From 1bb7c059779218d2db7dc4668f998617603e86df Mon Sep 17 00:00:00 2001 From: Simon Marchi Date: Tue, 5 Sep 2017 16:45:10 +0200 Subject: [PATCH] Read stop_pc after updating the gdbarch when exec'ing When an inferior execs and changes architecture (e.g. 64 bits to 32 bits), the gdbarch associated to the inferior is updated by the follow_exec call in handle_inferior_event_1. We should avoid doing any register read before that point, because the registers sent by the remote side will be those of the new architecture, but we would interpret them using the old architecture. We do just that by setting stop_pc during this window, which obviously requires reading the registers. This results in gdb.multi/multi-arch-exec.exp failing, GDB outputting the following error: Truncated register 50 in remote 'g' packet This patch fixes that by postponing the setting of stop_pc to after we've updated the inferior gdbarch. This bug was hiding another problem, and as such introduces some failures in gdb.base/foll-exec-mode.exp. The following patch takes care of that. gdb/ChangeLog: * infrun.c (handle_inferior_event_1): When exec'ing, read stop_pc after follow_exec. --- gdb/ChangeLog | 5 +++++ gdb/infrun.c | 4 ++-- 2 files changed, 7 insertions(+), 2 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 27922083662..2fe8ab103f7 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,8 @@ +2017-09-05 Simon Marchi + + * infrun.c (handle_inferior_event_1): When exec'ing, read + stop_pc after follow_exec. + 2017-09-05 Simon Marchi * remote.c (process_g_packet): Update error message. diff --git a/gdb/infrun.c b/gdb/infrun.c index 7568a5ef478..1c6b186e4d5 100644 --- a/gdb/infrun.c +++ b/gdb/infrun.c @@ -5309,8 +5309,6 @@ Cannot fill $_exitsignal with the correct signal number.\n")); if (!ptid_equal (ecs->ptid, inferior_ptid)) context_switch (ecs->ptid); - stop_pc = regcache_read_pc (get_thread_regcache (ecs->ptid)); - /* Do whatever is necessary to the parent branch of the vfork. */ handle_vfork_child_exec_or_exit (1); @@ -5319,6 +5317,8 @@ Cannot fill $_exitsignal with the correct signal number.\n")); stop. */ follow_exec (inferior_ptid, ecs->ws.value.execd_pathname); + stop_pc = regcache_read_pc (get_thread_regcache (ecs->ptid)); + /* In follow_exec we may have deleted the original thread and created a new one. Make sure that the event thread is the execd thread for that case (this is a nop otherwise). */ -- 2.30.2