Force to insert software single step breakpoint

GDB doesn't insert software single step breakpoint if the instruction
branches to itself, so that the program can't stop after command "si".

(gdb) b 32
Breakpoint 2 at 0x8680: file git/gdb/testsuite/gdb.base/branch-to-self.c, line 32.
(gdb) c
Continuing.

Breakpoint 2, main () at gdb/git/gdb/testsuite/gdb.base/branch-to-self.c:32
32	  asm (".Lhere: " BRANCH_INSN " .Lhere"); /* loop-line */
(gdb) si
infrun: clear_proceed_status_thread (Thread 3991.3991)
infrun: proceed (addr=0xffffffff, signal=GDB_SIGNAL_DEFAULT)
infrun: step-over queue now empty
infrun: resuming [Thread 3991.3991] for step-over
infrun: skipping breakpoint: stepping past insn at: 0x8680
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Sending packet: $Z0,8678,4#f3...Packet received: OK
infrun: skipping breakpoint: stepping past insn at: 0x8680
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Sending packet: $Z0,b6fe86c8,4#82...Packet received: OK
infrun: resume (step=1, signal=GDB_SIGNAL_0), trap_expected=1, current thread [Thread 3991.3991] at 0x868

breakpoint.c:should_be_inserted thinks the breakpoint shouldn't be
inserted, which is wrong.  This patch restrict the condition that
only skip the non-single-step breakpoints if they are inserted at
the place we are stepping over, however we don't want to skip
single-step breakpoint if its thread is the thread we are stepping
over, so in this patch, I add a thread num in 'struct step_over_info'
to record the thread we're stepping over.

gdb:

2016-04-25  Yao Qi  <yao.qi@linaro.org>

	* breakpoint.c (should_be_inserted): Return 0 if the location's
	owner is not single step breakpoint or single step breakpoint's
	thread isn't the thread which is stepping past a breakpoint.
	* gdbarch.sh (software_single_step): Update comments.
	* gdbarch.h: Regenerated.
	* infrun.c (struct step_over_info) <thread>: New field.
	(set_step_over_info): New argument 'thread'.  Callers updated.
	(clear_step_over_info): Set field thread to -1.
	(thread_is_stepping_over_breakpoint): New function.
	* infrun.h (thread_is_stepping_over_breakpoint): Declaration.

1 files changed, 4 insertions, 0 deletions

diff --git a/gdb/infrun.h b/gdb/infrun.h
index 61d3b20..e79bf2d 100644
--- a/gdb/infrun.h
+++ b/gdb/infrun.h
@@ -133,6 +133,10 @@ extern void insert_step_resume_breakpoint_at_sal (struct gdbarch *,
 extern int stepping_past_instruction_at (struct address_space *aspace,
 					 CORE_ADDR address);
 
+/* Returns true if thread whose thread number is THREAD is stepping
+   over a breakpoint.  */
+extern int thread_is_stepping_over_breakpoint (int thread);
+
 /* Returns true if we're trying to step past an instruction that
    triggers a non-steppable watchpoint.  */
 extern int stepping_past_nonsteppable_watchpoint (void);