[PATCH 04/18] gdbserver crash running gdb.threads/non-ldr-exc-1.exp

Pedro Alves
2015-10-14T15:36:39Z

This fixes a gdbserver crash when running
gdb.threads/non-ldr-exc-1.exp with "maint set target-non-stop on".
The problem is that qSymbol is called when gdbserver has
current_thread == NULL.

gdb/gdbserver/ChangeLog:
2015-10-14 Pedro Alves <palves@redhat.com>

* gdbthread.h (find_any_thread_of_pid): Declare.
* inferiors.c (thread_of_pid, find_any_thread_of_pid): New
functions.
* server.c (handle_query): If current_thread is NULL, look for
another thread of the selected process.
---
gdb/gdbserver/gdbthread.h | 4 ++++
gdb/gdbserver/inferiors.c | 23 +++++++++++++++++++++++
gdb/gdbserver/server.c | 23 +++++++++++++++++++++++
3 files changed, 50 insertions(+)

diff --git a/gdb/gdbserver/gdbthread.h b/gdb/gdbserver/gdbthread.h
index d6959f4..0510419 100644
--- a/gdb/gdbserver/gdbthread.h
+++ b/gdb/gdbserver/gdbthread.h
@@ -80,6 +80,10 @@ struct thread_info *get_first_thread (void);

struct thread_info *find_thread_ptid (ptid_t ptid);

+/* Find any thread of the PID process. Returns NULL if none is
+ found. */
+struct thread_info *find_any_thread_of_pid (int pid);
+
/* Get current thread ID (Linux task ID). */
#define current_ptid (current_thread->entry.id)

diff --git a/gdb/gdbserver/inferiors.c b/gdb/gdbserver/inferiors.c
index 21f45fa..84f5b7c 100644
--- a/gdb/gdbserver/inferiors.c
+++ b/gdb/gdbserver/inferiors.c
@@ -141,6 +141,29 @@ find_thread_ptid (ptid_t ptid)
return (struct thread_info *) find_inferior_id (&all_threads, ptid);
}

+/* Helper for find_any_thread_of_pid. Returns true if a thread
+ matches a PID. */
+
+static int
+thread_of_pid (struct inferior_list_entry *entry, void *pid_p)
+{
+ int pid = *(int *) pid_p;
+
+ return (ptid_get_pid (entry->id) == pid);
+}
+
+/* See gdbthread.h. */
+
+struct thread_info *
+find_any_thread_of_pid (int pid)
+{
+ struct inferior_list_entry *entry;
+
+ entry = find_inferior (&all_threads, thread_of_pid, &pid);
+
+ return (struct thread_info *) entry;
+}
+
ptid_t
gdb_id_to_thread_id (ptid_t gdb_id)
{
diff --git a/gdb/gdbserver/server.c b/gdb/gdbserver/server.c
index e25b7c7..ec52f84 100644
--- a/gdb/gdbserver/server.c
+++ b/gdb/gdbserver/server.c
@@ -1971,6 +1971,27 @@ handle_query (char *own_buf, int packet_len, int *new_packet_len_p)

if (strcmp ("qSymbol::", own_buf) == 0)
{
+ struct thread_info *save_thread = current_thread;
+
+ /* For qSymbol, GDB only changes the current thread if the
+ previous current thread was of a different process. So if
+ the previous thread is gone, we need to pick another one of
+ the same process. This can happen e.g., if we followed an
+ exec in a non-leader thread. */
+ if (current_thread == NULL)
+ {
+ current_thread = find_any_thread_of_pid (ptid_get_pid (general_thread));
+
+ /* Just in case, if we didn't find a thread, then bail out
+ instead of crashing. */
+ if (current_thread == NULL)
+ {
+ write_enn (own_buf);
+ current_thread = save_thread;
+ return;
+ }
+ }
+
/* GDB is suggesting new symbols have been loaded. This may
mean a new shared library has been detected as loaded, so
take the opportunity to check if breakpoints we think are
@@ -1989,6 +2010,8 @@ handle_query (char *own_buf, int packet_len, int *new_packet_len_p)
if (current_thread != NULL && the_target->look_up_symbols != NULL)
(*the_target->look_up_symbols) ();

+ current_thread = save_thread;
+
strcpy (own_buf, "OK");
return;
}
--
1.9.3