From 4b2f71e6c67060e2aa0d35652de80fdc1f810ce8 Mon Sep 17 00:00:00 2001 From: Andrew Burgess Date: Wed, 11 Oct 2023 10:30:35 +0100 Subject: [PATCH] gdb: replace architecture_changed with new_architecture observer This commit replaces the architecture_changed observer with a new_architecture observer. Currently the only user of the architecture_changed observer is the Python code, which uses this observer to register the Python unwinder with the architecture. The problem is that the architecture_changed observer is triggered from inferior::set_arch(), which only sees the inferior-wide gdbarch value. For targets that use thread-specific architectures, these never trigger the architecture_changed observer, and so never have the Python unwinder registered with them. When it comes to unwinding GDB makes use of the frame's gdbarch, which is based on the thread's regcache gdbarch, which is set in get_thread_regcache to the value returned from target_thread_architecture, which is not always the inferiors gdbarch value, it might be a thread-specific gdbarch which has not passed through inferior::set_arch(). The new_architecture observer will be triggered from gdbarch_find_by_info, whenever a new gdbarch is created and initialised. As GDB caches and reuses gdbarch values, we should expect to see each new architecture trigger the new_architecture observer just once. After this commit, targets that make use of thread-specific architectures should be able to make use of Python unwinders. As I don't have access to a machine that makes use of thread-specific architectures right now, I asked Luis to confirm that an AArch64 target that uses SVE/SME can't use the Python unwinders in threads that are using a thread-specific architectures, and he confirmed that this is indeed the case, see this discussion: https://inbox.sourceware.org/gdb/87wmvsat8i.fsf@redhat.com Tested-By: Lancelot Six Tested-By: Luis Machado Reviewed-By: Luis Machado Approved-By: Simon Marchi --- gdb/arch-utils.c | 2 ++ gdb/inferior.c | 1 - gdb/observable.c | 2 +- gdb/observable.h | 7 +++---- gdb/python/py-unwind.c | 5 ++--- 5 files changed, 8 insertions(+), 9 deletions(-) diff --git a/gdb/arch-utils.c b/gdb/arch-utils.c index 60a50ea5b2c..c64584c5760 100644 --- a/gdb/arch-utils.c +++ b/gdb/arch-utils.c @@ -1479,6 +1479,8 @@ gdbarch_find_by_info (struct gdbarch_info info) if (gdbarch_debug) gdbarch_dump (new_gdbarch, gdb_stdlog); + gdb::observers::new_architecture.notify (new_gdbarch); + return new_gdbarch; } diff --git a/gdb/inferior.c b/gdb/inferior.c index efe57cceae3..1778723863e 100644 --- a/gdb/inferior.c +++ b/gdb/inferior.c @@ -179,7 +179,6 @@ inferior::set_arch (gdbarch *arch) gdb_assert (arch != nullptr); gdb_assert (gdbarch_initialized_p (arch)); m_gdbarch = arch; - gdb::observers::architecture_changed.notify (this, arch); process_stratum_target *proc_target = this->process_target (); if (proc_target != nullptr) diff --git a/gdb/observable.c b/gdb/observable.c index 09613b2ddda..f2e65b11604 100644 --- a/gdb/observable.c +++ b/gdb/observable.c @@ -52,7 +52,7 @@ DEFINE_OBSERVABLE (about_to_proceed); DEFINE_OBSERVABLE (breakpoint_created); DEFINE_OBSERVABLE (breakpoint_deleted); DEFINE_OBSERVABLE (breakpoint_modified); -DEFINE_OBSERVABLE (architecture_changed); +DEFINE_OBSERVABLE (new_architecture); DEFINE_OBSERVABLE (thread_ptid_changed); DEFINE_OBSERVABLE (inferior_added); DEFINE_OBSERVABLE (inferior_appeared); diff --git a/gdb/observable.h b/gdb/observable.h index acb05e9b535..a535eedcd38 100644 --- a/gdb/observable.h +++ b/gdb/observable.h @@ -153,10 +153,9 @@ extern observable breakpoint_deleted; is the modified breakpoint. */ extern observable breakpoint_modified; -/* INF's architecture has changed. The argument NEWARCH is a - pointer to the new architecture. */ -extern observable - architecture_changed; +/* GDB has instantiated a new architecture, NEWARCH is a pointer to the new + architecture. */ +extern observable new_architecture; /* The thread's ptid has changed. The OLD_PTID parameter specifies the old value, and NEW_PTID specifies the new value. */ diff --git a/gdb/python/py-unwind.c b/gdb/python/py-unwind.c index f8b142dd52c..ee50c51b531 100644 --- a/gdb/python/py-unwind.c +++ b/gdb/python/py-unwind.c @@ -945,7 +945,7 @@ static const registry::key pyuw_gdbarch_data; intermediary. */ static void -pyuw_on_new_gdbarch (inferior *inf, gdbarch *newarch) +pyuw_on_new_gdbarch (gdbarch *newarch) { struct pyuw_gdbarch_data_type *data = pyuw_gdbarch_data.get (newarch); if (data == nullptr) @@ -974,8 +974,7 @@ pyuw_on_new_gdbarch (inferior *inf, gdbarch *newarch) static int CPYCHECKER_NEGATIVE_RESULT_SETS_EXCEPTION gdbpy_initialize_unwind (void) { - gdb::observers::architecture_changed.attach (pyuw_on_new_gdbarch, - "py-unwind"); + gdb::observers::new_architecture.attach (pyuw_on_new_gdbarch, "py-unwind"); if (PyType_Ready (&pending_frame_object_type) < 0) return -1; -- 2.30.2