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.

19 files changed, 566 insertions, 8 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 74f91d2..4bacf03 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,17 @@
+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.
+
 2016-01-12  Yao Qi  <yao.qi@linaro.org>
 
 	* nat/linux-ptrace.c (linux_child_function): Cast child_stack
diff --git a/gdb/NEWS b/gdb/NEWS
index e3dd399..85642fb 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -120,6 +120,21 @@ N stop reply
   threads are stopped).  The remote stub reports support for this stop
   reply to GDB's qSupported query.
 
+QCatchSyscalls:1 [;SYSNO]...
+QCatchSyscalls:0
+  Enable ("QCatchSyscalls:1") or disable ("QCatchSyscalls:0")
+  catching syscalls from the inferior process.
+
+syscall_entry stop reason
+  Indicates that a syscall was just called.
+
+syscall_return stop reason
+  Indicates that a syscall just returned.
+
+QCatchSyscalls:1 in qSupported
+  The qSupported packet may now include QCatchSyscalls:1 in the reply
+  to indicate support for catching syscalls.
+
 * Extended-remote exec events
 
   ** GDB now has support for exec events on extended-remote Linux targets.
@@ -142,6 +157,15 @@ show remote exec-event-feature-packet
      this enables follow-fork-mode, detach-on-fork, follow-exec-mode, and
      fork and exec catchpoints.
 
+* Remote syscall events
+
+  ** GDB now has support for catch syscall on remote Linux targets,
+     currently enabled on x86/x86_64 architectures.
+
+set remote catch-syscall-packet
+show remote catch-syscall-packet
+  Set/show the use of the remote catch syscall feature.
+
 * MI changes
 
   ** The -var-set-format command now accepts the zero-hexadecimal
diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog
index 3255fc3..b4ea0ee 100644
--- a/gdb/doc/ChangeLog
+++ b/gdb/doc/ChangeLog
@@ -1,3 +1,11 @@
+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.
+
 2016-01-12  Pedro Alves  <palves@redhat.com>
 
 	Remove use of the registered trademark symbol throughout.
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 89826a4..35065e0 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -20261,6 +20261,10 @@ are:
 @tab @code{qSupported}
 @tab Remote communications parameters
 
+@item @code{catch-syscalls}
+@tab @code{QCatchSyscalls}
+@tab @code{catch syscall}
+
 @item @code{pass-signals}
 @tab @code{QPassSignals}
 @tab @code{handle @var{signal}}
@@ -35580,6 +35584,11 @@ The currently defined stop reasons are:
 The packet indicates a watchpoint hit, and @var{r} is the data address, in
 hex.
 
+@item syscall_entry
+@itemx syscall_return
+The packet indicates a syscall entry or return, and @var{r} is the
+syscall number, in hex.
+
 @cindex shared library events, remote reply
 @item library
 The packet indicates that the loaded libraries have changed.
@@ -36072,6 +36081,49 @@ by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
 Use of this packet is controlled by the @code{set non-stop} command; 
 @pxref{Non-Stop Mode}.
 
+@item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
+@itemx QCatchSyscalls:0
+@cindex catch syscalls from inferior, remote request
+@cindex @samp{QCatchSyscalls} packet
+@anchor{QCatchSyscalls}
+Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
+catching syscalls from the inferior process.
+
+For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
+in hex) should be reported to @value{GDBN}.  If no syscall @var{sysno}
+is listed, every system call should be reported.
+
+Note that if a syscall not in the list is reported, @value{GDBN} will
+still filter the event according to its own list from all corresponding
+@code{catch syscall} commands.  However, it is more efficient to only
+report the requested syscalls.
+
+Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
+@samp{QCatchSyscalls:1} list is completely replaced by the new list.
+
+If the inferior process execs, the state of @samp{QCatchSyscalls} is
+kept for the new process too.  On targets where exec may affect syscall
+numbers, for example with exec between 32 and 64-bit processes, the
+client should send a new packet with the new syscall list.
+
+Reply:
+@table @samp
+@item OK
+The request succeeded.
+
+@item E @var{nn}
+An error occurred.  @var{nn} are hex digits.
+
+@item @w{}
+An empty reply indicates that @samp{QCatchSyscalls} is not supported by
+the stub.
+@end table
+
+Use of this packet is controlled by the @code{set remote catch-syscalls}
+command (@pxref{Remote Configuration, set remote catch-syscalls}).
+This packet is not probed by default; the remote stub must request it,
+by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
+
 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
 @cindex pass signals to inferior, remote request
 @cindex @samp{QPassSignals} packet
@@ -36523,6 +36575,11 @@ These are the currently defined stub features and their properties:
 @tab @samp{-}
 @tab Yes
 
+@item @samp{QCatchSyscalls}
+@tab No
+@tab @samp{-}
+@tab Yes
+
 @item @samp{QPassSignals}
 @tab No
 @tab @samp{-}
@@ -36726,6 +36783,10 @@ packet (@pxref{qXfer fdpic loadmap read}).
 The remote stub understands the @samp{QNonStop} packet
 (@pxref{QNonStop}).
 
+@item QCatchSyscalls
+The remote stub understands the @samp{QCatchSyscalls} packet
+(@pxref{QCatchSyscalls}).
+
 @item QPassSignals
 The remote stub understands the @samp{QPassSignals} packet
 (@pxref{QPassSignals}).
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)
diff --git a/gdb/linux-nat.h b/gdb/linux-nat.h
index 7bdeb31..73888e5 100644
--- a/gdb/linux-nat.h
+++ b/gdb/linux-nat.h
@@ -88,7 +88,7 @@ struct lwp_info
      or to a local variable in lin_lwp_wait.  */
   struct target_waitstatus waitstatus;
 
-  /* Signal wether we are in a SYSCALL_ENTRY or
+  /* Signal whether we are in a SYSCALL_ENTRY or
      in a SYSCALL_RETURN event.
      Values:
      - TARGET_WAITKIND_SYSCALL_ENTRY
diff --git a/gdb/remote.c b/gdb/remote.c
index 528d863..e825d27 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -1392,6 +1392,7 @@ enum {
   PACKET_qSupported,
   PACKET_qTStatus,
   PACKET_QPassSignals,
+  PACKET_QCatchSyscalls,
   PACKET_QProgramSignals,
   PACKET_qCRC,
   PACKET_qSearch_memory,
@@ -1987,6 +1988,93 @@ remote_pass_signals (struct target_ops *self,
     }
 }
 
+/* If 'QCatchSyscalls' is supported, tell the remote stub
+   to report syscalls to GDB.  */
+
+static int
+remote_set_syscall_catchpoint (struct target_ops *self,
+			       int pid, int needed, int any_count,
+			       int table_size, int *table)
+{
+  char *catch_packet;
+  enum packet_result result;
+  int n_sysno = 0;
+
+  if (packet_support (PACKET_QCatchSyscalls) == PACKET_DISABLE)
+    {
+      /* Not supported.  */
+      return 1;
+    }
+
+  if (needed && !any_count)
+    {
+      int i;
+
+      /* Count how many syscalls are to be caught (table[sysno] != 0).  */
+      for (i = 0; i < table_size; i++)
+	{
+	  if (table[i] != 0)
+	    n_sysno++;
+	}
+    }
+
+  if (remote_debug)
+    {
+      fprintf_unfiltered (gdb_stdlog,
+			  "remote_set_syscall_catchpoint "
+			  "pid %d needed %d any_count %d n_sysno %d\n",
+			  pid, needed, any_count, n_sysno);
+    }
+
+  if (needed)
+    {
+      /* Prepare a packet with the sysno list, assuming max 8+1
+	 characters for a sysno.  If the resulting packet size is too
+	 big, fallback on the non-selective packet.  */
+      const int maxpktsz = strlen ("QCatchSyscalls:1") + n_sysno * 9 + 1;
+
+      catch_packet = xmalloc (maxpktsz);
+      strcpy (catch_packet, "QCatchSyscalls:1");
+      if (!any_count)
+	{
+	  int i;
+	  char *p;
+
+	  p = catch_packet;
+	  p += strlen (p);
+
+	  /* Add in catch_packet each syscall to be caught (table[i] != 0).  */
+	  for (i = 0; i < table_size; i++)
+	    {
+	      if (table[i] != 0)
+		p += xsnprintf (p, catch_packet + maxpktsz - p, ";%x", i);
+	    }
+	}
+      if (strlen (catch_packet) > get_remote_packet_size ())
+	{
+	  /* catch_packet too big.  Fallback to less efficient
+	     non selective mode, with GDB doing the filtering.  */
+	  catch_packet[sizeof ("QCatchSyscalls:1") - 1] = 0;
+	}
+    }
+  else
+    catch_packet = xstrdup ("QCatchSyscalls:0");
+
+  {
+    struct cleanup *old_chain = make_cleanup (xfree, catch_packet);
+    struct remote_state *rs = get_remote_state ();
+
+    putpkt (catch_packet);
+    getpkt (&rs->buf, &rs->buf_size, 0);
+    result = packet_ok (rs->buf, &remote_protocol_packets[PACKET_QCatchSyscalls]);
+    do_cleanups (old_chain);
+    if (result == PACKET_OK)
+      return 0;
+    else
+      return -1;
+  }
+}
+
 /* If 'QProgramSignals' is supported, tell the remote stub what
    signals it should pass through to the inferior when detaching.  */
 
@@ -4467,6 +4555,8 @@ static const struct protocol_feature remote_protocol_features[] = {
     PACKET_qXfer_traceframe_info },
   { "QPassSignals", PACKET_DISABLE, remote_supported_packet,
     PACKET_QPassSignals },
+  { "QCatchSyscalls", PACKET_DISABLE, remote_supported_packet,
+    PACKET_QCatchSyscalls },
   { "QProgramSignals", PACKET_DISABLE, remote_supported_packet,
     PACKET_QProgramSignals },
   { "QStartNoAckMode", PACKET_DISABLE, remote_supported_packet,
@@ -6371,6 +6461,22 @@ Packet: '%s'\n"),
 
 	  if (strprefix (p, p1, "thread"))
 	    event->ptid = read_ptid (++p1, &p);
+	  else if (strprefix (p, p1, "syscall_entry"))
+	    {
+	      ULONGEST sysno;
+
+	      event->ws.kind = TARGET_WAITKIND_SYSCALL_ENTRY;
+	      p = unpack_varlen_hex (++p1, &sysno);
+	      event->ws.value.syscall_number = (int) sysno;
+	    }
+	  else if (strprefix (p, p1, "syscall_return"))
+	    {
+	      ULONGEST sysno;
+
+	      event->ws.kind = TARGET_WAITKIND_SYSCALL_RETURN;
+	      p = unpack_varlen_hex (++p1, &sysno);
+	      event->ws.value.syscall_number = (int) sysno;
+	    }
 	  else if (strprefix (p, p1, "watch")
 		   || strprefix (p, p1, "rwatch")
 		   || strprefix (p, p1, "awatch"))
@@ -12976,6 +13082,7 @@ Specify the serial device it is connected to\n\
   remote_ops.to_load = remote_load;
   remote_ops.to_mourn_inferior = remote_mourn;
   remote_ops.to_pass_signals = remote_pass_signals;
+  remote_ops.to_set_syscall_catchpoint = remote_set_syscall_catchpoint;
   remote_ops.to_program_signals = remote_program_signals;
   remote_ops.to_thread_alive = remote_thread_alive;
   remote_ops.to_thread_name = remote_thread_name;
@@ -13542,6 +13649,9 @@ Show the maximum size of the address (in bits) in a memory packet."), NULL,
   add_packet_config_cmd (&remote_protocol_packets[PACKET_QPassSignals],
 			 "QPassSignals", "pass-signals", 0);
 
+  add_packet_config_cmd (&remote_protocol_packets[PACKET_QCatchSyscalls],
+			 "QCatchSyscalls", "catch-syscalls", 0);
+
   add_packet_config_cmd (&remote_protocol_packets[PACKET_QProgramSignals],
 			 "QProgramSignals", "program-signals", 0);
 
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index da9c70a..0d07499 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,12 @@
+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.
+
 2016-01-12  Pedro Alves  <palves@redhat.com>
 
 	* gdb.base/random-signal.exp (do_test): New procedure, with body
diff --git a/gdb/testsuite/gdb.base/catch-syscall.c b/gdb/testsuite/gdb.base/catch-syscall.c
index e65d4a4..98222fa 100644
--- a/gdb/testsuite/gdb.base/catch-syscall.c
+++ b/gdb/testsuite/gdb.base/catch-syscall.c
@@ -31,13 +31,20 @@ int write_syscall = SYS_write;
 int unknown_syscall = 123456789;
 int exit_group_syscall = SYS_exit_group;
 
+/* Set by the test when it wants execve.  */
+int do_execve = 0;
+
 int
-main (void)
+main (int argc, char *const argv[])
 {
 	int fd[2];
 	char buf1[2] = "a";
 	char buf2[2];
 
+	/* Test a simple self-exec, but only on request.  */
+	if (do_execve)
+	  execv (*argv, argv);
+
 	/* A close() with a wrong argument.  We are only
 	   interested in the syscall.  */
 	close (-1);
diff --git a/gdb/testsuite/gdb.base/catch-syscall.exp b/gdb/testsuite/gdb.base/catch-syscall.exp
index 26fb6a5..5679000 100644
--- a/gdb/testsuite/gdb.base/catch-syscall.exp
+++ b/gdb/testsuite/gdb.base/catch-syscall.exp
@@ -19,7 +19,7 @@
 # It was written by Sergio Durigan Junior <sergiodj@linux.vnet.ibm.com>
 # on September/2008.
 
-if { [is_remote target] || ![isnative] } then {
+if { ![isnative] } then {
     continue
 }
 
@@ -322,6 +322,28 @@ proc test_catch_syscall_mid_vfork {} {
     }
 }
 
+proc test_catch_syscall_execve {} {
+    global gdb_prompt decimal
+
+    with_test_prefix "execve" {
+
+	# Tell the test program we want an execve.
+	gdb_test_no_output "set do_execve = 1"
+
+	# Check for entry/return across the execve, making sure that the
+	# syscall_state isn't lost when turning into a new process.
+	insert_catch_syscall_with_arg "execve"
+	check_continue "execve"
+
+	# Continue to main so extended-remote can read files as needed.
+	# (Otherwise that "Reading" output confuses gdb_continue_to_end.)
+	gdb_continue "main"
+
+	# Now can we finish?
+	check_for_program_end
+    }
+}
+
 proc test_catch_syscall_fail_nodatadir {} {
     with_test_prefix "fail no datadir" {
 	# Sanitizing.
@@ -392,6 +414,9 @@ proc do_syscall_tests {} {
     # Testing the 'catch syscall' command starting mid-vfork.
     if [runto_main] then { test_catch_syscall_mid_vfork }
 
+    # Testing that 'catch syscall' entry/return tracks across execve.
+    if [runto_main] then { test_catch_syscall_execve }
+
     # Testing if the 'catch syscall' command works when switching to
     # different architectures on-the-fly (PR gdb/10737).
     if [runto_main] then { test_catch_syscall_multi_arch }