Merge remote-tracking branch 'kselftest/next'
[karo-tx-linux.git] / fs / coredump.c
1 #include <linux/slab.h>
2 #include <linux/file.h>
3 #include <linux/fdtable.h>
4 #include <linux/mm.h>
5 #include <linux/stat.h>
6 #include <linux/fcntl.h>
7 #include <linux/swap.h>
8 #include <linux/string.h>
9 #include <linux/init.h>
10 #include <linux/pagemap.h>
11 #include <linux/perf_event.h>
12 #include <linux/highmem.h>
13 #include <linux/spinlock.h>
14 #include <linux/key.h>
15 #include <linux/personality.h>
16 #include <linux/binfmts.h>
17 #include <linux/coredump.h>
18 #include <linux/utsname.h>
19 #include <linux/pid_namespace.h>
20 #include <linux/module.h>
21 #include <linux/namei.h>
22 #include <linux/mount.h>
23 #include <linux/security.h>
24 #include <linux/syscalls.h>
25 #include <linux/tsacct_kern.h>
26 #include <linux/cn_proc.h>
27 #include <linux/audit.h>
28 #include <linux/tracehook.h>
29 #include <linux/kmod.h>
30 #include <linux/fsnotify.h>
31 #include <linux/fs_struct.h>
32 #include <linux/pipe_fs_i.h>
33 #include <linux/oom.h>
34 #include <linux/compat.h>
35
36 #include <asm/uaccess.h>
37 #include <asm/mmu_context.h>
38 #include <asm/tlb.h>
39 #include <asm/exec.h>
40
41 #include <trace/events/task.h>
42 #include "internal.h"
43
44 #include <trace/events/sched.h>
45
46 int core_uses_pid;
47 unsigned int core_pipe_limit;
48 char core_pattern[CORENAME_MAX_SIZE] = "core";
49 static int core_name_size = CORENAME_MAX_SIZE;
50
51 struct core_name {
52         char *corename;
53         int used, size;
54 };
55
56 /* The maximal length of core_pattern is also specified in sysctl.c */
57
58 static int expand_corename(struct core_name *cn, int size)
59 {
60         char *corename = krealloc(cn->corename, size, GFP_KERNEL);
61
62         if (!corename)
63                 return -ENOMEM;
64
65         if (size > core_name_size) /* racy but harmless */
66                 core_name_size = size;
67
68         cn->size = ksize(corename);
69         cn->corename = corename;
70         return 0;
71 }
72
73 static __printf(2, 0) int cn_vprintf(struct core_name *cn, const char *fmt,
74                                      va_list arg)
75 {
76         int free, need;
77         va_list arg_copy;
78
79 again:
80         free = cn->size - cn->used;
81
82         va_copy(arg_copy, arg);
83         need = vsnprintf(cn->corename + cn->used, free, fmt, arg_copy);
84         va_end(arg_copy);
85
86         if (need < free) {
87                 cn->used += need;
88                 return 0;
89         }
90
91         if (!expand_corename(cn, cn->size + need - free + 1))
92                 goto again;
93
94         return -ENOMEM;
95 }
96
97 static __printf(2, 3) int cn_printf(struct core_name *cn, const char *fmt, ...)
98 {
99         va_list arg;
100         int ret;
101
102         va_start(arg, fmt);
103         ret = cn_vprintf(cn, fmt, arg);
104         va_end(arg);
105
106         return ret;
107 }
108
109 static __printf(2, 3)
110 int cn_esc_printf(struct core_name *cn, const char *fmt, ...)
111 {
112         int cur = cn->used;
113         va_list arg;
114         int ret;
115
116         va_start(arg, fmt);
117         ret = cn_vprintf(cn, fmt, arg);
118         va_end(arg);
119
120         for (; cur < cn->used; ++cur) {
121                 if (cn->corename[cur] == '/')
122                         cn->corename[cur] = '!';
123         }
124         return ret;
125 }
126
127 static int cn_print_exe_file(struct core_name *cn)
128 {
129         struct file *exe_file;
130         char *pathbuf, *path;
131         int ret;
132
133         exe_file = get_mm_exe_file(current->mm);
134         if (!exe_file)
135                 return cn_esc_printf(cn, "%s (path unknown)", current->comm);
136
137         pathbuf = kmalloc(PATH_MAX, GFP_TEMPORARY);
138         if (!pathbuf) {
139                 ret = -ENOMEM;
140                 goto put_exe_file;
141         }
142
143         path = file_path(exe_file, pathbuf, PATH_MAX);
144         if (IS_ERR(path)) {
145                 ret = PTR_ERR(path);
146                 goto free_buf;
147         }
148
149         ret = cn_esc_printf(cn, "%s", path);
150
151 free_buf:
152         kfree(pathbuf);
153 put_exe_file:
154         fput(exe_file);
155         return ret;
156 }
157
158 /* format_corename will inspect the pattern parameter, and output a
159  * name into corename, which must have space for at least
160  * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
161  */
162 static int format_corename(struct core_name *cn, struct coredump_params *cprm)
163 {
164         const struct cred *cred = current_cred();
165         const char *pat_ptr = core_pattern;
166         int ispipe = (*pat_ptr == '|');
167         int pid_in_pattern = 0;
168         int err = 0;
169
170         cn->used = 0;
171         cn->corename = NULL;
172         if (expand_corename(cn, core_name_size))
173                 return -ENOMEM;
174         cn->corename[0] = '\0';
175
176         if (ispipe)
177                 ++pat_ptr;
178
179         /* Repeat as long as we have more pattern to process and more output
180            space */
181         while (*pat_ptr) {
182                 if (*pat_ptr != '%') {
183                         err = cn_printf(cn, "%c", *pat_ptr++);
184                 } else {
185                         switch (*++pat_ptr) {
186                         /* single % at the end, drop that */
187                         case 0:
188                                 goto out;
189                         /* Double percent, output one percent */
190                         case '%':
191                                 err = cn_printf(cn, "%c", '%');
192                                 break;
193                         /* pid */
194                         case 'p':
195                                 pid_in_pattern = 1;
196                                 err = cn_printf(cn, "%d",
197                                               task_tgid_vnr(current));
198                                 break;
199                         /* global pid */
200                         case 'P':
201                                 err = cn_printf(cn, "%d",
202                                               task_tgid_nr(current));
203                                 break;
204                         case 'i':
205                                 err = cn_printf(cn, "%d",
206                                               task_pid_vnr(current));
207                                 break;
208                         case 'I':
209                                 err = cn_printf(cn, "%d",
210                                               task_pid_nr(current));
211                                 break;
212                         /* uid */
213                         case 'u':
214                                 err = cn_printf(cn, "%u",
215                                                 from_kuid(&init_user_ns,
216                                                           cred->uid));
217                                 break;
218                         /* gid */
219                         case 'g':
220                                 err = cn_printf(cn, "%u",
221                                                 from_kgid(&init_user_ns,
222                                                           cred->gid));
223                                 break;
224                         case 'd':
225                                 err = cn_printf(cn, "%d",
226                                         __get_dumpable(cprm->mm_flags));
227                                 break;
228                         /* signal that caused the coredump */
229                         case 's':
230                                 err = cn_printf(cn, "%d",
231                                                 cprm->siginfo->si_signo);
232                                 break;
233                         /* UNIX time of coredump */
234                         case 't': {
235                                 struct timeval tv;
236                                 do_gettimeofday(&tv);
237                                 err = cn_printf(cn, "%lu", tv.tv_sec);
238                                 break;
239                         }
240                         /* hostname */
241                         case 'h':
242                                 down_read(&uts_sem);
243                                 err = cn_esc_printf(cn, "%s",
244                                               utsname()->nodename);
245                                 up_read(&uts_sem);
246                                 break;
247                         /* executable */
248                         case 'e':
249                                 err = cn_esc_printf(cn, "%s", current->comm);
250                                 break;
251                         case 'E':
252                                 err = cn_print_exe_file(cn);
253                                 break;
254                         /* core limit size */
255                         case 'c':
256                                 err = cn_printf(cn, "%lu",
257                                               rlimit(RLIMIT_CORE));
258                                 break;
259                         default:
260                                 break;
261                         }
262                         ++pat_ptr;
263                 }
264
265                 if (err)
266                         return err;
267         }
268
269 out:
270         /* Backward compatibility with core_uses_pid:
271          *
272          * If core_pattern does not include a %p (as is the default)
273          * and core_uses_pid is set, then .%pid will be appended to
274          * the filename. Do not do this for piped commands. */
275         if (!ispipe && !pid_in_pattern && core_uses_pid) {
276                 err = cn_printf(cn, ".%d", task_tgid_vnr(current));
277                 if (err)
278                         return err;
279         }
280         return ispipe;
281 }
282
283 static int zap_process(struct task_struct *start, int exit_code)
284 {
285         struct task_struct *t;
286         int nr = 0;
287
288         start->signal->group_exit_code = exit_code;
289         start->signal->group_stop_count = 0;
290
291         t = start;
292         do {
293                 task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
294                 if (t != current && t->mm) {
295                         sigaddset(&t->pending.signal, SIGKILL);
296                         signal_wake_up(t, 1);
297                         nr++;
298                 }
299         } while_each_thread(start, t);
300
301         return nr;
302 }
303
304 static int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
305                         struct core_state *core_state, int exit_code)
306 {
307         struct task_struct *g, *p;
308         unsigned long flags;
309         int nr = -EAGAIN;
310
311         spin_lock_irq(&tsk->sighand->siglock);
312         if (!signal_group_exit(tsk->signal)) {
313                 mm->core_state = core_state;
314                 nr = zap_process(tsk, exit_code);
315                 tsk->signal->group_exit_task = tsk;
316                 /* ignore all signals except SIGKILL, see prepare_signal() */
317                 tsk->signal->flags = SIGNAL_GROUP_COREDUMP;
318                 clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
319         }
320         spin_unlock_irq(&tsk->sighand->siglock);
321         if (unlikely(nr < 0))
322                 return nr;
323
324         tsk->flags |= PF_DUMPCORE;
325         if (atomic_read(&mm->mm_users) == nr + 1)
326                 goto done;
327         /*
328          * We should find and kill all tasks which use this mm, and we should
329          * count them correctly into ->nr_threads. We don't take tasklist
330          * lock, but this is safe wrt:
331          *
332          * fork:
333          *      None of sub-threads can fork after zap_process(leader). All
334          *      processes which were created before this point should be
335          *      visible to zap_threads() because copy_process() adds the new
336          *      process to the tail of init_task.tasks list, and lock/unlock
337          *      of ->siglock provides a memory barrier.
338          *
339          * do_exit:
340          *      The caller holds mm->mmap_sem. This means that the task which
341          *      uses this mm can't pass exit_mm(), so it can't exit or clear
342          *      its ->mm.
343          *
344          * de_thread:
345          *      It does list_replace_rcu(&leader->tasks, &current->tasks),
346          *      we must see either old or new leader, this does not matter.
347          *      However, it can change p->sighand, so lock_task_sighand(p)
348          *      must be used. Since p->mm != NULL and we hold ->mmap_sem
349          *      it can't fail.
350          *
351          *      Note also that "g" can be the old leader with ->mm == NULL
352          *      and already unhashed and thus removed from ->thread_group.
353          *      This is OK, __unhash_process()->list_del_rcu() does not
354          *      clear the ->next pointer, we will find the new leader via
355          *      next_thread().
356          */
357         rcu_read_lock();
358         for_each_process(g) {
359                 if (g == tsk->group_leader)
360                         continue;
361                 if (g->flags & PF_KTHREAD)
362                         continue;
363                 p = g;
364                 do {
365                         if (p->mm) {
366                                 if (unlikely(p->mm == mm)) {
367                                         lock_task_sighand(p, &flags);
368                                         nr += zap_process(p, exit_code);
369                                         p->signal->flags = SIGNAL_GROUP_EXIT;
370                                         unlock_task_sighand(p, &flags);
371                                 }
372                                 break;
373                         }
374                 } while_each_thread(g, p);
375         }
376         rcu_read_unlock();
377 done:
378         atomic_set(&core_state->nr_threads, nr);
379         return nr;
380 }
381
382 static int coredump_wait(int exit_code, struct core_state *core_state)
383 {
384         struct task_struct *tsk = current;
385         struct mm_struct *mm = tsk->mm;
386         int core_waiters = -EBUSY;
387
388         init_completion(&core_state->startup);
389         core_state->dumper.task = tsk;
390         core_state->dumper.next = NULL;
391
392         down_write(&mm->mmap_sem);
393         if (!mm->core_state)
394                 core_waiters = zap_threads(tsk, mm, core_state, exit_code);
395         up_write(&mm->mmap_sem);
396
397         if (core_waiters > 0) {
398                 struct core_thread *ptr;
399
400                 wait_for_completion(&core_state->startup);
401                 /*
402                  * Wait for all the threads to become inactive, so that
403                  * all the thread context (extended register state, like
404                  * fpu etc) gets copied to the memory.
405                  */
406                 ptr = core_state->dumper.next;
407                 while (ptr != NULL) {
408                         wait_task_inactive(ptr->task, 0);
409                         ptr = ptr->next;
410                 }
411         }
412
413         return core_waiters;
414 }
415
416 static void coredump_finish(struct mm_struct *mm, bool core_dumped)
417 {
418         struct core_thread *curr, *next;
419         struct task_struct *task;
420
421         spin_lock_irq(&current->sighand->siglock);
422         if (core_dumped && !__fatal_signal_pending(current))
423                 current->signal->group_exit_code |= 0x80;
424         current->signal->group_exit_task = NULL;
425         current->signal->flags = SIGNAL_GROUP_EXIT;
426         spin_unlock_irq(&current->sighand->siglock);
427
428         next = mm->core_state->dumper.next;
429         while ((curr = next) != NULL) {
430                 next = curr->next;
431                 task = curr->task;
432                 /*
433                  * see exit_mm(), curr->task must not see
434                  * ->task == NULL before we read ->next.
435                  */
436                 smp_mb();
437                 curr->task = NULL;
438                 wake_up_process(task);
439         }
440
441         mm->core_state = NULL;
442 }
443
444 static bool dump_interrupted(void)
445 {
446         /*
447          * SIGKILL or freezing() interrupt the coredumping. Perhaps we
448          * can do try_to_freeze() and check __fatal_signal_pending(),
449          * but then we need to teach dump_write() to restart and clear
450          * TIF_SIGPENDING.
451          */
452         return signal_pending(current);
453 }
454
455 static void wait_for_dump_helpers(struct file *file)
456 {
457         struct pipe_inode_info *pipe = file->private_data;
458
459         pipe_lock(pipe);
460         pipe->readers++;
461         pipe->writers--;
462         wake_up_interruptible_sync(&pipe->wait);
463         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
464         pipe_unlock(pipe);
465
466         /*
467          * We actually want wait_event_freezable() but then we need
468          * to clear TIF_SIGPENDING and improve dump_interrupted().
469          */
470         wait_event_interruptible(pipe->wait, pipe->readers == 1);
471
472         pipe_lock(pipe);
473         pipe->readers--;
474         pipe->writers++;
475         pipe_unlock(pipe);
476 }
477
478 /*
479  * umh_pipe_setup
480  * helper function to customize the process used
481  * to collect the core in userspace.  Specifically
482  * it sets up a pipe and installs it as fd 0 (stdin)
483  * for the process.  Returns 0 on success, or
484  * PTR_ERR on failure.
485  * Note that it also sets the core limit to 1.  This
486  * is a special value that we use to trap recursive
487  * core dumps
488  */
489 static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
490 {
491         struct file *files[2];
492         struct coredump_params *cp = (struct coredump_params *)info->data;
493         int err = create_pipe_files(files, 0);
494         if (err)
495                 return err;
496
497         cp->file = files[1];
498
499         err = replace_fd(0, files[0], 0);
500         fput(files[0]);
501         /* and disallow core files too */
502         current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
503
504         return err;
505 }
506
507 void do_coredump(const siginfo_t *siginfo)
508 {
509         struct core_state core_state;
510         struct core_name cn;
511         struct mm_struct *mm = current->mm;
512         struct linux_binfmt * binfmt;
513         const struct cred *old_cred;
514         struct cred *cred;
515         int retval = 0;
516         int ispipe;
517         struct files_struct *displaced;
518         /* require nonrelative corefile path and be extra careful */
519         bool need_suid_safe = false;
520         bool core_dumped = false;
521         static atomic_t core_dump_count = ATOMIC_INIT(0);
522         struct coredump_params cprm = {
523                 .siginfo = siginfo,
524                 .regs = signal_pt_regs(),
525                 .limit = rlimit(RLIMIT_CORE),
526                 /*
527                  * We must use the same mm->flags while dumping core to avoid
528                  * inconsistency of bit flags, since this flag is not protected
529                  * by any locks.
530                  */
531                 .mm_flags = mm->flags,
532         };
533
534         audit_core_dumps(siginfo->si_signo);
535
536         binfmt = mm->binfmt;
537         if (!binfmt || !binfmt->core_dump)
538                 goto fail;
539         if (!__get_dumpable(cprm.mm_flags))
540                 goto fail;
541
542         cred = prepare_creds();
543         if (!cred)
544                 goto fail;
545         /*
546          * We cannot trust fsuid as being the "true" uid of the process
547          * nor do we know its entire history. We only know it was tainted
548          * so we dump it as root in mode 2, and only into a controlled
549          * environment (pipe handler or fully qualified path).
550          */
551         if (__get_dumpable(cprm.mm_flags) == SUID_DUMP_ROOT) {
552                 /* Setuid core dump mode */
553                 cred->fsuid = GLOBAL_ROOT_UID;  /* Dump root private */
554                 need_suid_safe = true;
555         }
556
557         retval = coredump_wait(siginfo->si_signo, &core_state);
558         if (retval < 0)
559                 goto fail_creds;
560
561         old_cred = override_creds(cred);
562
563         ispipe = format_corename(&cn, &cprm);
564
565         if (ispipe) {
566                 int dump_count;
567                 char **helper_argv;
568                 struct subprocess_info *sub_info;
569
570                 if (ispipe < 0) {
571                         printk(KERN_WARNING "format_corename failed\n");
572                         printk(KERN_WARNING "Aborting core\n");
573                         goto fail_unlock;
574                 }
575
576                 if (cprm.limit == 1) {
577                         /* See umh_pipe_setup() which sets RLIMIT_CORE = 1.
578                          *
579                          * Normally core limits are irrelevant to pipes, since
580                          * we're not writing to the file system, but we use
581                          * cprm.limit of 1 here as a special value, this is a
582                          * consistent way to catch recursive crashes.
583                          * We can still crash if the core_pattern binary sets
584                          * RLIM_CORE = !1, but it runs as root, and can do
585                          * lots of stupid things.
586                          *
587                          * Note that we use task_tgid_vnr here to grab the pid
588                          * of the process group leader.  That way we get the
589                          * right pid if a thread in a multi-threaded
590                          * core_pattern process dies.
591                          */
592                         printk(KERN_WARNING
593                                 "Process %d(%s) has RLIMIT_CORE set to 1\n",
594                                 task_tgid_vnr(current), current->comm);
595                         printk(KERN_WARNING "Aborting core\n");
596                         goto fail_unlock;
597                 }
598                 cprm.limit = RLIM_INFINITY;
599
600                 dump_count = atomic_inc_return(&core_dump_count);
601                 if (core_pipe_limit && (core_pipe_limit < dump_count)) {
602                         printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n",
603                                task_tgid_vnr(current), current->comm);
604                         printk(KERN_WARNING "Skipping core dump\n");
605                         goto fail_dropcount;
606                 }
607
608                 helper_argv = argv_split(GFP_KERNEL, cn.corename, NULL);
609                 if (!helper_argv) {
610                         printk(KERN_WARNING "%s failed to allocate memory\n",
611                                __func__);
612                         goto fail_dropcount;
613                 }
614
615                 retval = -ENOMEM;
616                 sub_info = call_usermodehelper_setup(helper_argv[0],
617                                                 helper_argv, NULL, GFP_KERNEL,
618                                                 umh_pipe_setup, NULL, &cprm);
619                 if (sub_info)
620                         retval = call_usermodehelper_exec(sub_info,
621                                                           UMH_WAIT_EXEC);
622
623                 argv_free(helper_argv);
624                 if (retval) {
625                         printk(KERN_INFO "Core dump to |%s pipe failed\n",
626                                cn.corename);
627                         goto close_fail;
628                 }
629         } else {
630                 struct inode *inode;
631
632                 if (cprm.limit < binfmt->min_coredump)
633                         goto fail_unlock;
634
635                 if (need_suid_safe && cn.corename[0] != '/') {
636                         printk(KERN_WARNING "Pid %d(%s) can only dump core "\
637                                 "to fully qualified path!\n",
638                                 task_tgid_vnr(current), current->comm);
639                         printk(KERN_WARNING "Skipping core dump\n");
640                         goto fail_unlock;
641                 }
642
643                 /*
644                  * Unlink the file if it exists unless this is a SUID
645                  * binary - in that case, we're running around with root
646                  * privs and don't want to unlink another user's coredump.
647                  */
648                 if (!need_suid_safe) {
649                         mm_segment_t old_fs;
650
651                         old_fs = get_fs();
652                         set_fs(KERNEL_DS);
653                         /*
654                          * If it doesn't exist, that's fine. If there's some
655                          * other problem, we'll catch it at the filp_open().
656                          */
657                         (void) sys_unlink((const char __user *)cn.corename);
658                         set_fs(old_fs);
659                 }
660
661                 /*
662                  * There is a race between unlinking and creating the
663                  * file, but if that causes an EEXIST here, that's
664                  * fine - another process raced with us while creating
665                  * the corefile, and the other process won. To userspace,
666                  * what matters is that at least one of the two processes
667                  * writes its coredump successfully, not which one.
668                  */
669                 cprm.file = filp_open(cn.corename,
670                                  O_CREAT | 2 | O_NOFOLLOW |
671                                  O_LARGEFILE | O_EXCL,
672                                  0600);
673                 if (IS_ERR(cprm.file))
674                         goto fail_unlock;
675
676                 inode = file_inode(cprm.file);
677                 if (inode->i_nlink > 1)
678                         goto close_fail;
679                 if (d_unhashed(cprm.file->f_path.dentry))
680                         goto close_fail;
681                 /*
682                  * AK: actually i see no reason to not allow this for named
683                  * pipes etc, but keep the previous behaviour for now.
684                  */
685                 if (!S_ISREG(inode->i_mode))
686                         goto close_fail;
687                 /*
688                  * Don't dump core if the filesystem changed owner or mode
689                  * of the file during file creation. This is an issue when
690                  * a process dumps core while its cwd is e.g. on a vfat
691                  * filesystem.
692                  */
693                 if (!uid_eq(inode->i_uid, current_fsuid()))
694                         goto close_fail;
695                 if ((inode->i_mode & 0677) != 0600)
696                         goto close_fail;
697                 if (!(cprm.file->f_mode & FMODE_CAN_WRITE))
698                         goto close_fail;
699                 if (do_truncate(cprm.file->f_path.dentry, 0, 0, cprm.file))
700                         goto close_fail;
701         }
702
703         /* get us an unshared descriptor table; almost always a no-op */
704         retval = unshare_files(&displaced);
705         if (retval)
706                 goto close_fail;
707         if (displaced)
708                 put_files_struct(displaced);
709         if (!dump_interrupted()) {
710                 file_start_write(cprm.file);
711                 core_dumped = binfmt->core_dump(&cprm);
712                 file_end_write(cprm.file);
713         }
714         if (ispipe && core_pipe_limit)
715                 wait_for_dump_helpers(cprm.file);
716 close_fail:
717         if (cprm.file)
718                 filp_close(cprm.file, NULL);
719 fail_dropcount:
720         if (ispipe)
721                 atomic_dec(&core_dump_count);
722 fail_unlock:
723         kfree(cn.corename);
724         coredump_finish(mm, core_dumped);
725         revert_creds(old_cred);
726 fail_creds:
727         put_cred(cred);
728 fail:
729         return;
730 }
731
732 /*
733  * Core dumping helper functions.  These are the only things you should
734  * do on a core-file: use only these functions to write out all the
735  * necessary info.
736  */
737 int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
738 {
739         struct file *file = cprm->file;
740         loff_t pos = file->f_pos;
741         ssize_t n;
742         if (cprm->written + nr > cprm->limit)
743                 return 0;
744         while (nr) {
745                 if (dump_interrupted())
746                         return 0;
747                 n = __kernel_write(file, addr, nr, &pos);
748                 if (n <= 0)
749                         return 0;
750                 file->f_pos = pos;
751                 cprm->written += n;
752                 nr -= n;
753         }
754         return 1;
755 }
756 EXPORT_SYMBOL(dump_emit);
757
758 int dump_skip(struct coredump_params *cprm, size_t nr)
759 {
760         static char zeroes[PAGE_SIZE];
761         struct file *file = cprm->file;
762         if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
763                 if (cprm->written + nr > cprm->limit)
764                         return 0;
765                 if (dump_interrupted() ||
766                     file->f_op->llseek(file, nr, SEEK_CUR) < 0)
767                         return 0;
768                 cprm->written += nr;
769                 return 1;
770         } else {
771                 while (nr > PAGE_SIZE) {
772                         if (!dump_emit(cprm, zeroes, PAGE_SIZE))
773                                 return 0;
774                         nr -= PAGE_SIZE;
775                 }
776                 return dump_emit(cprm, zeroes, nr);
777         }
778 }
779 EXPORT_SYMBOL(dump_skip);
780
781 int dump_align(struct coredump_params *cprm, int align)
782 {
783         unsigned mod = cprm->written & (align - 1);
784         if (align & (align - 1))
785                 return 0;
786         return mod ? dump_skip(cprm, align - mod) : 1;
787 }
788 EXPORT_SYMBOL(dump_align);