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binutils-gdb/gdb/linux-nat.c
Andrew Cagney 155bd5d1c1 Index: ChangeLog 
2006-11-20  Andrew Cagney  <cagney@redhat.com>

	* linux-nat.h: Refer to GNU/Linux or Linux kernel.
	* linux-nat.c (lin_lwp_attach_lwp, linux_nat_thread_alive): Ditto.
	* infcmd.c (attach_command): Ditto.
	* hppa-linux-tdep.c (hppa_linux_regset): Ditto.
	* mn10300-linux-tdep.c: Ditto.  Update copyright year.
	* frv-linux-tdep.c: Ditto.  Update copyright year.
2006-11-20 21:47:06 +00:00

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/* GNU/Linux native-dependent code common to multiple platforms.
Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006
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 2 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, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor,
Boston, MA 02110-1301, USA. */
#include "defs.h"
#include "inferior.h"
#include "target.h"
#include "gdb_string.h"
#include "gdb_wait.h"
#include "gdb_assert.h"
#ifdef HAVE_TKILL_SYSCALL
#include <unistd.h>
#include <sys/syscall.h>
#endif
#include <sys/ptrace.h>
#include "linux-nat.h"
#include "linux-fork.h"
#include "gdbthread.h"
#include "gdbcmd.h"
#include "regcache.h"
#include "regset.h"
#include "inf-ptrace.h"
#include "auxv.h"
#include <sys/param.h> /* for MAXPATHLEN */
#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 "gdbthread.h" /* for struct thread_info etc. */
#include "gdb_stat.h" /* for struct stat */
#include <fcntl.h> /* for O_RDONLY */
#ifndef O_LARGEFILE
#define O_LARGEFILE 0
#endif
/* If the system headers did not provide the constants, hard-code the normal
values. */
#ifndef PTRACE_EVENT_FORK
#define PTRACE_SETOPTIONS 0x4200
#define PTRACE_GETEVENTMSG 0x4201
/* options set using PTRACE_SETOPTIONS */
#define PTRACE_O_TRACESYSGOOD 0x00000001
#define PTRACE_O_TRACEFORK 0x00000002
#define PTRACE_O_TRACEVFORK 0x00000004
#define PTRACE_O_TRACECLONE 0x00000008
#define PTRACE_O_TRACEEXEC 0x00000010
#define PTRACE_O_TRACEVFORKDONE 0x00000020
#define PTRACE_O_TRACEEXIT 0x00000040
/* Wait extended result codes for the above trace options. */
#define PTRACE_EVENT_FORK 1
#define PTRACE_EVENT_VFORK 2
#define PTRACE_EVENT_CLONE 3
#define PTRACE_EVENT_EXEC 4
#define PTRACE_EVENT_VFORK_DONE 5
#define PTRACE_EVENT_EXIT 6
#endif /* PTRACE_EVENT_FORK */
/* We can't always assume that this flag is available, but all systems
with the ptrace event handlers also have __WALL, so it's safe to use
here. */
#ifndef __WALL
#define __WALL 0x40000000 /* Wait for any child. */
#endif
/* The single-threaded native GNU/Linux target_ops. We save a pointer for
the use of the multi-threaded target. */
static struct target_ops *linux_ops;
static struct target_ops linux_ops_saved;
/* The saved to_xfer_partial method, inherited from inf-ptrace.c.
Called by our to_xfer_partial. */
static LONGEST (*super_xfer_partial) (struct target_ops *,
enum target_object,
const char *, gdb_byte *,
const gdb_byte *,
ULONGEST, LONGEST);
static 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);
}
static int linux_parent_pid;
struct simple_pid_list
{
int pid;
struct simple_pid_list *next;
};
struct simple_pid_list *stopped_pids;
/* This variable is a tri-state flag: -1 for unknown, 0 if PTRACE_O_TRACEFORK
can not be used, 1 if it can. */
static int linux_supports_tracefork_flag = -1;
/* If we have PTRACE_O_TRACEFORK, this flag indicates whether we also have
PTRACE_O_TRACEVFORKDONE. */
static int linux_supports_tracevforkdone_flag = -1;
/* 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)
{
struct simple_pid_list *new_pid = xmalloc (sizeof (struct simple_pid_list));
new_pid->pid = pid;
new_pid->next = *listp;
*listp = new_pid;
}
static int
pull_pid_from_list (struct simple_pid_list **listp, int pid)
{
struct simple_pid_list **p;
for (p = listp; *p != NULL; p = &(*p)->next)
if ((*p)->pid == pid)
{
struct simple_pid_list *next = (*p)->next;
xfree (*p);
*p = next;
return 1;
}
return 0;
}
void
linux_record_stopped_pid (int pid)
{
add_to_pid_list (&stopped_pids, pid);
}
/* A helper function for linux_test_for_tracefork, called after fork (). */
static void
linux_tracefork_child (void)
{
int ret;
ptrace (PTRACE_TRACEME, 0, 0, 0);
kill (getpid (), SIGSTOP);
fork ();
_exit (0);
}
/* Wrapper function for waitpid which handles EINTR. */
static int
my_waitpid (int pid, int *status, int flags)
{
int ret;
do
{
ret = waitpid (pid, status, flags);
}
while (ret == -1 && errno == EINTR);
return ret;
}
/* Determine if PTRACE_O_TRACEFORK can be used to follow fork events.
First, we try to enable fork tracing on ORIGINAL_PID. If this fails,
we know that the feature is not available. This may change the tracing
options for ORIGINAL_PID, but we'll be setting them shortly anyway.
However, if it succeeds, we don't know for sure that the feature is
available; old versions of PTRACE_SETOPTIONS ignored unknown options. We
create a child process, attach to it, use PTRACE_SETOPTIONS to enable
fork tracing, and let it fork. If the process exits, we assume that we
can't use TRACEFORK; if we get the fork notification, and we can extract
the new child's PID, then we assume that we can. */
static void
linux_test_for_tracefork (int original_pid)
{
int child_pid, ret, status;
long second_pid;
linux_supports_tracefork_flag = 0;
linux_supports_tracevforkdone_flag = 0;
ret = ptrace (PTRACE_SETOPTIONS, original_pid, 0, PTRACE_O_TRACEFORK);
if (ret != 0)
return;
child_pid = fork ();
if (child_pid == -1)
perror_with_name (("fork"));
if (child_pid == 0)
linux_tracefork_child ();
ret = my_waitpid (child_pid, &status, 0);
if (ret == -1)
perror_with_name (("waitpid"));
else if (ret != child_pid)
error (_("linux_test_for_tracefork: waitpid: unexpected result %d."), ret);
if (! WIFSTOPPED (status))
error (_("linux_test_for_tracefork: waitpid: unexpected status %d."), status);
ret = ptrace (PTRACE_SETOPTIONS, child_pid, 0, PTRACE_O_TRACEFORK);
if (ret != 0)
{
ret = ptrace (PTRACE_KILL, child_pid, 0, 0);
if (ret != 0)
{
warning (_("linux_test_for_tracefork: failed to kill child"));
return;
}
ret = my_waitpid (child_pid, &status, 0);
if (ret != child_pid)
warning (_("linux_test_for_tracefork: failed to wait for killed child"));
else if (!WIFSIGNALED (status))
warning (_("linux_test_for_tracefork: unexpected wait status 0x%x from "
"killed child"), status);
return;
}
/* Check whether PTRACE_O_TRACEVFORKDONE is available. */
ret = ptrace (PTRACE_SETOPTIONS, child_pid, 0,
PTRACE_O_TRACEFORK | PTRACE_O_TRACEVFORKDONE);
linux_supports_tracevforkdone_flag = (ret == 0);
ret = ptrace (PTRACE_CONT, child_pid, 0, 0);
if (ret != 0)
warning (_("linux_test_for_tracefork: failed to resume child"));
ret = my_waitpid (child_pid, &status, 0);
if (ret == child_pid && WIFSTOPPED (status)
&& status >> 16 == PTRACE_EVENT_FORK)
{
second_pid = 0;
ret = ptrace (PTRACE_GETEVENTMSG, child_pid, 0, &second_pid);
if (ret == 0 && second_pid != 0)
{
int second_status;
linux_supports_tracefork_flag = 1;
my_waitpid (second_pid, &second_status, 0);
ret = ptrace (PTRACE_KILL, second_pid, 0, 0);
if (ret != 0)
warning (_("linux_test_for_tracefork: failed to kill second child"));
my_waitpid (second_pid, &status, 0);
}
}
else
warning (_("linux_test_for_tracefork: unexpected result from waitpid "
"(%d, status 0x%x)"), ret, status);
ret = ptrace (PTRACE_KILL, child_pid, 0, 0);
if (ret != 0)
warning (_("linux_test_for_tracefork: failed to kill child"));
my_waitpid (child_pid, &status, 0);
}
/* Return non-zero iff we have tracefork functionality available.
This function also sets linux_supports_tracefork_flag. */
static int
linux_supports_tracefork (int pid)
{
if (linux_supports_tracefork_flag == -1)
linux_test_for_tracefork (pid);
return linux_supports_tracefork_flag;
}
static int
linux_supports_tracevforkdone (int pid)
{
if (linux_supports_tracefork_flag == -1)
linux_test_for_tracefork (pid);
return linux_supports_tracevforkdone_flag;
}
void
linux_enable_event_reporting (ptid_t ptid)
{
int pid = ptid_get_lwp (ptid);
int options;
if (pid == 0)
pid = ptid_get_pid (ptid);
if (! linux_supports_tracefork (pid))
return;
options = PTRACE_O_TRACEFORK | PTRACE_O_TRACEVFORK | PTRACE_O_TRACEEXEC
| PTRACE_O_TRACECLONE;
if (linux_supports_tracevforkdone (pid))
options |= PTRACE_O_TRACEVFORKDONE;
/* Do not enable PTRACE_O_TRACEEXIT until GDB is more prepared to support
read-only process state. */
ptrace (PTRACE_SETOPTIONS, pid, 0, options);
}
void
child_post_attach (int pid)
{
linux_enable_event_reporting (pid_to_ptid (pid));
check_for_thread_db ();
}
static void
linux_child_post_startup_inferior (ptid_t ptid)
{
linux_enable_event_reporting (ptid);
check_for_thread_db ();
}
int
child_follow_fork (struct target_ops *ops, int follow_child)
{
ptid_t last_ptid;
struct target_waitstatus last_status;
int has_vforked;
int parent_pid, child_pid;
get_last_target_status (&last_ptid, &last_status);
has_vforked = (last_status.kind == TARGET_WAITKIND_VFORKED);
parent_pid = ptid_get_lwp (last_ptid);
if (parent_pid == 0)
parent_pid = ptid_get_pid (last_ptid);
child_pid = last_status.value.related_pid;
if (! follow_child)
{
/* We're already attached to the parent, by default. */
/* Before detaching from the child, remove all breakpoints from
it. (This won't actually modify the breakpoint list, but will
physically remove the breakpoints from the child.) */
/* If we vforked this will remove the breakpoints from the parent
also, but they'll be reinserted below. */
detach_breakpoints (child_pid);
/* Detach new forked process? */
if (detach_fork)
{
if (debug_linux_nat)
{
target_terminal_ours ();
fprintf_filtered (gdb_stdlog,
"Detaching after fork from child process %d.\n",
child_pid);
}
ptrace (PTRACE_DETACH, child_pid, 0, 0);
}
else
{
struct fork_info *fp;
/* Retain child fork in ptrace (stopped) state. */
fp = find_fork_pid (child_pid);
if (!fp)
fp = add_fork (child_pid);
fork_save_infrun_state (fp, 0);
}
if (has_vforked)
{
gdb_assert (linux_supports_tracefork_flag >= 0);
if (linux_supports_tracevforkdone (0))
{
int status;
ptrace (PTRACE_CONT, parent_pid, 0, 0);
my_waitpid (parent_pid, &status, __WALL);
if ((status >> 16) != PTRACE_EVENT_VFORK_DONE)
warning (_("Unexpected waitpid result %06x when waiting for "
"vfork-done"), status);
}
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. */
usleep (10000);
}
/* Since we vforked, breakpoints were removed in the parent
too. Put them back. */
reattach_breakpoints (parent_pid);
}
}
else
{
char child_pid_spelling[40];
/* Needed to keep the breakpoint lists in sync. */
if (! has_vforked)
detach_breakpoints (child_pid);
/* Before detaching from the parent, remove all breakpoints from it. */
remove_breakpoints ();
if (debug_linux_nat)
{
target_terminal_ours ();
fprintf_filtered (gdb_stdlog,
"Attaching after fork to child process %d.\n",
child_pid);
}
/* If we're vforking, we may want to hold on to the parent until
the child exits or execs. At exec time we can remove the old
breakpoints from the parent and detach it; at exit time we
could do the same (or even, sneakily, resume debugging it - the
child's exec has failed, or something similar).
This doesn't clean up "properly", because we can't call
target_detach, but that's OK; if the current target is "child",
then it doesn't need any further cleanups, and lin_lwp will
generally not encounter vfork (vfork is defined to fork
in libpthread.so).
The holding part is very easy if we have VFORKDONE events;
but keeping track of both processes is beyond GDB at the
moment. So we don't expose the parent to the rest of GDB.
Instead we quietly hold onto it until such time as we can
safely resume it. */
if (has_vforked)
linux_parent_pid = parent_pid;
else if (!detach_fork)
{
struct fork_info *fp;
/* Retain parent fork in ptrace (stopped) state. */
fp = find_fork_pid (parent_pid);
if (!fp)
fp = add_fork (parent_pid);
fork_save_infrun_state (fp, 0);
}
else
{
target_detach (NULL, 0);
}
inferior_ptid = pid_to_ptid (child_pid);
/* Reinstall ourselves, since we might have been removed in
target_detach (which does other necessary cleanup). */
push_target (ops);
/* Reset breakpoints in the child as appropriate. */
follow_inferior_reset_breakpoints ();
}
return 0;
}
ptid_t
linux_handle_extended_wait (int pid, int status,
struct target_waitstatus *ourstatus)
{
int event = status >> 16;
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))
{
/* 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,
(event == PTRACE_EVENT_CLONE) ? __WCLONE : 0);
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) || WSTOPSIG (status) != SIGSTOP)
internal_error (__FILE__, __LINE__,
_("wait returned unexpected status 0x%x"), status);
}
if (event == PTRACE_EVENT_FORK)
ourstatus->kind = TARGET_WAITKIND_FORKED;
else if (event == PTRACE_EVENT_VFORK)
ourstatus->kind = TARGET_WAITKIND_VFORKED;
else
ourstatus->kind = TARGET_WAITKIND_SPURIOUS;
ourstatus->value.related_pid = new_pid;
return inferior_ptid;
}
if (event == PTRACE_EVENT_EXEC)
{
ourstatus->kind = TARGET_WAITKIND_EXECD;
ourstatus->value.execd_pathname
= xstrdup (child_pid_to_exec_file (pid));
if (linux_parent_pid)
{
detach_breakpoints (linux_parent_pid);
ptrace (PTRACE_DETACH, linux_parent_pid, 0, 0);
linux_parent_pid = 0;
}
return inferior_ptid;
}
internal_error (__FILE__, __LINE__,
_("unknown ptrace event %d"), event);
}
void
child_insert_fork_catchpoint (int pid)
{
if (! linux_supports_tracefork (pid))
error (_("Your system does not support fork catchpoints."));
}
void
child_insert_vfork_catchpoint (int pid)
{
if (!linux_supports_tracefork (pid))
error (_("Your system does not support vfork catchpoints."));
}
void
child_insert_exec_catchpoint (int pid)
{
if (!linux_supports_tracefork (pid))
error (_("Your system does not support exec catchpoints."));
}
/* On GNU/Linux there are no real LWP's. The closest thing to LWP's
are processes sharing the same VM space. A multi-threaded process
is basically a group of such processes. However, such a grouping
is almost entirely a user-space issue; the kernel doesn't enforce
such a grouping at all (this might change in the future). In
general, we'll rely on the threads library (i.e. the GNU/Linux
Threads library) to provide such a grouping.
It is perfectly well possible to write a multi-threaded application
without the assistance of a threads library, by using the clone
system call directly. This module should be able to give some
rudimentary support for debugging such applications if developers
specify the CLONE_PTRACE flag in the clone system call, and are
using the Linux kernel 2.4 or above.
Note that there are some peculiarities in GNU/Linux that affect
this code:
- In general one should specify the __WCLONE flag to waitpid in
order to make it report events for any of the cloned processes
(and leave it out for the initial process). However, if a cloned
process has exited the exit status is only reported if the
__WCLONE flag is absent. Linux kernel 2.4 has a __WALL flag, but
we cannot use it since GDB must work on older systems too.
- When a traced, cloned process exits and is waited for by the
debugger, the kernel reassigns it to the original parent and
keeps it around as a "zombie". Somehow, the GNU/Linux Threads
library doesn't notice this, which leads to the "zombie problem":
When debugged a multi-threaded process that spawns a lot of
threads will run out of processes, even if the threads exit,
because the "zombies" stay around. */
/* List of known LWPs. */
static struct lwp_info *lwp_list;
/* Number of LWPs in the list. */
static int num_lwps;
#define GET_LWP(ptid) ptid_get_lwp (ptid)
#define GET_PID(ptid) ptid_get_pid (ptid)
#define is_lwp(ptid) (GET_LWP (ptid) != 0)
#define BUILD_LWP(lwp, pid) ptid_build (pid, lwp, 0)
/* If the last reported event was a SIGTRAP, this variable is set to
the process id of the LWP/thread that got it. */
ptid_t trap_ptid;
/* Since we cannot wait (in linux_nat_wait) for the initial process and
any cloned processes with a single call to waitpid, we have to use
the WNOHANG flag and call waitpid in a loop. To optimize
things a bit we use `sigsuspend' to wake us up when a process has
something to report (it will send us a SIGCHLD if it has). To make
this work we have to juggle with the signal mask. We save the
original signal mask such that we can restore it before creating a
new process in order to avoid blocking certain signals in the
inferior. We then block SIGCHLD during the waitpid/sigsuspend
loop. */
/* Original signal mask. */
static sigset_t normal_mask;
/* 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;
/* Prototypes for local functions. */
static int stop_wait_callback (struct lwp_info *lp, void *data);
static int linux_nat_thread_alive (ptid_t ptid);
/* Convert wait status STATUS to a string. Used for printing debug
messages only. */
static char *
status_to_str (int status)
{
static char buf[64];
if (WIFSTOPPED (status))
snprintf (buf, sizeof (buf), "%s (stopped)",
strsignal (WSTOPSIG (status)));
else if (WIFSIGNALED (status))
snprintf (buf, sizeof (buf), "%s (terminated)",
strsignal (WSTOPSIG (status)));
else
snprintf (buf, sizeof (buf), "%d (exited)", WEXITSTATUS (status));
return buf;
}
/* Initialize the list of LWPs. Note that this module, contrary to
what GDB's generic threads layer does for its thread list,
re-initializes the LWP lists whenever we mourn or detach (which
doesn't involve mourning) the inferior. */
static void
init_lwp_list (void)
{
struct lwp_info *lp, *lpnext;
for (lp = lwp_list; lp; lp = lpnext)
{
lpnext = lp->next;
xfree (lp);
}
lwp_list = NULL;
num_lwps = 0;
}
/* Add the LWP specified by PID to the list. Return a pointer to the
structure describing the new LWP. */
static struct lwp_info *
add_lwp (ptid_t ptid)
{
struct lwp_info *lp;
gdb_assert (is_lwp (ptid));
lp = (struct lwp_info *) xmalloc (sizeof (struct lwp_info));
memset (lp, 0, sizeof (struct lwp_info));
lp->waitstatus.kind = TARGET_WAITKIND_IGNORE;
lp->ptid = ptid;
lp->next = lwp_list;
lwp_list = lp;
++num_lwps;
return lp;
}
/* Remove the LWP specified by PID from the list. */
static void
delete_lwp (ptid_t ptid)
{
struct lwp_info *lp, *lpprev;
lpprev = NULL;
for (lp = lwp_list; lp; lpprev = lp, lp = lp->next)
if (ptid_equal (lp->ptid, ptid))
break;
if (!lp)
return;
num_lwps--;
if (lpprev)
lpprev->next = lp->next;
else
lwp_list = lp->next;
xfree (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;
if (is_lwp (ptid))
lwp = GET_LWP (ptid);
else
lwp = GET_PID (ptid);
for (lp = lwp_list; lp; lp = lp->next)
if (lwp == GET_LWP (lp->ptid))
return lp;
return NULL;
}
/* Call CALLBACK with its second argument set to DATA for every LWP in
the list. If CALLBACK returns 1 for a particular LWP, return a
pointer to the structure describing that LWP immediately.
Otherwise return NULL. */
struct lwp_info *
iterate_over_lwps (int (*callback) (struct lwp_info *, void *), void *data)
{
struct lwp_info *lp, *lpnext;
for (lp = lwp_list; lp; lp = lpnext)
{
lpnext = lp->next;
if ((*callback) (lp, data))
return lp;
}
return NULL;
}
/* Update our internal state when changing from one fork (checkpoint,
et cetera) 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;
init_lwp_list ();
lp = add_lwp (new_ptid);
lp->stopped = 1;
}
/* Record a PTID for later deletion. */
struct saved_ptids
{
ptid_t ptid;
struct saved_ptids *next;
};
static struct saved_ptids *threads_to_delete;
static void
record_dead_thread (ptid_t ptid)
{
struct saved_ptids *p = xmalloc (sizeof (struct saved_ptids));
p->ptid = ptid;
p->next = threads_to_delete;
threads_to_delete = p;
}
/* Delete any dead threads which are not the current thread. */
static void
prune_lwps (void)
{
struct saved_ptids **p = &threads_to_delete;
while (*p)
if (! ptid_equal ((*p)->ptid, inferior_ptid))
{
struct saved_ptids *tmp = *p;
delete_thread (tmp->ptid);
*p = tmp->next;
xfree (tmp);
}
else
p = &(*p)->next;
}
/* Callback for iterate_over_threads that finds a thread corresponding
to the given LWP. */
static int
find_thread_from_lwp (struct thread_info *thr, void *dummy)
{
ptid_t *ptid_p = dummy;
if (GET_LWP (thr->ptid) && GET_LWP (thr->ptid) == GET_LWP (*ptid_p))
return 1;
else
return 0;
}
/* Handle the exit of a single thread LP. */
static void
exit_lwp (struct lwp_info *lp)
{
if (in_thread_list (lp->ptid))
{
/* Core GDB cannot deal with us deleting the current thread. */
if (!ptid_equal (lp->ptid, inferior_ptid))
delete_thread (lp->ptid);
else
record_dead_thread (lp->ptid);
printf_unfiltered (_("[%s exited]\n"),
target_pid_to_str (lp->ptid));
}
else
{
/* Even if LP->PTID is not in the global GDB thread list, the
LWP may be - with an additional thread ID. We don't need
to print anything in this case; thread_db is in use and
already took care of that. But it didn't delete the thread
in order to handle zombies correctly. */
struct thread_info *thr;
thr = iterate_over_threads (find_thread_from_lwp, &lp->ptid);
if (thr)
{
if (!ptid_equal (thr->ptid, inferior_ptid))
delete_thread (thr->ptid);
else
record_dead_thread (thr->ptid);
}
}
delete_lwp (lp->ptid);
}
/* Attach to the LWP specified by PID. If VERBOSE is non-zero, print
a message telling the user that a new LWP has been added to the
process. */
void
lin_lwp_attach_lwp (ptid_t ptid, int verbose)
{
struct lwp_info *lp, *found_lp;
gdb_assert (is_lwp (ptid));
/* Make sure SIGCHLD is blocked. We don't want SIGCHLD events
to interrupt either the ptrace() or waitpid() calls below. */
if (!sigismember (&blocked_mask, SIGCHLD))
{
sigaddset (&blocked_mask, SIGCHLD);
sigprocmask (SIG_BLOCK, &blocked_mask, NULL);
}
if (verbose)
printf_filtered (_("[New %s]\n"), target_pid_to_str (ptid));
found_lp = lp = find_lwp_pid (ptid);
if (lp == NULL)
lp = add_lwp (ptid);
/* We assume that we're already attached to any LWP that has an id
equal to the overall process id, and to any LWP that is already
in our list of LWPs. If we're not seeing exit events from threads
and we've had PID wraparound since we last tried to stop all threads,
this assumption might be wrong; fortunately, this is very unlikely
to happen. */
if (GET_LWP (ptid) != GET_PID (ptid) && found_lp == NULL)
{
pid_t pid;
int status;
if (ptrace (PTRACE_ATTACH, GET_LWP (ptid), 0, 0) < 0)
error (_("Can't attach %s: %s"), target_pid_to_str (ptid),
safe_strerror (errno));
if (debug_linux_nat)
fprintf_unfiltered (gdb_stdlog,
"LLAL: PTRACE_ATTACH %s, 0, 0 (OK)\n",
target_pid_to_str (ptid));
pid = my_waitpid (GET_LWP (ptid), &status, 0);
if (pid == -1 && errno == ECHILD)
{
/* Try again with __WCLONE to check cloned processes. */
pid = my_waitpid (GET_LWP (ptid), &status, __WCLONE);
lp->cloned = 1;
}
gdb_assert (pid == GET_LWP (ptid)
&& WIFSTOPPED (status) && WSTOPSIG (status));
target_post_attach (pid);
lp->stopped = 1;
if (debug_linux_nat)
{
fprintf_unfiltered (gdb_stdlog,
"LLAL: waitpid %s received %s\n",
target_pid_to_str (ptid),
status_to_str (status));
}
}
else
{
/* We assume that the LWP representing the original process is
already stopped. Mark it as stopped in the data structure
that the GNU/linux ptrace layer uses to keep track of
threads. Note that this won't have already been done since
the main thread will have, we assume, been stopped by an
attach from a different layer. */
lp->stopped = 1;
}
}
static void
linux_nat_attach (char *args, int from_tty)
{
struct lwp_info *lp;
pid_t pid;
int status;
/* FIXME: We should probably accept a list of process id's, and
attach all of them. */
linux_ops->to_attach (args, from_tty);
/* Add the initial process as the first LWP to the list. */
inferior_ptid = BUILD_LWP (GET_PID (inferior_ptid), GET_PID (inferior_ptid));
lp = add_lwp (inferior_ptid);
/* 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. */
pid = my_waitpid (GET_PID (inferior_ptid), &status, 0);
if (pid == -1 && errno == ECHILD)
{
warning (_("%s is a cloned process"), target_pid_to_str (inferior_ptid));
/* Try again with __WCLONE to check cloned processes. */
pid = my_waitpid (GET_PID (inferior_ptid), &status, __WCLONE);
lp->cloned = 1;
}
gdb_assert (pid == GET_PID (inferior_ptid)
&& WIFSTOPPED (status) && WSTOPSIG (status) == SIGSTOP);
lp->stopped = 1;
/* Fake the SIGSTOP that core GDB expects. */
lp->status = W_STOPCODE (SIGSTOP);
lp->resumed = 1;
if (debug_linux_nat)
{
fprintf_unfiltered (gdb_stdlog,
"LLA: waitpid %ld, faking SIGSTOP\n", (long) pid);
}
}
static int
detach_callback (struct lwp_info *lp, void *data)
{
gdb_assert (lp->status == 0 || WIFSTOPPED (lp->status));
if (debug_linux_nat && lp->status)
fprintf_unfiltered (gdb_stdlog, "DC: Pending %s for %s on detach.\n",
strsignal (WSTOPSIG (lp->status)),
target_pid_to_str (lp->ptid));
while (lp->signalled && lp->stopped)
{
errno = 0;
if (ptrace (PTRACE_CONT, GET_LWP (lp->ptid), 0,
WSTOPSIG (lp->status)) < 0)
error (_("Can't continue %s: %s"), target_pid_to_str (lp->ptid),
safe_strerror (errno));
if (debug_linux_nat)
fprintf_unfiltered (gdb_stdlog,
"DC: PTRACE_CONTINUE (%s, 0, %s) (OK)\n",
target_pid_to_str (lp->ptid),
status_to_str (lp->status));
lp->stopped = 0;
lp->signalled = 0;
lp->status = 0;
/* FIXME drow/2003-08-26: There was a call to stop_wait_callback
here. But since lp->signalled was cleared above,
stop_wait_callback didn't do anything; the process was left
running. Shouldn't we be waiting for it to stop?
I've removed the call, since stop_wait_callback now does do
something when called with lp->signalled == 0. */
gdb_assert (lp->status == 0 || WIFSTOPPED (lp->status));
}
/* We don't actually detach from the LWP that has an id equal to the
overall process id just yet. */
if (GET_LWP (lp->ptid) != GET_PID (lp->ptid))
{
errno = 0;
if (ptrace (PTRACE_DETACH, GET_LWP (lp->ptid), 0,
WSTOPSIG (lp->status)) < 0)
error (_("Can't detach %s: %s"), target_pid_to_str (lp->ptid),
safe_strerror (errno));
if (debug_linux_nat)
fprintf_unfiltered (gdb_stdlog,
"PTRACE_DETACH (%s, %s, 0) (OK)\n",
target_pid_to_str (lp->ptid),
strsignal (WSTOPSIG (lp->status)));
delete_lwp (lp->ptid);
}
return 0;
}
static void
linux_nat_detach (char *args, int from_tty)
{
iterate_over_lwps (detach_callback, NULL);
/* Only the initial process should be left right now. */
gdb_assert (num_lwps == 1);
trap_ptid = null_ptid;
/* Destroy LWP info; it's no longer valid. */
init_lwp_list ();
/* Restore the original signal mask. */
sigprocmask (SIG_SETMASK, &normal_mask, NULL);
sigemptyset (&blocked_mask);
inferior_ptid = pid_to_ptid (GET_PID (inferior_ptid));
linux_ops->to_detach (args, from_tty);
}
/* Resume LP. */
static int
resume_callback (struct lwp_info *lp, void *data)
{
if (lp->stopped && lp->status == 0)
{
struct thread_info *tp;
linux_ops->to_resume (pid_to_ptid (GET_LWP (lp->ptid)),
0, TARGET_SIGNAL_0);
if (debug_linux_nat)
fprintf_unfiltered (gdb_stdlog,
"RC: PTRACE_CONT %s, 0, 0 (resume sibling)\n",
target_pid_to_str (lp->ptid));
lp->stopped = 0;
lp->step = 0;
}
return 0;
}
static int
resume_clear_callback (struct lwp_info *lp, void *data)
{
lp->resumed = 0;
return 0;
}
static int
resume_set_callback (struct lwp_info *lp, void *data)
{
lp->resumed = 1;
return 0;
}
static void
linux_nat_resume (ptid_t ptid, int step, enum target_signal signo)
{
struct lwp_info *lp;
int resume_all;
if (debug_linux_nat)
fprintf_unfiltered (gdb_stdlog,
"LLR: Preparing to %s %s, %s, inferior_ptid %s\n",
step ? "step" : "resume",
target_pid_to_str (ptid),
signo ? strsignal (signo) : "0",
target_pid_to_str (inferior_ptid));
prune_lwps ();
/* A specific PTID means `step only this process id'. */
resume_all = (PIDGET (ptid) == -1);
if (resume_all)
iterate_over_lwps (resume_set_callback, NULL);
else
iterate_over_lwps (resume_clear_callback, NULL);
/* If PID is -1, it's the current inferior that should be
handled specially. */
if (PIDGET (ptid) == -1)
ptid = inferior_ptid;
lp = find_lwp_pid (ptid);
if (lp)
{
ptid = pid_to_ptid (GET_LWP (lp->ptid));
/* Remember if we're stepping. */
lp->step = step;
/* Mark this LWP as resumed. */
lp->resumed = 1;
/* 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))
{
int saved_signo = target_signal_from_host (WSTOPSIG (lp->status));
if (signal_stop_state (saved_signo) == 0
&& signal_print_state (saved_signo) == 0
&& signal_pass_state (saved_signo) == 1)
{
if (debug_linux_nat)
fprintf_unfiltered (gdb_stdlog,
"LLR: Not short circuiting for ignored "
"status 0x%x\n", lp->status);
/* FIXME: What should we do if we are supposed to continue
this thread with a signal? */
gdb_assert (signo == TARGET_SIGNAL_0);
signo = saved_signo;
lp->status = 0;
}
}
if (lp->status)
{
/* FIXME: What should we do if we are supposed to continue
this thread with a signal? */
gdb_assert (signo == TARGET_SIGNAL_0);
if (debug_linux_nat)
fprintf_unfiltered (gdb_stdlog,
"LLR: Short circuiting for status 0x%x\n",
lp->status);
return;
}
/* Mark LWP as not stopped to prevent it from being continued by
resume_callback. */
lp->stopped = 0;
}
if (resume_all)
iterate_over_lwps (resume_callback, NULL);
linux_ops->to_resume (ptid, step, signo);
if (debug_linux_nat)
fprintf_unfiltered (gdb_stdlog,
"LLR: %s %s, %s (resume event thread)\n",
step ? "PTRACE_SINGLESTEP" : "PTRACE_CONT",
target_pid_to_str (ptid),
signo ? strsignal (signo) : "0");
}
/* Issue kill to specified lwp. */
static int tkill_failed;
static int
kill_lwp (int lwpid, int signo)
{
errno = 0;
/* Use tkill, if possible, in case we are using nptl threads. If tkill
fails, then we are not using nptl threads and we should be using kill. */
#ifdef HAVE_TKILL_SYSCALL
if (!tkill_failed)
{
int ret = syscall (__NR_tkill, lwpid, signo);
if (errno != ENOSYS)
return ret;
errno = 0;
tkill_failed = 1;
}
#endif
return kill (lwpid, signo);
}
/* Handle a GNU/Linux extended wait response. Most of the work we
just pass off to linux_handle_extended_wait, but if it reports 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_nat_handle_extended (struct lwp_info *lp, int status, int stopping)
{
linux_handle_extended_wait (GET_LWP (lp->ptid), status,
&lp->waitstatus);
/* TARGET_WAITKIND_SPURIOUS is used to indicate clone events. */
if (lp->waitstatus.kind == TARGET_WAITKIND_SPURIOUS)
{
struct lwp_info *new_lp;
new_lp = add_lwp (BUILD_LWP (lp->waitstatus.value.related_pid,
GET_PID (inferior_ptid)));
new_lp->cloned = 1;
if (stopping)
new_lp->stopped = 1;
else
ptrace (PTRACE_CONT, lp->waitstatus.value.related_pid, 0, 0);
lp->waitstatus.kind = TARGET_WAITKIND_IGNORE;
if (debug_linux_nat)
fprintf_unfiltered (gdb_stdlog,
"LLHE: Got clone event from LWP %ld, resuming\n",
GET_LWP (lp->ptid));
ptrace (PTRACE_CONT, GET_LWP (lp->ptid), 0, 0);
return 1;
}
return 0;
}
/* 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;
int thread_dead = 0;
gdb_assert (!lp->stopped);
gdb_assert (lp->status == 0);
pid = my_waitpid (GET_LWP (lp->ptid), &status, 0);
if (pid == -1 && errno == ECHILD)
{
pid = my_waitpid (GET_LWP (lp->ptid), &status, __WCLONE);
if (pid == -1 && errno == ECHILD)
{
/* The thread has previously exited. We need to delete it
now because, for some vendor 2.4 kernels with NPTL
support backported, there won't be an exit event unless
it is the main thread. 2.6 kernels will report an exit
event for each thread that exits, as expected. */
thread_dead = 1;
if (debug_linux_nat)
fprintf_unfiltered (gdb_stdlog, "WL: %s vanished.\n",
target_pid_to_str (lp->ptid));
}
}
if (!thread_dead)
{
gdb_assert (pid == GET_LWP (lp->ptid));
if (debug_linux_nat)
{
fprintf_unfiltered (gdb_stdlog,
"WL: waitpid %s received %s\n",
target_pid_to_str (lp->ptid),
status_to_str (status));
}
}
/* Check if the thread has exited. */
if (WIFEXITED (status) || WIFSIGNALED (status))
{
thread_dead = 1;
if (debug_linux_nat)
fprintf_unfiltered (gdb_stdlog, "WL: %s exited.\n",
target_pid_to_str (lp->ptid));
}
if (thread_dead)
{
exit_lwp (lp);
return 0;
}
gdb_assert (WIFSTOPPED (status));
/* Handle GNU/Linux's extended waitstatus for trace events. */
if (WIFSTOPPED (status) && WSTOPSIG (status) == SIGTRAP && status >> 16 != 0)
{
if (debug_linux_nat)
fprintf_unfiltered (gdb_stdlog,
"WL: Handling extended status 0x%06x\n",
status);
if (linux_nat_handle_extended (lp, status, 1))
return wait_lwp (lp);
}
return status;
}
/* Send a SIGSTOP to LP. */
static int
stop_callback (struct lwp_info *lp, void *data)
{
if (!lp->stopped && !lp->signalled)
{
int ret;
if (debug_linux_nat)
{
fprintf_unfiltered (gdb_stdlog,
"SC: kill %s **<SIGSTOP>**\n",
target_pid_to_str (lp->ptid));
}
errno = 0;
ret = kill_lwp (GET_LWP (lp->ptid), SIGSTOP);
if (debug_linux_nat)
{
fprintf_unfiltered (gdb_stdlog,
"SC: lwp kill %d %s\n",
ret,
errno ? safe_strerror (errno) : "ERRNO-OK");
}
lp->signalled = 1;
gdb_assert (lp->status == 0);
}
return 0;
}
/* Wait until LP is stopped. If DATA is non-null it is interpreted as
a pointer to a set of signals to be flushed immediately. */
static int
stop_wait_callback (struct lwp_info *lp, void *data)
{
sigset_t *flush_mask = data;
if (!lp->stopped)
{
int status;
status = wait_lwp (lp);
if (status == 0)
return 0;
/* Ignore any signals in FLUSH_MASK. */
if (flush_mask && sigismember (flush_mask, WSTOPSIG (status)))
{
if (!lp->signalled)
{
lp->stopped = 1;
return 0;
}
errno = 0;
ptrace (PTRACE_CONT, GET_LWP (lp->ptid), 0, 0);
if (debug_linux_nat)
fprintf_unfiltered (gdb_stdlog,
"PTRACE_CONT %s, 0, 0 (%s)\n",
target_pid_to_str (lp->ptid),
errno ? safe_strerror (errno) : "OK");
return stop_wait_callback (lp, flush_mask);
}
if (WSTOPSIG (status) != SIGSTOP)
{
if (WSTOPSIG (status) == SIGTRAP)
{
/* If a LWP other than the LWP that we're reporting an
event for has hit a GDB breakpoint (as opposed to
some random trap signal), then just arrange for it to
hit it again later. We don't keep the SIGTRAP status
and don't forward the SIGTRAP signal to the LWP. We
will handle the current event, eventually we will
resume all LWPs, and this one will get its breakpoint
trap again.
If we do not do this, then we run the risk that the
user will delete or disable the breakpoint, but the
thread will have already tripped on it. */
/* Now resume this LWP and get the SIGSTOP event. */
errno = 0;
ptrace (PTRACE_CONT, GET_LWP (lp->ptid), 0, 0);
if (debug_linux_nat)
{
fprintf_unfiltered (gdb_stdlog,
"PTRACE_CONT %s, 0, 0 (%s)\n",
target_pid_to_str (lp->ptid),
errno ? safe_strerror (errno) : "OK");
fprintf_unfiltered (gdb_stdlog,
"SWC: Candidate SIGTRAP event in %s\n",
target_pid_to_str (lp->ptid));
}
/* Hold the SIGTRAP for handling by linux_nat_wait. */
stop_wait_callback (lp, data);
/* If there's another event, throw it back into the queue. */
if (lp->status)
{
if (debug_linux_nat)
{
fprintf_unfiltered (gdb_stdlog,
"SWC: kill %s, %s\n",
target_pid_to_str (lp->ptid),
status_to_str ((int) status));
}
kill_lwp (GET_LWP (lp->ptid), WSTOPSIG (lp->status));
}
/* Save the sigtrap event. */
lp->status = status;
return 0;
}
else
{
/* The thread was stopped with a signal other than
SIGSTOP, and didn't accidentally trip a breakpoint. */
if (debug_linux_nat)
{
fprintf_unfiltered (gdb_stdlog,
"SWC: Pending event %s in %s\n",
status_to_str ((int) status),
target_pid_to_str (lp->ptid));
}
/* Now resume this LWP and get the SIGSTOP event. */
errno = 0;
ptrace (PTRACE_CONT, GET_LWP (lp->ptid), 0, 0);
if (debug_linux_nat)
fprintf_unfiltered (gdb_stdlog,
"SWC: PTRACE_CONT %s, 0, 0 (%s)\n",
target_pid_to_str (lp->ptid),
errno ? safe_strerror (errno) : "OK");
/* Hold this event/waitstatus while we check to see if
there are any more (we still want to get that SIGSTOP). */
stop_wait_callback (lp, data);
/* If the lp->status field is still empty, use it to hold
this event. If not, then this event must be returned
to the event queue of the LWP. */
if (lp->status == 0)
lp->status = status;
else
{
if (debug_linux_nat)
{
fprintf_unfiltered (gdb_stdlog,
"SWC: kill %s, %s\n",
target_pid_to_str (lp->ptid),
status_to_str ((int) status));
}
kill_lwp (GET_LWP (lp->ptid), WSTOPSIG (status));
}
return 0;
}
}
else
{
/* We caught the SIGSTOP that we intended to catch, so
there's no SIGSTOP pending. */
lp->stopped = 1;
lp->signalled = 0;
}
}
return 0;
}
/* Check whether PID has any pending signals in FLUSH_MASK. If so set
the appropriate bits in PENDING, and return 1 - otherwise return 0. */
static int
linux_nat_has_pending (int pid, sigset_t *pending, sigset_t *flush_mask)
{
sigset_t blocked, ignored;
int i;
linux_proc_pending_signals (pid, pending, &blocked, &ignored);
if (!flush_mask)
return 0;
for (i = 1; i < NSIG; i++)
if (sigismember (pending, i))
if (!sigismember (flush_mask, i)
|| sigismember (&blocked, i)
|| sigismember (&ignored, i))
sigdelset (pending, i);
if (sigisemptyset (pending))
return 0;
return 1;
}
/* DATA is interpreted as a mask of signals to flush. If LP has
signals pending, and they are all in the flush mask, then arrange
to flush them. LP should be stopped, as should all other threads
it might share a signal queue with. */
static int
flush_callback (struct lwp_info *lp, void *data)
{
sigset_t *flush_mask = data;
sigset_t pending, intersection, blocked, ignored;
int pid, status;
/* Normally, when an LWP exits, it is removed from the LWP list. The
last LWP isn't removed till later, however. So if there is only
one LWP on the list, make sure it's alive. */
if (lwp_list == lp && lp->next == NULL)
if (!linux_nat_thread_alive (lp->ptid))
return 0;
/* Just because the LWP is stopped doesn't mean that new signals
can't arrive from outside, so this function must be careful of
race conditions. However, because all threads are stopped, we
can assume that the pending mask will not shrink unless we resume
the LWP, and that it will then get another signal. We can't
control which one, however. */
if (lp->status)
{
if (debug_linux_nat)
printf_unfiltered (_("FC: LP has pending status %06x\n"), lp->status);
if (WIFSTOPPED (lp->status) && sigismember (flush_mask, WSTOPSIG (lp->status)))
lp->status = 0;
}
while (linux_nat_has_pending (GET_LWP (lp->ptid), &pending, flush_mask))
{
int ret;
errno = 0;
ret = ptrace (PTRACE_CONT, GET_LWP (lp->ptid), 0, 0);
if (debug_linux_nat)
fprintf_unfiltered (gdb_stderr,
"FC: Sent PTRACE_CONT, ret %d %d\n", ret, errno);
lp->stopped = 0;
stop_wait_callback (lp, flush_mask);
if (debug_linux_nat)
fprintf_unfiltered (gdb_stderr,
"FC: Wait finished; saved status is %d\n",
lp->status);
}
return 0;
}
/* Return non-zero if LP has a wait status pending. */
static int
status_callback (struct lwp_info *lp, void *data)
{
/* Only report a pending wait status if we pretend that this has
indeed been resumed. */
return (lp->status != 0 && lp->resumed);
}
/* Return non-zero if LP isn't stopped. */
static int
running_callback (struct lwp_info *lp, void *data)
{
return (lp->stopped == 0 || (lp->status != 0 && lp->resumed));
}
/* Count the LWP's that have had events. */
static int
count_events_callback (struct lwp_info *lp, void *data)
{
int *count = data;
gdb_assert (count != NULL);
/* Count only LWPs that have a SIGTRAP event pending. */
if (lp->status != 0
&& WIFSTOPPED (lp->status) && WSTOPSIG (lp->status) == SIGTRAP)
(*count)++;
return 0;
}
/* Select the LWP (if any) that is currently being single-stepped. */
static int
select_singlestep_lwp_callback (struct lwp_info *lp, void *data)
{
if (lp->step && lp->status != 0)
return 1;
else
return 0;
}
/* Select the Nth LWP that has had a SIGTRAP event. */
static int
select_event_lwp_callback (struct lwp_info *lp, void *data)
{
int *selector = data;
gdb_assert (selector != NULL);
/* Select only LWPs that have a SIGTRAP event pending. */
if (lp->status != 0
&& WIFSTOPPED (lp->status) && WSTOPSIG (lp->status) == SIGTRAP)
if ((*selector)-- == 0)
return 1;
return 0;
}
static int
cancel_breakpoints_callback (struct lwp_info *lp, void *data)
{
struct lwp_info *event_lp = data;
/* Leave the LWP that has been elected to receive a SIGTRAP alone. */
if (lp == event_lp)
return 0;
/* If a LWP other than the LWP that we're reporting an event for has
hit a GDB breakpoint (as opposed to some random trap signal),
then just arrange for it to hit it again later. We don't keep
the SIGTRAP status and don't forward the SIGTRAP signal to the
LWP. We will handle the current event, eventually we will resume
all LWPs, and this one will get its breakpoint trap again.
If we do not do this, then we run the risk that the user will
delete or disable the breakpoint, but the LWP will have already
tripped on it. */
if (lp->status != 0
&& WIFSTOPPED (lp->status) && WSTOPSIG (lp->status) == SIGTRAP
&& breakpoint_inserted_here_p (read_pc_pid (lp->ptid) -
DECR_PC_AFTER_BREAK))
{
if (debug_linux_nat)
fprintf_unfiltered (gdb_stdlog,
"CBC: Push back breakpoint for %s\n",
target_pid_to_str (lp->ptid));
/* Back up the PC if necessary. */
if (DECR_PC_AFTER_BREAK)
write_pc_pid (read_pc_pid (lp->ptid) - DECR_PC_AFTER_BREAK, lp->ptid);
/* Throw away the SIGTRAP. */
lp->status = 0;
}
return 0;
}
/* Select one LWP out of those that have events pending. */
static void
select_event_lwp (struct lwp_info **orig_lp, int *status)
{
int num_events = 0;
int random_selector;
struct lwp_info *event_lp;
/* Record the wait status for the original LWP. */
(*orig_lp)->status = *status;
/* Give preference to any LWP that is being single-stepped. */
event_lp = iterate_over_lwps (select_singlestep_lwp_callback, NULL);
if (event_lp != NULL)
{
if (debug_linux_nat)
fprintf_unfiltered (gdb_stdlog,
"SEL: Select single-step %s\n",
target_pid_to_str (event_lp->ptid));
}
else
{
/* No single-stepping LWP. Select one at random, out of those
which have had SIGTRAP events. */
/* First see how many SIGTRAP events we have. */
iterate_over_lwps (count_events_callback, &num_events);
/* Now randomly pick a LWP out of those that have had a SIGTRAP. */
random_selector = (int)
((num_events * (double) rand ()) / (RAND_MAX + 1.0));
if (debug_linux_nat && num_events > 1)
fprintf_unfiltered (gdb_stdlog,
"SEL: Found %d SIGTRAP events, selecting #%d\n",
num_events, random_selector);
event_lp = iterate_over_lwps (select_event_lwp_callback,
&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, void *data)
{
return lp->resumed;
}
/* Stop an active thread, verify it still exists, then resume it. */
static int
stop_and_resume_callback (struct lwp_info *lp, void *data)
{
struct lwp_info *ptr;
if (!lp->stopped && !lp->signalled)
{
stop_callback (lp, NULL);
stop_wait_callback (lp, NULL);
/* Resume if the lwp still exists. */
for (ptr = lwp_list; ptr; ptr = ptr->next)
if (lp == ptr)
{
resume_callback (lp, NULL);
resume_set_callback (lp, NULL);
}
}
return 0;
}
static ptid_t
linux_nat_wait (ptid_t ptid, struct target_waitstatus *ourstatus)
{
struct lwp_info *lp = NULL;
int options = 0;
int status = 0;
pid_t pid = PIDGET (ptid);
sigset_t flush_mask;
/* The first time we get here after starting a new inferior, we may
not have added it to the LWP list yet - this is the earliest
moment at which we know its PID. */
if (num_lwps == 0)
{
gdb_assert (!is_lwp (inferior_ptid));
inferior_ptid = BUILD_LWP (GET_PID (inferior_ptid),
GET_PID (inferior_ptid));
lp = add_lwp (inferior_ptid);
lp->resumed = 1;
}
sigemptyset (&flush_mask);
/* Make sure SIGCHLD is blocked. */
if (!sigismember (&blocked_mask, SIGCHLD))
{
sigaddset (&blocked_mask, SIGCHLD);
sigprocmask (SIG_BLOCK, &blocked_mask, NULL);
}
retry:
/* Make sure there is at least one LWP that has been resumed. */
gdb_assert (iterate_over_lwps (resumed_callback, NULL));
/* First check if there is a LWP with a wait status pending. */
if (pid == -1)
{
/* Any LWP that's been resumed will do. */
lp = iterate_over_lwps (status_callback, NULL);
if (lp)
{
status = lp->status;
lp->status = 0;
if (debug_linux_nat && status)
fprintf_unfiltered (gdb_stdlog,
"LLW: Using pending wait status %s for %s.\n",
status_to_str (status),
target_pid_to_str (lp->ptid));
}
/* But if we don't fine one, we'll have to wait, and check both
cloned and uncloned processes. We start with the cloned
processes. */
options = __WCLONE | WNOHANG;
}
else if (is_lwp (ptid))
{
if (debug_linux_nat)
fprintf_unfiltered (gdb_stdlog,
"LLW: Waiting for specific LWP %s.\n",
target_pid_to_str (ptid));
/* We have a specific LWP to check. */
lp = find_lwp_pid (ptid);
gdb_assert (lp);
status = lp->status;
lp->status = 0;
if (debug_linux_nat && status)
fprintf_unfiltered (gdb_stdlog,
"LLW: Using pending wait status %s for %s.\n",
status_to_str (status),
target_pid_to_str (lp->ptid));
/* If we have to wait, take into account whether PID is a cloned
process or not. And we have to convert it to something that
the layer beneath us can understand. */
options = lp->cloned ? __WCLONE : 0;
pid = GET_LWP (ptid);
}
if (status && lp->signalled)
{
/* A pending SIGSTOP may interfere with the normal stream of
events. In a typical case where interference is a problem,
we have a SIGSTOP signal pending for LWP A while
single-stepping it, encounter an event in LWP B, and take the
pending SIGSTOP while trying to stop LWP A. After processing
the event in LWP B, LWP A is continued, and we'll never see
the SIGTRAP associated with the last time we were
single-stepping LWP A. */
/* Resume the thread. It should halt immediately returning the
pending SIGSTOP. */
registers_changed ();
linux_ops->to_resume (pid_to_ptid (GET_LWP (lp->ptid)),
lp->step, TARGET_SIGNAL_0);
if (debug_linux_nat)
fprintf_unfiltered (gdb_stdlog,
"LLW: %s %s, 0, 0 (expect SIGSTOP)\n",
lp->step ? "PTRACE_SINGLESTEP" : "PTRACE_CONT",
target_pid_to_str (lp->ptid));
lp->stopped = 0;
gdb_assert (lp->resumed);
/* This should catch the pending SIGSTOP. */
stop_wait_callback (lp, NULL);
}
set_sigint_trap (); /* Causes SIGINT to be passed on to the
attached process. */
set_sigio_trap ();
while (status == 0)
{
pid_t lwpid;
lwpid = my_waitpid (pid, &status, options);
if (lwpid > 0)
{
gdb_assert (pid == -1 || lwpid == pid);
if (debug_linux_nat)
{
fprintf_unfiltered (gdb_stdlog,
"LLW: waitpid %ld received %s\n",
(long) lwpid, status_to_str (status));
}
lp = find_lwp_pid (pid_to_ptid (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. */
if (WIFSTOPPED (status) && !lp)
{
linux_record_stopped_pid (lwpid);
status = 0;
continue;
}
/* 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 original forked and then it
exits. */
if (!WIFSTOPPED (status) && !lp)
{
status = 0;
continue;
}
/* NOTE drow/2003-06-17: This code seems to be meant for debugging
CLONE_PTRACE processes which do not use the thread library -
otherwise we wouldn't find the new LWP this way. That doesn't
currently work, and the following code is currently unreachable
due to the two blocks above. If it's fixed some day, this code
should be broken out into a function so that we can also pick up
LWPs from the new interface. */
if (!lp)
{
lp = add_lwp (BUILD_LWP (lwpid, GET_PID (inferior_ptid)));
if (options & __WCLONE)
lp->cloned = 1;
gdb_assert (WIFSTOPPED (status)
&& WSTOPSIG (status) == SIGSTOP);
lp->signalled = 1;
if (!in_thread_list (inferior_ptid))
{
inferior_ptid = BUILD_LWP (GET_PID (inferior_ptid),
GET_PID (inferior_ptid));
add_thread (inferior_ptid);
}
add_thread (lp->ptid);
printf_unfiltered (_("[New %s]\n"),
target_pid_to_str (lp->ptid));
}
/* Handle GNU/Linux's extended waitstatus for trace events. */
if (WIFSTOPPED (status) && WSTOPSIG (status) == SIGTRAP && status >> 16 != 0)
{
if (debug_linux_nat)
fprintf_unfiltered (gdb_stdlog,
"LLW: Handling extended status 0x%06x\n",
status);
if (linux_nat_handle_extended (lp, status, 0))
{
status = 0;
continue;
}
}
/* Check if the thread has exited. */
if ((WIFEXITED (status) || WIFSIGNALED (status)) && num_lwps > 1)
{
/* If this is the main thread, we must stop all threads and
verify if they are still alive. This is because in the nptl
thread model, there is no signal issued for exiting LWPs
other than the main thread. We only get the main thread
exit signal once all child threads have already exited.
If we stop all the threads and use the stop_wait_callback
to check if they have exited we can determine whether this
signal should be ignored or whether it means the end of the
debugged application, regardless of which threading model
is being used. */
if (GET_PID (lp->ptid) == GET_LWP (lp->ptid))
{
lp->stopped = 1;
iterate_over_lwps (stop_and_resume_callback, NULL);
}
if (debug_linux_nat)
fprintf_unfiltered (gdb_stdlog,
"LLW: %s exited.\n",
target_pid_to_str (lp->ptid));
exit_lwp (lp);
/* If there is at least one more LWP, then the exit signal
was not the end of the debugged application and should be
ignored. */
if (num_lwps > 0)
{
/* Make sure there is at least one thread running. */
gdb_assert (iterate_over_lwps (running_callback, NULL));
/* Discard the event. */
status = 0;
continue;
}
}
/* Check if the current LWP has previously exited. In the nptl
thread model, LWPs other than the main thread do not issue
signals when they exit so we must check whenever the thread
has stopped. A similar check is made in stop_wait_callback(). */
if (num_lwps > 1 && !linux_nat_thread_alive (lp->ptid))
{
if (debug_linux_nat)
fprintf_unfiltered (gdb_stdlog,
"LLW: %s exited.\n",
target_pid_to_str (lp->ptid));
exit_lwp (lp);
/* Make sure there is at least one thread running. */
gdb_assert (iterate_over_lwps (running_callback, NULL));
/* Discard the event. */
status = 0;
continue;
}
/* 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)
{
if (debug_linux_nat)
fprintf_unfiltered (gdb_stdlog,
"LLW: Delayed SIGSTOP caught for %s.\n",
target_pid_to_str (lp->ptid));
/* This is a delayed SIGSTOP. */
lp->signalled = 0;
registers_changed ();
linux_ops->to_resume (pid_to_ptid (GET_LWP (lp->ptid)),
lp->step, TARGET_SIGNAL_0);
if (debug_linux_nat)
fprintf_unfiltered (gdb_stdlog,
"LLW: %s %s, 0, 0 (discard SIGSTOP)\n",
lp->step ?
"PTRACE_SINGLESTEP" : "PTRACE_CONT",
target_pid_to_str (lp->ptid));
lp->stopped = 0;
gdb_assert (lp->resumed);
/* Discard the event. */
status = 0;
continue;
}
break;
}
if (pid == -1)
{
/* Alternate between checking cloned and uncloned processes. */
options ^= __WCLONE;
/* And suspend every time we have checked both. */
if (options & __WCLONE)
sigsuspend (&suspend_mask);
}
/* We shouldn't end up here unless we want to try again. */
gdb_assert (status == 0);
}
clear_sigio_trap ();
clear_sigint_trap ();
gdb_assert (lp);
/* 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))
{
int signo = target_signal_from_host (WSTOPSIG (status));
/* If we get a signal while single-stepping, we may need special
care, e.g. to skip the signal handler. Defer to common code. */
if (!lp->step
&& signal_stop_state (signo) == 0
&& signal_print_state (signo) == 0
&& signal_pass_state (signo) == 1)
{
/* FIMXE: kettenis/2001-06-06: Should we resume all threads
here? It is not clear we should. GDB may not expect
other threads to run. On the other hand, not resuming
newly attached threads may cause an unwanted delay in
getting them running. */
registers_changed ();
linux_ops->to_resume (pid_to_ptid (GET_LWP (lp->ptid)),
lp->step, signo);
if (debug_linux_nat)
fprintf_unfiltered (gdb_stdlog,
"LLW: %s %s, %s (preempt 'handle')\n",
lp->step ?
"PTRACE_SINGLESTEP" : "PTRACE_CONT",
target_pid_to_str (lp->ptid),
signo ? strsignal (signo) : "0");
lp->stopped = 0;
status = 0;
goto retry;
}
if (signo == TARGET_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 LWP's
will receive it. Since we only want to report it once,
we try to flush it from all LWPs except this one. */
sigaddset (&flush_mask, SIGINT);
}
}
/* This LWP is stopped now. */
lp->stopped = 1;
if (debug_linux_nat)
fprintf_unfiltered (gdb_stdlog, "LLW: Candidate event %s in %s.\n",
status_to_str (status), target_pid_to_str (lp->ptid));
/* Now stop all other LWP's ... */
iterate_over_lwps (stop_callback, NULL);
/* ... and wait until all of them have reported back that they're no
longer running. */
iterate_over_lwps (stop_wait_callback, &flush_mask);
iterate_over_lwps (flush_callback, &flush_mask);
/* If we're not waiting for a specific LWP, choose an event LWP from
among those that have had events. Giving equal priority to all
LWPs that have had events helps prevent starvation. */
if (pid == -1)
select_event_lwp (&lp, &status);
/* Now that we've selected our final event LWP, cancel any
breakpoints in other LWPs that have hit a GDB breakpoint. See
the comment in cancel_breakpoints_callback to find out why. */
iterate_over_lwps (cancel_breakpoints_callback, lp);
if (WIFSTOPPED (status) && WSTOPSIG (status) == SIGTRAP)
{
trap_ptid = lp->ptid;
if (debug_linux_nat)
fprintf_unfiltered (gdb_stdlog,
"LLW: trap_ptid is %s.\n",
target_pid_to_str (trap_ptid));
}
else
trap_ptid = null_ptid;
if (lp->waitstatus.kind != TARGET_WAITKIND_IGNORE)
{
*ourstatus = lp->waitstatus;
lp->waitstatus.kind = TARGET_WAITKIND_IGNORE;
}
else
store_waitstatus (ourstatus, status);
return lp->ptid;
}
static int
kill_callback (struct lwp_info *lp, void *data)
{
errno = 0;
ptrace (PTRACE_KILL, GET_LWP (lp->ptid), 0, 0);
if (debug_linux_nat)
fprintf_unfiltered (gdb_stdlog,
"KC: PTRACE_KILL %s, 0, 0 (%s)\n",
target_pid_to_str (lp->ptid),
errno ? safe_strerror (errno) : "OK");
return 0;
}
static int
kill_wait_callback (struct lwp_info *lp, void *data)
{
pid_t pid;
/* We must make sure that there are no pending events (delayed
SIGSTOPs, pending SIGTRAPs, etc.) to make sure the current
program doesn't interfere with any following debugging session. */
/* For cloned processes we must check both with __WCLONE and
without, since the exit status of a cloned process isn't reported
with __WCLONE. */
if (lp->cloned)
{
do
{
pid = my_waitpid (GET_LWP (lp->ptid), NULL, __WCLONE);
if (pid != (pid_t) -1 && debug_linux_nat)
{
fprintf_unfiltered (gdb_stdlog,
"KWC: wait %s received unknown.\n",
target_pid_to_str (lp->ptid));
}
}
while (pid == GET_LWP (lp->ptid));
gdb_assert (pid == -1 && errno == ECHILD);
}
do
{
pid = my_waitpid (GET_LWP (lp->ptid), NULL, 0);
if (pid != (pid_t) -1 && debug_linux_nat)
{
fprintf_unfiltered (gdb_stdlog,
"KWC: wait %s received unk.\n",
target_pid_to_str (lp->ptid));
}
}
while (pid == GET_LWP (lp->ptid));
gdb_assert (pid == -1 && errno == ECHILD);
return 0;
}
static void
linux_nat_kill (void)
{
struct target_waitstatus last;
ptid_t last_ptid;
int status;
/* If we're stopped while forking and we haven't followed yet,
kill the other task. We need to do this first because the
parent will be sleeping if this is a vfork. */
get_last_target_status (&last_ptid, &last);
if (last.kind == TARGET_WAITKIND_FORKED
|| last.kind == TARGET_WAITKIND_VFORKED)
{
ptrace (PT_KILL, last.value.related_pid, 0, 0);
wait (&status);
}
if (forks_exist_p ())
linux_fork_killall ();
else
{
/* Kill all LWP's ... */
iterate_over_lwps (kill_callback, NULL);
/* ... and wait until we've flushed all events. */
iterate_over_lwps (kill_wait_callback, NULL);
}
target_mourn_inferior ();
}
static void
linux_nat_mourn_inferior (void)
{
trap_ptid = null_ptid;
/* Destroy LWP info; it's no longer valid. */
init_lwp_list ();
/* Restore the original signal mask. */
sigprocmask (SIG_SETMASK, &normal_mask, NULL);
sigemptyset (&blocked_mask);
if (! forks_exist_p ())
/* Normal case, no other forks available. */
linux_ops->to_mourn_inferior ();
else
/* Multi-fork case. The current inferior_ptid has exited, but
there are other viable forks to debug. Delete the exiting
one and context-switch to the first available. */
linux_fork_mourn_inferior ();
}
static LONGEST
linux_nat_xfer_partial (struct target_ops *ops, enum target_object object,
const char *annex, gdb_byte *readbuf,
const gdb_byte *writebuf,
ULONGEST offset, LONGEST len)
{
struct cleanup *old_chain = save_inferior_ptid ();
LONGEST xfer;
if (is_lwp (inferior_ptid))
inferior_ptid = pid_to_ptid (GET_LWP (inferior_ptid));
xfer = linux_ops->to_xfer_partial (ops, object, annex, readbuf, writebuf,
offset, len);
do_cleanups (old_chain);
return xfer;
}
static int
linux_nat_thread_alive (ptid_t ptid)
{
gdb_assert (is_lwp (ptid));
errno = 0;
ptrace (PTRACE_PEEKUSER, GET_LWP (ptid), 0, 0);
if (debug_linux_nat)
fprintf_unfiltered (gdb_stdlog,
"LLTA: PTRACE_PEEKUSER %s, 0, 0 (%s)\n",
target_pid_to_str (ptid),
errno ? safe_strerror (errno) : "OK");
/* Not every Linux kernel implements PTRACE_PEEKUSER. But we can
handle that case gracefully since ptrace will first do a lookup
for the process based upon the passed-in pid. If that fails we
will get either -ESRCH or -EPERM, otherwise the child exists and
is alive. */
if (errno == ESRCH || errno == EPERM)
return 0;
return 1;
}
static char *
linux_nat_pid_to_str (ptid_t ptid)
{
static char buf[64];
if (lwp_list && lwp_list->next && is_lwp (ptid))
{
snprintf (buf, sizeof (buf), "LWP %ld", GET_LWP (ptid));
return buf;
}
return normal_pid_to_str (ptid);
}
static void
sigchld_handler (int signo)
{
/* Do nothing. The only reason for this handler is that it allows
us to use sigsuspend in linux_nat_wait above to wait for the
arrival of a SIGCHLD. */
}
/* Accepts an integer PID; Returns a string representing a file that
can be opened to get the symbols for the child process. */
char *
child_pid_to_exec_file (int pid)
{
char *name1, *name2;
name1 = xmalloc (MAXPATHLEN);
name2 = xmalloc (MAXPATHLEN);
make_cleanup (xfree, name1);
make_cleanup (xfree, name2);
memset (name2, 0, MAXPATHLEN);
sprintf (name1, "/proc/%d/exe", pid);
if (readlink (name1, name2, MAXPATHLEN) > 0)
return name2;
else
return name1;
}
/* Service function for corefiles and info proc. */
static int
read_mapping (FILE *mapfile,
long long *addr,
long long *endaddr,
char *permissions,
long long *offset,
char *device, long long *inode, char *filename)
{
int ret = fscanf (mapfile, "%llx-%llx %s %llx %s %llx",
addr, endaddr, permissions, offset, device, inode);
filename[0] = '\0';
if (ret > 0 && ret != EOF)
{
/* Eat everything up to EOL for the filename. This will prevent
weird filenames (such as one with embedded whitespace) from
confusing this code. It also makes this code more robust in
respect to annotations the kernel may add after the filename.
Note the filename is used for informational purposes
only. */
ret += fscanf (mapfile, "%[^\n]\n", filename);
}
return (ret != 0 && ret != EOF);
}
/* Fills the "to_find_memory_regions" target vector. Lists the memory
regions in the inferior for a corefile. */
static int
linux_nat_find_memory_regions (int (*func) (CORE_ADDR,
unsigned long,
int, int, int, void *), void *obfd)
{
long long pid = PIDGET (inferior_ptid);
char mapsfilename[MAXPATHLEN];
FILE *mapsfile;
long long addr, endaddr, size, offset, inode;
char permissions[8], device[8], filename[MAXPATHLEN];
int read, write, exec;
int ret;
/* Compose the filename for the /proc memory map, and open it. */
sprintf (mapsfilename, "/proc/%lld/maps", pid);
if ((mapsfile = fopen (mapsfilename, "r")) == NULL)
error (_("Could not open %s."), mapsfilename);
if (info_verbose)
fprintf_filtered (gdb_stdout,
"Reading memory regions from %s\n", mapsfilename);
/* Now iterate until end-of-file. */
while (read_mapping (mapsfile, &addr, &endaddr, &permissions[0],
&offset, &device[0], &inode, &filename[0]))
{
size = endaddr - addr;
/* Get the segment's permissions. */
read = (strchr (permissions, 'r') != 0);
write = (strchr (permissions, 'w') != 0);
exec = (strchr (permissions, 'x') != 0);
if (info_verbose)
{
fprintf_filtered (gdb_stdout,
"Save segment, %lld bytes at 0x%s (%c%c%c)",
size, paddr_nz (addr),
read ? 'r' : ' ',
write ? 'w' : ' ', exec ? 'x' : ' ');
if (filename && filename[0])
fprintf_filtered (gdb_stdout, " for %s", filename);
fprintf_filtered (gdb_stdout, "\n");
}
/* Invoke the callback function to create the corefile
segment. */
func (addr, size, read, write, exec, obfd);
}
fclose (mapsfile);
return 0;
}
/* Records the thread's register state for the corefile note
section. */
static char *
linux_nat_do_thread_registers (bfd *obfd, ptid_t ptid,
char *note_data, int *note_size)
{
gdb_gregset_t gregs;
gdb_fpregset_t fpregs;
#ifdef FILL_FPXREGSET
gdb_fpxregset_t fpxregs;
#endif
unsigned long lwp = ptid_get_lwp (ptid);
struct gdbarch *gdbarch = current_gdbarch;
const struct regset *regset;
int core_regset_p;
core_regset_p = gdbarch_regset_from_core_section_p (gdbarch);
if (core_regset_p
&& (regset = gdbarch_regset_from_core_section (gdbarch, ".reg",
sizeof (gregs))) != NULL
&& regset->collect_regset != NULL)
regset->collect_regset (regset, current_regcache, -1,
&gregs, sizeof (gregs));
else
fill_gregset (&gregs, -1);
note_data = (char *) elfcore_write_prstatus (obfd,
note_data,
note_size,
lwp,
stop_signal, &gregs);
if (core_regset_p
&& (regset = gdbarch_regset_from_core_section (gdbarch, ".reg2",
sizeof (fpregs))) != NULL
&& regset->collect_regset != NULL)
regset->collect_regset (regset, current_regcache, -1,
&fpregs, sizeof (fpregs));
else
fill_fpregset (&fpregs, -1);
note_data = (char *) elfcore_write_prfpreg (obfd,
note_data,
note_size,
&fpregs, sizeof (fpregs));
#ifdef FILL_FPXREGSET
if (core_regset_p
&& (regset = gdbarch_regset_from_core_section (gdbarch, ".reg-xfp",
sizeof (fpxregs))) != NULL
&& regset->collect_regset != NULL)
regset->collect_regset (regset, current_regcache, -1,
&fpxregs, sizeof (fpxregs));
else
fill_fpxregset (&fpxregs, -1);
note_data = (char *) elfcore_write_prxfpreg (obfd,
note_data,
note_size,
&fpxregs, sizeof (fpxregs));
#endif
return note_data;
}
struct linux_nat_corefile_thread_data
{
bfd *obfd;
char *note_data;
int *note_size;
int num_notes;
};
/* Called by gdbthread.c once per thread. Records the thread's
register state for the corefile note section. */
static int
linux_nat_corefile_thread_callback (struct lwp_info *ti, void *data)
{
struct linux_nat_corefile_thread_data *args = data;
ptid_t saved_ptid = inferior_ptid;
inferior_ptid = ti->ptid;
registers_changed ();
target_fetch_registers (-1); /* FIXME should not be necessary;
fill_gregset should do it automatically. */
args->note_data = linux_nat_do_thread_registers (args->obfd,
ti->ptid,
args->note_data,
args->note_size);
args->num_notes++;
inferior_ptid = saved_ptid;
registers_changed ();
target_fetch_registers (-1); /* FIXME should not be necessary;
fill_gregset should do it automatically. */
return 0;
}
/* Records the register state for the corefile note section. */
static char *
linux_nat_do_registers (bfd *obfd, ptid_t ptid,
char *note_data, int *note_size)
{
registers_changed ();
target_fetch_registers (-1); /* FIXME should not be necessary;
fill_gregset should do it automatically. */
return linux_nat_do_thread_registers (obfd,
ptid_build (ptid_get_pid (inferior_ptid),
ptid_get_pid (inferior_ptid),
0),
note_data, note_size);
return note_data;
}
/* Fills the "to_make_corefile_note" target vector. Builds the note
section for a corefile, and returns it in a malloc buffer. */
static char *
linux_nat_make_corefile_notes (bfd *obfd, int *note_size)
{
struct linux_nat_corefile_thread_data thread_args;
struct cleanup *old_chain;
char fname[16] = { '\0' };
char psargs[80] = { '\0' };
char *note_data = NULL;
ptid_t current_ptid = inferior_ptid;
gdb_byte *auxv;
int auxv_len;
if (get_exec_file (0))
{
strncpy (fname, strrchr (get_exec_file (0), '/') + 1, sizeof (fname));
strncpy (psargs, get_exec_file (0), sizeof (psargs));
if (get_inferior_args ())
{
strncat (psargs, " ", sizeof (psargs) - strlen (psargs));
strncat (psargs, get_inferior_args (),
sizeof (psargs) - strlen (psargs));
}
note_data = (char *) elfcore_write_prpsinfo (obfd,
note_data,
note_size, fname, psargs);
}
/* Dump information for threads. */
thread_args.obfd = obfd;
thread_args.note_data = note_data;
thread_args.note_size = note_size;
thread_args.num_notes = 0;
iterate_over_lwps (linux_nat_corefile_thread_callback, &thread_args);
if (thread_args.num_notes == 0)
{
/* iterate_over_threads didn't come up with any threads; just
use inferior_ptid. */
note_data = linux_nat_do_registers (obfd, inferior_ptid,
note_data, note_size);
}
else
{
note_data = thread_args.note_data;
}
auxv_len = target_read_alloc (&current_target, TARGET_OBJECT_AUXV,
NULL, &auxv);
if (auxv_len > 0)
{
note_data = elfcore_write_note (obfd, note_data, note_size,
"CORE", NT_AUXV, auxv, auxv_len);
xfree (auxv);
}
make_cleanup (xfree, note_data);
return note_data;
}
/* Implement the "info proc" command. */
static void
linux_nat_info_proc_cmd (char *args, int from_tty)
{
long long pid = PIDGET (inferior_ptid);
FILE *procfile;
char **argv = NULL;
char buffer[MAXPATHLEN];
char fname1[MAXPATHLEN], fname2[MAXPATHLEN];
int cmdline_f = 1;
int cwd_f = 1;
int exe_f = 1;
int mappings_f = 0;
int environ_f = 0;
int status_f = 0;
int stat_f = 0;
int all = 0;
struct stat dummy;
if (args)
{
/* Break up 'args' into an argv array. */
if ((argv = buildargv (args)) == NULL)
nomem (0);
else
make_cleanup_freeargv (argv);
}
while (argv != NULL && *argv != NULL)
{
if (isdigit (argv[0][0]))
{
pid = strtoul (argv[0], NULL, 10);
}
else if (strncmp (argv[0], "mappings", strlen (argv[0])) == 0)
{
mappings_f = 1;
}
else if (strcmp (argv[0], "status") == 0)
{
status_f = 1;
}
else if (strcmp (argv[0], "stat") == 0)
{
stat_f = 1;
}
else if (strcmp (argv[0], "cmd") == 0)
{
cmdline_f = 1;
}
else if (strncmp (argv[0], "exe", strlen (argv[0])) == 0)
{
exe_f = 1;
}
else if (strcmp (argv[0], "cwd") == 0)
{
cwd_f = 1;
}
else if (strncmp (argv[0], "all", strlen (argv[0])) == 0)
{
all = 1;
}
else
{
/* [...] (future options here) */
}
argv++;
}
if (pid == 0)
error (_("No current process: you must name one."));
sprintf (fname1, "/proc/%lld", pid);
if (stat (fname1, &dummy) != 0)
error (_("No /proc directory: '%s'"), fname1);
printf_filtered (_("process %lld\n"), pid);
if (cmdline_f || all)
{
sprintf (fname1, "/proc/%lld/cmdline", pid);
if ((procfile = fopen (fname1, "r")) > 0)
{
fgets (buffer, sizeof (buffer), procfile);
printf_filtered ("cmdline = '%s'\n", buffer);
fclose (procfile);
}
else
warning (_("unable to open /proc file '%s'"), fname1);
}
if (cwd_f || all)
{
sprintf (fname1, "/proc/%lld/cwd", pid);
memset (fname2, 0, sizeof (fname2));
if (readlink (fname1, fname2, sizeof (fname2)) > 0)
printf_filtered ("cwd = '%s'\n", fname2);
else
warning (_("unable to read link '%s'"), fname1);
}
if (exe_f || all)
{
sprintf (fname1, "/proc/%lld/exe", pid);
memset (fname2, 0, sizeof (fname2));
if (readlink (fname1, fname2, sizeof (fname2)) > 0)
printf_filtered ("exe = '%s'\n", fname2);
else
warning (_("unable to read link '%s'"), fname1);
}
if (mappings_f || all)
{
sprintf (fname1, "/proc/%lld/maps", pid);
if ((procfile = fopen (fname1, "r")) > 0)
{
long long addr, endaddr, size, offset, inode;
char permissions[8], device[8], filename[MAXPATHLEN];
printf_filtered (_("Mapped address spaces:\n\n"));
if (TARGET_ADDR_BIT == 32)
{
printf_filtered ("\t%10s %10s %10s %10s %7s\n",
"Start Addr",
" End Addr",
" Size", " Offset", "objfile");
}
else
{
printf_filtered (" %18s %18s %10s %10s %7s\n",
"Start Addr",
" End Addr",
" Size", " Offset", "objfile");
}
while (read_mapping (procfile, &addr, &endaddr, &permissions[0],
&offset, &device[0], &inode, &filename[0]))
{
size = endaddr - addr;
/* FIXME: carlton/2003-08-27: Maybe the printf_filtered
calls here (and possibly above) should be abstracted
out into their own functions? Andrew suggests using
a generic local_address_string instead to print out
the addresses; that makes sense to me, too. */
if (TARGET_ADDR_BIT == 32)
{
printf_filtered ("\t%#10lx %#10lx %#10x %#10x %7s\n",
(unsigned long) addr, /* FIXME: pr_addr */
(unsigned long) endaddr,
(int) size,
(unsigned int) offset,
filename[0] ? filename : "");
}
else
{
printf_filtered (" %#18lx %#18lx %#10x %#10x %7s\n",
(unsigned long) addr, /* FIXME: pr_addr */
(unsigned long) endaddr,
(int) size,
(unsigned int) offset,
filename[0] ? filename : "");
}
}
fclose (procfile);
}
else
warning (_("unable to open /proc file '%s'"), fname1);
}
if (status_f || all)
{
sprintf (fname1, "/proc/%lld/status", pid);
if ((procfile = fopen (fname1, "r")) > 0)
{
while (fgets (buffer, sizeof (buffer), procfile) != NULL)
puts_filtered (buffer);
fclose (procfile);
}
else
warning (_("unable to open /proc file '%s'"), fname1);
}
if (stat_f || all)
{
sprintf (fname1, "/proc/%lld/stat", pid);
if ((procfile = fopen (fname1, "r")) > 0)
{
int itmp;
char ctmp;
if (fscanf (procfile, "%d ", &itmp) > 0)
printf_filtered (_("Process: %d\n"), itmp);
if (fscanf (procfile, "%s ", &buffer[0]) > 0)
printf_filtered (_("Exec file: %s\n"), buffer);
if (fscanf (procfile, "%c ", &ctmp) > 0)
printf_filtered (_("State: %c\n"), ctmp);
if (fscanf (procfile, "%d ", &itmp) > 0)
printf_filtered (_("Parent process: %d\n"), itmp);
if (fscanf (procfile, "%d ", &itmp) > 0)
printf_filtered (_("Process group: %d\n"), itmp);
if (fscanf (procfile, "%d ", &itmp) > 0)
printf_filtered (_("Session id: %d\n"), itmp);
if (fscanf (procfile, "%d ", &itmp) > 0)
printf_filtered (_("TTY: %d\n"), itmp);
if (fscanf (procfile, "%d ", &itmp) > 0)
printf_filtered (_("TTY owner process group: %d\n"), itmp);
if (fscanf (procfile, "%u ", &itmp) > 0)
printf_filtered (_("Flags: 0x%x\n"), itmp);
if (fscanf (procfile, "%u ", &itmp) > 0)
printf_filtered (_("Minor faults (no memory page): %u\n"),
(unsigned int) itmp);
if (fscanf (procfile, "%u ", &itmp) > 0)
printf_filtered (_("Minor faults, children: %u\n"),
(unsigned int) itmp);
if (fscanf (procfile, "%u ", &itmp) > 0)
printf_filtered (_("Major faults (memory page faults): %u\n"),
(unsigned int) itmp);
if (fscanf (procfile, "%u ", &itmp) > 0)
printf_filtered (_("Major faults, children: %u\n"),
(unsigned int) itmp);
if (fscanf (procfile, "%d ", &itmp) > 0)
printf_filtered ("utime: %d\n", itmp);
if (fscanf (procfile, "%d ", &itmp) > 0)
printf_filtered ("stime: %d\n", itmp);
if (fscanf (procfile, "%d ", &itmp) > 0)
printf_filtered ("utime, children: %d\n", itmp);
if (fscanf (procfile, "%d ", &itmp) > 0)
printf_filtered ("stime, children: %d\n", itmp);
if (fscanf (procfile, "%d ", &itmp) > 0)
printf_filtered (_("jiffies remaining in current time slice: %d\n"),
itmp);
if (fscanf (procfile, "%d ", &itmp) > 0)
printf_filtered ("'nice' value: %d\n", itmp);
if (fscanf (procfile, "%u ", &itmp) > 0)
printf_filtered (_("jiffies until next timeout: %u\n"),
(unsigned int) itmp);
if (fscanf (procfile, "%u ", &itmp) > 0)
printf_filtered ("jiffies until next SIGALRM: %u\n",
(unsigned int) itmp);
if (fscanf (procfile, "%d ", &itmp) > 0)
printf_filtered (_("start time (jiffies since system boot): %d\n"),
itmp);
if (fscanf (procfile, "%u ", &itmp) > 0)
printf_filtered (_("Virtual memory size: %u\n"),
(unsigned int) itmp);
if (fscanf (procfile, "%u ", &itmp) > 0)
printf_filtered (_("Resident set size: %u\n"), (unsigned int) itmp);
if (fscanf (procfile, "%u ", &itmp) > 0)
printf_filtered ("rlim: %u\n", (unsigned int) itmp);
if (fscanf (procfile, "%u ", &itmp) > 0)
printf_filtered (_("Start of text: 0x%x\n"), itmp);
if (fscanf (procfile, "%u ", &itmp) > 0)
printf_filtered (_("End of text: 0x%x\n"), itmp);
if (fscanf (procfile, "%u ", &itmp) > 0)
printf_filtered (_("Start of stack: 0x%x\n"), itmp);
#if 0 /* Don't know how architecture-dependent the rest is...
Anyway the signal bitmap info is available from "status". */
if (fscanf (procfile, "%u ", &itmp) > 0) /* FIXME arch? */
printf_filtered (_("Kernel stack pointer: 0x%x\n"), itmp);
if (fscanf (procfile, "%u ", &itmp) > 0) /* FIXME arch? */
printf_filtered (_("Kernel instr pointer: 0x%x\n"), itmp);
if (fscanf (procfile, "%d ", &itmp) > 0)
printf_filtered (_("Pending signals bitmap: 0x%x\n"), itmp);
if (fscanf (procfile, "%d ", &itmp) > 0)
printf_filtered (_("Blocked signals bitmap: 0x%x\n"), itmp);
if (fscanf (procfile, "%d ", &itmp) > 0)
printf_filtered (_("Ignored signals bitmap: 0x%x\n"), itmp);
if (fscanf (procfile, "%d ", &itmp) > 0)
printf_filtered (_("Catched signals bitmap: 0x%x\n"), itmp);
if (fscanf (procfile, "%u ", &itmp) > 0) /* FIXME arch? */
printf_filtered (_("wchan (system call): 0x%x\n"), itmp);
#endif
fclose (procfile);
}
else
warning (_("unable to open /proc file '%s'"), fname1);
}
}
/* Implement the to_xfer_partial interface for memory reads using the /proc
filesystem. Because we can use a single read() call for /proc, this
can be much more efficient than banging away at PTRACE_PEEKTEXT,
but it doesn't support writes. */
static LONGEST
linux_proc_xfer_partial (struct target_ops *ops, enum target_object object,
const char *annex, gdb_byte *readbuf,
const gdb_byte *writebuf,
ULONGEST offset, LONGEST len)
{
LONGEST ret;
int fd;
char filename[64];
if (object != TARGET_OBJECT_MEMORY || !readbuf)
return 0;
/* Don't bother for one word. */
if (len < 3 * sizeof (long))
return 0;
/* We could keep this file open and cache it - possibly one per
thread. That requires some juggling, but is even faster. */
sprintf (filename, "/proc/%d/mem", PIDGET (inferior_ptid));
fd = open (filename, O_RDONLY | O_LARGEFILE);
if (fd == -1)
return 0;
/* If pread64 is available, use it. It's faster if the kernel
supports it (only one syscall), and it's 64-bit safe even on
32-bit platforms (for instance, SPARC debugging a SPARC64
application). */
#ifdef HAVE_PREAD64
if (pread64 (fd, readbuf, len, offset) != len)
#else
if (lseek (fd, offset, SEEK_SET) == -1 || read (fd, readbuf, len) != len)
#endif
ret = 0;
else
ret = len;
close (fd);
return ret;
}
/* Parse LINE as a signal set and add its set bits to SIGS. */
static void
add_line_to_sigset (const char *line, sigset_t *sigs)
{
int len = strlen (line) - 1;
const char *p;
int signum;
if (line[len] != '\n')
error (_("Could not parse signal set: %s"), line);
p = line;
signum = len * 4;
while (len-- > 0)
{
int digit;
if (*p >= '0' && *p <= '9')
digit = *p - '0';
else if (*p >= 'a' && *p <= 'f')
digit = *p - 'a' + 10;
else
error (_("Could not parse signal set: %s"), line);
signum -= 4;
if (digit & 1)
sigaddset (sigs, signum + 1);
if (digit & 2)
sigaddset (sigs, signum + 2);
if (digit & 4)
sigaddset (sigs, signum + 3);
if (digit & 8)
sigaddset (sigs, signum + 4);
p++;
}
}
/* Find process PID's pending signals from /proc/pid/status and set
SIGS to match. */
void
linux_proc_pending_signals (int pid, sigset_t *pending, sigset_t *blocked, sigset_t *ignored)
{
FILE *procfile;
char buffer[MAXPATHLEN], fname[MAXPATHLEN];
int signum;
sigemptyset (pending);
sigemptyset (blocked);
sigemptyset (ignored);
sprintf (fname, "/proc/%d/status", pid);
procfile = fopen (fname, "r");
if (procfile == NULL)
error (_("Could not open %s"), fname);
while (fgets (buffer, MAXPATHLEN, procfile) != NULL)
{
/* Normal queued signals are on the SigPnd line in the status
file. However, 2.6 kernels also have a "shared" pending
queue for delivering signals to a thread group, so check for
a ShdPnd line also.
Unfortunately some Red Hat kernels include the shared pending
queue but not the ShdPnd status field. */
if (strncmp (buffer, "SigPnd:\t", 8) == 0)
add_line_to_sigset (buffer + 8, pending);
else if (strncmp (buffer, "ShdPnd:\t", 8) == 0)
add_line_to_sigset (buffer + 8, pending);
else if (strncmp (buffer, "SigBlk:\t", 8) == 0)
add_line_to_sigset (buffer + 8, blocked);
else if (strncmp (buffer, "SigIgn:\t", 8) == 0)
add_line_to_sigset (buffer + 8, ignored);
}
fclose (procfile);
}
static LONGEST
linux_xfer_partial (struct target_ops *ops, enum target_object object,
const char *annex, gdb_byte *readbuf,
const gdb_byte *writebuf, ULONGEST offset, LONGEST len)
{
LONGEST xfer;
if (object == TARGET_OBJECT_AUXV)
return procfs_xfer_auxv (ops, object, annex, readbuf, writebuf,
offset, len);
xfer = linux_proc_xfer_partial (ops, object, annex, readbuf, writebuf,
offset, len);
if (xfer != 0)
return xfer;
return super_xfer_partial (ops, object, annex, readbuf, writebuf,
offset, len);
}
#ifndef FETCH_INFERIOR_REGISTERS
/* Return the address in the core dump or inferior of register
REGNO. */
static CORE_ADDR
linux_register_u_offset (int regno)
{
/* FIXME drow/2005-09-04: The hardcoded use of register_addr should go
away. This requires disentangling the various definitions of it
(particularly alpha-nat.c's). */
return register_addr (regno, 0);
}
#endif
/* Create a prototype generic Linux target. The client can override
it with local methods. */
struct target_ops *
linux_target (void)
{
struct target_ops *t;
#ifdef FETCH_INFERIOR_REGISTERS
t = inf_ptrace_target ();
#else
t = inf_ptrace_trad_target (linux_register_u_offset);
#endif
t->to_insert_fork_catchpoint = child_insert_fork_catchpoint;
t->to_insert_vfork_catchpoint = child_insert_vfork_catchpoint;
t->to_insert_exec_catchpoint = child_insert_exec_catchpoint;
t->to_pid_to_exec_file = child_pid_to_exec_file;
t->to_post_startup_inferior = linux_child_post_startup_inferior;
t->to_post_attach = child_post_attach;
t->to_follow_fork = child_follow_fork;
t->to_find_memory_regions = linux_nat_find_memory_regions;
t->to_make_corefile_notes = linux_nat_make_corefile_notes;
super_xfer_partial = t->to_xfer_partial;
t->to_xfer_partial = linux_xfer_partial;
return t;
}
void
linux_nat_add_target (struct target_ops *t)
{
/* Save the provided single-threaded target. We save this in a separate
variable because another target we've inherited from (e.g. inf-ptrace)
may have saved a pointer to T; we want to use it for the final
process stratum target. */
linux_ops_saved = *t;
linux_ops = &linux_ops_saved;
/* Override some methods for multithreading. */
t->to_attach = linux_nat_attach;
t->to_detach = linux_nat_detach;
t->to_resume = linux_nat_resume;
t->to_wait = linux_nat_wait;
t->to_xfer_partial = linux_nat_xfer_partial;
t->to_kill = linux_nat_kill;
t->to_mourn_inferior = linux_nat_mourn_inferior;
t->to_thread_alive = linux_nat_thread_alive;
t->to_pid_to_str = linux_nat_pid_to_str;
t->to_has_thread_control = tc_schedlock;
/* We don't change the stratum; this target will sit at
process_stratum and thread_db will set at thread_stratum. This
is a little strange, since this is a multi-threaded-capable
target, but we want to be on the stack below thread_db, and we
also want to be used for single-threaded processes. */
add_target (t);
/* TODO: Eliminate this and have libthread_db use
find_target_beneath. */
thread_db_init (t);
}
void
_initialize_linux_nat (void)
{
struct sigaction action;
add_info ("proc", linux_nat_info_proc_cmd, _("\
Show /proc process information about any running process.\n\
Specify any process id, or use the program being debugged by default.\n\
Specify any of the following keywords for detailed info:\n\
mappings -- list of mapped memory regions.\n\
stat -- list a bunch of random process info.\n\
status -- list a different bunch of random process info.\n\
all -- list all available /proc info."));
/* Save the original signal mask. */
sigprocmask (SIG_SETMASK, NULL, &normal_mask);
action.sa_handler = sigchld_handler;
sigemptyset (&action.sa_mask);
action.sa_flags = SA_RESTART;
sigaction (SIGCHLD, &action, NULL);
/* Make sure we don't block SIGCHLD during a sigsuspend. */
sigprocmask (SIG_SETMASK, NULL, &suspend_mask);
sigdelset (&suspend_mask, SIGCHLD);
sigemptyset (&blocked_mask);
add_setshow_zinteger_cmd ("lin-lwp", no_class, &debug_linux_nat, _("\
Set debugging of GNU/Linux lwp module."), _("\
Show debugging of GNU/Linux lwp module."), _("\
Enables printf debugging output."),
NULL,
show_debug_linux_nat,
&setdebuglist, &showdebuglist);
}
/* FIXME: kettenis/2000-08-26: The stuff on this page is specific to
the GNU/Linux Threads library and therefore doesn't really belong
here. */
/* Read variable NAME in the target and return its value if found.
Otherwise return zero. It is assumed that the type of the variable
is `int'. */
static int
get_signo (const char *name)
{
struct minimal_symbol *ms;
int signo;
ms = lookup_minimal_symbol (name, NULL, NULL);
if (ms == NULL)
return 0;
if (target_read_memory (SYMBOL_VALUE_ADDRESS (ms), (gdb_byte *) &signo,
sizeof (signo)) != 0)
return 0;
return signo;
}
/* Return the set of signals used by the threads library in *SET. */
void
lin_thread_get_thread_signals (sigset_t *set)
{
struct sigaction action;
int restart, cancel;
sigemptyset (set);
restart = get_signo ("__pthread_sig_restart");
cancel = get_signo ("__pthread_sig_cancel");
/* LinuxThreads normally uses the first two RT signals, but in some legacy
cases may use SIGUSR1/SIGUSR2. NPTL always uses RT signals, but does
not provide any way for the debugger to query the signal numbers -
fortunately they don't change! */
if (restart == 0)
restart = __SIGRTMIN;
if (cancel == 0)
cancel = __SIGRTMIN + 1;
sigaddset (set, restart);
sigaddset (set, cancel);
/* The GNU/Linux Threads library makes terminating threads send a
special "cancel" signal instead of SIGCHLD. Make sure we catch
those (to prevent them from terminating GDB itself, which is
likely to be their default action) and treat them the same way as
SIGCHLD. */
action.sa_handler = sigchld_handler;
sigemptyset (&action.sa_mask);
action.sa_flags = SA_RESTART;
sigaction (cancel, &action, NULL);
/* We block the "cancel" signal throughout this code ... */
sigaddset (&blocked_mask, cancel);
sigprocmask (SIG_BLOCK, &blocked_mask, NULL);
/* ... except during a sigsuspend. */
sigdelset (&suspend_mask, cancel);
}
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