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/* Low level interface to ptrace, for the remote server for GDB.
Copyright (C) 1995-2021 Free Software Foundation, Inc.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include "server.h"
#include "linux-low.h"
#include "nat/linux-osdata.h"
#include "gdbsupport/agent.h"
#include "tdesc.h"
#include "gdbsupport/rsp-low.h"
#include "gdbsupport/signals-state-save-restore.h"
#include "nat/linux-nat.h"
#include "nat/linux-waitpid.h"
#include "gdbsupport/gdb_wait.h"
#include "nat/gdb_ptrace.h"
#include "nat/linux-ptrace.h"
#include "nat/linux-procfs.h"
#include "nat/linux-personality.h"
#include <signal.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/syscall.h>
#include <sched.h>
#include <ctype.h>
#include <pwd.h>
#include <sys/types.h>
#include <dirent.h>
#include <sys/stat.h>
#include <sys/vfs.h>
#include <sys/uio.h>
#include "gdbsupport/filestuff.h"
#include "tracepoint.h"
#include <inttypes.h>
#include "gdbsupport/common-inferior.h"
#include "nat/fork-inferior.h"
#include "gdbsupport/environ.h"
#include "gdbsupport/gdb-sigmask.h"
#include "gdbsupport/scoped_restore.h"
#ifndef ELFMAG0
/* Don't include <linux/elf.h> here. If it got included by gdb_proc_service.h
then ELFMAG0 will have been defined. If it didn't get included by
gdb_proc_service.h then including it will likely introduce a duplicate
definition of elf_fpregset_t. */
#include <elf.h>
#endif
#include "nat/linux-namespaces.h"
#ifndef O_LARGEFILE
#define O_LARGEFILE 0
#endif
#ifndef AT_HWCAP2
#define AT_HWCAP2 26
#endif
/* Some targets did not define these ptrace constants from the start,
so gdbserver defines them locally here. In the future, these may
be removed after they are added to asm/ptrace.h. */
#if !(defined(PT_TEXT_ADDR) \
|| defined(PT_DATA_ADDR) \
|| defined(PT_TEXT_END_ADDR))
#if defined(__mcoldfire__)
/* These are still undefined in 3.10 kernels. */
#define PT_TEXT_ADDR 49*4
#define PT_DATA_ADDR 50*4
#define PT_TEXT_END_ADDR 51*4
/* These are still undefined in 3.10 kernels. */
#elif defined(__TMS320C6X__)
#define PT_TEXT_ADDR (0x10000*4)
#define PT_DATA_ADDR (0x10004*4)
#define PT_TEXT_END_ADDR (0x10008*4)
#endif
#endif
#if (defined(__UCLIBC__) \
&& defined(HAS_NOMMU) \
&& defined(PT_TEXT_ADDR) \
&& defined(PT_DATA_ADDR) \
&& defined(PT_TEXT_END_ADDR))
#define SUPPORTS_READ_OFFSETS
#endif
#ifdef HAVE_LINUX_BTRACE
# include "nat/linux-btrace.h"
# include "gdbsupport/btrace-common.h"
#endif
#ifndef HAVE_ELF32_AUXV_T
/* Copied from glibc's elf.h. */
typedef struct
{
uint32_t a_type; /* Entry type */
union
{
uint32_t a_val; /* Integer value */
/* We use to have pointer elements added here. We cannot do that,
though, since it does not work when using 32-bit definitions
on 64-bit platforms and vice versa. */
} a_un;
} Elf32_auxv_t;
#endif
#ifndef HAVE_ELF64_AUXV_T
/* Copied from glibc's elf.h. */
typedef struct
{
uint64_t a_type; /* Entry type */
union
{
uint64_t a_val; /* Integer value */
/* We use to have pointer elements added here. We cannot do that,
though, since it does not work when using 32-bit definitions
on 64-bit platforms and vice versa. */
} a_un;
} Elf64_auxv_t;
#endif
/* Does the current host support PTRACE_GETREGSET? */
int have_ptrace_getregset = -1;
/* LWP accessors. */
/* See nat/linux-nat.h. */
ptid_t
ptid_of_lwp (struct lwp_info *lwp)
{
return ptid_of (get_lwp_thread (lwp));
}
/* See nat/linux-nat.h. */
void
lwp_set_arch_private_info (struct lwp_info *lwp,
struct arch_lwp_info *info)
{
lwp->arch_private = info;
}
/* See nat/linux-nat.h. */
struct arch_lwp_info *
lwp_arch_private_info (struct lwp_info *lwp)
{
return lwp->arch_private;
}
/* See nat/linux-nat.h. */
int
lwp_is_stopped (struct lwp_info *lwp)
{
return lwp->stopped;
}
/* See nat/linux-nat.h. */
enum target_stop_reason
lwp_stop_reason (struct lwp_info *lwp)
{
return lwp->stop_reason;
}
/* See nat/linux-nat.h. */
int
lwp_is_stepping (struct lwp_info *lwp)
{
return lwp->stepping;
}
/* A list of all unknown processes which receive stop signals. Some
other process will presumably claim each of these as forked
children momentarily. */
struct simple_pid_list
{
/* The process ID. */
int pid;
/* The status as reported by waitpid. */
int status;
/* Next in chain. */
struct simple_pid_list *next;
};
static struct simple_pid_list *stopped_pids;
/* Trivial list manipulation functions to keep track of a list of new
stopped processes. */
static void
add_to_pid_list (struct simple_pid_list **listp, int pid, int status)
{
struct simple_pid_list *new_pid = XNEW (struct simple_pid_list);
new_pid->pid = pid;
new_pid->status = status;
new_pid->next = *listp;
*listp = new_pid;
}
static int
pull_pid_from_list (struct simple_pid_list **listp, int pid, int *statusp)
{
struct simple_pid_list **p;
for (p = listp; *p != NULL; p = &(*p)->next)
if ((*p)->pid == pid)
{
struct simple_pid_list *next = (*p)->next;
*statusp = (*p)->status;
xfree (*p);
*p = next;
return 1;
}
return 0;
}
enum stopping_threads_kind
{
/* Not stopping threads presently. */
NOT_STOPPING_THREADS,
/* Stopping threads. */
STOPPING_THREADS,
/* Stopping and suspending threads. */
STOPPING_AND_SUSPENDING_THREADS
};
/* This is set while stop_all_lwps is in effect. */
static stopping_threads_kind stopping_threads = NOT_STOPPING_THREADS;
/* FIXME make into a target method? */
int using_threads = 1;
/* True if we're presently stabilizing threads (moving them out of
jump pads). */
static int stabilizing_threads;
static void unsuspend_all_lwps (struct lwp_info *except);
static void mark_lwp_dead (struct lwp_info *lwp, int wstat);
static int lwp_is_marked_dead (struct lwp_info *lwp);
static int kill_lwp (unsigned long lwpid, int signo);
static void enqueue_pending_signal (struct lwp_info *lwp, int signal, siginfo_t *info);
static int linux_low_ptrace_options (int attached);
static int check_ptrace_stopped_lwp_gone (struct lwp_info *lp);
/* When the event-loop is doing a step-over, this points at the thread
being stepped. */
static ptid_t step_over_bkpt;
bool
linux_process_target::low_supports_breakpoints ()
{
return false;
}
CORE_ADDR
linux_process_target::low_get_pc (regcache *regcache)
{
return 0;
}
void
linux_process_target::low_set_pc (regcache *regcache, CORE_ADDR newpc)
{
gdb_assert_not_reached ("linux target op low_set_pc is not implemented");
}
std::vector<CORE_ADDR>
linux_process_target::low_get_next_pcs (regcache *regcache)
{
gdb_assert_not_reached ("linux target op low_get_next_pcs is not "
"implemented");
}
int
linux_process_target::low_decr_pc_after_break ()
{
return 0;
}
/* True if LWP is stopped in its stepping range. */
static int
lwp_in_step_range (struct lwp_info *lwp)
{
CORE_ADDR pc = lwp->stop_pc;
return (pc >= lwp->step_range_start && pc < lwp->step_range_end);
}
/* The read/write ends of the pipe registered as waitable file in the
event loop. */
static int linux_event_pipe[2] = { -1, -1 };
/* True if we're currently in async mode. */
#define target_is_async_p() (linux_event_pipe[0] != -1)
static void send_sigstop (struct lwp_info *lwp);
/* Return non-zero if HEADER is a 64-bit ELF file. */
static int
elf_64_header_p (const Elf64_Ehdr *header, unsigned int *machine)
{
if (header->e_ident[EI_MAG0] == ELFMAG0
&& header->e_ident[EI_MAG1] == ELFMAG1
&& header->e_ident[EI_MAG2] == ELFMAG2
&& header->e_ident[EI_MAG3] == ELFMAG3)
{
*machine = header->e_machine;
return header->e_ident[EI_CLASS] == ELFCLASS64;
}
*machine = EM_NONE;
return -1;
}
/* Return non-zero if FILE is a 64-bit ELF file,
zero if the file is not a 64-bit ELF file,
and -1 if the file is not accessible or doesn't exist. */
static int
elf_64_file_p (const char *file, unsigned int *machine)
{
Elf64_Ehdr header;
int fd;
fd = open (file, O_RDONLY);
if (fd < 0)
return -1;
if (read (fd, &header, sizeof (header)) != sizeof (header))
{
close (fd);
return 0;
}
close (fd);
return elf_64_header_p (&header, machine);
}
/* Accepts an integer PID; Returns true if the executable PID is
running is a 64-bit ELF file.. */
int
linux_pid_exe_is_elf_64_file (int pid, unsigned int *machine)
{
char file[PATH_MAX];
sprintf (file, "/proc/%d/exe", pid);
return elf_64_file_p (file, machine);
}
void
linux_process_target::delete_lwp (lwp_info *lwp)
{
struct thread_info *thr = get_lwp_thread (lwp);
if (debug_threads)
debug_printf ("deleting %ld\n", lwpid_of (thr));
remove_thread (thr);
low_delete_thread (lwp->arch_private);
delete lwp;
}
void
linux_process_target::low_delete_thread (arch_lwp_info *info)
{
/* Default implementation should be overridden if architecture-specific
info is being used. */
gdb_assert (info == nullptr);
}
process_info *
linux_process_target::add_linux_process (int pid, int attached)
{
struct process_info *proc;
proc = add_process (pid, attached);
proc->priv = XCNEW (struct process_info_private);
proc->priv->arch_private = low_new_process ();
return proc;
}
arch_process_info *
linux_process_target::low_new_process ()
{
return nullptr;
}
void
linux_process_target::low_delete_process (arch_process_info *info)
{
/* Default implementation must be overridden if architecture-specific
info exists. */
gdb_assert (info == nullptr);
}
void
linux_process_target::low_new_fork (process_info *parent, process_info *child)
{
/* Nop. */
}
void
linux_process_target::arch_setup_thread (thread_info *thread)
{
struct thread_info *saved_thread;
saved_thread = current_thread;
current_thread = thread;
low_arch_setup ();
current_thread = saved_thread;
}
int
linux_process_target::handle_extended_wait (lwp_info **orig_event_lwp,
int wstat)
{
client_state &cs = get_client_state ();
struct lwp_info *event_lwp = *orig_event_lwp;
int event = linux_ptrace_get_extended_event (wstat);
struct thread_info *event_thr = get_lwp_thread (event_lwp);
struct lwp_info *new_lwp;
gdb_assert (event_lwp->waitstatus.kind == TARGET_WAITKIND_IGNORE);
/* All extended events we currently use are mid-syscall. Only
PTRACE_EVENT_STOP is delivered more like a signal-stop, but
you have to be using PTRACE_SEIZE to get that. */
event_lwp->syscall_state = TARGET_WAITKIND_SYSCALL_ENTRY;
if ((event == PTRACE_EVENT_FORK) || (event == PTRACE_EVENT_VFORK)
|| (event == PTRACE_EVENT_CLONE))
{
ptid_t ptid;
unsigned long new_pid;
int ret, status;
/* Get the pid of the new lwp. */
ptrace (PTRACE_GETEVENTMSG, lwpid_of (event_thr), (PTRACE_TYPE_ARG3) 0,
&new_pid);
/* If we haven't already seen the new PID stop, wait for it now. */
if (!pull_pid_from_list (&stopped_pids, new_pid, &status))
{
/* The new child has a pending SIGSTOP. We can't affect it until it
hits the SIGSTOP, but we're already attached. */
ret = my_waitpid (new_pid, &status, __WALL);
if (ret == -1)
perror_with_name ("waiting for new child");
else if (ret != new_pid)
warning ("wait returned unexpected PID %d", ret);
else if (!WIFSTOPPED (status))
warning ("wait returned unexpected status 0x%x", status);
}
if (event == PTRACE_EVENT_FORK || event == PTRACE_EVENT_VFORK)
{
struct process_info *parent_proc;
struct process_info *child_proc;
struct lwp_info *child_lwp;
struct thread_info *child_thr;
ptid = ptid_t (new_pid, new_pid);
if (debug_threads)
{
debug_printf ("HEW: Got fork event from LWP %ld, "
"new child is %d\n",
ptid_of (event_thr).lwp (),
ptid.pid ());
}
/* Add the new process to the tables and clone the breakpoint
lists of the parent. We need to do this even if the new process
will be detached, since we will need the process object and the
breakpoints to remove any breakpoints from memory when we
detach, and the client side will access registers. */
child_proc = add_linux_process (new_pid, 0);
gdb_assert (child_proc != NULL);
child_lwp = add_lwp (ptid);
gdb_assert (child_lwp != NULL);
child_lwp->stopped = 1;
child_lwp->must_set_ptrace_flags = 1;
child_lwp->status_pending_p = 0;
child_thr = get_lwp_thread (child_lwp);
child_thr->last_resume_kind = resume_stop;
child_thr->last_status.kind = TARGET_WAITKIND_STOPPED;
/* If we're suspending all threads, leave this one suspended
too. If the fork/clone parent is stepping over a breakpoint,
all other threads have been suspended already. Leave the
child suspended too. */
if (stopping_threads == STOPPING_AND_SUSPENDING_THREADS
|| event_lwp->bp_reinsert != 0)
{
if (debug_threads)
debug_printf ("HEW: leaving child suspended\n");
child_lwp->suspended = 1;
}
parent_proc = get_thread_process (event_thr);
child_proc->attached = parent_proc->attached;
if (event_lwp->bp_reinsert != 0
&& supports_software_single_step ()
&& event == PTRACE_EVENT_VFORK)
{
/* If we leave single-step breakpoints there, child will
hit it, so uninsert single-step breakpoints from parent
(and child). Once vfork child is done, reinsert
them back to parent. */
uninsert_single_step_breakpoints (event_thr);
}
clone_all_breakpoints (child_thr, event_thr);
target_desc_up tdesc = allocate_target_description ();
copy_target_description (tdesc.get (), parent_proc->tdesc);
child_proc->tdesc = tdesc.release ();
/* Clone arch-specific process data. */
low_new_fork (parent_proc, child_proc);
/* Save fork info in the parent thread. */
if (event == PTRACE_EVENT_FORK)
event_lwp->waitstatus.kind = TARGET_WAITKIND_FORKED;
else if (event == PTRACE_EVENT_VFORK)
event_lwp->waitstatus.kind = TARGET_WAITKIND_VFORKED;
event_lwp->waitstatus.value.related_pid = ptid;
/* The status_pending field contains bits denoting the
extended event, so when the pending event is handled,
the handler will look at lwp->waitstatus. */
event_lwp->status_pending_p = 1;
event_lwp->status_pending = wstat;
/* Link the threads until the parent event is passed on to
higher layers. */
event_lwp->fork_relative = child_lwp;
child_lwp->fork_relative = event_lwp;
/* If the parent thread is doing step-over with single-step
breakpoints, the list of single-step breakpoints are cloned
from the parent's. Remove them from the child process.
In case of vfork, we'll reinsert them back once vforked
child is done. */
if (event_lwp->bp_reinsert != 0
&& supports_software_single_step ())
{
/* The child process is forked and stopped, so it is safe
to access its memory without stopping all other threads
from other processes. */
delete_single_step_breakpoints (child_thr);
gdb_assert (has_single_step_breakpoints (event_thr));
gdb_assert (!has_single_step_breakpoints (child_thr));
}
/* Report the event. */
return 0;
}
if (debug_threads)
debug_printf ("HEW: Got clone event "
"from LWP %ld, new child is LWP %ld\n",
lwpid_of (event_thr), new_pid);
ptid = ptid_t (pid_of (event_thr), new_pid);
new_lwp = add_lwp (ptid);
/* Either we're going to immediately resume the new thread
or leave it stopped. resume_one_lwp is a nop if it
thinks the thread is currently running, so set this first
before calling resume_one_lwp. */
new_lwp->stopped = 1;
/* If we're suspending all threads, leave this one suspended
too. If the fork/clone parent is stepping over a breakpoint,
all other threads have been suspended already. Leave the
child suspended too. */
if (stopping_threads == STOPPING_AND_SUSPENDING_THREADS
|| event_lwp->bp_reinsert != 0)
new_lwp->suspended = 1;
/* Normally we will get the pending SIGSTOP. But in some cases
we might get another signal delivered to the group first.
If we do get another signal, be sure not to lose it. */
if (WSTOPSIG (status) != SIGSTOP)
{
new_lwp->stop_expected = 1;
new_lwp->status_pending_p = 1;
new_lwp->status_pending = status;
}
else if (cs.report_thread_events)
{
new_lwp->waitstatus.kind = TARGET_WAITKIND_THREAD_CREATED;
new_lwp->status_pending_p = 1;
new_lwp->status_pending = status;
}
#ifdef USE_THREAD_DB
thread_db_notice_clone (event_thr, ptid);
#endif
/* Don't report the event. */
return 1;
}
else if (event == PTRACE_EVENT_VFORK_DONE)
{
event_lwp->waitstatus.kind = TARGET_WAITKIND_VFORK_DONE;
if (event_lwp->bp_reinsert != 0 && supports_software_single_step ())
{
reinsert_single_step_breakpoints (event_thr);
gdb_assert (has_single_step_breakpoints (event_thr));
}
/* Report the event. */
return 0;
}
else if (event == PTRACE_EVENT_EXEC && cs.report_exec_events)
{
struct process_info *proc;
std::vector<int> syscalls_to_catch;
ptid_t event_ptid;
pid_t event_pid;
if (debug_threads)
{
debug_printf ("HEW: Got exec event from LWP %ld\n",
lwpid_of (event_thr));
}
/* Get the event ptid. */
event_ptid = ptid_of (event_thr);
event_pid = event_ptid.pid ();
/* Save the syscall list from the execing process. */
proc = get_thread_process (event_thr);
syscalls_to_catch = std::move (proc->syscalls_to_catch);
/* Delete the execing process and all its threads. */
mourn (proc);
current_thread = NULL;
/* Create a new process/lwp/thread. */
proc = add_linux_process (event_pid, 0);
event_lwp = add_lwp (event_ptid);
event_thr = get_lwp_thread (event_lwp);
gdb_assert (current_thread == event_thr);
arch_setup_thread (event_thr);
/* Set the event status. */
event_lwp->waitstatus.kind = TARGET_WAITKIND_EXECD;
event_lwp->waitstatus.value.execd_pathname
= xstrdup (linux_proc_pid_to_exec_file (lwpid_of (event_thr)));
/* Mark the exec status as pending. */
event_lwp->stopped = 1;
event_lwp->status_pending_p = 1;
event_lwp->status_pending = wstat;
event_thr->last_resume_kind = resume_continue;
event_thr->last_status.kind = TARGET_WAITKIND_IGNORE;
/* Update syscall state in the new lwp, effectively mid-syscall too. */
event_lwp->syscall_state = TARGET_WAITKIND_SYSCALL_ENTRY;
/* Restore the list to catch. Don't rely on the client, which is free
to avoid sending a new list when the architecture doesn't change.
Also, for ANY_SYSCALL, the architecture doesn't really matter. */
proc->syscalls_to_catch = std::move (syscalls_to_catch);
/* Report the event. */
*orig_event_lwp = event_lwp;
return 0;
}
internal_error (__FILE__, __LINE__, _("unknown ptrace event %d"), event);
}
CORE_ADDR
linux_process_target::get_pc (lwp_info *lwp)
{
struct thread_info *saved_thread;
struct regcache *regcache;
CORE_ADDR pc;
if (!low_supports_breakpoints ())
return 0;
saved_thread = current_thread;
current_thread = get_lwp_thread (lwp);
regcache = get_thread_regcache (current_thread, 1);
pc = low_get_pc (regcache);
if (debug_threads)
debug_printf ("pc is 0x%lx\n", (long) pc);
current_thread = saved_thread;
return pc;
}
void
linux_process_target::get_syscall_trapinfo (lwp_info *lwp, int *sysno)
{
struct thread_info *saved_thread;
struct regcache *regcache;
saved_thread = current_thread;
current_thread = get_lwp_thread (lwp);
regcache = get_thread_regcache (current_thread, 1);
low_get_syscall_trapinfo (regcache, sysno);
if (debug_threads)
debug_printf ("get_syscall_trapinfo sysno %d\n", *sysno);
current_thread = saved_thread;
}
void
linux_process_target::low_get_syscall_trapinfo (regcache *regcache, int *sysno)
{
/* By default, report an unknown system call number. */
*sysno = UNKNOWN_SYSCALL;
}
bool
linux_process_target::save_stop_reason (lwp_info *lwp)
{
CORE_ADDR pc;
CORE_ADDR sw_breakpoint_pc;
struct thread_info *saved_thread;
#if USE_SIGTRAP_SIGINFO
siginfo_t siginfo;
#endif
if (!low_supports_breakpoints ())
return false;
pc = get_pc (lwp);
sw_breakpoint_pc = pc - low_decr_pc_after_break ();
/* breakpoint_at reads from the current thread. */
saved_thread = current_thread;
current_thread = get_lwp_thread (lwp);
#if USE_SIGTRAP_SIGINFO
if (ptrace (PTRACE_GETSIGINFO, lwpid_of (current_thread),
(PTRACE_TYPE_ARG3) 0, &siginfo) == 0)
{
if (siginfo.si_signo == SIGTRAP)
{
if (GDB_ARCH_IS_TRAP_BRKPT (siginfo.si_code)
&& GDB_ARCH_IS_TRAP_HWBKPT (siginfo.si_code))
{
/* The si_code is ambiguous on this arch -- check debug
registers. */
if (!check_stopped_by_watchpoint (lwp))
lwp->stop_reason = TARGET_STOPPED_BY_SW_BREAKPOINT;
}
else if (GDB_ARCH_IS_TRAP_BRKPT (siginfo.si_code))
{
/* If we determine the LWP stopped for a SW breakpoint,
trust it. Particularly don't check watchpoint
registers, because at least on s390, we'd find
stopped-by-watchpoint as long as there's a watchpoint
set. */
lwp->stop_reason = TARGET_STOPPED_BY_SW_BREAKPOINT;
}
else if (GDB_ARCH_IS_TRAP_HWBKPT (siginfo.si_code))
{
/* This can indicate either a hardware breakpoint or
hardware watchpoint. Check debug registers. */
if (!check_stopped_by_watchpoint (lwp))
lwp->stop_reason = TARGET_STOPPED_BY_HW_BREAKPOINT;
}
else if (siginfo.si_code == TRAP_TRACE)
{
/* We may have single stepped an instruction that
triggered a watchpoint. In that case, on some
architectures (such as x86), instead of TRAP_HWBKPT,
si_code indicates TRAP_TRACE, and we need to check
the debug registers separately. */
if (!check_stopped_by_watchpoint (lwp))
lwp->stop_reason = TARGET_STOPPED_BY_SINGLE_STEP;
}
}
}
#else
/* We may have just stepped a breakpoint instruction. E.g., in
non-stop mode, GDB first tells the thread A to step a range, and
then the user inserts a breakpoint inside the range. In that
case we need to report the breakpoint PC. */
if ((!lwp->stepping || lwp->stop_pc == sw_breakpoint_pc)
&& low_breakpoint_at (sw_breakpoint_pc))
lwp->stop_reason = TARGET_STOPPED_BY_SW_BREAKPOINT;
if (hardware_breakpoint_inserted_here (pc))
lwp->stop_reason = TARGET_STOPPED_BY_HW_BREAKPOINT;
if (lwp->stop_reason == TARGET_STOPPED_BY_NO_REASON)
check_stopped_by_watchpoint (lwp);
#endif
if (lwp->stop_reason == TARGET_STOPPED_BY_SW_BREAKPOINT)
{
if (debug_threads)
{
struct thread_info *thr = get_lwp_thread (lwp);
debug_printf ("CSBB: %s stopped by software breakpoint\n",
target_pid_to_str (ptid_of (thr)));
}
/* Back up the PC if necessary. */
if (pc != sw_breakpoint_pc)
{
struct regcache *regcache
= get_thread_regcache (current_thread, 1);
low_set_pc (regcache, sw_breakpoint_pc);
}
/* Update this so we record the correct stop PC below. */
pc = sw_breakpoint_pc;
}
else if (lwp->stop_reason == TARGET_STOPPED_BY_HW_BREAKPOINT)
{
if (debug_threads)
{
struct thread_info *thr = get_lwp_thread (lwp);
debug_printf ("CSBB: %s stopped by hardware breakpoint\n",
target_pid_to_str (ptid_of (thr)));
}
}
else if (lwp->stop_reason == TARGET_STOPPED_BY_WATCHPOINT)
{
if (debug_threads)
{
struct thread_info *thr = get_lwp_thread (lwp);
debug_printf ("CSBB: %s stopped by hardware watchpoint\n",
target_pid_to_str (ptid_of (thr)));
}
}
else if (lwp->stop_reason == TARGET_STOPPED_BY_SINGLE_STEP)
{
if (debug_threads)
{
struct thread_info *thr = get_lwp_thread (lwp);
debug_printf ("CSBB: %s stopped by trace\n",
target_pid_to_str (ptid_of (thr)));
}
}
lwp->stop_pc = pc;
current_thread = saved_thread;
return true;
}
lwp_info *
linux_process_target::add_lwp (ptid_t ptid)
{
struct lwp_info *lwp;
lwp = new lwp_info {};
lwp->waitstatus.kind = TARGET_WAITKIND_IGNORE;
lwp->thread = add_thread (ptid, lwp);
low_new_thread (lwp);
return lwp;
}
void
linux_process_target::low_new_thread (lwp_info *info)
{
/* Nop. */
}
/* Callback to be used when calling fork_inferior, responsible for
actually initiating the tracing of the inferior. */
static void
linux_ptrace_fun ()
{
if (ptrace (PTRACE_TRACEME, 0, (PTRACE_TYPE_ARG3) 0,
(PTRACE_TYPE_ARG4) 0) < 0)
trace_start_error_with_name ("ptrace");
if (setpgid (0, 0) < 0)
trace_start_error_with_name ("setpgid");
/* If GDBserver is connected to gdb via stdio, redirect the inferior's
stdout to stderr so that inferior i/o doesn't corrupt the connection.
Also, redirect stdin to /dev/null. */
if (remote_connection_is_stdio ())
{
if (close (0) < 0)
trace_start_error_with_name ("close");
if (open ("/dev/null", O_RDONLY) < 0)
trace_start_error_with_name ("open");
if (dup2 (2, 1) < 0)
trace_start_error_with_name ("dup2");
if (write (2, "stdin/stdout redirected\n",
sizeof ("stdin/stdout redirected\n") - 1) < 0)
{
/* Errors ignored. */;
}
}
}
/* Start an inferior process and returns its pid.
PROGRAM is the name of the program to be started, and PROGRAM_ARGS
are its arguments. */
int
linux_process_target::create_inferior (const char *program,
const std::vector<char *> &program_args)
{
client_state &cs = get_client_state ();
struct lwp_info *new_lwp;
int pid;
ptid_t ptid;
{
maybe_disable_address_space_randomization restore_personality
(cs.disable_randomization);
std::string str_program_args = construct_inferior_arguments (program_args);
pid = fork_inferior (program,
str_program_args.c_str (),
get_environ ()->envp (), linux_ptrace_fun,
NULL, NULL, NULL, NULL);
}
add_linux_process (pid, 0);
ptid = ptid_t (pid, pid);
new_lwp = add_lwp (ptid);
new_lwp->must_set_ptrace_flags = 1;
post_fork_inferior (pid, program);
return pid;
}
/* Implement the post_create_inferior target_ops method. */
void
linux_process_target::post_create_inferior ()
{
struct lwp_info *lwp = get_thread_lwp (current_thread);
low_arch_setup ();
if (lwp->must_set_ptrace_flags)
{
struct process_info *proc = current_process ();
int options = linux_low_ptrace_options (proc->attached);
linux_enable_event_reporting (lwpid_of (current_thread), options);
lwp->must_set_ptrace_flags = 0;
}
}
int
linux_process_target::attach_lwp (ptid_t ptid)
{
struct lwp_info *new_lwp;
int lwpid = ptid.lwp ();
if (ptrace (PTRACE_ATTACH, lwpid, (PTRACE_TYPE_ARG3) 0, (PTRACE_TYPE_ARG4) 0)
!= 0)
return errno;
new_lwp = add_lwp (ptid);
/* We need to wait for SIGSTOP before being able to make the next
ptrace call on this LWP. */
new_lwp->must_set_ptrace_flags = 1;
if (linux_proc_pid_is_stopped (lwpid))
{
if (debug_threads)
debug_printf ("Attached to a stopped process\n");
/* The process is definitely stopped. It is in a job control
stop, unless the kernel predates the TASK_STOPPED /
TASK_TRACED distinction, in which case it might be in a
ptrace stop. Make sure it is in a ptrace stop; from there we
can kill it, signal it, et cetera.
First make sure there is a pending SIGSTOP. Since we are
already attached, the process can not transition from stopped
to running without a PTRACE_CONT; so we know this signal will
go into the queue. The SIGSTOP generated by PTRACE_ATTACH is
probably already in the queue (unless this kernel is old
enough to use TASK_STOPPED for ptrace stops); but since
SIGSTOP is not an RT signal, it can only be queued once. */
kill_lwp (lwpid, SIGSTOP);
/* Finally, resume the stopped process. This will deliver the
SIGSTOP (or a higher priority signal, just like normal
PTRACE_ATTACH), which we'll catch later on. */
ptrace (PTRACE_CONT, lwpid, (PTRACE_TYPE_ARG3) 0, (PTRACE_TYPE_ARG4) 0);
}
/* The next time we wait for this LWP we'll see a SIGSTOP as PTRACE_ATTACH
brings it to a halt.
There are several cases to consider here:
1) gdbserver has already attached to the process and is being notified
of a new thread that is being created.
In this case we should ignore that SIGSTOP and resume the
process. This is handled below by setting stop_expected = 1,
and the fact that add_thread sets last_resume_kind ==
resume_continue.
2) This is the first thread (the process thread), and we're attaching
to it via attach_inferior.
In this case we want the process thread to stop.
This is handled by having linux_attach set last_resume_kind ==
resume_stop after we return.
If the pid we are attaching to is also the tgid, we attach to and
stop all the existing threads. Otherwise, we attach to pid and
ignore any other threads in the same group as this pid.
3) GDB is connecting to gdbserver and is requesting an enumeration of all
existing threads.
In this case we want the thread to stop.
FIXME: This case is currently not properly handled.
We should wait for the SIGSTOP but don't. Things work apparently
because enough time passes between when we ptrace (ATTACH) and when
gdb makes the next ptrace call on the thread.
On the other hand, if we are currently trying to stop all threads, we
should treat the new thread as if we had sent it a SIGSTOP. This works
because we are guaranteed that the add_lwp call above added us to the
end of the list, and so the new thread has not yet reached
wait_for_sigstop (but will). */
new_lwp->stop_expected = 1;
return 0;
}
/* Callback for linux_proc_attach_tgid_threads. Attach to PTID if not
already attached. Returns true if a new LWP is found, false
otherwise. */
static int
attach_proc_task_lwp_callback (ptid_t ptid)
{
/* Is this a new thread? */
if (find_thread_ptid (ptid) == NULL)
{
int lwpid = ptid.lwp ();
int err;
if (debug_threads)
debug_printf ("Found new lwp %d\n", lwpid);
err = the_linux_target->attach_lwp (ptid);
/* Be quiet if we simply raced with the thread exiting. EPERM
is returned if the thread's task still exists, and is marked
as exited or zombie, as well as other conditions, so in that
case, confirm the status in /proc/PID/status. */
if (err == ESRCH
|| (err == EPERM && linux_proc_pid_is_gone (lwpid)))
{
if (debug_threads)
{
debug_printf ("Cannot attach to lwp %d: "
"thread is gone (%d: %s)\n",
lwpid, err, safe_strerror (err));
}
}
else if (err != 0)
{
std::string reason
= linux_ptrace_attach_fail_reason_string (ptid, err);
warning (_("Cannot attach to lwp %d: %s"), lwpid, reason.c_str ());
}
return 1;
}
return 0;
}
static void async_file_mark (void);
/* Attach to PID. If PID is the tgid, attach to it and all
of its threads. */
int
linux_process_target::attach (unsigned long pid)
{
struct process_info *proc;
struct thread_info *initial_thread;
ptid_t ptid = ptid_t (pid, pid);
int err;
proc = add_linux_process (pid, 1);
/* Attach to PID. We will check for other threads
soon. */
err = attach_lwp (ptid);
if (err != 0)
{
remove_process (proc);
std::string reason = linux_ptrace_attach_fail_reason_string (ptid, err);
error ("Cannot attach to process %ld: %s", pid, reason.c_str ());
}
/* Don't ignore the initial SIGSTOP if we just attached to this
process. It will be collected by wait shortly. */
initial_thread = find_thread_ptid (ptid_t (pid, pid));
initial_thread->last_resume_kind = resume_stop;
/* We must attach to every LWP. If /proc is mounted, use that to
find them now. On the one hand, the inferior may be using raw
clone instead of using pthreads. On the other hand, even if it
is using pthreads, GDB may not be connected yet (thread_db needs
to do symbol lookups, through qSymbol). Also, thread_db walks
structures in the inferior's address space to find the list of
threads/LWPs, and those structures may well be corrupted. Note
that once thread_db is loaded, we'll still use it to list threads
and associate pthread info with each LWP. */
linux_proc_attach_tgid_threads (pid, attach_proc_task_lwp_callback);
/* GDB will shortly read the xml target description for this
process, to figure out the process' architecture. But the target
description is only filled in when the first process/thread in
the thread group reports its initial PTRACE_ATTACH SIGSTOP. Do
that now, otherwise, if GDB is fast enough, it could read the
target description _before_ that initial stop. */
if (non_stop)
{
struct lwp_info *lwp;
int wstat, lwpid;
ptid_t pid_ptid = ptid_t (pid);
lwpid = wait_for_event_filtered (pid_ptid, pid_ptid, &wstat, __WALL);
gdb_assert (lwpid > 0);
lwp = find_lwp_pid (ptid_t (lwpid));
if (!WIFSTOPPED (wstat) || WSTOPSIG (wstat) != SIGSTOP)
{
lwp->status_pending_p = 1;
lwp->status_pending = wstat;
}
initial_thread->last_resume_kind = resume_continue;
async_file_mark ();
gdb_assert (proc->tdesc != NULL);
}
return 0;
}
static int
last_thread_of_process_p (int pid)
{
bool seen_one = false;
thread_info *thread = find_thread (pid, [&] (thread_info *thr_arg)
{
if (!seen_one)
{
/* This is the first thread of this process we see. */
seen_one = true;
return false;
}
else
{
/* This is the second thread of this process we see. */
return true;
}
});
return thread == NULL;
}
/* Kill LWP. */
static void
linux_kill_one_lwp (struct lwp_info *lwp)
{
struct thread_info *thr = get_lwp_thread (lwp);
int pid = lwpid_of (thr);
/* PTRACE_KILL is unreliable. After stepping into a signal handler,
there is no signal context, and ptrace(PTRACE_KILL) (or
ptrace(PTRACE_CONT, SIGKILL), pretty much the same) acts like
ptrace(CONT, pid, 0,0) and just resumes the tracee. A better
alternative is to kill with SIGKILL. We only need one SIGKILL
per process, not one for each thread. But since we still support
support debugging programs using raw clone without CLONE_THREAD,
we send one for each thread. For years, we used PTRACE_KILL
only, so we're being a bit paranoid about some old kernels where
PTRACE_KILL might work better (dubious if there are any such, but
that's why it's paranoia), so we try SIGKILL first, PTRACE_KILL
second, and so we're fine everywhere. */
errno = 0;
kill_lwp (pid, SIGKILL);
if (debug_threads)
{
int save_errno = errno;
debug_printf ("LKL: kill_lwp (SIGKILL) %s, 0, 0 (%s)\n",
target_pid_to_str (ptid_of (thr)),
save_errno ? safe_strerror (save_errno) : "OK");
}
errno = 0;
ptrace (PTRACE_KILL, pid, (PTRACE_TYPE_ARG3) 0, (PTRACE_TYPE_ARG4) 0);
if (debug_threads)
{
int save_errno = errno;
debug_printf ("LKL: PTRACE_KILL %s, 0, 0 (%s)\n",
target_pid_to_str (ptid_of (thr)),
save_errno ? safe_strerror (save_errno) : "OK");
}
}
/* Kill LWP and wait for it to die. */
static void
kill_wait_lwp (struct lwp_info *lwp)
{
struct thread_info *thr = get_lwp_thread (lwp);
int pid = ptid_of (thr).pid ();
int lwpid = ptid_of (thr).lwp ();
int wstat;
int res;
if (debug_threads)
debug_printf ("kwl: killing lwp %d, for pid: %d\n", lwpid, pid);
do
{
linux_kill_one_lwp (lwp);
/* Make sure it died. Notes:
- The loop is most likely unnecessary.
- We don't use wait_for_event as that could delete lwps
while we're iterating over them. We're not interested in
any pending status at this point, only in making sure all
wait status on the kernel side are collected until the
process is reaped.
- We don't use __WALL here as the __WALL emulation relies on
SIGCHLD, and killing a stopped process doesn't generate
one, nor an exit status.
*/
res = my_waitpid (lwpid, &wstat, 0);
if (res == -1 && errno == ECHILD)
res = my_waitpid (lwpid, &wstat, __WCLONE);
} while (res > 0 && WIFSTOPPED (wstat));
/* Even if it was stopped, the child may have already disappeared.
E.g., if it was killed by SIGKILL. */
if (res < 0 && errno != ECHILD)
perror_with_name ("kill_wait_lwp");
}
/* Callback for `for_each_thread'. Kills an lwp of a given process,
except the leader. */
static void
kill_one_lwp_callback (thread_info *thread, int pid)
{
struct lwp_info *lwp = get_thread_lwp (thread);
/* We avoid killing the first thread here, because of a Linux kernel (at
least 2.6.0-test7 through 2.6.8-rc4) bug; if we kill the parent before
the children get a chance to be reaped, it will remain a zombie
forever. */
if (lwpid_of (thread) == pid)
{
if (debug_threads)
debug_printf ("lkop: is last of process %s\n",
target_pid_to_str (thread->id));
return;
}
kill_wait_lwp (lwp);
}
int
linux_process_target::kill (process_info *process)
{
int pid = process->pid;
/* If we're killing a running inferior, make sure it is stopped
first, as PTRACE_KILL will not work otherwise. */
stop_all_lwps (0, NULL);
for_each_thread (pid, [&] (thread_info *thread)
{
kill_one_lwp_callback (thread, pid);
});
/* See the comment in linux_kill_one_lwp. We did not kill the first
thread in the list, so do so now. */
lwp_info *lwp = find_lwp_pid (ptid_t (pid));
if (lwp == NULL)
{
if (debug_threads)
debug_printf ("lk_1: cannot find lwp for pid: %d\n",
pid);
}
else
kill_wait_lwp (lwp);
mourn (process);
/* Since we presently can only stop all lwps of all processes, we
need to unstop lwps of other processes. */
unstop_all_lwps (0, NULL);
return 0;
}
/* Get pending signal of THREAD, for detaching purposes. This is the
signal the thread last stopped for, which we need to deliver to the
thread when detaching, otherwise, it'd be suppressed/lost. */
static int
get_detach_signal (struct thread_info *thread)
{
client_state &cs = get_client_state ();
enum gdb_signal signo = GDB_SIGNAL_0;
int status;
struct lwp_info *lp = get_thread_lwp (thread);
if (lp->status_pending_p)
status = lp->status_pending;
else
{
/* If the thread had been suspended by gdbserver, and it stopped
cleanly, then it'll have stopped with SIGSTOP. But we don't
want to deliver that SIGSTOP. */
if (thread->last_status.kind != TARGET_WAITKIND_STOPPED
|| thread->last_status.value.sig == GDB_SIGNAL_0)
return 0;
/* Otherwise, we may need to deliver the signal we
intercepted. */
status = lp->last_status;
}
if (!WIFSTOPPED (status))
{
if (debug_threads)
debug_printf ("GPS: lwp %s hasn't stopped: no pending signal\n",
target_pid_to_str (ptid_of (thread)));
return 0;
}
/* Extended wait statuses aren't real SIGTRAPs. */
if (WSTOPSIG (status) == SIGTRAP && linux_is_extended_waitstatus (status))
{
if (debug_threads)
debug_printf ("GPS: lwp %s had stopped with extended "
"status: no pending signal\n",
target_pid_to_str (ptid_of (thread)));
return 0;
}
signo = gdb_signal_from_host (WSTOPSIG (status));
if (cs.program_signals_p && !cs.program_signals[signo])
{
if (debug_threads)
debug_printf ("GPS: lwp %s had signal %s, but it is in nopass state\n",
target_pid_to_str (ptid_of (thread)),
gdb_signal_to_string (signo));
return 0;
}
else if (!cs.program_signals_p
/* If we have no way to know which signals GDB does not
want to have passed to the program, assume
SIGTRAP/SIGINT, which is GDB's default. */
&& (signo == GDB_SIGNAL_TRAP || signo == GDB_SIGNAL_INT))
{
if (debug_threads)
debug_printf ("GPS: lwp %s had signal %s, "
"but we don't know if we should pass it. "
"Default to not.\n",
target_pid_to_str (ptid_of (thread)),
gdb_signal_to_string (signo));
return 0;
}
else
{
if (debug_threads)
debug_printf ("GPS: lwp %s has pending signal %s: delivering it.\n",
target_pid_to_str (ptid_of (thread)),
gdb_signal_to_string (signo));
return WSTOPSIG (status);
}
}
void
linux_process_target::detach_one_lwp (lwp_info *lwp)
{
struct thread_info *thread = get_lwp_thread (lwp);
int sig;
int lwpid;
/* If there is a pending SIGSTOP, get rid of it. */
if (lwp->stop_expected)
{
if (debug_threads)
debug_printf ("Sending SIGCONT to %s\n",
target_pid_to_str (ptid_of (thread)));
kill_lwp (lwpid_of (thread), SIGCONT);
lwp->stop_expected = 0;
}
/* Pass on any pending signal for this thread. */
sig = get_detach_signal (thread);
/* Preparing to resume may try to write registers, and fail if the
lwp is zombie. If that happens, ignore the error. We'll handle
it below, when detach fails with ESRCH. */
try
{
/* Flush any pending changes to the process's registers. */
regcache_invalidate_thread (thread);
/* Finally, let it resume. */
low_prepare_to_resume (lwp);
}
catch (const gdb_exception_error &ex)
{
if (!check_ptrace_stopped_lwp_gone (lwp))
throw;
}
lwpid = lwpid_of (thread);
if (ptrace (PTRACE_DETACH, lwpid, (PTRACE_TYPE_ARG3) 0,
(PTRACE_TYPE_ARG4) (long) sig) < 0)
{
int save_errno = errno;
/* We know the thread exists, so ESRCH must mean the lwp is
zombie. This can happen if one of the already-detached
threads exits the whole thread group. In that case we're
still attached, and must reap the lwp. */
if (save_errno == ESRCH)
{
int ret, status;
ret = my_waitpid (lwpid, &status, __WALL);
if (ret == -1)
{
warning (_("Couldn't reap LWP %d while detaching: %s"),
lwpid, safe_strerror (errno));
}
else if (!WIFEXITED (status) && !WIFSIGNALED (status))
{
warning (_("Reaping LWP %d while detaching "
"returned unexpected status 0x%x"),
lwpid, status);
}
}
else
{
error (_("Can't detach %s: %s"),
target_pid_to_str (ptid_of (thread)),
safe_strerror (save_errno));
}
}
else if (debug_threads)
{
debug_printf ("PTRACE_DETACH (%s, %s, 0) (OK)\n",
target_pid_to_str (ptid_of (thread)),
strsignal (sig));
}
delete_lwp (lwp);
}
int
linux_process_target::detach (process_info *process)
{
struct lwp_info *main_lwp;
/* As there's a step over already in progress, let it finish first,
otherwise nesting a stabilize_threads operation on top gets real
messy. */
complete_ongoing_step_over ();
/* Stop all threads before detaching. First, ptrace requires that
the thread is stopped to successfully detach. Second, thread_db
may need to uninstall thread event breakpoints from memory, which
only works with a stopped process anyway. */
stop_all_lwps (0, NULL);
#ifdef USE_THREAD_DB
thread_db_detach (process);
#endif
/* Stabilize threads (move out of jump pads). */
target_stabilize_threads ();
/* Detach from the clone lwps first. If the thread group exits just
while we're detaching, we must reap the clone lwps before we're
able to reap the leader. */
for_each_thread (process->pid, [this] (thread_info *thread)
{
/* We don't actually detach from the thread group leader just yet.
If the thread group exits, we must reap the zombie clone lwps
before we're able to reap the leader. */
if (thread->id.pid () == thread->id.lwp ())
return;
lwp_info *lwp = get_thread_lwp (thread);
detach_one_lwp (lwp);
});
main_lwp = find_lwp_pid (ptid_t (process->pid));
detach_one_lwp (main_lwp);
mourn (process);
/* Since we presently can only stop all lwps of all processes, we
need to unstop lwps of other processes. */
unstop_all_lwps (0, NULL);
return 0;
}
/* Remove all LWPs that belong to process PROC from the lwp list. */
void
linux_process_target::mourn (process_info *process)
{
struct process_info_private *priv;
#ifdef USE_THREAD_DB
thread_db_mourn (process);
#endif
for_each_thread (process->pid, [this] (thread_info *thread)
{
delete_lwp (get_thread_lwp (thread));
});
/* Freeing all private data. */
priv = process->priv;
low_delete_process (priv->arch_private);
free (priv);
process->priv = NULL;
remove_process (process);
}
void
linux_process_target::join (int pid)
{
int status, ret;
do {
ret = my_waitpid (pid, &status, 0);
if (WIFEXITED (status) || WIFSIGNALED (status))
break;
} while (ret != -1 || errno != ECHILD);
}
/* Return true if the given thread is still alive. */
bool
linux_process_target::thread_alive (ptid_t ptid)
{
struct lwp_info *lwp = find_lwp_pid (ptid);
/* We assume we always know if a thread exits. If a whole process
exited but we still haven't been able to report it to GDB, we'll
hold on to the last lwp of the dead process. */
if (lwp != NULL)
return !lwp_is_marked_dead (lwp);
else
return 0;
}
bool
linux_process_target::thread_still_has_status_pending (thread_info *thread)
{
struct lwp_info *lp = get_thread_lwp (thread);
if (!lp->status_pending_p)
return 0;
if (thread->last_resume_kind != resume_stop
&& (lp->stop_reason == TARGET_STOPPED_BY_SW_BREAKPOINT
|| lp->stop_reason == TARGET_STOPPED_BY_HW_BREAKPOINT))
{
struct thread_info *saved_thread;
CORE_ADDR pc;
int discard = 0;
gdb_assert (lp->last_status != 0);
pc = get_pc (lp);
saved_thread = current_thread;
current_thread = thread;
if (pc != lp->stop_pc)
{
if (debug_threads)
debug_printf ("PC of %ld changed\n",
lwpid_of (thread));
discard = 1;
}
#if !USE_SIGTRAP_SIGINFO
else if (lp->stop_reason == TARGET_STOPPED_BY_SW_BREAKPOINT
&& !low_breakpoint_at (pc))
{
if (debug_threads)
debug_printf ("previous SW breakpoint of %ld gone\n",
lwpid_of (thread));
discard = 1;
}
else if (lp->stop_reason == TARGET_STOPPED_BY_HW_BREAKPOINT
&& !hardware_breakpoint_inserted_here (pc))
{
if (debug_threads)
debug_printf ("previous HW breakpoint of %ld gone\n",
lwpid_of (thread));
discard = 1;
}
#endif
current_thread = saved_thread;
if (discard)
{
if (debug_threads)
debug_printf ("discarding pending breakpoint status\n");
lp->status_pending_p = 0;
return 0;
}
}
return 1;
}
/* Returns true if LWP is resumed from the client's perspective. */
static int
lwp_resumed (struct lwp_info *lwp)
{
struct thread_info *thread = get_lwp_thread (lwp);
if (thread->last_resume_kind != resume_stop)
return 1;
/* Did gdb send us a `vCont;t', but we haven't reported the
corresponding stop to gdb yet? If so, the thread is still
resumed/running from gdb's perspective. */
if (thread->last_resume_kind == resume_stop
&& thread->last_status.kind == TARGET_WAITKIND_IGNORE)
return 1;
return 0;
}
bool
linux_process_target::status_pending_p_callback (thread_info *thread,
ptid_t ptid)
{
struct lwp_info *lp = get_thread_lwp (thread);
/* Check if we're only interested in events from a specific process
or a specific LWP. */
if (!thread->id.matches (ptid))
return 0;
if (!lwp_resumed (lp))
return 0;
if (lp->status_pending_p
&& !thread_still_has_status_pending (thread))
{
resume_one_lwp (lp, lp->stepping, GDB_SIGNAL_0, NULL);
return 0;
}
return lp->status_pending_p;
}
struct lwp_info *
find_lwp_pid (ptid_t ptid)
{
thread_info *thread = find_thread ([&] (thread_info *thr_arg)
{
int lwp = ptid.lwp () != 0 ? ptid.lwp () : ptid.pid ();
return thr_arg->id.lwp () == lwp;
});
if (thread == NULL)
return NULL;
return get_thread_lwp (thread);
}
/* Return the number of known LWPs in the tgid given by PID. */
static int
num_lwps (int pid)
{
int count = 0;
for_each_thread (pid, [&] (thread_info *thread)
{
count++;
});
return count;
}
/* See nat/linux-nat.h. */
struct lwp_info *
iterate_over_lwps (ptid_t filter,
gdb::function_view<iterate_over_lwps_ftype> callback)
{
thread_info *thread = find_thread (filter, [&] (thread_info *thr_arg)
{
lwp_info *lwp = get_thread_lwp (thr_arg);
return callback (lwp);
});
if (thread == NULL)
return NULL;
return get_thread_lwp (thread);
}
void
linux_process_target::check_zombie_leaders ()
{
for_each_process ([this] (process_info *proc) {
pid_t leader_pid = pid_of (proc);
struct lwp_info *leader_lp;
leader_lp = find_lwp_pid (ptid_t (leader_pid));
if (debug_threads)
debug_printf ("leader_pid=%d, leader_lp!=NULL=%d, "
"num_lwps=%d, zombie=%d\n",
leader_pid, leader_lp!= NULL, num_lwps (leader_pid),
linux_proc_pid_is_zombie (leader_pid));
if (leader_lp != NULL && !leader_lp->stopped
/* Check if there are other threads in the group, as we may
have raced with the inferior simply exiting. */
&& !last_thread_of_process_p (leader_pid)
&& linux_proc_pid_is_zombie (leader_pid))
{
/* A leader zombie can mean one of two things:
- It exited, and there's an exit status pending
available, or only the leader exited (not the whole
program). In the latter case, we can't waitpid the
leader's exit status until all other threads are gone.
- There are 3 or more threads in the group, and a thread
other than the leader exec'd. On an exec, the Linux
kernel destroys all other threads (except the execing
one) in the thread group, and resets the execing thread's
tid to the tgid. No exit notification is sent for the
execing thread -- from the ptracer's perspective, it
appears as though the execing thread just vanishes.
Until we reap all other threads except the leader and the
execing thread, the leader will be zombie, and the
execing thread will be in `D (disc sleep)'. As soon as
all other threads are reaped, the execing thread changes
it's tid to the tgid, and the previous (zombie) leader
vanishes, giving place to the "new" leader. We could try
distinguishing the exit and exec cases, by waiting once
more, and seeing if something comes out, but it doesn't
sound useful. The previous leader _does_ go away, and
we'll re-add the new one once we see the exec event
(which is just the same as what would happen if the
previous leader did exit voluntarily before some other
thread execs). */
if (debug_threads)
debug_printf ("CZL: Thread group leader %d zombie "
"(it exited, or another thread execd).\n",
leader_pid);
delete_lwp (leader_lp);
}
});
}
/* Callback for `find_thread'. Returns the first LWP that is not
stopped. */
static bool
not_stopped_callback (thread_info *thread, ptid_t filter)
{
if (!thread->id.matches (filter))
return false;
lwp_info *lwp = get_thread_lwp (thread);
return !lwp->stopped;
}
/* Increment LWP's suspend count. */
static void
lwp_suspended_inc (struct lwp_info *lwp)
{
lwp->suspended++;
if (debug_threads && lwp->suspended > 4)
{
struct thread_info *thread = get_lwp_thread (lwp);
debug_printf ("LWP %ld has a suspiciously high suspend count,"
" suspended=%d\n", lwpid_of (thread), lwp->suspended);
}
}
/* Decrement LWP's suspend count. */
static void
lwp_suspended_decr (struct lwp_info *lwp)
{
lwp->suspended--;
if (lwp->suspended < 0)
{
struct thread_info *thread = get_lwp_thread (lwp);
internal_error (__FILE__, __LINE__,
"unsuspend LWP %ld, suspended=%d\n", lwpid_of (thread),
lwp->suspended);
}
}
/* This function should only be called if the LWP got a SIGTRAP.
Handle any tracepoint steps or hits. Return true if a tracepoint
event was handled, 0 otherwise. */
static int
handle_tracepoints (struct lwp_info *lwp)
{
struct thread_info *tinfo = get_lwp_thread (lwp);
int tpoint_related_event = 0;
gdb_assert (lwp->suspended == 0);
/* If this tracepoint hit causes a tracing stop, we'll immediately
uninsert tracepoints. To do this, we temporarily pause all
threads, unpatch away, and then unpause threads. We need to make
sure the unpausing doesn't resume LWP too. */
lwp_suspended_inc (lwp);
/* And we need to be sure that any all-threads-stopping doesn't try
to move threads out of the jump pads, as it could deadlock the
inferior (LWP could be in the jump pad, maybe even holding the
lock.) */
/* Do any necessary step collect actions. */
tpoint_related_event |= tracepoint_finished_step (tinfo, lwp->stop_pc);
tpoint_related_event |= handle_tracepoint_bkpts (tinfo, lwp->stop_pc);
/* See if we just hit a tracepoint and do its main collect
actions. */
tpoint_related_event |= tracepoint_was_hit (tinfo, lwp->stop_pc);
lwp_suspended_decr (lwp);
gdb_assert (lwp->suspended == 0);
gdb_assert (!stabilizing_threads
|| (lwp->collecting_fast_tracepoint
!= fast_tpoint_collect_result::not_collecting));
if (tpoint_related_event)
{
if (debug_threads)
debug_printf ("got a tracepoint event\n");
return 1;
}
return 0;
}
fast_tpoint_collect_result
linux_process_target::linux_fast_tracepoint_collecting
(lwp_info *lwp, fast_tpoint_collect_status *status)
{
CORE_ADDR thread_area;
struct thread_info *thread = get_lwp_thread (lwp);
/* Get the thread area address. This is used to recognize which
thread is which when tracing with the in-process agent library.
We don't read anything from the address, and treat it as opaque;
it's the address itself that we assume is unique per-thread. */
if (low_get_thread_area (lwpid_of (thread), &thread_area) == -1)
return fast_tpoint_collect_result::not_collecting;
return fast_tracepoint_collecting (thread_area, lwp->stop_pc, status);
}
int
linux_process_target::low_get_thread_area (int lwpid, CORE_ADDR *addrp)
{
return -1;
}
bool
linux_process_target::maybe_move_out_of_jump_pad (lwp_info *lwp, int *wstat)
{
struct thread_info *saved_thread;
saved_thread = current_thread;
current_thread = get_lwp_thread (lwp);
if ((wstat == NULL
|| (WIFSTOPPED (*wstat) && WSTOPSIG (*wstat) != SIGTRAP))
&& supports_fast_tracepoints ()
&& agent_loaded_p ())
{
struct fast_tpoint_collect_status status;
if (debug_threads)
debug_printf ("Checking whether LWP %ld needs to move out of the "
"jump pad.\n",
lwpid_of (current_thread));
fast_tpoint_collect_result r
= linux_fast_tracepoint_collecting (lwp, &status);
if (wstat == NULL
|| (WSTOPSIG (*wstat) != SIGILL
&& WSTOPSIG (*wstat) != SIGFPE
&& WSTOPSIG (*wstat) != SIGSEGV
&& WSTOPSIG (*wstat) != SIGBUS))
{
lwp->collecting_fast_tracepoint = r;
if (r != fast_tpoint_collect_result::not_collecting)
{
if (r == fast_tpoint_collect_result::before_insn
&& lwp->exit_jump_pad_bkpt == NULL)
{
/* Haven't executed the original instruction yet.
Set breakpoint there, and wait till it's hit,
then single-step until exiting the jump pad. */
lwp->exit_jump_pad_bkpt
= set_breakpoint_at (status.adjusted_insn_addr, NULL);
}
if (debug_threads)
debug_printf ("Checking whether LWP %ld needs to move out of "
"the jump pad...it does\n",
lwpid_of (current_thread));
current_thread = saved_thread;
return true;
}
}
else
{
/* If we get a synchronous signal while collecting, *and*
while executing the (relocated) original instruction,
reset the PC to point at the tpoint address, before
reporting to GDB. Otherwise, it's an IPA lib bug: just
report the signal to GDB, and pray for the best. */
lwp->collecting_fast_tracepoint
= fast_tpoint_collect_result::not_collecting;
if (r != fast_tpoint_collect_result::not_collecting
&& (status.adjusted_insn_addr <= lwp->stop_pc
&& lwp->stop_pc < status.adjusted_insn_addr_end))
{
siginfo_t info;
struct regcache *regcache;
/* The si_addr on a few signals references the address
of the faulting instruction. Adjust that as
well. */
if ((WSTOPSIG (*wstat) == SIGILL
|| WSTOPSIG (*wstat) == SIGFPE
|| WSTOPSIG (*wstat) == SIGBUS
|| WSTOPSIG (*wstat) == SIGSEGV)
&& ptrace (PTRACE_GETSIGINFO, lwpid_of (current_thread),
(PTRACE_TYPE_ARG3) 0, &info) == 0
/* Final check just to make sure we don't clobber
the siginfo of non-kernel-sent signals. */
&& (uintptr_t) info.si_addr == lwp->stop_pc)
{
info.si_addr = (void *) (uintptr_t) status.tpoint_addr;
ptrace (PTRACE_SETSIGINFO, lwpid_of (current_thread),
(PTRACE_TYPE_ARG3) 0, &info);
}
regcache = get_thread_regcache (current_thread, 1);
low_set_pc (regcache, status.tpoint_addr);
lwp->stop_pc = status.tpoint_addr;
/* Cancel any fast tracepoint lock this thread was
holding. */
force_unlock_trace_buffer ();
}
if (lwp->exit_jump_pad_bkpt != NULL)
{
if (debug_threads)
debug_printf ("Cancelling fast exit-jump-pad: removing bkpt. "
"stopping all threads momentarily.\n");
stop_all_lwps (1, lwp);
delete_breakpoint (lwp->exit_jump_pad_bkpt);
lwp->exit_jump_pad_bkpt = NULL;
unstop_all_lwps (1, lwp);
gdb_assert (lwp->suspended >= 0);
}
}
}
if (debug_threads)
debug_printf ("Checking whether LWP %ld needs to move out of the "
"jump pad...no\n",
lwpid_of (current_thread));
current_thread = saved_thread;
return false;
}
/* Enqueue one signal in the "signals to report later when out of the
jump pad" list. */
static void
enqueue_one_deferred_signal (struct lwp_info *lwp, int *wstat)
{
struct thread_info *thread = get_lwp_thread (lwp);
if (debug_threads)
debug_printf ("Deferring signal %d for LWP %ld.\n",
WSTOPSIG (*wstat), lwpid_of (thread));
if (debug_threads)
{
for (const auto &sig : lwp->pending_signals_to_report)
debug_printf (" Already queued %d\n",
sig.signal);
debug_printf (" (no more currently queued signals)\n");
}
/* Don't enqueue non-RT signals if they are already in the deferred
queue. (SIGSTOP being the easiest signal to see ending up here
twice) */
if (WSTOPSIG (*wstat) < __SIGRTMIN)
{
for (const auto &sig : lwp->pending_signals_to_report)
{
if (sig.signal == WSTOPSIG (*wstat))
{
if (debug_threads)
debug_printf ("Not requeuing already queued non-RT signal %d"
" for LWP %ld\n",
sig.signal,
lwpid_of (thread));
return;
}
}
}
lwp->pending_signals_to_report.emplace_back (WSTOPSIG (*wstat));
ptrace (PTRACE_GETSIGINFO, lwpid_of (thread), (PTRACE_TYPE_ARG3) 0,
&lwp->pending_signals_to_report.back ().info);
}
/* Dequeue one signal from the "signals to report later when out of
the jump pad" list. */
static int
dequeue_one_deferred_signal (struct lwp_info *lwp, int *wstat)
{
struct thread_info *thread = get_lwp_thread (lwp);
if (!lwp->pending_signals_to_report.empty ())
{
const pending_signal &p_sig = lwp->pending_signals_to_report.front ();
*wstat = W_STOPCODE (p_sig.signal);
if (p_sig.info.si_signo != 0)
ptrace (PTRACE_SETSIGINFO, lwpid_of (thread), (PTRACE_TYPE_ARG3) 0,
&p_sig.info);
lwp->pending_signals_to_report.pop_front ();
if (debug_threads)
debug_printf ("Reporting deferred signal %d for LWP %ld.\n",
WSTOPSIG (*wstat), lwpid_of (thread));
if (debug_threads)
{
for (const auto &sig : lwp->pending_signals_to_report)
debug_printf (" Still queued %d\n",
sig.signal);
debug_printf (" (no more queued signals)\n");
}
return 1;
}
return 0;
}
bool
linux_process_target::check_stopped_by_watchpoint (lwp_info *child)
{
struct thread_info *saved_thread = current_thread;
current_thread = get_lwp_thread (child);
if (low_stopped_by_watchpoint ())
{
child->stop_reason = TARGET_STOPPED_BY_WATCHPOINT;
child->stopped_data_address = low_stopped_data_address ();
}
current_thread = saved_thread;
return child->stop_reason == TARGET_STOPPED_BY_WATCHPOINT;
}
bool
linux_process_target::low_stopped_by_watchpoint ()
{
return false;
}
CORE_ADDR
linux_process_target::low_stopped_data_address ()
{
return 0;
}
/* Return the ptrace options that we want to try to enable. */
static int
linux_low_ptrace_options (int attached)
{
client_state &cs = get_client_state ();
int options = 0;
if (!attached)
options |= PTRACE_O_EXITKILL;
if (cs.report_fork_events)
options |= PTRACE_O_TRACEFORK;
if (cs.report_vfork_events)
options |= (PTRACE_O_TRACEVFORK | PTRACE_O_TRACEVFORKDONE);
if (cs.report_exec_events)
options |= PTRACE_O_TRACEEXEC;
options |= PTRACE_O_TRACESYSGOOD;
return options;
}
void
linux_process_target::filter_event (int lwpid, int wstat)
{
client_state &cs = get_client_state ();
struct lwp_info *child;
struct thread_info *thread;
int have_stop_pc = 0;
child = find_lwp_pid (ptid_t (lwpid));
/* Check for stop events reported by a process we didn't already
know about - anything not already in our LWP list.
If we're expecting to receive stopped processes after
fork, vfork, and clone events, then we'll just add the
new one to our list and go back to waiting for the event
to be reported - the stopped process might be returned
from waitpid before or after the event is.
But note the case of a non-leader thread exec'ing after the
leader having exited, and gone from our lists (because
check_zombie_leaders deleted it). The non-leader thread
changes its tid to the tgid. */
if (WIFSTOPPED (wstat) && child == NULL && WSTOPSIG (wstat) == SIGTRAP
&& linux_ptrace_get_extended_event (wstat) == PTRACE_EVENT_EXEC)
{
ptid_t child_ptid;
/* A multi-thread exec after we had seen the leader exiting. */
if (debug_threads)
{
debug_printf ("LLW: Re-adding thread group leader LWP %d"
"after exec.\n", lwpid);
}
child_ptid = ptid_t (lwpid, lwpid);
child = add_lwp (child_ptid);
child->stopped = 1;
current_thread = child->thread;
}
/* If we didn't find a process, one of two things presumably happened:
- A process we started and then detached from has exited. Ignore it.
- A process we are controlling has forked and the new child's stop
was reported to us by the kernel. Save its PID. */
if (child == NULL && WIFSTOPPED (wstat))
{
add_to_pid_list (&stopped_pids, lwpid, wstat);
return;
}
else if (child == NULL)
return;
thread = get_lwp_thread (child);
child->stopped = 1;
child->last_status = wstat;
/* Check if the thread has exited. */
if ((WIFEXITED (wstat) || WIFSIGNALED (wstat)))
{
if (debug_threads)
debug_printf ("LLFE: %d exited.\n", lwpid);
if (finish_step_over (child))
{
/* Unsuspend all other LWPs, and set them back running again. */
unsuspend_all_lwps (child);
}
/* If there is at least one more LWP, then the exit signal was
not the end of the debugged application and should be
ignored, unless GDB wants to hear about thread exits. */
if (cs.report_thread_events
|| last_thread_of_process_p (pid_of (thread)))
{
/* Since events are serialized to GDB core, and we can't
report this one right now. Leave the status pending for
the next time we're able to report it. */
mark_lwp_dead (child, wstat);
return;
}
else
{
delete_lwp (child);
return;
}
}
gdb_assert (WIFSTOPPED (wstat));
if (WIFSTOPPED (wstat))
{
struct process_info *proc;
/* Architecture-specific setup after inferior is running. */
proc = find_process_pid (pid_of (thread));
if (proc->tdesc == NULL)
{
if (proc->attached)
{
/* This needs to happen after we have attached to the
inferior and it is stopped for the first time, but
before we access any inferior registers. */
arch_setup_thread (thread);
}
else
{
/* The process is started, but GDBserver will do
architecture-specific setup after the program stops at
the first instruction. */
child->status_pending_p = 1;
child->status_pending = wstat;
return;
}
}
}
if (WIFSTOPPED (wstat) && child->must_set_ptrace_flags)
{
struct process_info *proc = find_process_pid (pid_of (thread));
int options = linux_low_ptrace_options (proc->attached);
linux_enable_event_reporting (lwpid, options);
child->must_set_ptrace_flags = 0;
}
/* Always update syscall_state, even if it will be filtered later. */
if (WIFSTOPPED (wstat) && WSTOPSIG (wstat) == SYSCALL_SIGTRAP)
{
child->syscall_state
= (child->syscall_state == TARGET_WAITKIND_SYSCALL_ENTRY
? TARGET_WAITKIND_SYSCALL_RETURN
: TARGET_WAITKIND_SYSCALL_ENTRY);
}
else
{
/* Almost all other ptrace-stops are known to be outside of system
calls, with further exceptions in handle_extended_wait. */
child->syscall_state = TARGET_WAITKIND_IGNORE;
}
/* Be careful to not overwrite stop_pc until save_stop_reason is
called. */
if (WIFSTOPPED (wstat) && WSTOPSIG (wstat) == SIGTRAP
&& linux_is_extended_waitstatus (wstat))
{
child->stop_pc = get_pc (child);
if (handle_extended_wait (&child, wstat))
{
/* The event has been handled, so just return without
reporting it. */
return;
}
}
if (linux_wstatus_maybe_breakpoint (wstat))
{
if (save_stop_reason (child))
have_stop_pc = 1;
}
if (!have_stop_pc)
child->stop_pc = get_pc (child);
if (WIFSTOPPED (wstat) && WSTOPSIG (wstat) == SIGSTOP
&& child->stop_expected)
{
if (debug_threads)
debug_printf ("Expected stop.\n");
child->stop_expected = 0;
if (thread->last_resume_kind == resume_stop)
{
/* We want to report the stop to the core. Treat the
SIGSTOP as a normal event. */
if (debug_threads)
debug_printf ("LLW: resume_stop SIGSTOP caught for %s.\n",
target_pid_to_str (ptid_of (thread)));
}
else if (stopping_threads != NOT_STOPPING_THREADS)
{
/* Stopping threads. We don't want this SIGSTOP to end up
pending. */
if (debug_threads)
debug_printf ("LLW: SIGSTOP caught for %s "
"while stopping threads.\n",
target_pid_to_str (ptid_of (thread)));
return;
}
else
{
/* This is a delayed SIGSTOP. Filter out the event. */
if (debug_threads)
debug_printf ("LLW: %s %s, 0, 0 (discard delayed SIGSTOP)\n",
child->stepping ? "step" : "continue",
target_pid_to_str (ptid_of (thread)));
resume_one_lwp (child, child->stepping, 0, NULL);
return;
}
}
child->status_pending_p = 1;
child->status_pending = wstat;
return;
}
bool
linux_process_target::maybe_hw_step (thread_info *thread)
{
if (supports_hardware_single_step ())
return true;
else
{
/* GDBserver must insert single-step breakpoint for software
single step. */
gdb_assert (has_single_step_breakpoints (thread));
return false;
}
}
void
linux_process_target::resume_stopped_resumed_lwps (thread_info *thread)
{
struct lwp_info *lp = get_thread_lwp (thread);
if (lp->stopped
&& !lp->suspended
&& !lp->status_pending_p
&& thread->last_status.kind == TARGET_WAITKIND_IGNORE)
{
int step = 0;
if (thread->last_resume_kind == resume_step)
step = maybe_hw_step (thread);
if (debug_threads)
debug_printf ("RSRL: resuming stopped-resumed LWP %s at %s: step=%d\n",
target_pid_to_str (ptid_of (thread)),
paddress (lp->stop_pc),
step);
resume_one_lwp (lp, step, GDB_SIGNAL_0, NULL);
}
}
int
linux_process_target::wait_for_event_filtered (ptid_t wait_ptid,
ptid_t filter_ptid,
int *wstatp, int options)
{
struct thread_info *event_thread;
struct lwp_info *event_child, *requested_child;
sigset_t block_mask, prev_mask;
retry:
/* N.B. event_thread points to the thread_info struct that contains
event_child. Keep them in sync. */
event_thread = NULL;
event_child = NULL;
requested_child = NULL;
/* Check for a lwp with a pending status. */
if (filter_ptid == minus_one_ptid || filter_ptid.is_pid ())
{
event_thread = find_thread_in_random ([&] (thread_info *thread)
{
return status_pending_p_callback (thread, filter_ptid);
});
if (event_thread != NULL)
event_child = get_thread_lwp (event_thread);
if (debug_threads && event_thread)
debug_printf ("Got a pending child %ld\n", lwpid_of (event_thread));
}
else if (filter_ptid != null_ptid)
{
requested_child = find_lwp_pid (filter_ptid);
if (stopping_threads == NOT_STOPPING_THREADS
&& requested_child->status_pending_p
&& (requested_child->collecting_fast_tracepoint
!= fast_tpoint_collect_result::not_collecting))
{
enqueue_one_deferred_signal (requested_child,
&requested_child->status_pending);
requested_child->status_pending_p = 0;
requested_child->status_pending = 0;
resume_one_lwp (requested_child, 0, 0, NULL);
}
if (requested_child->suspended
&& requested_child->status_pending_p)
{
internal_error (__FILE__, __LINE__,
"requesting an event out of a"
" suspended child?");
}
if (requested_child->status_pending_p)
{
event_child = requested_child;
event_thread = get_lwp_thread (event_child);
}
}
if (event_child != NULL)
{
if (debug_threads)
debug_printf ("Got an event from pending child %ld (%04x)\n",
lwpid_of (event_thread), event_child->status_pending);
*wstatp = event_child->status_pending;
event_child->status_pending_p = 0;
event_child->status_pending = 0;
current_thread = event_thread;
return lwpid_of (event_thread);
}
/* But if we don't find a pending event, we'll have to wait.
We only enter this loop if no process has a pending wait status.
Thus any action taken in response to a wait status inside this
loop is responding as soon as we detect the status, not after any
pending events. */
/* Make sure SIGCHLD is blocked until the sigsuspend below. Block
all signals while here. */
sigfillset (&block_mask);
gdb_sigmask (SIG_BLOCK, &block_mask, &prev_mask);
/* Always pull all events out of the kernel. We'll randomly select
an event LWP out of all that have events, to prevent
starvation. */
while (event_child == NULL)
{
pid_t ret = 0;
/* Always use -1 and WNOHANG, due to couple of a kernel/ptrace
quirks:
- If the thread group leader exits while other threads in the
thread group still exist, waitpid(TGID, ...) hangs. That
waitpid won't return an exit status until the other threads
in the group are reaped.
- When a non-leader thread execs, that thread just vanishes
without reporting an exit (so we'd hang if we waited for it
explicitly in that case). The exec event is reported to
the TGID pid. */
errno = 0;
ret = my_waitpid (-1, wstatp, options | WNOHANG);
if (debug_threads)
debug_printf ("LWFE: waitpid(-1, ...) returned %d, %s\n",
ret, errno ? safe_strerror (errno) : "ERRNO-OK");
if (ret > 0)
{
if (debug_threads)
{
debug_printf ("LLW: waitpid %ld received %s\n",
(long) ret, status_to_str (*wstatp).c_str ());
}
/* Filter all events. IOW, leave all events pending. We'll
randomly select an event LWP out of all that have events
below. */
filter_event (ret, *wstatp);
/* Retry until nothing comes out of waitpid. A single
SIGCHLD can indicate more than one child stopped. */
continue;
}
/* Now that we've pulled all events out of the kernel, resume
LWPs that don't have an interesting event to report. */
if (stopping_threads == NOT_STOPPING_THREADS)
for_each_thread ([this] (thread_info *thread)
{
resume_stopped_resumed_lwps (thread);
});
/* ... and find an LWP with a status to report to the core, if
any. */
event_thread = find_thread_in_random ([&] (thread_info *thread)
{
return status_pending_p_callback (thread, filter_ptid);
});
if (event_thread != NULL)
{
event_child = get_thread_lwp (event_thread);
*wstatp = event_child->status_pending;
event_child->status_pending_p = 0;
event_child->status_pending = 0;
break;
}
/* Check for zombie thread group leaders. Those can't be reaped
until all other threads in the thread group are. */
check_zombie_leaders ();
auto not_stopped = [&] (thread_info *thread)
{
return not_stopped_callback (thread, wait_ptid);
};
/* If there are no resumed children left in the set of LWPs we
want to wait for, bail. We can't just block in
waitpid/sigsuspend, because lwps might have been left stopped
in trace-stop state, and we'd be stuck forever waiting for
their status to change (which would only happen if we resumed
them). Even if WNOHANG is set, this return code is preferred
over 0 (below), as it is more detailed. */
if (find_thread (not_stopped) == NULL)
{
if (debug_threads)
debug_printf ("LLW: exit (no unwaited-for LWP)\n");
gdb_sigmask (SIG_SETMASK, &prev_mask, NULL);
return -1;
}
/* No interesting event to report to the caller. */
if ((options & WNOHANG))
{
if (debug_threads)
debug_printf ("WNOHANG set, no event found\n");
gdb_sigmask (SIG_SETMASK, &prev_mask, NULL);
return 0;
}
/* Block until we get an event reported with SIGCHLD. */
if (debug_threads)
debug_printf ("sigsuspend'ing\n");
sigsuspend (&prev_mask);
gdb_sigmask (SIG_SETMASK, &prev_mask, NULL);
goto retry;
}
gdb_sigmask (SIG_SETMASK, &prev_mask, NULL);
current_thread = event_thread;
return lwpid_of (event_thread);
}
int
linux_process_target::wait_for_event (ptid_t ptid, int *wstatp, int options)
{
return wait_for_event_filtered (ptid, ptid, wstatp, options);
}
/* Select one LWP out of those that have events pending. */
static void
select_event_lwp (struct lwp_info **orig_lp)
{
struct thread_info *event_thread = NULL;
/* In all-stop, give preference to the LWP that is being
single-stepped. There will be at most one, and it's the LWP that
the core is most interested in. If we didn't do this, then we'd
have to handle pending step SIGTRAPs somehow in case the core
later continues the previously-stepped thread, otherwise we'd
report the pending SIGTRAP, and the core, not having stepped the
thread, wouldn't understand what the trap was for, and therefore
would report it to the user as a random signal. */
if (!non_stop)
{
event_thread = find_thread ([] (thread_info *thread)
{
lwp_info *lp = get_thread_lwp (thread);
return (thread->last_status.kind == TARGET_WAITKIND_IGNORE
&& thread->last_resume_kind == resume_step
&& lp->status_pending_p);
});
if (event_thread != NULL)
{
if (debug_threads)
debug_printf ("SEL: Select single-step %s\n",
target_pid_to_str (ptid_of (event_thread)));
}
}
if (event_thread == NULL)
{
/* No single-stepping LWP. Select one at random, out of those
which have had events. */
event_thread = find_thread_in_random ([&] (thread_info *thread)
{
lwp_info *lp = get_thread_lwp (thread);
/* Only resumed LWPs that have an event pending. */
return (thread->last_status.kind == TARGET_WAITKIND_IGNORE
&& lp->status_pending_p);
});
}
if (event_thread != NULL)
{
struct lwp_info *event_lp = get_thread_lwp (event_thread);
/* Switch the event LWP. */
*orig_lp = event_lp;
}
}
/* Decrement the suspend count of all LWPs, except EXCEPT, if non
NULL. */
static void
unsuspend_all_lwps (struct lwp_info *except)
{
for_each_thread ([&] (thread_info *thread)
{
lwp_info *lwp = get_thread_lwp (thread);
if (lwp != except)
lwp_suspended_decr (lwp);
});
}
static bool lwp_running (thread_info *thread);
/* Stabilize threads (move out of jump pads).
If a thread is midway collecting a fast tracepoint, we need to
finish the collection and move it out of the jump pad before
reporting the signal.
This avoids recursion while collecting (when a signal arrives
midway, and the signal handler itself collects), which would trash
the trace buffer. In case the user set a breakpoint in a signal
handler, this avoids the backtrace showing the jump pad, etc..
Most importantly, there are certain things we can't do safely if
threads are stopped in a jump pad (or in its callee's). For
example:
- starting a new trace run. A thread still collecting the
previous run, could trash the trace buffer when resumed. The trace
buffer control structures would have been reset but the thread had
no way to tell. The thread could even midway memcpy'ing to the
buffer, which would mean that when resumed, it would clobber the
trace buffer that had been set for a new run.
- we can't rewrite/reuse the jump pads for new tracepoints
safely. Say you do tstart while a thread is stopped midway while
collecting. When the thread is later resumed, it finishes the
collection, and returns to the jump pad, to execute the original
instruction that was under the tracepoint jump at the time the
older run had been started. If the jump pad had been rewritten
since for something else in the new run, the thread would now
execute the wrong / random instructions. */
void
linux_process_target::stabilize_threads ()
{
thread_info *thread_stuck = find_thread ([this] (thread_info *thread)
{
return stuck_in_jump_pad (thread);
});
if (thread_stuck != NULL)
{
if (debug_threads)
debug_printf ("can't stabilize, LWP %ld is stuck in jump pad\n",
lwpid_of (thread_stuck));
return;
}
thread_info *saved_thread = current_thread;
stabilizing_threads = 1;
/* Kick 'em all. */
for_each_thread ([this] (thread_info *thread)
{
move_out_of_jump_pad (thread);
});
/* Loop until all are stopped out of the jump pads. */
while (find_thread (lwp_running) != NULL)
{
struct target_waitstatus ourstatus;
struct lwp_info *lwp;
int wstat;
/* Note that we go through the full wait even loop. While
moving threads out of jump pad, we need to be able to step
over internal breakpoints and such. */
wait_1 (minus_one_ptid, &ourstatus, 0);
if (ourstatus.kind == TARGET_WAITKIND_STOPPED)
{
lwp = get_thread_lwp (current_thread);
/* Lock it. */
lwp_suspended_inc (lwp);
if (ourstatus.value.sig != GDB_SIGNAL_0
|| current_thread->last_resume_kind == resume_stop)
{
wstat = W_STOPCODE (gdb_signal_to_host (ourstatus.value.sig));
enqueue_one_deferred_signal (lwp, &wstat);
}
}
}
unsuspend_all_lwps (NULL);
stabilizing_threads = 0;
current_thread = saved_thread;
if (debug_threads)
{
thread_stuck = find_thread ([this] (thread_info *thread)
{
return stuck_in_jump_pad (thread);
});
if (thread_stuck != NULL)
debug_printf ("couldn't stabilize, LWP %ld got stuck in jump pad\n",
lwpid_of (thread_stuck));
}
}
/* Convenience function that is called when the kernel reports an
event that is not passed out to GDB. */
static ptid_t
ignore_event (struct target_waitstatus *ourstatus)
{
/* If we got an event, there may still be others, as a single
SIGCHLD can indicate more than one child stopped. This forces
another target_wait call. */
async_file_mark ();
ourstatus->kind = TARGET_WAITKIND_IGNORE;
return null_ptid;
}
ptid_t
linux_process_target::filter_exit_event (lwp_info *event_child,
target_waitstatus *ourstatus)
{
client_state &cs = get_client_state ();
struct thread_info *thread = get_lwp_thread (event_child);
ptid_t ptid = ptid_of (thread);
if (!last_thread_of_process_p (pid_of (thread)))
{
if (cs.report_thread_events)
ourstatus->kind = TARGET_WAITKIND_THREAD_EXITED;
else
ourstatus->kind = TARGET_WAITKIND_IGNORE;
delete_lwp (event_child);
}
return ptid;
}
/* Returns 1 if GDB is interested in any event_child syscalls. */
static int
gdb_catching_syscalls_p (struct lwp_info *event_child)
{
struct thread_info *thread = get_lwp_thread (event_child);
struct process_info *proc = get_thread_process (thread);
return !proc->syscalls_to_catch.empty ();
}
bool
linux_process_target::gdb_catch_this_syscall (lwp_info *event_child)
{
int sysno;
struct thread_info *thread = get_lwp_thread (event_child);
struct process_info *proc = get_thread_process (thread);
if (proc->syscalls_to_catch.empty ())
return false;
if (proc->syscalls_to_catch[0] == ANY_SYSCALL)
return true;
get_syscall_trapinfo (event_child, &sysno);
for (int iter : proc->syscalls_to_catch)
if (iter == sysno)
return true;
return false;
}
ptid_t
linux_process_target::wait_1 (ptid_t ptid, target_waitstatus *ourstatus,
target_wait_flags target_options)
{
client_state &cs = get_client_state ();
int w;
struct lwp_info *event_child;
int options;
int pid;
int step_over_finished;
int bp_explains_trap;
int maybe_internal_trap;
int report_to_gdb;
int trace_event;
int in_step_range;
int any_resumed;
if (debug_threads)
{
debug_enter ();
debug_printf ("wait_1: [%s]\n", target_pid_to_str (ptid));
}
/* Translate generic target options into linux options. */
options = __WALL;
if (target_options & TARGET_WNOHANG)
options |= WNOHANG;
bp_explains_trap = 0;
trace_event = 0;
in_step_range = 0;
ourstatus->kind = TARGET_WAITKIND_IGNORE;
auto status_pending_p_any = [&] (thread_info *thread)
{
return status_pending_p_callback (thread, minus_one_ptid);
};
auto not_stopped = [&] (thread_info *thread)
{
return not_stopped_callback (thread, minus_one_ptid);
};
/* Find a resumed LWP, if any. */
if (find_thread (status_pending_p_any) != NULL)
any_resumed = 1;
else if (find_thread (not_stopped) != NULL)
any_resumed = 1;
else
any_resumed = 0;
if (step_over_bkpt == null_ptid)
pid = wait_for_event (ptid, &w, options);
else
{
if (debug_threads)
debug_printf ("step_over_bkpt set [%s], doing a blocking wait\n",
target_pid_to_str (step_over_bkpt));
pid = wait_for_event (step_over_bkpt, &w, options & ~WNOHANG);
}
if (pid == 0 || (pid == -1 && !any_resumed))
{
gdb_assert (target_options & TARGET_WNOHANG);
if (debug_threads)
{
debug_printf ("wait_1 ret = null_ptid, "
"TARGET_WAITKIND_IGNORE\n");
debug_exit ();
}
ourstatus->kind = TARGET_WAITKIND_IGNORE;
return null_ptid;
}
else if (pid == -1)
{
if (debug_threads)
{
debug_printf ("wait_1 ret = null_ptid, "
"TARGET_WAITKIND_NO_RESUMED\n");
debug_exit ();
}
ourstatus->kind = TARGET_WAITKIND_NO_RESUMED;
return null_ptid;
}
event_child = get_thread_lwp (current_thread);
/* wait_for_event only returns an exit status for the last
child of a process. Report it. */
if (WIFEXITED (w) || WIFSIGNALED (w))
{
if (WIFEXITED (w))
{
ourstatus->kind = TARGET_WAITKIND_EXITED;
ourstatus->value.integer = WEXITSTATUS (w);
if (debug_threads)
{
debug_printf ("wait_1 ret = %s, exited with "
"retcode %d\n",
target_pid_to_str (ptid_of (current_thread)),
WEXITSTATUS (w));
debug_exit ();
}
}
else
{
ourstatus->kind = TARGET_WAITKIND_SIGNALLED;
ourstatus->value.sig = gdb_signal_from_host (WTERMSIG (w));
if (debug_threads)
{
debug_printf ("wait_1 ret = %s, terminated with "
"signal %d\n",
target_pid_to_str (ptid_of (current_thread)),
WTERMSIG (w));
debug_exit ();
}
}
if (ourstatus->kind == TARGET_WAITKIND_EXITED)
return filter_exit_event (event_child, ourstatus);
return ptid_of (current_thread);
}
/* If step-over executes a breakpoint instruction, in the case of a
hardware single step it means a gdb/gdbserver breakpoint had been
planted on top of a permanent breakpoint, in the case of a software
single step it may just mean that gdbserver hit the reinsert breakpoint.
The PC has been adjusted by save_stop_reason to point at
the breakpoint address.
So in the case of the hardware single step advance the PC manually
past the breakpoint and in the case of software single step advance only
if it's not the single_step_breakpoint we are hitting.
This avoids that a program would keep trapping a permanent breakpoint
forever. */
if (step_over_bkpt != null_ptid
&& event_child->stop_reason == TARGET_STOPPED_BY_SW_BREAKPOINT
&& (event_child->stepping
|| !single_step_breakpoint_inserted_here (event_child->stop_pc)))
{
int increment_pc = 0;
int breakpoint_kind = 0;
CORE_ADDR stop_pc = event_child->stop_pc;
breakpoint_kind = breakpoint_kind_from_current_state (&stop_pc);
sw_breakpoint_from_kind (breakpoint_kind, &increment_pc);
if (debug_threads)
{
debug_printf ("step-over for %s executed software breakpoint\n",
target_pid_to_str (ptid_of (current_thread)));
}
if (increment_pc != 0)
{
struct regcache *regcache
= get_thread_regcache (current_thread, 1);
event_child->stop_pc += increment_pc;
low_set_pc (regcache, event_child->stop_pc);
if (!low_breakpoint_at (event_child->stop_pc))
event_child->stop_reason = TARGET_STOPPED_BY_NO_REASON;
}
}
/* If this event was not handled before, and is not a SIGTRAP, we
report it. SIGILL and SIGSEGV are also treated as traps in case
a breakpoint is inserted at the current PC. If this target does
not support internal breakpoints at all, we also report the
SIGTRAP without further processing; it's of no concern to us. */
maybe_internal_trap
= (low_supports_breakpoints ()
&& (WSTOPSIG (w) == SIGTRAP
|| ((WSTOPSIG (w) == SIGILL
|| WSTOPSIG (w) == SIGSEGV)
&& low_breakpoint_at (event_child->stop_pc))));
if (maybe_internal_trap)
{
/* Handle anything that requires bookkeeping before deciding to
report the event or continue waiting. */
/* First check if we can explain the SIGTRAP with an internal
breakpoint, or if we should possibly report the event to GDB.
Do this before anything that may remove or insert a
breakpoint. */
bp_explains_trap = breakpoint_inserted_here (event_child->stop_pc);
/* We have a SIGTRAP, possibly a step-over dance has just
finished. If so, tweak the state machine accordingly,
reinsert breakpoints and delete any single-step
breakpoints. */
step_over_finished = finish_step_over (event_child);
/* Now invoke the callbacks of any internal breakpoints there. */
check_breakpoints (event_child->stop_pc);
/* Handle tracepoint data collecting. This may overflow the
trace buffer, and cause a tracing stop, removing
breakpoints. */
trace_event = handle_tracepoints (event_child);
if (bp_explains_trap)
{
if (debug_threads)
debug_printf ("Hit a gdbserver breakpoint.\n");
}
}
else
{
/* We have some other signal, possibly a step-over dance was in
progress, and it should be cancelled too. */
step_over_finished = finish_step_over (event_child);
}
/* We have all the data we need. Either report the event to GDB, or
resume threads and keep waiting for more. */
/* If we're collecting a fast tracepoint, finish the collection and
move out of the jump pad before delivering a signal. See
linux_stabilize_threads. */
if (WIFSTOPPED (w)
&& WSTOPSIG (w) != SIGTRAP
&& supports_fast_tracepoints ()
&& agent_loaded_p ())
{
if (debug_threads)
debug_printf ("Got signal %d for LWP %ld. Check if we need "
"to defer or adjust it.\n",
WSTOPSIG (w), lwpid_of (current_thread));
/* Allow debugging the jump pad itself. */
if (current_thread->last_resume_kind != resume_step
&& maybe_move_out_of_jump_pad (event_child, &w))
{
enqueue_one_deferred_signal (event_child, &w);
if (debug_threads)
debug_printf ("Signal %d for LWP %ld deferred (in jump pad)\n",
WSTOPSIG (w), lwpid_of (current_thread));
resume_one_lwp (event_child, 0, 0, NULL);
if (debug_threads)
debug_exit ();
return ignore_event (ourstatus);
}
}
if (event_child->collecting_fast_tracepoint
!= fast_tpoint_collect_result::not_collecting)
{
if (debug_threads)
debug_printf ("LWP %ld was trying to move out of the jump pad (%d). "
"Check if we're already there.\n",
lwpid_of (current_thread),
(int) event_child->collecting_fast_tracepoint);
trace_event = 1;
event_child->collecting_fast_tracepoint
= linux_fast_tracepoint_collecting (event_child, NULL);
if (event_child->collecting_fast_tracepoint
!= fast_tpoint_collect_result::before_insn)
{
/* No longer need this breakpoint. */
if (event_child->exit_jump_pad_bkpt != NULL)
{
if (debug_threads)
debug_printf ("No longer need exit-jump-pad bkpt; removing it."
"stopping all threads momentarily.\n");
/* Other running threads could hit this breakpoint.
We don't handle moribund locations like GDB does,
instead we always pause all threads when removing
breakpoints, so that any step-over or
decr_pc_after_break adjustment is always taken
care of while the breakpoint is still
inserted. */
stop_all_lwps (1, event_child);
delete_breakpoint (event_child->exit_jump_pad_bkpt);
event_child->exit_jump_pad_bkpt = NULL;
unstop_all_lwps (1, event_child);
gdb_assert (event_child->suspended >= 0);
}
}
if (event_child->collecting_fast_tracepoint
== fast_tpoint_collect_result::not_collecting)
{
if (debug_threads)
debug_printf ("fast tracepoint finished "
"collecting successfully.\n");
/* We may have a deferred signal to report. */
if (dequeue_one_deferred_signal (event_child, &w))
{
if (debug_threads)
debug_printf ("dequeued one signal.\n");
}
else
{
if (debug_threads)
debug_printf ("no deferred signals.\n");
if (stabilizing_threads)
{
ourstatus->kind = TARGET_WAITKIND_STOPPED;
ourstatus->value.sig = GDB_SIGNAL_0;
if (debug_threads)
{
debug_printf ("wait_1 ret = %s, stopped "
"while stabilizing threads\n",
target_pid_to_str (ptid_of (current_thread)));
debug_exit ();
}
return ptid_of (current_thread);
}
}
}
}
/* Check whether GDB would be interested in this event. */
/* Check if GDB is interested in this syscall. */
if (WIFSTOPPED (w)
&& WSTOPSIG (w) == SYSCALL_SIGTRAP
&& !gdb_catch_this_syscall (event_child))
{
if (debug_threads)
{
debug_printf ("Ignored syscall for LWP %ld.\n",
lwpid_of (current_thread));
}
resume_one_lwp (event_child, event_child->stepping, 0, NULL);
if (debug_threads)
debug_exit ();
return ignore_event (ourstatus);
}
/* If GDB is not interested in this signal, don't stop other
threads, and don't report it to GDB. Just resume the inferior
right away. We do this for threading-related signals as well as
any that GDB specifically requested we ignore. But never ignore
SIGSTOP if we sent it ourselves, and do not ignore signals when
stepping - they may require special handling to skip the signal
handler. Also never ignore signals that could be caused by a
breakpoint. */
if (WIFSTOPPED (w)
&& current_thread->last_resume_kind != resume_step
&& (
#if defined (USE_THREAD_DB) && !defined (__ANDROID__)
(current_process ()->priv->thread_db != NULL
&& (WSTOPSIG (w) == __SIGRTMIN
|| WSTOPSIG (w) == __SIGRTMIN + 1))
||
#endif
(cs.pass_signals[gdb_signal_from_host (WSTOPSIG (w))]
&& !(WSTOPSIG (w) == SIGSTOP
&& current_thread->last_resume_kind == resume_stop)
&& !linux_wstatus_maybe_breakpoint (w))))
{
siginfo_t info, *info_p;
if (debug_threads)
debug_printf ("Ignored signal %d for LWP %ld.\n",
WSTOPSIG (w), lwpid_of (current_thread));
if (ptrace (PTRACE_GETSIGINFO, lwpid_of (current_thread),
(PTRACE_TYPE_ARG3) 0, &info) == 0)
info_p = &info;
else
info_p = NULL;
if (step_over_finished)
{
/* We cancelled this thread's step-over above. We still
need to unsuspend all other LWPs, and set them back
running again while the signal handler runs. */
unsuspend_all_lwps (event_child);
/* Enqueue the pending signal info so that proceed_all_lwps
doesn't lose it. */
enqueue_pending_signal (event_child, WSTOPSIG (w), info_p);
proceed_all_lwps ();
}
else
{
resume_one_lwp (event_child, event_child->stepping,
WSTOPSIG (w), info_p);
}
if (debug_threads)
debug_exit ();
return ignore_event (ourstatus);
}
/* Note that all addresses are always "out of the step range" when
there's no range to begin with. */
in_step_range = lwp_in_step_range (event_child);
/* If GDB wanted this thread to single step, and the thread is out
of the step range, we always want to report the SIGTRAP, and let
GDB handle it. Watchpoints should always be reported. So should
signals we can't explain. A SIGTRAP we can't explain could be a
GDB breakpoint --- we may or not support Z0 breakpoints. If we
do, we're be able to handle GDB breakpoints on top of internal
breakpoints, by handling the internal breakpoint and still
reporting the event to GDB. If we don't, we're out of luck, GDB
won't see the breakpoint hit. If we see a single-step event but
the thread should be continuing, don't pass the trap to gdb.
That indicates that we had previously finished a single-step but
left the single-step pending -- see
complete_ongoing_step_over. */
report_to_gdb = (!maybe_internal_trap
|| (current_thread->last_resume_kind == resume_step
&& !in_step_range)
|| event_child->stop_reason == TARGET_STOPPED_BY_WATCHPOINT
|| (!in_step_range
&& !bp_explains_trap
&& !trace_event
&& !step_over_finished
&& !(current_thread->last_resume_kind == resume_continue
&& event_child->stop_reason == TARGET_STOPPED_BY_SINGLE_STEP))
|| (gdb_breakpoint_here (event_child->stop_pc)
&& gdb_condition_true_at_breakpoint (event_child->stop_pc)
&& gdb_no_commands_at_breakpoint (event_child->stop_pc))
|| event_child->waitstatus.kind != TARGET_WAITKIND_IGNORE);
run_breakpoint_commands (event_child->stop_pc);
/* We found no reason GDB would want us to stop. We either hit one
of our own breakpoints, or finished an internal step GDB
shouldn't know about. */
if (!report_to_gdb)
{
if (debug_threads)
{
if (bp_explains_trap)
debug_printf ("Hit a gdbserver breakpoint.\n");
if (step_over_finished)
debug_printf ("Step-over finished.\n");
if (trace_event)