Right now, "set debug target" acts a bit strangely.
Most target APIs only notice that it has changed when the target stack
is changed in some way. This is because many methods implement the
setting using the special debug target. However, a few spots do
change their behavior immediately -- any place explicitly checking
"targetdebug".
Some of this peculiar behavior is documented. However, I think that
it just isn't very useful for it to work this way. So, this patch
changes "set debug target" to take effect immediately in all cases.
This is done by simply calling update_current_target when the setting
is changed.
This required one small change in the test suite. Here a test was
expecting the current behavior.
Built and regtested on x86-64 Fedora 20.
2014-08-04 Tom Tromey <tromey@redhat.com>
* target.c (set_targetdebug): New function.
(initialize_targets): Pass set_targetdebug when creating "set
debug target".
2014-08-04 Tom Tromey <tromey@redhat.com>
* gdb.texinfo (Debugging Output): Update for change to "set debug
target".
2014-08-04 Tom Tromey <tromey@redhat.com>
* gdb.base/sss-bp-on-user-bp-2.exp: Expect output from "set debug
target 0".
This fixes a test suite regession that Yao noticed.
This test checks for some specific "target debug" output
that has changed since the test was written.
2014-08-04 Tom Tromey <tromey@redhat.com>
* gdb.base/sss-bp-on-user-bp-2.exp: Match "to_resume", not
"target_resume".
I noticed that sss-bp-on-user-bp-2.exp is racy on native GNU/Linux. I
sometimes still see an int3 in the disassembly:
(gdb) PASS: gdb.base/sss-bp-on-user-bp-2.exp: set debug target 0
disassemble test
Dump of assembler code for function test:
0x0000000000400590 <+0>: push %rbp
0x0000000000400591 <+1>: mov %rsp,%rbp
0x0000000000400594 <+4>: nop
=> 0x0000000000400595 <+5>: int3
0x0000000000400596 <+6>: pop %rbp
0x0000000000400597 <+7>: retq
End of assembler dump.
(gdb) FAIL: gdb.base/sss-bp-on-user-bp-2.exp: before/after disassembly matches
Enabling infrun/target debug logs, we can see the problem.
Simplified, that's:
(gdb) PASS: gdb.base/sss-bp-on-user-bp-2.exp: define stepi_del_break
stepi_del_break
infrun: clear_proceed_status_thread (process 25311)
infrun: resume (step=1, signal=GDB_SIGNAL_0), trap_expected=0, current thread [process 25311] at 0x400594
LLR: PTRACE_SINGLESTEP process 25311, 0 (resume event thread)
target_resume (25311, step, 0)
native:target_xfer_partial (3, (null), 0x0, 0x32dce4c, 0x400595, 1) = 0, 0
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
(gdb) linux_nat_wait: [process -1], [TARGET_WNOHANG]
0x400595 is the address of the breakpoint, and "= 0" is
TARGET_XFER_EOF. That's default_memory_remove_breakpoint trying to
remove the breakpoint, but failing.
The problem is that we had just resumed the target and the native
GNU/Linux target can't read memory off of a running thread. Most of
the time, we get "lucky", because we manage to read memory before the
kernel actually schedules the target to run.
So just give up and skip the test on any target that uses hardware
stepping, not just remote targets.
gdb/testsuite/
2014-06-06 Pedro Alves <palves@redhat.com>
* gdb.base/sss-bp-on-user-bp-2.exp: Look for target_resume(step)
in target debug output instead of looking at RSP packets,
disabling the test on any target that uses hardware stepping.
Update comments.
with the following code...
12 Nested; -- break #1
13 return I; -- break #2
14 end;
(line 12 is a call to function Nested)
... we have noticed the following errorneous behavior on ppc-aix,
where, after having inserted a breakpoint at line 12 and line 13,
and continuing from the breakpoint at line 12, the program never
stops at line 13, running away until the program terminates:
% gdb -q func
(gdb) b func.adb:12
Breakpoint 1 at 0x10000a24: file func.adb, line 12.
(gdb) b func.adb:13
Breakpoint 2 at 0x10000a28: file func.adb, line 13.
(gdb) run
Starting program: /[...]/func
Breakpoint 1, func () at func.adb:12
12 Nested; -- break #1
(gdb) c
Continuing.
[Inferior 1 (process 4128872) exited with code 02]
When resuming from the first breakpoint, GDB first tries to step out
of that first breakpoint. We rely on software single-stepping on this
platform, and it just so happens that the address of the first
software single-step breakpoint is the same as the user's breakpoint
#2 (0x10000a28). So, with infrun and target traces turned on (but
uninteresting traces snip'ed off), the "continue" operation looks like
this:
(gdb) c
### First, we insert the user breakpoints (the second one is an internal
### breakpoint on __pthread_init). The first user breakpoint is not
### inserted as we need to step out of it first.
target_insert_breakpoint (0x0000000010000a28, xxx) = 0
target_insert_breakpoint (0x00000000d03f3800, xxx) = 0
### Then we proceed with the step-out-of-breakpoint...
infrun: resume (step=1, signal=GDB_SIGNAL_0), trap_expected=1, current thread [process 15335610] at 0x10000a24
### That's when we insert the SSS breakpoints...
target_insert_breakpoint (0x0000000010000a28, xxx) = 0
target_insert_breakpoint (0x00000000100009ac, xxx) = 0
### ... then let the inferior resume...
target_resume (15335610, continue, 0)
infrun: wait_for_inferior ()
target_wait (-1, status, options={}) = 15335610, status->kind = stopped, signal = GDB_SIGNAL_TRAP
infrun: target_wait (-1, status) =
infrun: 15335610 [process 15335610],
infrun: status->kind = stopped, signal = GDB_SIGNAL_TRAP
infrun: infwait_normal_state
infrun: TARGET_WAITKIND_STOPPED
infrun: stop_pc = 0x100009ac
### At this point, we stopped at the second SSS breakpoint...
target_stopped_by_watchpoint () = 0
### We remove the SSS breakpoints...
target_remove_breakpoint (0x0000000010000a28, xxx) = 0
target_remove_breakpoint (0x00000000100009ac, xxx) = 0
target_stopped_by_watchpoint () = 0
### We find that we're not done, so we resume....
infrun: no stepping, continue
### And thus insert the user breakpoints again, except we're not
### inserting the second breakpoint?!?
target_insert_breakpoint (0x0000000010000a24, xxx) = 0
infrun: resume (step=0, signal=GDB_SIGNAL_0), trap_expected=0, current thread [process 15335610] at 0x100009ac
target_resume (-1, continue, 0)
infrun: prepare_to_wait
target_wait (-1, status, options={}) = 15335610, status->kind = exited, status = 2
What happens is that the removal of the software single-step
breakpoints effectively removed the breakpoint instruction from
inferior memory. But because such breakpoints are inserted directly
as raw breakpoints rather than through the normal chain of
breakpoints, we fail to notice that one of the user breakpoints points
to the same address and that this user breakpoint is therefore
effectively un-inserted. When resuming after the single-step, GDB
thinks that the user breakpoint is still inserted and therefore does
not need to insert it again.
This patch teaches the insert and remove routines of both regular and
raw breakpoints to be aware of each other. Special care needs to be
applied in case the target supports evaluation of breakpoint
conditions or commands.
gdb/ChangeLog:
PR breakpoints/17000
* breakpoint.c (find_non_raw_software_breakpoint_inserted_here):
New function, extracted from software_breakpoint_inserted_here_p.
(software_breakpoint_inserted_here_p): Replace factored out code
by call to find_non_raw_software_breakpoint_inserted_here.
(bp_target_info_copy_insertion_state): New function.
(bkpt_insert_location): Handle the case of a single-step
breakpoint already inserted at the same address.
(bkpt_remove_location): Handle the case of a single-step
breakpoint still inserted at the same address.
(deprecated_insert_raw_breakpoint): Handle the case of non-raw
breakpoint already inserted at the same address.
(deprecated_remove_raw_breakpoint): Handle the case of a
non-raw breakpoint still inserted at the same address.
(find_single_step_breakpoint): New function, extracted from
single_step_breakpoint_inserted_here_p.
(find_single_step_breakpoint): New function,
factored out from single_step_breakpoint_inserted_here_p.
(single_step_breakpoint_inserted_here_p): Reimplement.
gdb/testsuite/ChangeLog:
PR breakpoints/17000
* gdb.base/sss-bp-on-user-bp.exp: Remove kfail.
* gdb.base/sss-bp-on-user-bp-2.exp: Remove kfail.
Tested on ppc-aix with AdaCore's testsuite. Tested on x86_64-linux,
(native and gdbserver) with the official testsuite. Also tested on
x86_64-linux through Pedro's branch enabling software single-stepping
on that platform (native and gdbserver).
gdb/testsuite/
2014-06-03 Pedro Alves <palves@redhat.com>
* gdb.base/sss-bp-on-user-bp-2.exp: Skip if testing with a remote
target that doesn't use software single-stepping.
GDB gets confused when removing a software single-step breakpoint that
is at the same address as another breakpoint. Add another kfailed
test.
gdb/testsuite/
2014-06-03 Pedro Alves <palves@redhat.com>
PR breakpoints/17000
* gdb.base/sss-bp-on-user-bp-2.c: New file.
* gdb.base/sss-bp-on-user-bp-2.exp: New file.
