de0d863ec3
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.
163 lines
6.1 KiB
C
163 lines
6.1 KiB
C
/* Copyright (C) 2011-2015 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 COMMON_LINUX_PTRACE_H
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#define COMMON_LINUX_PTRACE_H
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struct buffer;
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#include <sys/ptrace.h>
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#ifdef __UCLIBC__
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#if !(defined(__UCLIBC_HAS_MMU__) || defined(__ARCH_HAS_MMU__))
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/* PTRACE_TEXT_ADDR and friends. */
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#include <asm/ptrace.h>
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#define HAS_NOMMU
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#endif
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#endif
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#if !defined(PTRACE_TYPE_ARG3)
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#define PTRACE_TYPE_ARG3 void *
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#endif
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#if !defined(PTRACE_TYPE_ARG4)
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#define PTRACE_TYPE_ARG4 void *
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#endif
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#ifndef PTRACE_GETSIGINFO
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# define PTRACE_GETSIGINFO 0x4202
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# define PTRACE_SETSIGINFO 0x4203
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#endif /* PTRACE_GETSIGINF */
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/* If the system headers did not provide the constants, hard-code the normal
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values. */
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#ifndef PTRACE_EVENT_FORK
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#define PTRACE_SETOPTIONS 0x4200
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#define PTRACE_GETEVENTMSG 0x4201
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/* options set using PTRACE_SETOPTIONS */
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#define PTRACE_O_TRACESYSGOOD 0x00000001
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#define PTRACE_O_TRACEFORK 0x00000002
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#define PTRACE_O_TRACEVFORK 0x00000004
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#define PTRACE_O_TRACECLONE 0x00000008
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#define PTRACE_O_TRACEEXEC 0x00000010
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#define PTRACE_O_TRACEVFORKDONE 0x00000020
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#define PTRACE_O_TRACEEXIT 0x00000040
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/* Wait extended result codes for the above trace options. */
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#define PTRACE_EVENT_FORK 1
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#define PTRACE_EVENT_VFORK 2
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#define PTRACE_EVENT_CLONE 3
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#define PTRACE_EVENT_EXEC 4
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#define PTRACE_EVENT_VFORK_DONE 5
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#define PTRACE_EVENT_EXIT 6
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#endif /* PTRACE_EVENT_FORK */
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#ifndef PTRACE_O_EXITKILL
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/* Only defined in Linux Kernel 3.8 or later. */
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#define PTRACE_O_EXITKILL 0x00100000
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#endif
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#if (defined __bfin__ || defined __frv__ || defined __sh__) \
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&& !defined PTRACE_GETFDPIC
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#define PTRACE_GETFDPIC 31
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#define PTRACE_GETFDPIC_EXEC 0
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#define PTRACE_GETFDPIC_INTERP 1
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#endif
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/* We can't always assume that this flag is available, but all systems
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with the ptrace event handlers also have __WALL, so it's safe to use
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in some contexts. */
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#ifndef __WALL
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#define __WALL 0x40000000 /* Wait for any child. */
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#endif
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/* True if whether a breakpoint/watchpoint triggered can be determined
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from the si_code of SIGTRAP's siginfo_t (TRAP_BRKPT/TRAP_HWBKPT).
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That is, if the kernel can tell us whether the thread executed a
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software breakpoint, we trust it. The kernel will be determining
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that from the hardware (e.g., from which exception was raised in
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the CPU). Relying on whether a breakpoint is planted in memory at
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the time the SIGTRAP is processed to determine whether the thread
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stopped for a software breakpoint can be too late. E.g., the
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breakpoint could have been removed since. Or the thread could have
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stepped an instruction the size of a breakpoint instruction, and
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before the stop is processed a breakpoint is inserted at its
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address. Getting these wrong is disastrous on decr_pc_after_break
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architectures. The moribund location mechanism helps with that
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somewhat but it is an heuristic, and can well fail. Getting that
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information out of the kernel and ultimately out of the CPU is the
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way to go. That said, some architecture may get the si_code wrong,
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and as such we're leaving fallback code in place. We'll remove
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this after a while if no problem is reported. */
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#define USE_SIGTRAP_SIGINFO 1
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/* The x86 kernel gets some of the si_code values backwards, like
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this:
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| what | si_code |
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|------------------------------------------+------------|
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| software breakpoints (int3) | SI_KERNEL |
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| single-steps | TRAP_TRACE |
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| single-stepping a syscall | TRAP_BRKPT |
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| user sent SIGTRAP | 0 |
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| exec SIGTRAP (when no PTRACE_EVENT_EXEC) | 0 |
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| hardware breakpoints/watchpoints | TRAP_HWBPT |
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That is, it reports SI_KERNEL for software breakpoints (and only
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for those), and TRAP_BRKPT for single-stepping a syscall... If the
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kernel is ever fixed, we'll just have to detect it like we detect
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optional ptrace features: by forking and debugging ourselves,
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running to a breakpoint and checking what comes out of
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siginfo->si_code.
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The generic Linux target code should use GDB_ARCH_TRAP_BRKPT
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instead of TRAP_BRKPT to abstract out this x86 peculiarity. */
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#if defined __i386__ || defined __x86_64__
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# define GDB_ARCH_TRAP_BRKPT SI_KERNEL
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#else
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# define GDB_ARCH_TRAP_BRKPT TRAP_BRKPT
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#endif
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#ifndef TRAP_HWBKPT
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# define TRAP_HWBKPT 4
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#endif
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extern void linux_ptrace_attach_fail_reason (pid_t pid, struct buffer *buffer);
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/* Find all possible reasons we could have failed to attach to PTID
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and return them as a string. ERR is the error PTRACE_ATTACH failed
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with (an errno). The result is stored in a static buffer. This
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string should be copied into a buffer by the client if the string
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will not be immediately used, or if it must persist. */
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extern char *linux_ptrace_attach_fail_reason_string (ptid_t ptid, int err);
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extern void linux_ptrace_init_warnings (void);
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extern void linux_check_ptrace_features (void);
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extern void linux_enable_event_reporting (pid_t pid, int attached);
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extern void linux_disable_event_reporting (pid_t pid);
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extern int linux_supports_tracefork (void);
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extern int linux_supports_traceclone (void);
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extern int linux_supports_tracevforkdone (void);
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extern int linux_supports_tracesysgood (void);
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extern int linux_ptrace_get_extended_event (int wstat);
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extern int linux_is_extended_waitstatus (int wstat);
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extern int linux_wstatus_maybe_breakpoint (int wstat);
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#endif /* COMMON_LINUX_PTRACE_H */
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