Merge remote-tracking branch 'y2038/y2038'
[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 #include <linux/timekeeping.h>
36
37 #include <asm/uaccess.h>
38 #include <asm/mmu_context.h>
39 #include <asm/tlb.h>
40 #include <asm/exec.h>
41
42 #include <trace/events/task.h>
43 #include "internal.h"
44
45 #include <trace/events/sched.h>
46
47 int core_uses_pid;
48 unsigned int core_pipe_limit;
49 char core_pattern[CORENAME_MAX_SIZE] = "core";
50 static int core_name_size = CORENAME_MAX_SIZE;
51
52 struct core_name {
53         char *corename;
54         int used, size;
55 };
56
57 /* The maximal length of core_pattern is also specified in sysctl.c */
58
59 static int expand_corename(struct core_name *cn, int size)
60 {
61         char *corename = krealloc(cn->corename, size, GFP_KERNEL);
62
63         if (!corename)
64                 return -ENOMEM;
65
66         if (size > core_name_size) /* racy but harmless */
67                 core_name_size = size;
68
69         cn->size = ksize(corename);
70         cn->corename = corename;
71         return 0;
72 }
73
74 static __printf(2, 0) int cn_vprintf(struct core_name *cn, const char *fmt,
75                                      va_list arg)
76 {
77         int free, need;
78         va_list arg_copy;
79
80 again:
81         free = cn->size - cn->used;
82
83         va_copy(arg_copy, arg);
84         need = vsnprintf(cn->corename + cn->used, free, fmt, arg_copy);
85         va_end(arg_copy);
86
87         if (need < free) {
88                 cn->used += need;
89                 return 0;
90         }
91
92         if (!expand_corename(cn, cn->size + need - free + 1))
93                 goto again;
94
95         return -ENOMEM;
96 }
97
98 static __printf(2, 3) int cn_printf(struct core_name *cn, const char *fmt, ...)
99 {
100         va_list arg;
101         int ret;
102
103         va_start(arg, fmt);
104         ret = cn_vprintf(cn, fmt, arg);
105         va_end(arg);
106
107         return ret;
108 }
109
110 static __printf(2, 3)
111 int cn_esc_printf(struct core_name *cn, const char *fmt, ...)
112 {
113         int cur = cn->used;
114         va_list arg;
115         int ret;
116
117         va_start(arg, fmt);
118         ret = cn_vprintf(cn, fmt, arg);
119         va_end(arg);
120
121         for (; cur < cn->used; ++cur) {
122                 if (cn->corename[cur] == '/')
123                         cn->corename[cur] = '!';
124         }
125         return ret;
126 }
127
128 static int cn_print_exe_file(struct core_name *cn)
129 {
130         struct file *exe_file;
131         char *pathbuf, *path;
132         int ret;
133
134         exe_file = get_mm_exe_file(current->mm);
135         if (!exe_file)
136                 return cn_esc_printf(cn, "%s (path unknown)", current->comm);
137
138         pathbuf = kmalloc(PATH_MAX, GFP_TEMPORARY);
139         if (!pathbuf) {
140                 ret = -ENOMEM;
141                 goto put_exe_file;
142         }
143
144         path = file_path(exe_file, pathbuf, PATH_MAX);
145         if (IS_ERR(path)) {
146                 ret = PTR_ERR(path);
147                 goto free_buf;
148         }
149
150         ret = cn_esc_printf(cn, "%s", path);
151
152 free_buf:
153         kfree(pathbuf);
154 put_exe_file:
155         fput(exe_file);
156         return ret;
157 }
158
159 /* format_corename will inspect the pattern parameter, and output a
160  * name into corename, which must have space for at least
161  * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
162  */
163 static int format_corename(struct core_name *cn, struct coredump_params *cprm)
164 {
165         const struct cred *cred = current_cred();
166         const char *pat_ptr = core_pattern;
167         int ispipe = (*pat_ptr == '|');
168         int pid_in_pattern = 0;
169         int err = 0;
170
171         cn->used = 0;
172         cn->corename = NULL;
173         if (expand_corename(cn, core_name_size))
174                 return -ENOMEM;
175         cn->corename[0] = '\0';
176
177         if (ispipe)
178                 ++pat_ptr;
179
180         /* Repeat as long as we have more pattern to process and more output
181            space */
182         while (*pat_ptr) {
183                 if (*pat_ptr != '%') {
184                         err = cn_printf(cn, "%c", *pat_ptr++);
185                 } else {
186                         switch (*++pat_ptr) {
187                         /* single % at the end, drop that */
188                         case 0:
189                                 goto out;
190                         /* Double percent, output one percent */
191                         case '%':
192                                 err = cn_printf(cn, "%c", '%');
193                                 break;
194                         /* pid */
195                         case 'p':
196                                 pid_in_pattern = 1;
197                                 err = cn_printf(cn, "%d",
198                                               task_tgid_vnr(current));
199                                 break;
200                         /* global pid */
201                         case 'P':
202                                 err = cn_printf(cn, "%d",
203                                               task_tgid_nr(current));
204                                 break;
205                         case 'i':
206                                 err = cn_printf(cn, "%d",
207                                               task_pid_vnr(current));
208                                 break;
209                         case 'I':
210                                 err = cn_printf(cn, "%d",
211                                               task_pid_nr(current));
212                                 break;
213                         /* uid */
214                         case 'u':
215                                 err = cn_printf(cn, "%u",
216                                                 from_kuid(&init_user_ns,
217                                                           cred->uid));
218                                 break;
219                         /* gid */
220                         case 'g':
221                                 err = cn_printf(cn, "%u",
222                                                 from_kgid(&init_user_ns,
223                                                           cred->gid));
224                                 break;
225                         case 'd':
226                                 err = cn_printf(cn, "%d",
227                                         __get_dumpable(cprm->mm_flags));
228                                 break;
229                         /* signal that caused the coredump */
230                         case 's':
231                                 err = cn_printf(cn, "%d",
232                                                 cprm->siginfo->si_signo);
233                                 break;
234                         /* UNIX time of coredump */
235                         case 't': {
236                                 time64_t time;
237
238                                 time = ktime_get_real_seconds();
239                                 err = cn_printf(cn, "%lld", time);
240                                 break;
241                         }
242                         /* hostname */
243                         case 'h':
244                                 down_read(&uts_sem);
245                                 err = cn_esc_printf(cn, "%s",
246                                               utsname()->nodename);
247                                 up_read(&uts_sem);
248                                 break;
249                         /* executable */
250                         case 'e':
251                                 err = cn_esc_printf(cn, "%s", current->comm);
252                                 break;
253                         case 'E':
254                                 err = cn_print_exe_file(cn);
255                                 break;
256                         /* core limit size */
257                         case 'c':
258                                 err = cn_printf(cn, "%lu",
259                                               rlimit(RLIMIT_CORE));
260                                 break;
261                         default:
262                                 break;
263                         }
264                         ++pat_ptr;
265                 }
266
267                 if (err)
268                         return err;
269         }
270
271 out:
272         /* Backward compatibility with core_uses_pid:
273          *
274          * If core_pattern does not include a %p (as is the default)
275          * and core_uses_pid is set, then .%pid will be appended to
276          * the filename. Do not do this for piped commands. */
277         if (!ispipe && !pid_in_pattern && core_uses_pid) {
278                 err = cn_printf(cn, ".%d", task_tgid_vnr(current));
279                 if (err)
280                         return err;
281         }
282         return ispipe;
283 }
284
285 static int zap_process(struct task_struct *start, int exit_code)
286 {
287         struct task_struct *t;
288         int nr = 0;
289
290         start->signal->group_exit_code = exit_code;
291         start->signal->group_stop_count = 0;
292
293         t = start;
294         do {
295                 task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
296                 if (t != current && t->mm) {
297                         sigaddset(&t->pending.signal, SIGKILL);
298                         signal_wake_up(t, 1);
299                         nr++;
300                 }
301         } while_each_thread(start, t);
302
303         return nr;
304 }
305
306 static int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
307                         struct core_state *core_state, int exit_code)
308 {
309         struct task_struct *g, *p;
310         unsigned long flags;
311         int nr = -EAGAIN;
312
313         spin_lock_irq(&tsk->sighand->siglock);
314         if (!signal_group_exit(tsk->signal)) {
315                 mm->core_state = core_state;
316                 nr = zap_process(tsk, exit_code);
317                 tsk->signal->group_exit_task = tsk;
318                 /* ignore all signals except SIGKILL, see prepare_signal() */
319                 tsk->signal->flags = SIGNAL_GROUP_COREDUMP;
320                 clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
321         }
322         spin_unlock_irq(&tsk->sighand->siglock);
323         if (unlikely(nr < 0))
324                 return nr;
325
326         tsk->flags |= PF_DUMPCORE;
327         if (atomic_read(&mm->mm_users) == nr + 1)
328                 goto done;
329         /*
330          * We should find and kill all tasks which use this mm, and we should
331          * count them correctly into ->nr_threads. We don't take tasklist
332          * lock, but this is safe wrt:
333          *
334          * fork:
335          *      None of sub-threads can fork after zap_process(leader). All
336          *      processes which were created before this point should be
337          *      visible to zap_threads() because copy_process() adds the new
338          *      process to the tail of init_task.tasks list, and lock/unlock
339          *      of ->siglock provides a memory barrier.
340          *
341          * do_exit:
342          *      The caller holds mm->mmap_sem. This means that the task which
343          *      uses this mm can't pass exit_mm(), so it can't exit or clear
344          *      its ->mm.
345          *
346          * de_thread:
347          *      It does list_replace_rcu(&leader->tasks, &current->tasks),
348          *      we must see either old or new leader, this does not matter.
349          *      However, it can change p->sighand, so lock_task_sighand(p)
350          *      must be used. Since p->mm != NULL and we hold ->mmap_sem
351          *      it can't fail.
352          *
353          *      Note also that "g" can be the old leader with ->mm == NULL
354          *      and already unhashed and thus removed from ->thread_group.
355          *      This is OK, __unhash_process()->list_del_rcu() does not
356          *      clear the ->next pointer, we will find the new leader via
357          *      next_thread().
358          */
359         rcu_read_lock();
360         for_each_process(g) {
361                 if (g == tsk->group_leader)
362                         continue;
363                 if (g->flags & PF_KTHREAD)
364                         continue;
365                 p = g;
366                 do {
367                         if (p->mm) {
368                                 if (unlikely(p->mm == mm)) {
369                                         lock_task_sighand(p, &flags);
370                                         nr += zap_process(p, exit_code);
371                                         p->signal->flags = SIGNAL_GROUP_EXIT;
372                                         unlock_task_sighand(p, &flags);
373                                 }
374                                 break;
375                         }
376                 } while_each_thread(g, p);
377         }
378         rcu_read_unlock();
379 done:
380         atomic_set(&core_state->nr_threads, nr);
381         return nr;
382 }
383
384 static int coredump_wait(int exit_code, struct core_state *core_state)
385 {
386         struct task_struct *tsk = current;
387         struct mm_struct *mm = tsk->mm;
388         int core_waiters = -EBUSY;
389
390         init_completion(&core_state->startup);
391         core_state->dumper.task = tsk;
392         core_state->dumper.next = NULL;
393
394         down_write(&mm->mmap_sem);
395         if (!mm->core_state)
396                 core_waiters = zap_threads(tsk, mm, core_state, exit_code);
397         up_write(&mm->mmap_sem);
398
399         if (core_waiters > 0) {
400                 struct core_thread *ptr;
401
402                 wait_for_completion(&core_state->startup);
403                 /*
404                  * Wait for all the threads to become inactive, so that
405                  * all the thread context (extended register state, like
406                  * fpu etc) gets copied to the memory.
407                  */
408                 ptr = core_state->dumper.next;
409                 while (ptr != NULL) {
410                         wait_task_inactive(ptr->task, 0);
411                         ptr = ptr->next;
412                 }
413         }
414
415         return core_waiters;
416 }
417
418 static void coredump_finish(struct mm_struct *mm, bool core_dumped)
419 {
420         struct core_thread *curr, *next;
421         struct task_struct *task;
422
423         spin_lock_irq(&current->sighand->siglock);
424         if (core_dumped && !__fatal_signal_pending(current))
425                 current->signal->group_exit_code |= 0x80;
426         current->signal->group_exit_task = NULL;
427         current->signal->flags = SIGNAL_GROUP_EXIT;
428         spin_unlock_irq(&current->sighand->siglock);
429
430         next = mm->core_state->dumper.next;
431         while ((curr = next) != NULL) {
432                 next = curr->next;
433                 task = curr->task;
434                 /*
435                  * see exit_mm(), curr->task must not see
436                  * ->task == NULL before we read ->next.
437                  */
438                 smp_mb();
439                 curr->task = NULL;
440                 wake_up_process(task);
441         }
442
443         mm->core_state = NULL;
444 }
445
446 static bool dump_interrupted(void)
447 {
448         /*
449          * SIGKILL or freezing() interrupt the coredumping. Perhaps we
450          * can do try_to_freeze() and check __fatal_signal_pending(),
451          * but then we need to teach dump_write() to restart and clear
452          * TIF_SIGPENDING.
453          */
454         return signal_pending(current);
455 }
456
457 static void wait_for_dump_helpers(struct file *file)
458 {
459         struct pipe_inode_info *pipe = file->private_data;
460
461         pipe_lock(pipe);
462         pipe->readers++;
463         pipe->writers--;
464         wake_up_interruptible_sync(&pipe->wait);
465         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
466         pipe_unlock(pipe);
467
468         /*
469          * We actually want wait_event_freezable() but then we need
470          * to clear TIF_SIGPENDING and improve dump_interrupted().
471          */
472         wait_event_interruptible(pipe->wait, pipe->readers == 1);
473
474         pipe_lock(pipe);
475         pipe->readers--;
476         pipe->writers++;
477         pipe_unlock(pipe);
478 }
479
480 /*
481  * umh_pipe_setup
482  * helper function to customize the process used
483  * to collect the core in userspace.  Specifically
484  * it sets up a pipe and installs it as fd 0 (stdin)
485  * for the process.  Returns 0 on success, or
486  * PTR_ERR on failure.
487  * Note that it also sets the core limit to 1.  This
488  * is a special value that we use to trap recursive
489  * core dumps
490  */
491 static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
492 {
493         struct file *files[2];
494         struct coredump_params *cp = (struct coredump_params *)info->data;
495         int err = create_pipe_files(files, 0);
496         if (err)
497                 return err;
498
499         cp->file = files[1];
500
501         err = replace_fd(0, files[0], 0);
502         fput(files[0]);
503         /* and disallow core files too */
504         current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
505
506         return err;
507 }
508
509 void do_coredump(const siginfo_t *siginfo)
510 {
511         struct core_state core_state;
512         struct core_name cn;
513         struct mm_struct *mm = current->mm;
514         struct linux_binfmt * binfmt;
515         const struct cred *old_cred;
516         struct cred *cred;
517         int retval = 0;
518         int ispipe;
519         struct files_struct *displaced;
520         /* require nonrelative corefile path and be extra careful */
521         bool need_suid_safe = false;
522         bool core_dumped = false;
523         static atomic_t core_dump_count = ATOMIC_INIT(0);
524         struct coredump_params cprm = {
525                 .siginfo = siginfo,
526                 .regs = signal_pt_regs(),
527                 .limit = rlimit(RLIMIT_CORE),
528                 /*
529                  * We must use the same mm->flags while dumping core to avoid
530                  * inconsistency of bit flags, since this flag is not protected
531                  * by any locks.
532                  */
533                 .mm_flags = mm->flags,
534         };
535
536         audit_core_dumps(siginfo->si_signo);
537
538         binfmt = mm->binfmt;
539         if (!binfmt || !binfmt->core_dump)
540                 goto fail;
541         if (!__get_dumpable(cprm.mm_flags))
542                 goto fail;
543
544         cred = prepare_creds();
545         if (!cred)
546                 goto fail;
547         /*
548          * We cannot trust fsuid as being the "true" uid of the process
549          * nor do we know its entire history. We only know it was tainted
550          * so we dump it as root in mode 2, and only into a controlled
551          * environment (pipe handler or fully qualified path).
552          */
553         if (__get_dumpable(cprm.mm_flags) == SUID_DUMP_ROOT) {
554                 /* Setuid core dump mode */
555                 cred->fsuid = GLOBAL_ROOT_UID;  /* Dump root private */
556                 need_suid_safe = true;
557         }
558
559         retval = coredump_wait(siginfo->si_signo, &core_state);
560         if (retval < 0)
561                 goto fail_creds;
562
563         old_cred = override_creds(cred);
564
565         ispipe = format_corename(&cn, &cprm);
566
567         if (ispipe) {
568                 int dump_count;
569                 char **helper_argv;
570                 struct subprocess_info *sub_info;
571
572                 if (ispipe < 0) {
573                         printk(KERN_WARNING "format_corename failed\n");
574                         printk(KERN_WARNING "Aborting core\n");
575                         goto fail_unlock;
576                 }
577
578                 if (cprm.limit == 1) {
579                         /* See umh_pipe_setup() which sets RLIMIT_CORE = 1.
580                          *
581                          * Normally core limits are irrelevant to pipes, since
582                          * we're not writing to the file system, but we use
583                          * cprm.limit of 1 here as a special value, this is a
584                          * consistent way to catch recursive crashes.
585                          * We can still crash if the core_pattern binary sets
586                          * RLIM_CORE = !1, but it runs as root, and can do
587                          * lots of stupid things.
588                          *
589                          * Note that we use task_tgid_vnr here to grab the pid
590                          * of the process group leader.  That way we get the
591                          * right pid if a thread in a multi-threaded
592                          * core_pattern process dies.
593                          */
594                         printk(KERN_WARNING
595                                 "Process %d(%s) has RLIMIT_CORE set to 1\n",
596                                 task_tgid_vnr(current), current->comm);
597                         printk(KERN_WARNING "Aborting core\n");
598                         goto fail_unlock;
599                 }
600                 cprm.limit = RLIM_INFINITY;
601
602                 dump_count = atomic_inc_return(&core_dump_count);
603                 if (core_pipe_limit && (core_pipe_limit < dump_count)) {
604                         printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n",
605                                task_tgid_vnr(current), current->comm);
606                         printk(KERN_WARNING "Skipping core dump\n");
607                         goto fail_dropcount;
608                 }
609
610                 helper_argv = argv_split(GFP_KERNEL, cn.corename, NULL);
611                 if (!helper_argv) {
612                         printk(KERN_WARNING "%s failed to allocate memory\n",
613                                __func__);
614                         goto fail_dropcount;
615                 }
616
617                 retval = -ENOMEM;
618                 sub_info = call_usermodehelper_setup(helper_argv[0],
619                                                 helper_argv, NULL, GFP_KERNEL,
620                                                 umh_pipe_setup, NULL, &cprm);
621                 if (sub_info)
622                         retval = call_usermodehelper_exec(sub_info,
623                                                           UMH_WAIT_EXEC);
624
625                 argv_free(helper_argv);
626                 if (retval) {
627                         printk(KERN_INFO "Core dump to |%s pipe failed\n",
628                                cn.corename);
629                         goto close_fail;
630                 }
631         } else {
632                 struct inode *inode;
633
634                 if (cprm.limit < binfmt->min_coredump)
635                         goto fail_unlock;
636
637                 if (need_suid_safe && cn.corename[0] != '/') {
638                         printk(KERN_WARNING "Pid %d(%s) can only dump core "\
639                                 "to fully qualified path!\n",
640                                 task_tgid_vnr(current), current->comm);
641                         printk(KERN_WARNING "Skipping core dump\n");
642                         goto fail_unlock;
643                 }
644
645                 /*
646                  * Unlink the file if it exists unless this is a SUID
647                  * binary - in that case, we're running around with root
648                  * privs and don't want to unlink another user's coredump.
649                  */
650                 if (!need_suid_safe) {
651                         mm_segment_t old_fs;
652
653                         old_fs = get_fs();
654                         set_fs(KERNEL_DS);
655                         /*
656                          * If it doesn't exist, that's fine. If there's some
657                          * other problem, we'll catch it at the filp_open().
658                          */
659                         (void) sys_unlink((const char __user *)cn.corename);
660                         set_fs(old_fs);
661                 }
662
663                 /*
664                  * There is a race between unlinking and creating the
665                  * file, but if that causes an EEXIST here, that's
666                  * fine - another process raced with us while creating
667                  * the corefile, and the other process won. To userspace,
668                  * what matters is that at least one of the two processes
669                  * writes its coredump successfully, not which one.
670                  */
671                 cprm.file = filp_open(cn.corename,
672                                  O_CREAT | 2 | O_NOFOLLOW |
673                                  O_LARGEFILE | O_EXCL,
674                                  0600);
675                 if (IS_ERR(cprm.file))
676                         goto fail_unlock;
677
678                 inode = file_inode(cprm.file);
679                 if (inode->i_nlink > 1)
680                         goto close_fail;
681                 if (d_unhashed(cprm.file->f_path.dentry))
682                         goto close_fail;
683                 /*
684                  * AK: actually i see no reason to not allow this for named
685                  * pipes etc, but keep the previous behaviour for now.
686                  */
687                 if (!S_ISREG(inode->i_mode))
688                         goto close_fail;
689                 /*
690                  * Don't dump core if the filesystem changed owner or mode
691                  * of the file during file creation. This is an issue when
692                  * a process dumps core while its cwd is e.g. on a vfat
693                  * filesystem.
694                  */
695                 if (!uid_eq(inode->i_uid, current_fsuid()))
696                         goto close_fail;
697                 if ((inode->i_mode & 0677) != 0600)
698                         goto close_fail;
699                 if (!(cprm.file->f_mode & FMODE_CAN_WRITE))
700                         goto close_fail;
701                 if (do_truncate(cprm.file->f_path.dentry, 0, 0, cprm.file))
702                         goto close_fail;
703         }
704
705         /* get us an unshared descriptor table; almost always a no-op */
706         retval = unshare_files(&displaced);
707         if (retval)
708                 goto close_fail;
709         if (displaced)
710                 put_files_struct(displaced);
711         if (!dump_interrupted()) {
712                 file_start_write(cprm.file);
713                 core_dumped = binfmt->core_dump(&cprm);
714                 file_end_write(cprm.file);
715         }
716         if (ispipe && core_pipe_limit)
717                 wait_for_dump_helpers(cprm.file);
718 close_fail:
719         if (cprm.file)
720                 filp_close(cprm.file, NULL);
721 fail_dropcount:
722         if (ispipe)
723                 atomic_dec(&core_dump_count);
724 fail_unlock:
725         kfree(cn.corename);
726         coredump_finish(mm, core_dumped);
727         revert_creds(old_cred);
728 fail_creds:
729         put_cred(cred);
730 fail:
731         return;
732 }
733
734 /*
735  * Core dumping helper functions.  These are the only things you should
736  * do on a core-file: use only these functions to write out all the
737  * necessary info.
738  */
739 int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
740 {
741         struct file *file = cprm->file;
742         loff_t pos = file->f_pos;
743         ssize_t n;
744         if (cprm->written + nr > cprm->limit)
745                 return 0;
746         while (nr) {
747                 if (dump_interrupted())
748                         return 0;
749                 n = __kernel_write(file, addr, nr, &pos);
750                 if (n <= 0)
751                         return 0;
752                 file->f_pos = pos;
753                 cprm->written += n;
754                 nr -= n;
755         }
756         return 1;
757 }
758 EXPORT_SYMBOL(dump_emit);
759
760 int dump_skip(struct coredump_params *cprm, size_t nr)
761 {
762         static char zeroes[PAGE_SIZE];
763         struct file *file = cprm->file;
764         if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
765                 if (cprm->written + nr > cprm->limit)
766                         return 0;
767                 if (dump_interrupted() ||
768                     file->f_op->llseek(file, nr, SEEK_CUR) < 0)
769                         return 0;
770                 cprm->written += nr;
771                 return 1;
772         } else {
773                 while (nr > PAGE_SIZE) {
774                         if (!dump_emit(cprm, zeroes, PAGE_SIZE))
775                                 return 0;
776                         nr -= PAGE_SIZE;
777                 }
778                 return dump_emit(cprm, zeroes, nr);
779         }
780 }
781 EXPORT_SYMBOL(dump_skip);
782
783 int dump_align(struct coredump_params *cprm, int align)
784 {
785         unsigned mod = cprm->written & (align - 1);
786         if (align & (align - 1))
787                 return 0;
788         return mod ? dump_skip(cprm, align - mod) : 1;
789 }
790 EXPORT_SYMBOL(dump_align);