#include <linux/personality.h>
#include <linux/tty.h>
#include <linux/mnt_namespace.h>
+#include <linux/iocontext.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/fdtable.h>
#include <linux/binfmts.h>
#include <linux/nsproxy.h>
#include <linux/pid_namespace.h>
#include <linux/resource.h>
#include <linux/blkdev.h>
#include <linux/task_io_accounting_ops.h>
+#include <linux/tracehook.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>
__get_cpu_var(process_counts)--;
}
list_del_rcu(&p->thread_group);
- remove_parent(p);
+ list_del_init(&p->sibling);
}
/*
BUG_ON(!sig);
BUG_ON(!atomic_read(&sig->count));
- rcu_read_lock();
sighand = rcu_dereference(tsk->sighand);
spin_lock(&sighand->siglock);
sig->nivcsw += tsk->nivcsw;
sig->inblock += task_io_get_inblock(tsk);
sig->oublock += task_io_get_oublock(tsk);
+#ifdef CONFIG_TASK_XACCT
+ sig->rchar += tsk->rchar;
+ sig->wchar += tsk->wchar;
+ sig->syscr += tsk->syscr;
+ sig->syscw += tsk->syscw;
+#endif /* CONFIG_TASK_XACCT */
+#ifdef CONFIG_TASK_IO_ACCOUNTING
+ sig->ioac.read_bytes += tsk->ioac.read_bytes;
+ sig->ioac.write_bytes += tsk->ioac.write_bytes;
+ sig->ioac.cancelled_write_bytes +=
+ tsk->ioac.cancelled_write_bytes;
+#endif /* CONFIG_TASK_IO_ACCOUNTING */
sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
sig = NULL; /* Marker for below. */
}
__unhash_process(tsk);
+ /*
+ * Do this under ->siglock, we can race with another thread
+ * doing sigqueue_free() if we have SIGQUEUE_PREALLOC signals.
+ */
+ flush_sigqueue(&tsk->pending);
+
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);
put_task_struct(container_of(rhp, struct task_struct, rcu));
}
+/*
+ * Do final ptrace-related cleanup of a zombie being reaped.
+ *
+ * Called with write_lock(&tasklist_lock) held.
+ */
+static void ptrace_release_task(struct task_struct *p)
+{
+ BUG_ON(!list_empty(&p->ptraced));
+ ptrace_unlink(p);
+ BUG_ON(!list_empty(&p->ptrace_entry));
+}
+
void release_task(struct task_struct * p)
{
struct task_struct *leader;
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));
+ ptrace_release_task(p);
__exit_signal(p);
/*
ptrace_unlink(current);
/* Reparent to init */
- remove_parent(current);
current->real_parent = current->parent = kthreadd_task;
- add_parent(current);
+ list_move_tail(¤t->sibling, ¤t->real_parent->children);
/* Set the exit signal to SIGCHLD so we signal init on exit */
current->exit_signal = SIGCHLD;
* We don't want to have TIF_FREEZE set if the system-wide hibernation
* or suspend transition begins right now.
*/
- current->flags |= PF_NOFREEZE;
+ current->flags |= (PF_NOFREEZE | PF_KTHREAD);
if (current->nsproxy != &init_nsproxy) {
get_nsproxy(&init_nsproxy);
static void exit_mm(struct task_struct * tsk)
{
struct mm_struct *mm = tsk->mm;
+ struct core_state *core_state;
mm_release(tsk, mm);
if (!mm)
return;
/*
* Serialize with any possible pending coredump.
- * We must hold mmap_sem around checking core_waiters
+ * We must hold mmap_sem around checking core_state
* and clearing tsk->mm. The core-inducing thread
- * will increment core_waiters for each thread in the
+ * will increment ->nr_threads for each thread in the
* group with ->mm != NULL.
*/
down_read(&mm->mmap_sem);
- if (mm->core_waiters) {
+ core_state = mm->core_state;
+ if (core_state) {
+ struct core_thread self;
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);
+ self.task = tsk;
+ self.next = xchg(&core_state->dumper.next, &self);
+ /*
+ * Implies mb(), the result of xchg() must be visible
+ * to core_state->dumper.
+ */
+ if (atomic_dec_and_test(&core_state->nr_threads))
+ complete(&core_state->startup);
+
+ for (;;) {
+ set_task_state(tsk, TASK_UNINTERRUPTIBLE);
+ if (!self.task) /* see coredump_finish() */
+ break;
+ schedule();
+ }
+ __set_task_state(tsk, TASK_RUNNING);
down_read(&mm->mmap_sem);
}
atomic_inc(&mm->mm_count);
mmput(mm);
}
-static void
-reparent_thread(struct task_struct *p, struct task_struct *father, int traced)
+/*
+ * Return nonzero if @parent's children should reap themselves.
+ *
+ * Called with write_lock_irq(&tasklist_lock) held.
+ */
+static int ignoring_children(struct task_struct *parent)
{
- if (p->pdeath_signal)
- /* We already hold the tasklist_lock here. */
- group_send_sig_info(p->pdeath_signal, SEND_SIG_NOINFO, p);
+ int ret;
+ struct sighand_struct *psig = parent->sighand;
+ unsigned long flags;
+ spin_lock_irqsave(&psig->siglock, flags);
+ ret = (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN ||
+ (psig->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT));
+ spin_unlock_irqrestore(&psig->siglock, flags);
+ return ret;
+}
- /* 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 (ptrace_reparented(p))
- 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.
+/*
+ * Detach all tasks we were using ptrace on.
+ * Any that need to be release_task'd are put on the @dead list.
+ *
+ * Called with write_lock(&tasklist_lock) held.
+ */
+static void ptrace_exit(struct task_struct *parent, struct list_head *dead)
+{
+ struct task_struct *p, *n;
+ int ign = -1;
+
+ list_for_each_entry_safe(p, n, &parent->ptraced, ptrace_entry) {
+ __ptrace_unlink(p);
+
+ if (p->exit_state != EXIT_ZOMBIE)
+ continue;
+
+ /*
+ * If it's a zombie, our attachedness prevented normal
+ * parent notification or self-reaping. Do notification
+ * now if it would have happened earlier. If it should
+ * reap itself, add it to the @dead list. We can't call
+ * release_task() here because we already hold tasklist_lock.
+ *
+ * If it's our own child, there is no notification to do.
+ * But if our normal children self-reap, then this child
+ * was prevented by ptrace and we must reap it now.
*/
- p->ptrace = 0;
- remove_parent(p);
- p->parent = p->real_parent;
- add_parent(p);
+ if (!task_detached(p) && thread_group_empty(p)) {
+ if (!same_thread_group(p->real_parent, parent))
+ do_notify_parent(p, p->exit_signal);
+ else {
+ if (ign < 0)
+ ign = ignoring_children(parent);
+ if (ign)
+ p->exit_signal = -1;
+ }
+ }
- if (task_is_traced(p)) {
+ if (task_detached(p)) {
/*
- * If it was at a trace stop, turn it into
- * a normal stop since it's no longer being
- * traced.
+ * Mark it as in the process of being reaped.
*/
- ptrace_untrace(p);
+ p->exit_state = EXIT_DEAD;
+ list_add(&p->ptrace_entry, dead);
}
}
+}
+
+/*
+ * Finish up exit-time ptrace cleanup.
+ *
+ * Called without locks.
+ */
+static void ptrace_exit_finish(struct task_struct *parent,
+ struct list_head *dead)
+{
+ struct task_struct *p, *n;
+
+ BUG_ON(!list_empty(&parent->ptraced));
+
+ list_for_each_entry_safe(p, n, dead, ptrace_entry) {
+ list_del_init(&p->ptrace_entry);
+ release_task(p);
+ }
+}
+
+static void reparent_thread(struct task_struct *p, struct task_struct *father)
+{
+ if (p->pdeath_signal)
+ /* We already hold the tasklist_lock here. */
+ group_send_sig_info(p->pdeath_signal, SEND_SIG_NOINFO, p);
+
+ list_move_tail(&p->sibling, &p->real_parent->children);
/* If this is a threaded reparent there is no need to
* notify anyone anything has happened.
/* If we'd notified the old parent about this child's death,
* also notify the new parent.
*/
- if (!traced && p->exit_state == EXIT_ZOMBIE &&
+ if (!ptrace_reparented(p) &&
+ p->exit_state == EXIT_ZOMBIE &&
!task_detached(p) && thread_group_empty(p))
do_notify_parent(p, p->exit_signal);
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);
+ LIST_HEAD(ptrace_dead);
write_lock_irq(&tasklist_lock);
+ /*
+ * First clean up ptrace if we were using it.
+ */
+ ptrace_exit(father, &ptrace_dead);
+
do {
reaper = next_thread(reaper);
if (reaper == father) {
}
} 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 && !task_detached(p) &&
- thread_group_empty(p))
- do_notify_parent(p, p->exit_signal);
- }
-
- /*
- * if the ptraced child is a detached zombie 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 && task_detached(p)))
- 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);
+ if (p->parent == father) {
+ BUG_ON(p->ptrace);
+ p->parent = p->real_parent;
+ }
+ reparent_thread(p, father);
}
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);
- }
+ ptrace_exit_finish(father, &ptrace_dead);
}
/*
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);
- }
+ tracehook_report_exit(&code);
/*
* We're taking recursive faults here in do_exit. Safest is to just
return 0;
}
- /*
- * Do not consider detached threads that are
- * not ptraced:
- */
- if (task_detached(p) && !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:
return 0;
err = security_task_wait(p);
- if (likely(!err))
- return 1;
+ if (err)
+ return err;
- if (type != PIDTYPE_PID)
- return 0;
- /* This child was explicitly requested, abort */
- read_unlock(&tasklist_lock);
- return err;
+ return 1;
}
static int wait_noreap_copyout(struct task_struct *p, pid_t pid, uid_t uid,
* 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,
+static int wait_task_zombie(struct task_struct *p, int options,
struct siginfo __user *infop,
int __user *stat_addr, struct rusage __user *ru)
{
int retval, status, traced;
pid_t pid = task_pid_vnr(p);
- if (unlikely(noreap)) {
+ if (!likely(options & WEXITED))
+ return 0;
+
+ if (unlikely(options & WNOWAIT)) {
uid_t uid = p->uid;
int exit_code = p->exit_code;
int why, status;
psig->coublock +=
task_io_get_oublock(p) +
sig->oublock + sig->coublock;
+#ifdef CONFIG_TASK_XACCT
+ psig->rchar += p->rchar + sig->rchar;
+ psig->wchar += p->wchar + sig->wchar;
+ psig->syscr += p->syscr + sig->syscr;
+ psig->syscw += p->syscw + sig->syscw;
+#endif /* CONFIG_TASK_XACCT */
+#ifdef CONFIG_TASK_IO_ACCOUNTING
+ psig->ioac.read_bytes +=
+ p->ioac.read_bytes + sig->ioac.read_bytes;
+ psig->ioac.write_bytes +=
+ p->ioac.write_bytes + sig->ioac.write_bytes;
+ psig->ioac.cancelled_write_bytes +=
+ p->ioac.cancelled_write_bytes +
+ sig->ioac.cancelled_write_bytes;
+#endif /* CONFIG_TASK_IO_ACCOUNTING */
spin_unlock_irq(&p->parent->sighand->siglock);
}
* 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,
+static int wait_task_stopped(int ptrace, struct task_struct *p,
+ int options, 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;
+ if (!(options & WUNTRACED))
+ return 0;
+
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)
+ if (!ptrace && 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.
if (!exit_code)
goto unlock_sig;
- if (!noreap)
+ if (!unlikely(options & WNOWAIT))
p->exit_code = 0;
uid = p->uid;
*/
get_task_struct(p);
pid = task_pid_vnr(p);
- why = (p->ptrace & PT_PTRACED) ? CLD_TRAPPED : CLD_STOPPED;
+ why = ptrace ? CLD_TRAPPED : CLD_STOPPED;
read_unlock(&tasklist_lock);
- if (unlikely(noreap))
+ if (unlikely(options & WNOWAIT))
return wait_noreap_copyout(p, pid, uid,
why, exit_code,
infop, ru);
* 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,
+static int wait_task_continued(struct task_struct *p, int options,
struct siginfo __user *infop,
int __user *stat_addr, struct rusage __user *ru)
{
pid_t pid;
uid_t uid;
+ if (!unlikely(options & WCONTINUED))
+ return 0;
+
if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))
return 0;
spin_unlock_irq(&p->sighand->siglock);
return 0;
}
- if (!noreap)
+ if (!unlikely(options & WNOWAIT))
p->signal->flags &= ~SIGNAL_STOP_CONTINUED;
spin_unlock_irq(&p->sighand->siglock);
return retval;
}
+/*
+ * Consider @p for a wait by @parent.
+ *
+ * -ECHILD should be in *@notask_error before the first call.
+ * Returns nonzero for a final return, when we have unlocked tasklist_lock.
+ * Returns zero if the search for a child should continue;
+ * then *@notask_error is 0 if @p is an eligible child,
+ * or another error from security_task_wait(), or still -ECHILD.
+ */
+static int wait_consider_task(struct task_struct *parent, int ptrace,
+ struct task_struct *p, int *notask_error,
+ enum pid_type type, struct pid *pid, int options,
+ struct siginfo __user *infop,
+ int __user *stat_addr, struct rusage __user *ru)
+{
+ int ret = eligible_child(type, pid, options, p);
+ if (!ret)
+ return ret;
+
+ if (unlikely(ret < 0)) {
+ /*
+ * If we have not yet seen any eligible child,
+ * then let this error code replace -ECHILD.
+ * A permission error will give the user a clue
+ * to look for security policy problems, rather
+ * than for mysterious wait bugs.
+ */
+ if (*notask_error)
+ *notask_error = ret;
+ }
+
+ if (likely(!ptrace) && unlikely(p->ptrace)) {
+ /*
+ * This child is hidden by ptrace.
+ * We aren't allowed to see it now, but eventually we will.
+ */
+ *notask_error = 0;
+ return 0;
+ }
+
+ if (p->exit_state == EXIT_DEAD)
+ return 0;
+
+ /*
+ * We don't reap group leaders with subthreads.
+ */
+ if (p->exit_state == EXIT_ZOMBIE && !delay_group_leader(p))
+ return wait_task_zombie(p, options, infop, stat_addr, ru);
+
+ /*
+ * It's stopped or running now, so it might
+ * later continue, exit, or stop again.
+ */
+ *notask_error = 0;
+
+ if (task_is_stopped_or_traced(p))
+ return wait_task_stopped(ptrace, p, options,
+ infop, stat_addr, ru);
+
+ return wait_task_continued(p, options, infop, stat_addr, ru);
+}
+
+/*
+ * Do the work of do_wait() for one thread in the group, @tsk.
+ *
+ * -ECHILD should be in *@notask_error before the first call.
+ * Returns nonzero for a final return, when we have unlocked tasklist_lock.
+ * Returns zero if the search for a child should continue; then
+ * *@notask_error is 0 if there were any eligible children,
+ * or another error from security_task_wait(), or still -ECHILD.
+ */
+static int do_wait_thread(struct task_struct *tsk, int *notask_error,
+ enum pid_type type, struct pid *pid, int options,
+ struct siginfo __user *infop, int __user *stat_addr,
+ struct rusage __user *ru)
+{
+ struct task_struct *p;
+
+ list_for_each_entry(p, &tsk->children, sibling) {
+ /*
+ * Do not consider detached threads.
+ */
+ if (!task_detached(p)) {
+ int ret = wait_consider_task(tsk, 0, p, notask_error,
+ type, pid, options,
+ infop, stat_addr, ru);
+ if (ret)
+ return ret;
+ }
+ }
+
+ return 0;
+}
+
+static int ptrace_do_wait(struct task_struct *tsk, int *notask_error,
+ enum pid_type type, struct pid *pid, int options,
+ struct siginfo __user *infop, int __user *stat_addr,
+ struct rusage __user *ru)
+{
+ struct task_struct *p;
+
+ /*
+ * Traditionally we see ptrace'd stopped tasks regardless of options.
+ */
+ options |= WUNTRACED;
+
+ list_for_each_entry(p, &tsk->ptraced, ptrace_entry) {
+ int ret = wait_consider_task(tsk, 1, p, notask_error,
+ type, pid, options,
+ infop, stat_addr, ru);
+ if (ret)
+ return ret;
+ }
+
+ return 0;
+}
+
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;
+ int retval;
add_wait_queue(¤t->signal->wait_chldexit,&wait);
repeat:
- /* If there is nothing that can match our critier just get out */
+ /*
+ * If there is nothing that can match our critiera just get out.
+ * We will clear @retval to zero if we see any child that might later
+ * match our criteria, even if we are not able to reap it yet.
+ */
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;
- }
+ int tsk_result = do_wait_thread(tsk, &retval,
+ type, pid, options,
+ infop, stat_addr, ru);
+ if (!tsk_result)
+ tsk_result = ptrace_do_wait(tsk, &retval,
+ type, pid, options,
+ infop, stat_addr, ru);
+ if (tsk_result) {
+ /*
+ * tasklist_lock is unlocked and we have a final result.
+ */
+ retval = tsk_result;
+ goto end;
}
+
if (options & __WNOTHREAD)
break;
tsk = next_thread(tsk);
} while (tsk != current);
read_unlock(&tasklist_lock);
- if (flag) {
- if (options & WNOHANG)
- goto end;
+ if (!retval && !(options & WNOHANG)) {
retval = -ERESTARTSYS;
- if (signal_pending(current))
- goto end;
- schedule();
- goto repeat;
+ if (!signal_pending(current)) {
+ schedule();
+ goto repeat;
+ }
}
- retval = -ECHILD;
+
end:
current->state = TASK_RUNNING;
remove_wait_queue(¤t->signal->wait_chldexit,&wait);
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff