From 2e7b624b851c34f6bc2ab75fcbc94db75f72eb3a Mon Sep 17 00:00:00 2001 From: Yao Qi Date: Fri, 17 Jun 2016 10:25:13 +0100 Subject: [PATCH] Handle reinsert breakpoints for vforked child When a thread is doing step-over with reinsert breakpoint, and the instruction executed is a syscall doing vfork, both parent and child share the memory, so the reinsert breakpoint in the space is visible to both of them. Also, removing the reinsert breakpoints from the child will effectively remove them from the parent. We should carefully manipulate reinsert breakpoints for both processes. What we are doing here is that - uninsert reinsert breakpoints from the parent before cloning the breakpoint list. We use "uninsert" instead of "remove", because we need to "reinsert" them back after vfork is done. In fact, "uninsert" removes them from both child and parent process space. - reinsert breakpoints in parent process are still copied to child's breakpoint list, - remove them from child's breakpoint list as what we did for fork, at this point, reinsert breakpoints are removed from the child and the parent, but they are still tracked by the parent's breakpoint list, - once vfork is done, "reinsert" them back to the parent, gdb/gdbserver: 2016-06-17 Yao Qi * linux-low.c (handle_extended_wait): Call uninsert_reinsert_breakpoints for the parent process. Remove reinsert breakpoints from the child process. Reinsert them to the parent process when vfork is done. * mem-break.c (uninsert_reinsert_breakpoints): New function. (reinsert_reinsert_breakpoints): New function. * mem-break.h (uninsert_reinsert_breakpoints): Declare (reinsert_reinsert_breakpoints): Declare. --- gdb/gdbserver/ChangeLog | 11 +++++++++++ gdb/gdbserver/linux-low.c | 38 +++++++++++++++++++++++++++++++++----- gdb/gdbserver/mem-break.c | 38 ++++++++++++++++++++++++++++++++++++++ gdb/gdbserver/mem-break.h | 9 +++++++++ 4 files changed, 91 insertions(+), 5 deletions(-) diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog index 734d70dd656..6983e19a704 100644 --- a/gdb/gdbserver/ChangeLog +++ b/gdb/gdbserver/ChangeLog @@ -1,3 +1,14 @@ +2016-06-17 Yao Qi + + * linux-low.c (handle_extended_wait): Call + uninsert_reinsert_breakpoints for the parent process. Remove + reinsert breakpoints from the child process. Reinsert them to + the parent process when vfork is done. + * mem-break.c (uninsert_reinsert_breakpoints): New function. + (reinsert_reinsert_breakpoints): New function. + * mem-break.h (uninsert_reinsert_breakpoints): Declare + (reinsert_reinsert_breakpoints): Declare. + 2016-06-17 Yao Qi * linux-low.c (handle_extended_wait): If the parent is doing diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c index 3f2d08eea5a..dd92e7814af 100644 --- a/gdb/gdbserver/linux-low.c +++ b/gdb/gdbserver/linux-low.c @@ -543,6 +543,22 @@ handle_extended_wait (struct lwp_info **orig_event_lwp, int wstat) parent_proc = get_thread_process (event_thr); child_proc->attached = parent_proc->attached; + + if (event_lwp->bp_reinsert != 0 + && can_software_single_step () + && event == PTRACE_EVENT_VFORK) + { + struct thread_info *saved_thread = current_thread; + + current_thread = event_thr; + /* If we leave reinsert breakpoints there, child will + hit it, so uninsert reinsert breakpoints from parent + (and child). Once vfork child is done, reinsert + them back to parent. */ + uninsert_reinsert_breakpoints (); + current_thread = saved_thread; + } + clone_all_breakpoints (&child_proc->breakpoints, &child_proc->raw_breakpoints, parent_proc->breakpoints); @@ -570,12 +586,12 @@ handle_extended_wait (struct lwp_info **orig_event_lwp, int wstat) event_lwp->status_pending = wstat; /* If the parent thread is doing step-over with reinsert - breakpoints, the reinsert breakpoints are still in forked - child's process space and cloned to its breakpoint list - from the parent's. Remove them from the child process. */ + breakpoints, the list of reinsert breakpoints are cloned + from the parent's. Remove them from the child process. + In case of vfork, we'll reinsert them back once vforked + child is done. */ if (event_lwp->bp_reinsert != 0 - && can_software_single_step () - && event == PTRACE_EVENT_FORK) + && can_software_single_step ()) { struct thread_info *saved_thread = current_thread; @@ -639,6 +655,18 @@ handle_extended_wait (struct lwp_info **orig_event_lwp, int wstat) { event_lwp->waitstatus.kind = TARGET_WAITKIND_VFORK_DONE; + if (event_lwp->bp_reinsert != 0 && can_software_single_step ()) + { + struct thread_info *saved_thread = current_thread; + struct process_info *proc = get_thread_process (event_thr); + + current_thread = event_thr; + reinsert_reinsert_breakpoints (); + current_thread = saved_thread; + + gdb_assert (has_reinsert_breakpoints (proc)); + } + /* Report the event. */ return 0; } diff --git a/gdb/gdbserver/mem-break.c b/gdb/gdbserver/mem-break.c index c27e803027c..5c73326ebb5 100644 --- a/gdb/gdbserver/mem-break.c +++ b/gdb/gdbserver/mem-break.c @@ -1509,6 +1509,26 @@ uninsert_all_breakpoints (void) uninsert_raw_breakpoint (bp); } +void +uninsert_reinsert_breakpoints (void) +{ + struct process_info *proc = current_process (); + struct breakpoint *bp; + + for (bp = proc->breakpoints; bp != NULL; bp = bp->next) + { + if (bp->type == reinsert_breakpoint) + { + gdb_assert (bp->raw->inserted > 0); + + /* Only uninsert the raw breakpoint if it only belongs to a + reinsert breakpoint. */ + if (bp->raw->refcount == 1) + uninsert_raw_breakpoint (bp->raw); + } + } +} + static void reinsert_raw_breakpoint (struct raw_breakpoint *bp) { @@ -1588,6 +1608,24 @@ reinsert_all_breakpoints (void) reinsert_raw_breakpoint (bp); } +void +reinsert_reinsert_breakpoints (void) +{ + struct process_info *proc = current_process (); + struct breakpoint *bp; + + for (bp = proc->breakpoints; bp != NULL; bp = bp->next) + { + if (bp->type == reinsert_breakpoint) + { + gdb_assert (bp->raw->inserted > 0); + + if (bp->raw->refcount == 1) + reinsert_raw_breakpoint (bp->raw); + } + } +} + void check_breakpoints (CORE_ADDR stop_pc) { diff --git a/gdb/gdbserver/mem-break.h b/gdb/gdbserver/mem-break.h index b84dc1e2415..6a06c0c0f7c 100644 --- a/gdb/gdbserver/mem-break.h +++ b/gdb/gdbserver/mem-break.h @@ -158,6 +158,15 @@ void set_reinsert_breakpoint (CORE_ADDR stop_at); void delete_reinsert_breakpoints (void); +/* Reinsert all reinsert breakpoints of the current process. */ + +void reinsert_reinsert_breakpoints (void); + +/* Uninsert all reinsert breakpoints of the current process. This + still leaves the reinsert breakpoints in the table. */ + +void uninsert_reinsert_breakpoints (void); + /* Reinsert breakpoints at WHERE (and change their status to inserted). */ -- 2.30.2