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From: Pedro Alves <palves@sourceware.org> To: gdb-cvs@sourceware.org Subject: [binutils-gdb] displaced_step_finish: Don't fetch the regcache of exited threads Date: Wed, 20 Dec 2023 21:21:43 +0000 (GMT) [thread overview] Message-ID: <20231220212143.3C8823858CD1@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=249d08128787e4e0a977079aa09516d73f196f77 commit 249d08128787e4e0a977079aa09516d73f196f77 Author: Pedro Alves <pedro@palves.net> Date: Fri Dec 1 13:31:00 2023 +0000 displaced_step_finish: Don't fetch the regcache of exited threads displaced_step_finish can be called with event_status.kind == TARGET_WAITKIND_THREAD_EXITED, and in that case it is not possible to get at the already-exited thread's registers. This patch moves the get_thread_regcache calls to branches that actually need it, where we know the thread is still alive. It also adds an assertion to get_thread_regcache, to help catching these broken cases sooner. Approved-By: Simon Marchi <simon.marchi@efficios.com> Change-Id: I63b5eacb3e02a538fc5087c270d8025adfda88c3 Diff: --- gdb/infrun.c | 19 ++++++++++++------- gdb/regcache.c | 2 ++ 2 files changed, 14 insertions(+), 7 deletions(-) diff --git a/gdb/infrun.c b/gdb/infrun.c index 6dc0a2bb9a5..76693a30611 100644 --- a/gdb/infrun.c +++ b/gdb/infrun.c @@ -2021,8 +2021,6 @@ displaced_step_finish (thread_info *event_thread, const target_waitstatus &event_status) { /* Check whether the parent is displaced stepping. */ - struct regcache *regcache = get_thread_regcache (event_thread); - struct gdbarch *gdbarch = regcache->arch (); inferior *parent_inf = event_thread->inf; /* If this was a fork/vfork/clone, this event indicates that the @@ -2040,10 +2038,15 @@ displaced_step_finish (thread_info *event_thread, gdbarch_displaced_step_restore_all_in_ptid. This is not enforced during gdbarch validation to support architectures which support displaced stepping but not forks. */ - if (event_status.kind () == TARGET_WAITKIND_FORKED - && gdbarch_supports_displaced_stepping (gdbarch)) - gdbarch_displaced_step_restore_all_in_ptid - (gdbarch, parent_inf, event_status.child_ptid ()); + if (event_status.kind () == TARGET_WAITKIND_FORKED) + { + struct regcache *parent_regcache = get_thread_regcache (event_thread); + struct gdbarch *gdbarch = parent_regcache->arch (); + + if (gdbarch_supports_displaced_stepping (gdbarch)) + gdbarch_displaced_step_restore_all_in_ptid + (gdbarch, parent_inf, event_status.child_ptid ()); + } displaced_step_thread_state *displaced = &event_thread->displaced_step_state; @@ -2082,11 +2085,13 @@ displaced_step_finish (thread_info *event_thread, child hasn't been added to the inferior list yet at this point. */ + struct regcache *parent_regcache = get_thread_regcache (event_thread); + struct gdbarch *gdbarch = parent_regcache->arch (); struct regcache *child_regcache = get_thread_arch_regcache (parent_inf, event_status.child_ptid (), gdbarch); /* Read PC value of parent. */ - CORE_ADDR parent_pc = regcache_read_pc (regcache); + CORE_ADDR parent_pc = regcache_read_pc (parent_regcache); displaced_debug_printf ("write child pc from %s to %s", paddress (gdbarch, diff --git a/gdb/regcache.c b/gdb/regcache.c index 6140a05f02b..1217fe7240b 100644 --- a/gdb/regcache.c +++ b/gdb/regcache.c @@ -430,6 +430,8 @@ get_thread_regcache (process_stratum_target *target, ptid_t ptid) struct regcache * get_thread_regcache (thread_info *thread) { + gdb_assert (thread->state != THREAD_EXITED); + return get_thread_regcache (thread->inf->process_target (), thread->ptid); }
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