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.

2 files changed, 69 insertions, 0 deletions

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}).