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187b041e25
Today, GDB only allows a single displaced stepping operation to happen per inferior at a time. There is a single displaced stepping buffer per inferior, whose address is fixed (obtained with gdbarch_displaced_step_location), managed by infrun.c. In the case of the AMD ROCm target [1] (in the context of which this work has been done), it is typical to have thousands of threads (or waves, in SMT terminology) executing the same code, hitting the same breakpoint (possibly conditional) and needing to to displaced step it at the same time. The limitation of only one displaced step executing at a any given time becomes a real bottleneck. To fix this bottleneck, we want to make it possible for threads of a same inferior to execute multiple displaced steps in parallel. This patch builds the foundation for that. In essence, this patch moves the task of preparing a displaced step and cleaning up after to gdbarch functions. This allows using different schemes for allocating and managing displaced stepping buffers for different platforms. The gdbarch decides how to assign a buffer to a thread that needs to execute a displaced step. On the ROCm target, we are able to allocate one displaced stepping buffer per thread, so a thread will never have to wait to execute a displaced step. On Linux, the entry point of the executable if used as the displaced stepping buffer, since we assume that this code won't get used after startup. From what I saw (I checked with a binary generated against glibc and musl), on AMD64 we have enough space there to fit two displaced stepping buffers. A subsequent patch makes AMD64/Linux use two buffers. In addition to having multiple displaced stepping buffers, there is also the idea of sharing displaced stepping buffers between threads. Two threads doing displaced steps for the same PC could use the same buffer at the same time. Two threads stepping over the same instruction (same opcode) at two different PCs may also be able to share a displaced stepping buffer. This is an idea for future patches, but the architecture built by this patch is made to allow this. Now, the implementation details. The main part of this patch is moving the responsibility of preparing and finishing a displaced step to the gdbarch. Before this patch, preparing a displaced step is driven by the displaced_step_prepare_throw function. It does some calls to the gdbarch to do some low-level operations, but the high-level logic is there. The steps are roughly: - Ask the gdbarch for the displaced step buffer location - Save the existing bytes in the displaced step buffer - Ask the gdbarch to copy the instruction into the displaced step buffer - Set the pc of the thread to the beginning of the displaced step buffer Similarly, the "fixup" phase, executed after the instruction was successfully single-stepped, is driven by the infrun code (function displaced_step_finish). The steps are roughly: - Restore the original bytes in the displaced stepping buffer - Ask the gdbarch to fixup the instruction result (adjust the target's registers or memory to do as if the instruction had been executed in its original location) The displaced_step_inferior_state::step_thread field indicates which thread (if any) is currently using the displaced stepping buffer, so it is used by displaced_step_prepare_throw to check if the displaced stepping buffer is free to use or not. This patch defers the whole task of preparing and cleaning up after a displaced step to the gdbarch. Two new main gdbarch methods are added, with the following semantics: - gdbarch_displaced_step_prepare: Prepare for the given thread to execute a displaced step of the instruction located at its current PC. Upon return, everything should be ready for GDB to resume the thread (with either a single step or continue, as indicated by gdbarch_displaced_step_hw_singlestep) to make it displaced step the instruction. - gdbarch_displaced_step_finish: Called when the thread stopped after having started a displaced step. Verify if the instruction was executed, if so apply any fixup required to compensate for the fact that the instruction was executed at a different place than its original pc. Release any resources that were allocated for this displaced step. Upon return, everything should be ready for GDB to resume the thread in its "normal" code path. The displaced_step_prepare_throw function now pretty much just offloads to gdbarch_displaced_step_prepare and the displaced_step_finish function offloads to gdbarch_displaced_step_finish. The gdbarch_displaced_step_location method is now unnecessary, so is removed. Indeed, the core of GDB doesn't know how many displaced step buffers there are nor where they are. To keep the existing behavior for existing architectures, the logic that was previously implemented in infrun.c for preparing and finishing a displaced step is moved to displaced-stepping.c, to the displaced_step_buffer class. Architectures are modified to implement the new gdbarch methods using this class. The behavior is not expected to change. The other important change (which arises from the above) is that the core of GDB no longer prevents concurrent displaced steps. Before this patch, start_step_over walks the global step over chain and tries to initiate a step over (whether it is in-line or displaced). It follows these rules: - if an in-line step is in progress (in any inferior), don't start any other step over - if a displaced step is in progress for an inferior, don't start another displaced step for that inferior After starting a displaced step for a given inferior, it won't start another displaced step for that inferior. In the new code, start_step_over simply tries to initiate step overs for all the threads in the list. But because threads may be added back to the global list as it iterates the global list, trying to initiate step overs, start_step_over now starts by stealing the global queue into a local queue and iterates on the local queue. In the typical case, each thread will either: - have initiated a displaced step and be resumed - have been added back by the global step over queue by displaced_step_prepare_throw, because the gdbarch will have returned that there aren't enough resources (i.e. buffers) to initiate a displaced step for that thread Lastly, if start_step_over initiates an in-line step, it stops iterating, and moves back whatever remaining threads it had in its local step over queue to the global step over queue. Two other gdbarch methods are added, to handle some slightly annoying corner cases. They feel awkwardly specific to these cases, but I don't see any way around them: - gdbarch_displaced_step_copy_insn_closure_by_addr: in arm_pc_is_thumb, arm-tdep.c wants to get the closure for a given buffer address. - gdbarch_displaced_step_restore_all_in_ptid: when a process forks (at least on Linux), the address space is copied. If some displaced step buffers were in use at the time of the fork, we need to restore the original bytes in the child's address space. These two adjustments are also made in infrun.c: - prepare_for_detach: there may be multiple threads doing displaced steps when we detach, so wait until all of them are done - handle_inferior_event: when we handle a fork event for a given thread, it's possible that other threads are doing a displaced step at the same time. Make sure to restore the displaced step buffer contents in the child for them. [1] https://github.com/ROCm-Developer-Tools/ROCgdb gdb/ChangeLog: * displaced-stepping.h (struct displaced_step_copy_insn_closure): Adjust comments. (struct displaced_step_inferior_state) <step_thread, step_gdbarch, step_closure, step_original, step_copy, step_saved_copy>: Remove fields. (struct displaced_step_thread_state): New. (struct displaced_step_buffer): New. * displaced-stepping.c (displaced_step_buffer::prepare): New. (write_memory_ptid): Move from infrun.c. (displaced_step_instruction_executed_successfully): New, factored out of displaced_step_finish. (displaced_step_buffer::finish): New. (displaced_step_buffer::copy_insn_closure_by_addr): New. (displaced_step_buffer::restore_in_ptid): New. * gdbarch.sh (displaced_step_location): Remove. (displaced_step_prepare, displaced_step_finish, displaced_step_copy_insn_closure_by_addr, displaced_step_restore_all_in_ptid): New. * gdbarch.c: Re-generate. * gdbarch.h: Re-generate. * gdbthread.h (class thread_info) <displaced_step_state>: New field. (thread_step_over_chain_remove): New declaration. (thread_step_over_chain_next): New declaration. (thread_step_over_chain_length): New declaration. * thread.c (thread_step_over_chain_remove): Make non-static. (thread_step_over_chain_next): New. (global_thread_step_over_chain_next): Use thread_step_over_chain_next. (thread_step_over_chain_length): New. (global_thread_step_over_chain_enqueue): Add debug print. (global_thread_step_over_chain_remove): Add debug print. * infrun.h (get_displaced_step_copy_insn_closure_by_addr): Remove. * infrun.c (get_displaced_stepping_state): New. (displaced_step_in_progress_any_inferior): Remove. (displaced_step_in_progress_thread): Adjust. (displaced_step_in_progress): Adjust. (displaced_step_in_progress_any_thread): New. (get_displaced_step_copy_insn_closure_by_addr): Remove. (gdbarch_supports_displaced_stepping): Use gdbarch_displaced_step_prepare_p. (displaced_step_reset): Change parameter from inferior to thread. (displaced_step_prepare_throw): Implement using gdbarch_displaced_step_prepare. (write_memory_ptid): Move to displaced-step.c. (displaced_step_restore): Remove. (displaced_step_finish): Implement using gdbarch_displaced_step_finish. (start_step_over): Allow starting more than one displaced step. (prepare_for_detach): Handle possibly multiple threads doing displaced steps. (handle_inferior_event): Handle possibility that fork event happens while another thread displaced steps. * linux-tdep.h (linux_displaced_step_prepare): New. (linux_displaced_step_finish): New. (linux_displaced_step_copy_insn_closure_by_addr): New. (linux_displaced_step_restore_all_in_ptid): New. (linux_init_abi): Add supports_displaced_step parameter. * linux-tdep.c (struct linux_info) <disp_step_buf>: New field. (linux_displaced_step_prepare): New. (linux_displaced_step_finish): New. (linux_displaced_step_copy_insn_closure_by_addr): New. (linux_displaced_step_restore_all_in_ptid): New. (linux_init_abi): Add supports_displaced_step parameter, register displaced step methods if true. (_initialize_linux_tdep): Register inferior_execd observer. * amd64-linux-tdep.c (amd64_linux_init_abi_common): Add supports_displaced_step parameter, adjust call to linux_init_abi. Remove call to set_gdbarch_displaced_step_location. (amd64_linux_init_abi): Adjust call to amd64_linux_init_abi_common. (amd64_x32_linux_init_abi): Likewise. * aarch64-linux-tdep.c (aarch64_linux_init_abi): Adjust call to linux_init_abi. Remove call to set_gdbarch_displaced_step_location. * arm-linux-tdep.c (arm_linux_init_abi): Likewise. * i386-linux-tdep.c (i386_linux_init_abi): Likewise. * alpha-linux-tdep.c (alpha_linux_init_abi): Adjust call to linux_init_abi. * arc-linux-tdep.c (arc_linux_init_osabi): Likewise. * bfin-linux-tdep.c (bfin_linux_init_abi): Likewise. * cris-linux-tdep.c (cris_linux_init_abi): Likewise. * csky-linux-tdep.c (csky_linux_init_abi): Likewise. * frv-linux-tdep.c (frv_linux_init_abi): Likewise. * hppa-linux-tdep.c (hppa_linux_init_abi): Likewise. * ia64-linux-tdep.c (ia64_linux_init_abi): Likewise. * m32r-linux-tdep.c (m32r_linux_init_abi): Likewise. * m68k-linux-tdep.c (m68k_linux_init_abi): Likewise. * microblaze-linux-tdep.c (microblaze_linux_init_abi): Likewise. * mips-linux-tdep.c (mips_linux_init_abi): Likewise. * mn10300-linux-tdep.c (am33_linux_init_osabi): Likewise. * nios2-linux-tdep.c (nios2_linux_init_abi): Likewise. * or1k-linux-tdep.c (or1k_linux_init_abi): Likewise. * riscv-linux-tdep.c (riscv_linux_init_abi): Likewise. * s390-linux-tdep.c (s390_linux_init_abi_any): Likewise. * sh-linux-tdep.c (sh_linux_init_abi): Likewise. * sparc-linux-tdep.c (sparc32_linux_init_abi): Likewise. * sparc64-linux-tdep.c (sparc64_linux_init_abi): Likewise. * tic6x-linux-tdep.c (tic6x_uclinux_init_abi): Likewise. * tilegx-linux-tdep.c (tilegx_linux_init_abi): Likewise. * xtensa-linux-tdep.c (xtensa_linux_init_abi): Likewise. * ppc-linux-tdep.c (ppc_linux_init_abi): Adjust call to linux_init_abi. Remove call to set_gdbarch_displaced_step_location. * arm-tdep.c (arm_pc_is_thumb): Call gdbarch_displaced_step_copy_insn_closure_by_addr instead of get_displaced_step_copy_insn_closure_by_addr. * rs6000-aix-tdep.c (rs6000_aix_init_osabi): Adjust calls to clear gdbarch methods. * rs6000-tdep.c (struct ppc_inferior_data): New structure. (get_ppc_per_inferior): New function. (ppc_displaced_step_prepare): New function. (ppc_displaced_step_finish): New function. (ppc_displaced_step_restore_all_in_ptid): New function. (rs6000_gdbarch_init): Register new gdbarch methods. * s390-tdep.c (s390_gdbarch_init): Don't call set_gdbarch_displaced_step_location, set new gdbarch methods. gdb/testsuite/ChangeLog: * gdb.arch/amd64-disp-step-avx.exp: Adjust pattern. * gdb.threads/forking-threads-plus-breakpoint.exp: Likewise. * gdb.threads/non-stop-fair-events.exp: Likewise. Change-Id: I387cd235a442d0620ec43608fd3dc0097fcbf8c8
268 lines
9.9 KiB
C++
268 lines
9.9 KiB
C++
/* Copyright (C) 1986-2020 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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#ifndef INFRUN_H
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#define INFRUN_H 1
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#include "symtab.h"
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#include "gdbsupport/byte-vector.h"
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struct target_waitstatus;
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struct frame_info;
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struct address_space;
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struct return_value_info;
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struct process_stratum_target;
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struct thread_info;
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/* True if we are debugging run control. */
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extern unsigned int debug_infrun;
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/* Print an "infrun" debug statement. */
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#define infrun_debug_printf(fmt, ...) \
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do \
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{ \
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if (debug_infrun) \
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debug_prefixed_printf ("infrun", __func__, fmt, ##__VA_ARGS__); \
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} \
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while (0)
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/* Nonzero if we want to give control to the user when we're notified
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of shared library events by the dynamic linker. */
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extern int stop_on_solib_events;
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/* True if execution commands resume all threads of all processes by
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default; otherwise, resume only threads of the current inferior
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process. */
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extern bool sched_multi;
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/* When set, stop the 'step' command if we enter a function which has
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no line number information. The normal behavior is that we step
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over such function. */
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extern bool step_stop_if_no_debug;
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/* If set, the inferior should be controlled in non-stop mode. In
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this mode, each thread is controlled independently. Execution
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commands apply only to the selected thread by default, and stop
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events stop only the thread that had the event -- the other threads
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are kept running freely. */
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extern bool non_stop;
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/* When set (default), the target should attempt to disable the
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operating system's address space randomization feature when
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starting an inferior. */
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extern bool disable_randomization;
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/* Returns a unique identifier for the current stop. This can be used
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to tell whether a command has proceeded the inferior past the
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current location. */
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extern ULONGEST get_stop_id (void);
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/* Reverse execution. */
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enum exec_direction_kind
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{
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EXEC_FORWARD,
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EXEC_REVERSE
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};
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/* The current execution direction. */
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extern enum exec_direction_kind execution_direction;
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extern void start_remote (int from_tty);
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/* Clear out all variables saying what to do when inferior is
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continued or stepped. First do this, then set the ones you want,
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then call `proceed'. STEP indicates whether we're preparing for a
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step/stepi command. */
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extern void clear_proceed_status (int step);
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extern void proceed (CORE_ADDR, enum gdb_signal);
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/* Return a ptid representing the set of threads that we will proceed,
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in the perspective of the user/frontend. We may actually resume
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fewer threads at first, e.g., if a thread is stopped at a
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breakpoint that needs stepping-off, but that should not be visible
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to the user/frontend, and neither should the frontend/user be
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allowed to proceed any of the threads that happen to be stopped for
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internal run control handling, if a previous command wanted them
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resumed. */
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extern ptid_t user_visible_resume_ptid (int step);
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/* Return the process_stratum target that we will proceed, in the
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perspective of the user/frontend. If RESUME_PTID is
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MINUS_ONE_PTID, then we'll resume all threads of all targets, so
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the function returns NULL. Otherwise, we'll be resuming a process
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or thread of the current process, so we return the current
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inferior's process stratum target. */
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extern process_stratum_target *user_visible_resume_target (ptid_t resume_ptid);
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/* Return control to GDB when the inferior stops for real. Print
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appropriate messages, remove breakpoints, give terminal our modes,
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and run the stop hook. Returns true if the stop hook proceeded the
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target, false otherwise. */
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extern int normal_stop (void);
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/* Return the cached copy of the last target/ptid/waitstatus returned
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by target_wait()/deprecated_target_wait_hook(). The data is
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actually cached by handle_inferior_event(), which gets called
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immediately after target_wait()/deprecated_target_wait_hook(). */
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extern void get_last_target_status (process_stratum_target **target,
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ptid_t *ptid,
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struct target_waitstatus *status);
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/* Set the cached copy of the last target/ptid/waitstatus. */
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extern void set_last_target_status (process_stratum_target *target, ptid_t ptid,
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struct target_waitstatus status);
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/* Clear the cached copy of the last ptid/waitstatus returned by
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target_wait(). */
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extern void nullify_last_target_wait_ptid ();
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/* Stop all threads. Only returns after everything is halted. */
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extern void stop_all_threads (void);
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extern void prepare_for_detach (void);
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extern void fetch_inferior_event ();
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extern void init_wait_for_inferior (void);
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extern void insert_step_resume_breakpoint_at_sal (struct gdbarch *,
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struct symtab_and_line ,
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struct frame_id);
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/* Returns true if we're trying to step past the instruction at
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ADDRESS in ASPACE. */
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extern int stepping_past_instruction_at (struct address_space *aspace,
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CORE_ADDR address);
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/* Returns true if thread whose thread number is THREAD is stepping
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over a breakpoint. */
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extern int thread_is_stepping_over_breakpoint (int thread);
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/* Returns true if we're trying to step past an instruction that
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triggers a non-steppable watchpoint. */
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extern int stepping_past_nonsteppable_watchpoint (void);
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/* Record in TP the frame and location we're currently stepping through. */
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extern void set_step_info (thread_info *tp,
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struct frame_info *frame,
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struct symtab_and_line sal);
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/* Several print_*_reason helper functions to print why the inferior
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has stopped to the passed in UIOUT. */
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/* Signal received, print why the inferior has stopped. */
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extern void print_signal_received_reason (struct ui_out *uiout,
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enum gdb_signal siggnal);
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/* Print why the inferior has stopped. We are done with a
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step/next/si/ni command, print why the inferior has stopped. */
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extern void print_end_stepping_range_reason (struct ui_out *uiout);
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/* The inferior was terminated by a signal, print why it stopped. */
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extern void print_signal_exited_reason (struct ui_out *uiout,
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enum gdb_signal siggnal);
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/* The inferior program is finished, print why it stopped. */
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extern void print_exited_reason (struct ui_out *uiout, int exitstatus);
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/* Reverse execution: target ran out of history info, print why the
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inferior has stopped. */
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extern void print_no_history_reason (struct ui_out *uiout);
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/* Print the result of a function at the end of a 'finish' command.
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RV points at an object representing the captured return value/type
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and its position in the value history. */
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extern void print_return_value (struct ui_out *uiout,
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struct return_value_info *rv);
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/* Print current location without a level number, if we have changed
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functions or hit a breakpoint. Print source line if we have one.
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If the execution command captured a return value, print it. If
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DISPLAYS is false, do not call 'do_displays'. */
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extern void print_stop_event (struct ui_out *uiout, bool displays = true);
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/* Pretty print the results of target_wait, for debugging purposes. */
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extern void print_target_wait_results (ptid_t waiton_ptid, ptid_t result_ptid,
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const struct target_waitstatus *ws);
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extern int signal_stop_state (int);
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extern int signal_print_state (int);
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extern int signal_pass_state (int);
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extern int signal_stop_update (int, int);
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extern int signal_print_update (int, int);
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extern int signal_pass_update (int, int);
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extern void update_signals_program_target (void);
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/* Clear the convenience variables associated with the exit of the
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inferior. Currently, those variables are $_exitcode and
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$_exitsignal. */
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extern void clear_exit_convenience_vars (void);
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/* Dump LEN bytes at BUF in hex to a string and return it. */
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extern std::string displaced_step_dump_bytes (const gdb_byte *buf, size_t len);
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extern void update_observer_mode (void);
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extern void signal_catch_update (const unsigned int *);
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/* In some circumstances we allow a command to specify a numeric
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signal. The idea is to keep these circumstances limited so that
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users (and scripts) develop portable habits. For comparison,
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POSIX.2 `kill' requires that 1,2,3,6,9,14, and 15 work (and using a
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numeric signal at all is obsolescent. We are slightly more lenient
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and allow 1-15 which should match host signal numbers on most
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systems. Use of symbolic signal names is strongly encouraged. */
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enum gdb_signal gdb_signal_from_command (int num);
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/* Enables/disables infrun's async event source in the event loop. */
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extern void infrun_async (int enable);
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/* Call infrun's event handler the next time through the event
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loop. */
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extern void mark_infrun_async_event_handler (void);
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/* The global chain of threads that need to do a step-over operation
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to get past e.g., a breakpoint. */
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extern struct thread_info *global_thread_step_over_chain_head;
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/* Remove breakpoints if possible (usually that means, if everything
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is stopped). On failure, print a message. */
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extern void maybe_remove_breakpoints (void);
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/* If a UI was in sync execution mode, and now isn't, restore its
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prompt (a synchronous execution command has finished, and we're
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ready for input). */
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extern void all_uis_check_sync_execution_done (void);
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/* If a UI was in sync execution mode, and hasn't displayed the prompt
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yet, re-disable its prompt (a synchronous execution command was
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started or re-started). */
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extern void all_uis_on_sync_execution_starting (void);
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#endif /* INFRUN_H */
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