signal.c

linux-2.6.15.6

 * Check whether the register-backing store is already on the signal stack.
 */
static inline int
rbs_on_sig_stack (unsigned long bsp)
{
	return (bsp - current->sas_ss_sp < current->sas_ss_size);
}

static long
force_sigsegv_info (int sig, void __user *addr)
{
	unsigned long flags;
	struct siginfo si;

	if (sig == SIGSEGV) {
		/*
		 * Acquiring siglock around the sa_handler-update is almost
		 * certainly overkill, but this isn't a
		 * performance-critical path and I'd rather play it safe
		 * here than having to debug a nasty race if and when
		 * something changes in kernel/signal.c that would make it
		 * no longer safe to modify sa_handler without holding the
		 * lock.
		 */
		spin_lock_irqsave(&current->sighand->siglock, flags);
		current->sighand->action[sig - 1].sa.sa_handler = SIG_DFL;
		spin_unlock_irqrestore(&current->sighand->siglock, flags);
	}
	si.si_signo = SIGSEGV;
	si.si_errno = 0;
	si.si_code = SI_KERNEL;
	si.si_pid = current->pid;
	si.si_uid = current->uid;
	si.si_addr = addr;
	force_sig_info(SIGSEGV, &si, current);
	return 0;
}

static long
setup_frame (int sig, struct k_sigaction *ka, siginfo_t *info, sigset_t *set,
	     struct sigscratch *scr)
{
	extern char __kernel_sigtramp[];
	unsigned long tramp_addr, new_rbs = 0, new_sp;
	struct sigframe __user *frame;
	long err;

	new_sp = scr->pt.r12;
	tramp_addr = (unsigned long) __kernel_sigtramp;
	if ((ka->sa.sa_flags & SA_ONSTACK) && sas_ss_flags(new_sp) == 0) {
		new_sp = current->sas_ss_sp + current->sas_ss_size;
		/*
		 * We need to check for the register stack being on the signal stack
		 * separately, because it's switched separately (memory stack is switched
		 * in the kernel, register stack is switched in the signal trampoline).
		 */
		if (!rbs_on_sig_stack(scr->pt.ar_bspstore))
			new_rbs = (current->sas_ss_sp + sizeof(long) - 1) & ~(sizeof(long) - 1);
	}
	frame = (void __user *) ((new_sp - sizeof(*frame)) & -STACK_ALIGN);

	if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
		return force_sigsegv_info(sig, frame);

	err  = __put_user(sig, &frame->arg0);
	err |= __put_user(&frame->info, &frame->arg1);
	err |= __put_user(&frame->sc, &frame->arg2);
	err |= __put_user(new_rbs, &frame->sc.sc_rbs_base);
	err |= __put_user(0, &frame->sc.sc_loadrs);	/* initialize to zero */
	err |= __put_user(ka->sa.sa_handler, &frame->handler);

	err |= copy_siginfo_to_user(&frame->info, info);

	err |= __put_user(current->sas_ss_sp, &frame->sc.sc_stack.ss_sp);
	err |= __put_user(current->sas_ss_size, &frame->sc.sc_stack.ss_size);
	err |= __put_user(sas_ss_flags(scr->pt.r12), &frame->sc.sc_stack.ss_flags);
	err |= setup_sigcontext(&frame->sc, set, scr);

	if (unlikely(err))
		return force_sigsegv_info(sig, frame);

	scr->pt.r12 = (unsigned long) frame - 16;	/* new stack pointer */
	scr->pt.ar_fpsr = FPSR_DEFAULT;			/* reset fpsr for signal handler */
	scr->pt.cr_iip = tramp_addr;
	ia64_psr(&scr->pt)->ri = 0;			/* start executing in first slot */
	ia64_psr(&scr->pt)->be = 0;			/* force little-endian byte-order */
	/*
	 * Force the interruption function mask to zero.  This has no effect when a
	 * system-call got interrupted by a signal (since, in that case, scr->pt_cr_ifs is
	 * ignored), but it has the desirable effect of making it possible to deliver a
	 * signal with an incomplete register frame (which happens when a mandatory RSE
	 * load faults).  Furthermore, it has no negative effect on the getting the user's
	 * dirty partition preserved, because that's governed by scr->pt.loadrs.
	 */
	scr->pt.cr_ifs = (1UL << 63);

	/*
	 * Note: this affects only the NaT bits of the scratch regs (the ones saved in
	 * pt_regs), which is exactly what we want.
	 */
	scr->scratch_unat = 0; /* ensure NaT bits of r12 is clear */

#if DEBUG_SIG
	printk("SIG deliver (%s:%d): sig=%d sp=%lx ip=%lx handler=%p\n",
	       current->comm, current->pid, sig, scr->pt.r12, frame->sc.sc_ip, frame->handler);
#endif
	return 1;
}

static long
handle_signal (unsigned long sig, struct k_sigaction *ka, siginfo_t *info, sigset_t *oldset,
	       struct sigscratch *scr)
{
	if (IS_IA32_PROCESS(&scr->pt)) {
		/* send signal to IA-32 process */
		if (!ia32_setup_frame1(sig, ka, info, oldset, &scr->pt))
			return 0;
	} else
		/* send signal to IA-64 process */
		if (!setup_frame(sig, ka, info, oldset, scr))
			return 0;

	spin_lock_irq(&current->sighand->siglock);
	sigorsets(&current->blocked, &current->blocked, &ka->sa.sa_mask);
	if (!(ka->sa.sa_flags & SA_NODEFER))
		sigaddset(&current->blocked, sig);
	recalc_sigpending();
	spin_unlock_irq(&current->sighand->siglock);
	return 1;
}

/*
 * Note that `init' is a special process: it doesn't get signals it doesn't want to
 * handle.  Thus you cannot kill init even with a SIGKILL even by mistake.
 */
long
ia64_do_signal (sigset_t *oldset, struct sigscratch *scr, long in_syscall)
{
	struct k_sigaction ka;
	siginfo_t info;
	long restart = in_syscall;
	long errno = scr->pt.r8;
#	define ERR_CODE(c)	(IS_IA32_PROCESS(&scr->pt) ? -(c) : (c))

	/*
	 * In the ia64_leave_kernel code path, we want the common case to go fast, which
	 * is why we may in certain cases get here from kernel mode. Just return without
	 * doing anything if so.
	 */
	if (!user_mode(&scr->pt))
		return 0;

	if (!oldset)
		oldset = &current->blocked;

	/*
	 * This only loops in the rare cases of handle_signal() failing, in which case we
	 * need to push through a forced SIGSEGV.
	 */
	while (1) {
		int signr = get_signal_to_deliver(&info, &ka, &scr->pt, NULL);

		/*
		 * get_signal_to_deliver() may have run a debugger (via notify_parent())
		 * and the debugger may have modified the state (e.g., to arrange for an
		 * inferior call), thus it's important to check for restarting _after_
		 * get_signal_to_deliver().
		 */
		if (IS_IA32_PROCESS(&scr->pt)) {
			if (in_syscall) {
				if (errno >= 0)
					restart = 0;
				else
					errno = -errno;
			}
		} else if ((long) scr->pt.r10 != -1)
			/*
			 * A system calls has to be restarted only if one of the error codes
			 * ERESTARTNOHAND, ERESTARTSYS, or ERESTARTNOINTR is returned.  If r10
			 * isn't -1 then r8 doesn't hold an error code and we don't need to
			 * restart the syscall, so we can clear the "restart" flag here.
			 */
			restart = 0;

		if (signr <= 0)
			break;

		if (unlikely(restart)) {
			switch (errno) {
			      case ERESTART_RESTARTBLOCK:
			      case ERESTARTNOHAND:
				scr->pt.r8 = ERR_CODE(EINTR);
				/* note: scr->pt.r10 is already -1 */
				break;

			      case ERESTARTSYS:
				if ((ka.sa.sa_flags & SA_RESTART) == 0) {
					scr->pt.r8 = ERR_CODE(EINTR);
					/* note: scr->pt.r10 is already -1 */
					break;
				}
			      case ERESTARTNOINTR:
				if (IS_IA32_PROCESS(&scr->pt)) {
					scr->pt.r8 = scr->pt.r1;
					scr->pt.cr_iip -= 2;
				} else
					ia64_decrement_ip(&scr->pt);
				restart = 0; /* don't restart twice if handle_signal() fails... */
			}
		}

		/*
		 * Whee!  Actually deliver the signal.  If the delivery failed, we need to
		 * continue to iterate in this loop so we can deliver the SIGSEGV...
		 */
		if (handle_signal(signr, &ka, &info, oldset, scr))
			return 1;
	}

	/* Did we come from a system call? */
	if (restart) {
		/* Restart the system call - no handlers present */
		if (errno == ERESTARTNOHAND || errno == ERESTARTSYS || errno == ERESTARTNOINTR
		    || errno == ERESTART_RESTARTBLOCK)
		{
			if (IS_IA32_PROCESS(&scr->pt)) {
				scr->pt.r8 = scr->pt.r1;
				scr->pt.cr_iip -= 2;
				if (errno == ERESTART_RESTARTBLOCK)
					scr->pt.r8 = 0;	/* x86 version of __NR_restart_syscall */
			} else {
				/*
				 * Note: the syscall number is in r15 which is saved in
				 * pt_regs so all we need to do here is adjust ip so that
				 * the "break" instruction gets re-executed.
				 */
				ia64_decrement_ip(&scr->pt);
				if (errno == ERESTART_RESTARTBLOCK)
					scr->pt.r15 = __NR_restart_syscall;
			}
		}
	}
	return 0;
}

/* Set a delayed signal that was detected in MCA/INIT/NMI/PMI context where it
 * could not be delivered.  It is important that the target process is not
 * allowed to do any more work in user space.  Possible cases for the target
 * process:
 *
 * - It is sleeping and will wake up soon.  Store the data in the current task,
 *   the signal will be sent when the current task returns from the next
 *   interrupt.
 *
 * - It is running in user context.  Store the data in the current task, the
 *   signal will be sent when the current task returns from the next interrupt.
 *
 * - It is running in kernel context on this or another cpu and will return to
 *   user context.  Store the data in the target task, the signal will be sent
 *   to itself when the target task returns to user space.
 *
 * - It is running in kernel context on this cpu and will sleep before
 *   returning to user context.  Because this is also the current task, the
 *   signal will not get delivered and the task could sleep indefinitely.
 *   Store the data in the idle task for this cpu, the signal will be sent
 *   after the idle task processes its next interrupt.
 *
 * To cover all cases, store the data in the target task, the current task and
 * the idle task on this cpu.  Whatever happens, the signal will be delivered
 * to the target task before it can do any useful user space work.  Multiple
 * deliveries have no unwanted side effects.
 *
 * Note: This code is executed in MCA/INIT/NMI/PMI context, with interrupts
 * disabled.  It must not take any locks nor use kernel structures or services
 * that require locks.
 */

/* To ensure that we get the right pid, check its start time.  To avoid extra
 * include files in thread_info.h, convert the task start_time to unsigned long,
 * giving us a cycle time of > 580 years.
 */
static inline unsigned long
start_time_ul(const struct task_struct *t)
{
	return t->start_time.tv_sec * NSEC_PER_SEC + t->start_time.tv_nsec;
}

void
set_sigdelayed(pid_t pid, int signo, int code, void __user *addr)
{
	struct task_struct *t;
	unsigned long start_time =  0;
	int i;

	for (i = 1; i <= 3; ++i) {
		switch (i) {
		case 1:
			t = find_task_by_pid(pid);
			if (t)
				start_time = start_time_ul(t);
			break;
		case 2:
			t = current;
			break;
		default:
			t = idle_task(smp_processor_id());
			break;
		}

		if (!t)
			return;
		t->thread_info->sigdelayed.signo = signo;
		t->thread_info->sigdelayed.code = code;
		t->thread_info->sigdelayed.addr = addr;
		t->thread_info->sigdelayed.start_time = start_time;
		t->thread_info->sigdelayed.pid = pid;
		wmb();
		set_tsk_thread_flag(t, TIF_SIGDELAYED);
	}
}

/* Called from entry.S when it detects TIF_SIGDELAYED, a delayed signal that
 * was detected in MCA/INIT/NMI/PMI context where it could not be delivered.
 */

void
do_sigdelayed(void)
{
	struct siginfo siginfo;
	pid_t pid;
	struct task_struct *t;

	clear_thread_flag(TIF_SIGDELAYED);
	memset(&siginfo, 0, sizeof(siginfo));
	siginfo.si_signo = current_thread_info()->sigdelayed.signo;
	siginfo.si_code = current_thread_info()->sigdelayed.code;
	siginfo.si_addr = current_thread_info()->sigdelayed.addr;
	pid = current_thread_info()->sigdelayed.pid;
	t = find_task_by_pid(pid);
	if (!t)
		return;
	if (current_thread_info()->sigdelayed.start_time != start_time_ul(t))
		return;
	force_sig_info(siginfo.si_signo, &siginfo, t);
}