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binutils-gdb/gdb/linux-fork.c
Pedro Alves 7022349d5c Stop assuming no-debug-info functions return int 
The fact that GDB defaults to assuming that functions return int, when
it has no debug info for the function has been a recurring source of
user confusion.  Recently this came up on the errno pretty printer
discussions.  Shortly after, it came up again on IRC, with someone
wondering why does getenv() in GDB return a negative int:

  (gdb) p getenv("PATH")
  $1 = -6185

This question (with s/getenv/random-other-C-runtime-function) is a FAQ
on IRC.

The reason for the above is:

 (gdb) p getenv
 $2 = {<text variable, no debug info>} 0x7ffff7751d80 <getenv>
 (gdb) ptype getenv
 type = int ()

... which means that GDB truncated the 64-bit pointer that is actually
returned from getent to 32-bit, and then sign-extended it:

 (gdb) p /x -6185
 $6 = 0xffffe7d7

The workaround is to cast the function to the right type, like:

 (gdb) p ((char *(*) (const char *)) getenv) ("PATH")
 $3 = 0x7fffffffe7d7 "/usr/local/bin:/"...

IMO, we should do better than this.

I see the "assume-int" issue the same way I see printing bogus values
for optimized-out variables instead of "<optimized out>" -- I'd much
rather that the debugger tells me "I don't know" and tells me how to
fix it than showing me bogus misleading results, making me go around
tilting at windmills.

If GDB prints a signed integer when you're expecting a pointer or
aggregate, you at least have some sense that something is off, but
consider the case of the function actually returning a 64-bit integer.
For example, compile this without debug info:

 unsigned long long
 function ()
 {
   return 0x7fffffffffffffff;
 }

Currently, with pristine GDB, you get:

 (gdb) p function ()
 $1 = -1                      # incorrect
 (gdb) p /x function ()
 $2 = 0xffffffff              # incorrect

maybe after spending a few hours debugging you suspect something is
wrong with that -1, and do:

 (gdb) ptype function
 type = int ()

and maybe, just maybe, you realize that the function actually returns
unsigned long long.  And you try to fix it with:

(gdb) p /x (unsigned long long) function ()
 $3 = 0xffffffffffffffff      # incorrect

... which still produces the wrong result, because GDB simply applied
int to unsigned long long conversion.  Meaning, it sign-extended the
integer that it extracted from the return of the function, to 64-bits.

and then maybe, after asking around on IRC, you realize you have to
cast the function to a pointer of the right type, and call that.  It
won't be easy, but after a few missteps, you'll get to it:

.....  (gdb) p /x ((unsigned long long(*) ()) function) ()
 $666 = 0x7fffffffffffffff             # finally! :-)


So to improve on the user experience, this patch does the following
(interrelated) things:

 - makes no-debug-info functions no longer default to "int" as return
   type.  Instead, they're left with NULL/"<unknown return type>"
   return type.

    (gdb) ptype getenv
    type = <unknown return type> ()

 - makes calling a function with unknown return type an error.

    (gdb) p getenv ("PATH")
    'getenv' has unknown return type; cast the call to its declared return type

 - and then to make it easier to call the function, makes it possible
   to _only_ cast the return of the function to the right type,
   instead of having to cast the function to a function pointer:

    (gdb) p (char *) getenv ("PATH")                      # now Just Works
    $3 = 0x7fffffffe7d7 "/usr/local/bin:/"...

    (gdb) p ((char *(*) (const char *)) getenv) ("PATH")  # continues working
    $4 = 0x7fffffffe7d7 "/usr/local/bin:/"...

   I.e., it makes GDB default the function's return type to the type
   of the cast, and the function's parameters to the type of the
   arguments passed down.

After this patch, here's what you'll get for the "unsigned long long"
example above:

 (gdb) p function ()
 'function' has unknown return type; cast the call to its declared return type
 (gdb) p /x (unsigned long long) function ()
 $4 = 0x7fffffffffffffff     # correct!

Note that while with "print" GDB shows the name of the function that
has the problem:

  (gdb) p getenv ("PATH")
  'getenv' has unknown return type; cast the call to its declared return type

which can by handy in more complicated expressions, "ptype" does not:

  (gdb) ptype getenv ("PATH")
  function has unknown return type; cast the call to its declared return type

This will be fixed in the next patch.

gdb/ChangeLog:
2017-09-04  Pedro Alves  <palves@redhat.com>

	* ada-lang.c (ada_evaluate_subexp) <TYPE_CODE_FUNC>: Don't handle
	TYPE_GNU_IFUNC specially here.  Throw error if return type is
	unknown.
	* ada-typeprint.c (print_func_type): Handle functions with unknown
	return type.
	* c-typeprint.c (c_type_print_base): Handle functions and methods
	with unknown return type.
	* compile/compile-c-symbols.c (convert_symbol_bmsym)
	<mst_text_gnu_ifunc>: Use nodebug_text_gnu_ifunc_symbol.
	* compile/compile-c-types.c: Include "objfiles.h".
	(convert_func): For functions with unknown return type, warn and
	default to int.
	* compile/compile-object-run.c (compile_object_run): Adjust call
	to call_function_by_hand_dummy.
	* elfread.c (elf_gnu_ifunc_resolve_addr): Adjust call to
	call_function_by_hand.
	* eval.c (evaluate_subexp_standard): Adjust calls to
	call_function_by_hand.  Handle functions and methods with unknown
	return type.  Pass expect_type to call_function_by_hand.
	* f-typeprint.c (f_type_print_base): Handle functions with unknown
	return type.
	* gcore.c (call_target_sbrk): Adjust call to
	call_function_by_hand.
	* gdbtypes.c (objfile_type): Leave nodebug text symbol with NULL
	return type instead of int.  Make nodebug_text_gnu_ifunc_symbol be
	an integer address type instead of nodebug.
	* guile/scm-value.c (gdbscm_value_call): Adjust call to
	call_function_by_hand.
	* infcall.c (error_call_unknown_return_type): New function.
	(call_function_by_hand): New "default_return_type" parameter.
	Pass it down.
	(call_function_by_hand_dummy): New "default_return_type"
	parameter.  Use it instead of defaulting to int.  If there's no
	default and the return type is unknown, throw an error.  If
	there's a default return type, and the called function has no
	debug info, then assume the function is prototyped.
	* infcall.h (call_function_by_hand, call_function_by_hand_dummy):
	New "default_return_type" parameter.
	(error_call_unknown_return_type): New declaration.
	* linux-fork.c (call_lseek): Cast return type of lseek.
	(inferior_call_waitpid, checkpoint_command): Adjust calls to
	call_function_by_hand.
	* linux-tdep.c (linux_infcall_mmap, linux_infcall_munmap): Adjust
	calls to call_function_by_hand.
	* m2-typeprint.c (m2_procedure): Handle functions with unknown
	return type.
	* objc-lang.c (lookup_objc_class, lookup_child_selector)
	(value_nsstring, print_object_command): Adjust calls to
	call_function_by_hand.
	* p-typeprint.c (pascal_type_print_varspec_prefix): Handle
	functions with unknown return type.
	(pascal_type_print_func_varspec_suffix): New function.
	(pascal_type_print_varspec_suffix) <TYPE_CODE_FUNC,
	TYPE_CODE_METHOD>: Use it.
	* python/py-value.c (valpy_call): Adjust call to
	call_function_by_hand.
	* rust-lang.c (rust_evaluate_funcall): Adjust call to
	call_function_by_hand.
	* valarith.c (value_x_binop, value_x_unop): Adjust calls to
	call_function_by_hand.
	* valops.c (value_allocate_space_in_inferior): Adjust call to
	call_function_by_hand.
	* typeprint.c (type_print_unknown_return_type): New function.
	* typeprint.h (type_print_unknown_return_type): New declaration.

gdb/testsuite/ChangeLog:
2017-09-04  Pedro Alves  <palves@redhat.com>

	* gdb.base/break-main-file-remove-fail.exp (test_remove_bp): Cast
	return type of munmap in infcall.
	* gdb.base/break-probes.exp: Cast return type of foo in infcall.
	* gdb.base/checkpoint.exp: Simplify using for loop.  Cast return
	type of ftell in infcall.
	* gdb.base/dprintf-detach.exp (dprintf_detach_test): Cast return
	type of getpid in infcall.
	* gdb.base/infcall-exec.exp: Cast return type of execlp in
	infcall.
	* gdb.base/info-os.exp: Cast return type of getpid in infcall.
	Bail on failure to extract the pid.
	* gdb.base/nodebug.c: #include <stdint.h>.
	(multf, multf_noproto, mult, mult_noproto, add8, add8_noproto):
	New functions.
	* gdb.base/nodebug.exp (test_call_promotion): New procedure.
	Change expected output of print/whatis/ptype with functions with
	no debug info.  Test all supported languages.  Call
	test_call_promotion.
	* gdb.compile/compile.exp: Adjust expected output to expect
	warning.
	* gdb.threads/siginfo-threads.exp: Likewise.
2017-09-04 20:21:13 +01:00

818 lines
22 KiB
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/* GNU/Linux native-dependent code for debugging multiple forks.
Copyright (C) 2005-2017 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 "infrun.h"
#include "regcache.h"
#include "gdbcmd.h"
#include "infcall.h"
#include "objfiles.h"
#include "linux-fork.h"
#include "linux-nat.h"
#include "gdbthread.h"
#include "source.h"
#include "nat/gdb_ptrace.h"
#include "gdb_wait.h"
#include <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);
}
/* Return the last fork in the list. */
static struct fork_info *
find_last_fork (void)
{
struct fork_info *last;
if (fork_list == NULL)
return NULL;
for (last = fork_list; last->next != NULL; last = last->next)
;
return last;
}
/* 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 != ptid_get_pid (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 (ptid_get_pid (inferior_ptid)); /* safe recursion */
}
fp = XCNEW (struct fork_info);
fp->ptid = ptid_build (pid, pid, 0);
fp->num = ++highest_fork_num;
if (fork_list == NULL)
fork_list = fp;
else
{
struct fork_info *last = find_last_fork ();
last->next = 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), "(long) 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[PATH_MAX];
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, PATH_MAX, "/proc/%ld/fd",
(long) ptid_get_pid (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 = XRESIZEVEC (off_t, fp->filepos, fp->maxfd + 1);
/* 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 = ptid_get_pid (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)
{
struct fork_info *last;
int status;
/* 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. */
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);
last = find_last_fork ();
fork_load_infrun_state (last);
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 (const 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, ptid_get_pid (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 = (struct fork_info *) 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).minsym != NULL)
waitpid_fn = find_function_in_inferior ("waitpid", &waitpid_objf);
if (!waitpid_fn
&& lookup_minimal_symbol ("_waitpid", NULL, NULL).minsym != 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, NULL, 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, ptid_get_pid (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, ptid_get_pid (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, ptid_get_pid (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 bound_minimal_symbol msym;
msym = lookup_minimal_symbol_by_pc (pc);
if (msym.minsym)
printf_filtered (", <%s>", MSYMBOL_LINKAGE_NAME (msym.minsym));
}
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;
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).minsym != NULL)
fork_fn = find_function_in_inferior ("fork", &fork_objf);
if (!fork_fn)
if (lookup_minimal_symbol ("_fork", NULL, NULL).minsym != 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. */
{
scoped_restore save_pid
= make_scoped_restore (&checkpointing_pid, ptid_get_pid (inferior_ptid));
ret = call_function_by_hand (fork_fn, NULL, 0, &ret);
}
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);
fp = find_fork_pid (retpid);
if (from_tty)
{
int parent_pid;
printf_filtered (_("checkpoint %d: fork returned pid %ld.\n"),
fp != NULL ? fp->num : -1, (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);
}
}
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, 1);
}
/* 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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