For the BTS recording format, we sometimes get a FROM->TO record where the
FROM address lies in the kernel and the TO address lies in user space at
whatever address the user process was resumed.
GDB has a heuristic to filter out such records based on looking at the most
significant bit in the PC. This works fine for 64-bit systems but it doesn't
always work for 32-bit systems. Libraries that are loaded at fairly high
addresses might be mistaken for kernel code and branches inside the library
are filtered out.
Change the heuristic to (again heuristically) try to determine the lowest
address in kernel space. Any PC that is smaller than that should be in
user space.
On today's systems, there should be a symbol "_text" at that address.
Read /proc/kallsyms and search for that symbol.
It is not guaranteed that /proc/kallsyms is readable on all systems. On
64-bit systems, we fall back to check the most significant bit. On 32-bit
systems, we refrain from filtering out addresses.
The filtering should really be done by the kernel. And it soon will be:
https://lkml.org/lkml/2015/8/31/212.
gdb/
* nat/linux-btrace.h (struct btrace_target_info) <ptr_bits>: Remove.
* nat/linux-btrace.c: Include filestuff.h and inttypes.h.
Remove include of sys/utsname.h.
(linux_determine_kernel_ptr_bits): Remove.
(linux_determine_kernel_start): New.
(perf_event_is_kernel_addr): Remove tinfo argument. Update users.
Update check.
(perf_event_skip_bts_record): Remove tinfo argument. Update users.
(linux_enable_bts, linux_enable_pt): Remove tinfo->ptr_bits
initialization.
* x86-linux-nat.c (x86_linux_enable_btrace): Remove ptr_bits
assignment.
gdbserver/
* linux-low.c (linux_low_enable_btrace): Remove.
(linux_target_ops): Replace linux_low_enable_btrace with
linux_enable_btrace.
The Linux target and gdbserver now check the siginfo si_code
reported on a SIGTRAP to detect whether the trap indicates
a software breakpoint was hit.
Unfortunately, on Cell/B.E., the kernel uses an si_code value
of TRAP_BRKPT when a SW breakpoint was hit in PowerPC code,
but a si_code value of SI_KERNEL when a SW breakpoint was
hit in SPU code.
This patch updates Linux target and gdbserver to accept both
si_code values to indicate SW breakpoint on PowerPC.
ChangeLog:
* nat/linux-ptrace.h (GDB_ARCH_TRAP_BRKPT): Replace by ...
(GDB_ARCH_IS_TRAP_BRKPT): ... this. Add __powerpc__ case.
* linux-nat.c (check_stopped_by_breakpoint): Use
GDB_ARCH_IS_TRAP_BRKPT instead of GDB_ARCH_TRAP_BRKPT.
gdbserver/ChangeLog:
* linux-low.c (check_stopped_by_breakpoint): Use
GDB_ARCH_IS_TRAP_BRKPT instead of GDB_ARCH_TRAP_BRKPT.
In all-stop mode, if the current thread disappears while stopping all
threads, gdbserver calls set_desired_thread(0) ['0' means "I want the
continue thread"] which just picks the first thread in the list.
This looks like a dangerous thing to do. GDBserver continues
processing whatever it was doing, but to the wrong thread. If
debugging more than one process, we may even pick the wrong process.
Instead, GDBserver should detect the situation and bail out of
whatever is was doing.
The backends used to pay attention to the set 'cont_thread' (the Hc
thread, used in the old way to resume threads, before vCont), but all
such 'cont_thread' checks have been eliminated meanwhile. The
remaining implicit dependencies that I found on there being a selected
thread in the backends are in the Ctrl-C handling, which some backends
use as thread to send a signal to. Even that seems to me to be better
handled by always using the first thread in the list or by using the
signal_pid PID.
In order to make this a systematic approach, I'm making
set_desired_thread never fallback to a random thread, and instead end
up with current_thread == NULL, like already done in non-stop mode.
Then I updated all callers to handle the situation.
I stumbled on this while fixing other bugs exposed by
gdb.threads/fork-plus-threads.exp test. The problems I saw were fixed
in a different way, but in any case, I think the potential for
problems is more or less obvious, and the resulting code looks a bit
less magical to me.
Tested on x86-64 Fedora 20, w/ native-extended-gdbserver board.
gdb/gdbserver/ChangeLog:
2015-08-21 Pedro Alves <palves@redhat.com>
* linux-low.c (wait_for_sigstop): Always switch to no thread
selected if the previously current thread dies.
* lynx-low.c (lynx_request_interrupt): Use the first thread's
process instead of the current thread's.
* remote-utils.c (input_interrupt): Don't check if there's no
current thread.
* server.c (gdb_read_memory, gdb_write_memory): If setting the
current thread to the general thread fails, error out.
(handle_qxfer_auxv, handle_qxfer_libraries)
(handle_qxfer_libraries_svr4, handle_qxfer_siginfo)
(handle_qxfer_spu, handle_qxfer_statictrace, handle_qxfer_fdpic)
(handle_query): Check if there's a thread selected instead of
checking whether there's any thread in the thread list.
(handle_qxfer_threads, handle_qxfer_btrace)
(handle_qxfer_btrace_conf): Don't error out early if there's no
thread in the thread list.
(handle_v_cont, myresume): Don't set the current thread to the
continue thread.
(process_serial_event) <Hg handling>: Also set thread_id if the
previous general thread is still alive.
(process_serial_event) <g/G handling>: If setting the current
thread to the general thread fails, error out.
* spu-low.c (spu_resume, spu_request_interrupt): Use the first
thread's lwp instead of the current thread's.
* target.c (set_desired_thread): If the desired thread was not
found, leave the current thread pointing to NULL. Return an int
(boolean) indicating success.
* target.h (set_desired_thread): Change return type to int.
This tag allows debugging of MIPS position independent executables
and provides access to shared library information.
gdb/gdbserver/
* linux-low.c (get_r_debug): Handle DT_MIPS_RLD_MAP_REL.
gdb/
* solib-svr4.c (read_program_header): Add base_addr argument to
report the runtime address of the segment.
(find_program_interpreter): Update read_program_header call to pass
a NULL pointer for the new argument.
(scan_dyntag): Add ptr_addr argument to report the runtime address
of the tag payload.
(scan_dyntag_auxv): Likewise and use thew new base_addr argument of
read_program_header to get the base address of the dynamic segment.
(elf_locate_base): Update uses of scan_dyntag, scan_dyntag_auxv and
read_program_header.
(elf_locate_base): Scan for and handle DT_MIPS_RLD_MAP_REL.
While hacking on the fix for PR threads/18600 (Threads left stopped
after fork+thread spawn), I once saw its test (fork-plus-threads.exp)
FAIL against gdbserver because move_out_of_jump_pad_callback has a
gdb_breakpoint_here call, and the caller isn't making sure the current
thread points to the right thread. In the case I saw, the current
thread pointed to the wrong process, so gdb_breakpoint_here returned
the wrong answer. Unfortunately I didn't save logs. Still, seems
obvious enough and it should fix a potential occasional racy FAIL.
Tested on x86_64 Fedora 20.
gdb/gdbserver/ChangeLog:
2015-08-06 Pedro Alves <palves@redhat.com>
* linux-low.c (move_out_of_jump_pad_callback): Temporarily switch
the current thread.
Running gdbserver --debug under Valgrind shows:
==4803== Invalid read of size 4
==4803== at 0x432B62: linux_write_memory (linux-low.c:5320)
==4803== by 0x4143F7: write_inferior_memory (target.c:83)
==4803== by 0x415895: remove_memory_breakpoint (mem-break.c:362)
==4803== by 0x432EF5: linux_remove_point (linux-low.c:5460)
==4803== by 0x416319: delete_raw_breakpoint (mem-break.c:802)
==4803== by 0x4163F3: release_breakpoint (mem-break.c:842)
==4803== by 0x416477: delete_breakpoint_1 (mem-break.c:869)
==4803== by 0x4164EF: delete_breakpoint (mem-break.c:891)
==4803== by 0x416843: delete_gdb_breakpoint_1 (mem-break.c:1069)
==4803== by 0x4168D8: delete_gdb_breakpoint (mem-break.c:1098)
==4803== by 0x4134E3: process_serial_event (server.c:4051)
==4803== by 0x4138E4: handle_serial_event (server.c:4196)
==4803== Address 0x4c6b930 is 0 bytes inside a block of size 1 alloc'd
==4803== at 0x4A0645D: malloc (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==4803== by 0x4240C6: xmalloc (common-utils.c:43)
==4803== by 0x41439C: write_inferior_memory (target.c:80)
==4803== by 0x415895: remove_memory_breakpoint (mem-break.c:362)
==4803== by 0x432EF5: linux_remove_point (linux-low.c:5460)
==4803== by 0x416319: delete_raw_breakpoint (mem-break.c:802)
==4803== by 0x4163F3: release_breakpoint (mem-break.c:842)
==4803== by 0x416477: delete_breakpoint_1 (mem-break.c:869)
==4803== by 0x4164EF: delete_breakpoint (mem-break.c:891)
==4803== by 0x416843: delete_gdb_breakpoint_1 (mem-break.c:1069)
==4803== by 0x4168D8: delete_gdb_breakpoint (mem-break.c:1098)
==4803== by 0x4134E3: process_serial_event (server.c:4051)
==4803==
And:
==7272== Conditional jump or move depends on uninitialised value(s)
==7272== at 0x3615E48361: vfprintf (vfprintf.c:1634)
==7272== by 0x414E89: debug_vprintf (debug.c:60)
==7272== by 0x42800A: debug_printf (common-debug.c:35)
==7272== by 0x43937B: my_waitpid (linux-waitpid.c:149)
==7272== by 0x42D740: linux_wait_for_event_filtered (linux-low.c:2441)
==7272== by 0x42DADA: linux_wait_for_event (linux-low.c:2552)
==7272== by 0x42E165: linux_wait_1 (linux-low.c:2860)
==7272== by 0x42F5D8: linux_wait (linux-low.c:3453)
==7272== by 0x4144A4: mywait (target.c:107)
==7272== by 0x413969: handle_target_event (server.c:4214)
==7272== by 0x41A1A6: handle_file_event (event-loop.c:429)
==7272== by 0x41996D: process_event (event-loop.c:184)
gdb/ChangeLog:
2015-08-06 Pedro Alves <palves@redhat.com>
* nat/linux-waitpid.c (my_waitpid): Only print *status if waitpid
returned > 0.
gdb/gdbserver/ChangeLog:
2015-08-06 Pedro Alves <palves@redhat.com>
* linux-low.c (linux_write_memory): Rewrite debug output to avoid
reading beyond the passed in buffer length.
Ref: https://sourceware.org/ml/gdb-patches/2015-07/msg00868.html
This adds a test that has a multithreaded program have several threads
continuously fork, while another thread continuously steps over a
breakpoint.
This exposes several intertwined issues, which this patch addresses:
- When we're stopping and suspending threads, some thread may fork,
and we missed setting its suspend count to 1, like we do when a new
clone/thread is detected. When we next unsuspend threads, the fork
child's suspend count goes below 0, which is bogus and fails an
assertion.
- If a step-over is cancelled because a signal arrives, but then gdb
is not interested in the signal, we pass the signal straight back
to the inferior. However, we miss that we need to re-increment the
suspend counts of all other threads that had been paused for the
step-over. As a result, other threads indefinitely end up stuck
stopped.
- If a detach request comes in just while gdbserver is handling a
step-over (in the test at hand, this is GDB detaching the fork
child), gdbserver internal errors in stabilize_thread's helpers,
which assert that all thread's suspend counts are 0 (otherwise we
wouldn't be able to move threads out of the jump pads). The
suspend counts aren't 0 while a step-over is in progress, because
all threads but the one stepping past the breakpoint must remain
paused until the step-over finishes and the breakpoint can be
reinserted.
- Occasionally, we see "BAD - reinserting but not stepping." being
output (from within linux_resume_one_lwp_throw). That was because
GDB pokes memory while gdbserver is busy with a step-over, and that
suspends threads, and then re-resumes them with proceed_one_lwp,
which missed another reason to tell linux_resume_one_lwp that the
thread should be set back to stepping.
- In a couple places, we were resuming threads that are meant to be
suspended. E.g., when a vCont;c/s request for thread B comes in
just while gdbserver is stepping thread A past a breakpoint. The
resume for thread B must be deferred until the step-over finishes.
- The test runs with both "set detach-on-fork" on and off. When off,
it exercises the case of GDB detaching the fork child explicitly.
When on, it exercises the case of gdb resuming the child
explicitly. In the "off" case, gdb seems to exponentially become
slower as new inferiors are created. This is _very_ noticeable as
with only 100 inferiors gdb is crawling already, which makes the
test take quite a bit to run. For that reason, I've disabled the
"off" variant for now.
gdb/ChangeLog:
2015-08-06 Pedro Alves <palves@redhat.com>
* target/waitstatus.h (enum target_stop_reason)
<TARGET_STOPPED_BY_SINGLE_STEP>: New value.
gdb/gdbserver/ChangeLog:
2015-08-06 Pedro Alves <palves@redhat.com>
* linux-low.c (handle_extended_wait): Set the fork child's suspend
count if stopping and suspending threads.
(check_stopped_by_breakpoint): If stopped by trace, set the LWP's
stop reason to TARGET_STOPPED_BY_SINGLE_STEP.
(linux_detach): Complete an ongoing step-over.
(lwp_suspended_inc, lwp_suspended_decr): New functions. Use
throughout.
(resume_stopped_resumed_lwps): Don't resume a suspended thread.
(linux_wait_1): If passing a signal to the inferior after
finishing a step-over, unsuspend and re-resume all lwps. If we
see a single-step event but the thread should be continuing, don't
pass the trap to gdb.
(stuck_in_jump_pad_callback, move_out_of_jump_pad_callback): Use
internal_error instead of gdb_assert.
(enqueue_pending_signal): New function.
(check_ptrace_stopped_lwp_gone): Add debug output.
(start_step_over): Use internal_error instead of gdb_assert.
(complete_ongoing_step_over): New function.
(linux_resume_one_thread): Don't resume a suspended thread.
(proceed_one_lwp): If the LWP is stepping over a breakpoint, reset
it stepping.
gdb/testsuite/ChangeLog:
2015-08-06 Pedro Alves <palves@redhat.com>
* gdb.threads/forking-threads-plus-breakpoint.exp: New file.
* gdb.threads/forking-threads-plus-breakpoint.c: New file.
The tail end of linux_wait_1 isn't expecting that the select_event_lwp
machinery can pick a whole-process exit event to report to GDB. When
that happens, both gdb and gdbserver end up quite confused:
...
(gdb)
[Thread 24971.24971] #1 stopped.
0x0000003615a011f0 in ?? ()
c&
Continuing.
(gdb) [New Thread 24971.24981]
[New Thread 24983.24983]
[New Thread 24971.24982]
[Thread 24983.24983] #3 stopped.
0x0000003615ebc7cc in __libc_fork () at ../nptl/sysdeps/unix/sysv/linux/fork.c:130
130 pid = ARCH_FORK ();
[New Thread 24984.24984]
Error in re-setting breakpoint -16: PC register is not available
Error in re-setting breakpoint -17: PC register is not available
Error in re-setting breakpoint -18: PC register is not available
Error in re-setting breakpoint -19: PC register is not available
Error in re-setting breakpoint -24: PC register is not available
Error in re-setting breakpoint -25: PC register is not available
Error in re-setting breakpoint -26: PC register is not available
Error in re-setting breakpoint -27: PC register is not available
Error in re-setting breakpoint -28: PC register is not available
Error in re-setting breakpoint -29: PC register is not available
Error in re-setting breakpoint -30: PC register is not available
PC register is not available
(gdb)
gdb/gdbserver/ChangeLog:
2015-08-06 Pedro Alves <palves@redhat.com>
* linux-low.c (add_lwp): Set waitstatus to TARGET_WAITKIND_IGNORE.
(linux_thread_alive): Use lwp_is_marked_dead.
(extended_event_reported): Delete.
(linux_wait_1): Check if waitstatus is TARGET_WAITKIND_IGNORE
instead of extended_event_reported.
(mark_lwp_dead): Don't set the 'dead' flag. Store the waitstatus
as well.
(lwp_is_marked_dead): New function.
(lwp_running): Use lwp_is_marked_dead.
* linux-low.h: Delete 'dead' field, and update 'waitstatus's
comment.
The "extended event with waitstatus" debug output is unreachable, as
it is guarded by "if (!report_to_gdb)". If extended_event_reported is
true, then so is report_to_gdb. Move it to where we print why we're
reporting an event to GDB.
Also, the debug output currently tries to print the wrong struct
target_waitstatus.
gdb/gdbserver/ChangeLog:
2015-08-06 Pedro Alves <palves@redhat.com>
* linux-low.c (linux_wait_1): Move fork event output out of the
!report_to_gdb check. Pass event_child->waitstatus to
target_waitstatus_to_string instead of ourstatus.
This patch moves variable have_ptrace_getregset from linux-x86-low.c
to linux-low.c, so that arm can use it too.
gdb/gdbserver:
2015-08-04 Yao Qi <yao.qi@linaro.org>
* linux-x86-low.c (have_ptrace_getregset): Move it to ...
* linux-low.c: ... here.
* linux-low.h (have_ptrace_getregset): Declare it.
Running gdb.threads/fork-plus-threads.exp against gdbserver in
extended-remote mode, even though the test passes, we still see broken
behavior:
(gdb) PASS: gdb.threads/fork-plus-threads.exp: set detach-on-fork off
continue &
Continuing.
(gdb) PASS: gdb.threads/fork-plus-threads.exp: continue &
[New Thread 28092.28092]
[Thread 28092.28092] #2 stopped.
[New Thread 28094.28094]
[Inferior 2 (process 28092) exited normally]
[New Thread 28094.28105]
[New Thread 28094.28109]
...
[Thread 28174.28174] #18 stopped.
[New Thread 28185.28185]
[Inferior 10 (process 28174) exited normally]
[New Thread 28185.28196]
[Thread 28185.28185] #20 stopped.
Cannot remove breakpoints because program is no longer writable.
Further execution is probably impossible.
[Inferior 11 (process 28185) exited normally]
[Inferior 1 (process 28091) exited normally]
PASS: gdb.threads/fork-plus-threads.exp: reached breakpoint
info threads
No threads.
(gdb) PASS: gdb.threads/fork-plus-threads.exp: no threads left
info inferiors
Num Description Executable
* 1 <null> /home/pedro/gdb/mygit/build/gdb/testsuite/gdb.threads/fork-plus-threads
(gdb) PASS: gdb.threads/fork-plus-threads.exp: only inferior 1 left
All the "[Thread FOO] #NN stopped." above are bogus, as well as the
"Cannot remove breakpoints because program is no longer writable.",
which is a consequence.
The problem is that when we intercept a fork event, we should report
the event for the parent, only, and leave the child stopped, but not
report its stop event. GDB later decides whether to follow the parent
or the child. But because handle_extended_wait does not set the
child's last_status.kind to TARGET_WAITKIND_STOPPED, a
stop_all_threads/unstop_all_lwps sequence (e.g., from trying to access
memory) by mistake ends up queueing a SIGSTOP on the child, resuming
it, and then when that SIGSTOP is intercepted, because the LWP has
last_resume_kind set to resume_stop, gdbserver reports the stop to
GDB, as GDB_SIGNAL_0:
...
>>>> entering unstop_all_lwps
unstopping all lwps
proceed_one_lwp: lwp 1600
client wants LWP to remain 1600 stopped
proceed_one_lwp: lwp 1828
Client wants LWP 1828 to stop. Making sure it has a SIGSTOP pending
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Sending sigstop to lwp 1828
pc is 0x3615ebc7cc
Resuming lwp 1828 (continue, signal 0, stop expected)
continue from pc 0x3615ebc7cc
unstop_all_lwps done
sigchld_handler
<<<< exiting unstop_all_lwps
handling possible target event
>>>> entering linux_wait_1
linux_wait_1: [<all threads>]
my_waitpid (-1, 0x40000001)
my_waitpid (-1, 0x1): status(137f), 1828
LWFE: waitpid(-1, ...) returned 1828, ERRNO-OK
LLW: waitpid 1828 received Stopped (signal) (stopped)
pc is 0x3615ebc7cc
Expected stop.
LLW: resume_stop SIGSTOP caught for LWP 1828.1828.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
...
linux_wait_1 ret = LWP 1828.1828, 1, 0
<<<< exiting linux_wait_1
Writing resume reply for LWP 1828.1828:1
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Tested on x86_64 Fedora 20, extended-remote.
gdb/gdbserver/ChangeLog:
2015-07-30 Pedro Alves <palves@redhat.com>
* linux-low.c (handle_extended_wait): Set the child's last
reported status to TARGET_WAITKIND_STOPPED.
As the result of the previous patch, new_inferior is no longer used.
This patch is to remove it.
gdb/gdbserver:
2015-07-24 Yao Qi <yao.qi@linaro.org>
* linux-low.c (linux_create_inferior): Remove setting to
proc->priv->new_inferior.
(linux_attach): Likewise.
(linux_low_filter_event): Likewise.
* linux-low.h (struct process_info_private) <new_inferior>: Remove.
Nowadays, when --wrapper is used, GDBserver skips extra traps/stops
in the wrapper program, and stops at the first instruction of the
program to be debugged. However, GDBserver created target description
in the first stop of inferior, and the executable of the inferior
is the wrapper program rather than the program to be debugged. In
this way, the target description can be wrong if the architectures
of wrapper program and program to be debugged are different. This
is shown by some fails in gdb.server/wrapper.exp on buildbot.
We are testing i686-linux GDB (Fedora-i686) on an x86_64-linux box
(fedora-x86-64-4) in buildbot, such configuration causes fails in
gdb.server/wrapper.exp like this:
spawn /home/gdb-buildbot-2/fedora-x86-64-4/fedora-i686/build/gdb/testsuite/../../gdb/gdbserver/gdbserver --once --wrapper env TEST=1 -- :2346 /home/gdb-buildbot-2/fedora-x86-64-4/fedora-i686/build/gdb/testsuite/outputs/gdb.server/wrapper/wrapper
Process /home/gdb-buildbot-2/fedora-x86-64-4/fedora-i686/build/gdb/testsuite/outputs/gdb.server/wrapper/wrapper created; pid = 8795
Can't debug 64-bit process with 32-bit GDBserver
Exiting
target remote localhost:2346
localhost:2346: Connection timed out.
(gdb) FAIL: gdb.server/wrapper.exp: setting breakpoint at marker
See https://sourceware.org/ml/gdb-testers/2015-q3/msg01541.html
In this case, program to be debugged ("wrapper") is 32-bit but wrapper
program ("/usr/bin/env") is 64-bit, so GDBserver gets the 64-bit
target description instead of 32-bit.
The root cause of this problem is that GDBserver creates target
description too early, and the rationale of fix could be creating
target description once the GDBserver skips extra traps and inferior
stops at the first instruction of the program we want to debug. IOW,
when GDBserver skips extra traps, the inferior's tdesc is NULL, and
mywait and its callees shouldn't use inferior's tdesc, so in this
patch, we skip code that requires register access, see changes in
linux_resume_one_lwp_throw and need_step_over_p.
In linux_low_filter_event, if target description isn't initialised and
GDBserver attached the process, we create target description immediately,
because GDBserver don't have to skip extra traps for attach, IOW, it
makes no sense to use --attach and --wrapper together. Otherwise, the
process is launched by GDBserver, we keep the status pending, and return.
After GDBserver skipped extra traps in start_inferior, we call a
target_ops hook arch_setup to initialise target description there.
gdb/gdbserver:
2015-07-24 Yao Qi <yao.qi@linaro.org>
* linux-low.c (linux_arch_setup): New function.
(linux_low_filter_event): If proc->tdesc is NULL and
proc->attached is true, call the_low_target.arch_setup.
Otherwise, keep status pending, and return.
(linux_resume_one_lwp_throw): Don't call get_pc if
thread->while_stepping isn't NULL. Don't call
get_thread_regcache if proc->tdesc is NULL.
(need_step_over_p): Return 0 if proc->tdesc is NULL.
(linux_target_ops): Install arch_setup.
* server.c (start_inferior): Call the_target->arch_setup.
* target.h (struct target_ops) <arch_setup>: New field.
(target_arch_setup): New marco.
* lynx-low.c (lynx_target_ops): Update.
* nto-low.c (nto_target_ops): Update.
* spu-low.c (spu_target_ops): Update.
* win32-low.c (win32_target_ops): Update.
Nowadays, we set proc->priv->new_inferior to 1 inside linux_add_process,
and new_inferior is used as a flag to initialise target description later.
linux_add_process is used for the three cases, fork/vfork event
(handle_extended_wait), run the program (linux_create_inferior), and
attach to the process (linux_attach). In the first case, the child's
target description is copied from parent's, so we don't need to initialise
target description again later, which means we don't need to set
proc->priv->new_inferior to 1 in this case. For the rest of two cases,
we need this flag.
This patch move the code setting proc->priv->new_inferior to 1 inside
linux_add_process to linux_create_inferior and linux_attach. No
functionality is changed.
gdb/gdbserver:
2015-07-24 Yao Qi <yao.qi@linaro.org>
* linux-low.c (linux_add_process): Don't set
proc->priv->new_inferior.
(linux_create_inferior): Set proc->priv->new_inferior to 1.
(linux_attach): Likewise.
Producer part of the new "build-id" XML attribute.
gdb/ChangeLog
2015-07-15 Aleksandar Ristovski <aristovski@qnx.com
Jan Kratochvil <jan.kratochvil@redhat.com>
gdbserver build-id attribute generator.
* features/library-list-svr4.dtd (library-list-svr4): New
'build-id' attribute.
gdb/doc/ChangeLog
2015-07-15 Aleksandar Ristovski <aristovski@qnx.com
Jan Kratochvil <jan.kratochvil@redhat.com>
gdbserver build-id attribute generator.
* gdb.texinfo (Library List Format for SVR4 Targets): Add
'build-id' in description, example, new attribute in dtd.
gdb/gdbserver/ChangeLog
2015-07-15 Aleksandar Ristovski <aristovski@qnx.com
Jan Kratochvil <jan.kratochvil@redhat.com>
gdbserver build-id attribute generator.
* linux-low.c (nat/linux-maps.h, search.h, rsp-low.h): Include.
(ElfXX_Ehdr, ElfXX_Phdr, ElfXX_Nhdr): New.
(ELFXX_FLD, ELFXX_SIZEOF, ELFXX_ROUNDUP, BUILD_ID_INVALID): New.
(find_phdr): New.
(get_dynamic): Use find_pdhr to traverse program headers.
(struct mapping_entry, mapping_entry_s, free_mapping_entry_vec)
(compare_mapping_entry_range, struct find_memory_region_callback_data)
(read_build_id, find_memory_region_callback, lrfind_mapping_entry)
(get_hex_build_id): New.
(linux_qxfer_libraries_svr4): Add optional build-id attribute
to reply XML document.
If the process disappears (e.g., killed with "kill -9" from the shell)
while it was stopped under GDBserver's control, and the GDBserver
tries to kill it, GDBserver asserts:
(gdb) shell kill -9 23084
(gdb) kill
...
Killing process(es): 23084
/home/pedro/gdb/mygit/src/gdb/gdbserver/linux-low.c:972: A problem internal to GDBserver has been detected.
kill_wait_lwp: Assertion `res > 0' failed.
...
gdb/gdbserver/ChangeLog:
2015-07-14 Pedro Alves <palves@redhat.com>
* linux-low.c (kill_wait_lwp): Don't assert if waitpid fails.
Instead, ignore ECHILD, and throw an error for other errnos.
Adds a new command "record btrace pt" to configure the kernel to use
Intel(R) Processor Trace instead of Branch Trace Strore.
The "record btrace" command chooses the tracing format automatically.
Intel(R) Processor Trace support requires Linux 4.1 and libipt.
gdb/
* NEWS: Announce new commands "record btrace pt" and "record pt".
Announce new options "set|show record btrace pt buffer-size".
* btrace.c: Include "rsp-low.h".
Include "inttypes.h".
(btrace_add_pc): Add forward declaration.
(pt_reclassify_insn, ftrace_add_pt, btrace_pt_readmem_callback)
(pt_translate_cpu_vendor, btrace_finalize_ftrace_pt)
(btrace_compute_ftrace_pt): New.
(btrace_compute_ftrace): Support BTRACE_FORMAT_PT.
(check_xml_btrace_version): Update version check.
(parse_xml_raw, parse_xml_btrace_pt_config_cpu)
(parse_xml_btrace_pt_raw, parse_xml_btrace_pt)
(btrace_pt_config_cpu_attributes, btrace_pt_config_children)
(btrace_pt_children): New.
(btrace_children): Add support for "pt".
(parse_xml_btrace_conf_pt, btrace_conf_pt_attributes): New.
(btrace_conf_children): Add support for "pt".
* btrace.h: Include "intel-pt.h".
(btrace_pt_error): New.
* common/btrace-common.c (btrace_format_string, btrace_data_fini)
(btrace_data_empty): Support BTRACE_FORMAT_PT.
* common/btrace-common.h (btrace_format): Add BTRACE_FORMAT_PT.
(struct btrace_config_pt): New.
(struct btrace_config)<pt>: New.
(struct btrace_data_pt_config, struct btrace_data_pt): New.
(struct btrace_data)<pt>: New.
* features/btrace-conf.dtd (btrace-conf)<pt>: New.
(pt): New.
* features/btrace.dtd (btrace)<pt>: New.
(pt, pt-config, cpu): New.
* nat/linux-btrace.c (perf_event_read, perf_event_read_all)
(perf_event_pt_event_type, kernel_supports_pt)
(linux_supports_pt): New.
(linux_supports_btrace): Support BTRACE_FORMAT_PT.
(linux_enable_bts): Free tinfo on error.
(linux_enable_pt): New.
(linux_enable_btrace): Support BTRACE_FORMAT_PT.
(linux_disable_pt): New.
(linux_disable_btrace): Support BTRACE_FORMAT_PT.
(linux_fill_btrace_pt_config, linux_read_pt): New.
(linux_read_btrace): Support BTRACE_FORMAT_PT.
* nat/linux-btrace.h (struct btrace_tinfo_pt): New.
(struct btrace_target_info)<pt>: New.
* record-btrace.c (set_record_btrace_pt_cmdlist)
(show_record_btrace_pt_cmdlist): New.
(record_btrace_print_pt_conf): New.
(record_btrace_print_conf): Support BTRACE_FORMAT_PT.
(btrace_ui_out_decode_error): Support BTRACE_FORMAT_PT.
(cmd_record_btrace_pt_start): New.
(cmd_record_btrace_start): Support BTRACE_FORMAT_PT.
(cmd_set_record_btrace_pt, cmd_show_record_btrace_pt): New.
(_initialize_record_btrace): Add new commands.
* remote.c (PACKET_Qbtrace_pt, PACKET_Qbtrace_conf_pt_size): New.
(remote_protocol_features): Add "Qbtrace:pt".
Add "Qbtrace-conf:pt:size".
(remote_supports_btrace): Support BTRACE_FORMAT_PT.
(btrace_sync_conf): Support PACKET_Qbtrace_conf_pt_size.
(remote_enable_btrace): Support BTRACE_FORMAT_PT.
(_initialize_remote): Add new commands.
gdbserver/
* linux-low.c: Include "rsp-low.h"
(linux_low_encode_pt_config, linux_low_encode_raw): New.
(linux_low_read_btrace): Support BTRACE_FORMAT_PT.
(linux_low_btrace_conf): Support BTRACE_FORMAT_PT.
(handle_btrace_enable_pt): New.
(handle_btrace_general_set): Support "pt".
(handle_btrace_conf_general_set): Support "pt:size".
doc/
* gdb.texinfo (Process Record and Replay): Spell out that variables
and registers are not available during btrace replay.
Describe the new "record btrace pt" command.
Describe the new "set|show record btrace pt buffer-size" options.
(General Query Packets): Describe the new Qbtrace:pt and
Qbtrace-conf:pt:size packets.
Expand "bts" to "Branch Trace Store".
Update the branch trace DTD.
This commit implements the "vFile:setfs" packet in gdbserver.
gdb/gdbserver/ChangeLog:
* target.h (struct target_ops) <multifs_open>: New field.
<multifs_unlink>: Likewise.
<multifs_readlink>: Likewise.
* linux-low.c (nat/linux-namespaces.h): New include.
(linux_target_ops): Initialize the_target->multifs_open,
the_target->multifs_unlink and the_target->multifs_readlink.
* hostio.h (hostio_handle_new_gdb_connection): New declaration.
* hostio.c (hostio_fs_pid): New static variable.
(hostio_handle_new_gdb_connection): New function.
(handle_setfs): Likewise.
(handle_open): Use the_target->multifs_open as appropriate.
(handle_unlink): Use the_target->multifs_unlink as appropriate.
(handle_readlink): Use the_target->multifs_readlink as
appropriate.
(handle_vFile): Handle vFile:setfs packets.
* server.c (handle_query): Call hostio_handle_new_gdb_connection
after target_handle_new_gdb_connection.
This patch fixes some intermittent test failures in
gdb.base/foll-vfork.exp where a vfork child would be (incorrectly)
resumed when handling the vfork event. In this case the result
was a subsequent event reported to the client side as a SIGTRAP
delivered to the as-yet-unknown child thread.
The new thread was resumed (incorrectly) in linux-low.c when
resume_stopped_resumed_lwps was called from
linux_wait_for_event_filtered after the vfork event had been
handled in handle_extended_wait.
Gdbserver/linux-low.c's add_thread function creates threads with
last_resume_kind == resume_continue by default. This field is
used by resume_stopped_resumed_lwps to decide whether to perform
the resume:
static void
resume_stopped_resumed_lwps (struct inferior_list_entry *entry) {
struct thread_info *thread = (struct thread_info *) entry;
struct lwp_info *lp = get_thread_lwp (thread);
if (lp->stopped
&& !lp->status_pending_p
&& thread->last_resume_kind != resume_stop
&& thread->last_status.kind == TARGET_WAITKIND_IGNORE)
{
So the fix is to make sure to set thread->last_resume_kind to
resume_stop. Here we do that for new fork children in
gdbserver/linux-low.c:handle_extended_wait.
In addition, it seemed prudent to initialize lwp_info.status_pending_p
for the new fork child. I also rearranged the initialization code
so that all of the lwp_info initialization was together, rather than
intermixed with thread_info and process_info initialization.
Tested native, native-gdbserver, native-extended-gdbserver on
x86_64 GNU/Linux.
gdb/gdbserver/
* linux-low.c (handle_extended_wait): Initialize
thread_info.last_resume_kind for new fork children.
This patch implements follow-fork for vfork on extended-remote Linux targets.
The implementation follows the native implementation as much as possible.
Most of the work is done on the GDB side in the existing code now in
infrun.c. GDBserver just has to report the events and do a little
bookkeeping.
Implementation includes:
* enabling VFORK events by adding ptrace options for VFORK and VFORK_DONE
to linux-low.c:linux_low_ptrace_options.
* handling VFORK and VFORK_DONE events in linux-low.c:handle_extended_wait
and reporting them to GDB.
* including VFORK and VFORK_DONE events in the predicate
linux-low.c:extended_event_reported.
* adding support for VFORK and VFORK_DONE events in RSP by adding stop
reasons "vfork" and "vforkdone" to the 'T' Stop Reply Packet in both
gdbserver/remote-utils.c and gdb/remote.c.
Tested on x64 Ubuntu Lucid, native, remote, extended-remote.
gdb/gdbserver/ChangeLog:
* linux-low.c (handle_extended_wait): Handle PTRACE_EVENT_FORK and
PTRACE_EVENT_VFORK_DONE.
(linux_low_ptrace_options, extended_event_reported): Add vfork
events.
* remote-utils.c (prepare_resume_reply): New stop reasons "vfork"
and "vforkdone" for RSP 'T' Stop Reply Packet.
* server.h (report_vfork_events): Declare
global variable.
gdb/ChangeLog:
* remote.c (remove_vfork_event_p): New function.
(remote_follow_fork): Add vfork event type to event checking.
(remote_parse_stop_reply): New stop reasons "vfork" and
"vforkdone" for RSP 'T' Stop Reply Packet.
This patch implements the architecture-specific pieces of follow-fork
for remote and extended-remote Linux targets, which in the current
implementation copyies the parent's debug register state into the new
child's data structures. This is required for x86, arm, aarch64, and
mips.
This follows the native implementation as closely as possible by
implementing a new linux_target_ops function 'new_fork', which is
analogous to 'linux_nat_new_fork' in linux-nat.c. In gdbserver, the debug
registers are stored in the process list, instead of an
architecture-specific list, so the function arguments are process_info
pointers instead of an lwp_info and a pid as in the native implementation.
In the MIPS implementation the debug register mirror is stored differently
from x86, ARM, and aarch64, so instead of doing a simple structure assignment
I had to clone the list of watchpoint structures.
Tested using gdb.threads/watchpoint-fork.exp on x86, and ran manual tests
on a MIPS board and an ARM board. Aarch64 hasn't been tested.
gdb/gdbserver/ChangeLog:
* linux-aarch64-low.c (aarch64_linux_new_fork): New function.
(the_low_target) <new_fork>: Initialize new member.
* linux-arm-low.c (arm_new_fork): New function.
(the_low_target) <new_fork>: Initialize new member.
* linux-low.c (handle_extended_wait): Call new target function
new_fork.
* linux-low.h (struct linux_target_ops) <new_fork>: New member.
* linux-mips-low.c (mips_add_watchpoint): New function
extracted from mips_insert_point.
(the_low_target) <new_fork>: Initialize new member.
(mips_linux_new_fork): New function.
(mips_insert_point): Call mips_add_watchpoint.
* linux-x86-low.c (x86_linux_new_fork): New function.
(the_low_target) <new_fork>: Initialize new member.
This patch implements basic support for follow-fork and detach-on-fork on
extended-remote Linux targets. Only 'fork' is supported in this patch;
'vfork' support is added n a subsequent patch. This patch depends on
the previous patches in the patch series.
Sufficient extended-remote functionality has been implemented here to pass
gdb.base/multi-forks.exp, as well as gdb.base/foll-fork.exp with the
catchpoint tests commented out. Some other fork tests fail with this
patch because it doesn't provide the architecture support needed for
watchpoint inheritance or fork catchpoints.
The implementation follows the same general structure as for the native
implementation as much as possible.
This implementation includes:
* enabling fork events in linux-low.c in initialize_low and
linux_enable_extended_features
* handling fork events in gdbserver/linux-low.c:handle_extended_wait
- when a fork event occurs in gdbserver, we must do the full creation
of the new process, thread, lwp, and breakpoint lists. This is
required whether or not the new child is destined to be
detached-on-fork, because GDB will make target calls that require all
the structures. In particular we need the breakpoint lists in order
to remove the breakpoints from a detaching child. If we are not
detaching the child we will need all these structures anyway.
- as part of this event handling we store the target_waitstatus in a new
member of the parent lwp_info structure, 'waitstatus'. This
is used to store extended event information for reporting to GDB.
- handle_extended_wait is given a return value, denoting whether the
handled event should be reported to GDB. Previously it had only
handled clone events, which were never reported.
* using a new predicate in gdbserver to control handling of the fork event
(and eventually all extended events) in linux_wait_1. The predicate,
extended_event_reported, checks a target_waitstatus.kind for an
extended ptrace event.
* implementing a new RSP 'T' Stop Reply Packet stop reason: "fork", in
gdbserver/remote-utils.c and remote.c.
* implementing new target and RSP support for target_follow_fork with
target extended-remote. (The RSP components were actually defined in
patch 1, but they see their first use here).
- remote target routine remote_follow_fork, which just sends the 'D;pid'
detach packet to detach the new fork child cleanly. We can't just
call target_detach because the data structures for the forked child
have not been allocated on the host side.
Tested on x64 Ubuntu Lucid, native, remote, extended-remote.
gdb/gdbserver/ChangeLog:
* linux-low.c (handle_extended_wait): Implement return value,
rename argument 'event_child' to 'event_lwp', handle
PTRACE_EVENT_FORK, call internal_error for unrecognized event.
(linux_low_ptrace_options): New function.
(linux_low_filter_event): Call linux_low_ptrace_options,
use different argument fo linux_enable_event_reporting,
use return value from handle_extended_wait.
(extended_event_reported): New function.
(linux_wait_1): Call extended_event_reported and set
status to report fork events.
(linux_write_memory): Add pid to debug message.
(reset_lwp_ptrace_options_callback): New function.
(linux_handle_new_gdb_connection): New function.
(linux_target_ops): Initialize new structure member.
* linux-low.h (struct lwp_info) <waitstatus>: New member.
* lynx-low.c: Initialize new structure member.
* remote-utils.c (prepare_resume_reply): Implement stop reason
"fork" for "T" stop message.
* server.c (handle_query): Call handle_new_gdb_connection.
* server.h (report_fork_events): Declare global flag.
* target.h (struct target_ops) <handle_new_gdb_connection>:
New member.
(target_handle_new_gdb_connection): New macro.
* win32-low.c: Initialize new structure member.
gdb/ChangeLog:
* linux-nat.c (linux_nat_ptrace_options): New function.
(linux_init_ptrace, wait_lwp, linux_nat_filter_event):
Call linux_nat_ptrace_options and use different argument to
linux_enable_event_reporting.
(_initialize_linux_nat): Delete call to
linux_ptrace_set_additional_flags.
* nat/linux-ptrace.c (current_ptrace_options): Rename to
supported_ptrace_options.
(additional_flags): Delete variable.
(linux_check_ptrace_features): Use supported_ptrace_options.
(linux_test_for_tracesysgood, linux_test_for_tracefork):
Likewise, and remove additional_flags check.
(linux_enable_event_reporting): Change 'attached' argument to
'options'. Use supported_ptrace_options.
(ptrace_supports_feature): Change comment. Use
supported_ptrace_options.
(linux_ptrace_set_additional_flags): Delete function.
* nat/linux-ptrace.h (linux_ptrace_set_additional_flags):
Delete function prototype.
* remote.c (remote_fork_event_p): New function.
(remote_detach_pid): New function.
(remote_detach_1): Call remote_detach_pid, don't mourn inferior
if doing detach-on-fork.
(remote_follow_fork): New function.
(remote_parse_stop_reply): Handle new "T" stop reason "fork".
(remote_pid_to_str): Print "process" strings for pid/0/0 ptids.
(init_extended_remote_ops): Initialize to_follow_fork.
This patch implements a mechanism for GDB to determine whether fork
events are supported in gdbserver. This is a preparatory patch for
remote fork and exec event support.
Two new RSP packets are defined to represent fork and vfork event
support. These packets are used just like PACKET_multiprocess_feature
to denote whether the corresponding event is supported. GDB sends
fork-events+ and vfork-events+ to gdbserver to inquire about fork
event support. If the response enables these packets, then GDB
knows that gdbserver supports the corresponding events and will
enable them.
Target functions used to query for support are included along with
each new packet.
In order for gdbserver to know whether the events are supported at the
point where the qSupported packet arrives, the code in nat/linux-ptrace.c
had to be reorganized. Previously it would test for fork/exec event
support, then enable the events using the pid of the inferior. When the
qSupported packet arrives there may not be an inferior. So the mechanism
was split into two parts: a function that checks whether the events are
supported, called when gdbserver starts up, and another that enables the
events when the inferior stops for the first time.
Another gdbserver change was to add some global variables similar to
multi_process, one per new packet. These are used to control whether
the corresponding fork events are enabled. If GDB does not inquire
about the event support in the qSupported packet, then gdbserver will
not set these "report the event" flags. If the flags are not set, the
events are ignored like they were in the past. Thus, gdbserver will
never send fork event notification to an older GDB that doesn't
recognize fork events.
Tested on Ubuntu x64, native/remote/extended-remote, and as part of
subsequent patches in the series.
gdb/gdbserver/ChangeLog:
* linux-low.c (linux_supports_fork_events): New function.
(linux_supports_vfork_events): New function.
(linux_target_ops): Initialize new structure members.
(initialize_low): Call linux_check_ptrace_features.
* lynx-low.c (lynx_target_ops): Initialize new structure
members.
* server.c (report_fork_events, report_vfork_events):
New global flags.
(handle_query): Add new features to qSupported packet and
response.
(captured_main): Initialize new global variables.
* target.h (struct target_ops) <supports_fork_events>:
New member.
<supports_vfork_events>: New member.
(target_supports_fork_events): New macro.
(target_supports_vfork_events): New macro.
* win32-low.c (win32_target_ops): Initialize new structure
members.
gdb/ChangeLog:
* nat/linux-ptrace.c (linux_check_ptrace_features): Change
from static to extern.
* nat/linux-ptrace.h (linux_check_ptrace_features): Declare.
* remote.c (anonymous enum): <PACKET_fork_event_feature,
* PACKET_vfork_event_feature>: New enumeration constants.
(remote_protocol_features): Add table entries for new packets.
(remote_query_supported): Add new feature queries to qSupported
packet.
(_initialize_remote): Exempt new packets from the requirement
to have 'set remote' commands.
GDBserver steps over breakpoint if the condition is false, but if target
doesn't support hardware single step, the step over is very simple, if
not incorrect, in linux-arm-low.c:
/* We only place breakpoints in empty marker functions, and thread locking
is outside of the function. So rather than importing software single-step,
we can just run until exit. */
static CORE_ADDR
arm_reinsert_addr (void)
{
struct regcache *regcache = get_thread_regcache (current_thread, 1);
unsigned long pc;
collect_register_by_name (regcache, "lr", &pc);
return pc;
}
and linux-mips-low.c does the same. GDBserver sets a breakpoint at the
return address of the current function, resume and wait the program hits
the breakpoint in order to achieve "breakpoint step over". What if
program hits other user breakponits during this "step over"?
It is worse if the arm/thumb interworking is considered. Nowadays,
GDBserver arm backend unconditionally inserts arm breakpoint,
/* Define an ARM-mode breakpoint; we only set breakpoints in the C
library, which is most likely to be ARM. If the kernel supports
clone events, we will never insert a breakpoint, so even a Thumb
C library will work; so will mixing EABI/non-EABI gdbserver and
application. */
(const unsigned char *) &arm_breakpoint,
(const unsigned char *) &arm_eabi_breakpoint,
note that the comments are no longer valid as C library can be compiled
in thumb mode.
When GDBserver steps over a breakpoint in arm mode function, which
returns to thumb mode, GDBserver will insert arm mode breakpoint by
mistake and the program will crash. GDBserver alone is unable to
determine the arm/thumb mode given a PC address. See how GDB does
it in arm-tdep.c:arm_pc_is_thumb.
After thinking about how to teach GDBserver inserting right breakpoint
(arm or thumb) for a while, I reconsider it from a different direction
that it may be unreasonable to run target-side conditional breakpoint for
targets without hardware single step. Pedro also pointed this out here
https://sourceware.org/ml/gdb-patches/2015-04/msg00337.html
This patch is to add a new target_ops hook
supports_conditional_breakpoints, and only reply
";ConditionalBreakpoints+" if it is true. On linux targets,
supports_conditional_breakpoints returns true if target has hardware
single step, on other targets, (win32, lynx, nto, spu), set it to NULL,
because conditional breakpoint is a linux-specific feature.
gdb/gdbserver:
2015-05-08 Yao Qi <yao.qi@linaro.org>
* linux-low.c (linux_supports_conditional_breakpoints): New
function.
(linux_target_ops): Install new target method.
* lynx-low.c (lynx_target_ops): Install NULL hook for
supports_conditional_breakpoints.
* nto-low.c (nto_target_ops): Likewise.
* spu-low.c (spu_target_ops): Likewise.
* win32-low.c (win32_target_ops): Likewise.
* server.c (handle_query): Check
target_supports_conditional_breakpoints.
* target.h (struct target_ops) <supports_conditional_breakpoints>:
New field.
(target_supports_conditional_breakpoints): New macro.
Hi,
I see the following error on arm linux gdbserver,
continue^M
Continuing.^M
../../../binutils-gdb/gdb/gdbserver/linux-arm-low.c:458: A problem internal to GDBserver has been detected.^M
raw_bkpt_type_to_arm_hwbp_type: unhandled raw type^M
Remote connection closed^M
(gdb) FAIL: gdb.base/cond-eval-mode.exp: hbreak: continue
After we make GDBserver handling Zx/zx packet idempotent,
[PATCH 3/3] [GDBserver] Make Zx/zx packet handling idempotent.
https://sourceware.org/ml/gdb-patches/2014-04/msg00480.html
> Now removal/insertion of all kinds of breakpoints/watchpoints, either
> internal, or from GDB, always go through the target methods.
GDBserver handles all kinds of breakpoints/watchpoints through target
methods. However, some target backends, such as arm, don't support Z0
packet but need software breakpoint to do breakpoint stepping over in
linux-low.c:start_step_over,
if (can_hardware_single_step ())
{
step = 1;
}
else
{
CORE_ADDR raddr = (*the_low_target.breakpoint_reinsert_addr) ();
set_reinsert_breakpoint (raddr);
step = 0;
}
a software breakpoint is requested to the backend, and the error is
triggered. This problem should affect targets having
breakpoint_reinsert_addr hooked.
Instead of handling memory breakpoint in these affected linux backend,
this patch handles memory breakpoint in linux_{insert,remove}_point,
that, if memory breakpoint is requested, call
{insert,remove}_memory_breakpoint respectively. Then, it becomes
unnecessary to handle memory breakpoint for linux x86 backend, so
this patch removes the code there.
This patch is tested with GDBserver on x86_64-linux and arm-linux
(-marm, -mthumb). Note that there are still some fails in
gdb.base/cond-eval-mode.exp with -mthumb, because GDBserver doesn't
know how to select the correct breakpoint instruction according to
the arm-or-thumb-mode of requested address. This is a separate
issue, anyway.
gdb/gdbserver:
2015-04-09 Yao Qi <yao.qi@linaro.org>
* linux-low.c (linux_insert_point): Call
insert_memory_breakpoint if TYPE is raw_bkpt_type_sw.
(linux_remove_point): Call remove_memory_breakpoint if type is
raw_bkpt_type_sw.
* linux-x86-low.c (x86_insert_point): Don't call
insert_memory_breakpoint.
(x86_remove_point): Don't call remove_memory_breakpoint.
This adds/tweaks a few debug logs I found useful recently.
gdb/gdbserver/ChangeLog:
2015-03-24 Pedro Alves <palves@redhat.com>
* linux-low.c (check_stopped_by_breakpoint): Tweak debug log
output. Also dump TRAP_TRACE.
(linux_low_filter_event): In debug output, distinguish a
resume_stop SIGSTOP from a delayed SIGSTOP.
gdb/ChangeLog:
2015-03-24 Pedro Alves <palves@redhat.com>
* linux-nat.c (linux_nat_resume): Output debug logs before trying
to resume the event lwp. Use the lwp's ptid instead of the passed
in (maybe wildcard) ptid.
(stop_wait_callback): Tweak debug log output.
(check_stopped_by_breakpoint): Tweak debug log output. Also dump
TRAP_TRACE.
(linux_nat_filter_event): In debug output, distinguish a
resume_stop SIGSTOP from a delayed SIGSTOP. Output debug logs
before trying to resume the lwp.
This commit moves the code to handle lwp_info.arch_private for
Linux x86 into a new shared file, nat/x86-linux.c.
gdb/ChangeLog:
* nat/x86-linux.h: New file.
* nat/x86-linux.c: Likewise.
* Makefile.in (HFILES_NO_SRCDIR): Add nat/x86-linux.h.
(x86-linux.o): New rule.
* config/i386/linux.mh (NATDEPFILES): Add x86-linux.o.
* config/i386/linux64.mh (NATDEPFILES): Likewise.
* nat/linux-nat.h (struct arch_lwp_info): New forward declaration.
(lwp_set_arch_private_info): New declaration.
(lwp_arch_private_info): Likewise.
* linux-nat.c (lwp_set_arch_private_info): New function.
(lwp_arch_private_info): Likewise.
* x86-linux-nat.c: Include nat/x86-linux.h.
(arch_lwp_info): Removed structure.
(update_debug_registers_callback):
Use lwp_set_debug_registers_changed.
(x86_linux_prepare_to_resume): Use lwp_debug_registers_changed
and lwp_set_debug_registers_changed.
(x86_linux_new_thread): Use lwp_set_debug_registers_changed.
gdb/gdbserver/ChangeLog:
* Makefile.in (x86-linux.o): New rule.
* configure.srv: Add x86-linux.o to relevant targets.
* linux-low.c (lwp_set_arch_private_info): New function.
(lwp_arch_private_info): Likewise.
* linux-x86-low.c: Include nat/x86-linux.h.
(arch_lwp_info): Removed structure.
(update_debug_registers_callback):
Use lwp_set_debug_registers_changed.
(x86_linux_prepare_to_resume): Use lwp_debug_registers_changed
and lwp_set_debug_registers_changed.
(x86_linux_new_thread): Use lwp_set_debug_registers_changed.
This commit changes the signature of linux_target_ops.new_thread in
gdbserver to match that used in GDB's equivalent.
gdb/gdbserver/ChangeLog:
* linux-low.h (linux_target_ops) <new_thread>: Changed signature.
* linux-arm-low.c (arm_new_thread): Likewise.
* linux-aarch64-low.c (aarch64_linux_new_thread): Likewise.
* linux-mips-low.c (mips_linux_new_thread): Likewise.
* linux-x86-low.c (x86_linux_new_thread): Likewise.
* linux-low.c (add_lwp): Update the_low_target.new_thread call.
This commit introduces three accessors that shared Linux code can
use to access fields of struct lwp_info. The GDB and gdbserver
Linux x86 code is modified to use them.
gdb/ChangeLog:
* nat/linux-nat.h (ptid_of_lwp): New declaration.
(lwp_is_stopped): Likewise.
(lwp_stop_reason): Likewise.
* linux-nat.c (ptid_of_lwp): New function.
(lwp_is_stopped): Likewise.
(lwp_is_stopped_by_watchpoint): Likewise.
* x86-linux-nat.c (update_debug_registers_callback):
Use lwp_is_stopped.
(x86_linux_prepare_to_resume): Use ptid_of_lwp and
lwp_stop_reason.
gdb/gdbserver/ChangeLog:
* linux-low.c (ptid_of_lwp): New function.
(lwp_is_stopped): Likewise.
(lwp_stop_reason): Likewise.
* linux-x86-low.c (update_debug_registers_callback):
Use lwp_is_stopped.
(x86_linux_prepare_to_resume): Use ptid_of_lwp and
lwp_stop_reason.
This commit introduces a new function, iterate_over_lwps, that
shared Linux code can use to call a function for each LWP that
matches certain criteria. This function already existed in GDB
and was in use by GDB's various low-level Linux x86 debug register
setters. An equivalent was written for gdbserver and gdbserver's
low-level Linux x86 debug register setters were modified to use
it.
gdb/ChangeLog:
* linux-nat.h: Include nat/linux-nat.h.
(iterate_over_lwps): Move declaration to nat/linux-nat.h.
* nat/linux-nat.h (struct lwp_info): New forward declaration.
(iterate_over_lwps_ftype): New typedef.
(iterate_over_lwps): New declaration.
* linux-nat.h (iterate_over_lwps): Update comment. Use
iterate_over_lwps_ftype. Update callback return value check.
gdb/gdbserver/ChangeLog:
* linux-low.h: Include nat/linux-nat.h.
* linux-low.c (iterate_over_lwps_args): New structure.
(iterate_over_lwps_filter): New function.
(iterate_over_lwps): Likewise.
* linux-x86-low.c (update_debug_registers_callback):
Update signature to what iterate_over_lwps expects.
Remove PID check that iterate_over_lwps now performs.
(x86_dr_low_set_addr): Use iterate_over_lwps.
(x86_dr_low_set_control): Likewise.
This commit introduces a new function, current_lwp_ptid, that
shared Linux code can use to obtain the ptid of the current
lightweight process.
gdb/ChangeLog:
* nat/linux-nat.h (current_lwp_ptid): New declaration.
* linux-nat.c (current_lwp_ptid): New function.
* x86-linux-nat.c: Include nat/linux-nat.h.
(x86_linux_dr_get_addr): Use current_lwp_ptid.
(x86_linux_dr_get_control): Likewise.
(x86_linux_dr_get_status): Likewise.
(x86_linux_dr_set_control): Likewise.
(x86_linux_dr_set_addr): Likewise.
gdb/gdbserver/ChangeLog:
* linux-low.c (current_lwp_ptid): New function.
* linux-x86-low.c: Include nat/linux-nat.h.
(x86_dr_low_get_addr): Use current_lwp_ptid.
(x86_dr_low_get_control): Likewise.
(x86_dr_low_get_status): Likewise.
On GNU/Linux, this test sometimes FAILs like this:
(gdb) run
Starting program: /home/pedro/gdb/mygit/build/gdb/testsuite/gdb.threads/killed
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
ptrace: No such process.
(gdb)
Program terminated with signal SIGKILL, Killed.
The program no longer exists.
FAIL: gdb.threads/killed.exp: run program to completion (timeout)
Note the suspicious "No such process" line (that's errno==ESRCH).
Adding debug output we see:
linux_nat_wait: [process -1], [TARGET_WNOHANG]
LLW: enter
LNW: waitpid(-1, ...) returned 18465, ERRNO-OK
LLW: waitpid 18465 received Stopped (signal) (stopped)
LNW: waitpid(-1, ...) returned 18461, ERRNO-OK
LLW: waitpid 18461 received Trace/breakpoint trap (stopped)
LLW: Handling extended status 0x03057f
LHEW: Got clone event from LWP 18461, new child is LWP 18465
LNW: waitpid(-1, ...) returned 0, ERRNO-OK
RSRL: resuming stopped-resumed LWP LWP 18465 at 0x3b36af4b51: step=0
RSRL: resuming stopped-resumed LWP LWP 18461 at 0x3b36af4b51: step=0
sigchld
ptrace: No such process.
(gdb) linux_nat_wait: [process -1], [TARGET_WNOHANG]
LLW: enter
LNW: waitpid(-1, ...) returned 18465, ERRNO-OK
LLW: waitpid 18465 received Killed (terminated)
LLW: LWP 18465 exited.
LNW: waitpid(-1, ...) returned 18461, No child processes
LLW: waitpid 18461 received Killed (terminated)
Process 18461 exited
LNW: waitpid(-1, ...) returned -1, No child processes
LLW: exit
sigchld
infrun: target_wait (-1, status) =
infrun: 18461 [process 18461],
infrun: status->kind = signalled, signal = GDB_SIGNAL_KILL
infrun: TARGET_WAITKIND_SIGNALLED
Program terminated with signal SIGKILL, Killed.
The program no longer exists.
infrun: stop_waiting
FAIL: gdb.threads/killed.exp: run program to completion (timeout)
The issue is that here:
RSRL: resuming stopped-resumed LWP LWP 18465 at 0x3b36af4b51: step=0
RSRL: resuming stopped-resumed LWP LWP 18461 at 0x3b36af4b51: step=0
The first line shows we had just resumed LWP 18465, which does:
void *
child_func (void *dummy)
{
kill (pid, SIGKILL);
exit (1);
}
So if the kernel manages to schedule that thread fast enough, the
process may be killed before GDB has a chance to resume LWP 18461.
GDBserver has code at the tail end of linux_resume_one_lwp to cope
with this:
~~~
ptrace (step ? PTRACE_SINGLESTEP : PTRACE_CONT, lwpid_of (thread),
(PTRACE_TYPE_ARG3) 0,
/* Coerce to a uintptr_t first to avoid potential gcc warning
of coercing an 8 byte integer to a 4 byte pointer. */
(PTRACE_TYPE_ARG4) (uintptr_t) signal);
current_thread = saved_thread;
if (errno)
{
/* ESRCH from ptrace either means that the thread was already
running (an error) or that it is gone (a race condition). If
it's gone, we will get a notification the next time we wait,
so we can ignore the error. We could differentiate these
two, but it's tricky without waiting; the thread still exists
as a zombie, so sending it signal 0 would succeed. So just
ignore ESRCH. */
if (errno == ESRCH)
return;
perror_with_name ("ptrace");
}
~~~
However, that's not a complete fix, because between starting to handle
the resume request and getting that PTRACE_CONTINUE, we run other
ptrace calls that can also fail with ESRCH, and that end up throwing
an error (with perror_with_name).
In the case above, I indeed sometimes see resume_stopped_resumed_lwps
fail in the registers read:
resume_stopped_resumed_lwps (struct lwp_info *lp, void *data)
{
...
CORE_ADDR pc = regcache_read_pc (regcache);
Or e.g., in 32-bit mode, i386_linux_resume has several calls that can
throw too.
Whether to ignore ptrace errors or not depends on context that is only
available somewhere up the call chain. So the fix is to let ptrace
errors throw as they do today, and wrap the resume request in a
TRY/CATCH that swallows it iff the lwp that we were trying to resume
is no longer ptrace-stopped.
gdb/gdbserver/ChangeLog:
2015-03-19 Pedro Alves <palves@redhat.com>
* linux-low.c (linux_resume_one_lwp): Rename to ...
(linux_resume_one_lwp_throw): ... this. Don't handle ESRCH here,
instead call perror_with_name.
(check_ptrace_stopped_lwp_gone): New function.
(linux_resume_one_lwp): Reimplement as wrapper around
linux_resume_one_lwp_throw that swallows errors if the LWP is
gone.
gdb/ChangeLog:
2015-03-19 Pedro Alves <palves@redhat.com>
* linux-nat.c (linux_resume_one_lwp): Rename to ...
(linux_resume_one_lwp_throw): ... this. Don't handle ESRCH here,
instead call perror_with_name.
(check_ptrace_stopped_lwp_gone): New function.
(linux_resume_one_lwp): Reimplement as wrapper around
linux_resume_one_lwp_throw that swallows errors if the LWP is
gone.
(resume_stopped_resumed_lwps): Try register reads in TRY/CATCH and
swallows errors if the LWP is gone. Use
linux_resume_one_lwp_throw instead of linux_resume_one_lwp.
The previous change added an assertion that is catching yet another
bug in count_events_callback/select_event_lwp_callback:
(gdb)
PASS: gdb.mi/mi-nonstop.exp: interrupted
mi_expect_interrupt: expecting: \*stopped,(reason="signal-received",signal-name="0",signal-meaning="Signal 0"|reason="signal-received",signal-name="SIGINT",signal-meaning="Interrupt")[^
]*
/home/pedro/gdb/mygit/src/gdb/gdbserver/linux-low.c:2329: A problem internal to GDBserver has been detected.
select_event_lwp: Assertion `num_events > 0' failed.
=thread-group-exited,id="i1"
Certainly select_event_lwp_callback should always at least find one
event, as it's only called because an event triggered (though we may
have more than one: the point of the function is randomly picking
one).
An LWP that GDB previously asked to continue/step (thus is resumed)
and gets a vCont;t request ends up with last_resume_kind ==
resume_stop. These functions in gdbserver used to filter out events
that weren't going to be reported to GDB; I think the last_resume_kind
kind check used to make sense at that point, but it no longer does.
gdb/gdbserver/ChangeLog:
2015-03-19 Pedro Alves <palves@redhat.com>
* linux-low.c (count_events_callback, select_event_lwp_callback):
No longer check whether the thread has resume_stop as last resume
kind.
Wanting to make sure the new continue-pending-status.exp test tests
both cases of threads 2 and 3 reporting an event, I added counters to
the test, to make it FAIL if events for both threads aren't seen.
Assuming a well behaved backend, and given a reasonable number of
iterations, it should PASS.
However, running that against GNU/Linux gdbserver, I found that
surprisingly, that FAILed. GDBserver always reported the breakpoint
hit for the same thread.
Turns out that I broke gdbserver's thread event randomization
recently, with git commit 582511be ([gdbserver] linux-low.c: better
starvation avoidance, handle non-stop mode too). In that commit I
missed that the thread structure also has a status_pending_p field...
The end result was that count_events_callback always returns 0, and
then if no thread is stepping, select_event_lwp always returns the
event thread. IOW, no randomization is happening at all. Quite
curious how all the other changes in that patch were sufficient to fix
non-stop-fair-events.exp anyway even with that broken.
Tested on x86_64 Fedora 20, native and gdbserver.
gdb/gdbserver/ChangeLog:
2015-03-19 Pedro Alves <palves@redhat.com>
* linux-low.c (count_events_callback, select_event_lwp_callback):
Use the lwp's status_pending_p field, not the thread's.
gdb/testsuite/ChangeLog:
2015-03-19 Pedro Alves <palves@redhat.com>
* gdb.threads/continue-pending-status.exp (saw_thread_2)
(saw_thread_3): New globals.
(top level): Increment them when an event for the corresponding
thread is seen.
(no thread starvation): New test.
This function (in both GDB and GDBserver) used to consider only
SIGTRAP/breakpoint events, but that's no longer the case nowadays.
gdb/gdbserver/ChangeLog:
2015-03-19 Pedro Alves <palves@redhat.com>
* linux-low.c (select_event_lwp_callback): Update comments to
no longer mention SIGTRAP.
gdb/ChangeLog:
2015-03-19 Pedro Alves <palves@redhat.com>
* linux-nat.c (select_event_lwp_callback): Update comment to no
longer mention SIGTRAP.
This commit introduces a new inline common function "startswith"
which takes two string arguments and returns nonzero if the first
string starts with the second. It also updates the 295 places
where this logic was written out longhand to use the new function.
gdb/ChangeLog:
* common/common-utils.h (startswith): New inline function.
All places where this logic was used updated to use the above.
This patch adjusts gdbserver's Linux backend to tell gdbserver core
(and ultimately GDB) whether a trap was caused by a breakpoint.
It teaches the backend to get that information out of the si_code of
the SIGTRAP siginfo.
gdb/gdbserver/ChangeLog:
2015-03-04 Pedro Alves <palves@redhat.com>
* linux-low.c (check_stopped_by_breakpoint) [USE_SIGTRAP_SIGINFO]:
Decide whether a breakpoint triggered based on the SIGTRAP's
siginfo.si_code.
(thread_still_has_status_pending_p) [USE_SIGTRAP_SIGINFO]: Don't check whether a
breakpoint is inserted if relying on SIGTRAP's siginfo.si_code.
(linux_low_filter_event): Check for breakpoints before checking
watchpoints.
(linux_wait_1): Don't re-increment the PC if relying on SIGTRAP's
siginfo.si_code.
(linux_stopped_by_sw_breakpoint)
(linux_supports_stopped_by_sw_breakpoint)
(linux_stopped_by_hw_breakpoint)
(linux_supports_stopped_by_hw_breakpoint): New functions.
(linux_target_ops): Install new target methods.
The heuristic for filtering out kernel addressess in BTS trace checks the
most significant bit in each address. This works fine for 32-bit and 64-bit
mode.
For 32-bit compatibility mode, i.e. a 32-bit inferior running on 64-bit
host, we need to check bit 63 (or any bit bigger than 31), not bit 31.
Use the machine field in struct utsname provided by a uname call to
determine whether we are running on a 64-bit host.
Thanks to Jan Kratochvil for reporting the issue.
gdb/
* nat/linux-btrace.c: Include sys/utsname.h.
(linux_determine_kernel_ptr_bits): New.
(linux_enable_bts): Call linux_determine_kernel_ptr_bits.
* x86-linux-nat.c (x86_linux_enable_btrace): Do not overwrite non-zero
ptr_bits.
gdbserver/
* linux-low.c (linux_low_enable_btrace): Do not overwrite non-zero
ptr_bits.
This patch renames symbols that happen to have names which are
reserved keywords in C++.
Most of this was generated with Tromey's cxx-conversion.el script.
Some places where later hand massaged a bit, to fix formatting, etc.
And this was rebased several times meanwhile, along with re-running
the script, so re-running the script from scratch probably does not
result in the exact same output. I don't think that matters anyway.
gdb/
2015-02-27 Tom Tromey <tromey@redhat.com>
Pedro Alves <palves@redhat.com>
Rename symbols whose names are reserved C++ keywords throughout.
gdb/gdbserver/
2015-02-27 Tom Tromey <tromey@redhat.com>
Pedro Alves <palves@redhat.com>
Rename symbols whose names are reserved C++ keywords throughout.
.decr_pc_after_break is never higher than .breakpoint_len, so use
.breakpoint_len directly. Based on idea from Yao here:
https://sourceware.org/ml/gdb-patches/2015-02/msg00689.html
gdb/gdbserver/ChangeLog:
2015-02-26 Pedro Alves <palves@redhat.com>
* linux-low.c (linux_wait_1): When incrementing the PC past a
program breakpoint always use the_low_target.breakpoint_len as
increment, rather than the maximum between that and
the_low_target.decr_pc_after_break.
I'm going to add an alternate mechanism of breakpoint trap
identification to 'check_stopped_by_breakpoint' that does not rely on
checking the instruction at PC. The mechanism currently used to tell
whether we're stepping over a permanent breakpoint doesn't fit in that
new method. This patch redoes the whole logic in a different way that
works with both old and new methods, in essence moving the "stepped
permanent breakpoint" detection "one level up". It makes lower level
check_stopped_by_breakpoint always the adjust the PC, and then has
linux_wait_1 advance the PC past the breakpoint if necessary. This
ends up being better also because this now handles
non-decr_pc_after_break targets too. Before, such targets would get
stuck forever reexecuting the breakpoint instruction.
Tested on x86_64 Fedora 20.
gdb/gdbserver/ChangeLog:
2015-02-23 Pedro Alves <palves@redhat.com>
* linux-low.c (check_stopped_by_breakpoint): Don't check if the
thread was doing a step-over; always adjust the PC if
we stepped over a permanent breakpoint.
(linux_wait_1): If we stepped over breakpoint that was on top of a
permanent breakpoint, manually advance the PC past it.
Another fix I'm working made schedlock.exp fail with gdbserver
frequently. Looking deeper, it turns out to be a pre-existing bug.
status_pending_p_callback is filtering out LWPs incorrectly. The
result is that that sometimes status_pending_p_callback returns a
pending event for an LWP that isn't expected, and then GDBserver gets
very confused.
E.g,. when doing a step-over, linux_wait_for_event is called with a
particular LWP's ptid, meaning events for all other LWPs should be
left pending, but here we see it retuning an event for some other LWP:
linux_wait_1: [<all threads>]
step_over_bkpt set [LWP 29577.29577], doing a blocking wait <--------
my_waitpid (-1, 0x40000001)
my_waitpid (-1, 0x80000001): status(57f), 0
LWFE: waitpid(-1, ...) returned 0, ERRNO-OK
pc is 0x4007a0
src/gdb/gdbserver/linux-low.c:2587: A problem internal to GDBserver has been detected.
linux_wait_1: got event for 29581 <--------
Remote connection closed
(gdb) FAIL: gdb.threads/schedlock.exp: continue to breakpoint: return to loop (initial)
delete breakpoints
Tested on x86_64 Fedora 20.
gdb/gdbserver/ChangeLog:
2015-02-20 Pedro Alves <palves@redhat.com>
* linux-low.c (status_pending_p_callback): Use ptid_match.
When gdb creates a dummy frame to execute a function in the inferior,
the process may generate a SIGSEGV, SIGTRAP or SIGILL because the stack
is non executable. If the signal handler set in gdb has option print
or stop enabled for these signals gdb handles this correctly.
However, in the case of noprint and nostop the signal is short-circuited
and the inferior process is sent the signal directly. This causes the
inferior to crash because of gdb.
This patch adds a check for SIGSEGV, SIGTRAP or SIGILL so that these
signals are sent to gdb rather than short-circuited in the inferior.
gdb then handles them properly and the inferior process does not
crash.
This patch also fixes the same behavior in gdbserver.
Also added a small testcase to test the issue called catch-gdb-caused-signals.
This applies to Linux only, tested on Linux.
gdb/ChangeLog:
PR breakpoints/16812
* linux-nat.c (linux_nat_filter_event): Report SIGTRAP,SIGILL,SIGSEGV.
* nat/linux-ptrace.c (linux_wstatus_maybe_breakpoint): Add.
* nat/linux-ptrace.h: Add linux_wstatus_maybe_breakpoint.
gdb/gdbserver/ChangeLog:
PR breakpoints/16812
* linux-low.c (wstatus_maybe_breakpoint): Remove.
(linux_low_filter_event): Update wstatus_maybe_breakpoint name.
(linux_wait_1): Report SIGTRAP,SIGILL,SIGSEGV.
gdb/testsuite/ChangeLog:
PR breakpoints/16812
* gdb.base/catch-gdb-caused-signals.c: New file.
* gdb.base/catch-gdb-caused-signals.exp: New file.
Allow the size of the branch trace ring buffer to be defined by the
user. The specified buffer size will be used when BTS tracing is
enabled for new threads.
The obtained buffer size may differ from the requested size. The
actual buffer size for the current thread is shown in the "info record"
command.
Bigger buffers mean longer traces, but also longer processing time.
2015-02-09 Markus Metzger <markus.t.metzger@intel.com>
* btrace.c (parse_xml_btrace_conf_bts): Add size.
(btrace_conf_bts_attributes): New.
(btrace_conf_children): Add attributes.
* common/btrace-common.h (btrace_config_bts): New.
(btrace_config)<bts>: New.
(btrace_config): Update comment.
* nat/linux-btrace.c (linux_enable_btrace, linux_enable_bts):
Use config.
* features/btrace-conf.dtd: Increment version. Add size
attribute to bts element.
* record-btrace.c (set_record_btrace_bts_cmdlist,
show_record_btrace_bts_cmdlist): New.
(record_btrace_adjust_size, record_btrace_print_bts_conf,
record_btrace_print_conf, cmd_set_record_btrace_bts,
cmd_show_record_btrace_bts): New.
(record_btrace_info): Call record_btrace_print_conf.
(_initialize_record_btrace): Add commands.
* remote.c: Add PACKET_Qbtrace_conf_bts_size enum.
(remote_protocol_features): Add Qbtrace-conf:bts:size packet.
(btrace_sync_conf): Synchronize bts size.
(_initialize_remote): Add Qbtrace-conf:bts:size packet.
* NEWS: Announce new commands and new packets.
doc/
* gdb.texinfo (Branch Trace Configuration Format): Add size.
(Process Record and Replay): Describe new set|show commands.
(General Query Packets): Describe Qbtrace-conf:bts:size packet.
testsuite/
* gdb.btrace/buffer-size: New.
gdbserver/
* linux-low.c (linux_low_btrace_conf): Print size.
* server.c (handle_btrace_conf_general_set): New.
(hanle_general_set): Call handle_btrace_conf_general_set.
(handle_query): Report Qbtrace-conf:bts:size as supported.
