linux-hardened/kernel/exit.c
Roland McGrath 54a0151041 asmlinkage_protect replaces prevent_tail_call
The prevent_tail_call() macro works around the problem of the compiler
clobbering argument words on the stack, which for asmlinkage functions
is the caller's (user's) struct pt_regs.  The tail/sibling-call
optimization is not the only way that the compiler can decide to use
stack argument words as scratch space, which we have to prevent.
Other optimizations can do it too.

Until we have new compiler support to make "asmlinkage" binding on the
compiler's own use of the stack argument frame, we have work around all
the manifestations of this issue that crop up.

More cases seem to be prevented by also keeping the incoming argument
variables live at the end of the function.  This makes their original
stack slots attractive places to leave those variables, so the compiler
tends not clobber them for something else.  It's still no guarantee, but
it handles some observed cases that prevent_tail_call() did not.

Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-10 17:28:26 -07:00

1658 lines
42 KiB
C

/*
* linux/kernel/exit.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*/
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/capability.h>
#include <linux/completion.h>
#include <linux/personality.h>
#include <linux/tty.h>
#include <linux/mnt_namespace.h>
#include <linux/key.h>
#include <linux/security.h>
#include <linux/cpu.h>
#include <linux/acct.h>
#include <linux/tsacct_kern.h>
#include <linux/file.h>
#include <linux/binfmts.h>
#include <linux/nsproxy.h>
#include <linux/pid_namespace.h>
#include <linux/ptrace.h>
#include <linux/profile.h>
#include <linux/mount.h>
#include <linux/proc_fs.h>
#include <linux/kthread.h>
#include <linux/mempolicy.h>
#include <linux/taskstats_kern.h>
#include <linux/delayacct.h>
#include <linux/freezer.h>
#include <linux/cgroup.h>
#include <linux/syscalls.h>
#include <linux/signal.h>
#include <linux/posix-timers.h>
#include <linux/cn_proc.h>
#include <linux/mutex.h>
#include <linux/futex.h>
#include <linux/compat.h>
#include <linux/pipe_fs_i.h>
#include <linux/audit.h> /* for audit_free() */
#include <linux/resource.h>
#include <linux/blkdev.h>
#include <linux/task_io_accounting_ops.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>
#include <asm/pgtable.h>
#include <asm/mmu_context.h>
static void exit_mm(struct task_struct * tsk);
static void __unhash_process(struct task_struct *p)
{
nr_threads--;
detach_pid(p, PIDTYPE_PID);
if (thread_group_leader(p)) {
detach_pid(p, PIDTYPE_PGID);
detach_pid(p, PIDTYPE_SID);
list_del_rcu(&p->tasks);
__get_cpu_var(process_counts)--;
}
list_del_rcu(&p->thread_group);
remove_parent(p);
}
/*
* This function expects the tasklist_lock write-locked.
*/
static void __exit_signal(struct task_struct *tsk)
{
struct signal_struct *sig = tsk->signal;
struct sighand_struct *sighand;
BUG_ON(!sig);
BUG_ON(!atomic_read(&sig->count));
rcu_read_lock();
sighand = rcu_dereference(tsk->sighand);
spin_lock(&sighand->siglock);
posix_cpu_timers_exit(tsk);
if (atomic_dec_and_test(&sig->count))
posix_cpu_timers_exit_group(tsk);
else {
/*
* If there is any task waiting for the group exit
* then notify it:
*/
if (sig->group_exit_task && atomic_read(&sig->count) == sig->notify_count)
wake_up_process(sig->group_exit_task);
if (tsk == sig->curr_target)
sig->curr_target = next_thread(tsk);
/*
* Accumulate here the counters for all threads but the
* group leader as they die, so they can be added into
* the process-wide totals when those are taken.
* The group leader stays around as a zombie as long
* as there are other threads. When it gets reaped,
* the exit.c code will add its counts into these totals.
* We won't ever get here for the group leader, since it
* will have been the last reference on the signal_struct.
*/
sig->utime = cputime_add(sig->utime, tsk->utime);
sig->stime = cputime_add(sig->stime, tsk->stime);
sig->gtime = cputime_add(sig->gtime, tsk->gtime);
sig->min_flt += tsk->min_flt;
sig->maj_flt += tsk->maj_flt;
sig->nvcsw += tsk->nvcsw;
sig->nivcsw += tsk->nivcsw;
sig->inblock += task_io_get_inblock(tsk);
sig->oublock += task_io_get_oublock(tsk);
sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
sig = NULL; /* Marker for below. */
}
__unhash_process(tsk);
tsk->signal = NULL;
tsk->sighand = NULL;
spin_unlock(&sighand->siglock);
rcu_read_unlock();
__cleanup_sighand(sighand);
clear_tsk_thread_flag(tsk,TIF_SIGPENDING);
flush_sigqueue(&tsk->pending);
if (sig) {
flush_sigqueue(&sig->shared_pending);
taskstats_tgid_free(sig);
__cleanup_signal(sig);
}
}
static void delayed_put_task_struct(struct rcu_head *rhp)
{
put_task_struct(container_of(rhp, struct task_struct, rcu));
}
void release_task(struct task_struct * p)
{
struct task_struct *leader;
int zap_leader;
repeat:
atomic_dec(&p->user->processes);
proc_flush_task(p);
write_lock_irq(&tasklist_lock);
ptrace_unlink(p);
BUG_ON(!list_empty(&p->ptrace_list) || !list_empty(&p->ptrace_children));
__exit_signal(p);
/*
* If we are the last non-leader member of the thread
* group, and the leader is zombie, then notify the
* group leader's parent process. (if it wants notification.)
*/
zap_leader = 0;
leader = p->group_leader;
if (leader != p && thread_group_empty(leader) && leader->exit_state == EXIT_ZOMBIE) {
BUG_ON(leader->exit_signal == -1);
do_notify_parent(leader, leader->exit_signal);
/*
* If we were the last child thread and the leader has
* exited already, and the leader's parent ignores SIGCHLD,
* then we are the one who should release the leader.
*
* do_notify_parent() will have marked it self-reaping in
* that case.
*/
zap_leader = (leader->exit_signal == -1);
}
write_unlock_irq(&tasklist_lock);
release_thread(p);
call_rcu(&p->rcu, delayed_put_task_struct);
p = leader;
if (unlikely(zap_leader))
goto repeat;
}
/*
* This checks not only the pgrp, but falls back on the pid if no
* satisfactory pgrp is found. I dunno - gdb doesn't work correctly
* without this...
*
* The caller must hold rcu lock or the tasklist lock.
*/
struct pid *session_of_pgrp(struct pid *pgrp)
{
struct task_struct *p;
struct pid *sid = NULL;
p = pid_task(pgrp, PIDTYPE_PGID);
if (p == NULL)
p = pid_task(pgrp, PIDTYPE_PID);
if (p != NULL)
sid = task_session(p);
return sid;
}
/*
* Determine if a process group is "orphaned", according to the POSIX
* definition in 2.2.2.52. Orphaned process groups are not to be affected
* by terminal-generated stop signals. Newly orphaned process groups are
* to receive a SIGHUP and a SIGCONT.
*
* "I ask you, have you ever known what it is to be an orphan?"
*/
static int will_become_orphaned_pgrp(struct pid *pgrp, struct task_struct *ignored_task)
{
struct task_struct *p;
do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
if ((p == ignored_task) ||
(p->exit_state && thread_group_empty(p)) ||
is_global_init(p->real_parent))
continue;
if (task_pgrp(p->real_parent) != pgrp &&
task_session(p->real_parent) == task_session(p))
return 0;
} while_each_pid_task(pgrp, PIDTYPE_PGID, p);
return 1;
}
int is_current_pgrp_orphaned(void)
{
int retval;
read_lock(&tasklist_lock);
retval = will_become_orphaned_pgrp(task_pgrp(current), NULL);
read_unlock(&tasklist_lock);
return retval;
}
static int has_stopped_jobs(struct pid *pgrp)
{
int retval = 0;
struct task_struct *p;
do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
if (!task_is_stopped(p))
continue;
retval = 1;
break;
} while_each_pid_task(pgrp, PIDTYPE_PGID, p);
return retval;
}
/*
* Check to see if any process groups have become orphaned as
* a result of our exiting, and if they have any stopped jobs,
* send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
*/
static void
kill_orphaned_pgrp(struct task_struct *tsk, struct task_struct *parent)
{
struct pid *pgrp = task_pgrp(tsk);
struct task_struct *ignored_task = tsk;
if (!parent)
/* exit: our father is in a different pgrp than
* we are and we were the only connection outside.
*/
parent = tsk->real_parent;
else
/* reparent: our child is in a different pgrp than
* we are, and it was the only connection outside.
*/
ignored_task = NULL;
if (task_pgrp(parent) != pgrp &&
task_session(parent) == task_session(tsk) &&
will_become_orphaned_pgrp(pgrp, ignored_task) &&
has_stopped_jobs(pgrp)) {
__kill_pgrp_info(SIGHUP, SEND_SIG_PRIV, pgrp);
__kill_pgrp_info(SIGCONT, SEND_SIG_PRIV, pgrp);
}
}
/**
* reparent_to_kthreadd - Reparent the calling kernel thread to kthreadd
*
* If a kernel thread is launched as a result of a system call, or if
* it ever exits, it should generally reparent itself to kthreadd so it
* isn't in the way of other processes and is correctly cleaned up on exit.
*
* The various task state such as scheduling policy and priority may have
* been inherited from a user process, so we reset them to sane values here.
*
* NOTE that reparent_to_kthreadd() gives the caller full capabilities.
*/
static void reparent_to_kthreadd(void)
{
write_lock_irq(&tasklist_lock);
ptrace_unlink(current);
/* Reparent to init */
remove_parent(current);
current->real_parent = current->parent = kthreadd_task;
add_parent(current);
/* Set the exit signal to SIGCHLD so we signal init on exit */
current->exit_signal = SIGCHLD;
if (task_nice(current) < 0)
set_user_nice(current, 0);
/* cpus_allowed? */
/* rt_priority? */
/* signals? */
security_task_reparent_to_init(current);
memcpy(current->signal->rlim, init_task.signal->rlim,
sizeof(current->signal->rlim));
atomic_inc(&(INIT_USER->__count));
write_unlock_irq(&tasklist_lock);
switch_uid(INIT_USER);
}
void __set_special_pids(struct pid *pid)
{
struct task_struct *curr = current->group_leader;
pid_t nr = pid_nr(pid);
if (task_session(curr) != pid) {
detach_pid(curr, PIDTYPE_SID);
attach_pid(curr, PIDTYPE_SID, pid);
set_task_session(curr, nr);
}
if (task_pgrp(curr) != pid) {
detach_pid(curr, PIDTYPE_PGID);
attach_pid(curr, PIDTYPE_PGID, pid);
set_task_pgrp(curr, nr);
}
}
static void set_special_pids(struct pid *pid)
{
write_lock_irq(&tasklist_lock);
__set_special_pids(pid);
write_unlock_irq(&tasklist_lock);
}
/*
* Let kernel threads use this to say that they
* allow a certain signal (since daemonize() will
* have disabled all of them by default).
*/
int allow_signal(int sig)
{
if (!valid_signal(sig) || sig < 1)
return -EINVAL;
spin_lock_irq(&current->sighand->siglock);
sigdelset(&current->blocked, sig);
if (!current->mm) {
/* Kernel threads handle their own signals.
Let the signal code know it'll be handled, so
that they don't get converted to SIGKILL or
just silently dropped */
current->sighand->action[(sig)-1].sa.sa_handler = (void __user *)2;
}
recalc_sigpending();
spin_unlock_irq(&current->sighand->siglock);
return 0;
}
EXPORT_SYMBOL(allow_signal);
int disallow_signal(int sig)
{
if (!valid_signal(sig) || sig < 1)
return -EINVAL;
spin_lock_irq(&current->sighand->siglock);
current->sighand->action[(sig)-1].sa.sa_handler = SIG_IGN;
recalc_sigpending();
spin_unlock_irq(&current->sighand->siglock);
return 0;
}
EXPORT_SYMBOL(disallow_signal);
/*
* Put all the gunge required to become a kernel thread without
* attached user resources in one place where it belongs.
*/
void daemonize(const char *name, ...)
{
va_list args;
struct fs_struct *fs;
sigset_t blocked;
va_start(args, name);
vsnprintf(current->comm, sizeof(current->comm), name, args);
va_end(args);
/*
* If we were started as result of loading a module, close all of the
* user space pages. We don't need them, and if we didn't close them
* they would be locked into memory.
*/
exit_mm(current);
/*
* We don't want to have TIF_FREEZE set if the system-wide hibernation
* or suspend transition begins right now.
*/
current->flags |= PF_NOFREEZE;
if (current->nsproxy != &init_nsproxy) {
get_nsproxy(&init_nsproxy);
switch_task_namespaces(current, &init_nsproxy);
}
set_special_pids(&init_struct_pid);
proc_clear_tty(current);
/* Block and flush all signals */
sigfillset(&blocked);
sigprocmask(SIG_BLOCK, &blocked, NULL);
flush_signals(current);
/* Become as one with the init task */
exit_fs(current); /* current->fs->count--; */
fs = init_task.fs;
current->fs = fs;
atomic_inc(&fs->count);
exit_files(current);
current->files = init_task.files;
atomic_inc(&current->files->count);
reparent_to_kthreadd();
}
EXPORT_SYMBOL(daemonize);
static void close_files(struct files_struct * files)
{
int i, j;
struct fdtable *fdt;
j = 0;
/*
* It is safe to dereference the fd table without RCU or
* ->file_lock because this is the last reference to the
* files structure.
*/
fdt = files_fdtable(files);
for (;;) {
unsigned long set;
i = j * __NFDBITS;
if (i >= fdt->max_fds)
break;
set = fdt->open_fds->fds_bits[j++];
while (set) {
if (set & 1) {
struct file * file = xchg(&fdt->fd[i], NULL);
if (file) {
filp_close(file, files);
cond_resched();
}
}
i++;
set >>= 1;
}
}
}
struct files_struct *get_files_struct(struct task_struct *task)
{
struct files_struct *files;
task_lock(task);
files = task->files;
if (files)
atomic_inc(&files->count);
task_unlock(task);
return files;
}
void put_files_struct(struct files_struct *files)
{
struct fdtable *fdt;
if (atomic_dec_and_test(&files->count)) {
close_files(files);
/*
* Free the fd and fdset arrays if we expanded them.
* If the fdtable was embedded, pass files for freeing
* at the end of the RCU grace period. Otherwise,
* you can free files immediately.
*/
fdt = files_fdtable(files);
if (fdt != &files->fdtab)
kmem_cache_free(files_cachep, files);
free_fdtable(fdt);
}
}
EXPORT_SYMBOL(put_files_struct);
void reset_files_struct(struct task_struct *tsk, struct files_struct *files)
{
struct files_struct *old;
old = tsk->files;
task_lock(tsk);
tsk->files = files;
task_unlock(tsk);
put_files_struct(old);
}
EXPORT_SYMBOL(reset_files_struct);
static void __exit_files(struct task_struct *tsk)
{
struct files_struct * files = tsk->files;
if (files) {
task_lock(tsk);
tsk->files = NULL;
task_unlock(tsk);
put_files_struct(files);
}
}
void exit_files(struct task_struct *tsk)
{
__exit_files(tsk);
}
static void __put_fs_struct(struct fs_struct *fs)
{
/* No need to hold fs->lock if we are killing it */
if (atomic_dec_and_test(&fs->count)) {
path_put(&fs->root);
path_put(&fs->pwd);
if (fs->altroot.dentry)
path_put(&fs->altroot);
kmem_cache_free(fs_cachep, fs);
}
}
void put_fs_struct(struct fs_struct *fs)
{
__put_fs_struct(fs);
}
static void __exit_fs(struct task_struct *tsk)
{
struct fs_struct * fs = tsk->fs;
if (fs) {
task_lock(tsk);
tsk->fs = NULL;
task_unlock(tsk);
__put_fs_struct(fs);
}
}
void exit_fs(struct task_struct *tsk)
{
__exit_fs(tsk);
}
EXPORT_SYMBOL_GPL(exit_fs);
/*
* Turn us into a lazy TLB process if we
* aren't already..
*/
static void exit_mm(struct task_struct * tsk)
{
struct mm_struct *mm = tsk->mm;
mm_release(tsk, mm);
if (!mm)
return;
/*
* Serialize with any possible pending coredump.
* We must hold mmap_sem around checking core_waiters
* and clearing tsk->mm. The core-inducing thread
* will increment core_waiters for each thread in the
* group with ->mm != NULL.
*/
down_read(&mm->mmap_sem);
if (mm->core_waiters) {
up_read(&mm->mmap_sem);
down_write(&mm->mmap_sem);
if (!--mm->core_waiters)
complete(mm->core_startup_done);
up_write(&mm->mmap_sem);
wait_for_completion(&mm->core_done);
down_read(&mm->mmap_sem);
}
atomic_inc(&mm->mm_count);
BUG_ON(mm != tsk->active_mm);
/* more a memory barrier than a real lock */
task_lock(tsk);
tsk->mm = NULL;
up_read(&mm->mmap_sem);
enter_lazy_tlb(mm, current);
/* We don't want this task to be frozen prematurely */
clear_freeze_flag(tsk);
task_unlock(tsk);
mmput(mm);
}
static void
reparent_thread(struct task_struct *p, struct task_struct *father, int traced)
{
if (p->pdeath_signal)
/* We already hold the tasklist_lock here. */
group_send_sig_info(p->pdeath_signal, SEND_SIG_NOINFO, p);
/* Move the child from its dying parent to the new one. */
if (unlikely(traced)) {
/* Preserve ptrace links if someone else is tracing this child. */
list_del_init(&p->ptrace_list);
if (p->parent != p->real_parent)
list_add(&p->ptrace_list, &p->real_parent->ptrace_children);
} else {
/* If this child is being traced, then we're the one tracing it
* anyway, so let go of it.
*/
p->ptrace = 0;
remove_parent(p);
p->parent = p->real_parent;
add_parent(p);
if (task_is_traced(p)) {
/*
* If it was at a trace stop, turn it into
* a normal stop since it's no longer being
* traced.
*/
ptrace_untrace(p);
}
}
/* If this is a threaded reparent there is no need to
* notify anyone anything has happened.
*/
if (p->real_parent->group_leader == father->group_leader)
return;
/* We don't want people slaying init. */
if (p->exit_signal != -1)
p->exit_signal = SIGCHLD;
/* If we'd notified the old parent about this child's death,
* also notify the new parent.
*/
if (!traced && p->exit_state == EXIT_ZOMBIE &&
p->exit_signal != -1 && thread_group_empty(p))
do_notify_parent(p, p->exit_signal);
kill_orphaned_pgrp(p, father);
}
/*
* When we die, we re-parent all our children.
* Try to give them to another thread in our thread
* group, and if no such member exists, give it to
* the child reaper process (ie "init") in our pid
* space.
*/
static void forget_original_parent(struct task_struct *father)
{
struct task_struct *p, *n, *reaper = father;
struct list_head ptrace_dead;
INIT_LIST_HEAD(&ptrace_dead);
write_lock_irq(&tasklist_lock);
do {
reaper = next_thread(reaper);
if (reaper == father) {
reaper = task_child_reaper(father);
break;
}
} while (reaper->flags & PF_EXITING);
/*
* There are only two places where our children can be:
*
* - in our child list
* - in our ptraced child list
*
* Search them and reparent children.
*/
list_for_each_entry_safe(p, n, &father->children, sibling) {
int ptrace;
ptrace = p->ptrace;
/* if father isn't the real parent, then ptrace must be enabled */
BUG_ON(father != p->real_parent && !ptrace);
if (father == p->real_parent) {
/* reparent with a reaper, real father it's us */
p->real_parent = reaper;
reparent_thread(p, father, 0);
} else {
/* reparent ptraced task to its real parent */
__ptrace_unlink (p);
if (p->exit_state == EXIT_ZOMBIE && p->exit_signal != -1 &&
thread_group_empty(p))
do_notify_parent(p, p->exit_signal);
}
/*
* if the ptraced child is a zombie with exit_signal == -1
* we must collect it before we exit, or it will remain
* zombie forever since we prevented it from self-reap itself
* while it was being traced by us, to be able to see it in wait4.
*/
if (unlikely(ptrace && p->exit_state == EXIT_ZOMBIE && p->exit_signal == -1))
list_add(&p->ptrace_list, &ptrace_dead);
}
list_for_each_entry_safe(p, n, &father->ptrace_children, ptrace_list) {
p->real_parent = reaper;
reparent_thread(p, father, 1);
}
write_unlock_irq(&tasklist_lock);
BUG_ON(!list_empty(&father->children));
BUG_ON(!list_empty(&father->ptrace_children));
list_for_each_entry_safe(p, n, &ptrace_dead, ptrace_list) {
list_del_init(&p->ptrace_list);
release_task(p);
}
}
/*
* Send signals to all our closest relatives so that they know
* to properly mourn us..
*/
static void exit_notify(struct task_struct *tsk, int group_dead)
{
int state;
/*
* This does two things:
*
* A. Make init inherit all the child processes
* B. Check to see if any process groups have become orphaned
* as a result of our exiting, and if they have any stopped
* jobs, send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
*/
forget_original_parent(tsk);
exit_task_namespaces(tsk);
write_lock_irq(&tasklist_lock);
if (group_dead)
kill_orphaned_pgrp(tsk->group_leader, NULL);
/* Let father know we died
*
* Thread signals are configurable, but you aren't going to use
* that to send signals to arbitary processes.
* That stops right now.
*
* If the parent exec id doesn't match the exec id we saved
* when we started then we know the parent has changed security
* domain.
*
* If our self_exec id doesn't match our parent_exec_id then
* we have changed execution domain as these two values started
* the same after a fork.
*/
if (tsk->exit_signal != SIGCHLD && tsk->exit_signal != -1 &&
(tsk->parent_exec_id != tsk->real_parent->self_exec_id ||
tsk->self_exec_id != tsk->parent_exec_id)
&& !capable(CAP_KILL))
tsk->exit_signal = SIGCHLD;
/* If something other than our normal parent is ptracing us, then
* send it a SIGCHLD instead of honoring exit_signal. exit_signal
* only has special meaning to our real parent.
*/
if (tsk->exit_signal != -1 && thread_group_empty(tsk)) {
int signal = tsk->parent == tsk->real_parent ? tsk->exit_signal : SIGCHLD;
do_notify_parent(tsk, signal);
} else if (tsk->ptrace) {
do_notify_parent(tsk, SIGCHLD);
}
state = EXIT_ZOMBIE;
if (tsk->exit_signal == -1 && likely(!tsk->ptrace))
state = EXIT_DEAD;
tsk->exit_state = state;
if (thread_group_leader(tsk) &&
tsk->signal->notify_count < 0 &&
tsk->signal->group_exit_task)
wake_up_process(tsk->signal->group_exit_task);
write_unlock_irq(&tasklist_lock);
/* If the process is dead, release it - nobody will wait for it */
if (state == EXIT_DEAD)
release_task(tsk);
}
#ifdef CONFIG_DEBUG_STACK_USAGE
static void check_stack_usage(void)
{
static DEFINE_SPINLOCK(low_water_lock);
static int lowest_to_date = THREAD_SIZE;
unsigned long *n = end_of_stack(current);
unsigned long free;
while (*n == 0)
n++;
free = (unsigned long)n - (unsigned long)end_of_stack(current);
if (free >= lowest_to_date)
return;
spin_lock(&low_water_lock);
if (free < lowest_to_date) {
printk(KERN_WARNING "%s used greatest stack depth: %lu bytes "
"left\n",
current->comm, free);
lowest_to_date = free;
}
spin_unlock(&low_water_lock);
}
#else
static inline void check_stack_usage(void) {}
#endif
static inline void exit_child_reaper(struct task_struct *tsk)
{
if (likely(tsk->group_leader != task_child_reaper(tsk)))
return;
if (tsk->nsproxy->pid_ns == &init_pid_ns)
panic("Attempted to kill init!");
/*
* @tsk is the last thread in the 'cgroup-init' and is exiting.
* Terminate all remaining processes in the namespace and reap them
* before exiting @tsk.
*
* Note that @tsk (last thread of cgroup-init) may not necessarily
* be the child-reaper (i.e main thread of cgroup-init) of the
* namespace i.e the child_reaper may have already exited.
*
* Even after a child_reaper exits, we let it inherit orphaned children,
* because, pid_ns->child_reaper remains valid as long as there is
* at least one living sub-thread in the cgroup init.
* This living sub-thread of the cgroup-init will be notified when
* a child inherited by the 'child-reaper' exits (do_notify_parent()
* uses __group_send_sig_info()). Further, when reaping child processes,
* do_wait() iterates over children of all living sub threads.
* i.e even though 'child_reaper' thread is listed as the parent of the
* orphaned children, any living sub-thread in the cgroup-init can
* perform the role of the child_reaper.
*/
zap_pid_ns_processes(tsk->nsproxy->pid_ns);
}
NORET_TYPE void do_exit(long code)
{
struct task_struct *tsk = current;
int group_dead;
profile_task_exit(tsk);
WARN_ON(atomic_read(&tsk->fs_excl));
if (unlikely(in_interrupt()))
panic("Aiee, killing interrupt handler!");
if (unlikely(!tsk->pid))
panic("Attempted to kill the idle task!");
if (unlikely(current->ptrace & PT_TRACE_EXIT)) {
current->ptrace_message = code;
ptrace_notify((PTRACE_EVENT_EXIT << 8) | SIGTRAP);
}
/*
* We're taking recursive faults here in do_exit. Safest is to just
* leave this task alone and wait for reboot.
*/
if (unlikely(tsk->flags & PF_EXITING)) {
printk(KERN_ALERT
"Fixing recursive fault but reboot is needed!\n");
/*
* We can do this unlocked here. The futex code uses
* this flag just to verify whether the pi state
* cleanup has been done or not. In the worst case it
* loops once more. We pretend that the cleanup was
* done as there is no way to return. Either the
* OWNER_DIED bit is set by now or we push the blocked
* task into the wait for ever nirwana as well.
*/
tsk->flags |= PF_EXITPIDONE;
if (tsk->io_context)
exit_io_context();
set_current_state(TASK_UNINTERRUPTIBLE);
schedule();
}
exit_signals(tsk); /* sets PF_EXITING */
/*
* tsk->flags are checked in the futex code to protect against
* an exiting task cleaning up the robust pi futexes.
*/
smp_mb();
spin_unlock_wait(&tsk->pi_lock);
if (unlikely(in_atomic()))
printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",
current->comm, task_pid_nr(current),
preempt_count());
acct_update_integrals(tsk);
if (tsk->mm) {
update_hiwater_rss(tsk->mm);
update_hiwater_vm(tsk->mm);
}
group_dead = atomic_dec_and_test(&tsk->signal->live);
if (group_dead) {
exit_child_reaper(tsk);
hrtimer_cancel(&tsk->signal->real_timer);
exit_itimers(tsk->signal);
}
acct_collect(code, group_dead);
#ifdef CONFIG_FUTEX
if (unlikely(tsk->robust_list))
exit_robust_list(tsk);
#ifdef CONFIG_COMPAT
if (unlikely(tsk->compat_robust_list))
compat_exit_robust_list(tsk);
#endif
#endif
if (group_dead)
tty_audit_exit();
if (unlikely(tsk->audit_context))
audit_free(tsk);
tsk->exit_code = code;
taskstats_exit(tsk, group_dead);
exit_mm(tsk);
if (group_dead)
acct_process();
exit_sem(tsk);
__exit_files(tsk);
__exit_fs(tsk);
check_stack_usage();
exit_thread();
cgroup_exit(tsk, 1);
exit_keys(tsk);
if (group_dead && tsk->signal->leader)
disassociate_ctty(1);
module_put(task_thread_info(tsk)->exec_domain->module);
if (tsk->binfmt)
module_put(tsk->binfmt->module);
proc_exit_connector(tsk);
exit_notify(tsk, group_dead);
#ifdef CONFIG_NUMA
mpol_free(tsk->mempolicy);
tsk->mempolicy = NULL;
#endif
#ifdef CONFIG_FUTEX
/*
* This must happen late, after the PID is not
* hashed anymore:
*/
if (unlikely(!list_empty(&tsk->pi_state_list)))
exit_pi_state_list(tsk);
if (unlikely(current->pi_state_cache))
kfree(current->pi_state_cache);
#endif
/*
* Make sure we are holding no locks:
*/
debug_check_no_locks_held(tsk);
/*
* We can do this unlocked here. The futex code uses this flag
* just to verify whether the pi state cleanup has been done
* or not. In the worst case it loops once more.
*/
tsk->flags |= PF_EXITPIDONE;
if (tsk->io_context)
exit_io_context();
if (tsk->splice_pipe)
__free_pipe_info(tsk->splice_pipe);
preempt_disable();
/* causes final put_task_struct in finish_task_switch(). */
tsk->state = TASK_DEAD;
schedule();
BUG();
/* Avoid "noreturn function does return". */
for (;;)
cpu_relax(); /* For when BUG is null */
}
EXPORT_SYMBOL_GPL(do_exit);
NORET_TYPE void complete_and_exit(struct completion *comp, long code)
{
if (comp)
complete(comp);
do_exit(code);
}
EXPORT_SYMBOL(complete_and_exit);
asmlinkage long sys_exit(int error_code)
{
do_exit((error_code&0xff)<<8);
}
/*
* Take down every thread in the group. This is called by fatal signals
* as well as by sys_exit_group (below).
*/
NORET_TYPE void
do_group_exit(int exit_code)
{
BUG_ON(exit_code & 0x80); /* core dumps don't get here */
if (current->signal->flags & SIGNAL_GROUP_EXIT)
exit_code = current->signal->group_exit_code;
else if (!thread_group_empty(current)) {
struct signal_struct *const sig = current->signal;
struct sighand_struct *const sighand = current->sighand;
spin_lock_irq(&sighand->siglock);
if (signal_group_exit(sig))
/* Another thread got here before we took the lock. */
exit_code = sig->group_exit_code;
else {
sig->group_exit_code = exit_code;
sig->flags = SIGNAL_GROUP_EXIT;
zap_other_threads(current);
}
spin_unlock_irq(&sighand->siglock);
}
do_exit(exit_code);
/* NOTREACHED */
}
/*
* this kills every thread in the thread group. Note that any externally
* wait4()-ing process will get the correct exit code - even if this
* thread is not the thread group leader.
*/
asmlinkage void sys_exit_group(int error_code)
{
do_group_exit((error_code & 0xff) << 8);
}
static struct pid *task_pid_type(struct task_struct *task, enum pid_type type)
{
struct pid *pid = NULL;
if (type == PIDTYPE_PID)
pid = task->pids[type].pid;
else if (type < PIDTYPE_MAX)
pid = task->group_leader->pids[type].pid;
return pid;
}
static int eligible_child(enum pid_type type, struct pid *pid, int options,
struct task_struct *p)
{
int err;
if (type < PIDTYPE_MAX) {
if (task_pid_type(p, type) != pid)
return 0;
}
/*
* Do not consider detached threads that are
* not ptraced:
*/
if (p->exit_signal == -1 && !p->ptrace)
return 0;
/* Wait for all children (clone and not) if __WALL is set;
* otherwise, wait for clone children *only* if __WCLONE is
* set; otherwise, wait for non-clone children *only*. (Note:
* A "clone" child here is one that reports to its parent
* using a signal other than SIGCHLD.) */
if (((p->exit_signal != SIGCHLD) ^ ((options & __WCLONE) != 0))
&& !(options & __WALL))
return 0;
err = security_task_wait(p);
if (likely(!err))
return 1;
if (type != PIDTYPE_PID)
return 0;
/* This child was explicitly requested, abort */
read_unlock(&tasklist_lock);
return err;
}
static int wait_noreap_copyout(struct task_struct *p, pid_t pid, uid_t uid,
int why, int status,
struct siginfo __user *infop,
struct rusage __user *rusagep)
{
int retval = rusagep ? getrusage(p, RUSAGE_BOTH, rusagep) : 0;
put_task_struct(p);
if (!retval)
retval = put_user(SIGCHLD, &infop->si_signo);
if (!retval)
retval = put_user(0, &infop->si_errno);
if (!retval)
retval = put_user((short)why, &infop->si_code);
if (!retval)
retval = put_user(pid, &infop->si_pid);
if (!retval)
retval = put_user(uid, &infop->si_uid);
if (!retval)
retval = put_user(status, &infop->si_status);
if (!retval)
retval = pid;
return retval;
}
/*
* Handle sys_wait4 work for one task in state EXIT_ZOMBIE. We hold
* read_lock(&tasklist_lock) on entry. If we return zero, we still hold
* the lock and this task is uninteresting. If we return nonzero, we have
* released the lock and the system call should return.
*/
static int wait_task_zombie(struct task_struct *p, int noreap,
struct siginfo __user *infop,
int __user *stat_addr, struct rusage __user *ru)
{
unsigned long state;
int retval, status, traced;
pid_t pid = task_pid_vnr(p);
if (unlikely(noreap)) {
uid_t uid = p->uid;
int exit_code = p->exit_code;
int why, status;
get_task_struct(p);
read_unlock(&tasklist_lock);
if ((exit_code & 0x7f) == 0) {
why = CLD_EXITED;
status = exit_code >> 8;
} else {
why = (exit_code & 0x80) ? CLD_DUMPED : CLD_KILLED;
status = exit_code & 0x7f;
}
return wait_noreap_copyout(p, pid, uid, why,
status, infop, ru);
}
/*
* Try to move the task's state to DEAD
* only one thread is allowed to do this:
*/
state = xchg(&p->exit_state, EXIT_DEAD);
if (state != EXIT_ZOMBIE) {
BUG_ON(state != EXIT_DEAD);
return 0;
}
/* traced means p->ptrace, but not vice versa */
traced = (p->real_parent != p->parent);
if (likely(!traced)) {
struct signal_struct *psig;
struct signal_struct *sig;
/*
* The resource counters for the group leader are in its
* own task_struct. Those for dead threads in the group
* are in its signal_struct, as are those for the child
* processes it has previously reaped. All these
* accumulate in the parent's signal_struct c* fields.
*
* We don't bother to take a lock here to protect these
* p->signal fields, because they are only touched by
* __exit_signal, which runs with tasklist_lock
* write-locked anyway, and so is excluded here. We do
* need to protect the access to p->parent->signal fields,
* as other threads in the parent group can be right
* here reaping other children at the same time.
*/
spin_lock_irq(&p->parent->sighand->siglock);
psig = p->parent->signal;
sig = p->signal;
psig->cutime =
cputime_add(psig->cutime,
cputime_add(p->utime,
cputime_add(sig->utime,
sig->cutime)));
psig->cstime =
cputime_add(psig->cstime,
cputime_add(p->stime,
cputime_add(sig->stime,
sig->cstime)));
psig->cgtime =
cputime_add(psig->cgtime,
cputime_add(p->gtime,
cputime_add(sig->gtime,
sig->cgtime)));
psig->cmin_flt +=
p->min_flt + sig->min_flt + sig->cmin_flt;
psig->cmaj_flt +=
p->maj_flt + sig->maj_flt + sig->cmaj_flt;
psig->cnvcsw +=
p->nvcsw + sig->nvcsw + sig->cnvcsw;
psig->cnivcsw +=
p->nivcsw + sig->nivcsw + sig->cnivcsw;
psig->cinblock +=
task_io_get_inblock(p) +
sig->inblock + sig->cinblock;
psig->coublock +=
task_io_get_oublock(p) +
sig->oublock + sig->coublock;
spin_unlock_irq(&p->parent->sighand->siglock);
}
/*
* Now we are sure this task is interesting, and no other
* thread can reap it because we set its state to EXIT_DEAD.
*/
read_unlock(&tasklist_lock);
retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
status = (p->signal->flags & SIGNAL_GROUP_EXIT)
? p->signal->group_exit_code : p->exit_code;
if (!retval && stat_addr)
retval = put_user(status, stat_addr);
if (!retval && infop)
retval = put_user(SIGCHLD, &infop->si_signo);
if (!retval && infop)
retval = put_user(0, &infop->si_errno);
if (!retval && infop) {
int why;
if ((status & 0x7f) == 0) {
why = CLD_EXITED;
status >>= 8;
} else {
why = (status & 0x80) ? CLD_DUMPED : CLD_KILLED;
status &= 0x7f;
}
retval = put_user((short)why, &infop->si_code);
if (!retval)
retval = put_user(status, &infop->si_status);
}
if (!retval && infop)
retval = put_user(pid, &infop->si_pid);
if (!retval && infop)
retval = put_user(p->uid, &infop->si_uid);
if (!retval)
retval = pid;
if (traced) {
write_lock_irq(&tasklist_lock);
/* We dropped tasklist, ptracer could die and untrace */
ptrace_unlink(p);
/*
* If this is not a detached task, notify the parent.
* If it's still not detached after that, don't release
* it now.
*/
if (p->exit_signal != -1) {
do_notify_parent(p, p->exit_signal);
if (p->exit_signal != -1) {
p->exit_state = EXIT_ZOMBIE;
p = NULL;
}
}
write_unlock_irq(&tasklist_lock);
}
if (p != NULL)
release_task(p);
return retval;
}
/*
* Handle sys_wait4 work for one task in state TASK_STOPPED. We hold
* read_lock(&tasklist_lock) on entry. If we return zero, we still hold
* the lock and this task is uninteresting. If we return nonzero, we have
* released the lock and the system call should return.
*/
static int wait_task_stopped(struct task_struct *p,
int noreap, struct siginfo __user *infop,
int __user *stat_addr, struct rusage __user *ru)
{
int retval, exit_code, why;
uid_t uid = 0; /* unneeded, required by compiler */
pid_t pid;
exit_code = 0;
spin_lock_irq(&p->sighand->siglock);
if (unlikely(!task_is_stopped_or_traced(p)))
goto unlock_sig;
if (!(p->ptrace & PT_PTRACED) && p->signal->group_stop_count > 0)
/*
* A group stop is in progress and this is the group leader.
* We won't report until all threads have stopped.
*/
goto unlock_sig;
exit_code = p->exit_code;
if (!exit_code)
goto unlock_sig;
if (!noreap)
p->exit_code = 0;
uid = p->uid;
unlock_sig:
spin_unlock_irq(&p->sighand->siglock);
if (!exit_code)
return 0;
/*
* Now we are pretty sure this task is interesting.
* Make sure it doesn't get reaped out from under us while we
* give up the lock and then examine it below. We don't want to
* keep holding onto the tasklist_lock while we call getrusage and
* possibly take page faults for user memory.
*/
get_task_struct(p);
pid = task_pid_vnr(p);
why = (p->ptrace & PT_PTRACED) ? CLD_TRAPPED : CLD_STOPPED;
read_unlock(&tasklist_lock);
if (unlikely(noreap))
return wait_noreap_copyout(p, pid, uid,
why, exit_code,
infop, ru);
retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
if (!retval && stat_addr)
retval = put_user((exit_code << 8) | 0x7f, stat_addr);
if (!retval && infop)
retval = put_user(SIGCHLD, &infop->si_signo);
if (!retval && infop)
retval = put_user(0, &infop->si_errno);
if (!retval && infop)
retval = put_user((short)why, &infop->si_code);
if (!retval && infop)
retval = put_user(exit_code, &infop->si_status);
if (!retval && infop)
retval = put_user(pid, &infop->si_pid);
if (!retval && infop)
retval = put_user(uid, &infop->si_uid);
if (!retval)
retval = pid;
put_task_struct(p);
BUG_ON(!retval);
return retval;
}
/*
* Handle do_wait work for one task in a live, non-stopped state.
* read_lock(&tasklist_lock) on entry. If we return zero, we still hold
* the lock and this task is uninteresting. If we return nonzero, we have
* released the lock and the system call should return.
*/
static int wait_task_continued(struct task_struct *p, int noreap,
struct siginfo __user *infop,
int __user *stat_addr, struct rusage __user *ru)
{
int retval;
pid_t pid;
uid_t uid;
if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))
return 0;
spin_lock_irq(&p->sighand->siglock);
/* Re-check with the lock held. */
if (!(p->signal->flags & SIGNAL_STOP_CONTINUED)) {
spin_unlock_irq(&p->sighand->siglock);
return 0;
}
if (!noreap)
p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
spin_unlock_irq(&p->sighand->siglock);
pid = task_pid_vnr(p);
uid = p->uid;
get_task_struct(p);
read_unlock(&tasklist_lock);
if (!infop) {
retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
put_task_struct(p);
if (!retval && stat_addr)
retval = put_user(0xffff, stat_addr);
if (!retval)
retval = pid;
} else {
retval = wait_noreap_copyout(p, pid, uid,
CLD_CONTINUED, SIGCONT,
infop, ru);
BUG_ON(retval == 0);
}
return retval;
}
static long do_wait(enum pid_type type, struct pid *pid, int options,
struct siginfo __user *infop, int __user *stat_addr,
struct rusage __user *ru)
{
DECLARE_WAITQUEUE(wait, current);
struct task_struct *tsk;
int flag, retval;
add_wait_queue(&current->signal->wait_chldexit,&wait);
repeat:
/* If there is nothing that can match our critier just get out */
retval = -ECHILD;
if ((type < PIDTYPE_MAX) && (!pid || hlist_empty(&pid->tasks[type])))
goto end;
/*
* We will set this flag if we see any child that might later
* match our criteria, even if we are not able to reap it yet.
*/
flag = retval = 0;
current->state = TASK_INTERRUPTIBLE;
read_lock(&tasklist_lock);
tsk = current;
do {
struct task_struct *p;
list_for_each_entry(p, &tsk->children, sibling) {
int ret = eligible_child(type, pid, options, p);
if (!ret)
continue;
if (unlikely(ret < 0)) {
retval = ret;
} else if (task_is_stopped_or_traced(p)) {
/*
* It's stopped now, so it might later
* continue, exit, or stop again.
*/
flag = 1;
if (!(p->ptrace & PT_PTRACED) &&
!(options & WUNTRACED))
continue;
retval = wait_task_stopped(p,
(options & WNOWAIT), infop,
stat_addr, ru);
} else if (p->exit_state == EXIT_ZOMBIE &&
!delay_group_leader(p)) {
/*
* We don't reap group leaders with subthreads.
*/
if (!likely(options & WEXITED))
continue;
retval = wait_task_zombie(p,
(options & WNOWAIT), infop,
stat_addr, ru);
} else if (p->exit_state != EXIT_DEAD) {
/*
* It's running now, so it might later
* exit, stop, or stop and then continue.
*/
flag = 1;
if (!unlikely(options & WCONTINUED))
continue;
retval = wait_task_continued(p,
(options & WNOWAIT), infop,
stat_addr, ru);
}
if (retval != 0) /* tasklist_lock released */
goto end;
}
if (!flag) {
list_for_each_entry(p, &tsk->ptrace_children,
ptrace_list) {
flag = eligible_child(type, pid, options, p);
if (!flag)
continue;
if (likely(flag > 0))
break;
retval = flag;
goto end;
}
}
if (options & __WNOTHREAD)
break;
tsk = next_thread(tsk);
BUG_ON(tsk->signal != current->signal);
} while (tsk != current);
read_unlock(&tasklist_lock);
if (flag) {
if (options & WNOHANG)
goto end;
retval = -ERESTARTSYS;
if (signal_pending(current))
goto end;
schedule();
goto repeat;
}
retval = -ECHILD;
end:
current->state = TASK_RUNNING;
remove_wait_queue(&current->signal->wait_chldexit,&wait);
if (infop) {
if (retval > 0)
retval = 0;
else {
/*
* For a WNOHANG return, clear out all the fields
* we would set so the user can easily tell the
* difference.
*/
if (!retval)
retval = put_user(0, &infop->si_signo);
if (!retval)
retval = put_user(0, &infop->si_errno);
if (!retval)
retval = put_user(0, &infop->si_code);
if (!retval)
retval = put_user(0, &infop->si_pid);
if (!retval)
retval = put_user(0, &infop->si_uid);
if (!retval)
retval = put_user(0, &infop->si_status);
}
}
return retval;
}
asmlinkage long sys_waitid(int which, pid_t upid,
struct siginfo __user *infop, int options,
struct rusage __user *ru)
{
struct pid *pid = NULL;
enum pid_type type;
long ret;
if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED))
return -EINVAL;
if (!(options & (WEXITED|WSTOPPED|WCONTINUED)))
return -EINVAL;
switch (which) {
case P_ALL:
type = PIDTYPE_MAX;
break;
case P_PID:
type = PIDTYPE_PID;
if (upid <= 0)
return -EINVAL;
break;
case P_PGID:
type = PIDTYPE_PGID;
if (upid <= 0)
return -EINVAL;
break;
default:
return -EINVAL;
}
if (type < PIDTYPE_MAX)
pid = find_get_pid(upid);
ret = do_wait(type, pid, options, infop, NULL, ru);
put_pid(pid);
/* avoid REGPARM breakage on x86: */
asmlinkage_protect(5, ret, which, upid, infop, options, ru);
return ret;
}
asmlinkage long sys_wait4(pid_t upid, int __user *stat_addr,
int options, struct rusage __user *ru)
{
struct pid *pid = NULL;
enum pid_type type;
long ret;
if (options & ~(WNOHANG|WUNTRACED|WCONTINUED|
__WNOTHREAD|__WCLONE|__WALL))
return -EINVAL;
if (upid == -1)
type = PIDTYPE_MAX;
else if (upid < 0) {
type = PIDTYPE_PGID;
pid = find_get_pid(-upid);
} else if (upid == 0) {
type = PIDTYPE_PGID;
pid = get_pid(task_pgrp(current));
} else /* upid > 0 */ {
type = PIDTYPE_PID;
pid = find_get_pid(upid);
}
ret = do_wait(type, pid, options | WEXITED, NULL, stat_addr, ru);
put_pid(pid);
/* avoid REGPARM breakage on x86: */
asmlinkage_protect(4, ret, upid, stat_addr, options, ru);
return ret;
}
#ifdef __ARCH_WANT_SYS_WAITPID
/*
* sys_waitpid() remains for compatibility. waitpid() should be
* implemented by calling sys_wait4() from libc.a.
*/
asmlinkage long sys_waitpid(pid_t pid, int __user *stat_addr, int options)
{
return sys_wait4(pid, stat_addr, options, NULL);
}
#endif