Implement 'catch syscall' for gdbserver

This adds a new QCatchSyscalls packet to enable 'catch syscall', and new
stop reasons "syscall_entry" and "syscall_return" for those events.  It
is currently only supported on Linux x86 and x86_64.

gdb/ChangeLog:

2016-01-12  Josh Stone  <jistone@redhat.com>
	    Philippe Waroquiers  <philippe.waroquiers@skynet.be>

	* NEWS (Changes since GDB 7.10): Mention QCatchSyscalls and the
	syscall_entry and syscall_return stop reasons.  Mention GDB
	support for remote catch syscall.
	* remote.c (PACKET_QCatchSyscalls): New enum.
	(remote_set_syscall_catchpoint): New function.
	(remote_protocol_features): New element for QCatchSyscalls.
	(remote_parse_stop_reply): Parse syscall_entry/return stops.
	(init_remote_ops): Install remote_set_syscall_catchpoint.
	(_initialize_remote): Config QCatchSyscalls.
	* linux-nat.h (struct lwp_info) <syscall_state>: Comment typo.

gdb/doc/ChangeLog:

2016-01-12  Josh Stone  <jistone@redhat.com>
	    Philippe Waroquiers  <philippe.waroquiers@skynet.be>

	* gdb.texinfo (Remote Configuration): List the QCatchSyscalls packet.
	(Stop Reply Packets): List the syscall entry and return stop reasons.
	(General Query Packets): Describe QCatchSyscalls, and add it to the
	table and the detailed list of stub features.

gdb/gdbserver/ChangeLog:

2016-01-12  Josh Stone  <jistone@redhat.com>
	    Philippe Waroquiers  <philippe.waroquiers@skynet.be>

	* inferiors.h: Include "gdb_vecs.h".
	(struct process_info): Add syscalls_to_catch.
	* inferiors.c (remove_process): Free syscalls_to_catch.
	* remote-utils.c (prepare_resume_reply): Report syscall_entry and
	syscall_return stops.
	* server.h (UNKNOWN_SYSCALL, ANY_SYSCALL): Define.
	* server.c (handle_general_set): Handle QCatchSyscalls.
	(handle_query): Report support for QCatchSyscalls.
	* target.h (struct target_ops): Add supports_catch_syscall.
	(target_supports_catch_syscall): New macro.
	* linux-low.h (struct linux_target_ops): Add get_syscall_trapinfo.
	(struct lwp_info): Add syscall_state.
	* linux-low.c (handle_extended_wait): Mark syscall_state as an entry.
	Maintain syscall_state and syscalls_to_catch across exec.
	(get_syscall_trapinfo): New function, proxy to the_low_target.
	(linux_low_ptrace_options): Enable PTRACE_O_TRACESYSGOOD.
	(linux_low_filter_event): Toggle syscall_state entry/return for
	syscall traps, and set it ignored for all others.
	(gdb_catching_syscalls_p): New function.
	(gdb_catch_this_syscall_p): New function.
	(linux_wait_1): Handle SYSCALL_SIGTRAP.
	(linux_resume_one_lwp_throw): Add PTRACE_SYSCALL possibility.
	(linux_supports_catch_syscall): New function.
	(linux_target_ops): Install it.
	* linux-x86-low.c (x86_get_syscall_trapinfo): New function.
	(the_low_target): Install it.

gdb/testsuite/ChangeLog:

2016-01-12  Josh Stone  <jistone@redhat.com>
	    Philippe Waroquiers  <philippe.waroquiers@skynet.be>

	* gdb.base/catch-syscall.c (do_execve): New variable.
	(main): Conditionally trigger an execve.
	* gdb.base/catch-syscall.exp: Enable testing for remote targets.
	(test_catch_syscall_execve): New, check entry/return across execve.
	(do_syscall_tests): Call test_catch_syscall_execve.

10 files changed, 305 insertions, 5 deletions

diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog
index 3c2d6db..757424c 100644
--- a/gdb/gdbserver/ChangeLog
+++ b/gdb/gdbserver/ChangeLog
@@ -1,3 +1,33 @@
+2016-01-12  Josh Stone  <jistone@redhat.com>
+	    Philippe Waroquiers  <philippe.waroquiers@skynet.be>
+
+	* inferiors.h: Include "gdb_vecs.h".
+	(struct process_info): Add syscalls_to_catch.
+	* inferiors.c (remove_process): Free syscalls_to_catch.
+	* remote-utils.c (prepare_resume_reply): Report syscall_entry and
+	syscall_return stops.
+	* server.h (UNKNOWN_SYSCALL, ANY_SYSCALL): Define.
+	* server.c (handle_general_set): Handle QCatchSyscalls.
+	(handle_query): Report support for QCatchSyscalls.
+	* target.h (struct target_ops): Add supports_catch_syscall.
+	(target_supports_catch_syscall): New macro.
+	* linux-low.h (struct linux_target_ops): Add get_syscall_trapinfo.
+	(struct lwp_info): Add syscall_state.
+	* linux-low.c (handle_extended_wait): Mark syscall_state as an entry.
+	Maintain syscall_state and syscalls_to_catch across exec.
+	(get_syscall_trapinfo): New function, proxy to the_low_target.
+	(linux_low_ptrace_options): Enable PTRACE_O_TRACESYSGOOD.
+	(linux_low_filter_event): Toggle syscall_state entry/return for
+	syscall traps, and set it ignored for all others.
+	(gdb_catching_syscalls_p): New function.
+	(gdb_catch_this_syscall_p): New function.
+	(linux_wait_1): Handle SYSCALL_SIGTRAP.
+	(linux_resume_one_lwp_throw): Add PTRACE_SYSCALL possibility.
+	(linux_supports_catch_syscall): New function.
+	(linux_target_ops): Install it.
+	* linux-x86-low.c (x86_get_syscall_trapinfo): New function.
+	(the_low_target): Install it.
+
 2016-01-12  Mike Frysinger  <vapier@gentoo.org>
 
 	* acinclude.m4: Include new ../warning.m4 file.
diff --git a/gdb/gdbserver/inferiors.c b/gdb/gdbserver/inferiors.c
index c884b55..4bea4fd 100644
--- a/gdb/gdbserver/inferiors.c
+++ b/gdb/gdbserver/inferiors.c
@@ -339,6 +339,7 @@ remove_process (struct process_info *process)
   free_all_breakpoints (process);
   gdb_assert (find_thread_process (process) == NULL);
   remove_inferior (&all_processes, &process->entry);
+  VEC_free (int, process->syscalls_to_catch);
   free (process);
 }
 
diff --git a/gdb/gdbserver/inferiors.h b/gdb/gdbserver/inferiors.h
index af65718..00dfe60 100644
--- a/gdb/gdbserver/inferiors.h
+++ b/gdb/gdbserver/inferiors.h
@@ -19,6 +19,8 @@
 #ifndef INFERIORS_H
 #define INFERIORS_H
 
+#include "gdb_vecs.h"
+
 /* Generic information for tracking a list of ``inferiors'' - threads,
    processes, etc.  */
 struct inferior_list
@@ -67,6 +69,10 @@ struct process_info
   /* The list of installed fast tracepoints.  */
   struct fast_tracepoint_jump *fast_tracepoint_jumps;
 
+  /* The list of syscalls to report, or just a single element, ANY_SYSCALL,
+     for unfiltered syscall reporting.  */
+  VEC (int) *syscalls_to_catch;
+
   const struct target_desc *tdesc;
 
   /* Private target data.  */
diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c
index 47f0f9d..7c77a2f 100644
--- a/gdb/gdbserver/linux-low.c
+++ b/gdb/gdbserver/linux-low.c
@@ -461,6 +461,11 @@ handle_extended_wait (struct lwp_info **orig_event_lwp, int wstat)
 
   gdb_assert (event_lwp->waitstatus.kind == TARGET_WAITKIND_IGNORE);
 
+  /* All extended events we currently use are mid-syscall.  Only
+     PTRACE_EVENT_STOP is delivered more like a signal-stop, but
+     you have to be using PTRACE_SEIZE to get that.  */
+  event_lwp->syscall_state = TARGET_WAITKIND_SYSCALL_ENTRY;
+
   if ((event == PTRACE_EVENT_FORK) || (event == PTRACE_EVENT_VFORK)
       || (event == PTRACE_EVENT_CLONE))
     {
@@ -611,6 +616,7 @@ handle_extended_wait (struct lwp_info **orig_event_lwp, int wstat)
   else if (event == PTRACE_EVENT_EXEC && report_exec_events)
     {
       struct process_info *proc;
+      VEC (int) *syscalls_to_catch;
       ptid_t event_ptid;
       pid_t event_pid;
 
@@ -624,8 +630,12 @@ handle_extended_wait (struct lwp_info **orig_event_lwp, int wstat)
       event_ptid = ptid_of (event_thr);
       event_pid = ptid_get_pid (event_ptid);
 
-      /* Delete the execing process and all its threads.  */
+      /* Save the syscall list from the execing process.  */
       proc = get_thread_process (event_thr);
+      syscalls_to_catch = proc->syscalls_to_catch;
+      proc->syscalls_to_catch = NULL;
+
+      /* Delete the execing process and all its threads.  */
       linux_mourn (proc);
       current_thread = NULL;
 
@@ -648,6 +658,14 @@ handle_extended_wait (struct lwp_info **orig_event_lwp, int wstat)
       event_thr->last_resume_kind = resume_continue;
       event_thr->last_status.kind = TARGET_WAITKIND_IGNORE;
 
+      /* Update syscall state in the new lwp, effectively mid-syscall too.  */
+      event_lwp->syscall_state = TARGET_WAITKIND_SYSCALL_ENTRY;
+
+      /* Restore the list to catch.  Don't rely on the client, which is free
+	 to avoid sending a new list when the architecture doesn't change.
+	 Also, for ANY_SYSCALL, the architecture doesn't really matter.  */
+      proc->syscalls_to_catch = syscalls_to_catch;
+
       /* Report the event.  */
       *orig_event_lwp = event_lwp;
       return 0;
@@ -682,6 +700,40 @@ get_pc (struct lwp_info *lwp)
   return pc;
 }
 
+/* This function should only be called if LWP got a SYSCALL_SIGTRAP.
+   Fill *SYSNO with the syscall nr trapped.  Fill *SYSRET with the
+   return code.  */
+
+static void
+get_syscall_trapinfo (struct lwp_info *lwp, int *sysno, int *sysret)
+{
+  struct thread_info *saved_thread;
+  struct regcache *regcache;
+
+  if (the_low_target.get_syscall_trapinfo == NULL)
+    {
+      /* If we cannot get the syscall trapinfo, report an unknown
+	 system call number and -ENOSYS return value.  */
+      *sysno = UNKNOWN_SYSCALL;
+      *sysret = -ENOSYS;
+      return;
+    }
+
+  saved_thread = current_thread;
+  current_thread = get_lwp_thread (lwp);
+
+  regcache = get_thread_regcache (current_thread, 1);
+  (*the_low_target.get_syscall_trapinfo) (regcache, sysno, sysret);
+
+  if (debug_threads)
+    {
+      debug_printf ("get_syscall_trapinfo sysno %d sysret %d\n",
+		    *sysno, *sysret);
+    }
+
+  current_thread = saved_thread;
+}
+
 /* This function should only be called if LWP got a SIGTRAP.
    The SIGTRAP could mean several things.
 
@@ -2236,6 +2288,8 @@ linux_low_ptrace_options (int attached)
   if (report_exec_events)
     options |= PTRACE_O_TRACEEXEC;
 
+  options |= PTRACE_O_TRACESYSGOOD;
+
   return options;
 }
 
@@ -2364,6 +2418,21 @@ linux_low_filter_event (int lwpid, int wstat)
       child->must_set_ptrace_flags = 0;
     }
 
+  /* Always update syscall_state, even if it will be filtered later.  */
+  if (WIFSTOPPED (wstat) && WSTOPSIG (wstat) == SYSCALL_SIGTRAP)
+    {
+      child->syscall_state
+	= (child->syscall_state == TARGET_WAITKIND_SYSCALL_ENTRY
+	   ? TARGET_WAITKIND_SYSCALL_RETURN
+	   : TARGET_WAITKIND_SYSCALL_ENTRY);
+    }
+  else
+    {
+      /* Almost all other ptrace-stops are known to be outside of system
+	 calls, with further exceptions in handle_extended_wait.  */
+      child->syscall_state = TARGET_WAITKIND_IGNORE;
+    }
+
   /* Be careful to not overwrite stop_pc until
      check_stopped_by_breakpoint is called.  */
   if (WIFSTOPPED (wstat) && WSTOPSIG (wstat) == SIGTRAP
@@ -2973,6 +3042,44 @@ filter_exit_event (struct lwp_info *event_child,
   return ptid;
 }
 
+/* Returns 1 if GDB is interested in any event_child syscalls.  */
+
+static int
+gdb_catching_syscalls_p (struct lwp_info *event_child)
+{
+  struct thread_info *thread = get_lwp_thread (event_child);
+  struct process_info *proc = get_thread_process (thread);
+
+  return !VEC_empty (int, proc->syscalls_to_catch);
+}
+
+/* Returns 1 if GDB is interested in the event_child syscall.
+   Only to be called when stopped reason is SYSCALL_SIGTRAP.  */
+
+static int
+gdb_catch_this_syscall_p (struct lwp_info *event_child)
+{
+  int i, iter;
+  int sysno, sysret;
+  struct thread_info *thread = get_lwp_thread (event_child);
+  struct process_info *proc = get_thread_process (thread);
+
+  if (VEC_empty (int, proc->syscalls_to_catch))
+    return 0;
+
+  if (VEC_index (int, proc->syscalls_to_catch, 0) == ANY_SYSCALL)
+    return 1;
+
+  get_syscall_trapinfo (event_child, &sysno, &sysret);
+  for (i = 0;
+       VEC_iterate (int, proc->syscalls_to_catch, i, iter);
+       i++)
+    if (iter == sysno)
+      return 1;
+
+  return 0;
+}
+
 /* Wait for process, returns status.  */
 
 static ptid_t
@@ -3307,6 +3414,22 @@ linux_wait_1 (ptid_t ptid,
 
   /* Check whether GDB would be interested in this event.  */
 
+  /* Check if GDB is interested in this syscall.  */
+  if (WIFSTOPPED (w)
+      && WSTOPSIG (w) == SYSCALL_SIGTRAP
+      && !gdb_catch_this_syscall_p (event_child))
+    {
+      if (debug_threads)
+	{
+	  debug_printf ("Ignored syscall for LWP %ld.\n",
+			lwpid_of (current_thread));
+	}
+
+      linux_resume_one_lwp (event_child, event_child->stepping,
+			    0, NULL);
+      return ignore_event (ourstatus);
+    }
+
   /* If GDB is not interested in this signal, don't stop other
      threads, and don't report it to GDB.  Just resume the inferior
      right away.  We do this for threading-related signals as well as
@@ -3559,8 +3682,16 @@ linux_wait_1 (ptid_t ptid,
 	}
     }
 
-  if (current_thread->last_resume_kind == resume_stop
-      && WSTOPSIG (w) == SIGSTOP)
+  if (WSTOPSIG (w) == SYSCALL_SIGTRAP)
+    {
+      int sysret;
+
+      get_syscall_trapinfo (event_child,
+			    &ourstatus->value.syscall_number, &sysret);
+      ourstatus->kind = event_child->syscall_state;
+    }
+  else if (current_thread->last_resume_kind == resume_stop
+	   && WSTOPSIG (w) == SIGSTOP)
     {
       /* A thread that has been requested to stop by GDB with vCont;t,
 	 and it stopped cleanly, so report as SIG0.  The use of
@@ -4017,6 +4148,7 @@ linux_resume_one_lwp_throw (struct lwp_info *lwp,
   struct thread_info *thread = get_lwp_thread (lwp);
   struct thread_info *saved_thread;
   int fast_tp_collecting;
+  int ptrace_request;
   struct process_info *proc = get_thread_process (thread);
 
   /* Note that target description may not be initialised
@@ -4204,7 +4336,14 @@ linux_resume_one_lwp_throw (struct lwp_info *lwp,
   regcache_invalidate_thread (thread);
   errno = 0;
   lwp->stepping = step;
-  ptrace (step ? PTRACE_SINGLESTEP : PTRACE_CONT, lwpid_of (thread),
+  if (step)
+    ptrace_request = PTRACE_SINGLESTEP;
+  else if (gdb_catching_syscalls_p (lwp))
+    ptrace_request = PTRACE_SYSCALL;
+  else
+    ptrace_request = PTRACE_CONT;
+  ptrace (ptrace_request,
+	  lwpid_of (thread),
 	  (PTRACE_TYPE_ARG3) 0,
 	  /* Coerce to a uintptr_t first to avoid potential gcc warning
 	     of coercing an 8 byte integer to a 4 byte pointer.  */
@@ -6286,6 +6425,13 @@ linux_process_qsupported (char **features, int count)
 }
 
 static int
+linux_supports_catch_syscall (void)
+{
+  return (the_low_target.get_syscall_trapinfo != NULL
+	  && linux_supports_tracesysgood ());
+}
+
+static int
 linux_supports_tracepoints (void)
 {
   if (*the_low_target.supports_tracepoints == NULL)
@@ -7209,7 +7355,8 @@ static struct target_ops linux_target_ops = {
   linux_sw_breakpoint_from_kind,
   linux_proc_tid_get_name,
   linux_breakpoint_kind_from_current_state,
-  linux_supports_software_single_step
+  linux_supports_software_single_step,
+  linux_supports_catch_syscall,
 };
 
 #ifdef HAVE_LINUX_REGSETS
diff --git a/gdb/gdbserver/linux-low.h b/gdb/gdbserver/linux-low.h
index e80c67f..751eea1 100644
--- a/gdb/gdbserver/linux-low.h
+++ b/gdb/gdbserver/linux-low.h
@@ -240,6 +240,12 @@ struct linux_target_ops
 
   /* See target.h.  */
   int (*supports_hardware_single_step) (void);
+
+  /* Fill *SYSNO with the syscall nr trapped.  Fill *SYSRET with the
+     return code.  Only to be called when inferior is stopped
+     due to SYSCALL_SIGTRAP.  */
+  void (*get_syscall_trapinfo) (struct regcache *regcache,
+				int *sysno, int *sysret);
 };
 
 extern struct linux_target_ops the_low_target;
@@ -278,6 +284,13 @@ struct lwp_info
      event already received in a wait()).  */
   int stopped;
 
+  /* Signal whether we are in a SYSCALL_ENTRY or
+     in a SYSCALL_RETURN event.
+     Values:
+     - TARGET_WAITKIND_SYSCALL_ENTRY
+     - TARGET_WAITKIND_SYSCALL_RETURN */
+  enum target_waitkind syscall_state;
+
   /* When stopped is set, the last wait status recorded for this lwp.  */
   int last_status;
 
diff --git a/gdb/gdbserver/linux-x86-low.c b/gdb/gdbserver/linux-x86-low.c
index 0432a86..4a01750 100644
--- a/gdb/gdbserver/linux-x86-low.c
+++ b/gdb/gdbserver/linux-x86-low.c
@@ -1438,6 +1438,31 @@ x86_arch_setup (void)
   current_process ()->tdesc = x86_linux_read_description ();
 }
 
+/* Fill *SYSNO and *SYSRET with the syscall nr trapped and the syscall return
+   code.  This should only be called if LWP got a SYSCALL_SIGTRAP.  */
+
+static void
+x86_get_syscall_trapinfo (struct regcache *regcache, int *sysno, int *sysret)
+{
+  int use_64bit = register_size (regcache->tdesc, 0) == 8;
+
+  if (use_64bit)
+    {
+      long l_sysno;
+      long l_sysret;
+
+      collect_register_by_name (regcache, "orig_rax", &l_sysno);
+      collect_register_by_name (regcache, "rax", &l_sysret);
+      *sysno = (int) l_sysno;
+      *sysret = (int) l_sysret;
+    }
+  else
+    {
+      collect_register_by_name (regcache, "orig_eax", sysno);
+      collect_register_by_name (regcache, "eax", sysret);
+    }
+}
+
 static int
 x86_supports_tracepoints (void)
 {
@@ -3315,6 +3340,7 @@ struct linux_target_ops the_low_target =
   x86_supports_range_stepping,
   NULL, /* breakpoint_kind_from_current_state */
   x86_supports_hardware_single_step,
+  x86_get_syscall_trapinfo,
 };
 
 void
diff --git a/gdb/gdbserver/remote-utils.c b/gdb/gdbserver/remote-utils.c
index 40bd373..15cdbe1 100644
--- a/gdb/gdbserver/remote-utils.c
+++ b/gdb/gdbserver/remote-utils.c
@@ -1132,6 +1132,8 @@ prepare_resume_reply (char *buf, ptid_t ptid,
     case TARGET_WAITKIND_VFORK_DONE:
     case TARGET_WAITKIND_EXECD:
     case TARGET_WAITKIND_THREAD_CREATED:
+    case TARGET_WAITKIND_SYSCALL_ENTRY:
+    case TARGET_WAITKIND_SYSCALL_RETURN:
       {
 	struct thread_info *saved_thread;
 	const char **regp;
@@ -1181,6 +1183,16 @@ prepare_resume_reply (char *buf, ptid_t ptid,
 
 	    sprintf (buf, "T%02xcreate:;", signal);
 	  }
+	else if (status->kind == TARGET_WAITKIND_SYSCALL_ENTRY
+		 || status->kind == TARGET_WAITKIND_SYSCALL_RETURN)
+	  {
+	    enum gdb_signal signal = GDB_SIGNAL_TRAP;
+	    const char *event = (status->kind == TARGET_WAITKIND_SYSCALL_ENTRY
+				 ? "syscall_entry" : "syscall_return");
+
+	    sprintf (buf, "T%02x%s:%x;", signal, event,
+		     status->value.syscall_number);
+	  }
 	else
 	  sprintf (buf, "T%02x", status->value.sig);
 
diff --git a/gdb/gdbserver/server.c b/gdb/gdbserver/server.c
index 440c076..301dea9 100644
--- a/gdb/gdbserver/server.c
+++ b/gdb/gdbserver/server.c
@@ -624,6 +624,54 @@ handle_general_set (char *own_buf)
       return;
     }
 
+  if (startswith (own_buf, "QCatchSyscalls:"))
+    {
+      const char *p = own_buf + sizeof ("QCatchSyscalls:") - 1;
+      int enabled = -1;
+      CORE_ADDR sysno;
+      struct process_info *process;
+
+      if (!target_running () || !target_supports_catch_syscall ())
+	{
+	  write_enn (own_buf);
+	  return;
+	}
+
+      if (strcmp (p, "0") == 0)
+	enabled = 0;
+      else if (p[0] == '1' && (p[1] == ';' || p[1] == '\0'))
+	enabled = 1;
+      else
+	{
+	  fprintf (stderr, "Unknown catch-syscalls mode requested: %s\n",
+		   own_buf);
+	  write_enn (own_buf);
+	  return;
+	}
+
+      process = current_process ();
+      VEC_truncate (int, process->syscalls_to_catch, 0);
+
+      if (enabled)
+	{
+	  p += 1;
+	  if (*p == ';')
+	    {
+	      p += 1;
+	      while (*p != '\0')
+		{
+		  p = decode_address_to_semicolon (&sysno, p);
+		  VEC_safe_push (int, process->syscalls_to_catch, (int) sysno);
+		}
+	    }
+	  else
+	    VEC_safe_push (int, process->syscalls_to_catch, ANY_SYSCALL);
+	}
+
+      write_ok (own_buf);
+      return;
+    }
+
   if (strcmp (own_buf, "QStartNoAckMode") == 0)
     {
       if (remote_debug)
@@ -2200,6 +2248,9 @@ handle_query (char *own_buf, int packet_len, int *new_packet_len_p)
 	       "PacketSize=%x;QPassSignals+;QProgramSignals+",
 	       PBUFSIZ - 1);
 
+      if (target_supports_catch_syscall ())
+	strcat (own_buf, ";QCatchSyscalls+");
+
       if (the_target->qxfer_libraries_svr4 != NULL)
 	strcat (own_buf, ";qXfer:libraries-svr4:read+"
 		";augmented-libraries-svr4-read+");
diff --git a/gdb/gdbserver/server.h b/gdb/gdbserver/server.h
index 58cf342..3d78fb3 100644
--- a/gdb/gdbserver/server.h
+++ b/gdb/gdbserver/server.h
@@ -134,4 +134,10 @@ extern void discard_queued_stop_replies (ptid_t ptid);
    as large as the largest register set supported by gdbserver.  */
 #define PBUFSIZ 16384
 
+/* Definition for an unknown syscall, used basically in error-cases.  */
+#define UNKNOWN_SYSCALL (-1)
+
+/* Definition for any syscall, used for unfiltered syscall reporting.  */
+#define ANY_SYSCALL (-2)
+
 #endif /* SERVER_H */
diff --git a/gdb/gdbserver/target.h b/gdb/gdbserver/target.h
index cbdb8d9..5af2051 100644
--- a/gdb/gdbserver/target.h
+++ b/gdb/gdbserver/target.h
@@ -467,6 +467,10 @@ struct target_ops
 
   /* Returns true if the target can software single step.  */
   int (*supports_software_single_step) (void);
+
+  /* Return 1 if the target supports catch syscall, 0 (or leave the
+     callback NULL) otherwise.  */
+  int (*supports_catch_syscall) (void);
 };
 
 extern struct target_ops *the_target;
@@ -542,6 +546,10 @@ int kill_inferior (int);
 	the_target->process_qsupported (features, count); \
     } while (0)
 
+#define target_supports_catch_syscall()              	\
+  (the_target->supports_catch_syscall ?			\
+   (*the_target->supports_catch_syscall) () : 0)
+
 #define target_supports_tracepoints()			\
   (the_target->supports_tracepoints			\
    ? (*the_target->supports_tracepoints) () : 0)