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.
+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.
+
2016-04-22 Edjunior Barbosa Machado <emachado@linux.vnet.ibm.com>
* ppc-linux-nat.c (ppc_linux_read_description): Use PPC_FEATURE_HAS_VSX
return 0;
/* Don't insert a breakpoint if we're trying to step past its
- location. */
+ location, except if the breakpoint is a single-step breakpoint,
+ and the breakpoint's thread is the thread which is stepping past
+ a breakpoint. */
if ((bl->loc_type == bp_loc_software_breakpoint
|| bl->loc_type == bp_loc_hardware_breakpoint)
&& stepping_past_instruction_at (bl->pspace->aspace,
- bl->address))
+ bl->address)
+ /* The single-step breakpoint may be inserted at the location
+ we're trying to step if the instruction branches to itself.
+ However, the instruction won't be executed at all and it may
+ break the semantics of the instruction, for example, the
+ instruction is a conditional branch or updates some flags.
+ We can't fix it unless GDB is able to emulate the instruction
+ or switch to displaced stepping. */
+ && !(bl->owner->type == bp_single_step
+ && thread_is_stepping_over_breakpoint (bl->owner->thread)))
{
if (debug_infrun)
{
target can single step. If not, then implement single step using breakpoints.
A return value of 1 means that the software_single_step breakpoints
- were inserted; 0 means they were not. */
+ were inserted; 0 means they were not. Multiple breakpoints may be
+ inserted for some instructions such as conditional branch. However,
+ each implementation must always evaluate the condition and only put
+ the breakpoint at the branch destination if the condition is true, so
+ that we ensure forward progress when stepping past a conditional
+ branch to self. */
extern int gdbarch_software_single_step_p (struct gdbarch *gdbarch);
# target can single step. If not, then implement single step using breakpoints.
#
# A return value of 1 means that the software_single_step breakpoints
-# were inserted; 0 means they were not.
+# were inserted; 0 means they were not. Multiple breakpoints may be
+# inserted for some instructions such as conditional branch. However,
+# each implementation must always evaluate the condition and only put
+# the breakpoint at the branch destination if the condition is true, so
+# that we ensure forward progress when stepping past a conditional
+# branch to self.
F:int:software_single_step:struct frame_info *frame:frame
# Return non-zero if the processor is executing a delay slot and a
/* The instruction being stepped over triggers a nonsteppable
watchpoint. If true, we'll skip inserting watchpoints. */
int nonsteppable_watchpoint_p;
+
+ /* The thread's global number. */
+ int thread;
};
/* The step-over info of the location that is being stepped over.
static void
set_step_over_info (struct address_space *aspace, CORE_ADDR address,
- int nonsteppable_watchpoint_p)
+ int nonsteppable_watchpoint_p,
+ int thread)
{
step_over_info.aspace = aspace;
step_over_info.address = address;
step_over_info.nonsteppable_watchpoint_p = nonsteppable_watchpoint_p;
+ step_over_info.thread = thread;
}
/* Called when we're not longer stepping over a breakpoint / an
step_over_info.aspace = NULL;
step_over_info.address = 0;
step_over_info.nonsteppable_watchpoint_p = 0;
+ step_over_info.thread = -1;
}
/* See infrun.h. */
/* See infrun.h. */
+int
+thread_is_stepping_over_breakpoint (int thread)
+{
+ return (step_over_info.thread != -1
+ && thread == step_over_info.thread);
+}
+
+/* See infrun.h. */
+
int
stepping_past_nonsteppable_watchpoint (void)
{
stop_all_threads ();
set_step_over_info (get_regcache_aspace (regcache),
- regcache_read_pc (regcache), 0);
+ regcache_read_pc (regcache), 0, tp->global_num);
step = maybe_software_singlestep (gdbarch, pc);
&& (remove_wps || !use_displaced_stepping (ecs->event_thread)))
{
set_step_over_info (get_regcache_aspace (regcache),
- regcache_read_pc (regcache), remove_wps);
+ regcache_read_pc (regcache), remove_wps,
+ ecs->event_thread->global_num);
}
else if (remove_wps)
- set_step_over_info (NULL, 0, remove_wps);
+ set_step_over_info (NULL, 0, remove_wps, -1);
/* If we now need to do an in-line step-over, we need to stop
all other threads. Note this must be done before
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);
projects / binutils-gdb.git / commitdiff