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Re: [PATCH] Implement 'catch syscall' for gdbserver
- From: Josh Stone <jistone at redhat dot com>
- To: Doug Evans <xdje42 at gmail dot com>
- Cc: gdb-patches at sourceware dot org, sergiodj at redhat dot com, palves at redhat dot com, philippe dot waroquiers at skynet dot be
- Date: Tue, 24 Nov 2015 18:36:52 -0800
- Subject: Re: [PATCH] Implement 'catch syscall' for gdbserver
- Authentication-results: sourceware.org; auth=none
- References: <1446169946-28117-1-git-send-email-jistone at redhat dot com> <m3egfhtkk4 dot fsf at sspiff dot org>
Thanks for the review!
I'll go ahead and correct the style issues without further comment.
Other replies are inline.
I'll try to rebase and send updates tomorrow.
On 11/22/2015 08:18 PM, Doug Evans wrote:
> Josh Stone <jistone@redhat.com> writes:
>> 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.
>>
>> Based on work from Philippe Waroquiers <philippe.waroquiers@skynet.be>.
>>
>> Beyond simple rebasing, I've also updated it to store the syscall catch
>> lists uniquely to each target process, and updated entry/return logic
>> from checking ENOSYS to now matching gdb's current Linux logic.
>>
>> gdb/ChangeLog:
>>
>> 2015-10-29 Josh Stone <jistone@redhat.com>
>>
>> * NEWS (Changes since GDB 7.10): Mention QCatchSyscalls and new
>> GDBserver support for 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.
>>
>> gdb/doc/ChangeLog:
>>
>> 2015-10-29 Josh Stone <jistone@redhat.com>
>>
>> * 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 detailed list of stub features.
>>
>> gdb/gdbserver/ChangeLog:
>>
>> 2015-10-29 Josh Stone <jistone@redhat.com>
>>
>> * 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_resume 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 (SYSCALL_SIGTRAP): Define.
>> (handle_extended_wait): Mark syscall_state like an entry.
>> (get_syscall_trapinfo): New function, proxy to the_low_target.
>> (linux_low_ptrace_options): Enable PTRACE_O_TRACESYSGOOD.
>> (linux_low_filter_event): Set ptrace options even before arch-specific
>> setup. Either toggle syscall_state entry/return or set ignored.
>> (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.
>> * nto-low.c (nto_target_ops): Install NULL supports_catch_syscall.
>> * spu-low.c (spu_target_ops): Likewise.
>> * win32-low.c (win32_target_ops): Likewise.
>>
>> gdb/testsuite/ChangeLog:
>>
>> 2015-10-29 Josh Stone <jistone@redhat.com>
>>
>> * gdb.base/catch-syscall.exp: Enable testing for x86 and x86_64 linux
>> remote targets.
>> (do_syscall_tests): Only test mid-vfork on local or extended-remote.
>> ---
>> gdb/NEWS | 10 ++
>> gdb/doc/gdb.texinfo | 56 +++++++++++
>> gdb/gdbserver/inferiors.c | 1 +
>> gdb/gdbserver/inferiors.h | 5 +
>> gdb/gdbserver/linux-low.c | 158 +++++++++++++++++++++++++++++--
>> gdb/gdbserver/linux-low.h | 13 +++
>> gdb/gdbserver/linux-x86-low.c | 31 ++++++
>> gdb/gdbserver/nto-low.c | 1 +
>> gdb/gdbserver/remote-utils.c | 12 +++
>> gdb/gdbserver/server.c | 49 ++++++++++
>> gdb/gdbserver/server.h | 6 ++
>> gdb/gdbserver/spu-low.c | 1 +
>> gdb/gdbserver/target.h | 8 ++
>> gdb/gdbserver/win32-low.c | 1 +
>> gdb/remote.c | 116 +++++++++++++++++++++++
>> gdb/testsuite/gdb.base/catch-syscall.exp | 15 ++-
>> 16 files changed, 472 insertions(+), 11 deletions(-)
>>
>> diff --git a/gdb/NEWS b/gdb/NEWS
>> index b2b1e99d58c6..9c9b4b04a146 100644
>> --- a/gdb/NEWS
>> +++ b/gdb/NEWS
>> @@ -77,6 +77,11 @@ exec-events feature in qSupported
>> response can contain the corresponding 'stubfeature'. Set and
>> show commands can be used to display whether these features are enabled.
>>
>> +QCatchSyscalls:1 [;SYSNO]...
>> +QCatchSyscalls:0
>> + Enable ("QCatchSyscalls:1") or disable ("QCatchSyscalls:0")
>> + catching syscalls from the inferior process.
>> +
>> * Extended-remote exec events
>>
>> ** GDB now has support for exec events on extended-remote Linux targets.
>> @@ -87,6 +92,11 @@ set remote exec-event-feature-packet
>> show remote exec-event-feature-packet
>> Set/show the use of the remote exec event feature.
>>
>> +* New features in the GDB remote stub, GDBserver
>> +
>> + ** GDBserver now supports catch syscall. Currently enabled
>> + on x86/x86_64 GNU/Linux targets.
>> +
>> *** Changes in GDB 7.10
>>
>> * Support for process record-replay and reverse debugging on aarch64*-linux*
>> diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
>> index 3c1f7857393c..d8ed630da3fc 100644
>> --- a/gdb/doc/gdb.texinfo
>> +++ b/gdb/doc/gdb.texinfo
>> @@ -20121,6 +20121,10 @@ 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}}
>> @@ -35418,6 +35422,11 @@ 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.
>> @@ -35878,6 +35887,44 @@ 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 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
>> @@ -36296,6 +36343,11 @@ 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{-}
>> @@ -36489,6 +36541,10 @@ 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/inferiors.c b/gdb/gdbserver/inferiors.c
>> index 72a3ef1b1b61..a8263656a4af 100644
>> --- a/gdb/gdbserver/inferiors.c
>> +++ b/gdb/gdbserver/inferiors.c
>> @@ -316,6 +316,7 @@ 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 d7226163c0e8..43fc869f6612 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 +69,9 @@ struct process_info
>> /* The list of installed fast tracepoints. */
>> struct fast_tracepoint_jump *fast_tracepoint_jumps;
>>
>> + /* The list of syscalls to report, or just ANY_SYSCALL. */
>> + 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 41ab510fa4ac..c2c513130997 100644
>> --- a/gdb/gdbserver/linux-low.c
>> +++ b/gdb/gdbserver/linux-low.c
>> @@ -70,6 +70,11 @@
>> #define O_LARGEFILE 0
>> #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 already defined in nat/linux-nat.h.
Ah, indeed, and that's already included too. I'll nuke this.
>> /* Some targets did not define these ptrace constants from the start,
>> so gdbserver defines them locally here. In the future, these may
>> be removed after they are added to asm/ptrace.h. */
>> @@ -447,6 +452,11 @@ handle_extended_wait (struct lwp_info **orig_event_lwp, int wstat)
>> struct thread_info *event_thr = get_lwp_thread (event_lwp);
>> struct lwp_info *new_lwp;
>>
>> + /* 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))
>> {
>> @@ -662,6 +672,40 @@ 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.
>>
>> @@ -2154,6 +2198,8 @@ linux_low_ptrace_options (int attached)
>> if (report_exec_events)
>> options |= PTRACE_O_TRACEEXEC;
>>
>> + options |= PTRACE_O_TRACESYSGOOD;
>> +
>> return options;
>> }
>>
>> @@ -2249,6 +2295,16 @@ linux_low_filter_event (int lwpid, int wstat)
>>
>> gdb_assert (WIFSTOPPED (wstat));
>>
>> + /* Set ptrace flags ASAP, so no events can be missed. */
>> + if (WIFSTOPPED (wstat) && child->must_set_ptrace_flags)
>
> It's a bit weird to check WIFSTOPPED after we just asserted it's true,
> but I realize all the subsequent "if"s checks WIFSTOPPED too.
I agree it's weird, but as you say it's the local pattern.
>> + {
>> + struct process_info *proc = find_process_pid (pid_of (thread));
>> + int options = linux_low_ptrace_options (proc->attached);
>> +
>> + linux_enable_event_reporting (lwpid, options);
>> + child->must_set_ptrace_flags = 0;
>> + }
>> +
>
> Is moving the must_set_ptrace_flags check up to here good in general,
> or is it only necessary for this patch?
> I see that gdb/linux-nat.c does the must_set_ptrace_flags check early.
> [ref: gdb/linux.c line 2312: if (lp->must_set_ptrace_flags)]
> If this part of patch can be separated out, I think that'd be helpful.
Before I moved this, I was getting my first syscall trap as a plain
SIGTRAP, indicating PTRACE_O_TRACESYSGOOD wasn't set as desired. I
finally figured out that the following block with child->status_pending
was returning early, so must_set_ptrace_flags wasn't even checked.
It might even by my own peculiar setup though, as I was also testing
this with my own strace-over-gdbserver hack. I'm sure there are ways
that doesn't behave like a normal gdb client.
Anyway, I think it's probably a good change in general, especially to
mirror gdb's own behavior. In practice it may only matter for syscalls
or the weird way I was using it, but that's ok. It'll be easy to make
this piece a patch preceding the rest.
>> if (WIFSTOPPED (wstat))
>> {
>> struct process_info *proc;
>> @@ -2276,13 +2332,19 @@ linux_low_filter_event (int lwpid, int wstat)
>> }
>> }
>>
>> - if (WIFSTOPPED (wstat) && child->must_set_ptrace_flags)
>> + /* Always update syscall_state, even if it will be filtered later. */
>> + if (WIFSTOPPED (wstat) && WSTOPSIG (wstat) == SYSCALL_SIGTRAP)
>> {
>> - struct process_info *proc = find_process_pid (pid_of (thread));
>> - int options = linux_low_ptrace_options (proc->attached);
>> -
>> - linux_enable_event_reporting (lwpid, options);
>> - child->must_set_ptrace_flags = 0;
>> + child->syscall_state =
>> + child->syscall_state == TARGET_WAITKIND_SYSCALL_ENTRY
>> + ? TARGET_WAITKIND_SYSCALL_RETURN
>> + : TARGET_WAITKIND_SYSCALL_ENTRY;
>
> Our convention when wrapping on "=" is to put the "=" on the next line.
> Also, I'd put the expression in parens like this:
>
> 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
>> @@ -2885,6 +2947,44 @@ ignore_event (struct target_waitstatus *ourstatus)
>> return null_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
>> @@ -3195,6 +3295,22 @@ 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
>> @@ -3449,8 +3565,16 @@ 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
>> @@ -3867,6 +3991,7 @@ 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
>> @@ -4052,7 +4177,14 @@ 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;
>
> Unnecessary extra space after =.
>
>> + else
>> + ptrace_request = PTRACE_CONT;
>
> Ditto.
>
>> + 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. */
>> @@ -6135,6 +6267,13 @@ linux_process_qsupported (const char *query)
>> }
>>
>> 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)
>> @@ -7010,6 +7149,7 @@ static struct target_ops linux_target_ops = {
>> linux_common_core_of_thread,
>> linux_read_loadmap,
>> linux_process_qsupported,
>> + linux_supports_catch_syscall,
>> linux_supports_tracepoints,
>> linux_read_pc,
>> linux_write_pc,
>> diff --git a/gdb/gdbserver/linux-low.h b/gdb/gdbserver/linux-low.h
>> index ccf4c9421d87..71d72f48ea3a 100644
>> --- a/gdb/gdbserver/linux-low.h
>> +++ b/gdb/gdbserver/linux-low.h
>> @@ -201,6 +201,12 @@ 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);
>>
>> @@ -271,6 +277,13 @@ struct lwp_info
>> event already received in a wait()). */
>> int stopped;
>>
>> + /* Signal wether 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 89ec4e54b3b8..6e3c589de8fb 100644
>> --- a/gdb/gdbserver/linux-x86-low.c
>> +++ b/gdb/gdbserver/linux-x86-low.c
>> @@ -1432,6 +1432,36 @@ 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 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
>> + {
>> + 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;
>
> These casts are confusing, especially when coupled with the l_ prefix
> ("l" for "long" is the first thing that comes to mind, but these are ints).
> I can appreciate them when casting from long to int, but here we
> already have ints.
Ah, yeah, I think this is simply duped from the 64bit block.
> How about changing the parameters to sysno_ptr, sysret_ptr,
> and change l_sysno,l_sysret to sysno,sysret?
> Or some such.
I think we can just drop the locals entirely for this block and just
collect the registers directly into the sysno/sysret parameters.
>> + }
>> +}
>> +
>> static int
>> x86_supports_tracepoints (void)
>> {
>> @@ -3292,6 +3322,7 @@ struct linux_target_ops the_low_target =
>> x86_linux_new_fork,
>> 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,
>> diff --git a/gdb/gdbserver/nto-low.c b/gdb/gdbserver/nto-low.c
>> index d72c46515d13..1301acea49b7 100644
>> --- a/gdb/gdbserver/nto-low.c
>> +++ b/gdb/gdbserver/nto-low.c
>> @@ -979,6 +979,7 @@ static struct target_ops nto_target_ops = {
>> NULL, /* core_of_thread */
>> NULL, /* read_loadmap */
>> NULL, /* process_qsupported */
>> + NULL, /* supports_catch_syscall */
>> NULL, /* supports_tracepoints */
>> NULL, /* read_pc */
>> NULL, /* write_pc */
>> diff --git a/gdb/gdbserver/remote-utils.c b/gdb/gdbserver/remote-utils.c
>> index e36609176afa..19eed77d4874 100644
>> --- a/gdb/gdbserver/remote-utils.c
>> +++ b/gdb/gdbserver/remote-utils.c
>> @@ -1119,6 +1119,8 @@ prepare_resume_reply (char *buf, ptid_t ptid,
>> case TARGET_WAITKIND_VFORKED:
>> case TARGET_WAITKIND_VFORK_DONE:
>> case TARGET_WAITKIND_EXECD:
>> + case TARGET_WAITKIND_SYSCALL_ENTRY:
>> + case TARGET_WAITKIND_SYSCALL_RETURN:
>> {
>> struct thread_info *saved_thread;
>> const char **regp;
>> @@ -1161,6 +1163,16 @@ prepare_resume_reply (char *buf, ptid_t ptid,
>> status->value.execd_pathname = NULL;
>> buf += strlen (buf);
>> }
>> + 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 fd2804beaa4e..72621f261dfa 100644
>> --- a/gdb/gdbserver/server.c
>> +++ b/gdb/gdbserver/server.c
>> @@ -592,6 +592,52 @@ handle_general_set (char *own_buf)
>> return;
>> }
>>
>> + if (startswith (own_buf, "QCatchSyscalls:1"))
>> + {
>> + const char *p;
>> + CORE_ADDR sysno;
>> + struct process_info *process;
>> +
>> + if (!target_running () || !target_supports_catch_syscall ())
>> + {
>> + write_enn (own_buf);
>> + return;
>> + }
>> +
>> + process = current_process ();
>> +
>> + VEC_truncate (int, process->syscalls_to_catch, 0);
>> +
>> + p = own_buf + strlen("QCatchSyscalls:1");
>> + if (*p == ';')
>> + {
>> + p += 1;
>> + while (*p)
>> + {
>> + 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 ("QCatchSyscalls:0", own_buf) == 0)
>> + {
>> + if (!target_running () || !target_supports_catch_syscall ())
>> + {
>> + write_enn (own_buf);
>> + return;
>> + }
>> +
>> + VEC_free (int, current_process ()->syscalls_to_catch);
>> + write_ok (own_buf);
>> + return;
>> + }
>> +
>> if (startswith (own_buf, "QProgramSignals:"))
>> {
>> int numsigs = (int) GDB_SIGNAL_LAST, i;
>> @@ -2140,6 +2186,9 @@ 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 96ad4fa58b7c..a8780ebfbc65 100644
>> --- a/gdb/gdbserver/server.h
>> +++ b/gdb/gdbserver/server.h
>> @@ -133,4 +133,10 @@ 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/spu-low.c b/gdb/gdbserver/spu-low.c
>> index 89bed7a02dd1..55ec0caef296 100644
>> --- a/gdb/gdbserver/spu-low.c
>> +++ b/gdb/gdbserver/spu-low.c
>> @@ -699,6 +699,7 @@ static struct target_ops spu_target_ops = {
>> NULL, /* core_of_thread */
>> NULL, /* read_loadmap */
>> NULL, /* process_qsupported */
>> + NULL, /* supports_catch_syscall */
>> NULL, /* supports_tracepoints */
>> NULL, /* read_pc */
>> NULL, /* write_pc */
>> diff --git a/gdb/gdbserver/target.h b/gdb/gdbserver/target.h
>> index 769c876ede49..ef8a7680ccca 100644
>> --- a/gdb/gdbserver/target.h
>> +++ b/gdb/gdbserver/target.h
>> @@ -309,6 +309,10 @@ 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);
>> @@ -526,6 +530,10 @@ 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)
>> diff --git a/gdb/gdbserver/win32-low.c b/gdb/gdbserver/win32-low.c
>> index 6e33509c0b50..4314513876fa 100644
>> --- a/gdb/gdbserver/win32-low.c
>> +++ b/gdb/gdbserver/win32-low.c
>> @@ -1844,6 +1844,7 @@ static struct target_ops win32_target_ops = {
>> NULL, /* core_of_thread */
>> NULL, /* read_loadmap */
>> NULL, /* process_qsupported */
>> + NULL, /* supports_catch_syscall */
>> NULL, /* supports_tracepoints */
>> NULL, /* read_pc */
>> NULL, /* write_pc */
>> diff --git a/gdb/remote.c b/gdb/remote.c
>> index fed397affeab..41751e9d93b1 100644
>> --- a/gdb/remote.c
>> +++ b/gdb/remote.c
>> @@ -1388,6 +1388,7 @@ enum {
>> PACKET_qSupported,
>> PACKET_qTStatus,
>> PACKET_QPassSignals,
>> + PACKET_QCatchSyscalls,
>> PACKET_QProgramSignals,
>> PACKET_qCRC,
>> PACKET_qSearch_memory,
>> @@ -1973,6 +1974,99 @@ 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, *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 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])
>> + {
>> + 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 ("QCatchSyscalls:1")] = 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. */
>>
>> @@ -4328,6 +4422,8 @@ 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,
>> @@ -6159,6 +6255,22 @@ 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"))
>> @@ -12734,6 +12846,7 @@ 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_update_thread_list = remote_update_thread_list;
>> @@ -13263,6 +13376,9 @@ 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/gdb.base/catch-syscall.exp b/gdb/testsuite/gdb.base/catch-syscall.exp
>> index c1cfe23cdddb..0ba078db22ac 100644
>> --- a/gdb/testsuite/gdb.base/catch-syscall.exp
>> +++ b/gdb/testsuite/gdb.base/catch-syscall.exp
>> @@ -19,7 +19,15 @@
>> # 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
>> +}
>> +
>> +# 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
>> }
>>
>> @@ -390,7 +398,10 @@ proc do_syscall_tests {} {
>> if [runto_main] then { test_catch_syscall_skipping_return }
>>
>> # Testing the 'catch syscall' command starting mid-vfork.
>> - if [runto_main] then { test_catch_syscall_mid_vfork }
>> + # (Only local or extended-remote can use "catch vfork".)
>> + if { ![is_remote target] || [target_info gdb_protocol] == "extended-remote" } {
>> + if [runto_main] then { test_catch_syscall_mid_vfork }
>> + }
>>
>> # Testing if the 'catch syscall' command works when switching to
>> # different architectures on-the-fly (PR gdb/10737).