From 2dd1cd011c097c6c754c2317fef678bd92efdf72 Mon Sep 17 00:00:00 2001 From: Simon Marchi Date: Mon, 20 Jul 2020 16:40:35 -0400 Subject: gdb: pass target to thread_ptid_changed observable I noticed what I think is a potential bug. I did not observe it nor was I able to reproduce it using actual debugging. It's quite unlikely, because it involves multi-target and ptid clashes. I added selftests that demonstrate it though. The thread_ptid_changed observer says that thread with OLD_PTID now has NEW_PTID. Now, if for some reason we happen to have two targets defining a thread with OLD_PTID, the observers don't know which thread this is about. regcache::regcache_thread_ptid_changed changes all regcaches with OLD_PTID. If there is a regcache for a thread with ptid OLD_PTID, but that belongs to a different target, this regcache will be erroneously changed. Similarly, infrun_thread_ptid_changed updates inferior_ptid if inferior_ptid matches OLD_PTID. But if inferior_ptid currently refers not to the thread is being changed, but to a thread with the same ptid belonging to a different target, then inferior_ptid will erroneously be changed. This patch adds a `process_stratum_target *` parameter to the `thread_ptid_changed` observable and makes the two observers use it. Tests for both are added, which would fail if the corresponding fix wasn't done. gdb/ChangeLog: * observable.h (thread_ptid_changed): Add parameter `process_stratum_target *`. * infrun.c (infrun_thread_ptid_changed): Add parameter `process_stratum_target *` and use it. (selftests): New namespace. (infrun_thread_ptid_changed): New function. (_initialize_infrun): Register selftest. * regcache.c (regcache_thread_ptid_changed): Add parameter `process_stratum_target *` and use it. (regcache_thread_ptid_changed): New function. (_initialize_regcache): Register selftest. * thread.c (thread_change_ptid): Pass target to thread_ptid_changed observable. Change-Id: I0599e61224b6d154a7b55088a894cb88298c3c71 --- gdb/infrun.c | 78 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-- gdb/observable.h | 6 +++-- gdb/regcache.c | 65 ++++++++++++++++++++++++++++++++++++++++++++-- gdb/thread.c | 2 +- 4 files changed, 144 insertions(+), 7 deletions(-) diff --git a/gdb/infrun.c b/gdb/infrun.c index ca850f8..7be1fed 100644 --- a/gdb/infrun.c +++ b/gdb/infrun.c @@ -67,6 +67,9 @@ #include "gdbsupport/gdb_select.h" #include #include "async-event.h" +#include "gdbsupport/selftest.h" +#include "scoped-mock-context.h" +#include "test-target.h" /* Prototypes for local functions */ @@ -2068,9 +2071,11 @@ start_step_over (void) /* Update global variables holding ptids to hold NEW_PTID if they were holding OLD_PTID. */ static void -infrun_thread_ptid_changed (ptid_t old_ptid, ptid_t new_ptid) +infrun_thread_ptid_changed (process_stratum_target *target, + ptid_t old_ptid, ptid_t new_ptid) { - if (inferior_ptid == old_ptid) + if (inferior_ptid == old_ptid + && current_inferior ()->process_target () == target) inferior_ptid = new_ptid; } @@ -9455,6 +9460,70 @@ infrun_async_inferior_event_handler (gdb_client_data data) inferior_event_handler (INF_REG_EVENT); } +namespace selftests +{ + +/* Verify that when two threads with the same ptid exist (from two different + targets) and one of them changes ptid, we only update inferior_ptid if + it is appropriate. */ + +static void +infrun_thread_ptid_changed () +{ + gdbarch *arch = current_inferior ()->gdbarch; + + /* The thread which inferior_ptid represents changes ptid. */ + { + scoped_restore_current_pspace_and_thread restore; + + scoped_mock_context target1 (arch); + scoped_mock_context target2 (arch); + target2.mock_inferior.next = &target1.mock_inferior; + + ptid_t old_ptid (111, 222); + ptid_t new_ptid (111, 333); + + target1.mock_inferior.pid = old_ptid.pid (); + target1.mock_thread.ptid = old_ptid; + target2.mock_inferior.pid = old_ptid.pid (); + target2.mock_thread.ptid = old_ptid; + + auto restore_inferior_ptid = make_scoped_restore (&inferior_ptid, old_ptid); + set_current_inferior (&target1.mock_inferior); + + thread_change_ptid (&target1.mock_target, old_ptid, new_ptid); + + gdb_assert (inferior_ptid == new_ptid); + } + + /* A thread with the same ptid as inferior_ptid, but from another target, + changes ptid. */ + { + scoped_restore_current_pspace_and_thread restore; + + scoped_mock_context target1 (arch); + scoped_mock_context target2 (arch); + target2.mock_inferior.next = &target1.mock_inferior; + + ptid_t old_ptid (111, 222); + ptid_t new_ptid (111, 333); + + target1.mock_inferior.pid = old_ptid.pid (); + target1.mock_thread.ptid = old_ptid; + target2.mock_inferior.pid = old_ptid.pid (); + target2.mock_thread.ptid = old_ptid; + + auto restore_inferior_ptid = make_scoped_restore (&inferior_ptid, old_ptid); + set_current_inferior (&target2.mock_inferior); + + thread_change_ptid (&target1.mock_target, old_ptid, new_ptid); + + gdb_assert (inferior_ptid == old_ptid); + } +} + +} /* namespace selftests */ + void _initialize_infrun (); void _initialize_infrun () @@ -9756,4 +9825,9 @@ or signalled."), show_observer_mode, &setlist, &showlist); + +#if GDB_SELF_TEST + selftests::register_test ("infrun_thread_ptid_changed", + selftests::infrun_thread_ptid_changed); +#endif } diff --git a/gdb/observable.h b/gdb/observable.h index 070cf0f..da0a9b1 100644 --- a/gdb/observable.h +++ b/gdb/observable.h @@ -27,6 +27,7 @@ struct so_list; struct objfile; struct thread_info; struct inferior; +struct process_stratum_target; struct trace_state_variable; namespace gdb @@ -165,8 +166,9 @@ extern observable architecture_changed; /* The thread's ptid has changed. The OLD_PTID parameter specifies the old value, and NEW_PTID specifies the new value. */ -extern observable - thread_ptid_changed; +extern observable + thread_ptid_changed; /* The inferior INF has been added to the list of inferiors. At this point, it might not be associated with any process. */ diff --git a/gdb/regcache.c b/gdb/regcache.c index 54354fe..46fbb07 100644 --- a/gdb/regcache.c +++ b/gdb/regcache.c @@ -414,11 +414,12 @@ regcache_observer_target_changed (struct target_ops *target) /* Update regcaches related to OLD_PTID to now use NEW_PTID. */ static void -regcache_thread_ptid_changed (ptid_t old_ptid, ptid_t new_ptid) +regcache_thread_ptid_changed (process_stratum_target *target, + ptid_t old_ptid, ptid_t new_ptid) { for (auto ®cache : regcaches) { - if (regcache->ptid () == old_ptid) + if (regcache->ptid () == old_ptid && regcache->target () == target) regcache->set_ptid (new_ptid); } } @@ -1817,6 +1818,64 @@ cooked_write_test (struct gdbarch *gdbarch) } } +/* Verify that when two threads with the same ptid exist (from two different + targets) and one of them changes ptid, we only update the appropriate + regcaches. */ + +static void +regcache_thread_ptid_changed () +{ + /* Any arch will do. */ + gdbarch *arch = current_inferior ()->gdbarch; + + /* Prepare two targets with one thread each, with the same ptid. */ + scoped_mock_context target1 (arch); + scoped_mock_context target2 (arch); + target2.mock_inferior.next = &target1.mock_inferior; + + ptid_t old_ptid (111, 222); + ptid_t new_ptid (111, 333); + + target1.mock_inferior.pid = old_ptid.pid (); + target1.mock_thread.ptid = old_ptid; + target2.mock_inferior.pid = old_ptid.pid (); + target2.mock_thread.ptid = old_ptid; + + gdb_assert (regcaches.empty ()); + + /* Populate the regcaches container. */ + get_thread_arch_aspace_regcache (&target1.mock_target, old_ptid, arch, + nullptr); + get_thread_arch_aspace_regcache (&target2.mock_target, old_ptid, arch, + nullptr); + + /* Return whether a regcache for (TARGET, PTID) exists in REGCACHES. */ + auto regcache_exists = [] (process_stratum_target *target, ptid_t ptid) + { + for (regcache *rc : regcaches) + { + if (rc->target () == target && rc->ptid () == ptid) + return true; + } + + return false; + }; + + gdb_assert (regcaches_size () == 2); + gdb_assert (regcache_exists (&target1.mock_target, old_ptid)); + gdb_assert (!regcache_exists (&target1.mock_target, new_ptid)); + gdb_assert (regcache_exists (&target2.mock_target, old_ptid)); + gdb_assert (!regcache_exists (&target2.mock_target, new_ptid)); + + thread_change_ptid (&target1.mock_target, old_ptid, new_ptid); + + gdb_assert (regcaches_size () == 2); + gdb_assert (!regcache_exists (&target1.mock_target, old_ptid)); + gdb_assert (regcache_exists (&target1.mock_target, new_ptid)); + gdb_assert (regcache_exists (&target2.mock_target, old_ptid)); + gdb_assert (!regcache_exists (&target2.mock_target, new_ptid)); +} + } // namespace selftests #endif /* GDB_SELF_TEST */ @@ -1840,5 +1899,7 @@ _initialize_regcache () selftests::cooked_read_test); selftests::register_test_foreach_arch ("regcache::cooked_write_test", selftests::cooked_write_test); + selftests::register_test ("regcache_thread_ptid_changed", + selftests::regcache_thread_ptid_changed); #endif } diff --git a/gdb/thread.c b/gdb/thread.c index 4dce1ef..c915407 100644 --- a/gdb/thread.c +++ b/gdb/thread.c @@ -775,7 +775,7 @@ thread_change_ptid (process_stratum_target *targ, tp = find_thread_ptid (inf, old_ptid); tp->ptid = new_ptid; - gdb::observers::thread_ptid_changed.notify (old_ptid, new_ptid); + gdb::observers::thread_ptid_changed.notify (targ, old_ptid, new_ptid); } /* See gdbthread.h. */ -- cgit v1.1