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26cb8b7c1a
While reviewing the native AArch64 patch, I noticed a problem:
On 02/06/2013 08:46 PM, Pedro Alves wrote:
>
>> > +static void
>> > +aarch64_linux_prepare_to_resume (struct lwp_info *lwp)
>> > +{
>> > + struct arch_lwp_info *info = lwp->arch_private;
>> > +
>> > + /* NULL means this is the main thread still going through the shell,
>> > + or, no watchpoint has been set yet. In that case, there's
>> > + nothing to do. */
>> > + if (info == NULL)
>> > + return;
>> > +
>> > + if (DR_HAS_CHANGED (info->dr_changed_bp)
>> > + || DR_HAS_CHANGED (info->dr_changed_wp))
>> > + {
>> > + int tid = GET_LWP (lwp->ptid);
>> > + struct aarch64_debug_reg_state *state = aarch64_get_debug_reg_state ();
> Hmm. This is always fetching the debug_reg_state of
> the current inferior, but may not be the inferior of lwp.
> I see the same bug on x86. Sorry about that. I'll fix it.
A natural fix would be to make xxx_get_debug_reg_state take an
inferior argument, but that doesn't work because of the case where we
detach breakpoints/watchpoints from the child fork, at a time there's
no inferior for the child fork at all. We do a nasty hack in
i386_inferior_data_get, but that relies on all callers pointing the
current inferior to the correct inferior, which isn't actually being
done by all callers, and I don't think we want to enforce that -- deep
in the bowls of linux-nat.c, there are many cases we resume lwps
behind the scenes, and it's be better to not have that code rely on
global state (as it doesn't today).
The fix is to decouple the watchpoints code from inferiors, making it
track target processes instead. This way, we can freely keep track of
the watchpoint mirrors for these processes behind the core's back.
Checkpoints also play dirty tricks with swapping the process behind
the inferior, so they get special treatment too in the patch (which
just amounts to calling a new hook). Instead of the old hack in
i386_inferior_data_get, where we returned a copy of the current
inferior's debug registers mirror, as soon as we detect a fork in the
target, we copy the debug register mirror from the parent to the child
process.
I don't have an old kernel handy to test, but I stepped through gdb doing
the watchpoint removal in the fork child in the watchpoint-fork test
seeing that the debug registers end up cleared in the child.
I didn't find the need for linux_nat_iterate_watchpoint_lwps. If
we use plain iterate_over_lwps instead, what happens is that
when removing watchpoints, that iterate_over_lwps doesn't actually
iterate over anything, since the fork child is not added to the
lwp list until later, at detach time, in linux_child_follow_fork.
And if we don't iterate over that lwp, we don't mark its debug
registers as needing update. But linux_child_follow_fork takes
care of doing that explicitly:
child_lp = add_lwp (inferior_ptid);
child_lp->stopped = 1;
child_lp->last_resume_kind = resume_stop;
make_cleanup (delete_lwp_cleanup, child_lp);
/* CHILD_LP has new PID, therefore linux_nat_new_thread is not called for it.
See i386_inferior_data_get for the Linux kernel specifics.
Ensure linux_nat_prepare_to_resume will reset the hardware debug
registers. It is done by the linux_nat_new_thread call, which is
being skipped in add_lwp above for the first lwp of a pid. */
gdb_assert (num_lwps (GET_PID (child_lp->ptid)) == 1);
if (linux_nat_new_thread != NULL)
linux_nat_new_thread (child_lp);
if (linux_nat_prepare_to_resume != NULL)
linux_nat_prepare_to_resume (child_lp);
ptrace (PTRACE_DETACH, child_pid, 0, 0);
so unless I'm missing something (quite possible) it ends up all
the same. But, the !detach-on-fork, and the "follow-fork child" paths
should also call linux_nat_new_thread, and they don't presently. It
seems to me in those cases we're not clearing debug regs correctly
when that's needed. Instead of copying that bit that works around
add_lwp bypassing the linux_nat_new_thread call, I thought it'd
be better to add an add_initial_lwp call to be used in the case we
really need to bypass linux_nat_new_thread, and make
add_lwp always call linux_nat_new_thread.
i386_cleanup_dregs is rewritten to forget about the current process
debug mirrors, which takes cares of other i386 ports. Only a couple
of extra tweaks here and there were needed, as some targets wheren't
actually calling i386_cleanup_dregs.
Tested on Fedora 17 x86_64 -m64/-m32.
GDBserver already fetches the i386_debug_reg_state from the right
process, and, it doesn't handle forks at all, so no fix is needed over
there.
gdb/
2013-02-13 Pedro Alves <palves@redhat.com>
* amd64-linux-nat.c (update_debug_registers_callback):
Update comment.
(amd64_linux_dr_set_control, amd64_linux_dr_set_addr): Use
iterate_over_lwps.
(amd64_linux_prepare_to_resume): Pass the lwp's pid to
i386_debug_reg_state.
(amd64_linux_new_fork): New function.
(_initialize_amd64_linux_nat): Install amd64_linux_new_fork as
linux_nat_new_fork hook, and i386_forget_process as
linux_nat_forget_process hook.
* i386-linux-nat.c (update_debug_registers_callback):
Update comment.
(amd64_linux_dr_set_control, amd64_linux_dr_set_addr): Use
iterate_over_lwps.
(i386_linux_prepare_to_resume): Pass the lwp's pid to
i386_debug_reg_state.
(i386_linux_new_fork): New function.
(_initialize_i386_linux_nat): Install i386_linux_new_fork as
linux_nat_new_fork hook, and i386_forget_process as
linux_nat_forget_process hook.
* i386-nat.c (i386_init_dregs): Delete.
(i386_inferior_data, struct i386_inferior_data):
Delete.
(struct i386_process_info): New.
(i386_process_list): New global.
(i386_find_process_pid, i386_add_process, i386_process_info_get):
New functions.
(i386_inferior_data_get): Delete.
(i386_process_info_get): New function.
(i386_debug_reg_state): New parameter 'pid'. Reimplement.
(i386_forget_process): New function.
(i386_cleanup_dregs): Rewrite.
(i386_update_inferior_debug_regs, i386_insert_watchpoint)
(i386_remove_watchpoint, i386_region_ok_for_watchpoint)
(i386_stopped_data_address, i386_insert_hw_breakpoint)
(i386_remove_hw_breakpoint): Adjust to pass the current process id
to i386_debug_reg_state.
(i386_use_watchpoints): Don't register inferior data.
* i386-nat.h (i386_debug_reg_state): Add new 'pid' parameter, and
adjust comment.
(i386_forget_process): Declare.
* linux-fork.c (delete_fork): Call linux_nat_forget_process.
* linux-nat.c (linux_nat_new_fork, linux_nat_forget_process_hook):
New static globals.
(linux_child_follow_fork): Don't call linux_nat_new_thread here.
(add_initial_lwp): New, factored out from ...
(add_lwp): ... this. Don't check the number of lwps before
calling linux_nat_new_thread.
(linux_nat_iterate_watchpoint_lwps): Delete.
(linux_nat_attach): Use add_initial_lwp instead of add_lwp.
(linux_handle_extended_wait): Call the linux_nat_new_fork hook on
forks and vforks.
(linux_nat_wait_1): Use add_initial_lwp instead of add_lwp for the
initial lwp.
(linux_nat_kill, linux_nat_mourn_inferior): Call
linux_nat_forget_process.
(linux_nat_set_new_fork, linux_nat_set_forget_process)
(linux_nat_forget_process): New functions.
* linux-nat.h (linux_nat_iterate_watchpoint_lwps_ftype): Delete
type.
(linux_nat_iterate_watchpoint_lwps): Delete declaration.
(linux_nat_new_fork_ftype, linux_nat_forget_process_ftype): New
types.
(linux_nat_set_new_fork, linux_nat_set_forget_process)
(linux_nat_forget_process): New declarations.
* amd64fbsd-nat.c (super_mourn_inferior): New global.
(amd64fbsd_mourn_inferior): New function.
(_initialize_amd64fbsd_nat): Override to_mourn_inferior.
* windows-nat.c (windows_detach): Call i386_cleanup_dregs.
215 lines
7.0 KiB
C
215 lines
7.0 KiB
C
/* Native debugging support for GNU/Linux (LWP layer).
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Copyright (C) 2000-2013 Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#include "target.h"
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#include <signal.h>
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struct arch_lwp_info;
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/* Ways to "resume" a thread. */
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enum resume_kind
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{
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/* Thread should continue. */
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resume_continue,
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/* Thread should single-step. */
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resume_step,
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/* Thread should be stopped. */
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resume_stop
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};
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/* Structure describing an LWP. This is public only for the purposes
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of ALL_LWPS; target-specific code should generally not access it
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directly. */
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struct lwp_info
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{
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/* The process id of the LWP. This is a combination of the LWP id
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and overall process id. */
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ptid_t ptid;
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/* Non-zero if this LWP is cloned. In this context "cloned" means
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that the LWP is reporting to its parent using a signal other than
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SIGCHLD. */
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int cloned;
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/* Non-zero if we sent this LWP a SIGSTOP (but the LWP didn't report
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it back yet). */
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int signalled;
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/* Non-zero if this LWP is stopped. */
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int stopped;
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/* Non-zero if this LWP will be/has been resumed. Note that an LWP
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can be marked both as stopped and resumed at the same time. This
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happens if we try to resume an LWP that has a wait status
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pending. We shouldn't let the LWP run until that wait status has
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been processed, but we should not report that wait status if GDB
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didn't try to let the LWP run. */
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int resumed;
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/* The last resume GDB requested on this thread. */
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enum resume_kind last_resume_kind;
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/* If non-zero, a pending wait status. */
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int status;
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/* Non-zero if we were stepping this LWP. */
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int step;
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/* STOPPED_BY_WATCHPOINT is non-zero if this LWP stopped with a data
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watchpoint trap. */
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int stopped_by_watchpoint;
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/* On architectures where it is possible to know the data address of
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a triggered watchpoint, STOPPED_DATA_ADDRESS_P is non-zero, and
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STOPPED_DATA_ADDRESS contains such data address. Otherwise,
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STOPPED_DATA_ADDRESS_P is false, and STOPPED_DATA_ADDRESS is
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undefined. Only valid if STOPPED_BY_WATCHPOINT is true. */
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int stopped_data_address_p;
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CORE_ADDR stopped_data_address;
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/* Non-zero if we expect a duplicated SIGINT. */
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int ignore_sigint;
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/* If WAITSTATUS->KIND != TARGET_WAITKIND_SPURIOUS, the waitstatus
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for this LWP's last event. This may correspond to STATUS above,
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or to a local variable in lin_lwp_wait. */
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struct target_waitstatus waitstatus;
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/* Signal wether we are in a SYSCALL_ENTRY or
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in a SYSCALL_RETURN event.
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Values:
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- TARGET_WAITKIND_SYSCALL_ENTRY
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- TARGET_WAITKIND_SYSCALL_RETURN */
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int syscall_state;
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/* The processor core this LWP was last seen on. */
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int core;
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/* Arch-specific additions. */
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struct arch_lwp_info *arch_private;
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/* Next LWP in list. */
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struct lwp_info *next;
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};
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/* The global list of LWPs, for ALL_LWPS. Unlike the threads list,
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there is always at least one LWP on the list while the GNU/Linux
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native target is active. */
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extern struct lwp_info *lwp_list;
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/* Iterate over each active thread (light-weight process). */
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#define ALL_LWPS(LP) \
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for ((LP) = lwp_list; \
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(LP) != NULL; \
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(LP) = (LP)->next)
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#define GET_LWP(ptid) ptid_get_lwp (ptid)
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#define GET_PID(ptid) ptid_get_pid (ptid)
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#define is_lwp(ptid) (GET_LWP (ptid) != 0)
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#define BUILD_LWP(lwp, pid) ptid_build (pid, lwp, 0)
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/* Attempt to initialize libthread_db. */
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void check_for_thread_db (void);
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int thread_db_attach_lwp (ptid_t ptid);
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/* Return the set of signals used by the threads library. */
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extern void lin_thread_get_thread_signals (sigset_t *mask);
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/* Find process PID's pending signal set from /proc/pid/status. */
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void linux_proc_pending_signals (int pid, sigset_t *pending,
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sigset_t *blocked, sigset_t *ignored);
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/* linux-nat functions for handling fork events. */
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extern void linux_enable_event_reporting (ptid_t ptid);
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extern int lin_lwp_attach_lwp (ptid_t ptid);
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extern void linux_stop_lwp (struct lwp_info *lwp);
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/* Iterator function for lin-lwp's lwp list. */
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struct lwp_info *iterate_over_lwps (ptid_t filter,
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int (*callback) (struct lwp_info *,
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void *),
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void *data);
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/* Create a prototype generic GNU/Linux target. The client can
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override it with local methods. */
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struct target_ops * linux_target (void);
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/* Create a generic GNU/Linux target using traditional
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ptrace register access. */
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struct target_ops *
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linux_trad_target (CORE_ADDR (*register_u_offset)(struct gdbarch *, int, int));
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/* Register the customized GNU/Linux target. This should be used
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instead of calling add_target directly. */
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void linux_nat_add_target (struct target_ops *);
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/* Register a method to call whenever a new thread is attached. */
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void linux_nat_set_new_thread (struct target_ops *, void (*) (struct lwp_info *));
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/* Register a method to call whenever a new fork is attached. */
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typedef void (linux_nat_new_fork_ftype) (struct lwp_info *parent,
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pid_t child_pid);
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void linux_nat_set_new_fork (struct target_ops *ops,
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linux_nat_new_fork_ftype *fn);
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/* Register a method to call whenever a process is killed or
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detached. */
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typedef void (linux_nat_forget_process_ftype) (pid_t pid);
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void linux_nat_set_forget_process (struct target_ops *ops,
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linux_nat_forget_process_ftype *fn);
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/* Call the method registered with the function above. PID is the
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process to forget about. */
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void linux_nat_forget_process (pid_t pid);
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/* Register a method that converts a siginfo object between the layout
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that ptrace returns, and the layout in the architecture of the
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inferior. */
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void linux_nat_set_siginfo_fixup (struct target_ops *,
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int (*) (siginfo_t *,
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gdb_byte *,
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int));
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/* Register a method to call prior to resuming a thread. */
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void linux_nat_set_prepare_to_resume (struct target_ops *,
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void (*) (struct lwp_info *));
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/* Update linux-nat internal state when changing from one fork
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to another. */
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void linux_nat_switch_fork (ptid_t new_ptid);
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/* Store the saved siginfo associated with PTID in *SIGINFO.
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Return 1 if it was retrieved successfully, 0 otherwise (*SIGINFO is
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uninitialized in such case). */
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int linux_nat_get_siginfo (ptid_t ptid, siginfo_t *siginfo);
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/* Set alternative SIGTRAP-like events recognizer. */
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void linux_nat_set_status_is_event (struct target_ops *t,
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int (*status_is_event) (int status));
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