hurd/hurd/signal.h

   1 /* Implementing POSIX.1 signals under the Hurd.
   2    Copyright (C) 1993-2017 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 = (struct hurd_sigstate **)
 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 = (struct hurd_sigstate **)
 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.  */
 179       ss = *location = _hurd_thread_sigstate (__mach_thread_self ());
 180     }
 181
 182   if (! __spin_try_lock (&ss->critical_section_lock))
 183     /* We are already in a critical section, so do nothing.  */
 184     return NULL;
 185
 186   /* With the critical section lock held no signal handler will run.
 187      Return our sigstate pointer; this will be passed to
 188      _hurd_critical_section_unlock to unlock it.  */
 189   return ss;
 190 }
 191
 192 _HURD_SIGNAL_H_EXTERN_INLINE void
 193 _hurd_critical_section_unlock (void *our_lock)
 194 {
 195   if (our_lock == NULL)
 196     /* The critical section lock was held when we began.  Do nothing.  */
 197     return;
 198   else
 199     {
 200       /* It was us who acquired the critical section lock.  Unlock it.  */
 201       struct hurd_sigstate *ss = (struct hurd_sigstate *) our_lock;
 202       sigset_t pending;
 203       __spin_lock (&ss->lock);
 204       __spin_unlock (&ss->critical_section_lock);
 205       pending = ss->pending & ~ss->blocked;
 206       __spin_unlock (&ss->lock);
 207       if (! __sigisemptyset (&pending))
 208         /* There are unblocked signals pending, which weren't
 209            delivered because we were in the critical section.
 210            Tell the signal thread to deliver them now.  */
 211         __msg_sig_post (_hurd_msgport, 0, 0, __mach_task_self ());
 212     }
 213 }
 214
 215 /* Convenient macros for simple uses of critical sections.
 216    These two must be used as a pair at the same C scoping level.  */
 217
 218 #define HURD_CRITICAL_BEGIN \
 219   { void *__hurd_critical__ = _hurd_critical_section_lock ()
 220 #define HURD_CRITICAL_END \
 221       _hurd_critical_section_unlock (__hurd_critical__); } while (0)
 222 \f
 223 /* Initialize the signal code, and start the signal thread.
 224    Arguments give the "init ints" from exec_startup.  */
 225
 226 extern void _hurdsig_init (const int *intarray, size_t intarraysize);
 227
 228 /* Initialize proc server-assisted fault recovery for the signal thread.  */
 229
 230 extern void _hurdsig_fault_init (void);
 231
 232 /* Raise a signal as described by SIGNO an DETAIL, on the thread whose
 233    sigstate SS points to.  If SS is a null pointer, this instead affects
 234    the calling thread.  */
 235
 236 extern int _hurd_raise_signal (struct hurd_sigstate *ss, int signo,
 237                                const struct hurd_signal_detail *detail);
 238
 239 /* Translate a Mach exception into a signal (machine-dependent).  */
 240
 241 extern void _hurd_exception2signal (struct hurd_signal_detail *detail,
 242                                     int *signo);
 243
 244
 245 /* Make the thread described by SS take the signal described by SIGNO and
 246    DETAIL.  If the process is traced, this will in fact stop with a SIGNO
 247    as the stop signal unless UNTRACED is nonzero.  When the signal can be
 248    considered delivered, sends a sig_post reply message on REPLY_PORT
 249    indicating success.  SS is not locked.  */
 250
 251 extern void _hurd_internal_post_signal (struct hurd_sigstate *ss,
 252                                         int signo,
 253                                         struct hurd_signal_detail *detail,
 254                                         mach_port_t reply_port,
 255                                         mach_msg_type_name_t reply_port_type,
 256                                         int untraced);
 257
 258 /* Set up STATE and SS to handle signal SIGNO by running HANDLER.  If
 259    RPC_WAIT is nonzero, the thread needs to wait for a pending RPC to
 260    finish before running the signal handler.  The handler is passed SIGNO,
 261    SIGCODE, and the returned `struct sigcontext' (which resides on the
 262    stack the handler will use, and which describes the state of the thread
 263    encoded in STATE before running the handler).  */
 264
 265 struct machine_thread_all_state;
 266 extern struct sigcontext *
 267 _hurd_setup_sighandler (struct hurd_sigstate *ss, __sighandler_t handler,
 268                         int signo, struct hurd_signal_detail *detail,
 269                         int rpc_wait, struct machine_thread_all_state *state);
 270
 271 /* Function run by the signal thread to receive from the signal port.  */
 272
 273 extern void _hurd_msgport_receive (void);
 274
 275 /* Set up STATE with a thread state that, when resumed, is
 276    like `longjmp (_hurd_sigthread_fault_env, 1)'.  */
 277
 278 extern void _hurd_initialize_fault_recovery_state (void *state);
 279
 280 /* Set up STATE to do the equivalent of `longjmp (ENV, VAL);'.  */
 281
 282 extern void _hurd_longjmp_thread_state (void *state, jmp_buf env, int value);
 283
 284 /* Function run for SIGINFO when its action is SIG_DFL and the current
 285    process is the session leader.  */
 286
 287 extern void _hurd_siginfo_handler (int);
 288
 289 /* Replacement for mach_msg used in RPCs to provide Hurd interruption
 290    semantics.  Args are all the same as for mach_msg.  intr-rpc.h arranges
 291    for this version to be used automatically by the RPC stubs the library
 292    builds in place of the normal mach_msg. */
 293 error_t _hurd_intr_rpc_mach_msg (mach_msg_header_t *msg,
 294                                  mach_msg_option_t option,
 295                                  mach_msg_size_t send_size,
 296                                  mach_msg_size_t rcv_size,
 297                                  mach_port_t rcv_name,
 298                                  mach_msg_timeout_t timeout,
 299                                  mach_port_t notify);
 300
 301
 302 /* Milliseconds to wait for an interruptible RPC to return after
 303    `interrupt_operation'.  */
 304
 305 extern mach_msg_timeout_t _hurd_interrupted_rpc_timeout;
 306
 307
 308 /* Mask of signals that cannot be caught, blocked, or ignored.  */
 309 #define _SIG_CANT_MASK  (__sigmask (SIGSTOP) | __sigmask (SIGKILL))
 310
 311 /* Do an RPC to a process's message port.
 312
 313    Each argument is an expression which returns an error code; each
 314    expression may be evaluated several times.  FETCH_MSGPORT_EXPR should
 315    fetch the appropriate message port and store it in the local variable
 316    `msgport'; it will be deallocated after use.  FETCH_REFPORT_EXPR should
 317    fetch the appropriate message port and store it in the local variable
 318    `refport' (if no reference port is needed in the call, then
 319    FETCH_REFPORT_EXPR should be simply KERN_SUCCESS or 0); if
 320    DEALLOC_REFPORT evaluates to nonzero it will be deallocated after use,
 321    otherwise the FETCH_REFPORT_EXPR must take care of user references to
 322    `refport'.  RPC_EXPR should perform the desired RPC operation using
 323    `msgport' and `refport'.
 324
 325    The reason for the complexity is that a process's message port and
 326    reference port may change between fetching those ports and completing an
 327    RPC using them (usually they change only when a process execs).  The RPC
 328    will fail with MACH_SEND_INVALID_DEST if the msgport dies before we can
 329    send the RPC request; or with MIG_SERVER_DIED if the msgport was
 330    destroyed after we sent the RPC request but before it was serviced.  In
 331    either of these cases, we retry the entire operation, discarding the old
 332    message and reference ports and fetch them anew.  */
 333
 334 #define HURD_MSGPORT_RPC(fetch_msgport_expr,                                  \
 335                          fetch_refport_expr, dealloc_refport,                 \
 336                          rpc_expr)                                            \
 337 ({                                                                            \
 338     error_t __err;                                                            \
 339     mach_port_t msgport, refport = MACH_PORT_NULL;                            \
 340     do                                                                        \
 341       {                                                                       \
 342         /* Get the message port.  */                                          \
 343         __err = (error_t) (fetch_msgport_expr);                               \
 344         if (__err)                                                            \
 345           break;                                                              \
 346         /* Get the reference port.  */                                        \
 347         __err = (error_t) (fetch_refport_expr);                               \
 348         if (__err)                                                            \
 349           {                                                                   \
 350             /* Couldn't get it; deallocate MSGPORT and fail.  */              \
 351             __mach_port_deallocate (__mach_task_self (), msgport);            \
 352             break;                                                            \
 353           }                                                                   \
 354         __err = (error_t) (rpc_expr);                                         \
 355         __mach_port_deallocate (__mach_task_self (), msgport);                \
 356         if ((dealloc_refport) && refport != MACH_PORT_NULL)                   \
 357           __mach_port_deallocate (__mach_task_self (), refport);              \
 358       } while (__err == MACH_SEND_INVALID_DEST ||                             \
 359                __err == MIG_SERVER_DIED);                                     \
 360     __err;                                                                    \
 361 })
 362
 363
 364 #endif  /* hurd/signal.h */