From f79b145de30d6eaafc1f3f5b2aa913519fcd311f Mon Sep 17 00:00:00 2001 From: Yao Qi Date: Fri, 17 Jun 2016 10:25:12 +0100 Subject: [PATCH] Switch to current thread in finish_step_over This patch adds some sanity check that reinsert breakpoints must be there when doing step-over on software single step target. The check triggers an assert when running forking-threads-plus-breakpoint.exp on arm-linux target, gdb/gdbserver/linux-low.c:4714: A problem internal to GDBserver has been detected.^M int finish_step_over(lwp_info*): Assertion `has_reinsert_breakpoints ()' failed. the error happens when GDBserver has already resumed a thread of process A for step-over (and wait for it hitting reinsert breakpoint), but receives detach request for process B from GDB, which is shown in the backtrace below, (gdb) bt #2 0x000228aa in finish_step_over (lwp=0x12bbd98) at /home/yao/SourceCode/gnu/gdb/git/gdb/gdbserver/linux-low.c:4703 #3 0x00025a50 in finish_step_over (lwp=0x12bbd98) at /home/yao/SourceCode/gnu/gdb/git/gdb/gdbserver/linux-low.c:4749 #4 complete_ongoing_step_over () at /home/yao/SourceCode/gnu/gdb/git/gdb/gdbserver/linux-low.c:4760 #5 linux_detach (pid=25228) at /home/yao/SourceCode/gnu/gdb/git/gdb/gdbserver/linux-low.c:1503 #6 0x00012bae in process_serial_event () at /home/yao/SourceCode/gnu/gdb/git/gdb/gdbserver/server.c:3974 #7 handle_serial_event (err=, client_data=) at /home/yao/SourceCode/gnu/gdb/git/gdb/gdbserver/server.c:4347 #8 0x00016d68 in handle_file_event (event_file_desc=) at /home/yao/SourceCode/gnu/gdb/git/gdb/gdbserver/event-loop.c:429 #9 0x000173ea in process_event () at /home/yao/SourceCode/gnu/gdb/git/gdb/gdbserver/event-loop.c:184 #10 start_event_loop () at /home/yao/SourceCode/gnu/gdb/git/gdb/gdbserver/event-loop.c:547 #11 0x0000aa2c in captured_main (argv=, argc=) at /home/yao/SourceCode/gnu/gdb/git/gdb/gdbserver/server.c:3719 #12 main (argc=, argv=) at /home/yao/SourceCode/gnu/gdb/git/gdb/gdbserver/server.c:3804 the sanity check tries to find the reinsert breakpoint from process B, but nothing is found. It is wrong, we need to search in process A, since we started step-over of a thread of process A. (gdb) p lwp->thread->entry.id $3 = {pid = 25120, lwp = 25131, tid = 0} (gdb) p current_thread->entry.id $4 = {pid = 25228, lwp = 25228, tid = 0} This patch switched current_thread to the thread we are doing step-over in finish_step_over. gdb/gdbserver: 2016-06-17 Yao Qi * linux-low.c (maybe_hw_step): New function. (linux_resume_one_lwp_throw): Call maybe_hw_step. (finish_step_over): Switch current_thread to lwp temporarily, and assert has_reinsert_breakpoints returns true. (proceed_one_lwp): Call maybe_hw_step. * mem-break.c (has_reinsert_breakpoints): New function. * mem-break.h (has_reinsert_breakpoints): Declare. --- gdb/gdbserver/ChangeLog | 10 ++++++++++ gdb/gdbserver/linux-low.c | 35 +++++++++++++++++++++++++++++++---- gdb/gdbserver/mem-break.c | 22 ++++++++++++++++++++++ gdb/gdbserver/mem-break.h | 4 ++++ 4 files changed, 67 insertions(+), 4 deletions(-) diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog index 079507ae306..70f64fff19b 100644 --- a/gdb/gdbserver/ChangeLog +++ b/gdb/gdbserver/ChangeLog @@ -1,3 +1,13 @@ +2016-06-17 Yao Qi + + * linux-low.c (maybe_hw_step): New function. + (linux_resume_one_lwp_throw): Call maybe_hw_step. + (finish_step_over): Switch current_thread to lwp temporarily, + and assert has_reinsert_breakpoints returns true. + (proceed_one_lwp): Call maybe_hw_step. + * mem-break.c (has_reinsert_breakpoints): New function. + * mem-break.h (has_reinsert_breakpoints): Declare. + 2016-06-02 Jon Turney * win32-low.c (win32_create_inferior): Add pointer casts for C++. diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c index 81134b0c525..77c296ca2a1 100644 --- a/gdb/gdbserver/linux-low.c +++ b/gdb/gdbserver/linux-low.c @@ -2495,6 +2495,24 @@ linux_low_filter_event (int lwpid, int wstat) return child; } +/* Return true if THREAD is doing hardware single step. */ + +static int +maybe_hw_step (struct thread_info *thread) +{ + if (can_hardware_single_step ()) + return 1; + else + { + struct process_info *proc = get_thread_process (thread); + + /* GDBserver must insert reinsert breakpoint for software + single step. */ + gdb_assert (has_reinsert_breakpoints (proc)); + return 0; + } +} + /* Resume LWPs that are currently stopped without any pending status to report, but are resumed from the core's perspective. */ @@ -4215,9 +4233,9 @@ linux_resume_one_lwp_throw (struct lwp_info *lwp, fprintf (stderr, "BAD - reinserting and suspended(%d).\n", lwp->suspended); } - - step = 1; } + + step = maybe_hw_step (thread); } if (fast_tp_collecting == 1) @@ -4689,9 +4707,13 @@ finish_step_over (struct lwp_info *lwp) { if (lwp->bp_reinsert != 0) { + struct thread_info *saved_thread = current_thread; + if (debug_threads) debug_printf ("Finished step over.\n"); + current_thread = get_lwp_thread (lwp); + /* Reinsert any breakpoint at LWP->BP_REINSERT. Note that there may be no breakpoint to reinsert there by now. */ reinsert_breakpoints_at (lwp->bp_reinsert); @@ -4705,9 +4727,13 @@ finish_step_over (struct lwp_info *lwp) because we were stepping over a breakpoint, and we hold all threads but LWP stopped while doing that. */ if (!can_hardware_single_step ()) - delete_reinsert_breakpoints (); + { + gdb_assert (has_reinsert_breakpoints (current_process ())); + delete_reinsert_breakpoints (); + } step_over_bkpt = null_ptid; + current_thread = saved_thread; return 1; } else @@ -5029,7 +5055,8 @@ proceed_one_lwp (struct inferior_list_entry *entry, void *except) if (debug_threads) debug_printf (" stepping LWP %ld, reinsert set\n", lwpid_of (thread)); - step = 1; + + step = maybe_hw_step (thread); } else step = 0; diff --git a/gdb/gdbserver/mem-break.c b/gdb/gdbserver/mem-break.c index 363d7ca5628..3313459b9a2 100644 --- a/gdb/gdbserver/mem-break.c +++ b/gdb/gdbserver/mem-break.c @@ -1553,6 +1553,28 @@ reinsert_breakpoints_at (CORE_ADDR pc) } } +int +has_reinsert_breakpoints (struct process_info *proc) +{ + struct breakpoint *bp, **bp_link; + + bp = proc->breakpoints; + bp_link = &proc->breakpoints; + + while (bp) + { + if (bp->type == reinsert_breakpoint) + return 1; + else + { + bp_link = &bp->next; + bp = *bp_link; + } + } + + return 0; +} + void reinsert_all_breakpoints (void) { diff --git a/gdb/gdbserver/mem-break.h b/gdb/gdbserver/mem-break.h index 4d9a76c23d4..b84dc1e2415 100644 --- a/gdb/gdbserver/mem-break.h +++ b/gdb/gdbserver/mem-break.h @@ -163,6 +163,10 @@ void delete_reinsert_breakpoints (void); void reinsert_breakpoints_at (CORE_ADDR where); +/* Process PROC has reinsert breakpoints or not. */ + +int has_reinsert_breakpoints (struct process_info *proc); + /* Uninsert breakpoints at WHERE (and change their status to uninserted). This still leaves the breakpoints in the table. */