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displaced_step_finish: Don't fetch the regcache of exited threads

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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
This commit is contained in:
Pedro Alves 2023-12-01 13:31:00 +00:00
parent d0b5914979
commit 249d081287
2 changed files with 14 additions and 7 deletions
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19
gdb/infrun.c
View file

@ -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,

2
gdb/regcache.c
View file

@ -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);
}