[patch+7.12] PR gdb/20609 - attach of JIT-debug-enabled inf 7.11.1 regression

[Jan Kratochvil <jan dot kratochvil at redhat dot com>]

Hi,

Regression: gdb --pid $(pidof qemu-system-x86_64) stopped working with gdb 7.11.1
https://sourceware.org/bugzilla/show_bug.cgi?id=20609

It was reported for qemu-system-x86_64 but it happens for any multithreaded
inferior with a JIT debugging hook.

136613ef0c6850427317e57be1b644080ff6decb is the first bad commit
Author: Pedro Alves <palves@redhat.com>
    Fix PR gdb/19828: gdb -p <process from a container>: internal error
Message-ID: <cbdf2e04-4fa8-872a-2a23-08c9c1b26e00@redhat.com>
https://sourceware.org/ml/gdb-patches/2016-05/msg00450.html

jit_breakpoint_re_set() is specific by trying to insert a breakpoint into the
main executable, not into a shared library.  During attachment GDB thinks it
needs to use 'breakpoint always-inserted' from
breakpoints_should_be_inserted_now() as a newly attached thread is
'thread_info->executing' due to 'lwp_info->must_set_ptrace_flags' enabled and
the task not yet stopped.  This did not happen before the 'bad commit' above
which adds tracking of such thread.

GDB then fails to insert the breakpoints to invalid address as PIE executable
gets properly relocated during later phase of attachment.  One can see in the
backtraces below:
#11 in setup_inferior (from_tty=0) at infcmd.c:2663
 -> jit_breakpoint_re_set_internal()
later:
#5  in setup_inferior (from_tty=0) at infcmd.c:2673
 -> svr4_exec_displacement()

One can suppress the initial breakpoint_re_set() call as there will be another
breakpoint_re_set() done from the final post_create_inferior() call in
setup_inferior().

BTW additionally 'threads_executing' cache bool is somehow stale (somewhere is
missing update_threads_executing()).  I was trying to deal with that in my
first/second attempt below but in my final third attempt (attached) I have
left it as it is.

First attempt trying not to falsely require 'breakpoint always-inserted':
  https://people.redhat.com/jkratoch/rhbz1375553-fix1.patch
Reduced first attempt:
  https://people.redhat.com/jkratoch/rhbz1375553-fix2.patch

The third attempt suppresses breakpoint insertion until PIE executable gets
relocated by svr4_exec_displacement().  Attached.

No regressions on {x86_64,x86_64-m32,i686}-fedora26pre-linux-gnu.

OK for check-in for trunk + 7.12?


Jan


#0  jit_breakpoint_re_set_internal (gdbarch=0x25befe0, ps_data=0x23b37e0) at jit.c:1045
#1  in jit_breakpoint_re_set () at jit.c:1408
#2  in breakpoint_re_set () at breakpoint.c:14665
#3  in clear_symtab_users (add_flags=4) at symfile.c:2970
#4  in finish_new_objfile (objfile=0x25b6d10, add_flags=4) at symfile.c:1109
#5  in symbol_file_add_with_addrs (abfd=0x25b4bd0, name=0x25b3970 "/tmp/a.out", add_flags=4, addrs=0x0, flags=0, parent=0x0) at symfile.c:1233
#6  in symbol_file_add_from_bfd (abfd=0x25b4bd0, name=0x25b3970 "/tmp/a.out", add_flags=4, addrs=0x0, flags=0, parent=0x0) at symfile.c:1276
#7  in symbol_file_add (name=0x25b3970 "/tmp/a.out", add_flags=4, addrs=0x0, flags=0) at symfile.c:1290
#8  in symbol_file_add_main_1 (args=0x25b3970 "/tmp/a.out", from_tty=0, flags=0) at symfile.c:1315
#9  in symbol_file_add_main (args=0x25b3970 "/tmp/a.out", from_tty=0) at symfile.c:1306
#10 in exec_file_locate_attach (pid=2502, from_tty=0) at exec.c:235
#11 in setup_inferior (from_tty=0) at infcmd.c:2663
#12 in stop_all_threads () at infrun.c:4630
#13 in stop_waiting (ecs=0x7fffffffd400) at infrun.c:7710
#14 in handle_signal_stop (ecs=0x7fffffffd400) at infrun.c:5765
#15 in handle_inferior_event_1 (ecs=0x7fffffffd400) at infrun.c:5395
#16 in handle_inferior_event (ecs=0x7fffffffd400) at infrun.c:5426
#17 in fetch_inferior_event (client_data=0x0) at infrun.c:3972
#18 in inferior_event_handler (event_type=INF_REG_EVENT, client_data=0x0) at inf-loop.c:44
#19 in handle_target_event (error=0, client_data=0x0) at linux-nat.c:4523
#20 in handle_file_event (file_ptr=0x25ad330, ready_mask=1) at event-loop.c:733
#21 in gdb_wait_for_event (block=0) at event-loop.c:859
#22 in gdb_do_one_event () at event-loop.c:322
#23 in wait_sync_command_done () at top.c:568
#24 in maybe_wait_sync_command_done (was_sync=0) at top.c:587
#25 in catch_command_errors (command=0x745e0c <attach_command(char*, int)>, arg=0x7fffffffdd08 "2502", from_tty=1) at main.c:377
#26 in captured_main (data=0x7fffffffd800) at main.c:1065
#27 in gdb_main (args=0x7fffffffd800) at main.c:1159
#28 in main (argc=10, argv=0x7fffffffd908) at gdb.c:32

#0  svr4_exec_displacement (displacementp=0x7fffffffced0) at solib-svr4.c:2634
#1  in svr4_relocate_main_executable () at solib-svr4.c:3031
#2  in svr4_solib_create_inferior_hook (from_tty=0) at solib-svr4.c:3092
#3  in solib_create_inferior_hook (from_tty=0) at solib.c:1276
#4  in post_create_inferior (target=0x21ee980 <current_target>, from_tty=0) at infcmd.c:445
#5  in setup_inferior (from_tty=0) at infcmd.c:2673
#6  in stop_all_threads () at infrun.c:4630
#7  in stop_waiting (ecs=0x7fffffffd400) at infrun.c:7710
#8  in handle_signal_stop (ecs=0x7fffffffd400) at infrun.c:5765
#9  in handle_inferior_event_1 (ecs=0x7fffffffd400) at infrun.c:5395
#10 in handle_inferior_event (ecs=0x7fffffffd400) at infrun.c:5426
#11 in fetch_inferior_event (client_data=0x0) at infrun.c:3972
#12 in inferior_event_handler (event_type=INF_REG_EVENT, client_data=0x0) at inf-loop.c:44
#13 in handle_target_event (error=0, client_data=0x0) at linux-nat.c:4523
#14 in handle_file_event (file_ptr=0x25ad330, ready_mask=1) at event-loop.c:733
#15 in gdb_wait_for_event (block=0) at event-loop.c:859
#16 in gdb_do_one_event () at event-loop.c:322
#17 in wait_sync_command_done () at top.c:568
#18 in maybe_wait_sync_command_done (was_sync=0) at top.c:587
#19 in catch_command_errors (command=0x745e0c <attach_command(char*, int)>, arg=0x7fffffffdd08 "2502", from_tty=1) at main.c:377
#20 in captured_main (data=0x7fffffffd800) at main.c:1065
#21 in gdb_main (args=0x7fffffffd800) at main.c:1159
#22 in main (argc=10, argv=0x7fffffffd908) at gdb.c:32

gdb/ChangeLog
2016-09-27  Jan Kratochvil  <jan.kratochvil@redhat.com>

	PR gdb/20609 - attach of JIT-debug-enabled inf 7.11.1 regression
	* exec.c (exec_file_locate_attach): Add parameter defer_bp_reset.
	Use it.
	* gdbcore.h (exec_file_locate_attach): Add parameter defer_bp_reset.
	* infcmd.c (setup_inferior): Update caller.
	* remote.c (remote_add_inferior): Likewise.

gdb/testsuite/ChangeLog
2016-09-27  Jan Kratochvil  <jan.kratochvil@redhat.com>

	PR gdb/20609 - attach of JIT-debug-enabled inf 7.11.1 regression
	* gdb.base/jit-attach-pie.c: New file.
	* gdb.base/jit-attach-pie.exp: New file.

diff --git a/gdb/exec.c b/gdb/exec.c
index 00c31d3..f16cb4b 100644
--- a/gdb/exec.c
+++ b/gdb/exec.c
@@ -157,7 +157,7 @@ exception_print_same (struct gdb_exception e1, struct gdb_exception e2)
 /* See gdbcore.h.  */
 
 void
-exec_file_locate_attach (int pid, int from_tty)
+exec_file_locate_attach (int pid, int defer_bp_reset, int from_tty)
 {
   char *exec_file, *full_exec_path = NULL;
   struct cleanup *old_chain;
@@ -232,6 +232,8 @@ exec_file_locate_attach (int pid, int from_tty)
 
   TRY
     {
+      if (defer_bp_reset)
+	current_inferior ()->symfile_flags |= SYMFILE_DEFER_BP_RESET;
       symbol_file_add_main (full_exec_path, from_tty);
     }
   CATCH (err, RETURN_MASK_ERROR)
@@ -240,6 +242,7 @@ exec_file_locate_attach (int pid, int from_tty)
 	warning ("%s", err.message);
     }
   END_CATCH
+  current_inferior ()->symfile_flags &= ~SYMFILE_DEFER_BP_RESET;
 
   do_cleanups (old_chain);
 }
diff --git a/gdb/gdbcore.h b/gdb/gdbcore.h
index 8b101bc..6aa9afa 100644
--- a/gdb/gdbcore.h
+++ b/gdb/gdbcore.h
@@ -154,9 +154,10 @@ extern void exec_file_attach (const char *filename, int from_tty);
 /* If the filename of the main executable is unknown, attempt to
    determine it.  If a filename is determined, proceed as though
    it was just specified with the "file" command.  Do nothing if
-   the filename of the main executable is already known.  */
+   the filename of the main executable is already known.
+   DEFER_BP_RESET uses SYMFILE_DEFER_BP_RESET for the main symbol file.  */
 
-extern void exec_file_locate_attach (int pid, int from_tty);
+extern void exec_file_locate_attach (int pid, int defer_bp_reset, int from_tty);
 
 extern void exec_file_clear (int from_tty);
 
diff --git a/gdb/infcmd.c b/gdb/infcmd.c
index 44a1fd1..8e34b7e 100644
--- a/gdb/infcmd.c
+++ b/gdb/infcmd.c
@@ -2660,7 +2660,7 @@ setup_inferior (int from_tty)
   /* If no exec file is yet known, try to determine it from the
      process itself.  */
   if (get_exec_file (0) == NULL)
-    exec_file_locate_attach (ptid_get_pid (inferior_ptid), from_tty);
+    exec_file_locate_attach (ptid_get_pid (inferior_ptid), 1, from_tty);
   else
     {
       reopen_exec_file ();
diff --git a/gdb/remote.c b/gdb/remote.c
index 910ac81..b460bb1 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -1799,7 +1799,7 @@ remote_add_inferior (int fake_pid_p, int pid, int attached,
   /* If no main executable is currently open then attempt to
      open the file that was executed to create this inferior.  */
   if (try_open_exec && get_exec_file (0) == NULL)
-    exec_file_locate_attach (pid, 1);
+    exec_file_locate_attach (pid, 0, 1);
 
   return inf;
 }
diff --git a/gdb/testsuite/gdb.base/jit-attach-pie.c b/gdb/testsuite/gdb.base/jit-attach-pie.c
new file mode 100644
index 0000000..5080bde
--- /dev/null
+++ b/gdb/testsuite/gdb.base/jit-attach-pie.c
@@ -0,0 +1,61 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2016 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <unistd.h>
+#include <stdint.h>
+#include <pthread.h>
+
+struct jit_code_entry
+{
+  struct jit_code_entry *next_entry;
+  struct jit_code_entry *prev_entry;
+  const char *symfile_addr;
+  uint64_t symfile_size;
+};
+
+struct jit_descriptor
+{
+  uint32_t version;
+  /* This type should be jit_actions_t, but we use uint32_t
+     to be explicit about the bitwidth.  */
+  uint32_t action_flag;
+  struct jit_code_entry *relevant_entry;
+  struct jit_code_entry *first_entry;
+};
+
+struct jit_descriptor __jit_debug_descriptor = { 1, 0, 0, 0 };
+
+void __jit_debug_register_code()
+{
+}
+
+static void *
+thread_proc (void *arg)
+{
+  sleep (60);
+  return arg;
+}
+
+int
+main (void)
+{
+  pthread_t thread;
+
+  pthread_create (&thread, NULL, thread_proc, 0);
+  pthread_join (thread, NULL);
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.base/jit-attach-pie.exp b/gdb/testsuite/gdb.base/jit-attach-pie.exp
new file mode 100644
index 0000000..2c25733
--- /dev/null
+++ b/gdb/testsuite/gdb.base/jit-attach-pie.exp
@@ -0,0 +1,48 @@
+# Copyright (C) 2016 Free Software Foundation, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+if {![can_spawn_for_attach]} {
+    return 0
+}
+
+standard_testfile .c
+set executable ${testfile}
+
+if { [build_executable ${testfile}.exp $executable $srcfile \
+			  [list debug pthreads "additional_flags=-fPIE -pie"]] } {
+    return -1
+}
+
+# Start the program running and then wait for a bit, to be sure
+# that it can be attached to.
+
+set test_spawn_id [spawn_wait_for_attach $binfile]
+set testpid [spawn_id_get_pid $test_spawn_id]
+
+# gdb_load ("file" command) must not be executed for the bug reproducibility.
+# That includes prepare_for_testing or clean_restart.
+gdb_start
+
+set test "attach"
+gdb_test_multiple "attach $testpid" $test {
+    -re "Attaching to process $testpid\r\n.*Cannot insert breakpoint .*\r\n$gdb_prompt $" {
+	fail $test
+    }
+    -re "Attaching to process $testpid\r\n.*\r\n$gdb_prompt $" {
+	pass $test
+    }
+}
+
+kill_wait_spawned_process $test_spawn_id