RFA [PATCH v4] Implement 'catch syscall' for gdbserver (was Re: RFA [PATCH v3] Implement 'catch syscall' for gdbserver)

Philippe Waroquiers
2013-09-29T15:04:18Z

On Fri, 2013-09-27 at 17:55 -0300, Sergio Durigan Junior wrote:
> Still have some formatting issues, as pointed by Tom on IRC.
Thanks, handled all comments (formatting and others),
just a question below about the -1 syscall nr.

> > + if (the_low_target.get_syscall_trapinfo == NULL)
> > + {
> > + *sysno = 0;
> > + *sysret = 0;
> > + return;
> > + }
>
> Just a reminder that you were going to check if -1 is a better value to
> represent this case. And if it is, then it should be documented, of course.
Tested with -1 (on x86_64), and it works.
I would have liked to re-use UNKNOWN_SYSCALL defined in gdbarch.h, but
this is not included in gdbserver, and it sounds strange to me to
include it to just get this constant.
So, for the moment, I have just used -1 directly.
Is there a correct place to define this constant ?

Also, not sure what is meant by 'should be documented'.
Do you mean add a sentence in the protocol documentation such as:
"In case the remote stub cannot determine the syscall number,
the remote stub must send -1 as syscall nr (encoded in hex,
e.g. ffffffff)."
(do we really want that to be part of the protocol spec ?
This is really a very special case caused by a user "strange"
manipulation of forcing to use the packet QCatchSyscalls).

In the meantime, find below the version 4 of the patch implementing
catch syscall for gdbserver.
The changes compared to v3 are:
* handles the additional review comments given by Sergio Durigan Junior
In particular, in case the syscall nr cannot be fetched from the low
linux target, returns -1 syscall nr.
* removes the useless "syscall" field in the stop_reply (i.e. similar
to the removal of fields solibs_changes/replay_event done by Pedro Alves).
* formatting changes (I hope I got the formatting all correct this time).

Tested on x86_64, using:
for t in "" "--target_board native-extended-gdbserver" "--target_board native-gdbserver"
do
make check RUNTESTFLAGS="$t"
....
done
(still without libexpat, waiting for Pedro's patch to be committed).

Thanks ...

Philippe

ChangeLog
2013-xx-yy Philippe Waroquiers <philippe.waroquiers@skynet.be>

* NEWS: Document new QcatchSyscalls packet and its use
in x86/amd64 linux gdbserver and Valgrind gdbserver.
* remote.c (PACKET_QCatchSyscalls): New.
(remote_protocol_features): Add QcatchSyscalls.
(remote_set_syscall_catchpoint): New function.
(remote_parse_stop_reply): New stop reasons syscall_entry
and syscall_return.
(init_remote_ops): Registers remote_set_syscall_catchpoint
and the config commands for PACKET_QCatchSyscalls.
* common/linux-ptrace.c (linux_check_ptrace_features):
Detect PTRACE_O_TRACESYSGOOD for gdbserver.
(ptrace_supports_feature): Initializes ptrace features if needed.

doc/ChangeLog
2013-xx-yy Philippe Waroquiers <philippe.waroquiers@skynet.be>

* gdb.texinfo (General Query Packets): Document new QCatchSyscalls
packet.
(Stop Reply Packets): Document new stop reasons syscall_entry and
syscall_return.
(Async Records): Fixed syscall-return item name.

gdbserver/ChangeLog
2013-xx-yy Philippe Waroquiers <philippe.waroquiers@skynet.be>

* target.h (struct target_ops): Add supports_catch_syscall operation.
* linux-low.h (struct linux_target_ops): Add get_syscall_trapinfo
operation.
* linux-low.c (linux_wait_1): Enable, detect and handle
SYSCALL_SIGTRAP.
(gdb_catch_this_syscall_p): New function.
(get_syscall_trapinfo): New function.
(linux_supports_catch_syscall): New function.
(struct target_ops linux_target_ops): Set linux_supports_catch_syscall.
* linux-x86-low.c (x86_get_syscall_trapinfo): New function.
(struct linux_target_ops the_low_target): Set x86_get_syscall_trapinfo.
* remote-utils.c (prepare_resume_reply): Handle status kinds
TARGET_WAITKIND_SYSCALL_ENTRY and TARGET_WAITKIND_SYSCALL_RETURN.
* server.h: Declare catching_syscalls_p, syscalls_to_catch_size and
syscalls_to_catch.
* server.c: Define catching_syscalls_p, syscalls_to_catch_size and
syscalls_to_catch.
(handle_general_set): Handle QCatchSyscalls packet.
(handle_query): Reports if low target supports QCatchSyscalls.
* win32-low.c (struct target_ops win32_target_op): Sets NULL
for supports_catch_syscall.

testsuite/ChangeLog
2013-xx-yy Philippe Waroquiers <philippe.waroquiers@skynet.be>

* gdb.base/catch-syscall.exp: Enables test for x86 and amd64
gdbserver.

Index: NEWS
===================================================================
RCS file: /cvs/src/src/gdb/NEWS,v
retrieving revision 1.616
diff -u -p -r1.616 NEWS
--- NEWS 25 Sep 2013 23:17:11 -0000 1.616
+++ NEWS 29 Sep 2013 14:20:27 -0000
@@ -157,11 +157,20 @@ qXfer:libraries-svr4:read's annex
necessary for library list updating, resulting in significant
speedup.

+QCatchSyscalls:1 [;SYSNO]...
+QCatchSyscalls:0
+ Enable ("QCatchSyscalls:1") or disable ("QCatchSyscalls:0")
+ catching syscalls from the inferior process.
+
+
* New features in the GDB remote stub, GDBserver

** GDBserver now supports target-assisted range stepping. Currently
enabled on x86/x86_64 GNU/Linux targets.

+ ** GDBserver now supports catch syscall. Currently enabled
+ on x86/x86_64 GNU/Linux targets, and in the Valgrind gdbserver.
+
** GDBserver now adds element 'tvar' in the XML in the reply to
'qXfer:traceframe-info:read'. It has the id of the collected
trace state variables.
Index: remote.c
===================================================================
RCS file: /cvs/src/src/gdb/remote.c,v
retrieving revision 1.579
diff -u -p -r1.579 remote.c
--- remote.c 27 Sep 2013 15:29:06 -0000 1.579
+++ remote.c 29 Sep 2013 14:20:29 -0000
@@ -1340,6 +1340,7 @@ enum {
PACKET_qSupported,
PACKET_qTStatus,
PACKET_QPassSignals,
+ PACKET_QCatchSyscalls,
PACKET_QProgramSignals,
PACKET_qSearch_memory,
PACKET_vAttach,
@@ -1728,6 +1729,98 @@ remote_pass_signals (int numsigs, unsign
}
}

+/* If 'QCatchSyscalls' is supported, tell the remote stub
+ to report syscalls to GDB. */
+
+static int
+remote_set_syscall_catchpoint (int pid, int needed, int any_count,
+ int table_size, int *table)
+{
+ char *catch_packet, *p;
+ enum packet_result result;
+ int n_sysno = 0;
+
+ if (remote_protocol_packets[PACKET_QCatchSyscalls].support == 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])
+ 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 char *q1 = "QCatchSyscalls:1";
+ int i;
+ const int maxpktsz = strlen (q1) + n_sysno * 9 + 1;
+
+ catch_packet = xmalloc (maxpktsz);
+ strcpy (catch_packet, q1);
+ if (!any_count)
+ {
+ 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])
+ {
+ xsnprintf (p, catch_packet + maxpktsz - p,
+ ";%x", i);
+ p += strlen (p);
+ }
+ }
+ }
+ 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[strlen (q1)] = 0;
+ }
+ }
+ else
+ {
+ catch_packet = xmalloc (strlen ("QCatchSyscalls:0") + 1);
+ strcpy (catch_packet, "QCatchSyscalls:0");
+ }
+
+ {
+ struct remote_state *rs = get_remote_state ();
+ char *buf = rs->buf;
+
+ putpkt (catch_packet);
+ getpkt (&rs->buf, &rs->buf_size, 0);
+ result = packet_ok (buf,
+ &remote_protocol_packets[PACKET_QCatchSyscalls]);
+ xfree (catch_packet);
+ 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. */

@@ -4016,6 +4109,8 @@ static const struct protocol_feature rem
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,
@@ -5591,6 +5686,22 @@ Packet: '%s'\n"),
p, buf);
if (strncmp (p, "thread", p1 - p) == 0)
event->ptid = read_ptid (++p1, &p);
+ else if (strncmp (p, "syscall_entry", p1 - p) == 0)
+ {
+ ULONGEST sysno;
+
+ event->ws.kind = TARGET_WAITKIND_SYSCALL_ENTRY;
+ p = unpack_varlen_hex (++p1, &sysno);
+ event->ws.value.syscall_number = (int) sysno;
+ }
+ else if (strncmp (p, "syscall_return", p1 - p) == 0)
+ {
+ ULONGEST sysno;
+
+ event->ws.kind = TARGET_WAITKIND_SYSCALL_RETURN;
+ p = unpack_varlen_hex (++p1, &sysno);
+ event->ws.value.syscall_number = (int) sysno;
+ }
else if ((strncmp (p, "watch", p1 - p) == 0)
|| (strncmp (p, "rwatch", p1 - p) == 0)
|| (strncmp (p, "awatch", p1 - p) == 0))
@@ -11445,6 +11556,7 @@ Specify the serial device it is connecte
remote_ops.to_load = generic_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_find_new_threads = remote_threads_info;
@@ -11939,6 +12051,9 @@ Show the maximum size of the address (in
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);

Index: common/linux-ptrace.c
===================================================================
RCS file: /cvs/src/src/gdb/common/linux-ptrace.c,v
retrieving revision 1.12
diff -u -p -r1.12 linux-ptrace.c
--- common/linux-ptrace.c 28 Aug 2013 14:09:31 -0000 1.12
+++ common/linux-ptrace.c 29 Sep 2013 14:20:29 -0000
@@ -361,16 +361,18 @@ linux_check_ptrace_features (void)
return;
}

-#ifdef GDBSERVER
- /* gdbserver does not support PTRACE_O_TRACESYSGOOD or
- PTRACE_O_TRACEVFORKDONE yet. */
-#else
- /* Check if the target supports PTRACE_O_TRACESYSGOOD. */
+ /* Check if the target supports PTRACE_O_TRACESYSGOOD.
+ We keep PTRACE_O_TRACEFORK option activated as a fork
+ event notification is expected after my_waitpid below. */
ret = ptrace (PTRACE_SETOPTIONS, child_pid, (PTRACE_TYPE_ARG3) 0,
- (PTRACE_TYPE_ARG4) PTRACE_O_TRACESYSGOOD);
+ (PTRACE_TYPE_ARG4) (PTRACE_O_TRACEFORK
+ | PTRACE_O_TRACESYSGOOD));
if (ret == 0)
current_ptrace_options |= PTRACE_O_TRACESYSGOOD;

+#ifdef GDBSERVER
+ /* gdbserver does not support PTRACE_O_TRACEVFORKDONE yet. */
+#else
/* Check if the target supports PTRACE_O_TRACEVFORKDONE. */
ret = ptrace (PTRACE_SETOPTIONS, child_pid, (PTRACE_TYPE_ARG3) 0,
(PTRACE_TYPE_ARG4) (PTRACE_O_TRACEFORK
@@ -474,6 +476,11 @@ linux_enable_event_reporting (pid_t pid)
static int
ptrace_supports_feature (int ptrace_options)
{
+ /* Check if we have initialized the ptrace features for this
+ target. If not, do it now. */
+ if (current_ptrace_options == -1)
+ linux_check_ptrace_features ();
+
gdb_assert (current_ptrace_options >= 0);

return ((current_ptrace_options & ptrace_options) == ptrace_options);
Index: doc/gdb.texinfo
===================================================================
RCS file: /cvs/src/src/gdb/doc/gdb.texinfo,v
retrieving revision 1.1113
diff -u -p -r1.1113 gdb.texinfo
--- doc/gdb.texinfo 25 Sep 2013 23:17:12 -0000 1.1113
+++ doc/gdb.texinfo 29 Sep 2013 14:20:34 -0000
@@ -18752,6 +18752,10 @@ 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}}
@@ -38153,6 +38157,11 @@ 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.
@@ -38523,6 +38532,44 @@ by supplying an appropriate @samp{qSuppo
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 member of the list is reported, @value{GDBN}
+will filter it if this syscall is not caught. It is however more efficient
+to only report the needed syscalls.
+
+Multiple @samp{QCatchSyscalls:1} packets do not
+combine; any earlier @samp{QCatchSyscalls:1} list is completely replaced by the
+new 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
@@ -38886,6 +38933,11 @@ These are the currently defined stub fea
@tab @samp{-}
@tab Yes

+@item @samp{QCatchSyscalls}
+@tab No
+@tab @samp{-}
+@tab Yes
+
@item @samp{QPassSignals}
@tab No
@tab @samp{-}
@@ -39046,6 +39098,10 @@ 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}).
Index: gdbserver/linux-low.c
===================================================================
RCS file: /cvs/src/src/gdb/gdbserver/linux-low.c,v
retrieving revision 1.248
diff -u -p -r1.248 linux-low.c
--- gdbserver/linux-low.c 5 Sep 2013 20:45:39 -0000 1.248
+++ gdbserver/linux-low.c 29 Sep 2013 14:20:35 -0000
@@ -74,6 +74,11 @@
#define W_STOPCODE(sig) ((sig) << 8 | 0x7f)
#endif

+/* Unlike other extended result codes, WSTOPSIG (status) on
+ PTRACE_O_TRACESYSGOOD syscall events doesn't return SIGTRAP, but
+ instead SIGTRAP with bit 7 set. */
+#define SYSCALL_SIGTRAP (SIGTRAP | 0x80)
+
/* This is the kernel's hard limit. Not to be confused with
SIGRTMIN. */
#ifndef __SIGRTMIN
@@ -481,6 +486,38 @@ get_pc (struct lwp_info *lwp)
return pc;
}

+/* This function should only be called if LWP got a SIGTRAP_SYSCALL.
+ 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_inferior;
+ struct regcache *regcache;
+
+ if (the_low_target.get_syscall_trapinfo == NULL)
+ {
+ /* If we cannot get the syscall trapinfo, report an unknown
+ system call using -1 values. */
+ *sysno = -1;
+ *sysret = -1;
+ return;
+ }
+
+ saved_inferior = current_inferior;
+ current_inferior = get_lwp_thread (lwp);
+
+ regcache = get_thread_regcache (current_inferior, 1);
+ (*the_low_target.get_syscall_trapinfo) (regcache, sysno, sysret);
+
+ if (debug_threads)
+ fprintf (stderr, "get_syscall_trapinfo sysno %d sysret %d\n",
+ *sysno, *sysret);
+
+ current_inferior = saved_inferior;
+}
+
/* This function should only be called if LWP got a SIGTRAP.
The SIGTRAP could mean several things.

@@ -2248,6 +2285,29 @@ linux_stabilize_threads (void)
}
}

+/* Returns 1 if GDB is interested in the event_child syscall.
+ Only to be called when stopped reason is SIGTRAP_SYSCALL. */
+
+static int
+gdb_catch_this_syscall_p (struct lwp_info *event_child)
+{
+ int i;
+ int sysno, sysret;
+
+ if (!catching_syscalls_p)
+ return 0;
+
+ if (syscalls_to_catch_size == 0)
+ return 1;
+
+ get_syscall_trapinfo (event_child, &sysno, &sysret);
+ for (i = 0; i < syscalls_to_catch_size; i++)
+ if (syscalls_to_catch[i] == sysno)
+ return 1;
+
+ return 0;
+}
+
/* Wait for process, returns status. */

static ptid_t
@@ -2529,6 +2589,19 @@ Check if we're already there.\n",

/* 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)
+ fprintf (stderr, "Ignored syscall for LWP %ld.\n",
+ lwpid_of (event_child));
+ linux_resume_one_lwp (event_child, event_child->stepping,
+ 0, NULL);
+ goto retry;
+ }
+
/* 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
@@ -2707,7 +2780,24 @@ Check if we're already there.\n",

ourstatus->kind = TARGET_WAITKIND_STOPPED;

- if (current_inferior->last_resume_kind == resume_stop
+ if (WSTOPSIG (w) == SYSCALL_SIGTRAP)
+ {
+ int sysret;
+
+ get_syscall_trapinfo (event_child,
+ &ourstatus->value.syscall_number, &sysret);
+ /* Differentiate entry from return using the return code
+ -ENOSYS. This is not ideal as a syscall return from a not
+ implemented syscall will be seen as an entry. However, this
+ resists well to enabling/disabling catch syscall at various
+ moment. A better way to differentiate entry/return in GDB
+ and GDBSERVER would be nice. */
+ if (sysret == -ENOSYS)
+ ourstatus->kind = TARGET_WAITKIND_SYSCALL_ENTRY;
+ else
+ ourstatus->kind = TARGET_WAITKIND_SYSCALL_RETURN;
+ }
+ else if (current_inferior->last_resume_kind == resume_stop
&& WSTOPSIG (w) == SIGSTOP)
{
/* A thread that has been requested to stop by GDB with vCont;t,
@@ -3098,6 +3188,7 @@ linux_resume_one_lwp (struct lwp_info *l
{
struct thread_info *saved_inferior;
int fast_tp_collecting;
+ int ptrace_request;

if (lwp->stopped == 0)
return;
@@ -3269,7 +3360,14 @@ lwp %ld wants to get out of fast tracepo
lwp->stopped = 0;
lwp->stopped_by_watchpoint = 0;
lwp->stepping = step;
- ptrace (step ? PTRACE_SINGLESTEP : PTRACE_CONT, lwpid_of (lwp),
+ if (step)
+ ptrace_request = PTRACE_SINGLESTEP;
+ else if (catching_syscalls_p)
+ ptrace_request = PTRACE_SYSCALL;
+ else
+ ptrace_request = PTRACE_CONT;
+ ptrace (ptrace_request,
+ lwpid_of (lwp),
(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. */
@@ -5108,6 +5206,13 @@ linux_process_qsupported (const char *qu
}

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)
@@ -5798,6 +5903,7 @@ static struct target_ops linux_target_op
linux_common_core_of_thread,
linux_read_loadmap,
linux_process_qsupported,
+ linux_supports_catch_syscall,
linux_supports_tracepoints,
linux_read_pc,
linux_write_pc,
Index: gdbserver/linux-low.h
===================================================================
RCS file: /cvs/src/src/gdb/gdbserver/linux-low.h,v
retrieving revision 1.65
diff -u -p -r1.65 linux-low.h
--- gdbserver/linux-low.h 22 Aug 2013 23:46:29 -0000 1.65
+++ gdbserver/linux-low.h 29 Sep 2013 14:20:35 -0000
@@ -187,6 +187,12 @@ struct linux_target_ops
/* Hook to support target specific qSupported. */
void (*process_qsupported) (const char *);

+ /* 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);
+
/* Returns true if the low target supports tracepoints. */
int (*supports_tracepoints) (void);

Index: gdbserver/linux-x86-low.c
===================================================================
RCS file: /cvs/src/src/gdb/gdbserver/linux-x86-low.c,v
retrieving revision 1.51
diff -u -p -r1.51 linux-x86-low.c
--- gdbserver/linux-x86-low.c 5 Sep 2013 20:40:58 -0000 1.51
+++ gdbserver/linux-x86-low.c 29 Sep 2013 14:20:35 -0000
@@ -1474,6 +1474,36 @@ 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 SIGTRAP_SYSCALL. */
+
+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
+ {
+ int l_sysno;
+ int l_sysret;
+
+ collect_register_by_name (regcache, "orig_eax", &l_sysno);
+ collect_register_by_name (regcache, "eax", &l_sysret);
+ *sysno = (int) l_sysno;
+ *sysret = (int) l_sysret;
+ }
+}
+
static int
x86_supports_tracepoints (void)
{
@@ -3323,6 +3353,7 @@ struct linux_target_ops the_low_target =
x86_linux_new_thread,
x86_linux_prepare_to_resume,
x86_linux_process_qsupported,
+ x86_get_syscall_trapinfo,
x86_supports_tracepoints,
x86_get_thread_area,
x86_install_fast_tracepoint_jump_pad,
Index: gdbserver/remote-utils.c
===================================================================
RCS file: /cvs/src/src/gdb/gdbserver/remote-utils.c,v
retrieving revision 1.99
diff -u -p -r1.99 remote-utils.c
--- gdbserver/remote-utils.c 5 Sep 2013 20:41:55 -0000 1.99
+++ gdbserver/remote-utils.c 29 Sep 2013 14:20:35 -0000
@@ -1321,12 +1321,17 @@ prepare_resume_reply (char *buf, ptid_t
switch (status->kind)
{
case TARGET_WAITKIND_STOPPED:
+ case TARGET_WAITKIND_SYSCALL_ENTRY:
+ case TARGET_WAITKIND_SYSCALL_RETURN:
{
struct thread_info *saved_inferior;
const char **regp;
struct regcache *regcache;

- sprintf (buf, "T%02x", status->value.sig);
+ if (status->kind == TARGET_WAITKIND_STOPPED)
+ sprintf (buf, "T%02x", status->value.sig);
+ else
+ sprintf (buf, "T%02x", SIGTRAP);
buf += strlen (buf);

saved_inferior = current_inferior;
@@ -1337,6 +1342,16 @@ prepare_resume_reply (char *buf, ptid_t

regcache = get_thread_regcache (current_inferior, 1);

+ if (status->kind == TARGET_WAITKIND_SYSCALL_ENTRY
+ || status->kind == TARGET_WAITKIND_SYSCALL_RETURN)
+ {
+ sprintf (buf, "%s:%x;",
+ status->kind == TARGET_WAITKIND_SYSCALL_ENTRY
+ ? "syscall_entry" : "syscall_return",
+ status->value.syscall_number);
+ buf += strlen (buf);
+ }
+
if (the_target->stopped_by_watchpoint != NULL
&& (*the_target->stopped_by_watchpoint) ())
{
Index: gdbserver/server.c
===================================================================
RCS file: /cvs/src/src/gdb/gdbserver/server.c,v
retrieving revision 1.201
diff -u -p -r1.201 server.c
--- gdbserver/server.c 18 Sep 2013 01:59:59 -0000 1.201
+++ gdbserver/server.c 29 Sep 2013 14:20:35 -0000
@@ -74,6 +74,9 @@ int debug_threads;
int debug_hw_points;

int pass_signals[GDB_SIGNAL_LAST];
+int catching_syscalls_p;
+int syscalls_to_catch_size;
+int *syscalls_to_catch;
int program_signals[GDB_SIGNAL_LAST];
int program_signals_p;

@@ -511,6 +514,46 @@ handle_general_set (char *own_buf)
return;
}

+ if (strncmp ("QCatchSyscalls:1", own_buf, strlen ("QCatchSyscalls:1")) == 0)
+ {
+ int i;
+ const char *p;
+ CORE_ADDR sysno;
+
+ catching_syscalls_p = 1;
+ if (syscalls_to_catch != NULL)
+ {
+ xfree (syscalls_to_catch);
+ syscalls_to_catch = NULL;
+ }
+ syscalls_to_catch_size = 0;
+ p = own_buf + strlen("QCatchSyscalls:1");
+ while (*p)
+ {
+ if (*p++ == ';')
+ syscalls_to_catch_size++;
+ }
+ if (syscalls_to_catch_size > 0)
+ {
+ syscalls_to_catch = xmalloc (syscalls_to_catch_size * sizeof (int));
+ p = strchr(own_buf, ';') + 1;
+ for (i = 0; i < syscalls_to_catch_size; i++)
+ {
+ p = decode_address_to_semicolon (&sysno, p);
+ syscalls_to_catch[i] = (int) sysno;
+ }
+ }
+ strcpy (own_buf, "OK");
+ return;
+ }
+
+ if (strcmp ("QCatchSyscalls:0", own_buf) == 0)
+ {
+ catching_syscalls_p = 0;
+ strcpy (own_buf, "OK");
+ return;
+ }
+
if (strncmp ("QProgramSignals:", own_buf, strlen ("QProgramSignals:")) == 0)
{
int numsigs = (int) GDB_SIGNAL_LAST, i;
@@ -1744,6 +1787,9 @@ handle_query (char *own_buf, int packet_
"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+");
Index: gdbserver/server.h
===================================================================
RCS file: /cvs/src/src/gdb/gdbserver/server.h,v
retrieving revision 1.118
diff -u -p -r1.118 server.h
--- gdbserver/server.h 5 Sep 2013 20:45:39 -0000 1.118
+++ gdbserver/server.h 29 Sep 2013 14:20:35 -0000
@@ -115,6 +115,15 @@ extern int server_waiting;
extern int debug_threads;
extern int debug_hw_points;
extern int pass_signals[];
+
+/* Set to 1 if GDB is catching some (or all) syscalls, zero otherwise. */
+extern int catching_syscalls_p;
+/* syscalls_to_catch is the list of syscalls to report to GDB.
+ If catching_syscalls_p and syscalls_to_catch == NULL, it means
+ all syscalls must be reported. */
+extern int syscalls_to_catch_size;
+extern int *syscalls_to_catch;
+
extern int program_signals[];
extern int program_signals_p;

Index: gdbserver/target.h
===================================================================
RCS file: /cvs/src/src/gdb/gdbserver/target.h,v
retrieving revision 1.71
diff -u -p -r1.71 target.h
--- gdbserver/target.h 5 Sep 2013 20:41:22 -0000 1.71
+++ gdbserver/target.h 29 Sep 2013 14:20:35 -0000
@@ -268,6 +268,10 @@ struct target_ops
/* Target specific qSupported support. */
void (*process_qsupported) (const char *);

+ /* Return 1 if the target supports catch syscall, 0 (or leave the
+ callback NULL) otherwise. */
+ int (*supports_catch_syscall) (void);
+
/* Return 1 if the target supports tracepoints, 0 (or leave the
callback NULL) otherwise. */
int (*supports_tracepoints) (void);
@@ -414,6 +418,10 @@ int kill_inferior (int);
the_target->process_qsupported (query); \
} 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)
Index: gdbserver/win32-low.c
===================================================================
RCS file: /cvs/src/src/gdb/gdbserver/win32-low.c,v
retrieving revision 1.69
diff -u -p -r1.69 win32-low.c
--- gdbserver/win32-low.c 5 Sep 2013 20:45:39 -0000 1.69
+++ gdbserver/win32-low.c 29 Sep 2013 14:20:35 -0000
@@ -1824,6 +1824,7 @@ static struct target_ops win32_target_op
NULL, /* core_of_thread */
NULL, /* read_loadmap */
NULL, /* process_qsupported */
+ NULL, /* supports_catch_syscall */
NULL, /* supports_tracepoints */
NULL, /* read_pc */
NULL, /* write_pc */
Index: testsuite/gdb.base/catch-syscall.exp
===================================================================
RCS file: /cvs/src/src/gdb/testsuite/gdb.base/catch-syscall.exp,v
retrieving revision 1.19
diff -u -p -r1.19 catch-syscall.exp
--- testsuite/gdb.base/catch-syscall.exp 22 Aug 2013 20:32:54 -0000 1.19
+++ testsuite/gdb.base/catch-syscall.exp 29 Sep 2013 14:20:36 -0000
@@ -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
}

@@ -28,6 +28,14 @@ if {![istarget "hppa*-hp-hpux*"] && ![is
continue
}

+# This shall be updated whenever QCatchSyscalls packet support is implemented
+# on some gdbserver architecture.
+if { [is_remote target]
+ && ![istarget "x86_64-*-linux*"]
+ && ![istarget "i\[34567\]86-*-linux*"] } {
+ continue
+}
+
# This shall be updated whenever 'catch syscall' is implemented
# on some architecture.
#if { ![istarget "i\[34567\]86-*-linux*"]