Re: [PATCH 01/31] displaced step: pass down target_waitstatus instead of gdb_signal

Andrew Burgess via Gdb-patches
2023-03-27T12:40:40Z

Pedro Alves <pedro@palves.net> writes:

> Hi!
>
> On 2023-03-22 9:29 p.m., Andrew Burgess wrote:
>> Andrew Burgess <aburgess@redhat.com> writes:
>>
> ...
>>> I took a look through and I'm happy with it. But I would like you to
>>> consider holding off until my displaced step patch has some feedback.
>>>
>>> I'm currently rebasing the patch. My patch deletes
>>> displaced_step_instruction_executed_successfully, which I realised makes
>>> passing the signal (or now target_waitstatus) redundant. As such I'm
>>> just testing an additional patch in the series which touches every place
>>> you're touching - but removes the signal instead of changing it.
>>>
>>> I hope to post my updated series later today (once testing completes).
>>
>> Pedro,
>>
>> Thanks for your feedback on my displaced stepping series. You're right
>> that just checking the $pc isn't going to be enough. So I'm now
>> thinking that I should be passing the gdb_signal through to the
>> gdbarch_displaced_step_fixup function.
>
> I guess passing down a boolean (or enum) indicating "success/failure" would
> also be an alternative. That may avoid every arch having to do the
> same check.

That's what I did in the end. I posted a V3 for my displaced step series.

>
>>
>> Rather than change things to pass through the gdb_signal though, and
>> then have this patch come along and s/gdb_signal/target_waitstatus/, I
>> wonder how you'd feel about merging this patch sooner rather than later?
>>
>> I'm planning to rebase my displaced stepping series off this patch -- I
>> just want to check you'd be OK with this patch possibly landing before
>> the rest of this series?
>
> I'm absolutely fine with putting this in before the rest of this series.
>
> How about I just merge it immediately, so none of us have to carry it
> around?

That would be great, as our patches will have a minor merge conflict in
displaced-stepping.c.

>
> I've updated the commit log a bit so it doesn't assume it is being merged along
> the rest of the series.
>
> From 7abd5c8ee74055621dc3a73fbcf2e8940712bb01 Mon Sep 17 00:00:00 2001
> From: Pedro Alves <pedro@palves.net>
> Date: Tue, 22 Jun 2021 15:42:51 +0100
> Subject: [PATCH] displaced step: pass down target_waitstatus instead of
> gdb_signal
>
> This commit tweaks displaced_step_finish & friends to pass down a
> target_waitstatus instead of a gdb_signal. This is needed because a
> patch later in the step-over-{thread-exit,clone] series will want to
> make displaced_step_buffers::finish handle
> TARGET_WAITKIND_THREAD_EXITED. It also helps with the
> TARGET_WAITKIND_THREAD_CLONED patch later in that same series.
>
> It's also a bit more logical this way, as we don't have to pass down
> signals when the thread didn't actually stop for a signal. So we can
> also think of it as a clean up.
>
> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=27338
> Change-Id: I4c5d338647b028071bc498c4e47063795a2db4c0
> Approved-By: Andrew Burgess <aburgess@redhat.com>

LGTM.

Thanks,
Andrew

> ---
> gdb/displaced-stepping.c | 16 +++++++++++-----
> gdb/displaced-stepping.h | 2 +-
> gdb/gdbarch-gen.h | 4 ++--
> gdb/gdbarch.c | 4 ++--
> gdb/gdbarch_components.py | 2 +-
> gdb/infrun.c | 17 +++++++----------
> gdb/linux-tdep.c | 5 +++--
> gdb/linux-tdep.h | 2 +-
> gdb/rs6000-tdep.c | 4 ++--
> 9 files changed, 30 insertions(+), 26 deletions(-)
>
> diff --git a/gdb/displaced-stepping.c b/gdb/displaced-stepping.c
> index 9f98ea8c35b..3fefdf322d8 100644
> --- a/gdb/displaced-stepping.c
> +++ b/gdb/displaced-stepping.c
> @@ -192,12 +192,18 @@ write_memory_ptid (ptid_t ptid, CORE_ADDR memaddr,
> }
>
> static bool
> -displaced_step_instruction_executed_successfully (gdbarch *arch,
> - gdb_signal signal)
> +displaced_step_instruction_executed_successfully
> + (gdbarch *arch, const target_waitstatus &status)
> {
> - if (signal != GDB_SIGNAL_TRAP)
> + if (status.kind () == TARGET_WAITKIND_STOPPED
> + && status.sig () != GDB_SIGNAL_TRAP)
> return false;
>
> + /* All other (thread event) waitkinds can only happen if the
> + instruction fully executed. For example, a fork, or a syscall
> + entry can only happen if the syscall instruction actually
> + executed. */
> +
> if (target_stopped_by_watchpoint ())
> {
> if (gdbarch_have_nonsteppable_watchpoint (arch)
> @@ -210,7 +216,7 @@ displaced_step_instruction_executed_successfully (gdbarch *arch,
>
> displaced_step_finish_status
> displaced_step_buffers::finish (gdbarch *arch, thread_info *thread,
> - gdb_signal sig)
> + const target_waitstatus &status)
> {
> gdb_assert (thread->displaced_step_state.in_progress ());
>
> @@ -256,7 +262,7 @@ displaced_step_buffers::finish (gdbarch *arch, thread_info *thread,
> regcache *rc = get_thread_regcache (thread);
>
> bool instruction_executed_successfully
> - = displaced_step_instruction_executed_successfully (arch, sig);
> + = displaced_step_instruction_executed_successfully (arch, status);
>
> if (instruction_executed_successfully)
> {
> diff --git a/gdb/displaced-stepping.h b/gdb/displaced-stepping.h
> index e154927ad92..d2c3fc1b2b4 100644
> --- a/gdb/displaced-stepping.h
> +++ b/gdb/displaced-stepping.h
> @@ -168,7 +168,7 @@ struct displaced_step_buffers
> CORE_ADDR &displaced_pc);
>
> displaced_step_finish_status finish (gdbarch *arch, thread_info *thread,
> - gdb_signal sig);
> + const target_waitstatus &status);
>
> const displaced_step_copy_insn_closure *
> copy_insn_closure_by_addr (CORE_ADDR addr);
> diff --git a/gdb/gdbarch-gen.h b/gdb/gdbarch-gen.h
> index a3fc0b9272b..bbf2376fc4b 100644
> --- a/gdb/gdbarch-gen.h
> +++ b/gdb/gdbarch-gen.h
> @@ -1101,8 +1101,8 @@ extern void set_gdbarch_displaced_step_prepare (struct gdbarch *gdbarch, gdbarch
>
> /* Clean up after a displaced step of THREAD. */
>
> -typedef displaced_step_finish_status (gdbarch_displaced_step_finish_ftype) (struct gdbarch *gdbarch, thread_info *thread, gdb_signal sig);
> -extern displaced_step_finish_status gdbarch_displaced_step_finish (struct gdbarch *gdbarch, thread_info *thread, gdb_signal sig);
> +typedef displaced_step_finish_status (gdbarch_displaced_step_finish_ftype) (struct gdbarch *gdbarch, thread_info *thread, const target_waitstatus &ws);
> +extern displaced_step_finish_status gdbarch_displaced_step_finish (struct gdbarch *gdbarch, thread_info *thread, const target_waitstatus &ws);
> extern void set_gdbarch_displaced_step_finish (struct gdbarch *gdbarch, gdbarch_displaced_step_finish_ftype *displaced_step_finish);
>
> /* Return the closure associated to the displaced step buffer that is at ADDR. */
> diff --git a/gdb/gdbarch.c b/gdb/gdbarch.c
> index b676e346fd0..84beb087336 100644
> --- a/gdb/gdbarch.c
> +++ b/gdb/gdbarch.c
> @@ -4098,13 +4098,13 @@ set_gdbarch_displaced_step_prepare (struct gdbarch *gdbarch,
> }
>
> displaced_step_finish_status
> -gdbarch_displaced_step_finish (struct gdbarch *gdbarch, thread_info *thread, gdb_signal sig)
> +gdbarch_displaced_step_finish (struct gdbarch *gdbarch, thread_info *thread, const target_waitstatus &ws)
> {
> gdb_assert (gdbarch != NULL);
> gdb_assert (gdbarch->displaced_step_finish != NULL);
> if (gdbarch_debug >= 2)
> gdb_printf (gdb_stdlog, "gdbarch_displaced_step_finish called\n");
> - return gdbarch->displaced_step_finish (gdbarch, thread, sig);
> + return gdbarch->displaced_step_finish (gdbarch, thread, ws);
> }
>
> void
> diff --git a/gdb/gdbarch_components.py b/gdb/gdbarch_components.py
> index 2b1a2b4f602..52beaeaa245 100644
> --- a/gdb/gdbarch_components.py
> +++ b/gdb/gdbarch_components.py
> @@ -1819,7 +1819,7 @@ Clean up after a displaced step of THREAD.
> """,
> type="displaced_step_finish_status",
> name="displaced_step_finish",
> - params=[("thread_info *", "thread"), ("gdb_signal", "sig")],
> + params=[("thread_info *", "thread"), ("const target_waitstatus &", "ws")],
> predefault="NULL",
> invalid="(! gdbarch->displaced_step_finish) != (! gdbarch->displaced_step_prepare)",
> )
> diff --git a/gdb/infrun.c b/gdb/infrun.c
> index 5c9babb9104..ee812baf8da 100644
> --- a/gdb/infrun.c
> +++ b/gdb/infrun.c
> @@ -1895,7 +1895,8 @@ displaced_step_prepare (thread_info *thread)
> DISPLACED_STEP_FINISH_STATUS_OK as well. */
>
> static displaced_step_finish_status
> -displaced_step_finish (thread_info *event_thread, enum gdb_signal signal)
> +displaced_step_finish (thread_info *event_thread,
> + const target_waitstatus &event_status)
> {
> displaced_step_thread_state *displaced = &event_thread->displaced_step_state;
>
> @@ -1917,7 +1918,7 @@ displaced_step_finish (thread_info *event_thread, enum gdb_signal signal)
> /* Do the fixup, and release the resources acquired to do the displaced
> step. */
> return gdbarch_displaced_step_finish (displaced->get_original_gdbarch (),
> - event_thread, signal);
> + event_thread, event_status);
> }
>
> /* Data to be passed around while handling an event. This data is
> @@ -5128,7 +5129,7 @@ handle_one (const wait_one_event &event)
> /* We caught the event that we intended to catch, so
> there's no event to save as pending. */
>
> - if (displaced_step_finish (t, GDB_SIGNAL_0)
> + if (displaced_step_finish (t, event.ws)
> == DISPLACED_STEP_FINISH_STATUS_NOT_EXECUTED)
> {
> /* Add it back to the step-over queue. */
> @@ -5143,7 +5144,6 @@ handle_one (const wait_one_event &event)
> }
> else
> {
> - enum gdb_signal sig;
> struct regcache *regcache;
>
> infrun_debug_printf
> @@ -5154,10 +5154,7 @@ handle_one (const wait_one_event &event)
> /* Record for later. */
> save_waitstatus (t, event.ws);
>
> - sig = (event.ws.kind () == TARGET_WAITKIND_STOPPED
> - ? event.ws.sig () : GDB_SIGNAL_0);
> -
> - if (displaced_step_finish (t, sig)
> + if (displaced_step_finish (t, event.ws)
> == DISPLACED_STEP_FINISH_STATUS_NOT_EXECUTED)
> {
> /* Add it back to the step-over queue. */
> @@ -5759,7 +5756,7 @@ handle_inferior_event (struct execution_control_state *ecs)
> has been done. Perform cleanup for parent process here. Note
> that this operation also cleans up the child process for vfork,
> because their pages are shared. */
> - displaced_step_finish (ecs->event_thread, GDB_SIGNAL_TRAP);
> + displaced_step_finish (ecs->event_thread, ecs->ws);
> /* Start a new step-over in another thread if there's one
> that needs it. */
> start_step_over ();
> @@ -6124,7 +6121,7 @@ resumed_thread_with_pending_status (struct thread_info *tp,
> static int
> finish_step_over (struct execution_control_state *ecs)
> {
> - displaced_step_finish (ecs->event_thread, ecs->event_thread->stop_signal ());
> + displaced_step_finish (ecs->event_thread, ecs->ws);
>
> bool had_step_over_info = step_over_info_valid_p ();
>
> diff --git a/gdb/linux-tdep.c b/gdb/linux-tdep.c
> index d0bda5ad9c4..1fc9cb6faee 100644
> --- a/gdb/linux-tdep.c
> +++ b/gdb/linux-tdep.c
> @@ -2626,13 +2626,14 @@ linux_displaced_step_prepare (gdbarch *arch, thread_info *thread,
> /* See linux-tdep.h. */
>
> displaced_step_finish_status
> -linux_displaced_step_finish (gdbarch *arch, thread_info *thread, gdb_signal sig)
> +linux_displaced_step_finish (gdbarch *arch, thread_info *thread,
> + const target_waitstatus &status)
> {
> linux_info *per_inferior = get_linux_inferior_data (thread->inf);
>
> gdb_assert (per_inferior->disp_step_bufs.has_value ());
>
> - return per_inferior->disp_step_bufs->finish (arch, thread, sig);
> + return per_inferior->disp_step_bufs->finish (arch, thread, status);
> }
>
> /* See linux-tdep.h. */
> diff --git a/gdb/linux-tdep.h b/gdb/linux-tdep.h
> index 16e1b806b26..e09a6ef32b1 100644
> --- a/gdb/linux-tdep.h
> +++ b/gdb/linux-tdep.h
> @@ -72,7 +72,7 @@ extern displaced_step_prepare_status linux_displaced_step_prepare
> /* Implementation of gdbarch_displaced_step_finish. */
>
> extern displaced_step_finish_status linux_displaced_step_finish
> - (gdbarch *arch, thread_info *thread, gdb_signal sig);
> + (gdbarch *arch, thread_info *thread, const target_waitstatus &status);
>
> /* Implementation of gdbarch_displaced_step_copy_insn_closure_by_addr. */
>
> diff --git a/gdb/rs6000-tdep.c b/gdb/rs6000-tdep.c
> index 52dcc89b2df..8b400047cfb 100644
> --- a/gdb/rs6000-tdep.c
> +++ b/gdb/rs6000-tdep.c
> @@ -1089,13 +1089,13 @@ ppc_displaced_step_prepare (gdbarch *arch, thread_info *thread,
>
> static displaced_step_finish_status
> ppc_displaced_step_finish (gdbarch *arch, thread_info *thread,
> - gdb_signal sig)
> + const target_waitstatus &status)
> {
> ppc_inferior_data *per_inferior = get_ppc_per_inferior (thread->inf);
>
> gdb_assert (per_inferior->disp_step_buf.has_value ());
>
> - return per_inferior->disp_step_buf->finish (arch, thread, sig);
> + return per_inferior->disp_step_buf->finish (arch, thread, status);
> }
>
> /* Implementation of gdbarch_displaced_step_restore_all_in_ptid. */
>
> base-commit: 91ffa03af1cc32515190c3b52d7b964f5abead5f
> --
> 2.36.0