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tracehook: tracehook_consider_ignored_signal

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This defines tracehook_consider_ignored_signal() has a fine-grained hook
for deciding to prevent the normal short-circuit of sending an ignored
signal, as ptrace does.  There is no change, only cleanup.

Signed-off-by: Roland McGrath <roland@redhat.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Reviewed-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Roland McGrath 2008-07-25 19:45:51 -07:00 committed by Linus Torvalds
parent c45aea2761
commit 35de254dc6
2 changed files with 35 additions and 11 deletions
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19
include/linux/tracehook.h
View file

@ -312,4 +312,23 @@ static inline void tracehook_signal_handler(int sig, siginfo_t *info,
ptrace_notify(SIGTRAP);
}
/**
* tracehook_consider_ignored_signal - suppress short-circuit of ignored signal
* @task: task receiving the signal
* @sig: signal number being sent
* @handler: %SIG_IGN or %SIG_DFL
*
* Return zero iff tracing doesn't care to examine this ignored signal,
* so it can short-circuit normal delivery and never even get queued.
* Either @handler is %SIG_DFL and @sig's default is ignore, or it's %SIG_IGN.
*
* Called with @task->sighand->siglock held.
*/
static inline int tracehook_consider_ignored_signal(struct task_struct *task,
int sig,
void __user *handler)
{
return (task_ptrace(task) & PT_PTRACED) != 0;
}
#endif /* <linux/tracehook.h> */

27
kernel/signal.c
View file

@ -22,6 +22,7 @@
#include <linux/ptrace.h>
#include <linux/signal.h>
#include <linux/signalfd.h>
#include <linux/tracehook.h>
#include <linux/capability.h>
#include <linux/freezer.h>
#include <linux/pid_namespace.h>
@ -39,24 +40,21 @@
static struct kmem_cache *sigqueue_cachep;
static int __sig_ignored(struct task_struct *t, int sig)
static void __user *sig_handler(struct task_struct *t, int sig)
{
void __user *handler;
return t->sighand->action[sig - 1].sa.sa_handler;
}
static int sig_handler_ignored(void __user *handler, int sig)
{
/* Is it explicitly or implicitly ignored? */
handler = t->sighand->action[sig - 1].sa.sa_handler;
return handler == SIG_IGN ||
(handler == SIG_DFL && sig_kernel_ignore(sig));
}
static int sig_ignored(struct task_struct *t, int sig)
{
/*
* Tracers always want to know about signals..
*/
if (t->ptrace & PT_PTRACED)
return 0;
void __user *handler;
/*
* Blocked signals are never ignored, since the
@ -66,7 +64,14 @@ static int sig_ignored(struct task_struct *t, int sig)
if (sigismember(&t->blocked, sig) || sigismember(&t->real_blocked, sig))
return 0;
return __sig_ignored(t, sig);
handler = sig_handler(t, sig);
if (!sig_handler_ignored(handler, sig))
return 0;
/*
* Tracers may want to know about even ignored signals.
*/
return !tracehook_consider_ignored_signal(t, sig, handler);
}
/*
@ -2298,7 +2303,7 @@ int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
* (for example, SIGCHLD), shall cause the pending signal to
* be discarded, whether or not it is blocked"
*/
if (__sig_ignored(t, sig)) {
if (sig_handler_ignored(sig_handler(t, sig), sig)) {
sigemptyset(&mask);
sigaddset(&mask, sig);
rm_from_queue_full(&mask, &t->signal->shared_pending);