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binutils-gdb/gdb/linux-fork.c
Pedro Alves 26cb8b7c1a [native x86 GNU/Linux] Access debug register mirror from the corresponding process. 
While reviewing the native AArch64 patch, I noticed a problem:

On 02/06/2013 08:46 PM, Pedro Alves wrote:
>
>> > +static void
>> > +aarch64_linux_prepare_to_resume (struct lwp_info *lwp)
>> > +{
>> > +  struct arch_lwp_info *info = lwp->arch_private;
>> > +
>> > +  /* NULL means this is the main thread still going through the shell,
>> > +     or, no watchpoint has been set yet.  In that case, there's
>> > +     nothing to do.  */
>> > +  if (info == NULL)
>> > +    return;
>> > +
>> > +  if (DR_HAS_CHANGED (info->dr_changed_bp)
>> > +      || DR_HAS_CHANGED (info->dr_changed_wp))
>> > +    {
>> > +      int tid = GET_LWP (lwp->ptid);
>> > +      struct aarch64_debug_reg_state *state = aarch64_get_debug_reg_state ();
> Hmm.  This is always fetching the debug_reg_state of
> the current inferior, but may not be the inferior of lwp.
> I see the same bug on x86.  Sorry about that.  I'll fix it.

A natural fix would be to make xxx_get_debug_reg_state take an
inferior argument, but that doesn't work because of the case where we
detach breakpoints/watchpoints from the child fork, at a time there's
no inferior for the child fork at all.  We do a nasty hack in
i386_inferior_data_get, but that relies on all callers pointing the
current inferior to the correct inferior, which isn't actually being
done by all callers, and I don't think we want to enforce that -- deep
in the bowls of linux-nat.c, there are many cases we resume lwps
behind the scenes, and it's be better to not have that code rely on
global state (as it doesn't today).

The fix is to decouple the watchpoints code from inferiors, making it
track target processes instead.  This way, we can freely keep track of
the watchpoint mirrors for these processes behind the core's back.
Checkpoints also play dirty tricks with swapping the process behind
the inferior, so they get special treatment too in the patch (which
just amounts to calling a new hook).  Instead of the old hack in
i386_inferior_data_get, where we returned a copy of the current
inferior's debug registers mirror, as soon as we detect a fork in the
target, we copy the debug register mirror from the parent to the child
process.

I don't have an old kernel handy to test, but I stepped through gdb doing
the watchpoint removal in the fork child in the watchpoint-fork test
seeing that the debug registers end up cleared in the child.

I didn't find the need for linux_nat_iterate_watchpoint_lwps.  If
we use plain iterate_over_lwps instead, what happens is that
when removing watchpoints, that iterate_over_lwps doesn't actually
iterate over anything, since the fork child is not added to the
lwp list until later, at detach time, in linux_child_follow_fork.
And if we don't iterate over that lwp, we don't mark its debug
registers as needing update.  But linux_child_follow_fork takes
care of doing that explicitly:

	  child_lp = add_lwp (inferior_ptid);
	  child_lp->stopped = 1;
	  child_lp->last_resume_kind = resume_stop;
	  make_cleanup (delete_lwp_cleanup, child_lp);

	  /* CHILD_LP has new PID, therefore linux_nat_new_thread is not called for it.
	     See i386_inferior_data_get for the Linux kernel specifics.
	     Ensure linux_nat_prepare_to_resume will reset the hardware debug
	     registers.  It is done by the linux_nat_new_thread call, which is
	     being skipped in add_lwp above for the first lwp of a pid.  */
	  gdb_assert (num_lwps (GET_PID (child_lp->ptid)) == 1);
	  if (linux_nat_new_thread != NULL)
	    linux_nat_new_thread (child_lp);

	  if (linux_nat_prepare_to_resume != NULL)
	    linux_nat_prepare_to_resume (child_lp);
	  ptrace (PTRACE_DETACH, child_pid, 0, 0);

so unless I'm missing something (quite possible) it ends up all
the same.  But, the !detach-on-fork, and the "follow-fork child" paths
should also call linux_nat_new_thread, and they don't presently.  It
seems to me in those cases we're not clearing debug regs correctly
when that's needed.  Instead of copying that bit that works around
add_lwp bypassing the linux_nat_new_thread call, I thought it'd
be better to add an add_initial_lwp call to be used in the case we
really need to bypass linux_nat_new_thread, and make
add_lwp always call linux_nat_new_thread.

i386_cleanup_dregs is rewritten to forget about the current process
debug mirrors, which takes cares of other i386 ports.  Only a couple
of extra tweaks here and there were needed, as some targets wheren't
actually calling i386_cleanup_dregs.

Tested on Fedora 17 x86_64 -m64/-m32.

GDBserver already fetches the i386_debug_reg_state from the right
process, and, it doesn't handle forks at all, so no fix is needed over
there.

gdb/
2013-02-13  Pedro Alves  <palves@redhat.com>

	* amd64-linux-nat.c (update_debug_registers_callback):
	Update comment.
	(amd64_linux_dr_set_control, amd64_linux_dr_set_addr): Use
	iterate_over_lwps.
	(amd64_linux_prepare_to_resume): Pass the lwp's pid to
	i386_debug_reg_state.
	(amd64_linux_new_fork): New function.
	(_initialize_amd64_linux_nat): Install amd64_linux_new_fork as
	linux_nat_new_fork hook, and i386_forget_process as
	linux_nat_forget_process hook.
	* i386-linux-nat.c (update_debug_registers_callback):
	Update comment.
	(amd64_linux_dr_set_control, amd64_linux_dr_set_addr): Use
	iterate_over_lwps.
	(i386_linux_prepare_to_resume): Pass the lwp's pid to
	i386_debug_reg_state.
	(i386_linux_new_fork): New function.
	(_initialize_i386_linux_nat): Install i386_linux_new_fork as
	linux_nat_new_fork hook, and i386_forget_process as
	linux_nat_forget_process hook.
	* i386-nat.c (i386_init_dregs): Delete.
	(i386_inferior_data, struct i386_inferior_data):
	Delete.
	(struct i386_process_info): New.
	(i386_process_list): New global.
	(i386_find_process_pid, i386_add_process, i386_process_info_get):
	New functions.
	(i386_inferior_data_get): Delete.
	(i386_process_info_get): New function.
	(i386_debug_reg_state): New parameter 'pid'.  Reimplement.
	(i386_forget_process): New function.
	(i386_cleanup_dregs): Rewrite.
	(i386_update_inferior_debug_regs, i386_insert_watchpoint)
	(i386_remove_watchpoint, i386_region_ok_for_watchpoint)
	(i386_stopped_data_address, i386_insert_hw_breakpoint)
	(i386_remove_hw_breakpoint): Adjust to pass the current process id
	to i386_debug_reg_state.
	(i386_use_watchpoints): Don't register inferior data.
	* i386-nat.h (i386_debug_reg_state): Add new 'pid' parameter, and
	adjust comment.
	(i386_forget_process): Declare.
	* linux-fork.c (delete_fork): Call linux_nat_forget_process.
	* linux-nat.c (linux_nat_new_fork, linux_nat_forget_process_hook):
	New static globals.
	(linux_child_follow_fork): Don't call linux_nat_new_thread here.
	(add_initial_lwp): New, factored out from ...
	(add_lwp): ... this.  Don't check the number of lwps before
	calling linux_nat_new_thread.
	(linux_nat_iterate_watchpoint_lwps): Delete.
	(linux_nat_attach): Use add_initial_lwp instead of add_lwp.
	(linux_handle_extended_wait): Call the linux_nat_new_fork hook on
	forks and vforks.
	(linux_nat_wait_1): Use add_initial_lwp instead of add_lwp for the
	initial lwp.
	(linux_nat_kill, linux_nat_mourn_inferior): Call
	linux_nat_forget_process.
	(linux_nat_set_new_fork, linux_nat_set_forget_process)
	(linux_nat_forget_process): New functions.
	* linux-nat.h (linux_nat_iterate_watchpoint_lwps_ftype): Delete
	type.
	(linux_nat_iterate_watchpoint_lwps): Delete declaration.
	(linux_nat_new_fork_ftype, linux_nat_forget_process_ftype): New
	types.
	(linux_nat_set_new_fork, linux_nat_set_forget_process)
	(linux_nat_forget_process): New declarations.

	* amd64fbsd-nat.c (super_mourn_inferior): New global.
	(amd64fbsd_mourn_inferior): New function.
	(_initialize_amd64fbsd_nat): Override to_mourn_inferior.
	* windows-nat.c (windows_detach): Call i386_cleanup_dregs.
2013-02-13 14:59:49 +00:00

791 lines
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/* GNU/Linux native-dependent code for debugging multiple forks.
Copyright (C) 2005-2013 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 "arch-utils.h"
#include "inferior.h"
#include "regcache.h"
#include "gdbcmd.h"
#include "infcall.h"
#include "objfiles.h"
#include "gdb_assert.h"
#include "gdb_string.h"
#include "linux-fork.h"
#include "linux-nat.h"
#include "gdbthread.h"
#include "source.h"
#include <sys/ptrace.h>
#include "gdb_wait.h"
#include <sys/param.h>
#include "gdb_dirent.h"
#include <ctype.h>
struct fork_info *fork_list;
static int highest_fork_num;
/* Prevent warning from -Wmissing-prototypes. */
extern void _initialize_linux_fork (void);
/* Fork list data structure: */
struct fork_info
{
struct fork_info *next;
ptid_t ptid;
ptid_t parent_ptid;
int num; /* Convenient handle (GDB fork id). */
struct regcache *savedregs; /* Convenient for info fork, saves
having to actually switch contexts. */
int clobber_regs; /* True if we should restore saved regs. */
off_t *filepos; /* Set of open file descriptors' offsets. */
int maxfd;
};
/* Fork list methods: */
int
forks_exist_p (void)
{
return (fork_list != NULL);
}
/* Add a fork to the internal fork list. */
struct fork_info *
add_fork (pid_t pid)
{
struct fork_info *fp;
if (fork_list == NULL && pid != PIDGET (inferior_ptid))
{
/* Special case -- if this is the first fork in the list
(the list is hitherto empty), and if this new fork is
NOT the current inferior_ptid, then add inferior_ptid
first, as a special zeroeth fork id. */
highest_fork_num = -1;
add_fork (PIDGET (inferior_ptid)); /* safe recursion */
}
fp = XZALLOC (struct fork_info);
fp->ptid = ptid_build (pid, pid, 0);
fp->num = ++highest_fork_num;
fp->next = fork_list;
fork_list = fp;
return fp;
}
static void
free_fork (struct fork_info *fp)
{
/* Notes on step-resume breakpoints: since this is a concern for
threads, let's convince ourselves that it's not a concern for
forks. There are two ways for a fork_info to be created. First,
by the checkpoint command, in which case we're at a gdb prompt
and there can't be any step-resume breakpoint. Second, by a fork
in the user program, in which case we *may* have stepped into the
fork call, but regardless of whether we follow the parent or the
child, we will return to the same place and the step-resume
breakpoint, if any, will take care of itself as usual. And
unlike threads, we do not save a private copy of the step-resume
breakpoint -- so we're OK. */
if (fp)
{
if (fp->savedregs)
regcache_xfree (fp->savedregs);
if (fp->filepos)
xfree (fp->filepos);
xfree (fp);
}
}
static void
delete_fork (ptid_t ptid)
{
struct fork_info *fp, *fpprev;
fpprev = NULL;
linux_nat_forget_process (ptid_get_pid (ptid));
for (fp = fork_list; fp; fpprev = fp, fp = fp->next)
if (ptid_equal (fp->ptid, ptid))
break;
if (!fp)
return;
if (fpprev)
fpprev->next = fp->next;
else
fork_list = fp->next;
free_fork (fp);
/* Special case: if there is now only one process in the list,
and if it is (hopefully!) the current inferior_ptid, then
remove it, leaving the list empty -- we're now down to the
default case of debugging a single process. */
if (fork_list != NULL && fork_list->next == NULL &&
ptid_equal (fork_list->ptid, inferior_ptid))
{
/* Last fork -- delete from list and handle as solo process
(should be a safe recursion). */
delete_fork (inferior_ptid);
}
}
/* Find a fork_info by matching PTID. */
static struct fork_info *
find_fork_ptid (ptid_t ptid)
{
struct fork_info *fp;
for (fp = fork_list; fp; fp = fp->next)
if (ptid_equal (fp->ptid, ptid))
return fp;
return NULL;
}
/* Find a fork_info by matching ID. */
static struct fork_info *
find_fork_id (int num)
{
struct fork_info *fp;
for (fp = fork_list; fp; fp = fp->next)
if (fp->num == num)
return fp;
return NULL;
}
/* Find a fork_info by matching pid. */
extern struct fork_info *
find_fork_pid (pid_t pid)
{
struct fork_info *fp;
for (fp = fork_list; fp; fp = fp->next)
if (pid == ptid_get_pid (fp->ptid))
return fp;
return NULL;
}
static ptid_t
fork_id_to_ptid (int num)
{
struct fork_info *fork = find_fork_id (num);
if (fork)
return fork->ptid;
else
return pid_to_ptid (-1);
}
static void
init_fork_list (void)
{
struct fork_info *fp, *fpnext;
if (!fork_list)
return;
for (fp = fork_list; fp; fp = fpnext)
{
fpnext = fp->next;
free_fork (fp);
}
fork_list = NULL;
}
/* Fork list <-> gdb interface. */
/* Utility function for fork_load/fork_save.
Calls lseek in the (current) inferior process. */
static off_t
call_lseek (int fd, off_t offset, int whence)
{
char exp[80];
snprintf (&exp[0], sizeof (exp), "lseek (%d, %ld, %d)",
fd, (long) offset, whence);
return (off_t) parse_and_eval_long (&exp[0]);
}
/* Load infrun state for the fork PTID. */
static void
fork_load_infrun_state (struct fork_info *fp)
{
extern void nullify_last_target_wait_ptid ();
int i;
linux_nat_switch_fork (fp->ptid);
if (fp->savedregs && fp->clobber_regs)
regcache_cpy (get_current_regcache (), fp->savedregs);
registers_changed ();
reinit_frame_cache ();
stop_pc = regcache_read_pc (get_current_regcache ());
nullify_last_target_wait_ptid ();
/* Now restore the file positions of open file descriptors. */
if (fp->filepos)
{
for (i = 0; i <= fp->maxfd; i++)
if (fp->filepos[i] != (off_t) -1)
call_lseek (i, fp->filepos[i], SEEK_SET);
/* NOTE: I can get away with using SEEK_SET and SEEK_CUR because
this is native-only. If it ever has to be cross, we'll have
to rethink this. */
}
}
/* Save infrun state for the fork PTID.
Exported for use by linux child_follow_fork. */
static void
fork_save_infrun_state (struct fork_info *fp, int clobber_regs)
{
char path[MAXPATHLEN];
struct dirent *de;
DIR *d;
if (fp->savedregs)
regcache_xfree (fp->savedregs);
fp->savedregs = regcache_dup (get_current_regcache ());
fp->clobber_regs = clobber_regs;
if (clobber_regs)
{
/* Now save the 'state' (file position) of all open file descriptors.
Unfortunately fork does not take care of that for us... */
snprintf (path, MAXPATHLEN, "/proc/%ld/fd", (long) PIDGET (fp->ptid));
if ((d = opendir (path)) != NULL)
{
long tmp;
fp->maxfd = 0;
while ((de = readdir (d)) != NULL)
{
/* Count open file descriptors (actually find highest
numbered). */
tmp = strtol (&de->d_name[0], NULL, 10);
if (fp->maxfd < tmp)
fp->maxfd = tmp;
}
/* Allocate array of file positions. */
fp->filepos = xrealloc (fp->filepos,
(fp->maxfd + 1) * sizeof (*fp->filepos));
/* Initialize to -1 (invalid). */
for (tmp = 0; tmp <= fp->maxfd; tmp++)
fp->filepos[tmp] = -1;
/* Now find actual file positions. */
rewinddir (d);
while ((de = readdir (d)) != NULL)
if (isdigit (de->d_name[0]))
{
tmp = strtol (&de->d_name[0], NULL, 10);
fp->filepos[tmp] = call_lseek (tmp, 0, SEEK_CUR);
}
closedir (d);
}
}
}
/* Kill 'em all, let God sort 'em out... */
void
linux_fork_killall (void)
{
/* Walk list and kill every pid. No need to treat the
current inferior_ptid as special (we do not return a
status for it) -- however any process may be a child
or a parent, so may get a SIGCHLD from a previously
killed child. Wait them all out. */
struct fork_info *fp;
pid_t pid, ret;
int status;
for (fp = fork_list; fp; fp = fp->next)
{
pid = PIDGET (fp->ptid);
do {
/* Use SIGKILL instead of PTRACE_KILL because the former works even
if the thread is running, while the later doesn't. */
kill (pid, SIGKILL);
ret = waitpid (pid, &status, 0);
/* We might get a SIGCHLD instead of an exit status. This is
aggravated by the first kill above - a child has just
died. MVS comment cut-and-pasted from linux-nat. */
} while (ret == pid && WIFSTOPPED (status));
}
init_fork_list (); /* Clear list, prepare to start fresh. */
}
/* 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. */
void
linux_fork_mourn_inferior (void)
{
/* Wait just one more time to collect the inferior's exit status.
Do not check whether this succeeds though, since we may be
dealing with a process that we attached to. Such a process will
only report its exit status to its original parent. */
int status;
waitpid (ptid_get_pid (inferior_ptid), &status, 0);
/* OK, presumably inferior_ptid is the one who has exited.
We need to delete that one from the fork_list, and switch
to the next available fork. */
delete_fork (inferior_ptid);
/* There should still be a fork - if there's only one left,
delete_fork won't remove it, because we haven't updated
inferior_ptid yet. */
gdb_assert (fork_list);
fork_load_infrun_state (fork_list);
printf_filtered (_("[Switching to %s]\n"),
target_pid_to_str (inferior_ptid));
/* If there's only one fork, switch back to non-fork mode. */
if (fork_list->next == NULL)
delete_fork (inferior_ptid);
}
/* The current inferior_ptid is being detached, but there are other
viable forks to debug. Detach and delete it and context-switch to
the first available. */
void
linux_fork_detach (char *args, int from_tty)
{
/* OK, inferior_ptid is the one we are detaching from. We need to
delete it from the fork_list, and switch to the next available
fork. */
if (ptrace (PTRACE_DETACH, PIDGET (inferior_ptid), 0, 0))
error (_("Unable to detach %s"), target_pid_to_str (inferior_ptid));
delete_fork (inferior_ptid);
/* There should still be a fork - if there's only one left,
delete_fork won't remove it, because we haven't updated
inferior_ptid yet. */
gdb_assert (fork_list);
fork_load_infrun_state (fork_list);
if (from_tty)
printf_filtered (_("[Switching to %s]\n"),
target_pid_to_str (inferior_ptid));
/* If there's only one fork, switch back to non-fork mode. */
if (fork_list->next == NULL)
delete_fork (inferior_ptid);
}
static void
inferior_call_waitpid_cleanup (void *fp)
{
struct fork_info *oldfp = fp;
if (oldfp)
{
/* Switch back to inferior_ptid. */
remove_breakpoints ();
fork_load_infrun_state (oldfp);
insert_breakpoints ();
}
}
static int
inferior_call_waitpid (ptid_t pptid, int pid)
{
struct objfile *waitpid_objf;
struct value *waitpid_fn = NULL;
struct value *argv[4], *retv;
struct gdbarch *gdbarch = get_current_arch ();
struct fork_info *oldfp = NULL, *newfp = NULL;
struct cleanup *old_cleanup;
int ret = -1;
if (!ptid_equal (pptid, inferior_ptid))
{
/* Switch to pptid. */
oldfp = find_fork_ptid (inferior_ptid);
gdb_assert (oldfp != NULL);
newfp = find_fork_ptid (pptid);
gdb_assert (newfp != NULL);
fork_save_infrun_state (oldfp, 1);
remove_breakpoints ();
fork_load_infrun_state (newfp);
insert_breakpoints ();
}
old_cleanup = make_cleanup (inferior_call_waitpid_cleanup, oldfp);
/* Get the waitpid_fn. */
if (lookup_minimal_symbol ("waitpid", NULL, NULL) != NULL)
waitpid_fn = find_function_in_inferior ("waitpid", &waitpid_objf);
if (!waitpid_fn && lookup_minimal_symbol ("_waitpid", NULL, NULL) != NULL)
waitpid_fn = find_function_in_inferior ("_waitpid", &waitpid_objf);
if (!waitpid_fn)
goto out;
/* Get the argv. */
argv[0] = value_from_longest (builtin_type (gdbarch)->builtin_int, pid);
argv[1] = value_from_pointer (builtin_type (gdbarch)->builtin_data_ptr, 0);
argv[2] = value_from_longest (builtin_type (gdbarch)->builtin_int, 0);
argv[3] = 0;
retv = call_function_by_hand (waitpid_fn, 3, argv);
if (value_as_long (retv) < 0)
goto out;
ret = 0;
out:
do_cleanups (old_cleanup);
return ret;
}
/* Fork list <-> user interface. */
static void
delete_checkpoint_command (char *args, int from_tty)
{
ptid_t ptid, pptid;
struct fork_info *fi;
if (!args || !*args)
error (_("Requires argument (checkpoint id to delete)"));
ptid = fork_id_to_ptid (parse_and_eval_long (args));
if (ptid_equal (ptid, minus_one_ptid))
error (_("No such checkpoint id, %s"), args);
if (ptid_equal (ptid, inferior_ptid))
error (_("\
Please switch to another checkpoint before deleting the current one"));
if (ptrace (PTRACE_KILL, PIDGET (ptid), 0, 0))
error (_("Unable to kill pid %s"), target_pid_to_str (ptid));
fi = find_fork_ptid (ptid);
gdb_assert (fi);
pptid = fi->parent_ptid;
if (from_tty)
printf_filtered (_("Killed %s\n"), target_pid_to_str (ptid));
delete_fork (ptid);
/* If fi->parent_ptid is not a part of lwp but it's a part of checkpoint
list, waitpid the ptid.
If fi->parent_ptid is a part of lwp and it is stoped, waitpid the
ptid. */
if ((!find_thread_ptid (pptid) && find_fork_ptid (pptid))
|| (find_thread_ptid (pptid) && is_stopped (pptid)))
{
if (inferior_call_waitpid (pptid, PIDGET (ptid)))
warning (_("Unable to wait pid %s"), target_pid_to_str (ptid));
}
}
static void
detach_checkpoint_command (char *args, int from_tty)
{
ptid_t ptid;
if (!args || !*args)
error (_("Requires argument (checkpoint id to detach)"));
ptid = fork_id_to_ptid (parse_and_eval_long (args));
if (ptid_equal (ptid, minus_one_ptid))
error (_("No such checkpoint id, %s"), args);
if (ptid_equal (ptid, inferior_ptid))
error (_("\
Please switch to another checkpoint before detaching the current one"));
if (ptrace (PTRACE_DETACH, PIDGET (ptid), 0, 0))
error (_("Unable to detach %s"), target_pid_to_str (ptid));
if (from_tty)
printf_filtered (_("Detached %s\n"), target_pid_to_str (ptid));
delete_fork (ptid);
}
/* Print information about currently known checkpoints. */
static void
info_checkpoints_command (char *arg, int from_tty)
{
struct gdbarch *gdbarch = get_current_arch ();
struct symtab_and_line sal;
struct fork_info *fp;
ULONGEST pc;
int requested = -1;
struct fork_info *printed = NULL;
if (arg && *arg)
requested = (int) parse_and_eval_long (arg);
for (fp = fork_list; fp; fp = fp->next)
{
if (requested > 0 && fp->num != requested)
continue;
printed = fp;
if (ptid_equal (fp->ptid, inferior_ptid))
{
printf_filtered ("* ");
pc = regcache_read_pc (get_current_regcache ());
}
else
{
printf_filtered (" ");
pc = regcache_read_pc (fp->savedregs);
}
printf_filtered ("%d %s", fp->num, target_pid_to_str (fp->ptid));
if (fp->num == 0)
printf_filtered (_(" (main process)"));
printf_filtered (_(" at "));
fputs_filtered (paddress (gdbarch, pc), gdb_stdout);
sal = find_pc_line (pc, 0);
if (sal.symtab)
printf_filtered (_(", file %s"),
symtab_to_filename_for_display (sal.symtab));
if (sal.line)
printf_filtered (_(", line %d"), sal.line);
if (!sal.symtab && !sal.line)
{
struct minimal_symbol *msym;
msym = lookup_minimal_symbol_by_pc (pc);
if (msym)
printf_filtered (", <%s>", SYMBOL_LINKAGE_NAME (msym));
}
putchar_filtered ('\n');
}
if (printed == NULL)
{
if (requested > 0)
printf_filtered (_("No checkpoint number %d.\n"), requested);
else
printf_filtered (_("No checkpoints.\n"));
}
}
/* The PID of the process we're checkpointing. */
static int checkpointing_pid = 0;
int
linux_fork_checkpointing_p (int pid)
{
return (checkpointing_pid == pid);
}
/* Callback for iterate over threads. Used to check whether
the current inferior is multi-threaded. Returns true as soon
as it sees the second thread of the current inferior. */
static int
inf_has_multiple_thread_cb (struct thread_info *tp, void *data)
{
int *count_p = (int *) data;
if (current_inferior ()->pid == ptid_get_pid (tp->ptid))
(*count_p)++;
/* Stop the iteration if multiple threads have been detected. */
return *count_p > 1;
}
/* Return true if the current inferior is multi-threaded. */
static int
inf_has_multiple_threads (void)
{
int count = 0;
iterate_over_threads (inf_has_multiple_thread_cb, &count);
return (count > 1);
}
static void
checkpoint_command (char *args, int from_tty)
{
struct objfile *fork_objf;
struct gdbarch *gdbarch;
struct target_waitstatus last_target_waitstatus;
ptid_t last_target_ptid;
struct value *fork_fn = NULL, *ret;
struct fork_info *fp;
pid_t retpid;
struct cleanup *old_chain;
if (!target_has_execution)
error (_("The program is not being run."));
/* Ensure that the inferior is not multithreaded. */
update_thread_list ();
if (inf_has_multiple_threads ())
error (_("checkpoint: can't checkpoint multiple threads."));
/* Make the inferior fork, record its (and gdb's) state. */
if (lookup_minimal_symbol ("fork", NULL, NULL) != NULL)
fork_fn = find_function_in_inferior ("fork", &fork_objf);
if (!fork_fn)
if (lookup_minimal_symbol ("_fork", NULL, NULL) != NULL)
fork_fn = find_function_in_inferior ("fork", &fork_objf);
if (!fork_fn)
error (_("checkpoint: can't find fork function in inferior."));
gdbarch = get_objfile_arch (fork_objf);
ret = value_from_longest (builtin_type (gdbarch)->builtin_int, 0);
/* Tell linux-nat.c that we're checkpointing this inferior. */
old_chain = make_cleanup_restore_integer (&checkpointing_pid);
checkpointing_pid = PIDGET (inferior_ptid);
ret = call_function_by_hand (fork_fn, 0, &ret);
do_cleanups (old_chain);
if (!ret) /* Probably can't happen. */
error (_("checkpoint: call_function_by_hand returned null."));
retpid = value_as_long (ret);
get_last_target_status (&last_target_ptid, &last_target_waitstatus);
if (from_tty)
{
int parent_pid;
printf_filtered (_("checkpoint: fork returned pid %ld.\n"),
(long) retpid);
if (info_verbose)
{
parent_pid = ptid_get_lwp (last_target_ptid);
if (parent_pid == 0)
parent_pid = ptid_get_pid (last_target_ptid);
printf_filtered (_(" gdb says parent = %ld.\n"),
(long) parent_pid);
}
}
fp = find_fork_pid (retpid);
if (!fp)
error (_("Failed to find new fork"));
fork_save_infrun_state (fp, 1);
fp->parent_ptid = last_target_ptid;
}
static void
linux_fork_context (struct fork_info *newfp, int from_tty)
{
/* Now we attempt to switch processes. */
struct fork_info *oldfp;
gdb_assert (newfp != NULL);
oldfp = find_fork_ptid (inferior_ptid);
gdb_assert (oldfp != NULL);
fork_save_infrun_state (oldfp, 1);
remove_breakpoints ();
fork_load_infrun_state (newfp);
insert_breakpoints ();
printf_filtered (_("Switching to %s\n"),
target_pid_to_str (inferior_ptid));
print_stack_frame (get_selected_frame (NULL), 1, SRC_AND_LOC);
}
/* Switch inferior process (checkpoint) context, by checkpoint id. */
static void
restart_command (char *args, int from_tty)
{
struct fork_info *fp;
if (!args || !*args)
error (_("Requires argument (checkpoint id to restart)"));
if ((fp = find_fork_id (parse_and_eval_long (args))) == NULL)
error (_("Not found: checkpoint id %s"), args);
linux_fork_context (fp, from_tty);
}
void
_initialize_linux_fork (void)
{
init_fork_list ();
/* Checkpoint command: create a fork of the inferior process
and set it aside for later debugging. */
add_com ("checkpoint", class_obscure, checkpoint_command, _("\
Fork a duplicate process (experimental)."));
/* Restart command: restore the context of a specified checkpoint
process. */
add_com ("restart", class_obscure, restart_command, _("\
restart <n>: restore program context from a checkpoint.\n\
Argument 'n' is checkpoint ID, as displayed by 'info checkpoints'."));
/* Delete checkpoint command: kill the process and remove it from
the fork list. */
add_cmd ("checkpoint", class_obscure, delete_checkpoint_command, _("\
Delete a checkpoint (experimental)."),
&deletelist);
/* Detach checkpoint command: release the process to run independently,
and remove it from the fork list. */
add_cmd ("checkpoint", class_obscure, detach_checkpoint_command, _("\
Detach from a checkpoint (experimental)."),
&detachlist);
/* Info checkpoints command: list all forks/checkpoints
currently under gdb's control. */
add_info ("checkpoints", info_checkpoints_command,
_("IDs of currently known checkpoints."));
}
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