hurd/hurd/signal.h

   1 /* Implementing POSIX.1 signals under the Hurd.
   2    Copyright (C) 1993-2014 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library 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 GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #ifndef _HURD_SIGNAL_H
  20
  21 #define _HURD_SIGNAL_H  1
  22 #include <features.h>
  23 /* Make sure <signal.h> is going to define NSIG.  */
  24 #ifndef __USE_GNU
  25 #error "Must have `_GNU_SOURCE' feature test macro to use this file"
  26 #endif
  27
  28 #define __need_size_t
  29 #define __need_NULL
  30 #include <stddef.h>
  31
  32 #include <mach/mach_types.h>
  33 #include <mach/port.h>
  34 #include <mach/message.h>
  35 #include <hurd/hurd_types.h>
  36 #include <signal.h>
  37 #include <errno.h>
  38 #include <hurd/msg.h>
  39
  40 #include <cthreads.h>           /* For `struct mutex'.  */
  41 #include <setjmp.h>             /* For `jmp_buf'.  */
  42 #include <spin-lock.h>
  43 #include <hurd/threadvar.h>     /* We cache sigstate in a threadvar.  */
  44 struct hurd_signal_preemptor;   /* <hurd/sigpreempt.h> */
  45
  46
  47 /* Full details of a signal.  */
  48 struct hurd_signal_detail
  49   {
  50     /* Codes from origination Mach exception_raise message.  */
  51     integer_t exc, exc_code, exc_subcode;
  52     /* Sigcode as passed or computed from exception codes.  */
  53     integer_t code;
  54     /* Error code as passed or extracted from exception codes.  */
  55     error_t error;
  56   };
  57
  58
  59 /* Per-thread signal state.  */
  60
  61 struct hurd_sigstate
  62   {
  63     spin_lock_t critical_section_lock; /* Held if in critical section.  */
  64
  65     spin_lock_t lock;           /* Locks most of the rest of the structure.  */
  66
  67     thread_t thread;
  68     struct hurd_sigstate *next; /* Linked-list of thread sigstates.  */
  69
  70     sigset_t blocked;           /* What signals are blocked.  */
  71     sigset_t pending;           /* Pending signals, possibly blocked.  */
  72     struct sigaction actions[NSIG];
  73     struct sigaltstack sigaltstack;
  74
  75     /* Chain of thread-local signal preemptors; see <hurd/sigpreempt.h>.
  76        Each element of this chain is in local stack storage, and the chain
  77        parallels the stack: the head of this chain is in the innermost
  78        stack frame, and each next element in an outermore frame.  */
  79     struct hurd_signal_preemptor *preemptors;
  80
  81     /* For each signal that may be pending, the details to deliver it with.  */
  82     struct hurd_signal_detail pending_data[NSIG];
  83
  84     /* If `suspended' is set when this thread gets a signal,
  85        the signal thread sends an empty message to it.  */
  86     mach_port_t suspended;
  87
  88     /* The following members are not locked.  They are used only by this
  89        thread, or by the signal thread with this thread suspended.  */
  90
  91     volatile mach_port_t intr_port; /* Port interruptible RPC was sent on.  */
  92
  93     /* If this is not null, the thread is in sigreturn awaiting delivery of
  94        pending signals.  This context (the machine-dependent portions only)
  95        will be passed to sigreturn after running the handler for a pending
  96        signal, instead of examining the thread state.  */
  97     struct sigcontext *context;
  98
  99     /* This is the head of the thread's list of active resources; see
 100        <hurd/userlink.h> for details.  This member is only used by the
 101        thread itself, and always inside a critical section.  */
 102     struct hurd_userlink *active_resources;
 103
 104     /* These are locked normally.  */
 105     int cancel;                 /* Flag set by hurd_thread_cancel.  */
 106     void (*cancel_hook) (void); /* Called on cancellation.  */
 107   };
 108
 109 /* Linked list of states of all threads whose state has been asked for.  */
 110
 111 extern struct hurd_sigstate *_hurd_sigstates;
 112
 113 extern struct mutex _hurd_siglock; /* Locks _hurd_sigstates.  */
 114
 115 /* Get the sigstate of a given thread, taking its lock.  */
 116
 117 extern struct hurd_sigstate *_hurd_thread_sigstate (thread_t);
 118
 119 /* Get the sigstate of the current thread.
 120    This uses a per-thread variable to optimize the lookup.  */
 121
 122 extern struct hurd_sigstate *_hurd_self_sigstate (void)
 123      /* This declaration tells the compiler that the value is constant.
 124         We assume this won't be called twice from the same stack frame
 125         by different threads.  */
 126      __attribute__ ((__const__));
 127
 128 #ifndef _HURD_SIGNAL_H_EXTERN_INLINE
 129 #define _HURD_SIGNAL_H_EXTERN_INLINE __extern_inline
 130 #endif
 131
 132 _HURD_SIGNAL_H_EXTERN_INLINE struct hurd_sigstate *
 133 _hurd_self_sigstate (void)
 134 {
 135   struct hurd_sigstate **location =
 136     (void *) __hurd_threadvar_location (_HURD_THREADVAR_SIGSTATE);
 137   if (*location == NULL)
 138     *location = _hurd_thread_sigstate (__mach_thread_self ());
 139   return *location;
 140 }
 141 \f
 142 /* Thread listening on our message port; also called the "signal thread".  */
 143
 144 extern thread_t _hurd_msgport_thread;
 145
 146 /* Our message port.  We hold the receive right and _hurd_msgport_thread
 147    listens for messages on it.  We also hold a send right, for convenience.  */
 148
 149 extern mach_port_t _hurd_msgport;
 150
 151
 152 /* Thread to receive process-global signals.  */
 153
 154 extern thread_t _hurd_sigthread;
 155
 156
 157 /* Resource limit on core file size.  Enforced by hurdsig.c.  */
 158 extern int _hurd_core_limit;
 159 \f
 160 /* Critical sections.
 161
 162    A critical section is a section of code which cannot safely be interrupted
 163    to run a signal handler; for example, code that holds any lock cannot be
 164    interrupted lest the signal handler try to take the same lock and
 165    deadlock result.  */
 166
 167 _HURD_SIGNAL_H_EXTERN_INLINE void *
 168 _hurd_critical_section_lock (void)
 169 {
 170   struct hurd_sigstate **location =
 171     (void *) __hurd_threadvar_location (_HURD_THREADVAR_SIGSTATE);
 172   struct hurd_sigstate *ss = *location;
 173   if (ss == NULL)
 174     {
 175       /* The thread variable is unset; this must be the first time we've
 176          asked for it.  In this case, the critical section flag cannot
 177          possible already be set.  Look up our sigstate structure the slow
 178          way; this locks the sigstate lock.  */
 179       ss = *location = _hurd_thread_sigstate (__mach_thread_self ());
 180       __spin_unlock (&ss->lock);
 181     }
 182
 183   if (! __spin_try_lock (&ss->critical_section_lock))
 184     /* We are already in a critical section, so do nothing.  */
 185     return NULL;
 186
 187   /* With the critical section lock held no signal handler will run.
 188      Return our sigstate pointer; this will be passed to
 189      _hurd_critical_section_unlock to unlock it.  */
 190   return ss;
 191 }
 192
 193 _HURD_SIGNAL_H_EXTERN_INLINE void
 194 _hurd_critical_section_unlock (void *our_lock)
 195 {
 196   if (our_lock == NULL)
 197     /* The critical section lock was held when we began.  Do nothing.  */
 198     return;
 199   else
 200     {
 201       /* It was us who acquired the critical section lock.  Unlock it.  */
 202       struct hurd_sigstate *ss = our_lock;
 203       sigset_t pending;
 204       __spin_lock (&ss->lock);
 205       __spin_unlock (&ss->critical_section_lock);
 206       pending = ss->pending & ~ss->blocked;
 207       __spin_unlock (&ss->lock);
 208       if (! __sigisemptyset (&pending))
 209         /* There are unblocked signals pending, which weren't
 210            delivered because we were in the critical section.
 211            Tell the signal thread to deliver them now.  */
 212         __msg_sig_post (_hurd_msgport, 0, 0, __mach_task_self ());
 213     }
 214 }
 215
 216 /* Convenient macros for simple uses of critical sections.
 217    These two must be used as a pair at the same C scoping level.  */
 218
 219 #define HURD_CRITICAL_BEGIN \
 220   { void *__hurd_critical__ = _hurd_critical_section_lock ()
 221 #define HURD_CRITICAL_END \
 222       _hurd_critical_section_unlock (__hurd_critical__); } while (0)
 223 \f
 224 /* Initialize the signal code, and start the signal thread.
 225    Arguments give the "init ints" from exec_startup.  */
 226
 227 extern void _hurdsig_init (const int *intarray, size_t intarraysize);
 228
 229 /* Initialize proc server-assisted fault recovery for the signal thread.  */
 230
 231 extern void _hurdsig_fault_init (void);
 232
 233 /* Raise a signal as described by SIGNO an DETAIL, on the thread whose
 234    sigstate SS points to.  If SS is a null pointer, this instead affects
 235    the calling thread.  */
 236
 237 extern void _hurd_raise_signal (struct hurd_sigstate *ss, int signo,
 238                                 const struct hurd_signal_detail *detail);
 239
 240 /* Translate a Mach exception into a signal (machine-dependent).  */
 241
 242 extern void _hurd_exception2signal (struct hurd_signal_detail *detail,
 243                                     int *signo);
 244
 245
 246 /* Make the thread described by SS take the signal described by SIGNO and
 247    DETAIL.  If the process is traced, this will in fact stop with a SIGNO
 248    as the stop signal unless UNTRACED is nonzero.  When the signal can be
 249    considered delivered, sends a sig_post reply message on REPLY_PORT
 250    indicating success.  SS is not locked.  */
 251
 252 extern void _hurd_internal_post_signal (struct hurd_sigstate *ss,
 253                                         int signo,
 254                                         struct hurd_signal_detail *detail,
 255                                         mach_port_t reply_port,
 256                                         mach_msg_type_name_t reply_port_type,
 257                                         int untraced);
 258
 259 /* Set up STATE and SS to handle signal SIGNO by running HANDLER.  If
 260    RPC_WAIT is nonzero, the thread needs to wait for a pending RPC to
 261    finish before running the signal handler.  The handler is passed SIGNO,
 262    SIGCODE, and the returned `struct sigcontext' (which resides on the
 263    stack the handler will use, and which describes the state of the thread
 264    encoded in STATE before running the handler).  */
 265
 266 struct machine_thread_all_state;
 267 extern struct sigcontext *
 268 _hurd_setup_sighandler (struct hurd_sigstate *ss, __sighandler_t handler,
 269                         int signo, struct hurd_signal_detail *detail,
 270                         int rpc_wait, struct machine_thread_all_state *state);
 271
 272 /* Function run by the signal thread to receive from the signal port.  */
 273
 274 extern void _hurd_msgport_receive (void);
 275
 276 /* Set up STATE with a thread state that, when resumed, is
 277    like `longjmp (_hurd_sigthread_fault_env, 1)'.  */
 278
 279 extern void _hurd_initialize_fault_recovery_state (void *state);
 280
 281 /* Set up STATE to do the equivalent of `longjmp (ENV, VAL);'.  */
 282
 283 extern void _hurd_longjmp_thread_state (void *state, jmp_buf env, int value);
 284
 285 /* Function run for SIGINFO when its action is SIG_DFL and the current
 286    process is the session leader.  */
 287
 288 extern void _hurd_siginfo_handler (int);
 289
 290 /* Replacement for mach_msg used in RPCs to provide Hurd interruption
 291    semantics.  Args are all the same as for mach_msg.  intr-rpc.h arranges
 292    for this version to be used automatically by the RPC stubs the library
 293    builds in place of the normal mach_msg. */
 294 error_t _hurd_intr_rpc_mach_msg (mach_msg_header_t *msg,
 295                                  mach_msg_option_t option,
 296                                  mach_msg_size_t send_size,
 297                                  mach_msg_size_t rcv_size,
 298                                  mach_port_t rcv_name,
 299                                  mach_msg_timeout_t timeout,
 300                                  mach_port_t notify);
 301
 302
 303 /* Milliseconds to wait for an interruptible RPC to return after
 304    `interrupt_operation'.  */
 305
 306 extern mach_msg_timeout_t _hurd_interrupted_rpc_timeout;
 307
 308
 309 /* Mask of signals that cannot be caught, blocked, or ignored.  */
 310 #define _SIG_CANT_MASK  (__sigmask (SIGSTOP) | __sigmask (SIGKILL))
 311
 312 /* Do an RPC to a process's message port.
 313
 314    Each argument is an expression which returns an error code; each
 315    expression may be evaluated several times.  FETCH_MSGPORT_EXPR should
 316    fetch the appropriate message port and store it in the local variable
 317    `msgport'; it will be deallocated after use.  FETCH_REFPORT_EXPR should
 318    fetch the appropriate message port and store it in the local variable
 319    `refport' (if no reference port is needed in the call, then
 320    FETCH_REFPORT_EXPR should be simply KERN_SUCCESS or 0); if
 321    DEALLOC_REFPORT evaluates to nonzero it will be deallocated after use,
 322    otherwise the FETCH_REFPORT_EXPR must take care of user references to
 323    `refport'.  RPC_EXPR should perform the desired RPC operation using
 324    `msgport' and `refport'.
 325
 326    The reason for the complexity is that a process's message port and
 327    reference port may change between fetching those ports and completing an
 328    RPC using them (usually they change only when a process execs).  The RPC
 329    will fail with MACH_SEND_INVALID_DEST if the msgport dies before we can
 330    send the RPC request; or with MIG_SERVER_DIED if the msgport was
 331    destroyed after we sent the RPC request but before it was serviced.  In
 332    either of these cases, we retry the entire operation, discarding the old
 333    message and reference ports and fetch them anew.  */
 334
 335 #define HURD_MSGPORT_RPC(fetch_msgport_expr,                                  \
 336                          fetch_refport_expr, dealloc_refport,                 \
 337                          rpc_expr)                                            \
 338 ({                                                                            \
 339     error_t __err;                                                            \
 340     mach_port_t msgport, refport = MACH_PORT_NULL;                            \
 341     do                                                                        \
 342       {                                                                       \
 343         /* Get the message port.  */                                          \
 344         __err = (fetch_msgport_expr);                                         \
 345         if (__err)                                                            \
 346           break;                                                              \
 347         /* Get the reference port.  */                                        \
 348         __err = (fetch_refport_expr);                                         \
 349         if (__err)                                                            \
 350           {                                                                   \
 351             /* Couldn't get it; deallocate MSGPORT and fail.  */              \
 352             __mach_port_deallocate (__mach_task_self (), msgport);            \
 353             break;                                                            \
 354           }                                                                   \
 355         __err = (rpc_expr);                                                   \
 356         __mach_port_deallocate (__mach_task_self (), msgport);                \
 357         if ((dealloc_refport) && refport != MACH_PORT_NULL)                   \
 358           __mach_port_deallocate (__mach_task_self (), refport);              \
 359       } while (__err == MACH_SEND_INVALID_DEST ||                             \
 360                __err == MIG_SERVER_DIED);                                     \
 361     __err;                                                                    \
 362 })
 363
 364
 365 #endif  /* hurd/signal.h */