Commit graph

16 commits

Author SHA1 Message Date
Pedro Alves
e7ad2f145c Handle MIPS Linux SIGTRAP siginfo.si_code values
This unbreaks pending/delayed breakpoints handling, as well as
hardware watchpoints, on MIPS.

Ref: https://sourceware.org/ml/gdb-patches/2016-02/msg00681.html

The MIPS kernel reports SI_KERNEL for all kernel generated traps,
instead of TRAP_BRKPT / TRAP_HWBKPT, but GDB isn't aware of this.

Basically, this commit:

- Folds watchpoints logic into check_stopped_by_breakpoint, and
  renames it to save_stop_reason.

- Adds GDB_ARCH_IS_TRAP_HWBKPT.

- Makes MIPS set both GDB_ARCH_IS_TRAP_BRPT and
  GDB_ARCH_IS_TRAP_HWBKPT to SI_KERNEL.  In save_stop_reason, we
  handle the case of the same si_code returning true for both
  TRAP_BRPT and TRAP_HWBKPT by looking at what the debug registers
  say.

Tested on x86-64 Fedora 20, native and gdbserver.

gdb/ChangeLog:
2016-02-24  Pedro Alves  <palves@redhat.com>

	* linux-nat.c (save_sigtrap) Delete.
	(stop_wait_callback): Call save_stop_reason instead of
	save_sigtrap.
	(check_stopped_by_breakpoint): Rename to ...
	(save_stop_reason): ... this.  Bits of save_sigtrap folded here.
	Use GDB_ARCH_IS_TRAP_HWBKPT and handle ambiguous
	GDB_ARCH_IS_TRAP_BRKPT / GDB_ARCH_IS_TRAP_HWBKPT.  Factor out
	common code between the USE_SIGTRAP_SIGINFO and
	!USE_SIGTRAP_SIGINFO blocks.
	(linux_nat_filter_event): Call save_stop_reason instead of
	save_sigtrap.
	* nat/linux-ptrace.h: Check for both SI_KERNEL and TRAP_BRKPT
	si_code for MIPS.
	* nat/linux-ptrace.h: Fix "TRAP_HWBPT" typo in x86 table.  Add
	comments on MIPS behavior.
	(GDB_ARCH_IS_TRAP_HWBKPT): Define for all archs.

gdb/gdbserver/ChangeLog:
2016-02-24  Pedro Alves  <palves@redhat.com>

	* linux-low.c (check_stopped_by_breakpoint): Rename to ...
	(save_stop_reason): ... this.  Use GDB_ARCH_IS_TRAP_HWBKPT and
	handle ambiguous GDB_ARCH_IS_TRAP_BRKPT / GDB_ARCH_IS_TRAP_HWBKPT.
	Factor out common code between the USE_SIGTRAP_SIGINFO and
	!USE_SIGTRAP_SIGINFO blocks.
	(linux_low_filter_event): Call save_stop_reason instead of
	check_stopped_by_breakpoint and check_stopped_by_watchpoint.
	Update comments.
	(linux_wait_1): Update comments.
2016-02-24 22:52:06 +00:00
Joel Brobecker
618f726fcb GDB copyright headers update after running GDB's copyright.py script.
gdb/ChangeLog:

        Update year range in copyright notice of all files.
2016-01-01 08:43:22 +04:00
Don Breazeal
94585166df Extended-remote follow-exec
This patch implements support for exec events on extended-remote Linux
targets.  Follow-exec-mode and rerun behave as expected.  Catchpoints and
test updates are implemented in subsequent patches.

This patch was derived from a patch posted last October:
https://sourceware.org/ml/gdb-patches/2014-10/msg00877.html.
It was originally based on some work done by Luis Machado in 2013.

IMPLEMENTATION
----------------
Exec events are enabled via ptrace options.

When an exec event is detected by gdbserver, the existing process
data, along with all its associated lwp and thread data, is deleted
and replaced by data for a new single-threaded process.  The new
process data is initialized with the appropriate parts of the state
of the execing process.  This approach takes care of several potential
pitfalls, including:

 * deleting the data for an execing non-leader thread before any
   wait/sigsuspend occurs
 * correctly initializing the architecture of the execed process

We then report the exec event using a new RSP stop reason, "exec".

When GDB receives an "exec" event, it saves the status in the event
structure's target_waitstatus field, like what is done for remote fork
events.  Because the original and execed programs may have different
architectures, we skip parsing the section of the stop reply packet
that contains register data.  The register data will be retrieved
later after the inferior's architecture has been set up by
infrun.c:follow_exec.

At that point the exec event is handled by the existing event handling
in GDB.  However, a few changes were necessary so that
infrun.c:follow_exec could accommodate the remote target.

 * Where follow-exec-mode "new" is handled, we now call
   add_inferior_with_spaces instead of add_inferior with separate calls
   to set up the program and address spaces.  The motivation for this
   is that add_inferior_with_spaces also sets up the initial architecture
   for the inferior, which is needed later by target_find_description
   when it calls target_gdbarch.

 * We call a new target function, target_follow_exec.  This function
   allows us to store the execd_pathname in the inferior, instead of
   using the static string remote_exec_file from remote.c.  The static
   string didn't work for follow-exec-mode "new", since once you switched
   to the execed program, the original remote exec-file was lost.  The
   execd_pathname is now stored in the inferior's program space as a
   REGISTRY field.  All of the requisite mechanisms for this are
   defined in remote.c.

gdb/gdbserver/ChangeLog:

	* linux-low.c (linux_mourn): Static declaration.
	(linux_arch_setup): Move in front of
	handle_extended_wait.
	(linux_arch_setup_thread): New function.
	(handle_extended_wait): Handle exec events.  Call
	linux_arch_setup_thread.  Make event_lwp argument a
	pointer-to-a-pointer.
	(check_zombie_leaders): Do not check stopped threads.
	(linux_low_ptrace_options): Add PTRACE_O_TRACEEXEC.
	(linux_low_filter_event): Add lwp and thread for exec'ing
	non-leader thread if leader thread has been deleted.
	Refactor code into linux_arch_setup_thread and call it.
	Pass child lwp pointer by reference to handle_extended_wait.
	(linux_wait_for_event_filtered): Update comment.
	(linux_wait_1): Prevent clobbering exec event status.
	(linux_supports_exec_events): New function.
	(linux_target_ops) <supports_exec_events>: Initialize new member.
	* lynx-low.c (lynx_target_ops) <supports_exec_events>: Initialize
	new member.
	* remote-utils.c (prepare_resume_reply): New stop reason 'exec'.
	* server.c (report_exec_events): New global variable.
	(handle_query): Handle qSupported query for exec-events feature.
	(captured_main): Initialize report_exec_events.
	* server.h (report_exec_events): Declare new global variable.
	* target.h (struct target_ops) <supports_exec_events>: New
	member.
	(target_supports_exec_events): New macro.
	* win32-low.c (win32_target_ops) <supports_exec_events>:
	Initialize new member.

gdb/ChangeLog:

	* infrun.c (follow_exec): Use process-style ptid for
	exec message.  Call add_inferior_with_spaces and
	target_follow_exec.
	* nat/linux-ptrace.c (linux_supports_traceexec): New function.
	* nat/linux-ptrace.h (linux_supports_traceexec): Declare.
	* remote.c (remote_pspace_data): New static variable.
	(remote_pspace_data_cleanup): New function.
	(get_remote_exec_file): New function.
	(set_remote_exec_file_1): New function.
	(set_remote_exec_file): New function.
	(show_remote_exec_file): New function.
	(remote_exec_file): Delete static variable.
	(anonymous enum) <PACKET_exec_event_feature> New
	enumeration constant.
	(remote_protocol_features): Add entry for exec-events feature.
	(remote_query_supported): Add client side of qSupported query
	for exec-events feature.
	(remote_follow_exec): New function.
	(remote_parse_stop_reply): Handle 'exec' stop reason.
	(extended_remote_run, extended_remote_create_inferior): Call
	get_remote_exec_file and set_remote_exec_file_1.
	(init_extended_remote_ops) <to_follow_exec>: Initialize new
	member.
	(_initialize_remote): Call
	register_program_space_data_with_cleanup.  Call
	add_packet_config_cmd for remote exec-events feature.
	Modify call to add_setshow_string_noescape_cmd for exec-file
	to use new functions set_remote_exec_file and
	show_remote_exec_file.
	* target-debug.h, target-delegates.c: Regenerated.
	* target.c (target_follow_exec): New function.
	* target.h (struct target_ops) <to_follow_exec>: New member.
	(target_follow_exec): Declare new function.
2015-09-11 11:12:46 -07:00
Ulrich Weigand
1db33b5a02 Detect SW breakpoints in Cell/B.E. combined debugging
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.
2015-08-27 19:26:31 +02:00
Pedro Alves
5826e15986 Linux: sys/ptrace.h -> nat/gdb_ptrace.h everywhere
So that we pick the enum __ptrace_request fix everywhere.

gdb/ChangeLog:
2015-07-24  Pedro Alves  <palves@redhat.com>

	* aarch64-linux-nat.c: Include nat/gdb_ptrace.h instead of
	sys/ptrace.h.
	* alpha-linux-nat.c: Likewise.
	* amd64-linux-nat.c: Likewise.
	* arm-linux-nat.c: Likewise.
	* hppa-linux-nat.c: Likewise.
	* i386-linux-nat.c: Likewise.
	* ia64-linux-nat.c: Likewise.
	* linux-fork.c: Likewise.
	* linux-nat.c: Likewise.
	* m32r-linux-nat.c: Likewise.
	* m68klinux-nat.c: Likewise.
	* mips-linux-nat.c: Likewise.
	* nat/linux-btrace.c: Likewise.
	* nat/linux-ptrace.c: Likewise.
	* nat/linux-ptrace.h
	* nat/mips-linux-watch.c: Likewise.
	* nat/x86-linux-dregs.c: Likewise.
	* ppc-linux-nat.c: Likewise.
	* s390-linux-nat.c: Likewise.
	* spu-linux-nat.c: Likewise.
	* tilegx-linux-nat.c: Likewise.
	* x86-linux-nat.c: Likewise.
	* xtensa-linux-nat.c: Likewise.

gdb/gdbserver/ChangeLog:
2015-07-24  Pedro Alves  <palves@redhat.c: Likewise.om>

	* linux-aarch64-low.c: Include nat/gdb_ptrace.h instead of
	sys/ptrace.h.
	* linux-arm-low.c: Likewise.
	* linux-cris-low.c: Likewise.
	* linux-crisv32-low.c: Likewise.
	* linux-low.c: Likewise.
	* linux-m68k-low.c: Likewise.
	* linux-mips-low.c: Likewise.
	* linux-nios2-low.c: Likewise.
	* linux-s390-low.c: Likewise.
	* linux-sparc-low.c: Likewise.
	* linux-tic6x-low.c: Likewise.
	* linux-tile-low.c: Likewise.
	* linux-x86-low.c: Likewise.
2015-07-24 15:14:47 +01:00
Yao Qi
ca9b78ce90 Move PTRACE_GETREGSET and PTRACE_SETREGSET to nat/linux-ptrace.h
Macros PTRACE_GETREGSET and PTRACE_SETREGSET are defined locally in
some places in GDB and GDBserver.  This patch is to move them to
nat/linux-ptrace.h to avoid duplication.

gdb:

2015-06-01  Yao Qi  <yao.qi@linaro.org>

	* amd64-linux-nat.c: Include "nat/linux-ptrace.h".
	* i386-linux-nat.c: Likewise.
	* nat/linux-ptrace.h (PTRACE_GETREGSET, PTRACE_SETREGSET): Define.
	* s390-linux-nat.c: Include "nat/linux-ptrace.h".
	(PTRACE_GETREGSET, PTRACE_SETREGSET): Remove.
	* x86-linux-nat.c: Include "nat/linux-ptrace.h".
	* x86-linux-nat.h (PTRACE_GETREGSET, PTRACE_SETREGSET): Remove.

gdb/gdbserver:

2015-06-01  Yao Qi  <yao.qi@linaro.org>

	* linux-s390-low.c (PTRACE_GETREGSET, PTRACE_SETREGSET): Remove.
	* linux-x86-low.c: Likewise.
2015-06-01 12:13:02 +01:00
Don Breazeal
de0d863ec3 Extended-remote Linux follow fork
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.
2015-05-12 09:52:43 -07:00
Don Breazeal
89245bc056 Identify remote fork event support
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.
2015-05-12 09:52:41 -07:00
Pedro Alves
faf09f0119 Linux native: Use TRAP_BRKPT/TRAP_HWBPT
This patch adjusts the native Linux target backend to tell the core
whether a trap was caused by a breakpoint.

It teaches the target to get that information out of the si_code of
the SIGTRAP siginfo.

Tested on x86-64 Fedora 20, s390 RHEL 7, and PPC64 Fedora 18.  An
earlier version was tested on ARM Fedora 21.

gdb/ChangeLog:
2015-03-04  Pedro Alves  <palves@redhat.com>

	* linux-nat.c (save_sigtrap): Check for breakpoints before
	checking watchpoints.
	(status_callback) [USE_SIGTRAP_SIGINFO]: Don't check whether a
	breakpoint is inserted if relying on SIGTRAP's siginfo.si_code.
	(check_stopped_by_breakpoint) [USE_SIGTRAP_SIGINFO]: Decide whether
	a breakpoint triggered based on the SIGTRAP's siginfo.si_code.
	(linux_nat_stopped_by_sw_breakpoint)
	(linux_nat_supports_stopped_by_sw_breakpoint)
	(linux_nat_stopped_by_hw_breakpoint)
	(linux_nat_supports_stopped_by_hw_breakpoint): New functions.
	(linux_nat_wait_1): Don't re-increment the PC if relying on
	SIGTRAP's siginfo->si_code.
	(linux_nat_add_target): Install new target methods.
	* linux-thread-db.c (check_event): Don't account for breakpoint PC
	offset if the target already adjusted the PC.
	* nat/linux-ptrace.h (USE_SIGTRAP_SIGINFO): New.
	(GDB_ARCH_TRAP_BRKPT): New.
	(TRAP_HWBKPT): Define if not already defined.
2015-03-04 20:41:16 +00:00
Antoine Tremblay
c9587f8823 Fix non executable stack handling when calling functions in the inferior.
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.
2015-02-19 11:04:21 -05:00
Pedro Alves
8784d56326 Linux: on attach, attach to lwps listed under /proc/$pid/task/
... instead of relying on libthread_db.

I wrote a test that attaches to a program that constantly spawns
short-lived threads, which exposed several issues.  This is one of
them.

On Linux, we need to attach to all threads of a process (thread group)
individually.  We currently rely on libthread_db to list the threads,
but that is problematic, because libthread_db relies on reading data
structures out of the inferior (which may well be corrupted).  If
threads are being created or exiting just while we try to attach, we
may trip on inconsistencies in the inferior's thread list.  To work
around that, when we see a seemingly corrupt list, we currently retry
a few times:

 static void
 thread_db_find_new_threads_2 (ptid_t ptid, int until_no_new)
 {
 ...
   if (until_no_new)
     {
       /* Require 4 successive iterations which do not find any new threads.
	  The 4 is a heuristic: there is an inherent race here, and I have
	  seen that 2 iterations in a row are not always sufficient to
	  "capture" all threads.  */
 ...

That heuristic may well fail, and when it does, we end up with threads
in the program that aren't under GDB's control.  That's obviously bad
and results in quite mistifying failures, like e.g., the process dying
for seeminly no reason when a thread that wasn't attached trips on a
breakpoint.

There's really no reason to rely on libthread_db for this nowadays
when we have /proc mounted.  In that case, which is the usual case, we
can list the LWPs from /proc/PID/task/.  In fact, GDBserver is already
doing this.  The patch factors out that code that knows to walk the
task/ directory out of GDBserver, and makes GDB use it too.

Like GDBserver, the patch makes GDB attach to LWPs and _not_ wait for
them to stop immediately.  Instead, we just tag the LWP as having an
expected stop.  Because we can only set the ptrace options when the
thread stops, we need a new flag in the lwp structure to keep track of
whether we've already set the ptrace options, just like in GDBserver.
Note that nothing issues any ptrace command to the threads between the
PTRACE_ATTACH and the stop, so this is safe (unlike one scenario
described in gdbserver's linux-low.c).

When we attach to a program that has threads exiting while we attach,
it's easy to race with a thread just exiting as we try to attach to
it, like:

  #1 - get current list of threads
  #2 - attach to each listed thread
  #3 - ooops, attach failed, thread is already gone

As this is pretty normal, we shouldn't be issuing a scary warning in
step #3.

When #3 happens, PTRACE_ATTACH usually fails with ESRCH, but sometimes
we'll see EPERM as well.  That happens when the kernel still has the
thread in its task list, but the thread is marked as dead.
Unfortunately, EPERM is ambiguous and we'll get it also on other
scenarios where the thread isn't dead, and in those cases, it's useful
to get a warning.  To distiguish the cases, when we get an EPERM
failure, we open /proc/PID/status, and check the thread's state -- if
the /proc file no longer exists, or the state is "Z (Zombie)" or "X
(Dead)", we ignore the EPERM error silently; otherwise, we'll warn.
Unfortunately, there seems to be a kernel race here.  Sometimes I get
EPERM, and then the /proc state still indicates "R (Running)"...  If
we wait a bit and retry, we do end up seeing X or Z state, or get an
ESRCH.  I thought of making GDB retry the attach a few times, but even
with a 500ms wait and 4 retries, I still see the warning sometimes.  I
haven't been able to identify the kernel path that causes this yet,
but in any case, it looks like a kernel bug to me.  As this just
results failure to suppress a warning that we've been printing since
about forever anyway, I'm just making the test cope with it, and issue
an XFAIL.

gdb/gdbserver/
2015-01-09  Pedro Alves  <palves@redhat.com>

	* linux-low.c (linux_attach_fail_reason_string): Move to
	nat/linux-ptrace.c, and rename.
	(linux_attach_lwp): Update comment.
	(attach_proc_task_lwp_callback): New function.
	(linux_attach): Adjust to rename and use
	linux_proc_attach_tgid_threads.
	(linux_attach_fail_reason_string): Delete declaration.

gdb/
2015-01-09  Pedro Alves  <palves@redhat.com>

	* linux-nat.c (attach_proc_task_lwp_callback): New function.
	(linux_nat_attach): Use linux_proc_attach_tgid_threads.
	(wait_lwp, linux_nat_filter_event): If not set yet, set the lwp's
	ptrace option flags.
	* linux-nat.h (struct lwp_info) <must_set_ptrace_flags>: New
	field.
	* nat/linux-procfs.c: Include <dirent.h>.
	(linux_proc_get_int): New parameter "warn".  Handle it.
	(linux_proc_get_tgid): Adjust.
	(linux_proc_get_tracerpid): Rename to ...
	(linux_proc_get_tracerpid_nowarn): ... this.
	(linux_proc_pid_get_state): New function, factored out from
	(linux_proc_pid_has_state): ... this.  Add new parameter "warn"
	and handle it.
	(linux_proc_pid_is_gone): New function.
	(linux_proc_pid_is_stopped): Adjust.
	(linux_proc_pid_is_zombie_maybe_warn)
	(linux_proc_pid_is_zombie_nowarn): New functions.
	(linux_proc_pid_is_zombie): Use
	linux_proc_pid_is_zombie_maybe_warn.
	(linux_proc_attach_tgid_threads): New function.
	* nat/linux-procfs.h (linux_proc_get_tgid): Update comment.
	(linux_proc_get_tracerpid): Rename to ...
	(linux_proc_get_tracerpid_nowarn): ... this, and update comment.
	(linux_proc_pid_is_gone): New declaration.
	(linux_proc_pid_is_zombie): Update comment.
	(linux_proc_pid_is_zombie_nowarn): New declaration.
	(linux_proc_attach_lwp_func): New typedef.
	(linux_proc_attach_tgid_threads): New declaration.
	* nat/linux-ptrace.c (linux_ptrace_attach_fail_reason): Adjust to
	use nowarn functions.
	(linux_ptrace_attach_fail_reason_string): Move here from
	gdbserver/linux-low.c and rename.
	(ptrace_supports_feature): If the current ptrace options are not
	known yet, check them now, instead of asserting.
	* nat/linux-ptrace.h (linux_ptrace_attach_fail_reason_string):
	Declare.
2015-01-09 11:39:49 +00:00
Joel Brobecker
32d0add0a6 Update year range in copyright notice of all files owned by the GDB project.
gdb/ChangeLog:

        Update year range in copyright notice of all files.
2015-01-01 13:32:14 +04:00
Joel Brobecker
beed38b827 [Linux] Ask kernel to kill inferior when GDB terminates
This patch enhances GDB on GNU/Linux systems in the situation where
we are debugging an inferior that was created from GDB (as opposed
to attached to), by asking the kernel to kill the inferior if GDB
terminates without doing it itself.

This would typically happen when GDB encounters a problem and
crashes, or when it gets killed by an external process. This can
be observed by starting a program under GDB, and then killing
GDB with signal 9. After GDB is killed, the inferior still remains.

This patch also fixes GDBserver similarly.

This fix is conditional on the kernel supporting the PTRACE_O_EXITKILL
feature.  On older kernels, the behavior remains unchanged.

gdb/ChangeLog:

        * nat/linux-ptrace.h (PTRACE_O_EXITKILL): Define if not
        already defined.
        (linux_enable_event_reporting): Add parameter "attached".
        * nat/linux-ptrace.c (linux_test_for_exitkill): New forward
        declaration.  New function.
        (linux_check_ptrace_features): Add linux_test_for_exitkill call.
        (linux_enable_event_reporting): Add new parameter "attached".
        Do not call ptrace with the PTRACE_O_EXITKILL if ATTACHED is
        nonzero.
        * linux-nat.c (linux_init_ptrace): Add parameter "attached".
        Use it.  Update function description.
        (linux_child_post_attach, linux_child_post_startup_inferior):
        Update call to linux_enable_event_reporting.

gdb/gdbserver/ChangeLog:

        * linux-low.c (linux_low_filter_event): Update call to
        linux_enable_event_reporting following the addition of
        a new parameter to that function.

Tested on x86_64-linux, native and native-gdbserver.

I also verified by hand that the inferior gets killed when killing
GDB in the "run" case, while the inferior remains in the "attach"
case. Same for GDBserver.
2014-12-16 07:56:46 -05:00
Don Breazeal
89a5711c56 Refactor ptrace extended event status.
This commit implements functions for identifying and extracting extended
ptrace event information from a Linux wait status.  These are just
convenience functions intended to hide the ">> 16" used to extract the
event from the wait status word, replacing the hard-coded shift with a more
descriptive function call.  This is preparatory work for implementation of
follow-fork and detach-on-fork for extended-remote linux targets.

gdb/ChangeLog:

	* linux-nat.c (linux_handle_extended_wait): Call
	linux_ptrace_get_extended_event.
	(wait_lwp): Call linux_is_extended_waitstatus.
	(linux_nat_filter_event): Call linux_ptrace_get_extended_event
	and linux_is_extended_waitstatus.
	* nat/linux-ptrace.c (linux_test_for_tracefork): Call
	linux_ptrace_get_extended_event.
	(linux_ptrace_get_extended_event): New function.
	(linux_is_extended_waitstatus): New function.
	* nat/linux-ptrace.h (linux_ptrace_get_extended_event)
	(linux_is_extended_waitstatus): New declarations.

gdb/gdbserver/ChangeLog:

	* linux-low.c (handle_extended_wait): Call
	linux_ptrace_get_extended_event.
	(get_stop_pc, get_detach_signal, linux_low_filter_event): Call
	linux_is_extended_waitstatus.

---
2014-09-19 10:54:34 -07:00
Tom Tromey
8009206ae2 Remove some GDBSERVER checks from linux-ptrace
This patch removes some GDBSERVER checks from nat/linux-ptrace.c.
Currently the code uses a compile-time check to decide whether some
flags should be used.  This changes the code to instead let users of
the module specify an additional set of flags; and then changes gdb's
linux-nat.c to call this function.  At some later date, when the back
ends are fully merged, we will be able to remove this function again.

gdb/
2014-07-24  Tom Tromey  <tromey@redhat.com>
	    Gary Benson  <gbenson@redhat.com>

	* nat/linux-ptrace.c (additional_flags): New global.
	(linux_test_for_tracesysgood, linux_test_for_tracefork): Use
	additional_flags; don't check GDBSERVER.
	(linux_ptrace_set_additional_flags): New function.
	* nat/linux-ptrace.h (linux_ptrace_set_additional_flags):
	Declare.
	* linux-nat.c (_initialize_linux_nat): Call
	linux_ptrace_set_additional_flags.
2014-07-24 15:06:39 +01:00
Gary Benson
125f8a3dde Move shared native target specific code to gdb/nat
https://sourceware.org/gdb/wiki/Common describes the following
directory structure:

 gdb/nat/
   Native target backend files. Code that interfaces with the
   host debug API. E.g., ptrace code, Windows debug API code,
   procfs code should go here.

 gdb/target/
   Host-independent, target vector specific code (target_ops).

 gdb/common/
   All other shared code.

This commit moves all native target backend files currently in
gdb/common to gdb/nat.

gdb/
2014-06-20  Gary Benson  <gbenson@redhat.com>

	* common/gdb_thread_db.h: Moved to nat.  All includes updated.
	* common/glibc_thread_db.h: Likewise.
	* common/i386-cpuid.h: Likewise.
	* common/i386-gcc-cpuid.h: Likewise.
	* common/linux-btrace.h: Likewise.
	* common/linux-osdata.h: Likewise.
	* common/linux-procfs.h: Likewise.
	* common/linux-ptrace.h: Likewise.
	* common/mips-linux-watch.h: Likewise.
	* common/linux-btrace.c: Moved to nat.
	* common/linux-osdata.c: Likewise.
	* common/linux-procfs.c: Likewise.
	* common/linux-ptrace.c: Likewise.
	* common/mips-linux-watch.c: Likewise.
	* nat/gdb_thread_db.h: Moved from common.
	* nat/glibc_thread_db.h: Likewise.
	* nat/i386-cpuid.h: Likewise.
	* nat/i386-gcc-cpuid.h: Likewise.
	* nat/linux-btrace.c: Likewise.
	* nat/linux-btrace.h: Likewise.
	* nat/linux-osdata.c: Likewise.
	* nat/linux-osdata.h: Likewise.
	* nat/linux-procfs.c: Likewise.
	* nat/linux-procfs.h: Likewise.
	* nat/linux-ptrace.c: Likewise.
	* nat/linux-ptrace.h: Likewise.
	* nat/mips-linux-watch.c: Likewise.
	* nat/mips-linux-watch.h: Likewise.
	* Makefile.in (HFILES_NO_SRCDIR): Reflect new locations.
	(object file files): Reordered.
	* gdb/copyright.py (EXCLUDE_LIST): Reflect new location
	of glibc_thread_db.h.

gdb/gdbserver/
2014-06-20  Gary Benson  <gbenson@redhat.com>

	* Makefile.in (SFILES): Update locations for files moved
	from common to nat.
	(object file files): Reordered.

gdb/testsuite/
2014-06-20  Gary Benson  <gbenson@redhat.com>

	* gdb.arch/i386-avx.exp: Fix include file location.
	* gdb.arch/i386-sse.exp: Likewise.
2014-06-20 14:06:48 +01:00
Renamed from gdb/common/linux-ptrace.h (Browse further)