
message and reference ports and fetch them anew. */
#define HURD_MSGPORT_RPC(fetch_msgport_expr, \
fetch_refport_expr, dealloc_refport, \
rpc_expr) \
({ \
error_t __err; \
mach_port_t msgport, refport = MACH_PORT_NULL; \
do \
{ \
/* Get the message port. */ \
__err = (fetch_msgport_expr); \
if (__err) \
break; \
/* Get the reference port. */ \
__err = (fetch_refport_expr); \
if (__err) \
{ \
/* Couldn't get it; deallocate MSGPORT and fail. */ \
__mach_port_deallocate (__mach_task_self (), msgport); \
break; \
} \
__err = (rpc_expr); \
__mach_port_deallocate (__mach_task_self (), msgport); \
if ((dealloc_refport) && refport != MACH_PORT_NULL) \
__mach_port_deallocate (__mach_task_self (), refport); \
} while (__err == MACH_SEND_INVALID_DEST || \
__err == MIG_SERVER_DIED); \
__err; \
#endif /* hurd/signal.h */