infrun.c:handle_one calls find_inferior_ptid unnecessarily, since we
already have a thread pointer handy, and the thread has a pointer to
the inferior. This commit removes the unnecessary lookup.
Change-Id: I2ae18601dd75346c6c91068e9a4f9a6484fb3339
No kind of internal var uses it remove it. This makes the transition to
using a variant easier, since we don't need to think about where this
should be called (in a destructor or not), if it can throw, etc.
Change-Id: Iebbc867d1ce6716480450d9790410d6684cbe4dd
Commit 14b3360508 ("do_target_wait_1: Clear
TARGET_WNOHANG if the target isn't async.") broke some multi-target
tests, such as gdb.multi/multi-target-info-inferiors.exp. The symptom
is that execution just hangs at some point. What happens is:
1. One remote inferior is started, and now sits stopped at a breakpoint.
It is not "async" at this point (but it "can async").
2. We run a native inferior, the event loop gets woken up by the native
target's fd.
3. In do_target_wait, we randomly choose an inferior to call target_wait
on first, it happens to be the remote inferior.
4. Because the target is currently not "async", we clear
TARGET_WNOHANG, resulting in synchronous wait. We therefore block
here:
#0 0x00007fe9540dbb4d in select () from /usr/lib/libc.so.6
#1 0x000055fc7e821da7 in gdb_select (n=15, readfds=0x7ffdb77c1fb0, writefds=0x0, exceptfds=0x7ffdb77c2050, timeout=0x7ffdb77c1f90) at /home/simark/src/binutils-gdb/gdb/posix-hdep.c:31
#2 0x000055fc7ddef905 in interruptible_select (n=15, readfds=0x7ffdb77c1fb0, writefds=0x0, exceptfds=0x7ffdb77c2050, timeout=0x7ffdb77c1f90) at /home/simark/src/binutils-gdb/gdb/event-top.c:1134
#3 0x000055fc7eda58e4 in ser_base_wait_for (scb=0x6250002e4100, timeout=1) at /home/simark/src/binutils-gdb/gdb/ser-base.c:240
#4 0x000055fc7eda66ba in do_ser_base_readchar (scb=0x6250002e4100, timeout=-1) at /home/simark/src/binutils-gdb/gdb/ser-base.c:365
#5 0x000055fc7eda6ff6 in generic_readchar (scb=0x6250002e4100, timeout=-1, do_readchar=0x55fc7eda663c <do_ser_base_readchar(serial*, int)>) at /home/simark/src/binutils-gdb/gdb/ser-base.c:444
#6 0x000055fc7eda718a in ser_base_readchar (scb=0x6250002e4100, timeout=-1) at /home/simark/src/binutils-gdb/gdb/ser-base.c:471
#7 0x000055fc7edb1ecd in serial_readchar (scb=0x6250002e4100, timeout=-1) at /home/simark/src/binutils-gdb/gdb/serial.c:393
#8 0x000055fc7ec48b8f in remote_target::readchar (this=0x617000038780, timeout=-1) at /home/simark/src/binutils-gdb/gdb/remote.c:9446
#9 0x000055fc7ec4da82 in remote_target::getpkt_or_notif_sane_1 (this=0x617000038780, buf=0x6170000387a8, forever=1, expecting_notif=1, is_notif=0x7ffdb77c24f0) at /home/simark/src/binutils-gdb/gdb/remote.c:9928
#10 0x000055fc7ec4f045 in remote_target::getpkt_or_notif_sane (this=0x617000038780, buf=0x6170000387a8, forever=1, is_notif=0x7ffdb77c24f0) at /home/simark/src/binutils-gdb/gdb/remote.c:10037
#11 0x000055fc7ec354d4 in remote_target::wait_ns (this=0x617000038780, ptid=..., status=0x7ffdb77c33c8, options=...) at /home/simark/src/binutils-gdb/gdb/remote.c:8147
#12 0x000055fc7ec38aa1 in remote_target::wait (this=0x617000038780, ptid=..., status=0x7ffdb77c33c8, options=...) at /home/simark/src/binutils-gdb/gdb/remote.c:8337
#13 0x000055fc7f1409ce in target_wait (ptid=..., status=0x7ffdb77c33c8, options=...) at /home/simark/src/binutils-gdb/gdb/target.c:2612
#14 0x000055fc7e19da98 in do_target_wait_1 (inf=0x617000038080, ptid=..., status=0x7ffdb77c33c8, options=...) at /home/simark/src/binutils-gdb/gdb/infrun.c:3636
#15 0x000055fc7e19e26b in operator() (__closure=0x7ffdb77c2f90, inf=0x617000038080) at /home/simark/src/binutils-gdb/gdb/infrun.c:3697
#16 0x000055fc7e19f0c4 in do_target_wait (ecs=0x7ffdb77c33a0, options=...) at /home/simark/src/binutils-gdb/gdb/infrun.c:3716
#17 0x000055fc7e1a31f7 in fetch_inferior_event () at /home/simark/src/binutils-gdb/gdb/infrun.c:4061
Before the aforementioned commit, we would not have cleared
TARGET_WNOHANG, the remote target's wait would have returned nothing,
and we would have consumed the native target's event.
After applying this revert, the testsuite state looks as good as before
for me on Ubuntu 20.04 amd64.
Change-Id: Ic17a1642935cabcc16c25cb6899d52e12c2f5c3f
Previously, TARGET_WNOHANG was cleared if a target supported async
mode even if async mode wasn't currently enabled. This change only
permits TARGET_WNOHANG if async mode is enabled.
Enabling async mode above the target layer removes duplicate code in
::resume methods of async-capable targets. Commit 5b6d1e4fa4
("Multi-target support") enabled async mode in do_target_resume after
target_resume returns which is a step in this direction. However,
other callers of target_resume such as target_continue do not enable
async mode. Rather than enabling async mode in each of the callers
after target_resume returns, enable async mode at the end of
target_resume.
While reviewing a different patch I wanted to know more about what was
going on during GDB's stepping. I added some extra infrun debug print
calls, and I thought these might be useful to others.
While working on function calls, I realized that the thread_fsm member
of struct thread_info is a raw pointer to a resource it owns. This
commit changes the type of the thread_fsm member to a std::unique_ptr in
order to signify this ownership relationship and slightly ease resource
management (no need to manually call delete).
To ensure consistent use, the field is made a private member
(m_thread_fsm). The setter method (set_thread_fsm) can then check
that it is incorrect to associate a FSM to a thread_info object if
another one is already in place. This is ensured by an assertion.
The function run_inferior_call takes an argument as a pointer to a
call_thread_fsm and installs it in it in a thread_info instance. Also
change this function's signature to accept a unique_ptr in order to
signify that the ownership of the call_thread_fsm is transferred during
the call.
No user visible change expected after this commit.
Tested on x86_64-linux with no regression observed.
Change-Id: Ia1224f72a4afa247801ce6650ce82f90224a9ae8
Add a getter and a setter for whether a symbol is an argument. Remove
the corresponding macro and adjust all callers.
Change-Id: I71b4f0465f3dfd2ed8b9e140bd3f7d5eb8d9ee81
This commit brings all the changes made by running gdb/copyright.py
as per GDB's Start of New Year Procedure.
For the avoidance of doubt, all changes in this commits were
performed by the script.
A following patch will change targets so that when they detach an
inferior, they also detach any pending fork children this inferior may
have. While doing this, I hit a case where we couldn't differentiate
two cases, where in one we should detach the fork detach but not in the
other.
Suppose we continue past a fork with "follow-fork-mode == child" &&
"detach-on-fork on". follow_fork_inferior calls target_detach to detach
the parent. In that case the target should not detach the fork
child, as we'll continue debugging the child. As of now, the
tp->pending_follow field of the thread who called fork still contains
the details about the fork.
Then, suppose we run to a fork catchpoint and the user types "detach".
In that case, the target should detach the fork child in addition to the
parent. In that case as well, the tp->pending_follow field contains
the details about the fork.
To allow targets to differentiate the two cases, clear
tp->pending_follow a bit earlier, when following a fork. Targets will
then see that tp->pending_follow contains TARGET_WAITKIND_SPURIOUS, and
won't detach the fork child.
As of this patch, no behavior changes are expected.
Change-Id: I537741859ed712cb531baaefc78bb934e2a28153
While working on target_waitstatus changes, I noticed a few places where
const target_waitstatus objects could be passed by reference instead of
by pointers. And in some cases, places where a target_waitstatus could
be passed as const, but was not. Convert them as much as possible.
Change-Id: Ied552d464be5d5b87489913b95f9720a5ad50c5a
Make target_waitstatus_to_string a "to_string" method of
target_waitstatus, a bit like we have ptid_t::to_string already. This
will save a bit of typing.
Change-Id: Id261b7a09fa9fa3c738abac131c191a6f9c13905
Change gdb_assert_not_reached to accept a format string plus
corresponding arguments. This allows giving more precise messages.
Because the format string passed by the caller is prepended with a "%s:"
to add the function name, the callers can no longer pass a translated
string (`_(...)`). Make the gdb_assert_not_reached include the _(),
just like the gdb_assert_fail macro just above.
Change-Id: Id0cfda5a57979df6cdaacaba0d55dd91ae9efee7
The test-case gdb.base/foll-vfork.exp contains:
...
if [gdb_debug_enabled] {
untested "debug is enabled"
return 0
}
...
To understand what it does, I disabled this bit and ran with GDB_DEBUG=infrun,
like so:
...
$ cd $build/gdb/testsuite
$ make check GDB_DEBUG=infrun RUNTESTFLAGS=gdb.base/foll-vfork.exp
...
and ran into:
...
(gdb) PASS: gdb.base/foll-vfork.exp: exec: \
vfork parent follow, through step: set follow-fork parent
next^M
33 if (pid == 0) {^M
(gdb) FAIL: gdb.base/foll-vfork.exp: exec: \
vfork parent follow, through step: step
...
The problem is that the test-case expects:
...
(gdb) PASS: gdb.base/foll-vfork.exp: exec: \
vfork parent follow, through step: set follow-fork parent
next^M
[Detaching after vfork from child process 28169]^M
33 if (pid == 0) {^M
(gdb) PASS: gdb.base/foll-vfork.exp: exec: \
vfork parent follow, through step: step
...
but the "Detaching" line has been redirected to
$outputs/gdb.base/foll-vfork/gdb.debug.
I looked at the documentation of "set logging debugredirect [on|off]":
...
By default, GDB debug output will go to both the terminal and the logfile.
Set debugredirect if you want debug output to go only to the log file.
...
and my interpretation of it was that "debug output" did not match the
"messages" description of inferior-events:
...
The set print inferior-events command allows you to enable or disable printing
of messages when GDB notices that new inferiors have started or that inferiors
have exited or have been detached.
...
Fix the discrepancy by not using gdb_stdlog for inferior-events.
Update the gdb.base/foll-vfork.exp test-case to not require
gdb_debug_enabled == 0.
Tested on x86_64-linux.
Tested test-case gdb.base/foll-vfork.exp with and without GDB_DEBUG=infrun.
GDB hangs when doing this:
- launch inferior with multiple threads
- multiple threads hit some breakpoint(s)
- one breakpoint hit is presented as a stop, the rest are saved as
pending wait statuses
- "set scheduler-locking on"
- resume the currently selected thread (because of scheduler-locking,
it's the only one resumed), let it execute until exit
- GDB hangs, not showing the prompt, impossible to interrupt with ^C
When the resumed thread exits, we expect the target to return a
TARGET_WAITKIND_NO_RESUMED event, and that's what we see:
[infrun] fetch_inferior_event: enter
[infrun] scoped_disable_commit_resumed: reason=handling event
[infrun] random_pending_event_thread: None found.
[Thread 0x7ffff7d9c700 (LWP 309357) exited]
[infrun] print_target_wait_results: target_wait (-1.0.0 [process -1], status) =
[infrun] print_target_wait_results: -1.0.0 [process -1],
[infrun] print_target_wait_results: status->kind = no-resumed
[infrun] handle_inferior_event: status->kind = no-resumed
[infrun] handle_no_resumed: TARGET_WAITKIND_NO_RESUMED (ignoring: found resumed)
[infrun] prepare_to_wait: prepare_to_wait
[infrun] reset: reason=handling event
[infrun] maybe_set_commit_resumed_all_targets: not requesting commit-resumed for target native, no resumed threads
[infrun] fetch_inferior_event: exit
The problem is in handle_no_resumed: we check if some other thread is
actually resumed, to see if we should ignore that event (see comments in
that function for more info). If this condition is true:
(thread->executing () || thread->has_pending_waitstatus ())
... then we ignore the event. The problem is that there are some non-resumed
threads with a pending event, which makes us ignore the event. But these
threads are not resumed, so we end up waiting while nothing executes, hence
waiting for ever.
My first fix was to change the condition to:
(thread->executing ()
|| (thread->resumed () && thread->has_pending_waitstatus ()))
... but then it occured to me that we could simply check for:
(thread->resumed ())
Since "executing" implies "resumed", checking simply for "resumed"
covers threads that are resumed and executing, as well as threads that
are resumed with a pending status, which is what we want.
Change-Id: Ie796290f8ae7f34c026ca3a8fcef7397414f4780
I don't find that the bpstat typedef, which hides a pointer, is
particularly useful. In fact, it confused me many times, and I just see
it as something to remember that adds cognitive load. Also, with C++,
we might want to be able to pass bpstats objects by const-reference, not
necessarily by pointer.
So, remove the bpstat typedef and rename struct bpstats to bpstat (since
it represents one bpstat, it makes sense that it is singular).
Change-Id: I52e763b6e54ee666a9e045785f686d37b4f5f849
In debug messages, I think it would be more helpful to print ptid using
the simple "pid.lwp.tid" notation in infrun debug messages. I am
currently debugging some fork issues, and find the pid_to_str output not
so useful, as it doesn't tell which process a thread belongs to.
It currently shows up like this:
[infrun] resume_1: step=1, signal=GDB_SIGNAL_0, trap_expected=0, current thread [Thread 0x7ffff7d95740 (LWP 892942)] at 0x55555555521f
With the patch, it shows up like this:
[infrun] resume_1: step=1, signal=GDB_SIGNAL_0, trap_expected=1, current thread [894072.894077.0] at 0x5555555551d9
Change-Id: I130796d7dfb0d8e763b8358d8a6002701d80c4ea
The bug fixed by this [1] patch was caused by an out-of-bounds access to
a value's content. The code gets the value's content (just a pointer)
and then indexes it with a non-sensical index.
This made me think of changing functions that return value contents to
return array_views instead of a plain pointer. This has the advantage
that when GDB is built with _GLIBCXX_DEBUG, accesses to the array_view
are checked, making bugs more apparent / easier to find.
This patch changes the return types of these functions, and updates
callers to call .data() on the result, meaning it's not changing
anything in practice. Additional work will be needed (which can be done
little by little) to make callers propagate the use of array_view and
reap the benefits.
[1] https://sourceware.org/pipermail/gdb-patches/2021-September/182306.html
Change-Id: I5151f888f169e1c36abe2cbc57620110673816f3
I stumbled on a bug caused by the fact that a code path read
target_waitstatus::value::sig (expecting it to contain a gdb_signal
value) while target_waitstatus::kind was TARGET_WAITKIND_FORKED. This
meant that the active union field was in fact
target_waitstatus::value::related_pid, and contained a ptid. The read
signal value was therefore garbage, and that caused GDB to crash soon
after. Or, since that GDB was built with ubsan, this nice error
message:
/home/simark/src/binutils-gdb/gdb/linux-nat.c:1271:12: runtime error: load of value 2686365, which is not a valid value for type 'gdb_signal'
Despite being a large-ish change, I think it would be nice to make
target_waitstatus safe against that kind of bug. As already done
elsewhere (e.g. dynamic_prop), validate that the type of value read from
the union matches what is supposed to be the active field.
- Make the kind and value of target_waitstatus private.
- Make the kind initialized to TARGET_WAITKIND_IGNORE on
target_waitstatus construction. This is what most users appear to do
explicitly.
- Add setters, one for each kind. Each setter takes as a parameter the
data associated to that kind, if any. This makes it impossible to
forget to attach the associated data.
- Add getters, one for each associated data type. Each getter
validates that the data type fetched by the user matches the wait
status kind.
- Change "integer" to "exit_status", "related_pid" to "child_ptid",
just because that's more precise terminology.
- Fix all users.
That last point is semi-mechanical. There are a lot of obvious changes,
but some less obvious ones. For example, it's not possible to set the
kind at some point and the associated data later, as some users did.
But in any case, the intent of the code should not change in this patch.
This was tested on x86-64 Linux (unix, native-gdbserver and
native-extended-gdbserver boards). It was built-tested on x86-64
FreeBSD, NetBSD, MinGW and macOS. The rest of the changes to native
files was done as a best effort. If I forgot any place to update in
these files, it should be easy to fix (unless the change happens to
reveal an actual bug).
Change-Id: I0ae967df1ff6e28de78abbe3ac9b4b2ff4ad03b7
The "make thread_suspend_state::stop_pc optional" patch caused a
regression on Windows when using shared libraries. I tracked this
down to an unguarded use of stop_pc() in the TARGET_WAITKIND_LOADED
case of handle_inferior_event. This patch fixes the bug by ensuring
that the stop PC is set at this point.
We found that when handling forks, two inferiors can unexpectedly share
their program space and address space. To reproduce:
1. Using a test program that forks...
2. "set follow-fork-mode child"
3. "set detach-on-fork on" (the default)
4. run to a breakpoint somewhere after the fork
Step 4 should have created a new inferior:
(gdb) info inferiors
Num Description Connection Executable
1 <null> /home/smarchi/build/wt/amd/gdb/fork
* 2 process 251425 1 (native) /home/smarchi/build/wt/amd/gdb/fork
By inspecting the state of GDB, we can see that the two inferiors now
share one program space and one address space:
Inferior 1:
(top-gdb) p inferior_list.m_front.num
$2 = 1
(top-gdb) p inferior_list.m_front.aspace
$3 = (struct address_space *) 0x5595e2520400
(top-gdb) p inferior_list.m_front.pspace
$4 = (struct program_space *) 0x5595e2520440
Inferior 2:
(top-gdb) p inferior_list.m_front.next.num
$5 = 2
(top-gdb) p inferior_list.m_front.next.aspace
$6 = (struct address_space *) 0x5595e2520400
(top-gdb) p inferior_list.m_front.next.pspace
$7 = (struct program_space *) 0x5595e2520440
You can then run inferior 1 again and the two inferiors will still
erroneously share their spaces, but already at this point this is wrong.
The cause of the bad {a,p}space sharing is in follow_fork_inferior.
When following the child and detaching from the parent, we just re-use
the parent's spaces, rather than cloning them. When we switch back to
inferior 1 and run again, we find ourselves with two unrelated inferiors
sharing spaces.
Fix that by creating new spaces for the parent after having moved them
to the child. My initial implementation created new spaces for the
child instead. Doing this breaks doing "next" over fork(). When "next"
start, we record the symtab of the starting location. When the program
stops, we compare that symtab with the symtab the program has stopped
at. If the symtab or the line number has changed, we conclude the
"next" is done. If we create a new program space for the child and copy
the parent's program space to it with clone_program_space, it creates
new symtabs for the child as well. When the child stop, but still on
the fork() line, GDB thinks the "next" is done because the symtab
pointers no longer match. In reality they are two symtab instances that
represent the same file. But moving the spaces to the child and
creating new spaces for the parent, we avoid this problem.
Note that the problem described above happens today with "detach-on-fork
off" and "follow-fork-mode child", because we create new spaces for the
child. This will have to be addressed later.
Test-wise, improve gdb.base/foll-fork.exp to set a breakpoint that is
expected to have a location in each inferiors. Without the fix, when
the two inferiors erroneously share a program space, GDB reports a
single location.
Change-Id: Ifea76e14f87b9f7321fc3a766217061190e71c6e
This started out as changing thread_info::name to a unique_xmalloc_ptr.
That showed that almost all users of that field had the same logic to
get a thread's name: use thread_info::name if non-nullptr, else ask the
target. Factor out this logic in a new thread_name free function. Make
the field private (rename to m_name) and add some accessors.
Change-Id: Iebdd95f4cd21fbefc505249bd1d05befc466a2fc
The ptid_t 'tid' member is normally used as an address in gdb -- both
bsd-uthread and ravenscar-thread use it this way. However, because
the type is 'long', this can cause problems with sign extension.
This patch changes the type to ULONGEST to ensure that sign extension
does not occur.
Currently the stop_pc field of thread_suspect_state is a CORE_ADDR and
when we want to indicate that there is no stop_pc available we set
this field back to a special value.
There are actually two special values used, in post_create_inferior
the stop_pc is set to 0. This is a little unfortunate, there are
plenty of embedded targets where 0 is a valid pc value. The more
common special value for stop_pc though, is set in
thread_info::set_executing, where the value (~(CORE_ADDR) 0) is used.
This commit changes things so that the stop_pc is instead a
gdb::optional. We can now explicitly reset the field to an
uninitialised state, we also have asserts that we don't read the
stop_pc when its in an uninitialised state (both in
gdbsupport/gdb_optional.h, when compiling with _GLIBCXX_DEBUG
defined, and in thread_info::stop_pc).
One situation where a thread will not have a stop_pc value is when the
thread is stopped as a consequence of GDB being in all stop mode, and
some other thread stopped at an interesting event. When GDB brings
all the other threads to a stop those other threads will not have a
stop_pc set (thus avoiding an unnecessary read of the pc register).
Previously, when GDB passed through handle_one (in infrun.c) the
threads executing flag was set to false and the stop_pc field was left
unchanged, i.e. it would (previous) have been left as ~0.
Now, handle_one leaves the stop_pc with no value.
This caused a problem when we later try to set these threads running
again, in proceed() we compare the current pc with the cached stop_pc.
If the thread was stopped via handle_one then the stop_pc would have
been left as ~0, and the compare (in proceed) would (likely) fail.
Now however, this compare tries to read the stop_pc when it has no
value and this would trigger an assert.
To resolve this I've added thread_info::stop_pc_p() which returns true
if the thread has a cached stop_pc. We should only ever call
thread_info::stop_pc() if we know that there is a cached stop_pc,
however, this doesn't mean that every call to thread_info::stop_pc()
needs to be guarded with a call to thread_info::stop_pc_p(), in most
cases we know that the thread we are looking at stopped due to some
interesting event in that thread, and so, we know that the stop_pc is
valid.
After running the testsuite I've seen no other situations where
stop_pc is read uninitialised.
There should be no user visible changes after this commit.
Rename thread_info::executing to thread_info::m_executing, and make it
private. Add a new get/set member functions, and convert GDB to make
use of these.
The only real change of interest in this patch is in thread.c where I
have deleted the helper function set_executing_thread, and now just
use the new set function thread_info::set_executing. However, the old
helper function set_executing_thread included some code to reset the
thread's stop_pc, so I moved this code into the new function
thread_info::set_executing. However, I don't believe there is
anywhere that this results in a change of behaviour, previously the
executing flag was always set true through a call to
set_executing_thread anyway.
Remove breakpoint_find_if, replace its sole usage with using
all_breakpoints directly instead. At the same time, change return
types to use bool.
Change-Id: I9ec392236b4804b362d16ab563330b9c07311106
I spotted what I think is a buglet in proceed_after_vfork_done. After a
vfork child exits or execs, we resume all the threads of the parent. To
do so, we iterate on all threads using iterate_over_threads with the
proceed_after_vfork_done callback. Each thread is resumed if the
following condition is true:
if (thread->ptid.pid () == pid
&& thread->state == THREAD_RUNNING
&& !thread->executing
&& !thread->stop_requested
&& thread->stop_signal () == GDB_SIGNAL_0)
where `pid` is the pid of the vfork parent. This is not multi-target
aware: since it only filters on pid, if there is an inferior with the
same pid in another target, we could end up resuming a thread of that
other inferior. The chances of the stars aligning for this to happen
are tiny, but still.
Fix that by iterating only on the vfork parent's threads, instead of on
all threads. This is more efficient, as we iterate on just the required
threads (inferiors have their own thread list), and we can drop the pid
check. The resulting code is also more straightforward in my opinion,
so it's a win-win.
Change-Id: I14647da72e2bf65592e82fbe6efb77a413a4be3a
The ptid_t::to_string method was introduced recently, to format a ptid_t
for debug purposes. It formats the ptid exactly as is done in
print_target_wait_results, so make print_target_wait_results use it.
Change-Id: I0a81c8040d3e1858fb304cb28366b34d94eefe4d
In the context of ROCm-gdb [1], the ROCm target sits on top of the
linux-nat target. when a process forks, it needs to carry over some
data from the forking inferior to the fork child inferior. Ideally, the
ROCm target would implement the follow_fork target_ops method, but there
are some small problems. This patch fixes these, which helps the ROCm
target, but also makes things more consistent and a bit nicer in
general, I believe.
The main problem is: when follow-fork-mode is "parent",
target_follow_fork is called with the parent as the current inferior.
When it's "child", target_follow_fork is called with the child as the
current inferior. This means that target_follow_fork is sometimes
called on the parent's target stack and sometimes on the child's target
stack.
The parent's target stack may contain targets above the process target,
such as the ROCm target. So if follow-fork-child is "parent", the ROCm
target would get notified of the fork and do whatever is needed. But
the child's target stack, at that moment, only contains the exec and
process target copied over from the parent. The child's target stack is
set up by follow_fork_inferior, before calling target_follow_fork. In
that case, the ROCm target wouldn't get notified of the fork.
For consistency, I think it would be good to always call
target_follow_fork on the parent inferior's target stack. I think it
makes sense as a way to indicate "this inferior has called fork, do
whatever is needed". The desired outcome of the fork (whether an
inferior is created for the child, do we need to detach from the child)
can be indicated by passed parameter.
I therefore propose these changes:
- make follow_fork_inferior always call target_follow_fork with the
parent as the current inferior. That lets all targets present on the
parent's target stack do some fork-related handling and push
themselves on the fork child's target stack if needed.
For this purpose, pass the child inferior down to target_follow_fork
and follow_fork implementations. This is nullptr if no inferior is
created for the child, because we want to detach from it.
- as a result, in follow_fork_inferior, detach from the parent inferior
(if needed) only after the target_follow_fork call. This is needed
because we want to call target_follow_fork before the parent's
target stack is torn down.
- hand over to the targets in the parent's target stack (including the
process target) the responsibility to push themselves, if needed, to
the child's target stack. Also hand over the responsibility to the
process target, at the same time, to create the child's initial
thread (just like we do for follow_exec).
- pass the child inferior to exec_on_vfork, so we don't need to swap
the current inferior between parent and child. Nothing in
exec_on_vfork depends on the current inferior, after this change.
Although this could perhaps be replaced with just having the exec
target implement follow_fork and push itself in the child's target
stack, like the process target does... We would just need to make
sure the process target calls beneath()->follow_fork(...). I'm not
sure about this one.
gdb/ChangeLog:
* target.h (struct target_ops) <follow_fork>: Add inferior*
parameter.
(target_follow_fork): Likewise.
* target.c (default_follow_fork): Likewise.
(target_follow_fork): Likewise.
* fbsd-nat.h (class fbsd_nat_target) <follow_fork>: Likewise.
(fbsd_nat_target::follow_fork): Likewise, and call
inf_ptrace_target::follow_fork.
* linux-nat.h (class linux_nat_target) <follow_fork>: Likewise.
* linux-nat.c (linux_nat_target::follow_fork): Likewise, and
call inf_ptrace_target::follow_fork.
* obsd-nat.h (obsd_nat_target) <follow_fork>: Likewise.
* obsd-nat.c (obsd_nat_target::follow_fork): Likewise, and call
inf_ptrace_target::follow_fork.
* remote.c (class remote_target) <follow_fork>: Likewise.
(remote_target::follow_fork): Likewise, and call
process_stratum_target::follow_fork.
* process-stratum-target.h (class process_stratum_target)
<follow_fork>: New.
* process-stratum-target.c
(process_stratum_target::follow_fork): New.
* target-delegates.c: Re-generate.
[1] https://github.com/ROCm-Developer-Tools/ROCgdb
Change-Id: I460bd0af850f0485e8aed4b24c6d8262a4c69929
GDB doesn't handle well the case of an inferior using the JIT interface
to register JIT-ed objfiles and forking. If an inferior registers a
code object using the JIT interface and then forks, the child process
conceptually has the same code object loaded, so GDB should look it up
and learn about it (it currently doesn't).
To achieve this, I think it would make sense to have the
inferior_created observable called when an inferior is created due to a
fork in follow_fork_inferior. The inferior_created observable is
currently called both after starting a new inferior and after attaching
to an inferior, allowing various sub-components to learn about that new
executing inferior. We can see handling a fork child just like
attaching to it, so any work done when attaching should also be done in
the case of a fork child.
Instead of just calling the inferior_created observable, this patch
makes follow_fork_inferior call the whole post_create_inferior function.
This way, the attach and follow-fork code code paths are more alike.
Given that post_create_inferior calls solib_create_inferior_hook,
follow_fork_inferior doesn't need to do it itself, so those calls to
solib_create_inferior_hook are removed.
One question you may have: why not just call post_create_inferior at the
places where solib_create_inferior_hook is currently called, instead of
after target_follow_fork?
- there's something fishy for the second solib_create_inferior_hook
call site: at this point we have switched the current program space
to the child's, but not the current inferior nor the current thread.
So solib_create_inferior_hook (and everything under, including
check_for_thread_db, for example) is called with inferior 1 as the
current inferior and inferior 2's program space as the current
program space. I think that's wrong, because at this point we are
setting up inferior 2, and all that code relies on the current
inferior. We could just add a switch_to_thread call before it to
make inferior 2 the current one, but there are other problems (see
below).
- solib_create_inferior_hook is currently not called on the
`follow_child && detach_fork` path. I think we need to call it,
because we still get a new inferior in that case (even though we
detach the parent). If we only call post_create_inferior where
solib_create_inferior_hook used to be called, then the JIT
subcomponent doesn't get informed about the new inferior, and that
introduces a failure in the new gdb.base/jit-elf-fork.exp test.
- if we try to put the post_create_inferior just after the
switch_to_thread that was originally at line 662, or just before the
call to target_follow_fork, we introduce a subtle failure in
gdb.threads/fork-thread-pending.exp. What happens then is that
libthread_db gets loaded (somewhere under post_create_inferior)
before the linux-nat target learns about the LWPs (which happens in
linux_nat_target::follow_fork). As a result, the ALL_LWPS loop in
try_thread_db_load_1 doesn't see the child LWP, and the thread-db
target doesn't have the chance to fill in thread_info::priv. A bit
later, when the test does "info threads", and
thread_db_target::pid_to_str is called, the thread-db target doesn't
recognize the thread as one of its own, and delegates the request to
the target below. Because the pid_to_str output is not the expected
one, the test fails.
This tells me that we need to call the process target's follow_fork
first, to make the process target create the necessary LWP and thread
structures. Then, we can call post_create_inferior to let the other
components of GDB do their thing.
But then you may ask: check_for_thread_db is already called today,
somewhere under solib_create_inferior_hook, and that is before
target_follow_fork, why don't we see this ordering problem!? Well,
because of the first bullet point: when check_for_thread_db /
thread_db_load are called, the current inferior is (erroneously)
inferior 1, the parent. Because libthread_db is already loaded for
the parent, thread_db_load early returns. check_for_thread_db later
gets called by linux_nat_target::follow_fork. At this point, the
current inferior is the correct one and the child's LWP exists, so
all is well.
Since we now call post_create_inferior after target_follow_fork, which
calls the inferior_created observable, which calls check_for_thread_db,
I don't think linux_nat_target needs to explicitly call
check_for_thread_db itself, so that is removed.
In terms of testing, this patch adds a new gdb.base/jit-elf-fork.exp
test. It makes an inferior register a JIT code object and then fork.
It then verifies that whatever the detach-on-fork and follow-fork-child
parameters are, GDB knows about the JIT code object in all the inferiors
that survive the fork. It verifies that the inferiors can unload that
code object.
There isn't currently a way to get visibility into GDB's idea of the JIT
code objects for each inferior. For the purpose of this test, add the
"maintenance info jit" command. There isn't much we can print about the
JIT code objects except their load address. So the output looks a bit
bare, but it's good enough for the test.
gdb/ChangeLog:
* NEWS: Mention "maint info jit" command.
* infrun.c (follow_fork_inferior): Don't call
solib_create_inferior_hook, call post_create_inferior if a new
inferior was created.
* jit.c (maint_info_jit_cmd): New.
(_initialize_jit): Register new command.
* linux-nat.c (linux_nat_target::follow_fork): Don't call
check_for_thread_db.
* linux-nat.h (check_for_thread_db): Remove declaration.
* linux-thread-db.c (check_thread_signals): Make static.
gdb/doc/ChangeLog:
* gdb.texinfo (Maintenance Commands): Mention "maint info jit".
gdb/testsuite/ChangeLog:
* gdb.base/jit-elf-fork-main.c: New test.
* gdb.base/jit-elf-fork-solib.c: New test.
* gdb.base/jit-elf-fork.exp: New test.
Change-Id: I9a192e55b8a451c00e88100669283fc9ca60de5c
When debugging a large number of threads (thousands), looking up a
thread by ptid_t using the inferior::thread_list linked list can add up.
Add inferior::thread_map, an std::unordered_map indexed by ptid_t, and
change the find_thread_ptid function to look up a thread using
std::unordered_map::find, instead of iterating on all of the
inferior's threads. This should make it faster to look up a thread
from its ptid.
Change-Id: I3a8da0a839e18dee5bb98b8b7dbeb7f3dfa8ae1c
Co-Authored-By: Pedro Alves <pedro@palves.net>
Consider a case where many threads (thousands) keep hitting a breakpoint
whose condition evaluates to false. random_pending_event_thread is
responsible for selecting a thread from an inferior among all that are
resumed with a pending wait status. It is currently implemented by
walking the inferior's thread list twice: once to count the number of
candidates and once to select a random one.
Since we now maintain a per target list of resumed threads with pending
event, we can implement this more efficiently by walking that list and
selecting the first thread that matches the criteria
(random_pending_event_thread looks for an thread from a specific
inferior, and possibly a filter ptid). It will be faster especially in
the common case where there isn't any resumed thread with pending
event. Currently, we have to iterate the thread list to figure this
out. With this patch, the list of resumed threads with pending event
will be empty, so it's quick to figure out.
The random selection is kept, but is moved to
process_stratum_target::random_resumed_with_pending_wait_status. The
same technique is used: do a first pass to count the number of
candidates, and do a second pass to select a random one. But given that
the list of resumed threads with pending wait statuses will generally be
short, or at least shorter than the full thread list, it should be
quicker.
Note that this isn't completely true, in case there are multiple
inferiors on the same target. Imagine that inferior A has 10k resumed
threads with pending wait statuses, and random_pending_event_thread is
called with inferior B. We'll need to go through the list that contains
inferior A's threads to realize that inferior B has no resumed threads
with pending wait status. But I think that this is a corner /
pathological case. And a possible fix for this situation would be to
make random_pending_event_thread work per-process-target, rather than
per-inferior.
Change-Id: I1b71d01beaa500a148b5b9797745103e13917325
Consider a test case where many threads (thousands) keep hitting a
breakpoint whose condition evaluates to false.
maybe_set_commit_resumed_all_targets is called at each handled event,
when the scoped_disable_commit_resumed object in fetch_inferior_event is
reset_and_commit-ed. One particularly expensive check in there is
whether the target has at least one resumed thread with a pending wait
status (in which case, we don't want to commit the resumed threads, as
we want to consume this status first). It is currently implemented as
walking all threads of the target.
Since we now maintain a per-target list of resumed threads with pending
status, we can do this check efficiently, by checking whether that list
is empty or not.
Add the process_stratum_target::has_resumed_with_pending_wait_status
method for this, and use it in maybe_set_commit_resumed_all_targets.
Change-Id: Ia1595baa1b358338f94fc3cb3af7f27092dad5b6
A following patch will want to take some action when a pending wait
status is set on or removed from a thread. Add a getter and a setter on
thread_info for the pending waitstatus, so that we can add some code in
the setter later.
The thing is, the pending wait status field is in the
thread_suspend_state, along with other fields that we need to backup
before and restore after the thread does an inferior function call.
Therefore, make the thread_suspend_state member private
(thread_info::suspend becomes thread_info::m_suspend), and add getters /
setters for all of its fields:
- pending wait status
- stop signal
- stop reason
- stop pc
For the pending wait status, add the additional has_pending_waitstatus
and clear_pending_waitstatus methods.
I think this makes the thread_info interface a bit nicer, because we
now access the fields as:
thread->stop_pc ()
rather than
thread->suspend.stop_pc
The stop_pc field being in the `suspend` structure is an implementation
detail of thread_info that callers don't need to be aware of.
For the backup / restore of the thread_suspend_state structure, add
save_suspend_to and restore_suspend_from methods. You might wonder why
`save_suspend_to`, as opposed to a simple getter like
thread_suspend_state &suspend ();
I want to make it clear that this is to be used only for backing up and
restoring the suspend state, _not_ to access fields like:
thread->suspend ()->stop_pc
Adding some getters / setters allows adding some assertions. I find
that this helps understand how things are supposed to work. Add:
- When getting the pending status (pending_waitstatus method), ensure
that there is a pending status.
- When setting a pending status (set_pending_waitstatus method), ensure
there is no pending status.
There is one case I found where this wasn't true - in
remote_target::process_initial_stop_replies - which needed adjustments
to respect that contract. I think it's because
process_initial_stop_replies is kind of (ab)using the
thread_info::suspend::waitstatus to store some statuses temporarily, for
its internal use (statuses it doesn't intent on leaving pending).
process_initial_stop_replies pulls out stop replies received during the
initial connection using target_wait. It always stores the received
event in `evthread->suspend.waitstatus`. But it only sets
waitstatus_pending_p, if it deems the event interesting enough to leave
pending, to be reported to the core:
if (ws.kind != TARGET_WAITKIND_STOPPED
|| ws.value.sig != GDB_SIGNAL_0)
evthread->suspend.waitstatus_pending_p = 1;
It later uses this flag a bit below, to choose which thread to make the
"selected" one:
if (selected == NULL
&& thread->suspend.waitstatus_pending_p)
selected = thread;
And ultimately that's used if the user-visible mode is all-stop, so that
we print the stop for that interesting thread:
/* In all-stop, we only print the status of one thread, and leave
others with their status pending. */
if (!non_stop)
{
thread_info *thread = selected;
if (thread == NULL)
thread = lowest_stopped;
if (thread == NULL)
thread = first;
print_one_stopped_thread (thread);
}
But in any case (all-stop or non-stop), print_one_stopped_thread needs
to access the waitstatus value of these threads that don't have a
pending waitstatus (those that had TARGET_WAITKIND_STOPPED +
GDB_SIGNAL_0). This doesn't work with the assertions I've
put.
So, change the code to only set the thread's wait status if it is an
interesting one that we are going to leave pending. If the thread
stopped due to a non-interesting event (TARGET_WAITKIND_STOPPED +
GDB_SIGNAL_0), don't store it. Adjust print_one_stopped_thread to
understand that if a thread has no pending waitstatus, it's because it
stopped with TARGET_WAITKIND_STOPPED + GDB_SIGNAL_0.
The call to set_last_target_status also uses the pending waitstatus.
However, given that the pending waitstatus for the thread may have been
cleared in print_one_stopped_thread (and that there might not even be a
pending waitstatus in the first place, as explained above), it is no
longer possible to do it at this point. To fix that, move the call to
set_last_target_status in print_one_stopped_thread. I think this will
preserve the existing behavior, because set_last_target_status is
currently using the current thread's wait status. And the current
thread is the last one for which print_one_stopped_thread is called. So
by calling set_last_target_status in print_one_stopped_thread, we'll get
the same result. set_last_target_status will possibly be called
multiple times, but only the last call will matter. It just means
possibly more calls to set_last_target_status, but those are cheap.
Change-Id: Iedab9653238eaf8231abcf0baa20145acc8b77a7
A following patch will want to do things when a thread's resumed state
changes. Make the `resumed` field private (renamed to `m_resumed`) and
add a getter and a setter for it. The following patch in question will
therefore be able to add some code to the setter.
Change-Id: I360c48cc55a036503174313261ce4e757d795319
The threads that need a step-over are currently linked using an
hand-written intrusive doubly-linked list, so that seems a very good
candidate for intrusive_list, convert it.
For this, we have a use case of appending a list to another one (in
start_step_over). Based on the std::list and Boost APIs, add a splice
method. However, only support splicing the other list at the end of the
`this` list, since that's all we need.
Add explicit default assignment operators to
reference_to_pointer_iterator, which are otherwise implicitly deleted.
This is needed because to define thread_step_over_list_safe_iterator, we
wrap reference_to_pointer_iterator inside a basic_safe_iterator, and
basic_safe_iterator needs to be able to copy-assign the wrapped
iterator. The move-assignment operator is therefore not needed, only
the copy-assignment operator is. But for completeness, add both.
Change-Id: I31b2ff67c7b78251314646b31887ef1dfebe510c
Change inferior_list, the global list of inferiors, to use
intrusive_list. I think most other changes are somewhat obvious
fallouts from this change.
There is a small change in behavior in scoped_mock_context. Before this
patch, constructing a scoped_mock_context would replace the whole
inferior list with only the new mock inferior. Tests using two
scoped_mock_contexts therefore needed to manually link the two inferiors
together, as the second scoped_mock_context would bump the first mock
inferior from the thread list. With this patch, a scoped_mock_context
adds its mock inferior to the inferior list on construction, and removes
it on destruction. This means that tests run with mock inferiors in the
inferior list in addition to any pre-existing inferiors (there is always
at least one). There is no possible pid clash problem, since each
scoped mock inferior uses its own process target, and pids are per
process target.
Co-Authored-By: Simon Marchi <simon.marchi@efficios.com>
Change-Id: I7eb6a8f867d4dcf8b8cd2dcffd118f7270756018
While working around, I noticed that the last parameter of
maybe_software_singlestep is never used. This path removes
it.
Built on x86_64-linux-gnu and riscv64-linux-gnu.
gdb/ChangeLog:
* infrun.c (maybe_software_singlestep): Remove unused PC
parameter.
(resume_1): Update calls to maybe_software_singlestep.
do_target_wait has a wait_ptid parameter, to filter what ptid we wait
on. The sole caller of do_target_wait passes minus_one_ptid, meaning
"all ptids". So in practice, this parameter is not needed, remove it.
gdb/ChangeLog:
* infrun.c (do_target_wait): Remove wait_ptid parameter.
(fetch_inferior_event): Adjust.
Change-Id: I54119beb43db678e4b2081dc490f89e7ff878e74
When trying to attach to a pthread process on a Linux system with glibc 2.33,
we get:
$ ./gdb -q -nx --data-directory=data-directory -p 1472010
Attaching to process 1472010
[New LWP 1472013]
[New LWP 1472014]
[New LWP 1472015]
Error while reading shared library symbols for /usr/lib/libpthread.so.0:
Cannot find user-level thread for LWP 1472015: generic error
0x00007ffff6d3637f in poll () from /usr/lib/libc.so.6
(gdb)
When attaching to a process (or handling a fork child, an operation very
similar to attaching), GDB reads the shared library list from the
process. For each shared library (if "set auto-solib-add" is on), it
reads its symbols and calls the "new_objfile" observable.
The libthread-db code monitors this observable, and if it sees an
objfile named somewhat like "libpthread.so" go by, it tries to load
libthread_db.so in the GDB process itself. libthread_db knows how to
navigate libpthread's data structures to get information about the
existing threads.
To locate these data structures, libthread_db calls ps_pglobal_lookup
(implemented in proc-service.c), passing in a symbol name and expecting
an address in return.
Before glibc 2.33, libthread_db always asked for symbols found in
libpthread. There was no ordering problem: since we were always trying
to load libthread_db in reaction to processing libpthread (and reading
in its symbols) and libthread_db only asked symbols from libpthread, the
requested symbols could always be found. Starting with glibc 2.33,
libthread_db now asks for a symbol name that can be found in
/lib/ld-linux-x86-64.so.2 (_rtld_global). And the ordering in which GDB
reads the shared libraries from the inferior when attaching is
unfortunate, in that libpthread is processed before ld-linux. So when
loading libthread_db in reaction to processing libpthread, and
libthread_db requests the symbol that is from ld-linux, GDB is not yet
able to supply it.
That problematic symbol lookup happens in the thread_from_lwp function,
when we call td_ta_map_lwp2thr_p, and an exception is thrown at this
point:
#0 0x00007ffff6681012 in __cxxabiv1::__cxa_throw (obj=0x60e000006100, tinfo=0x555560033b50 <typeinfo for gdb_exception_error>, dest=0x55555d9404bc <gdb_exception_error::~gdb_exception_error()>) at /build/gcc/src/gcc/libstdc++-v3/libsupc++/eh_throw.cc:78
#1 0x000055555e5d3734 in throw_it(return_reason, errors, const char *, typedef __va_list_tag __va_list_tag *) (reason=RETURN_ERROR, error=GENERIC_ERROR, fmt=0x55555f0c5360 "Cannot find user-level thread for LWP %ld: %s", ap=0x7fffffffaae0) at /home/simark/src/binutils-gdb/gdbsupport/common-exceptions.cc:200
#2 0x000055555e5d37d4 in throw_verror (error=GENERIC_ERROR, fmt=0x55555f0c5360 "Cannot find user-level thread for LWP %ld: %s", ap=0x7fffffffaae0) at /home/simark/src/binutils-gdb/gdbsupport/common-exceptions.cc:208
#3 0x000055555e0b0ed2 in verror (string=0x55555f0c5360 "Cannot find user-level thread for LWP %ld: %s", args=0x7fffffffaae0) at /home/simark/src/binutils-gdb/gdb/utils.c:171
#4 0x000055555e5e898a in error (fmt=0x55555f0c5360 "Cannot find user-level thread for LWP %ld: %s") at /home/simark/src/binutils-gdb/gdbsupport/errors.cc:43
#5 0x000055555d06b4bc in thread_from_lwp (stopped=0x617000035d80, ptid=...) at /home/simark/src/binutils-gdb/gdb/linux-thread-db.c:418
#6 0x000055555d07040d in try_thread_db_load_1 (info=0x60c000011140) at /home/simark/src/binutils-gdb/gdb/linux-thread-db.c:912
#7 0x000055555d071103 in try_thread_db_load (library=0x55555f0c62a0 "libthread_db.so.1", check_auto_load_safe=false) at /home/simark/src/binutils-gdb/gdb/linux-thread-db.c:1014
#8 0x000055555d072168 in try_thread_db_load_from_sdir () at /home/simark/src/binutils-gdb/gdb/linux-thread-db.c:1091
#9 0x000055555d072d1c in thread_db_load_search () at /home/simark/src/binutils-gdb/gdb/linux-thread-db.c:1146
#10 0x000055555d07365c in thread_db_load () at /home/simark/src/binutils-gdb/gdb/linux-thread-db.c:1203
#11 0x000055555d07373e in check_for_thread_db () at /home/simark/src/binutils-gdb/gdb/linux-thread-db.c:1246
#12 0x000055555d0738ab in thread_db_new_objfile (objfile=0x61300000c0c0) at /home/simark/src/binutils-gdb/gdb/linux-thread-db.c:1275
#13 0x000055555bd10740 in std::__invoke_impl<void, void (*&)(objfile*), objfile*> (__f=@0x616000068d88: 0x55555d073745 <thread_db_new_objfile(objfile*)>) at /usr/include/c++/10.2.0/bits/invoke.h:60
#14 0x000055555bd02096 in std::__invoke_r<void, void (*&)(objfile*), objfile*> (__fn=@0x616000068d88: 0x55555d073745 <thread_db_new_objfile(objfile*)>) at /usr/include/c++/10.2.0/bits/invoke.h:153
#15 0x000055555bce0392 in std::_Function_handler<void (objfile*), void (*)(objfile*)>::_M_invoke(std::_Any_data const&, objfile*&&) (__functor=..., __args#0=@0x7fffffffb4a0: 0x61300000c0c0) at /usr/include/c++/10.2.0/bits/std_function.h:291
#16 0x000055555d3595c0 in std::function<void (objfile*)>::operator()(objfile*) const (this=0x616000068d88, __args#0=0x61300000c0c0) at /usr/include/c++/10.2.0/bits/std_function.h:622
#17 0x000055555d356b7f in gdb::observers::observable<objfile*>::notify (this=0x555566727020 <gdb::observers::new_objfile>, args#0=0x61300000c0c0) at /home/simark/src/binutils-gdb/gdb/../gdbsupport/observable.h:106
#18 0x000055555da3f228 in symbol_file_add_with_addrs (abfd=0x61200001ccc0, name=0x6190000d9090 "/usr/lib/libpthread.so.0", add_flags=..., addrs=0x7fffffffbc10, flags=..., parent=0x0) at /home/simark/src/binutils-gdb/gdb/symfile.c:1131
#19 0x000055555da3f763 in symbol_file_add_from_bfd (abfd=0x61200001ccc0, name=0x6190000d9090 "/usr/lib/libpthread.so.0", add_flags=<error reading variable: Cannot access memory at address 0xffffffffffffffb0>, addrs=0x7fffffffbc10, flags=<error reading variable: Cannot access memory at address 0xffffffffffffffc0>, parent=0x0) at /home/simark/src/binutils-gdb/gdb/symfile.c:1167
#20 0x000055555d95f9fa in solib_read_symbols (so=0x6190000d8e80, flags=...) at /home/simark/src/binutils-gdb/gdb/solib.c:681
#21 0x000055555d96233d in solib_add (pattern=0x0, from_tty=0, readsyms=1) at /home/simark/src/binutils-gdb/gdb/solib.c:987
#22 0x000055555d93646e in enable_break (info=0x608000008f20, from_tty=0) at /home/simark/src/binutils-gdb/gdb/solib-svr4.c:2238
#23 0x000055555d93cfc0 in svr4_solib_create_inferior_hook (from_tty=0) at /home/simark/src/binutils-gdb/gdb/solib-svr4.c:3049
#24 0x000055555d96610d in solib_create_inferior_hook (from_tty=0) at /home/simark/src/binutils-gdb/gdb/solib.c:1195
#25 0x000055555cdee318 in post_create_inferior (from_tty=0) at /home/simark/src/binutils-gdb/gdb/infcmd.c:318
#26 0x000055555ce00e6e in setup_inferior (from_tty=0) at /home/simark/src/binutils-gdb/gdb/infcmd.c:2439
#27 0x000055555ce59c34 in handle_one (event=...) at /home/simark/src/binutils-gdb/gdb/infrun.c:4887
#28 0x000055555ce5cd00 in stop_all_threads () at /home/simark/src/binutils-gdb/gdb/infrun.c:5064
#29 0x000055555ce7f0da in stop_waiting (ecs=0x7fffffffd170) at /home/simark/src/binutils-gdb/gdb/infrun.c:8006
#30 0x000055555ce67f5c in handle_signal_stop (ecs=0x7fffffffd170) at /home/simark/src/binutils-gdb/gdb/infrun.c:6062
#31 0x000055555ce63653 in handle_inferior_event (ecs=0x7fffffffd170) at /home/simark/src/binutils-gdb/gdb/infrun.c:5727
#32 0x000055555ce4f297 in fetch_inferior_event () at /home/simark/src/binutils-gdb/gdb/infrun.c:4105
#33 0x000055555cdbe3bf in inferior_event_handler (event_type=INF_REG_EVENT) at /home/simark/src/binutils-gdb/gdb/inf-loop.c:42
#34 0x000055555d018047 in handle_target_event (error=0, client_data=0x0) at /home/simark/src/binutils-gdb/gdb/linux-nat.c:4060
#35 0x000055555e5ea77e in handle_file_event (file_ptr=0x60600008b1c0, ready_mask=1) at /home/simark/src/binutils-gdb/gdbsupport/event-loop.cc:575
#36 0x000055555e5eb09c in gdb_wait_for_event (block=0) at /home/simark/src/binutils-gdb/gdbsupport/event-loop.cc:701
#37 0x000055555e5e8d19 in gdb_do_one_event () at /home/simark/src/binutils-gdb/gdbsupport/event-loop.cc:212
#38 0x000055555dd6e0d4 in wait_sync_command_done () at /home/simark/src/binutils-gdb/gdb/top.c:528
#39 0x000055555dd6e372 in maybe_wait_sync_command_done (was_sync=0) at /home/simark/src/binutils-gdb/gdb/top.c:545
#40 0x000055555d0ec7c8 in catch_command_errors (command=0x55555ce01bb8 <attach_command(char const*, int)>, arg=0x7fffffffe28d "1472010", from_tty=1, do_bp_actions=false) at /home/simark/src/binutils-gdb/gdb/main.c:452
#41 0x000055555d0f03ad in captured_main_1 (context=0x7fffffffdd10) at /home/simark/src/binutils-gdb/gdb/main.c:1149
#42 0x000055555d0f1239 in captured_main (data=0x7fffffffdd10) at /home/simark/src/binutils-gdb/gdb/main.c:1232
#43 0x000055555d0f1315 in gdb_main (args=0x7fffffffdd10) at /home/simark/src/binutils-gdb/gdb/main.c:1257
#44 0x000055555bb70cf9 in main (argc=7, argv=0x7fffffffde88) at /home/simark/src/binutils-gdb/gdb/gdb.c:32
The exception is caught here:
#0 __cxxabiv1::__cxa_begin_catch (exc_obj_in=0x60e0000060e0) at /build/gcc/src/gcc/libstdc++-v3/libsupc++/eh_catch.cc:84
#1 0x000055555d95fded in solib_read_symbols (so=0x6190000d8e80, flags=...) at /home/simark/src/binutils-gdb/gdb/solib.c:689
#2 0x000055555d96233d in solib_add (pattern=0x0, from_tty=0, readsyms=1) at /home/simark/src/binutils-gdb/gdb/solib.c:987
#3 0x000055555d93646e in enable_break (info=0x608000008f20, from_tty=0) at /home/simark/src/binutils-gdb/gdb/solib-svr4.c:2238
#4 0x000055555d93cfc0 in svr4_solib_create_inferior_hook (from_tty=0) at /home/simark/src/binutils-gdb/gdb/solib-svr4.c:3049
#5 0x000055555d96610d in solib_create_inferior_hook (from_tty=0) at /home/simark/src/binutils-gdb/gdb/solib.c:1195
#6 0x000055555cdee318 in post_create_inferior (from_tty=0) at /home/simark/src/binutils-gdb/gdb/infcmd.c:318
#7 0x000055555ce00e6e in setup_inferior (from_tty=0) at /home/simark/src/binutils-gdb/gdb/infcmd.c:2439
#8 0x000055555ce59c34 in handle_one (event=...) at /home/simark/src/binutils-gdb/gdb/infrun.c:4887
#9 0x000055555ce5cd00 in stop_all_threads () at /home/simark/src/binutils-gdb/gdb/infrun.c:5064
#10 0x000055555ce7f0da in stop_waiting (ecs=0x7fffffffd170) at /home/simark/src/binutils-gdb/gdb/infrun.c:8006
#11 0x000055555ce67f5c in handle_signal_stop (ecs=0x7fffffffd170) at /home/simark/src/binutils-gdb/gdb/infrun.c:6062
#12 0x000055555ce63653 in handle_inferior_event (ecs=0x7fffffffd170) at /home/simark/src/binutils-gdb/gdb/infrun.c:5727
#13 0x000055555ce4f297 in fetch_inferior_event () at /home/simark/src/binutils-gdb/gdb/infrun.c:4105
#14 0x000055555cdbe3bf in inferior_event_handler (event_type=INF_REG_EVENT) at /home/simark/src/binutils-gdb/gdb/inf-loop.c:42
#15 0x000055555d018047 in handle_target_event (error=0, client_data=0x0) at /home/simark/src/binutils-gdb/gdb/linux-nat.c:4060
#16 0x000055555e5ea77e in handle_file_event (file_ptr=0x60600008b1c0, ready_mask=1) at /home/simark/src/binutils-gdb/gdbsupport/event-loop.cc:575
#17 0x000055555e5eb09c in gdb_wait_for_event (block=0) at /home/simark/src/binutils-gdb/gdbsupport/event-loop.cc:701
#18 0x000055555e5e8d19 in gdb_do_one_event () at /home/simark/src/binutils-gdb/gdbsupport/event-loop.cc:212
#19 0x000055555dd6e0d4 in wait_sync_command_done () at /home/simark/src/binutils-gdb/gdb/top.c:528
#20 0x000055555dd6e372 in maybe_wait_sync_command_done (was_sync=0) at /home/simark/src/binutils-gdb/gdb/top.c:545
#21 0x000055555d0ec7c8 in catch_command_errors (command=0x55555ce01bb8 <attach_command(char const*, int)>, arg=0x7fffffffe28d "1472010", from_tty=1, do_bp_actions=false) at /home/simark/src/binutils-gdb/gdb/main.c:452
#22 0x000055555d0f03ad in captured_main_1 (context=0x7fffffffdd10) at /home/simark/src/binutils-gdb/gdb/main.c:1149
#23 0x000055555d0f1239 in captured_main (data=0x7fffffffdd10) at /home/simark/src/binutils-gdb/gdb/main.c:1232
#24 0x000055555d0f1315 in gdb_main (args=0x7fffffffdd10) at /home/simark/src/binutils-gdb/gdb/main.c:1257
#25 0x000055555bb70cf9 in main (argc=7, argv=0x7fffffffde88) at /home/simark/src/binutils-gdb/gdb/gdb.c:32
Catching the exception at this point means that the thread_db_info
object for this inferior will be left in place, despite the failure to
load libthread_db. This means that there won't be further attempts at
loading libthread_db, because thread_db_load will think that
libthread_db is already loaded for this inferior and will always exit
early. To fix this, add a try/catch around calling try_thread_db_load_1
in try_thread_db_load, such that if some exception is thrown while
trying to load libthread_db, we reset / delete the thread_db_info for
that inferior. That alone makes attach work fine again, because
check_for_thread_db is called again in the thread_db_inferior_created
observer (that happens after we learned about all shared libraries and
their symbols), and libthread_db is successfully loaded then.
When attaching, I think that the inferior_created observer is a good
place to try to load libthread_db: it is called once everything has
stabilized, when we learned about all shared libraries.
The only problem then is that when we first try (and fail) to load
libthread_db, in reaction to learning about libpthread, we show this
warning:
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
This is misleading, because we do succeed in loading it later. So when
attaching, I think we shouldn't try to load libthread_db in reaction to
the new_objfile events, we should wait until we have learned about all
shared libraries (using the inferior_created observable). To do so, add
an `in_initial_library_scan` flag to struct inferior. This flag is used
to postpone loading libthread_db if we are attaching or handling a fork
child.
When debugging remotely with GDBserver, the same problem happens, except
that the qSymbol mechanism (allowing the remote side to ask GDB for
symbols values) is involved. The fix there is the same idea, we make
GDB wait until all shared libraries and their symbols are known before
sending out a qSymbol packet. This way, we never present the remote
side a state where libpthread.so's symbols are known but ld-linux's
symbols aren't.
gdb/ChangeLog:
* inferior.h (class inferior) <in_initial_library_scan>: New.
* infcmd.c (post_create_inferior): Set in_initial_library_scan.
* infrun.c (follow_fork_inferior): Likewise.
* linux-thread-db.c (try_thread_db_load): Catch exception thrown
by try_thread_db_load_1
(thread_db_load): Return early if in_initial_library_scan is
set.
* remote.c (remote_new_objfile): Return early if
in_initial_library_scan is set.
Change-Id: I7a279836cfbb2b362b4fde11b196b4aab82f5efb
There is no default method for
gdbarch_displaced_step_restore_all_in_ptid, so calling it
unconditionally for fork events triggered an assertion failure on
platforms that do not support displaced stepping. To fix, only invoke
the method if the gdbarch supports displaced stepping.
Note that not all gdbarches support both displaced stepping and fork
events, so gdbarch validation does not require
gdbarch_displaced_step_restore_all_in_ptid for any gdbarch supporting
displaced stepping. However, the internal assertion in
gdbarch_displaced_step_restore_all_in_ptid should catch any gdbarches
which do support both but fail to provide this method.
gdb/ChangeLog:
* infrun.c (handle_inferior_event): Only call
gdbarch_displaced_step_restore_all_in_ptid if
gdbarch_supports_displaced_stepping is true.
I spotted some indentation issues where we had some spaces followed by
tabs at beginning of line, that I wanted to fix. So while at it, I did
a quick grep to find and fix all I could find.
gdb/ChangeLog:
* Fix tab after space indentation issues throughout.
Change-Id: I1acb414dd9c593b474ae2b8667496584df4316fd
Same idea as previous patch, but for add_info_alias.
gdb/ChangeLog:
* command.h (add_info_alias): Accept target as
cmd_list_element. Update callers.
Change-Id: If830d423364bf42d7bea5ac4dd3a81adcfce6f7a
On "exec", some targets need to unpush themselves from the inferior,
and do some bookkeeping, like forgetting the data associated to the
exec'ing inferior.
One such example is the thread-db target. It does so in
a special case in thread_db_target::wait, just before returning the
TARGET_WAITKIND_EXECD event to its caller.
We have another such case in the context of rocm-gdb [1], where the
"rocm" target is pushed on top of the linux-nat target. When an exec
happens, we want to unpush the rocm target from the exec'ing inferior to
close some file descriptors that refer to the pre-exec address space and
forget about that inferior. We then want to push the target on the
inferior in which execution continues, to open the file descriptors for
the post-exec address space.
I think that a good way to address this cleanly is to do all this in the
target_ops::follow_exec implementations. Make the
process_stratum_target::follow_exec implementation have the default
behavior of pushing itself to the new inferior's target stack (if
execution continues in a new inferior) and add the initial thread.
remote_target::follow_exec is an example of process target that wants to
do a bit more than the default behavior. So it calls
process_stratum_target::follow_exec first and does the extra work
second.
linux-thread-db (a non-process target) implements follow_exec to do some
bookeeping (forget about that process' data), before handing down the
event down to the process target (which hits
process_stratum_target::follow_exec).
gdb/ChangeLog:
* target.h (struct target_ops) <follow_exec>: Add ptid_t
parameter.
(target_follow_exec): Likewise.
* target.c (target_follow_exec): Add ptid_t parameter.
* infrun.c (follow_exec): Adjust call to target_follow_exec,
don't push target nor create thread.
* linux-thread-db.c (class thread_db_target) <follow_exec>: New.
(thread_db_target::wait): Just return on TARGET_WAITKIND_EXECD.
(thread_db_target::follow_exec): New.
* remote.c (class remote_target) <follow_exec>: Add ptid_t parameter.
(remote_target::follow_exec): Call
process_stratum_target::follow_exec.
* target-delegates.c: Re-generate.
Change-Id: I3f96d0ba3ea0dde6540b7e1b4d5cdb01635088c8
target_follow_exec is currently only called in the "follow-exec-mode ==
new" branch of follow_exec, not the "follow-exec-mode == same" branch.
I think it would make sense to call it regardless of the mode to let
targets do some necessary handling.
This is needed in the context of rocm-gdb [1], where a target is pushed
on top of the linux-nat target. On exec, it needs to do some
bookkeeping, close some file descriptors / handles that were related to
the process pre-exec and open some new ones for the process post-exec.
However, by looking at the only in-tree implementation of
target_ops::follow_exec, remote_target::follow_exec, I found that it
would be useful for the extended-remote target too, to align its
behavior with native debugging (although I think that behavior is not
very user-friendly, see PR 27745 [2]).
Using two programs, one (let's call it "execer") that execs the other
(let's call it "execee"), with native:
$ ./gdb -q -nx --data-directory=data-directory ./execer
Reading symbols from ./execer...
(gdb) r
Starting program: /home/simark/build/binutils-gdb/gdb/execer
I am execer
process 1495622 is executing new program: /home/simark/build/binutils-gdb/gdb/execee
I am execee
[Inferior 1 (process 1495622) exited normally]
(gdb) r
Starting program: /home/simark/build/binutils-gdb/gdb/execee
I am execee
[Inferior 1 (process 1495626) exited normally]
And now with gdbserver (some irrelevant output lines removed for brevity):
$ ./gdbserver --once --multi :1234
...
$ ./gdb -q -nx --data-directory=data-directory ./execer -ex "set remote exec-file /home/simark/build/binutils-gdb/gdb/execer" -ex "tar ext :1234"
Reading symbols from ./execer...
Remote debugging using :1234
(gdb) r
Starting program: /home/simark/build/binutils-gdb/gdb/execer
process 1495724 is executing new program: /home/simark/build/binutils-gdb/gdb/execee
[Inferior 1 (process 1495724) exited normally]
(gdb) r
`target:/home/simark/build/binutils-gdb/gdb/execee' has disappeared; keeping its symbols.
Starting program: target:/home/simark/build/binutils-gdb/gdb/execee
warning: Build ID mismatch between current exec-file target:/home/simark/build/binutils-gdb/gdb/execee
and automatically determined exec-file target:/home/simark/build/binutils-gdb/gdb/execer
exec-file-mismatch handling is currently "ask"
Reading /home/simark/build/binutils-gdb/gdb/execer from remote target...
Load new symbol table from "target:/home/simark/build/binutils-gdb/gdb/execer"? (y or n)
When handling the exec, GDB updates the exec-file of the inferior to be
the execee. This means that a subsequent "run" will run the execee, not
the original executable (execer).
remote_target::follow_exec is meant to update the "remote exec-file",
which is the file on the remote system that will be executed if you
"run" the inferior, to the execee as well. However, this is not called
when follow-exec-mode is same, because target_follow_exec is not called
in this branch. As a result, GDB thinks the inferior is executing
execee but the remote side is really executing execer, hence the
mismatch message.
By calling target_follow_exec in the "same" branch of the follow_exec
function, we ensure that everybody agrees, and we get the same behavior
with the extended-remote target as we get with the native target, the
execee is executed on the second run:
$ ./gdbserver --once --multi :1234
...
$ ./gdb -q -nx --data-directory=data-directory ./execer -ex "set remote exec-file /home/simark/build/binutils-gdb/gdb/execer" -ex "tar ext :1234"
Reading symbols from ./execer...
Remote debugging using :1234
(gdb) r
Starting program: /home/simark/build/binutils-gdb/gdb/execer
process 1501445 is executing new program: /home/simark/build/binutils-gdb/gdb/execee
[Inferior 1 (process 1501445) exited normally]
(gdb) r
`target:/home/simark/build/binutils-gdb/gdb/execee' has disappeared; keeping its symbols.
Starting program: target:/home/simark/build/binutils-gdb/gdb/execee
[Inferior 1 (process 1501447) exited normally]
(gdb)
This scenario is tested in gdb.base/foll-exec-mode.exp, and in fact this
patch fixes the test for me when using
--target_board=native-extended-gdbserver.
gdb/ChangeLog:
* infrun.c (follow_exec): Call target_follow_fork when
follow-exec-mode is same.
* target.h (target_follow_fork): Improve doc.
[1] https://github.com/ROCm-Developer-Tools/ROCgdb
[2] https://sourceware.org/bugzilla/show_bug.cgi?id=27745
Change-Id: I4ee84a875e39bf3f8eaf3e6789a4bfe23a2a430e
These two variables:
struct regcache *regcache = get_thread_regcache (tp);
const address_space *aspace = regcache->aspace ();
are only needed inside the "if". Getting a thread's regcache is a
somewhat expensive operation, so it's good to avoid it if not necessary.
Move the variable declarations and their initialization to the "if"
scope.
gdb/ChangeLog:
* infrun.c (save_waitstatus): Move variables to inner scope.
Change-Id: Ief1463728755b4dcc142c0a0a76896e9d594ae84
Give a name to each observer, this will help produce more meaningful
debug message.
gdbsupport/ChangeLog:
* observable.h (class observable) <struct observer> <observer>:
Add name parameter.
<name>: New field.
<attach>: Add name parameter, update all callers.
Change-Id: Ie0cc4664925215b8d2b09e026011b7803549fba0
