binutils-gdb/gdb/process-stratum-target.c
Simon Marchi 294c36eb6a gdb: on exec, delegate pushing / unpushing target and adding thread to target_ops::follow_exec
On "exec", some targets need to unpush themselves from the inferior,
and do some bookkeeping, like forgetting the data associated to the
exec'ing inferior.

One such example is the thread-db target.  It does so in
a special case in thread_db_target::wait, just before returning the
TARGET_WAITKIND_EXECD event to its caller.

We have another such case in the context of rocm-gdb [1], where the
"rocm" target is pushed on top of the linux-nat target.  When an exec
happens, we want to unpush the rocm target from the exec'ing inferior to
close some file descriptors that refer to the pre-exec address space and
forget about that inferior.  We then want to push the target on the
inferior in which execution continues, to open the file descriptors for
the post-exec address space.

I think that a good way to address this cleanly is to do all this in the
target_ops::follow_exec implementations.  Make the
process_stratum_target::follow_exec implementation have the default
behavior of pushing itself to the new inferior's target stack (if
execution continues in a new inferior) and add the initial thread.

remote_target::follow_exec is an example of process target that wants to
do a bit more than the default behavior.  So it calls
process_stratum_target::follow_exec first and does the extra work
second.

linux-thread-db (a non-process target) implements follow_exec to do some
bookeeping (forget about that process' data), before handing down the
event down to the process target (which hits
process_stratum_target::follow_exec).

gdb/ChangeLog:

	* target.h (struct target_ops) <follow_exec>: Add ptid_t
	parameter.
	(target_follow_exec): Likewise.
	* target.c (target_follow_exec): Add ptid_t parameter.
	* infrun.c (follow_exec): Adjust call to target_follow_exec,
	don't push target nor create thread.
	* linux-thread-db.c (class thread_db_target) <follow_exec>: New.
	(thread_db_target::wait): Just return on TARGET_WAITKIND_EXECD.
	(thread_db_target::follow_exec): New.
	* remote.c (class remote_target) <follow_exec>: Add ptid_t parameter.
	(remote_target::follow_exec): Call
	process_stratum_target::follow_exec.
	* target-delegates.c: Re-generate.

Change-Id: I3f96d0ba3ea0dde6540b7e1b4d5cdb01635088c8
2021-05-13 15:29:00 -04:00

131 lines
3.5 KiB
C

/* Abstract base class inherited by all process_stratum targets
Copyright (C) 2018-2021 Free Software Foundation, Inc.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include "defs.h"
#include "process-stratum-target.h"
#include "inferior.h"
process_stratum_target::~process_stratum_target ()
{
}
struct address_space *
process_stratum_target::thread_address_space (ptid_t ptid)
{
/* Fall-back to the "main" address space of the inferior. */
inferior *inf = find_inferior_ptid (this, ptid);
if (inf == NULL || inf->aspace == NULL)
internal_error (__FILE__, __LINE__,
_("Can't determine the current "
"address space of thread %s\n"),
target_pid_to_str (ptid).c_str ());
return inf->aspace;
}
struct gdbarch *
process_stratum_target::thread_architecture (ptid_t ptid)
{
inferior *inf = find_inferior_ptid (this, ptid);
gdb_assert (inf != NULL);
return inf->gdbarch;
}
bool
process_stratum_target::has_all_memory ()
{
/* If no inferior selected, then we can't read memory here. */
return inferior_ptid != null_ptid;
}
bool
process_stratum_target::has_memory ()
{
/* If no inferior selected, then we can't read memory here. */
return inferior_ptid != null_ptid;
}
bool
process_stratum_target::has_stack ()
{
/* If no inferior selected, there's no stack. */
return inferior_ptid != null_ptid;
}
bool
process_stratum_target::has_registers ()
{
/* Can't read registers from no inferior. */
return inferior_ptid != null_ptid;
}
bool
process_stratum_target::has_execution (inferior *inf)
{
/* If there's a process running already, we can't make it run
through hoops. */
return inf->pid != 0;
}
void
process_stratum_target::follow_exec (inferior *follow_inf, ptid_t ptid,
const char *execd_pathname)
{
inferior *orig_inf = current_inferior ();
if (orig_inf != follow_inf)
{
/* Execution continues in a new inferior, push the original inferior's
process target on the new inferior's target stack. The process target
may decide to unpush itself from the original inferior's target stack
after that, at its discretion. */
follow_inf->push_target (orig_inf->process_target ());
thread_info *t = add_thread (follow_inf->process_target (), ptid);
/* Leave the new inferior / thread as the current inferior / thread. */
switch_to_thread (t);
}
}
/* See process-stratum-target.h. */
std::set<process_stratum_target *>
all_non_exited_process_targets ()
{
/* Inferiors may share targets. To eliminate duplicates, use a set. */
std::set<process_stratum_target *> targets;
for (inferior *inf : all_non_exited_inferiors ())
targets.insert (inf->process_target ());
return targets;
}
/* See process-stratum-target.h. */
void
switch_to_target_no_thread (process_stratum_target *target)
{
for (inferior *inf : all_inferiors (target))
{
switch_to_inferior_no_thread (inf);
break;
}
}