blob: f206b8749299f6b1fb041f47b427350335656a58 [file] [log] [blame]
/* GNU/Linux native-dependent code common to multiple platforms.
Copyright (C) 2001-2021 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 "defs.h"
#include "inferior.h"
#include "infrun.h"
#include "target.h"
#include "nat/linux-nat.h"
#include "nat/linux-waitpid.h"
#include "gdbsupport/gdb_wait.h"
#include <unistd.h>
#include <sys/syscall.h>
#include "nat/gdb_ptrace.h"
#include "linux-nat.h"
#include "nat/linux-ptrace.h"
#include "nat/linux-procfs.h"
#include "nat/linux-personality.h"
#include "linux-fork.h"
#include "gdbthread.h"
#include "gdbcmd.h"
#include "regcache.h"
#include "regset.h"
#include "inf-child.h"
#include "inf-ptrace.h"
#include "auxv.h"
#include <sys/procfs.h> /* for elf_gregset etc. */
#include "elf-bfd.h" /* for elfcore_write_* */
#include "gregset.h" /* for gregset */
#include "gdbcore.h" /* for get_exec_file */
#include <ctype.h> /* for isdigit */
#include <sys/stat.h> /* for struct stat */
#include <fcntl.h> /* for O_RDONLY */
#include "inf-loop.h"
#include "gdbsupport/event-loop.h"
#include "event-top.h"
#include <pwd.h>
#include <sys/types.h>
#include <dirent.h>
#include "xml-support.h"
#include <sys/vfs.h>
#include "solib.h"
#include "nat/linux-osdata.h"
#include "linux-tdep.h"
#include "symfile.h"
#include "gdbsupport/agent.h"
#include "tracepoint.h"
#include "gdbsupport/buffer.h"
#include "target-descriptions.h"
#include "gdbsupport/filestuff.h"
#include "objfiles.h"
#include "nat/linux-namespaces.h"
#include "gdbsupport/fileio.h"
#include "gdbsupport/scope-exit.h"
#include "gdbsupport/gdb-sigmask.h"
#include "gdbsupport/common-debug.h"
/* This comment documents high-level logic of this file.
Waiting for events in sync mode
===============================
When waiting for an event in a specific thread, we just use waitpid,
passing the specific pid, and not passing WNOHANG.
When waiting for an event in all threads, waitpid is not quite good:
- 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 instead reported to the TGID pid.
The solution is to always use -1 and WNOHANG, together with
sigsuspend.
First, we use non-blocking waitpid to check for events. If nothing is
found, we use sigsuspend to wait for SIGCHLD. When SIGCHLD arrives,
it means something happened to a child process. As soon as we know
there's an event, we get back to calling nonblocking waitpid.
Note that SIGCHLD should be blocked between waitpid and sigsuspend
calls, so that we don't miss a signal. If SIGCHLD arrives in between,
when it's blocked, the signal becomes pending and sigsuspend
immediately notices it and returns.
Waiting for events in async mode (TARGET_WNOHANG)
=================================================
In async mode, GDB should always be ready to handle both user input
and target events, so neither blocking waitpid nor sigsuspend are
viable options. Instead, we should asynchronously notify the GDB main
event loop whenever there's an unprocessed event from the target. We
detect asynchronous target events by handling SIGCHLD signals. To
notify the event loop about target events, the self-pipe trick is used
--- a pipe is registered as waitable event source in the event loop,
the event loop select/poll's on the read end of this pipe (as well on
other event sources, e.g., stdin), and the SIGCHLD handler writes a
byte to this pipe. This is more portable than relying on
pselect/ppoll, since on kernels that lack those syscalls, libc
emulates them with select/poll+sigprocmask, and that is racy
(a.k.a. plain broken).
Obviously, if we fail to notify the event loop if there's a target
event, it's bad. OTOH, if we notify the event loop when there's no
event from the target, linux_nat_wait will detect that there's no real
event to report, and return event of type TARGET_WAITKIND_IGNORE.
This is mostly harmless, but it will waste time and is better avoided.
The main design point is that every time GDB is outside linux-nat.c,
we have a SIGCHLD handler installed that is called when something
happens to the target and notifies the GDB event loop. Whenever GDB
core decides to handle the event, and calls into linux-nat.c, we
process things as in sync mode, except that the we never block in
sigsuspend.
While processing an event, we may end up momentarily blocked in
waitpid calls. Those waitpid calls, while blocking, are guarantied to
return quickly. E.g., in all-stop mode, before reporting to the core
that an LWP hit a breakpoint, all LWPs are stopped by sending them
SIGSTOP, and synchronously waiting for the SIGSTOP to be reported.
Note that this is different from blocking indefinitely waiting for the
next event --- here, we're already handling an event.
Use of signals
==============
We stop threads by sending a SIGSTOP. The use of SIGSTOP instead of another
signal is not entirely significant; we just need for a signal to be delivered,
so that we can intercept it. SIGSTOP's advantage is that it can not be
blocked. A disadvantage is that it is not a real-time signal, so it can only
be queued once; we do not keep track of other sources of SIGSTOP.
Two other signals that can't be blocked are SIGCONT and SIGKILL. But we can't
use them, because they have special behavior when the signal is generated -
not when it is delivered. SIGCONT resumes the entire thread group and SIGKILL
kills the entire thread group.
A delivered SIGSTOP would stop the entire thread group, not just the thread we
tkill'd. But we never let the SIGSTOP be delivered; we always intercept and
cancel it (by PTRACE_CONT without passing SIGSTOP).
We could use a real-time signal instead. This would solve those problems; we
could use PTRACE_GETSIGINFO to locate the specific stop signals sent by GDB.
But we would still have to have some support for SIGSTOP, since PTRACE_ATTACH
generates it, and there are races with trying to find a signal that is not
blocked.
Exec events
===========
The case of a thread group (process) with 3 or more threads, and a
thread other than the leader execs is worth detailing:
On an exec, the Linux kernel destroys all 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)' state. As soon as all other threads are
reaped, the execing thread changes its tid to the tgid, and the
previous (zombie) leader vanishes, giving place to the "new"
leader. */
#ifndef O_LARGEFILE
#define O_LARGEFILE 0
#endif
struct linux_nat_target *linux_target;
/* Does the current host support PTRACE_GETREGSET? */
enum tribool have_ptrace_getregset = TRIBOOL_UNKNOWN;
static unsigned int debug_linux_nat;
static void
show_debug_linux_nat (struct ui_file *file, int from_tty,
struct cmd_list_element *c, const char *value)
{
fprintf_filtered (file, _("Debugging of GNU/Linux lwp module is %s.\n"),
value);
}
/* Print a linux-nat debug statement. */
#define linux_nat_debug_printf(fmt, ...) \
debug_prefixed_printf_cond (debug_linux_nat, "linux-nat", fmt, ##__VA_ARGS__)
struct simple_pid_list
{
int pid;
int status;
struct simple_pid_list *next;
};
static struct simple_pid_list *stopped_pids;
/* Whether target_thread_events is in effect. */
static int report_thread_events;
/* Async mode support. */
/* The read/write ends of the pipe registered as waitable file in the
event loop. */
static int linux_nat_event_pipe[2] = { -1, -1 };
/* True if we're currently in async mode. */
#define linux_is_async_p() (linux_nat_event_pipe[0] != -1)
/* Flush the event pipe. */
static void
async_file_flush (void)
{
int ret;
char buf;
do
{
ret = read (linux_nat_event_pipe[0], &buf, 1);
}
while (ret >= 0 || (ret == -1 && errno == EINTR));
}
/* Put something (anything, doesn't matter what, or how much) in event
pipe, so that the select/poll in the event-loop realizes we have
something to process. */
static void
async_file_mark (void)
{
int ret;
/* It doesn't really matter what the pipe contains, as long we end
up with something in it. Might as well flush the previous
left-overs. */
async_file_flush ();
do
{
ret = write (linux_nat_event_pipe[1], "+", 1);
}
while (ret == -1 && errno == EINTR);
/* Ignore EAGAIN. If the pipe is full, the event loop will already
be awakened anyway. */
}
static int kill_lwp (int lwpid, int signo);
static int stop_callback (struct lwp_info *lp);
static void block_child_signals (sigset_t *prev_mask);
static void restore_child_signals_mask (sigset_t *prev_mask);
struct lwp_info;
static struct lwp_info *add_lwp (ptid_t ptid);
static void purge_lwp_list (int pid);
static void delete_lwp (ptid_t ptid);
static struct lwp_info *find_lwp_pid (ptid_t ptid);
static int lwp_status_pending_p (struct lwp_info *lp);
static void save_stop_reason (struct lwp_info *lp);
static void maybe_close_proc_mem_file (pid_t pid);
/* LWP accessors. */
/* See nat/linux-nat.h. */
ptid_t
ptid_of_lwp (struct lwp_info *lwp)
{
return lwp->ptid;
}
/* 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->step;
}
/* 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;
}
/* Return the ptrace options that we want to try to enable. */
static int
linux_nat_ptrace_options (int attached)
{
int options = 0;
if (!attached)
options |= PTRACE_O_EXITKILL;
options |= (PTRACE_O_TRACESYSGOOD
| PTRACE_O_TRACEVFORKDONE
| PTRACE_O_TRACEVFORK
| PTRACE_O_TRACEFORK
| PTRACE_O_TRACEEXEC);
return options;
}
/* Initialize ptrace and procfs warnings and check for supported
ptrace features given PID.
ATTACHED should be nonzero iff we attached to the inferior. */
static void
linux_init_ptrace_procfs (pid_t pid, int attached)
{
int options = linux_nat_ptrace_options (attached);
linux_enable_event_reporting (pid, options);
linux_ptrace_init_warnings ();
linux_proc_init_warnings ();
}
linux_nat_target::~linux_nat_target ()
{}
void
linux_nat_target::post_attach (int pid)
{
linux_init_ptrace_procfs (pid, 1);
}
void
linux_nat_target::post_startup_inferior (ptid_t ptid)
{
linux_init_ptrace_procfs (ptid.pid (), 0);
}
/* Return the number of known LWPs in the tgid given by PID. */
static int
num_lwps (int pid)
{
int count = 0;
struct lwp_info *lp;
for (lp = lwp_list; lp; lp = lp->next)
if (lp->ptid.pid () == pid)
count++;
return count;
}
/* Deleter for lwp_info unique_ptr specialisation. */
struct lwp_deleter
{
void operator() (struct lwp_info *lwp) const
{
delete_lwp (lwp->ptid);
}
};
/* A unique_ptr specialisation for lwp_info. */
typedef std::unique_ptr<struct lwp_info, lwp_deleter> lwp_info_up;
/* Target hook for follow_fork. On entry inferior_ptid must be the
ptid of the followed inferior. At return, inferior_ptid will be
unchanged. */
void
linux_nat_target::follow_fork (bool follow_child, bool detach_fork)
{
if (!follow_child)
{
struct lwp_info *child_lp = NULL;
int has_vforked;
ptid_t parent_ptid, child_ptid;
int parent_pid, child_pid;
has_vforked = (inferior_thread ()->pending_follow.kind
== TARGET_WAITKIND_VFORKED);
parent_ptid = inferior_ptid;
child_ptid = inferior_thread ()->pending_follow.value.related_pid;
parent_pid = parent_ptid.lwp ();
child_pid = child_ptid.lwp ();
/* We're already attached to the parent, by default. */
child_lp = add_lwp (child_ptid);
child_lp->stopped = 1;
child_lp->last_resume_kind = resume_stop;
/* Detach new forked process? */
if (detach_fork)
{
int child_stop_signal = 0;
bool detach_child = true;
/* Move CHILD_LP into a unique_ptr and clear the source pointer
to prevent us doing anything stupid with it. */
lwp_info_up child_lp_ptr (child_lp);
child_lp = nullptr;
linux_target->low_prepare_to_resume (child_lp_ptr.get ());
/* When debugging an inferior in an architecture that supports
hardware single stepping on a kernel without commit
6580807da14c423f0d0a708108e6df6ebc8bc83d, the vfork child
process starts with the TIF_SINGLESTEP/X86_EFLAGS_TF bits
set if the parent process had them set.
To work around this, single step the child process
once before detaching to clear the flags. */
/* Note that we consult the parent's architecture instead of
the child's because there's no inferior for the child at
this point. */
if (!gdbarch_software_single_step_p (target_thread_architecture
(parent_ptid)))
{
int status;
linux_disable_event_reporting (child_pid);
if (ptrace (PTRACE_SINGLESTEP, child_pid, 0, 0) < 0)
perror_with_name (_("Couldn't do single step"));
if (my_waitpid (child_pid, &status, 0) < 0)
perror_with_name (_("Couldn't wait vfork process"));
else
{
detach_child = WIFSTOPPED (status);
child_stop_signal = WSTOPSIG (status);
}
}
if (detach_child)
{
int signo = child_stop_signal;
if (signo != 0
&& !signal_pass_state (gdb_signal_from_host (signo)))
signo = 0;
ptrace (PTRACE_DETACH, child_pid, 0, signo);
}
}
else
{
/* Switching inferior_ptid is not enough, because then
inferior_thread () would crash by not finding the thread
in the current inferior. */
scoped_restore_current_thread restore_current_thread;
thread_info *child = find_thread_ptid (this, child_ptid);
switch_to_thread (child);
/* Let the thread_db layer learn about this new process. */
check_for_thread_db ();
}
if (has_vforked)
{
struct lwp_info *parent_lp;
parent_lp = find_lwp_pid (parent_ptid);
gdb_assert (linux_supports_tracefork () >= 0);
if (linux_supports_tracevforkdone ())
{
linux_nat_debug_printf ("waiting for VFORK_DONE on %d",
parent_pid);
parent_lp->stopped = 1;
/* We'll handle the VFORK_DONE event like any other
event, in target_wait. */
}
else
{
/* We can't insert breakpoints until the child has
finished with the shared memory region. We need to
wait until that happens. Ideal would be to just
call:
- ptrace (PTRACE_SYSCALL, parent_pid, 0, 0);
- waitpid (parent_pid, &status, __WALL);
However, most architectures can't handle a syscall
being traced on the way out if it wasn't traced on
the way in.
We might also think to loop, continuing the child
until it exits or gets a SIGTRAP. One problem is
that the child might call ptrace with PTRACE_TRACEME.
There's no simple and reliable way to figure out when
the vforked child will be done with its copy of the
shared memory. We could step it out of the syscall,
two instructions, let it go, and then single-step the
parent once. When we have hardware single-step, this
would work; with software single-step it could still
be made to work but we'd have to be able to insert
single-step breakpoints in the child, and we'd have
to insert -just- the single-step breakpoint in the
parent. Very awkward.
In the end, the best we can do is to make sure it
runs for a little while. Hopefully it will be out of
range of any breakpoints we reinsert. Usually this
is only the single-step breakpoint at vfork's return
point. */
linux_nat_debug_printf ("no VFORK_DONE support, sleeping a bit");
usleep (10000);
/* Pretend we've seen a PTRACE_EVENT_VFORK_DONE event,
and leave it pending. The next linux_nat_resume call
will notice a pending event, and bypasses actually
resuming the inferior. */
parent_lp->status = 0;
parent_lp->waitstatus.kind = TARGET_WAITKIND_VFORK_DONE;
parent_lp->stopped = 1;
/* If we're in async mode, need to tell the event loop
there's something here to process. */
if (target_is_async_p ())
async_file_mark ();
}
}
}
else
{
struct lwp_info *child_lp;
child_lp = add_lwp (inferior_ptid);
child_lp->stopped = 1;
child_lp->last_resume_kind = resume_stop;
/* Let the thread_db layer learn about this new process. */
check_for_thread_db ();
}
}
int
linux_nat_target::insert_fork_catchpoint (int pid)
{
return !linux_supports_tracefork ();
}
int
linux_nat_target::remove_fork_catchpoint (int pid)
{
return 0;
}
int
linux_nat_target::insert_vfork_catchpoint (int pid)
{
return !linux_supports_tracefork ();
}
int
linux_nat_target::remove_vfork_catchpoint (int pid)
{
return 0;
}
int
linux_nat_target::insert_exec_catchpoint (int pid)
{
return !linux_supports_tracefork ();
}
int
linux_nat_target::remove_exec_catchpoint (int pid)
{
return 0;
}
int
linux_nat_target::set_syscall_catchpoint (int pid, bool needed, int any_count,
gdb::array_view<const int> syscall_counts)
{
if (!linux_supports_tracesysgood ())
return 1;
/* On GNU/Linux, we ignore the arguments. It means that we only
enable the syscall catchpoints, but do not disable them.
Also, we do not use the `syscall_counts' information because we do not
filter system calls here. We let GDB do the logic for us. */
return 0;
}
/* List of known LWPs, keyed by LWP PID. This speeds up the common
case of mapping a PID returned from the kernel to our corresponding
lwp_info data structure. */
static htab_t lwp_lwpid_htab;
/* Calculate a hash from a lwp_info's LWP PID. */
static hashval_t
lwp_info_hash (const void *ap)
{
const struct lwp_info *lp = (struct lwp_info *) ap;
pid_t pid = lp->ptid.lwp ();
return iterative_hash_object (pid, 0);
}
/* Equality function for the lwp_info hash table. Compares the LWP's
PID. */
static int
lwp_lwpid_htab_eq (const void *a, const void *b)
{
const struct lwp_info *entry = (const struct lwp_info *) a;
const struct lwp_info *element = (const struct lwp_info *) b;
return entry->ptid.lwp () == element->ptid.lwp ();
}
/* Create the lwp_lwpid_htab hash table. */
static void
lwp_lwpid_htab_create (void)
{
lwp_lwpid_htab = htab_create (100, lwp_info_hash, lwp_lwpid_htab_eq, NULL);
}
/* Add LP to the hash table. */
static void
lwp_lwpid_htab_add_lwp (struct lwp_info *lp)
{
void **slot;
slot = htab_find_slot (lwp_lwpid_htab, lp, INSERT);
gdb_assert (slot != NULL && *slot == NULL);
*slot = lp;
}
/* Head of doubly-linked list of known LWPs. Sorted by reverse
creation order. This order is assumed in some cases. E.g.,
reaping status after killing alls lwps of a process: the leader LWP
must be reaped last. */
struct lwp_info *lwp_list;
/* Add LP to sorted-by-reverse-creation-order doubly-linked list. */
static void
lwp_list_add (struct lwp_info *lp)
{
lp->next = lwp_list;
if (lwp_list != NULL)
lwp_list->prev = lp;
lwp_list = lp;
}
/* Remove LP from sorted-by-reverse-creation-order doubly-linked
list. */
static void
lwp_list_remove (struct lwp_info *lp)
{
/* Remove from sorted-by-creation-order list. */
if (lp->next != NULL)
lp->next->prev = lp->prev;
if (lp->prev != NULL)
lp->prev->next = lp->next;
if (lp == lwp_list)
lwp_list = lp->next;
}
/* Signal mask for use with sigsuspend in linux_nat_wait, initialized in
_initialize_linux_nat. */
static sigset_t suspend_mask;
/* Signals to block to make that sigsuspend work. */
static sigset_t blocked_mask;
/* SIGCHLD action. */
static struct sigaction sigchld_action;
/* Block child signals (SIGCHLD and linux threads signals), and store
the previous mask in PREV_MASK. */
static void
block_child_signals (sigset_t *prev_mask)
{
/* Make sure SIGCHLD is blocked. */
if (!sigismember (&blocked_mask, SIGCHLD))
sigaddset (&blocked_mask, SIGCHLD);
gdb_sigmask (SIG_BLOCK, &blocked_mask, prev_mask);
}
/* Restore child signals mask, previously returned by
block_child_signals. */
static void
restore_child_signals_mask (sigset_t *prev_mask)
{
gdb_sigmask (SIG_SETMASK, prev_mask, NULL);
}
/* Mask of signals to pass directly to the inferior. */
static sigset_t pass_mask;
/* Update signals to pass to the inferior. */
void
linux_nat_target::pass_signals
(gdb::array_view<const unsigned char> pass_signals)
{
int signo;
sigemptyset (&pass_mask);
for (signo = 1; signo < NSIG; signo++)
{
int target_signo = gdb_signal_from_host (signo);
if (target_signo < pass_signals.size () && pass_signals[target_signo])
sigaddset (&pass_mask, signo);
}
}
/* Prototypes for local functions. */
static int stop_wait_callback (struct lwp_info *lp);
static int resume_stopped_resumed_lwps (struct lwp_info *lp, const ptid_t wait_ptid);
static int check_ptrace_stopped_lwp_gone (struct lwp_info *lp);
/* Destroy and free LP. */
static void
lwp_free (struct lwp_info *lp)
{
/* Let the arch specific bits release arch_lwp_info. */
linux_target->low_delete_thread (lp->arch_private);
xfree (lp);
}
/* Traversal function for purge_lwp_list. */
static int
lwp_lwpid_htab_remove_pid (void **slot, void *info)
{
struct lwp_info *lp = (struct lwp_info *) *slot;
int pid = *(int *) info;
if (lp->ptid.pid () == pid)
{
htab_clear_slot (lwp_lwpid_htab, slot);
lwp_list_remove (lp);
lwp_free (lp);
}
return 1;
}
/* Remove all LWPs belong to PID from the lwp list. */
static void
purge_lwp_list (int pid)
{
htab_traverse_noresize (lwp_lwpid_htab, lwp_lwpid_htab_remove_pid, &pid);
}
/* Add the LWP specified by PTID to the list. PTID is the first LWP
in the process. Return a pointer to the structure describing the
new LWP.
This differs from add_lwp in that we don't let the arch specific
bits know about this new thread. Current clients of this callback
take the opportunity to install watchpoints in the new thread, and
we shouldn't do that for the first thread. If we're spawning a
child ("run"), the thread executes the shell wrapper first, and we
shouldn't touch it until it execs the program we want to debug.
For "attach", it'd be okay to call the callback, but it's not
necessary, because watchpoints can't yet have been inserted into
the inferior. */
static struct lwp_info *
add_initial_lwp (ptid_t ptid)
{
struct lwp_info *lp;
gdb_assert (ptid.lwp_p ());
lp = XNEW (struct lwp_info);
memset (lp, 0, sizeof (struct lwp_info));
lp->last_resume_kind = resume_continue;
lp->waitstatus.kind = TARGET_WAITKIND_IGNORE;
lp->ptid = ptid;
lp->core = -1;
/* Add to sorted-by-reverse-creation-order list. */
lwp_list_add (lp);
/* Add to keyed-by-pid htab. */
lwp_lwpid_htab_add_lwp (lp);
return lp;
}
/* Add the LWP specified by PID to the list. Return a pointer to the
structure describing the new LWP. The LWP should already be
stopped. */
static struct lwp_info *
add_lwp (ptid_t ptid)
{
struct lwp_info *lp;
lp = add_initial_lwp (ptid);
/* Let the arch specific bits know about this new thread. Current
clients of this callback take the opportunity to install
watchpoints in the new thread. We don't do this for the first
thread though. See add_initial_lwp. */
linux_target->low_new_thread (lp);
return lp;
}
/* Remove the LWP specified by PID from the list. */
static void
delete_lwp (ptid_t ptid)
{
struct lwp_info *lp;
void **slot;
struct lwp_info dummy;
dummy.ptid = ptid;
slot = htab_find_slot (lwp_lwpid_htab, &dummy, NO_INSERT);
if (slot == NULL)
return;
lp = *(struct lwp_info **) slot;
gdb_assert (lp != NULL);
htab_clear_slot (lwp_lwpid_htab, slot);
/* Remove from sorted-by-creation-order list. */
lwp_list_remove (lp);
/* Release. */
lwp_free (lp);
}
/* Return a pointer to the structure describing the LWP corresponding
to PID. If no corresponding LWP could be found, return NULL. */
static struct lwp_info *
find_lwp_pid (ptid_t ptid)
{
struct lwp_info *lp;
int lwp;
struct lwp_info dummy;
if (ptid.lwp_p ())
lwp = ptid.lwp ();
else
lwp = ptid.pid ();
dummy.ptid = ptid_t (0, lwp, 0);
lp = (struct lwp_info *) htab_find (lwp_lwpid_htab, &dummy);
return lp;
}
/* See nat/linux-nat.h. */
struct lwp_info *
iterate_over_lwps (ptid_t filter,
gdb::function_view<iterate_over_lwps_ftype> callback)
{
struct lwp_info *lp, *lpnext;
for (lp = lwp_list; lp; lp = lpnext)
{
lpnext = lp->next;
if (lp->ptid.matches (filter))
{
if (callback (lp) != 0)
return lp;
}
}
return NULL;
}
/* Update our internal state when changing from one checkpoint to
another indicated by NEW_PTID. We can only switch single-threaded
applications, so we only create one new LWP, and the previous list
is discarded. */
void
linux_nat_switch_fork (ptid_t new_ptid)
{
struct lwp_info *lp;
purge_lwp_list (inferior_ptid.pid ());
lp = add_lwp (new_ptid);
lp->stopped = 1;
/* This changes the thread's ptid while preserving the gdb thread
num. Also changes the inferior pid, while preserving the
inferior num. */
thread_change_ptid (linux_target, inferior_ptid, new_ptid);
/* We've just told GDB core that the thread changed target id, but,
in fact, it really is a different thread, with different register
contents. */
registers_changed ();
}
/* Handle the exit of a single thread LP. */
static void
exit_lwp (struct lwp_info *lp)
{
struct thread_info *th = find_thread_ptid (linux_target, lp->ptid);
if (th)
{
if (print_thread_events)
printf_unfiltered (_("[%s exited]\n"),
target_pid_to_str (lp->ptid).c_str ());
delete_thread (th);
}
delete_lwp (lp->ptid);
}
/* Wait for the LWP specified by LP, which we have just attached to.
Returns a wait status for that LWP, to cache. */
static int
linux_nat_post_attach_wait (ptid_t ptid, int *signalled)
{
pid_t new_pid, pid = ptid.lwp ();
int status;
if (linux_proc_pid_is_stopped (pid))
{
linux_nat_debug_printf ("Attaching to a stopped process");
/* 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 (pid, SIGSTOP);
/* Finally, resume the stopped process. This will deliver the SIGSTOP
(or a higher priority signal, just like normal PTRACE_ATTACH). */
ptrace (PTRACE_CONT, pid, 0, 0);
}
/* Make sure the initial process is stopped. The user-level threads
layer might want to poke around in the inferior, and that won't
work if things haven't stabilized yet. */
new_pid = my_waitpid (pid, &status, __WALL);
gdb_assert (pid == new_pid);
if (!WIFSTOPPED (status))
{
/* The pid we tried to attach has apparently just exited. */
linux_nat_debug_printf ("Failed to stop %d: %s", pid,
status_to_str (status).c_str ());
return status;
}
if (WSTOPSIG (status) != SIGSTOP)
{
*signalled = 1;
linux_nat_debug_printf ("Received %s after attaching",
status_to_str (status).c_str ());
}
return status;
}
void
linux_nat_target::create_inferior (const char *exec_file,
const std::string &allargs,
char **env, int from_tty)
{
maybe_disable_address_space_randomization restore_personality
(disable_randomization);
/* The fork_child mechanism is synchronous and calls target_wait, so
we have to mask the async mode. */
/* Make sure we report all signals during startup. */
pass_signals ({});
inf_ptrace_target::create_inferior (exec_file, allargs, env, from_tty);
}
/* 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)
{
struct lwp_info *lp;
/* Ignore LWPs we're already attached to. */
lp = find_lwp_pid (ptid);
if (lp == NULL)
{
int lwpid = ptid.lwp ();
if (ptrace (PTRACE_ATTACH, lwpid, 0, 0) < 0)
{
int err = errno;
/* 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)))
{
linux_nat_debug_printf
("Cannot attach to lwp %d: thread is gone (%d: %s)",
lwpid, err, safe_strerror (err));
}
else
{
std::string reason
= linux_ptrace_attach_fail_reason_string (ptid, err);
warning (_("Cannot attach to lwp %d: %s"),
lwpid, reason.c_str ());
}
}
else
{
linux_nat_debug_printf ("PTRACE_ATTACH %s, 0, 0 (OK)",
target_pid_to_str (ptid).c_str ());
lp = add_lwp (ptid);
/* The next time we wait for this LWP we'll see a SIGSTOP as
PTRACE_ATTACH brings it to a halt. */
lp->signalled = 1;
/* We need to wait for a stop before being able to make the
next ptrace call on this LWP. */
lp->must_set_ptrace_flags = 1;
/* So that wait collects the SIGSTOP. */
lp->resumed = 1;
/* Also add the LWP to gdb's thread list, in case a
matching libthread_db is not found (or the process uses
raw clone). */
add_thread (linux_target, lp->ptid);
set_running (linux_target, lp->ptid, true);
set_executing (linux_target, lp->ptid, true);
}
return 1;
}
return 0;
}
void
linux_nat_target::attach (const char *args, int from_tty)
{
struct lwp_info *lp;
int status;
ptid_t ptid;
/* Make sure we report all signals during attach. */
pass_signals ({});
try
{
inf_ptrace_target::attach (args, from_tty);
}
catch (const gdb_exception_error &ex)
{
pid_t pid = parse_pid_to_attach (args);
std::string reason = linux_ptrace_attach_fail_reason (pid);
if (!reason.empty ())
throw_error (ex.error, "warning: %s\n%s", reason.c_str (),
ex.what ());
else
throw_error (ex.error, "%s", ex.what ());
}
/* The ptrace base target adds the main thread with (pid,0,0)
format. Decorate it with lwp info. */
ptid = ptid_t (inferior_ptid.pid (),
inferior_ptid.pid (),
0);
thread_change_ptid (linux_target, inferior_ptid, ptid);
/* Add the initial process as the first LWP to the list. */
lp = add_initial_lwp (ptid);
status = linux_nat_post_attach_wait (lp->ptid, &lp->signalled);
if (!WIFSTOPPED (status))
{
if (WIFEXITED (status))
{
int exit_code = WEXITSTATUS (status);
target_terminal::ours ();
target_mourn_inferior (inferior_ptid);
if (exit_code == 0)
error (_("Unable to attach: program exited normally."));
else
error (_("Unable to attach: program exited with code %d."),
exit_code);
}
else if (WIFSIGNALED (status))
{
enum gdb_signal signo;
target_terminal::ours ();
target_mourn_inferior (inferior_ptid);
signo = gdb_signal_from_host (WTERMSIG (status));
error (_("Unable to attach: program terminated with signal "
"%s, %s."),
gdb_signal_to_name (signo),
gdb_signal_to_string (signo));
}
internal_error (__FILE__, __LINE__,
_("unexpected status %d for PID %ld"),
status, (long) ptid.lwp ());
}
lp->stopped = 1;
/* Save the wait status to report later. */
lp->resumed = 1;
linux_nat_debug_printf ("waitpid %ld, saving status %s",
(long) lp->ptid.pid (),
status_to_str (status).c_str ());
lp->status = status;
/* We must attach to every LWP. If /proc is mounted, use that to
find them now. The inferior may be using raw clone instead of
using pthreads. But even if it is using pthreads, 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 (lp->ptid.pid (),
attach_proc_task_lwp_callback);
if (target_can_async_p ())
target_async (1);
}
/* Get pending signal of THREAD as a host signal number, 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 lwp_info *lp)
{
enum gdb_signal signo = GDB_SIGNAL_0;
/* If we paused threads momentarily, we may have stored pending
events in lp->status or lp->waitstatus (see stop_wait_callback),
and GDB core hasn't seen any signal for those threads.
Otherwise, the last signal reported to the core is found in the
thread object's stop_signal.
There's a corner case that isn't handled here at present. Only
if the thread stopped with a TARGET_WAITKIND_STOPPED does
stop_signal make sense as a real signal to pass to the inferior.
Some catchpoint related events, like
TARGET_WAITKIND_(V)FORK|EXEC|SYSCALL, have their stop_signal set
to GDB_SIGNAL_SIGTRAP when the catchpoint triggers. But,
those traps are debug API (ptrace in our case) related and
induced; the inferior wouldn't see them if it wasn't being
traced. Hence, we should never pass them to the inferior, even
when set to pass state. Since this corner case isn't handled by
infrun.c when proceeding with a signal, for consistency, neither
do we handle it here (or elsewhere in the file we check for
signal pass state). Normally SIGTRAP isn't set to pass state, so
this is really a corner case. */
if (lp->waitstatus.kind != TARGET_WAITKIND_IGNORE)
signo = GDB_SIGNAL_0; /* a pending ptrace event, not a real signal. */
else if (lp->status)
signo = gdb_signal_from_host (WSTOPSIG (lp->status));
else
{
struct thread_info *tp = find_thread_ptid (linux_target, lp->ptid);
if (target_is_non_stop_p () && !tp->executing)
{
if (tp->suspend.waitstatus_pending_p)
signo = tp->suspend.waitstatus.value.sig;
else
signo = tp->suspend.stop_signal;
}
else if (!target_is_non_stop_p ())
{
ptid_t last_ptid;
process_stratum_target *last_target;
get_last_target_status (&last_target, &last_ptid, nullptr);
if (last_target == linux_target
&& lp->ptid.lwp () == last_ptid.lwp ())
signo = tp->suspend.stop_signal;
}
}
if (signo == GDB_SIGNAL_0)
{
linux_nat_debug_printf ("lwp %s has no pending signal",
target_pid_to_str (lp->ptid).c_str ());
}
else if (!signal_pass_state (signo))
{
linux_nat_debug_printf
("lwp %s had signal %s but it is in no pass state",
target_pid_to_str (lp->ptid).c_str (), gdb_signal_to_string (signo));
}
else
{
linux_nat_debug_printf ("lwp %s has pending signal %s",
target_pid_to_str (lp->ptid).c_str (),
gdb_signal_to_string (signo));
return gdb_signal_to_host (signo);
}
return 0;
}
/* Detach from LP. If SIGNO_P is non-NULL, then it points to the
signal number that should be passed to the LWP when detaching.
Otherwise pass any pending signal the LWP may have, if any. */
static void
detach_one_lwp (struct lwp_info *lp, int *signo_p)
{
int lwpid = lp->ptid.lwp ();
int signo;
gdb_assert (lp->status == 0 || WIFSTOPPED (lp->status));
if (lp->status != 0)
linux_nat_debug_printf ("Pending %s for %s on detach.",
strsignal (WSTOPSIG (lp->status)),
target_pid_to_str (lp->ptid).c_str ());
/* If there is a pending SIGSTOP, get rid of it. */
if (lp->signalled)
{
linux_nat_debug_printf ("Sending SIGCONT to %s",
target_pid_to_str (lp->ptid).c_str ());
kill_lwp (lwpid, SIGCONT);
lp->signalled = 0;
}
if (signo_p == NULL)
{
/* Pass on any pending signal for this LWP. */
signo = get_detach_signal (lp);
}
else
signo = *signo_p;
/* 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
{
linux_target->low_prepare_to_resume (lp);
}
catch (const gdb_exception_error &ex)
{
if (!check_ptrace_stopped_lwp_gone (lp))
throw;
}
if (ptrace (PTRACE_DETACH, lwpid, 0, signo) < 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 (lp->ptid).c_str (),
safe_strerror (save_errno));
}
}
else
linux_nat_debug_printf ("PTRACE_DETACH (%s, %s, 0) (OK)",
target_pid_to_str (lp->ptid).c_str (),
strsignal (signo));
delete_lwp (lp->ptid);
}
static int
detach_callback (struct lwp_info *lp)
{
/* 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 (lp->ptid.lwp () != lp->ptid.pid ())
detach_one_lwp (lp, NULL);
return 0;
}
void
linux_nat_target::detach (inferior *inf, int from_tty)
{
struct lwp_info *main_lwp;
int pid = inf->pid;
/* Don't unregister from the event loop, as there may be other
inferiors running. */
/* Stop all threads before detaching. ptrace requires that the
thread is stopped to successfully detach. */
iterate_over_lwps (ptid_t (pid), stop_callback);
/* ... and wait until all of them have reported back that
they're no longer running. */
iterate_over_lwps (ptid_t (pid), stop_wait_callback);
/* We can now safely remove breakpoints. We don't this in earlier
in common code because this target doesn't currently support
writing memory while the inferior is running. */
remove_breakpoints_inf (current_inferior ());
iterate_over_lwps (ptid_t (pid), detach_callback);
/* Only the initial process should be left right now. */
gdb_assert (num_lwps (pid) == 1);
main_lwp = find_lwp_pid (ptid_t (pid));
if (forks_exist_p ())
{
/* Multi-fork case. The current inferior_ptid is being detached
from, but there are other viable forks to debug. Detach from
the current fork, and context-switch to the first
available. */
linux_fork_detach (from_tty);
}
else
{
target_announce_detach (from_tty);
/* Pass on any pending signal for the last LWP. */
int signo = get_detach_signal (main_lwp);
detach_one_lwp (main_lwp, &signo);
detach_success (inf);
}
maybe_close_proc_mem_file (pid);
}
/* Resume execution of the inferior process. If STEP is nonzero,
single-step it. If SIGNAL is nonzero, give it that signal. */
static void
linux_resume_one_lwp_throw (struct lwp_info *lp, int step,
enum gdb_signal signo)
{
lp->step = step;
/* stop_pc doubles as the PC the LWP had when it was last resumed.
We only presently need that if the LWP is stepped though (to
handle the case of stepping a breakpoint instruction). */
if (step)
{
struct regcache *regcache = get_thread_regcache (linux_target, lp->ptid);
lp->stop_pc = regcache_read_pc (regcache);
}
else
lp->stop_pc = 0;
linux_target->low_prepare_to_resume (lp);
linux_target->low_resume (lp->ptid, step, signo);
/* Successfully resumed. Clear state that no longer makes sense,
and mark the LWP as running. Must not do this before resuming
otherwise if that fails other code will be confused. E.g., we'd
later try to stop the LWP and hang forever waiting for a stop
status. Note that we must not throw after this is cleared,
otherwise handle_zombie_lwp_error would get confused. */
lp->stopped = 0;
lp->core = -1;
lp->stop_reason = TARGET_STOPPED_BY_NO_REASON;
registers_changed_ptid (linux_target, lp->ptid);
}
/* Called when we try to resume a stopped LWP and that errors out. If
the LWP is no longer in ptrace-stopped state (meaning it's zombie,
or about to become), discard the error, clear any pending status
the LWP may have, and return true (we'll collect the exit status
soon enough). Otherwise, return false. */
static int
check_ptrace_stopped_lwp_gone (struct lwp_info *lp)
{
/* If we get an error after resuming the LWP successfully, we'd
confuse !T state for the LWP being gone. */
gdb_assert (lp->stopped);
/* We can't just check whether the LWP is in 'Z (Zombie)' state,
because even if ptrace failed with ESRCH, the tracee may be "not
yet fully dead", but already refusing ptrace requests. In that
case the tracee has 'R (Running)' state for a little bit
(observed in Linux 3.18). See also the note on ESRCH in the
ptrace(2) man page. Instead, check whether the LWP has any state
other than ptrace-stopped. */
/* Don't assume anything if /proc/PID/status can't be read. */
if (linux_proc_pid_is_trace_stopped_nowarn (lp->ptid.lwp ()) == 0)
{
lp->stop_reason = TARGET_STOPPED_BY_NO_REASON;
lp->status = 0;
lp->waitstatus.kind = TARGET_WAITKIND_IGNORE;
return 1;
}
return 0;
}
/* Like linux_resume_one_lwp_throw, but no error is thrown if the LWP
disappears while we try to resume it. */
static void
linux_resume_one_lwp (struct lwp_info *lp, int step, enum gdb_signal signo)
{
try
{
linux_resume_one_lwp_throw (lp, step, signo);
}
catch (const gdb_exception_error &ex)
{
if (!check_ptrace_stopped_lwp_gone (lp))
throw;
}
}
/* Resume LP. */
static void
resume_lwp (struct lwp_info *lp, int step, enum gdb_signal signo)
{
if (lp->stopped)
{
struct inferior *inf = find_inferior_ptid (linux_target, lp->ptid);
if (inf->vfork_child != NULL)
{
linux_nat_debug_printf ("Not resuming %s (vfork parent)",
target_pid_to_str (lp->ptid).c_str ());
}
else if (!lwp_status_pending_p (lp))
{
linux_nat_debug_printf ("Resuming sibling %s, %s, %s",
target_pid_to_str (lp->ptid).c_str (),
(signo != GDB_SIGNAL_0
? strsignal (gdb_signal_to_host (signo))
: "0"),
step ? "step" : "resume");
linux_resume_one_lwp (lp, step, signo);
}
else
{
linux_nat_debug_printf ("Not resuming sibling %s (has pending)",
target_pid_to_str (lp->ptid).c_str ());
}
}
else
linux_nat_debug_printf ("Not resuming sibling %s (not stopped)",
target_pid_to_str (lp->ptid).c_str ());
}
/* Callback for iterate_over_lwps. If LWP is EXCEPT, do nothing.
Resume LWP with the last stop signal, if it is in pass state. */
static int
linux_nat_resume_callback (struct lwp_info *lp, struct lwp_info *except)
{
enum gdb_signal signo = GDB_SIGNAL_0;
if (lp == except)
return 0;
if (lp->stopped)
{
struct thread_info *thread;
thread = find_thread_ptid (linux_target, lp->ptid);
if (thread != NULL)
{
signo = thread->suspend.stop_signal;
thread->suspend.stop_signal = GDB_SIGNAL_0;
}
}
resume_lwp (lp, 0, signo);
return 0;
}
static int
resume_clear_callback (struct lwp_info *lp)
{
lp->resumed = 0;
lp->last_resume_kind = resume_stop;
return 0;
}
static int
resume_set_callback (struct lwp_info *lp)
{
lp->resumed = 1;
lp->last_resume_kind = resume_continue;
return 0;
}
void
linux_nat_target::resume (ptid_t ptid, int step, enum gdb_signal signo)
{
struct lwp_info *lp;
int resume_many;
linux_nat_debug_printf ("Preparing to %s %s, %s, inferior_ptid %s",
step ? "step" : "resume",
target_pid_to_str (ptid).c_str (),
(signo != GDB_SIGNAL_0
? strsignal (gdb_signal_to_host (signo)) : "0"),
target_pid_to_str (inferior_ptid).c_str ());
/* A specific PTID means `step only this process id'. */
resume_many = (minus_one_ptid == ptid
|| ptid.is_pid ());
/* Mark the lwps we're resuming as resumed and update their
last_resume_kind to resume_continue. */
iterate_over_lwps (ptid, resume_set_callback);
/* See if it's the current inferior that should be handled
specially. */
if (resume_many)
lp = find_lwp_pid (inferior_ptid);
else
lp = find_lwp_pid (ptid);
gdb_assert (lp != NULL);
/* Remember if we're stepping. */
lp->last_resume_kind = step ? resume_step : resume_continue;
/* If we have a pending wait status for this thread, there is no
point in resuming the process. But first make sure that
linux_nat_wait won't preemptively handle the event - we
should never take this short-circuit if we are going to
leave LP running, since we have skipped resuming all the
other threads. This bit of code needs to be synchronized
with linux_nat_wait. */
if (lp->status && WIFSTOPPED (lp->status))
{
if (!lp->step
&& WSTOPSIG (lp->status)
&& sigismember (&pass_mask, WSTOPSIG (lp->status)))
{
linux_nat_debug_printf
("Not short circuiting for ignored status 0x%x", lp->status);
/* FIXME: What should we do if we are supposed to continue
this thread with a signal? */
gdb_assert (signo == GDB_SIGNAL_0);
signo = gdb_signal_from_host (WSTOPSIG (lp->status));
lp->status = 0;
}
}
if (lwp_status_pending_p (lp))
{
/* FIXME: What should we do if we are supposed to continue
this thread with a signal? */
gdb_assert (signo == GDB_SIGNAL_0);
linux_nat_debug_printf ("Short circuiting for status 0x%x",
lp->status);
if (target_can_async_p ())
{
target_async (1);
/* Tell the event loop we have something to process. */
async_file_mark ();
}
return;
}
if (resume_many)
iterate_over_lwps (ptid, [=] (struct lwp_info *info)
{
return linux_nat_resume_callback (info, lp);
});
linux_nat_debug_printf ("%s %s, %s (resume event thread)",
step ? "PTRACE_SINGLESTEP" : "PTRACE_CONT",
target_pid_to_str (lp->ptid).c_str (),
(signo != GDB_SIGNAL_0
? strsignal (gdb_signal_to_host (signo)) : "0"));
linux_resume_one_lwp (lp, step, signo);
if (target_can_async_p ())
target_async (1);
}
/* Send a signal to an LWP. */
static int
kill_lwp (int lwpid, int signo)
{
int ret;
errno = 0;
ret = syscall (__NR_tkill, lwpid, signo);
if (errno == ENOSYS)
{
/* If tkill fails, then we are not using nptl threads, a
configuration we no longer support. */
perror_with_name (("tkill"));
}
return ret;
}
/* Handle a GNU/Linux syscall trap wait response. If we see a syscall
event, check if the core is interested in it: if not, ignore the
event, and keep waiting; otherwise, we need to toggle the LWP's
syscall entry/exit status, since the ptrace event itself doesn't
indicate it, and report the trap to higher layers. */
static int
linux_handle_syscall_trap (struct lwp_info *lp, int stopping)
{
struct target_waitstatus *ourstatus = &lp->waitstatus;
struct gdbarch *gdbarch = target_thread_architecture (lp->ptid);
thread_info *thread = find_thread_ptid (linux_target, lp->ptid);
int syscall_number = (int) gdbarch_get_syscall_number (gdbarch, thread);
if (stopping)
{
/* If we're stopping threads, there's a SIGSTOP pending, which
makes it so that the LWP reports an immediate syscall return,
followed by the SIGSTOP. Skip seeing that "return" using
PTRACE_CONT directly, and let stop_wait_callback collect the
SIGSTOP. Later when the thread is resumed, a new syscall
entry event. If we didn't do this (and returned 0), we'd
leave a syscall entry pending, and our caller, by using
PTRACE_CONT to collect the SIGSTOP, skips the syscall return
itself. Later, when the user re-resumes this LWP, we'd see
another syscall entry event and we'd mistake it for a return.
If stop_wait_callback didn't force the SIGSTOP out of the LWP
(leaving immediately with LWP->signalled set, without issuing
a PTRACE_CONT), it would still be problematic to leave this
syscall enter pending, as later when the thread is resumed,
it would then see the same syscall exit mentioned above,
followed by the delayed SIGSTOP, while the syscall didn't
actually get to execute. It seems it would be even more
confusing to the user. */
linux_nat_debug_printf
("ignoring syscall %d for LWP %ld (stopping threads), resuming with "
"PTRACE_CONT for SIGSTOP", syscall_number, lp->ptid.lwp ());
lp->syscall_state = TARGET_WAITKIND_IGNORE;
ptrace (PTRACE_CONT, lp->ptid.lwp (), 0, 0);
lp->stopped = 0;
return 1;
}
/* Always update the entry/return state, even if this particular
syscall isn't interesting to the core now. In async mode,
the user could install a new catchpoint for this syscall
between syscall enter/return, and we'll need to know to
report a syscall return if that happens. */
lp->syscall_state = (lp->syscall_state == TARGET_WAITKIND_SYSCALL_ENTRY
? TARGET_WAITKIND_SYSCALL_RETURN
: TARGET_WAITKIND_SYSCALL_ENTRY);
if (catch_syscall_enabled ())
{
if (catching_syscall_number (syscall_number))
{
/* Alright, an event to report. */
ourstatus->kind = lp->syscall_state;
ourstatus->value.syscall_number = syscall_number;
linux_nat_debug_printf
("stopping for %s of syscall %d for LWP %ld",
(lp->syscall_state == TARGET_WAITKIND_SYSCALL_ENTRY
? "entry" : "return"), syscall_number, lp->ptid.lwp ());
return 0;
}
linux_nat_debug_printf
("ignoring %s of syscall %d for LWP %ld",
(lp->syscall_state == TARGET_WAITKIND_SYSCALL_ENTRY
? "entry" : "return"), syscall_number, lp->ptid.lwp ());
}
else
{
/* If we had been syscall tracing, and hence used PT_SYSCALL
before on this LWP, it could happen that the user removes all
syscall catchpoints before we get to process this event.
There are two noteworthy issues here:
- When stopped at a syscall entry event, resuming with
PT_STEP still resumes executing the syscall and reports a
syscall return.
- Only PT_SYSCALL catches syscall enters. If we last
single-stepped this thread, then this event can't be a
syscall enter. If we last single-stepped this thread, this
has to be a syscall exit.
The points above mean that the next resume, be it PT_STEP or
PT_CONTINUE, can not trigger a syscall trace event. */
linux_nat_debug_printf
("caught syscall event with no syscall catchpoints. %d for LWP %ld, "
"ignoring", syscall_number, lp->ptid.lwp ());
lp->syscall_state = TARGET_WAITKIND_IGNORE;
}
/* The core isn't interested in this event. For efficiency, avoid
stopping all threads only to have the core resume them all again.
Since we're not stopping threads, if we're still syscall tracing
and not stepping, we can't use PTRACE_CONT here, as we'd miss any
subsequent syscall. Simply resume using the inf-ptrace layer,
which knows when to use PT_SYSCALL or PT_CONTINUE. */
linux_resume_one_lwp (lp, lp->step, GDB_SIGNAL_0);
return 1;
}
/* Handle a GNU/Linux extended wait response. If we see a clone
event, we need to add the new LWP to our list (and not report the
trap to higher layers). This function returns non-zero if the
event should be ignored and we should wait again. If STOPPING is
true, the new LWP remains stopped, otherwise it is continued. */
static int
linux_handle_extended_wait (struct lwp_info *lp, int status)
{
int pid = lp->ptid.lwp ();
struct target_waitstatus *ourstatus = &lp->waitstatus;
int event = linux_ptrace_get_extended_event (status);
/* 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. */
lp->syscall_state = TARGET_WAITKIND_SYSCALL_ENTRY;
if (event == PTRACE_EVENT_FORK || event == PTRACE_EVENT_VFORK
|| event == PTRACE_EVENT_CLONE)
{
unsigned long new_pid;
int ret;
ptrace (PTRACE_GETEVENTMSG, pid, 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)
internal_error (__FILE__, __LINE__,
_("wait returned unexpected PID %d"), ret);
else if (!WIFSTOPPED (status))
internal_error (__FILE__, __LINE__,
_("wait returned unexpected status 0x%x"), status);
}
ourstatus->value.related_pid = ptid_t (new_pid, new_pid, 0);
if (event == PTRACE_EVENT_FORK || event == PTRACE_EVENT_VFORK)
{
/* The arch-specific native code may need to know about new
forks even if those end up never mapped to an
inferior. */
linux_target->low_new_fork (lp, new_pid);
}
else if (event == PTRACE_EVENT_CLONE)
{
linux_target->low_new_clone (lp, new_pid);
}
if (event == PTRACE_EVENT_FORK
&& linux_fork_checkpointing_p (lp->ptid.pid ()))
{
/* Handle checkpointing by linux-fork.c here as a special
case. We don't want the follow-fork-mode or 'catch fork'
to interfere with this. */
/* This won't actually modify the breakpoint list, but will
physically remove the breakpoints from the child. */
detach_breakpoints (ptid_t (new_pid, new_pid, 0));
/* Retain child fork in ptrace (stopped) state. */
if (!find_fork_pid (new_pid))
add_fork (new_pid);
/* Report as spurious, so that infrun doesn't want to follow
this fork. We're actually doing an infcall in
linux-fork.c. */
ourstatus->kind = TARGET_WAITKIND_SPURIOUS;
/* Report the stop to the core. */
return 0;
}
if (event == PTRACE_EVENT_FORK)
ourstatus->kind = TARGET_WAITKIND_FORKED;
else if (event == PTRACE_EVENT_VFORK)
ourstatus->kind = TARGET_WAITKIND_VFORKED;
else if (event == PTRACE_EVENT_CLONE)
{
struct lwp_info *new_lp;
ourstatus->kind = TARGET_WAITKIND_IGNORE;
linux_nat_debug_printf
("Got clone event from LWP %d, new child is LWP %ld", pid, new_pid);
new_lp = add_lwp (ptid_t (lp->ptid.pid (), new_pid, 0));
new_lp->stopped = 1;
new_lp->resumed = 1;
/* If the thread_db layer is active, let it record the user
level thread id and status, and add the thread to GDB's
list. */
if (!thread_db_notice_clone (lp->ptid, new_lp->ptid))
{
/* The process is not using thread_db. Add the LWP to
GDB's list. */
target_post_attach (new_lp->ptid.lwp ());
add_thread (linux_target, new_lp->ptid);
}
/* Even if we're stopping the thread for some reason
internal to this module, from the perspective of infrun
and the user/frontend, this new thread is running until
it next reports a stop. */
set_running (linux_target, new_lp->ptid, true);
set_executing (linux_target, new_lp->ptid, true);
if (WSTOPSIG (status) != SIGSTOP)
{
/* This can happen if someone starts sending signals to
the new thread before it gets a chance to run, which
have a lower number than SIGSTOP (e.g. SIGUSR1).
This is an unlikely case, and harder to handle for
fork / vfork than for clone, so we do not try - but
we handle it for clone events here. */
new_lp->signalled = 1;
/* We created NEW_LP so it cannot yet contain STATUS. */
gdb_assert (new_lp->status == 0);
/* Save the wait status to report later. */
linux_nat_debug_printf
("waitpid of new LWP %ld, saving status %s",
(long) new_lp->ptid.lwp (), status_to_str (status).c_str ());
new_lp->status = status;
}
else if (report_thread_events)
{
new_lp->waitstatus.kind = TARGET_WAITKIND_THREAD_CREATED;
new_lp->status = status;
}
return 1;
}
return 0;
}
if (event == PTRACE_EVENT_EXEC)
{
linux_nat_debug_printf ("Got exec event from LWP %ld", lp->ptid.lwp ());
/* Close the /proc/<pid>/mem file if it was open for this
inferior. */
maybe_close_proc_mem_file (lp->ptid.pid ());
ourstatus->kind = TARGET_WAITKIND_EXECD;
ourstatus->value.execd_pathname
= xstrdup (linux_proc_pid_to_exec_file (pid));
/* The thread that execed must have been resumed, but, when a
thread execs, it changes its tid to the tgid, and the old
tgid thread might have not been resumed. */
lp->resumed = 1;
return 0;
}
if (event == PTRACE_EVENT_VFORK_DONE)
{
if (current_inferior ()->waiting_for_vfork_done)
{
linux_nat_debug_printf
("Got expected PTRACE_EVENT_VFORK_DONE from LWP %ld: stopping",
lp->ptid.lwp ());
ourstatus->kind = TARGET_WAITKIND_VFORK_DONE;
return 0;
}
linux_nat_debug_printf
("Got PTRACE_EVENT_VFORK_DONE from LWP %ld: ignoring", lp->ptid.lwp ());
return 1;
}
internal_error (__FILE__, __LINE__,
_("unknown ptrace event %d"), event);
}
/* Suspend waiting for a signal. We're mostly interested in
SIGCHLD/SIGINT. */
static void
wait_for_signal ()
{
linux_nat_debug_printf ("about to sigsuspend");
sigsuspend (&suspend_mask);
/* If the quit flag is set, it means that the user pressed Ctrl-C
and we're debugging a process that is running on a separate
terminal, so we must forward the Ctrl-C to the inferior. (If the
inferior is sharing GDB's terminal, then the Ctrl-C reaches the
inferior directly.) We must do this here because functions that
need to block waiting for a signal loop forever until there's an
event to report before returning back to the event loop. */
if (!target_terminal::is_ours ())
{
if (check_quit_flag ())
target_pass_ctrlc ();
}
}
/* Wait for LP to stop. Returns the wait status, or 0 if the LWP has
exited. */
static int
wait_lwp (struct lwp_info *lp)
{
pid_t pid;
int status = 0;
int thread_dead = 0;
sigset_t prev_mask;
gdb_assert (!lp->stopped);
gdb_assert (lp->status == 0);
/* Make sure SIGCHLD is blocked for sigsuspend avoiding a race below. */
block_child_signals (&prev_mask);
for (;;)
{
pid = my_waitpid (lp->ptid.lwp (), &status, __WALL | WNOHANG);
if (pid == -1 && errno == ECHILD)
{
/* The thread has previously exited. We need to delete it
now because if this was a non-leader thread execing, we
won't get an exit event. See comments on exec events at
the top of the file. */
thread_dead = 1;
linux_nat_debug_printf ("%s vanished.",
target_pid_to_str (lp->ptid).c_str ());
}
if (pid != 0)
break;
/* Bugs 10970, 12702.
Thread group leader may have exited in which case we'll lock up in
waitpid if there are other threads, even if they are all zombies too.
Basically, we're not supposed to use waitpid this way.
tkill(pid,0) cannot be used here as it gets ESRCH for both
for zombie and running processes.
As a workaround, check if we're waiting for the thread group leader and
if it's a zombie, and avoid calling waitpid if it is.
This is racy, what if the tgl becomes a zombie right after we check?
Therefore always use WNOHANG with sigsuspend - it is equivalent to
waiting waitpid but linux_proc_pid_is_zombie is safe this way. */
if (lp->ptid.pid () == lp->ptid.lwp ()
&& linux_proc_pid_is_zombie (lp->ptid.lwp ()))
{
thread_dead = 1;
linux_nat_debug_printf ("Thread group leader %s vanished.",
target_pid_to_str (lp->ptid).c_str ());
break;
}
/* Wait for next SIGCHLD and try again. This may let SIGCHLD handlers
get invoked despite our caller had them intentionally blocked by
block_child_signals. This is sensitive only to the loop of
linux_nat_wait_1 and there if we get called my_waitpid gets called
again before it gets to sigsuspend so we can safely let the handlers
get executed here. */
wait_for_signal ();
}
restore_child_signals_mask (&prev_mask);
if (!thread_dead)
{
gdb_assert (pid == lp->ptid.lwp ());
linux_nat_debug_printf ("waitpid %s received %s",
target_pid_to_str (lp->ptid).c_str (),
status_to_str (status).c_str ());
/* Check if the thread has exited. */
if (WIFEXITED (status) || WIFSIGNALED (status))
{
if (report_thread_events
|| lp->ptid.pid () == lp->ptid.lwp ())
{
linux_nat_debug_printf ("LWP %d exited.", lp->ptid.pid ());
/* If this is the leader exiting, it means the whole
process is gone. Store the status to report to the
core. Store it in lp->waitstatus, because lp->status
would be ambiguous (W_EXITCODE(0,0) == 0). */
store_waitstatus (&lp->waitstatus, status);
return 0;
}
thread_dead = 1;
linux_nat_debug_printf ("%s exited.",
target_pid_to_str (lp->ptid).c_str ());
}
}
if (thread_dead)
{
exit_lwp (lp);
return 0;
}
gdb_assert (WIFSTOPPED (status));
lp->stopped = 1;
if (lp->must_set_ptrace_flags)
{
inferior *inf = find_inferior_pid (linux_target, lp->ptid.pid ());
int options = linux_nat_ptrace_options (inf->attach_flag);
linux_enable_event_reporting (lp->ptid.lwp (), options);
lp->must_set_ptrace_flags = 0;
}
/* Handle GNU/Linux's syscall SIGTRAPs. */
if (WIFSTOPPED (status) && WSTOPSIG (status) == SYSCALL_SIGTRAP)
{
/* No longer need the sysgood bit. The ptrace event ends up
recorded in lp->waitstatus if we care for it. We can carry
on handling the event like a regular SIGTRAP from here
on. */
status = W_STOPCODE (SIGTRAP);
if (linux_handle_syscall_trap (lp, 1))
return wait_lwp (lp);
}
else
{
/* Almost all other ptrace-stops are known to be outside of system
calls, with further exceptions in linux_handle_extended_wait. */
lp->syscall_state = TARGET_WAITKIND_IGNORE;
}
/* Handle GNU/Linux's extended waitstatus for trace events. */
if (WIFSTOPPED (status) && WSTOPSIG (status) == SIGTRAP
&& linux_is_extended_waitstatus (status))
{
linux_nat_debug_printf ("Handling extended status 0x%06x", status);
linux_handle_extended_wait (lp, status);
return 0;
}
return status;
}
/* Send a SIGSTOP to LP. */
static int
stop_callback (struct lwp_info *lp)
{
if (!lp->stopped && !lp->signalled)
{
int ret;
linux_nat_debug_printf ("kill %s **<SIGSTOP>**",
target_pid_to_str (lp->ptid).c_str ());
errno = 0;
ret = kill_lwp (lp->ptid.lwp (), SIGSTOP);
linux_nat_debug_printf ("lwp kill %d %s", ret,
errno ? safe_strerror (errno) : "ERRNO-OK");
lp->signalled = 1;
gdb_assert (lp->status == 0);
}
return 0;
}
/* Request a stop on LWP. */
void
linux_stop_lwp (struct lwp_info *lwp)
{
stop_callback (lwp);
}
/* See linux-nat.h */
void
linux_stop_and_wait_all_lwps (void)
{
/* Stop all LWP's ... */
iterate_over_lwps (minus_one_ptid, stop_callback);
/* ... and wait until all of them have reported back that
they're no longer running. */
iterate_over_lwps (minus_one_ptid, stop_wait_callback);
}
/* See linux-nat.h */
void
linux_unstop_all_lwps (void)
{
iterate_over_lwps (minus_one_ptid,
[] (struct lwp_info *info)
{
return resume_stopped_resumed_lwps (info, minus_one_ptid);
});
}
/* Return non-zero if LWP PID has a pending SIGINT. */
static int
linux_nat_has_pending_sigint (int pid)
{
sigset_t pending, blocked, ignored;
linux_proc_pending_signals (pid, &pending, &blocked, &ignored);
if (sigismember (&pending, SIGINT)
&& !sigismember (&ignored, SIGINT))
return 1;
return 0;
}
/* Set a flag in LP indicating that we should ignore its next SIGINT. */
static int
set_ignore_sigint (struct lwp_info *lp)
{
/* If a thread has a pending SIGINT, consume it; otherwise, set a
flag to consume the next one. */
if (lp->stopped && lp->status != 0 && WIFSTOPPED (lp->status)
&& WSTOPSIG (lp->status) == SIGINT)
lp->status = 0;
else
lp->ignore_sigint = 1;
return 0;
}
/* If LP does not have a SIGINT pending, then clear the ignore_sigint flag.
This function is called after we know the LWP has stopped; if the LWP
stopped before the expected SIGINT was delivered, then it will never have
arrived. Also, if the signal was delivered to a shared queue and consumed
by a different thread, it will never be delivered to this LWP. */
static void
maybe_clear_ignore_sigint (struct lwp_info *lp)
{
if (!lp->ignore_sigint)
return;
if (!linux_nat_has_pending_sigint (lp->ptid.lwp ()))
{
linux_nat_debug_printf ("Clearing bogus flag for %s",
target_pid_to_str (lp->ptid).c_str ());
lp->ignore_sigint = 0;
}
}
/* Fetch the possible triggered data watchpoint info and store it in
LP.
On some archs, like x86, that use debug registers to set
watchpoints, it's possible that the way to know which watched
address trapped, is to check the register that is used to select
which address to watch. Problem is, between setting the watchpoint
and reading back which data address trapped, the user may change
the set of watchpoints, and, as a consequence, GDB changes the
debug registers in the inferior. To avoid reading back a stale
stopped-data-address when that happens, we cache in LP the fact
that a watchpoint trapped, and the corresponding data address, as
soon as we see LP stop with a SIGTRAP. If GDB changes the debug
registers meanwhile, we have the cached data we can rely on. */
static int
check_stopped_by_watchpoint (struct lwp_info *lp)
{
scoped_restore save_inferior_ptid = make_scoped_restore (&inferior_ptid);
inferior_ptid = lp->ptid;
if (linux_target->low_stopped_by_watchpoint ())
{
lp->stop_reason = TARGET_STOPPED_BY_WATCHPOINT;
lp->stopped_data_address_p
= linux_target->low_stopped_data_address (&lp->stopped_data_address);
}
return lp->stop_reason == TARGET_STOPPED_BY_WATCHPOINT;
}
/* Returns true if the LWP had stopped for a watchpoint. */
bool
linux_nat_target::stopped_by_watchpoint ()
{
struct lwp_info *lp = find_lwp_pid (inferior_ptid);
gdb_assert (lp != NULL);
return lp->stop_reason == TARGET_STOPPED_BY_WATCHPOINT;
}
bool
linux_nat_target::stopped_data_address (CORE_ADDR *addr_p)
{
struct lwp_info *lp = find_lwp_pid (inferior_ptid);
gdb_assert (lp != NULL);
*addr_p = lp->stopped_data_address;
return lp->stopped_data_address_p;
}
/* Commonly any breakpoint / watchpoint generate only SIGTRAP. */
bool
linux_nat_target::low_status_is_event (int status)
{
return WIFSTOPPED (status) && WSTOPSIG (status) == SIGTRAP;
}
/* Wait until LP is stopped. */
static int
stop_wait_callback (struct lwp_info *lp)
{
inferior *inf = find_inferior_ptid (linux_target, lp->ptid);
/* If this is a vfork parent, bail out, it is not going to report
any SIGSTOP until the vfork is done with. */
if (inf->vfork_child != NULL)
return 0;
if (!lp->stopped)
{
int status;
status = wait_lwp (lp);
if (status == 0)
return 0;
if (lp->ignore_sigint && WIFSTOPPED (status)
&& WSTOPSIG (status) == SIGINT)
{
lp->ignore_sigint = 0;
errno = 0;
ptrace (PTRACE_CONT, lp->ptid.lwp (), 0, 0);
lp->stopped = 0;
linux_nat_debug_printf
("PTRACE_CONT %s, 0, 0 (%s) (discarding SIGINT)",
target_pid_to_str (lp->ptid).c_str (),
errno ? safe_strerror (errno) : "OK");
return stop_wait_callback (lp);
}
maybe_clear_ignore_sigint (lp);
if (WSTOPSIG (status) != SIGSTOP)
{
/* The thread was stopped with a signal other than SIGSTOP. */
linux_nat_debug_printf ("Pending event %s in %s",
status_to_str ((int) status).c_str (),
target_pid_to_str (lp->ptid).c_str ());
/* Save the sigtrap event. */
lp->status = status;
gdb_assert (lp->signalled);
save_stop_reason (lp);
}
else
{
/* We caught the SIGSTOP that we intended to catch. */
linux_nat_debug_printf ("Expected SIGSTOP caught for %s.",
target_pid_to_str (lp->ptid).c_str ());
lp->signalled = 0;
/* If we are waiting for this stop so we can report the thread
stopped then we need to record this status. Otherwise, we can
now discard this stop event. */
if (lp->last_resume_kind == resume_stop)
{
lp->status = status;
save_stop_reason (lp);
}
}
}
return 0;
}
/* Return non-zero if LP has a wait status pending. Discard the
pending event and resume the LWP if the event that originally
caused the stop became uninteresting. */
static int
status_callback (struct lwp_info *lp)
{
/* Only report a pending wait status if we pretend that this has
indeed been resumed. */
if (!lp->resumed)
return 0;
if (!lwp_status_pending_p (lp))
return 0;
if (lp->stop_reason == TARGET_STOPPED_BY_SW_BREAKPOINT
|| lp->stop_reason == TARGET_STOPPED_BY_HW_BREAKPOINT)
{
struct regcache *regcache = get_thread_regcache (linux_target, lp->ptid);
CORE_ADDR pc;
int discard = 0;
pc = regcache_read_pc (regcache);
if (pc != lp->stop_pc)
{
linux_nat_debug_printf ("PC of %s changed. was=%s, now=%s",
target_pid_to_str (lp->ptid).c_str (),
paddress (target_gdbarch (), lp->stop_pc),
paddress (target_gdbarch (), pc));
discard = 1;
}
#if !USE_SIGTRAP_SIGINFO
else if (!breakpoint_inserted_here_p (regcache->aspace (), pc))
{
linux_nat_debug_printf ("previous breakpoint of %s, at %s gone",
target_pid_to_str (lp->ptid).c_str (),
paddress (target_gdbarch (), lp->stop_pc));
discard = 1;
}
#endif
if (discard)
{
linux_nat_debug_printf ("pending event of %s cancelled.",
target_pid_to_str (lp->ptid).c_str ());
lp->status = 0;
linux_resume_one_lwp (lp, lp->step, GDB_SIGNAL_0);
return 0;
}
}
return 1;
}
/* Count the LWP's that have had events. */
static int
count_events_callback (struct lwp_info *lp, int *count)
{
gdb_assert (count != NULL);
/* Select only resumed LWPs that have an event pending. */
if (lp->resumed && lwp_status_pending_p (lp))
(*count)++;
return 0;
}
/* Select the LWP (if any) that is currently being single-stepped. */
static int
select_singlestep_lwp_callback (struct lwp_info *lp)
{
if (lp->last_resume_kind == resume_step
&& lp->status != 0)
return 1;
else
return 0;
}
/* Returns true if LP has a status pending. */
static int
lwp_status_pending_p (struct lwp_info *lp)
{
/* We check for lp->waitstatus in addition to lp->status, because we
can have pending process exits recorded in lp->status and
W_EXITCODE(0,0) happens to be 0. */
return lp->status != 0 || lp->waitstatus.kind != TARGET_WAITKIND_IGNORE;
}
/* Select the Nth LWP that has had an event. */
static int
select_event_lwp_callback (struct lwp_info *lp, int *selector)
{
gdb_assert (selector != NULL);
/* Select only resumed LWPs that have an event pending. */
if (lp->resumed && lwp_status_pending_p (lp))
if ((*selector)-- == 0)
return 1;
return 0;
}
/* Called when the LWP stopped for a signal/trap. If it stopped for a
trap check what caused it (breakpoint, watchpoint, trace, etc.),
and save the result in the LWP's stop_reason field. If it stopped
for a breakpoint, decrement the PC if necessary on the lwp's
architecture. */
static void
save_stop_reason (struct lwp_info *lp)
{
struct regcache *regcache;
struct gdbarch *gdbarch;
CORE_ADDR pc;
CORE_ADDR sw_bp_pc;
#if USE_SIGTRAP_SIGINFO
siginfo_t siginfo;
#endif
gdb_assert (lp->stop_reason == TARGET_STOPPED_BY_NO_REASON);
gdb_assert (lp->status != 0);
if (!linux_target->low_status_is_event (lp->status))
return;
regcache = get_thread_regcache (linux_target, lp->ptid);
gdbarch = regcache->arch ();
pc = regcache_read_pc (regcache);
sw_bp_pc = pc - gdbarch_decr_pc_after_break (gdbarch);
#if USE_SIGTRAP_SIGINFO
if (linux_nat_get_siginfo (lp->ptid, &siginfo))
{
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 (lp))
lp->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. */
lp->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 (lp))
lp->stop_reason = TARGET_STOPPED_BY_HW_BREAKPOINT;
}
else if (siginfo.si_code == TRAP_TRACE)
{
linux_nat_debug_printf ("%s stopped by trace",
target_pid_to_str (lp->ptid).c_str ());
/* 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. */
check_stopped_by_watchpoint (lp);
}
}
}
#else
if ((!lp->step || lp->stop_pc == sw_bp_pc)
&& software_breakpoint_inserted_here_p (regcache->aspace (),
sw_bp_pc))
{
/* The LWP was either continued, or stepped a software
breakpoint instruction. */
lp->stop_reason = TARGET_STOPPED_BY_SW_BREAKPOINT;
}
if (hardware_breakpoint_inserted_here_p (regcache->aspace (), pc))
lp->stop_reason = TARGET_STOPPED_BY_HW_BREAKPOINT;
if (lp->stop_reason == TARGET_STOPPED_BY_NO_REASON)
check_stopped_by_watchpoint (lp);
#endif
if (lp->stop_reason == TARGET_STOPPED_BY_SW_BREAKPOINT)
{
linux_nat_debug_printf ("%s stopped by software breakpoint",
target_pid_to_str (lp->ptid).c_str ());
/* Back up the PC if necessary. */
if (pc != sw_bp_pc)
regcache_write_pc (regcache, sw_bp_pc);
/* Update this so we record the correct stop PC below. */
pc = sw_bp_pc;
}
else if (lp->stop_reason == TARGET_STOPPED_BY_HW_BREAKPOINT)
{
linux_nat_debug_printf ("%s stopped by hardware breakpoint",
target_pid_to_str (lp->ptid).c_str ());
}
else if (lp->stop_reason == TARGET_STOPPED_BY_WATCHPOINT)
{
linux_nat_debug_printf ("%s stopped by hardware watchpoint",
target_pid_to_str (lp->ptid).c_str ());
}
lp->stop_pc = pc;
}
/* Returns true if the LWP had stopped for a software breakpoint. */
bool
linux_nat_target::stopped_by_sw_breakpoint ()
{
struct lwp_info *lp = find_lwp_pid (inferior_ptid);
gdb_assert (lp != NULL);
return lp->stop_reason == TARGET_STOPPED_BY_SW_BREAKPOINT;
}
/* Implement the supports_stopped_by_sw_breakpoint method. */
bool
linux_nat_target::supports_stopped_by_sw_breakpoint ()
{
return USE_SIGTRAP_SIGINFO;
}
/* Returns true if the LWP had stopped for a hardware
breakpoint/watchpoint. */
bool
linux_nat_target::stopped_by_hw_breakpoint ()
{
struct lwp_info *lp = find_lwp_pid (inferior_ptid);
gdb_assert (lp != NULL);
return lp->stop_reason == TARGET_STOPPED_BY_HW_BREAKPOINT;
}
/* Implement the supports_stopped_by_hw_breakpoint method. */
bool
linux_nat_target::supports_stopped_by_hw_breakpoint ()
{
return USE_SIGTRAP_SIGINFO;
}
/* Select one LWP out of those that have events pending. */
static void
select_event_lwp (ptid_t filter, struct lwp_info **orig_lp, int *status)
{
int num_events = 0;
int random_selector;
struct lwp_info *event_lp = NULL;
/* Record the wait status for the original LWP. */
(*orig_lp)->status = *status;
/* In all-stop, give preference to the LWP that is being
single-stepped. There will be at most one, and it will be 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, as
otherwise we'd report the pending SIGTRAP then, 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 (!target_is_non_stop_p ())
{
event_lp = iterate_over_lwps (filter, select_singlestep_lwp_callback);
if (event_lp != NULL)
{
linux_nat_debug_printf ("Select single-step %s",
target_pid_to_str (event_lp->ptid).c_str ());
}
}
if (event_lp == NULL)
{
/* Pick one at random, out of those which have had events. */
/* First see how many events we have. */
iterate_over_lwps (filter,
[&] (struct lwp_info *info)
{
return count_events_callback (info, &num_events);
});
gdb_assert (num_events > 0);
/* Now randomly pick a LWP out of those that have had
events. */
random_selector = (int)
((num_events * (double) rand ()) / (RAND_MAX + 1.0));
if (num_events > 1)
linux_nat_debug_printf ("Found %d events, selecting #%d",
num_events, random_selector);
event_lp
= (iterate_over_lwps
(filter,
[&] (struct lwp_info *info)
{
return select_event_lwp_callback (info,
&random_selector);
}));
}
if (event_lp != NULL)
{
/* Switch the event LWP. */
*orig_lp = event_lp;
*status = event_lp->status;
}
/* Flush the wait status for the event LWP. */
(*orig_lp)->status = 0;
}
/* Return non-zero if LP has been resumed. */
static int
resumed_callback (struct lwp_info *lp)
{
return lp->resumed;
}
/* Check if we should go on and pass this event to common code.
If so, save the status to the lwp_info structure associated to LWPID. */
static void
linux_nat_filter_event (int lwpid, int status)
{
struct lwp_info *lp;
int event = linux_ptrace_get_extended_event (status);
lp = 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. The non-leader
thread changes its tid to the tgid. */
if (WIFSTOPPED (status) && lp == NULL
&& (WSTOPSIG (status) == SIGTRAP && event == PTRACE_EVENT_EXEC))
{
/* A multi-thread exec after we had seen the leader exiting. */
linux_nat_debug_printf ("Re-adding thread group leader LWP %d.", lwpid);
lp = add_lwp (ptid_t (lwpid, lwpid, 0));
lp->stopped = 1;
lp->resumed = 1;
add_thread (linux_target, lp->ptid);
}
if (WIFSTOPPED (status) && !lp)
{
linux_nat_debug_printf ("saving LWP %ld status %s in stopped_pids list",
(long) lwpid, status_to_str (status).c_str ());
add_to_pid_list (&stopped_pids, lwpid, status);
return;
}
/* Make sure we don't report an event for the exit of an LWP not in
our list, i.e. not part of the current process. This can happen
if we detach from a program we originally forked and then it
exits. */
if (!WIFSTOPPED (status) && !lp)
return;
/* This LWP is stopped now. (And if dead, this prevents it from
ever being continued.) */
lp->stopped = 1;
if (WIFSTOPPED (status) && lp->must_set_ptrace_flags)
{
inferior *inf = find_inferior_pid (linux_target, lp->ptid.pid ());
int options = linux_nat_ptrace_options (inf->attach_flag);
linux_enable_event_reporting (lp->ptid.lwp (), options);
lp->must_set_ptrace_flags = 0;
}
/* Handle GNU/Linux's syscall SIGTRAPs. */
if (WIFSTOPPED (status) && WSTOPSIG (status) == SYSCALL_SIGTRAP)
{
/* No longer need the sysgood bit. The ptrace event ends up
recorded in lp->waitstatus if we care for it. We can carry
on handling the event like a regular SIGTRAP from here
on. */
status = W_STOPCODE (SIGTRAP);
if (linux_handle_syscall_trap (lp, 0))
return;
}
else
{
/* Almost all other ptrace-stops are known to be outside of system
calls, with further exceptions in linux_handle_extended_wait. */
lp->syscall_state = TARGET_WAITKIND_IGNORE;
}
/* Handle GNU/Linux's extended waitstatus for trace events. */
if (WIFSTOPPED (status) && WSTOPSIG (status) == SIGTRAP
&& linux_is_extended_waitstatus (status))
{
linux_nat_debug_printf ("Handling extended status 0x%06x", status);
if (linux_handle_extended_wait (lp, status))
return;
}
/* Check if the thread has exited. */
if (WIFEXITED (status) || WIFSIGNALED (status))
{
if (!report_thread_events
&& num_lwps (lp->ptid.pid ()) > 1)
{
linux_nat_debug_printf ("%s exited.",
target_pid_to_str (lp->ptid).c_str ());
/* If there is at least one more LWP, then the exit signal
was not the end of the debugged application and should be
ignored. */
exit_lwp (lp);
return;
}
/* Note that even if the leader was ptrace-stopped, it can still
exit, if e.g., some other thread brings down the whole
process (calls `exit'). So don't assert that the lwp is
resumed. */
linux_nat_debug_printf ("LWP %ld exited (resumed=%d)",
lp->ptid.lwp (), lp->resumed);
/* Dead LWP's aren't expected to reported a pending sigstop. */
lp->signalled = 0;
/* Store the pending event in the waitstatus, because
W_EXITCODE(0,0) == 0. */
store_waitstatus (&lp->waitstatus, status);
return;
}
/* Make sure we don't report a SIGSTOP that we sent ourselves in
an attempt to stop an LWP. */
if (lp->signalled
&& WIFSTOPPED (status) && WSTOPSIG (status) == SIGSTOP)
{
lp->signalled = 0;
if (lp->last_resume_kind == resume_stop)
{
linux_nat_debug_printf ("resume_stop SIGSTOP caught for %s.",
target_pid_to_str (lp->ptid).c_str ());
}
else
{
/* This is a delayed SIGSTOP. Filter out the event. */
linux_nat_debug_printf
("%s %s, 0, 0 (discard delayed SIGSTOP)",
lp->step ? "PTRACE_SINGLESTEP" : "PTRACE_CONT",
target_pid_to_str (lp->ptid).c_str ());
linux_resume_one_lwp (lp, lp->step, GDB_SIGNAL_0);
gdb_assert (lp->resumed);
return;
}
}
/* Make sure we don't report a SIGINT that we have already displayed
for another thread. */
if (lp->ignore_sigint
&& WIFSTOPPED (status) && WSTOPSIG (status) == SIGINT)
{
linux_nat_debug_printf ("Delayed SIGINT caught for %s.",
target_pid_to_str (lp->ptid).c_str ());
/* This is a delayed SIGINT. */
lp->ignore_sigint = 0;
linux_resume_one_lwp (lp, lp->step, GDB_SIGNAL_0);
linux_nat_debug_printf ("%s %s, 0, 0 (discard SIGINT)",
lp->step ? "PTRACE_SINGLESTEP" : "PTRACE_CONT",
target_pid_to_str (lp->ptid).c_str ());
gdb_assert (lp->resumed);
/* Discard the event. */
return;
}
/* Don't report signals that GDB isn't interested in, such as
signals that are neither printed nor stopped upon. Stopping all
threads can be a bit time-consuming, so if we want decent
performance with heavily multi-threaded programs, especially when
they're using a high frequency timer, we'd better avoid it if we
can. */
if (WIFSTOPPED (status))
{
enum gdb_signal signo = gdb_signal_from_host (WSTOPSIG (status));
if (!target_is_non_stop_p ())
{
/* Only do the below in all-stop, as we currently use SIGSTOP
to implement target_stop (see linux_nat_stop) in
non-stop. */
if (signo == GDB_SIGNAL_INT && signal_pass_state (signo) == 0)
{
/* If ^C/BREAK is typed at the tty/console, SIGINT gets
forwarded to the entire process group, that is, all LWPs
will receive it - unless they're using CLONE_THREAD to
share signals. Since we only want to report it once, we
mark it as ignored for all LWPs except this one. */
iterate_over_lwps (ptid_t (lp->ptid.pid ()), set_ignore_sigint);
lp->ignore_sigint = 0;
}
else
maybe_clear_ignore_sigint (lp);
}
/* When using hardware single-step, we need to report every signal.
Otherwise, signals in pass_mask may be short-circuited
except signals that might be caused by a breakpoint, or SIGSTOP
if we sent the SIGSTOP and are waiting for it to arrive. */
if (!lp->step
&& WSTOPSIG (status) && sigismember (&pass_mask, WSTOPSIG (status))
&& (WSTOPSIG (status) != SIGSTOP
|| !find_thread_ptid (linux_target, lp->ptid)->stop_requested)
&& !linux_wstatus_maybe_breakpoint (status))
{
linux_resume_one_lwp (lp, lp->step, signo);
linux_nat_debug_printf
("%s %s, %s (preempt 'handle')",
lp->step ? "PTRACE_SINGLESTEP" : "PTRACE_CONT",
target_pid_to_str (lp->ptid).c_str (),
(signo != GDB_SIGNAL_0
? strsignal (gdb_signal_to_host (signo)) : "0"));
return;
}
}
/* An interesting event. */
gdb_assert (lp);
lp->status = status;
save_stop_reason (lp);
}
/* Detect zombie thread group leaders, and "exit" them. We can't reap
their exits until all other threads in the group have exited. */
static void
check_zombie_leaders (