signal.c

来自「linux-2.4.29操作系统的源码」· C语言 代码 · 共 746 行 · 第 1/2 页

	    || __copy_to_user(&rt_sf->uc.uc_sigmask, oldset, sizeof(*oldset)))
		goto badframe;

	/* Save user registers on the stack */
	frame = &rt_sf->uc.uc_mcontext;
	if (save_user_regs(regs, frame, 0x6666))
		goto badframe;

	if (put_user(regs->gpr[1], (unsigned long *)newsp))
		goto badframe;
	regs->gpr[1] = newsp;
	regs->gpr[3] = sig;
	regs->gpr[4] = (unsigned long) &rt_sf->info;
	regs->gpr[5] = (unsigned long) &rt_sf->uc;
	regs->gpr[6] = (unsigned long) rt_sf;
	regs->nip = (unsigned long) ka->sa.sa_handler;
	regs->link = (unsigned long) frame->tramp;

	return;

badframe:
#if DEBUG_SIG
	printk("badframe in handle_rt_signal, regs=%p frame=%p newsp=%lx\n",
	       regs, frame, newsp);
#endif
	if (sig == SIGSEGV)
		ka->sa.sa_handler = SIG_DFL;
	force_sig(SIGSEGV, current);
}

static int do_setcontext(struct ucontext *ucp, struct pt_regs *regs)
{
	sigset_t set;
	struct mcontext *mcp;

	if (__copy_from_user(&set, &ucp->uc_sigmask, sizeof(set))
	    || __get_user(mcp, &ucp->uc_regs))
		return -EFAULT;
	restore_sigmask(&set);
	if (restore_user_regs(regs, mcp))
		return -EFAULT;

	return 0;
}

int sys_swapcontext(struct ucontext *old_ctx, struct ucontext *new_ctx,
		    int r5, int r6, int r7, int r8, struct pt_regs *regs)
{
	unsigned char tmp;

	if (old_ctx != NULL) {
		if (verify_area(VERIFY_WRITE, old_ctx, sizeof(*old_ctx))
		    || save_user_regs(regs, &old_ctx->uc_mcontext, 0)
		    || __copy_to_user(&old_ctx->uc_sigmask,
				      &current->blocked, sizeof(sigset_t))
		    || __put_user(&old_ctx->uc_mcontext, &old_ctx->uc_regs))
			return -EFAULT;
	}
	if (new_ctx == NULL)
		return 0;
	if (verify_area(VERIFY_READ, new_ctx, sizeof(*new_ctx))
	    || __get_user(tmp, (u8 *) new_ctx)
	    || __get_user(tmp, (u8 *) (new_ctx + 1) - 1))
		return -EFAULT;

	/*
	 * If we get a fault copying the context into the kernel's
	 * image of the user's registers, we can't just return -EFAULT
	 * because the user's registers will be corrupted.  For instance
	 * the NIP value may have been updated but not some of the
	 * other registers.  Given that we have done the verify_area
	 * and successfully read the first and last bytes of the region
	 * above, this should only happen in an out-of-memory situation
	 * or if another thread unmaps the region containing the context.
	 * We kill the task with a SIGSEGV in this situation.
	 */
	if (do_setcontext(new_ctx, regs))
		do_exit(SIGSEGV);
	syscall_direct_return(regs);
	/* doesn't actually return back to here */
	return 0;
}

int sys_rt_sigreturn(struct pt_regs *regs)
{
	struct rt_sigframe *rt_sf;
	stack_t st;

	rt_sf = (struct rt_sigframe *)(regs->gpr[1] + __SIGNAL_FRAMESIZE + 16);
	if (verify_area(VERIFY_READ, rt_sf, sizeof(struct rt_sigframe)))
		goto bad;
	if (do_setcontext(&rt_sf->uc, regs))
		goto bad;

	/*
	 * It's not clear whether or why it is desirable to save the
	 * sigaltstack setting on signal delivery and restore it on
	 * signal return.  But other architectures do this and we have
	 * always done it up until now so it is probably better not to
	 * change it.  -- paulus
	 */
	if (__copy_from_user(&st, &rt_sf->uc.uc_stack, sizeof(st)))
		goto bad;
	do_sigaltstack(&st, NULL, regs->gpr[1]);

	return regs->result;

 bad:
	force_sig(SIGSEGV, current);
	return 0;
}

/*
 * OK, we're invoking a handler
 */
static void
handle_signal(unsigned long sig, struct k_sigaction *ka,
	      siginfo_t *info, sigset_t *oldset, struct pt_regs * regs,
	      unsigned long newsp)
{
	struct sigcontext *sc;
	struct sigregs *frame;
	unsigned long origsp = newsp;

	/* Set up Signal Frame */
	newsp -= sizeof(struct sigregs);
	frame = (struct sigregs *) newsp;

	/* Put a sigcontext on the stack */
	newsp -= sizeof(*sc);
	sc = (struct sigcontext *) newsp;

	/* create a stack frame for the caller of the handler */
	newsp -= __SIGNAL_FRAMESIZE;

	if (verify_area(VERIFY_WRITE, (void *) newsp, origsp - newsp))
		goto badframe;

#if _NSIG != 64
#error "Please adjust handle_signal()"
#endif
	if (__put_user((unsigned long) ka->sa.sa_handler, &sc->handler)
	    || __put_user(oldset->sig[0], &sc->oldmask)
	    || __put_user(oldset->sig[1], &sc->_unused[3])
	    || __put_user((struct pt_regs *)frame, &sc->regs)
	    || __put_user(sig, &sc->signal))
		goto badframe;

	if (save_user_regs(regs, &frame->mctx, 0x7777))
		goto badframe;

	if (put_user(regs->gpr[1], (unsigned long *)newsp))
		goto badframe;
	regs->gpr[1] = newsp;
	regs->gpr[3] = sig;
	regs->gpr[4] = (unsigned long) sc;
	regs->nip = (unsigned long) ka->sa.sa_handler;
	regs->link = (unsigned long) frame->mctx.tramp;

	return;

badframe:
#if DEBUG_SIG
	printk("badframe in handle_signal, regs=%p frame=%lx newsp=%lx\n",
	       regs, frame, *newspp);
#endif
	if (sig == SIGSEGV)
		ka->sa.sa_handler = SIG_DFL;
	force_sig(SIGSEGV, current);
}

/*
 * Do a signal return; undo the signal stack.
 */
int sys_sigreturn(struct pt_regs *regs)
{
	struct sigcontext *sc, sigctx;
	struct mcontext *sr;
	int ret;
	sigset_t set;

	sc = (struct sigcontext *)(regs->gpr[1] + __SIGNAL_FRAMESIZE);
	if (copy_from_user(&sigctx, sc, sizeof(sigctx)))
		goto badframe;

	set.sig[0] = sigctx.oldmask;
	set.sig[1] = sigctx._unused[3];
	restore_sigmask(&set);

	sr = (struct mcontext *) sigctx.regs;
	if (verify_area(VERIFY_READ, sr, sizeof(*sr))
	    || restore_user_regs(regs, sr))
		goto badframe;

	ret = regs->result;

	return ret;

badframe:
	force_sig(SIGSEGV, current);
	return 0;
}	

static int get_signal_to_deliver(struct siginfo *infop, struct pt_regs *regs)
{
	struct k_sigaction *ka;
	int signr;

	for (;;) {
		spin_lock_irq(&current->sigmask_lock);
		signr = dequeue_signal(&current->blocked, infop);
		spin_unlock_irq(&current->sigmask_lock);

		if (!signr)
			return 0;

		if ((current->ptrace & PT_PTRACED) && signr != SIGKILL) {
			/* Let the debugger run.  */
			current->exit_code = signr;
			current->state = TASK_STOPPED;
			notify_parent(current, SIGCHLD);
			schedule();

			/* We're back.  Did the debugger cancel the sig?  */
			if (!(signr = current->exit_code))
				continue;
			current->exit_code = 0;

			/* The debugger continued.  Ignore SIGSTOP.  */
			if (signr == SIGSTOP)
				continue;

			/* Update the siginfo structure.  Is this good?  */
			if (signr != infop->si_signo) {
				infop->si_signo = signr;
				infop->si_errno = 0;
				infop->si_code = SI_USER;
				infop->si_pid = current->p_pptr->pid;
				infop->si_uid = current->p_pptr->uid;
			}

			/* If the (new) signal is now blocked, requeue it.  */
			if (sigismember(&current->blocked, signr)) {
				send_sig_info(signr, infop, current);
				continue;
			}
		}

		ka = &current->sig->action[signr-1];
		if (ka->sa.sa_handler == SIG_IGN) {
			if (signr != SIGCHLD)
				continue;
			/* Check for SIGCHLD: it's special.  */
			while (sys_wait4(-1, NULL, WNOHANG, NULL) > 0)
				/* nothing */;
			continue;
		}

		if (ka->sa.sa_handler == SIG_DFL) {
			int exit_code = signr;

			/* Init gets no signals it doesn't want.  */
			if (current->pid == 1)
				continue;

			switch (signr) {
			case SIGCONT: case SIGCHLD: case SIGWINCH: case SIGURG:
				continue;

			case SIGTSTP: case SIGTTIN: case SIGTTOU:
				if (is_orphaned_pgrp(current->pgrp))
					continue;
				/* FALLTHRU */

			case SIGSTOP:
				current->state = TASK_STOPPED;
				current->exit_code = signr;
				if (!(current->p_pptr->sig->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDSTOP))
					notify_parent(current, SIGCHLD);
				schedule();
				continue;

			case SIGQUIT: case SIGILL: case SIGTRAP:
			case SIGABRT: case SIGFPE: case SIGSEGV:
			case SIGBUS: case SIGSYS: case SIGXCPU: case SIGXFSZ:
				if (do_coredump(signr, regs))
					exit_code |= 0x80;
				/* FALLTHRU */

			default:
				sig_exit(signr, exit_code, infop);
				/* NOTREACHED */
			}
		}
		return signr;
	}
}

/*
 * 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.
 */
int do_signal(sigset_t *oldset, struct pt_regs *regs)
{
	siginfo_t info;
	struct k_sigaction *ka;
	unsigned long frame, newsp;
	int signr;

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

	newsp = frame = 0;

	signr = get_signal_to_deliver(&info, regs);

	ka = (signr == 0)? NULL: &current->sig->action[signr-1];

	if (regs->trap == 0xc00) {		/* system call */
		switch ((int) regs->result) {
		case -ERESTARTSYS:
			if (signr == 0 || (ka->sa.sa_flags & SA_RESTART))
				goto retry;
			/* fall through */
		case -ERESTARTNOHAND:
			if (signr > 0) {
				/* make the system call return an EINTR */
				regs->result = -EINTR;
				break;
			}
			/* fall through */
		case -ERESTARTNOINTR:
		retry:
			/* Back up & retry system call */
			regs->gpr[3] = regs->orig_gpr3;
			regs->nip -= 4;
			regs->result = 0;
			break;
		}
	}

	if (signr == 0)
		return 0;		/* no signals delivered */

	if ((ka->sa.sa_flags & SA_ONSTACK) && current->sas_ss_size
	    && !on_sig_stack(regs->gpr[1]))
		newsp = current->sas_ss_sp + current->sas_ss_size;
	else
		newsp = regs->gpr[1];
	newsp &= ~0xfUL;

	/* Whee!  Actually deliver the signal.  */
	if (ka->sa.sa_flags & SA_SIGINFO)
		handle_rt_signal(signr, ka, &info, oldset, regs, newsp);
	else
		handle_signal(signr, ka, &info, oldset, regs, newsp);

	if (ka->sa.sa_flags & SA_ONESHOT)
		ka->sa.sa_handler = SIG_DFL;

	if (!(ka->sa.sa_flags & SA_NODEFER)) {
		spin_lock_irq(&current->sigmask_lock);
		sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
		sigaddset(&current->blocked, signr);
		recalc_sigpending(current);
		spin_unlock_irq(&current->sigmask_lock);
	}

	return 1;
}