[RFC 2/3] use reinsert breakpoint for vCont;s

Yao Qi
2016-05-06T10:32:44Z

This patch teaches GDBserver to handle vCont;s using software single
step. That is, if the resume request is resume_step, insert reinsert
breakpoint at the next pc address, and resume the thread. These
reinsert breakpoints are removed in linux_wait_1, which I am not sure.

gdb/gdbserver:

2016-04-26 Yao Qi <yao.qi@linaro.org>

* linux-low.c (linux_wait_1): Delete reinsert breakpoints in
some cases.
(linux_resume_one_thread): Call single_step if lwp->resume->kind
is resume_step.
(proceed_one_lwp): Call single_step.
---
gdb/gdbserver/linux-low.c | 33 ++++++++++++++++++++++++++++++---
gdb/gdbserver/mem-break.c | 20 +++++++++++++++++++-
gdb/gdbserver/mem-break.h | 7 ++++++-
3 files changed, 55 insertions(+), 5 deletions(-)

diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c
index e539e34..2a9a1ad 100644
--- a/gdb/gdbserver/linux-low.c
+++ b/gdb/gdbserver/linux-low.c
@@ -3270,12 +3270,34 @@ linux_wait_1 (ptid_t ptid,
if (debug_threads)
debug_printf ("Hit a gdbserver breakpoint.\n");
}
+
+ if (!step_over_finished && !can_hardware_single_step ())
+ {
+ /* If the thread resumed by resume_step hits the reinsert
+ breakpoint, delete the reinsert breakpoint for it. */
+ if (current_thread->last_resume_kind == resume_step)
+ delete_reinsert_breakpoints (current_thread);
+ else
+ {
+ /* If the thread resumed by other kind, like
+ resume_continue, hits the breakpoint (either
+ reinsert breakpoint or GDB breakpoint), delete
+ all reinsert breakpoints if it hits non-reinsert
+ breakpoints, otherwise, leave reinsert breakpoint there
+ and step over it. */
+ if (non_reinsert_breakpoint_inserted_here (event_child->stop_pc))
+ delete_reinsert_breakpoints (NULL);
+ }
+ }
}
else
{
/* We have some other signal, possibly a step-over dance was in
progress, and it should be cancelled too. */
step_over_finished = finish_step_over (event_child);
+
+ if (!step_over_finished && !can_hardware_single_step ())
+ delete_reinsert_breakpoints (NULL);
}

/* We have all the data we need. Either report the event to GDB, or
@@ -3568,6 +3590,8 @@ linux_wait_1 (ptid_t ptid,

/* Alright, we're going to report a stop. */

+ delete_reinsert_breakpoints (NULL);
+
if (!stabilizing_threads)
{
/* In all-stop, stop all threads. */
@@ -4765,7 +4789,6 @@ linux_resume_one_thread (struct inferior_list_entry *entry, void *arg)
{
struct thread_info *thread = (struct thread_info *) entry;
struct lwp_info *lwp = get_thread_lwp (thread);
- int step;
int leave_all_stopped = * (int *) arg;
int leave_pending;

@@ -4834,10 +4857,14 @@ linux_resume_one_thread (struct inferior_list_entry *entry, void *arg)

if (!leave_pending)
{
+ int step = 0;
+
if (debug_threads)
debug_printf ("resuming LWP %ld\n", lwpid_of (thread));

- step = (lwp->resume->kind == resume_step);
+ if (lwp->resume->kind == resume_step)
+ step = single_step (lwp);
+
linux_resume_one_lwp (lwp, step, lwp->resume->sig, NULL);
}
else
@@ -5022,7 +5049,7 @@ proceed_one_lwp (struct inferior_list_entry *entry, void *except)
if (debug_threads)
debug_printf (" stepping LWP %ld, client wants it stepping\n",
lwpid_of (thread));
- step = 1;
+ step = single_step (lwp);
}
else if (lwp->bp_reinsert != 0)
{
diff --git a/gdb/gdbserver/mem-break.c b/gdb/gdbserver/mem-break.c
index 197d7a1..051325a 100644
--- a/gdb/gdbserver/mem-break.c
+++ b/gdb/gdbserver/mem-break.c
@@ -1431,7 +1431,8 @@ delete_reinsert_breakpoints (struct thread_info *thread)

while (bp)
{
- if (bp->type == reinsert_breakpoint && bp->thread == thread)
+ if (bp->type == reinsert_breakpoint
+ && (bp->thread == thread || thread == NULL))
{
*bp_link = bp->next;
release_breakpoint (proc, bp);
@@ -1692,6 +1693,23 @@ reinsert_breakpoint_inserted_here (CORE_ADDR addr)
return 0;
}

+/* See mem-break.h. */
+
+int
+non_reinsert_breakpoint_inserted_here (CORE_ADDR addr)
+{
+ struct process_info *proc = current_process ();
+ struct breakpoint *bp;
+
+ for (bp = proc->breakpoints; bp != NULL; bp = bp->next)
+ if (bp->type != reinsert_breakpoint
+ && bp->raw->pc == addr
+ && bp->raw->inserted)
+ return 1;
+
+ return 0;
+}
+
static int
validate_inserted_breakpoint (struct raw_breakpoint *bp)
{
diff --git a/gdb/gdbserver/mem-break.h b/gdb/gdbserver/mem-break.h
index 2744584..e2aac80 100644
--- a/gdb/gdbserver/mem-break.h
+++ b/gdb/gdbserver/mem-break.h
@@ -104,6 +104,10 @@ int hardware_breakpoint_inserted_here (CORE_ADDR addr);

int reinsert_breakpoint_inserted_here (CORE_ADDR addr);

+/* Returns TRUE if there's any breakpoint other than reinsert at ADDR. */
+
+int non_reinsert_breakpoint_inserted_here (CORE_ADDR addr);
+
/* Clear all breakpoint conditions and commands associated with a
breakpoint. */

@@ -154,7 +158,8 @@ int delete_breakpoint (struct breakpoint *bkpt);

void set_reinsert_breakpoint (CORE_ADDR stop_at, struct thread_info *thread);

-/* Delete all reinsert breakpoints of THREAD. */
+/* Delete all reinsert breakpoints of THREAD. If THREAD is NULL,
+ delete all from all threads. */

void delete_reinsert_breakpoints (struct thread_info *thread);

--
1.9.1