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

Pedro Alves
2023-03-23T15:16:09Z

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.

>
> 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?

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>
---
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