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Wrap xfer_partial and enable_btrace for Ravenscar

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A gdb crash showed that the xfer_partial target method was not wrapped
for Ravenscar.  This caused remote.c to call
remote::set_general_thread with a Ravenscar "fake" ptid, which showed
up later as an event ptid.

I went through all the target methods and looked to see which ones
could call set_general_thread or set_continue_thread (but not
set_general_process, as I think Ravenscar targets aren't
multi-inferior).  This patch wraps the two that I found.

xfer_partial requires special treatment, because it can be called
recursively via get_base_thread_from_ravenscar_task.  To avoid a
recursive call, this patch changes update_thread_list to record all
tasks in the m_cpu_map, and changes get_thread_base_cpu to prefer this
map.  This avoids some memory reads.

It was unclear to me whether enable_btrace really makes sense for
Ravenscar; but at the same time it seemed harmless to add this patch.

gdb/ChangeLog
2020-08-07  Tom Tromey  <tromey@adacore.com>

	* ravenscar-thread.c (xfer_partial, enable_btrace, add_thread):
	New methods.
	(ravenscar_thread_target::get_thread_base_cpu): Check m_cpu_map
	first.
	(ravenscar_thread_target::add_thread): Rename from
	ravenscar_add_thread.
	(ravenscar_thread_target::update_thread_list): Use a lambda.
	(ravenscar_thread_target::xfer_partial): New method.
This commit is contained in:
Tom Tromey 2020-08-07 10:26:45 -06:00
parent 78c02f21ad
commit 2080266b77
2 changed files with 65 additions and 10 deletions
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11
gdb/ChangeLog
View File

@ -1,3 +1,14 @@
2020-08-07 Tom Tromey <tromey@adacore.com>
* ravenscar-thread.c (xfer_partial, enable_btrace, add_thread):
New methods.
(ravenscar_thread_target::get_thread_base_cpu): Check m_cpu_map
first.
(ravenscar_thread_target::add_thread): Rename from
ravenscar_add_thread.
(ravenscar_thread_target::update_thread_list): Use a lambda.
(ravenscar_thread_target::xfer_partial): New method.
2020-08-07 Tom Tromey <tromey@adacore.com>
* ada-lang.h (ada_task_list_iterator_ftype): Now a

64
gdb/ravenscar-thread.c
View File

@ -103,6 +103,13 @@ struct ravenscar_thread_target final : public target_ops
bool stopped_data_address (CORE_ADDR *) override;
enum target_xfer_status xfer_partial (enum target_object object,
const char *annex,
gdb_byte *readbuf,
const gdb_byte *writebuf,
ULONGEST offset, ULONGEST len,
ULONGEST *xfered_len) override;
bool thread_alive (ptid_t ptid) override;
int core_of_thread (ptid_t ptid) override;
@ -113,6 +120,14 @@ struct ravenscar_thread_target final : public target_ops
ptid_t get_ada_task_ptid (long lwp, long thread) override;
struct btrace_target_info *enable_btrace (ptid_t ptid,
const struct btrace_config *conf)
override
{
ptid = get_base_thread_from_ravenscar_task (ptid);
return beneath ()->enable_btrace (ptid, conf);
}
void mourn_inferior () override;
void close () override
@ -134,6 +149,7 @@ struct ravenscar_thread_target final : public target_ops
bool runtime_initialized ();
int get_thread_base_cpu (ptid_t ptid);
ptid_t get_base_thread_from_ravenscar_task (ptid_t ptid);
void add_thread (struct ada_task_info *task);
/* This maps a TID to the CPU on which it was running. This is
needed because sometimes the runtime will report an active task
@ -170,16 +186,18 @@ ravenscar_thread_target::get_thread_base_cpu (ptid_t ptid)
if (is_ravenscar_task (ptid))
{
struct ada_task_info *task_info = ada_get_task_info_from_ptid (ptid);
/* Prefer to not read inferior memory if possible, to avoid
reentrancy problems with xfer_partial. */
auto iter = m_cpu_map.find (ptid.tid ());
if (task_info != NULL)
base_cpu = task_info->base_cpu;
if (iter != m_cpu_map.end ())
base_cpu = iter->second;
else
{
auto iter = m_cpu_map.find (ptid.tid ());
struct ada_task_info *task_info = ada_get_task_info_from_ptid (ptid);
gdb_assert (iter != m_cpu_map.end ());
base_cpu = iter->second;
gdb_assert (task_info != NULL);
base_cpu = task_info->base_cpu;
}
}
else
@ -383,11 +401,14 @@ ravenscar_thread_target::wait (ptid_t ptid,
/* Add the thread associated to the given TASK to the thread list
(if the thread has already been added, this is a no-op). */
static void
ravenscar_add_thread (struct ada_task_info *task)
void
ravenscar_thread_target::add_thread (struct ada_task_info *task)
{
if (find_thread_ptid (current_inferior (), task->ptid) == NULL)
add_thread (current_inferior ()->process_target (), task->ptid);
{
::add_thread (current_inferior ()->process_target (), task->ptid);
m_cpu_map[task->ptid.tid ()] = task->base_cpu;
}
}
void
@ -398,7 +419,10 @@ ravenscar_thread_target::update_thread_list ()
(m_base_ptid) and the running thread, that may not have been included
to system.tasking.debug's list yet. */
iterate_over_live_ada_tasks (ravenscar_add_thread);
iterate_over_live_ada_tasks ([=] (struct ada_task_info *task)
{
this->add_thread (task);
});
}
ptid_t
@ -541,6 +565,26 @@ ravenscar_thread_target::core_of_thread (ptid_t ptid)
return beneath ()->core_of_thread (inferior_ptid);
}
/* Implement the target xfer_partial method. */
enum target_xfer_status
ravenscar_thread_target::xfer_partial (enum target_object object,
const char *annex,
gdb_byte *readbuf,
const gdb_byte *writebuf,
ULONGEST offset, ULONGEST len,
ULONGEST *xfered_len)
{
scoped_restore save_ptid = make_scoped_restore (&inferior_ptid);
/* Calling get_base_thread_from_ravenscar_task can read memory from
the inferior. However, that function is written to prefer our
internal map, so it should not result in recursive calls in
practice. */
inferior_ptid = get_base_thread_from_ravenscar_task (inferior_ptid);
return beneath ()->xfer_partial (object, annex, readbuf, writebuf,
offset, len, xfered_len);
}
/* Observer on inferior_created: push ravenscar thread stratum if needed. */
static void