signal.c

linux内核源码

setup_frame(int sig, struct k_sigaction *ka,  sigset_t *set,
	    struct pt_regs * regs)
{
	int err;
	unsigned long return_ip;
	struct signal_frame __user *frame;

	err = 0;
	frame = get_sigframe(ka, regs, sizeof(*frame));

	if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
		goto give_sigsegv;

	err |= setup_sigcontext(&frame->sc, regs, set->sig[0]);

	if (err)
		goto give_sigsegv;

	if (_NSIG_WORDS > 1) {
		err |= __copy_to_user(frame->extramask, &set->sig[1],
				      sizeof(frame->extramask));
	}

	if (err)
		goto give_sigsegv;

	/*
	 * Set up to return from user-space. If provided, use a stub
	 * already located in user-space.
	 */
	if (ka->sa.sa_flags & SA_RESTORER) {
		return_ip = (unsigned long)ka->sa.sa_restorer;
	} else {
		/* Trampoline - the desired return ip is in the signal return page. */
		return_ip = cris_signal_return_page;

		/*
		 * This is movu.w __NR_sigreturn, r9; break 13;
		 *
		 * WE DO NOT USE IT ANY MORE! It's only left here for historical
		 * reasons and because gdb uses it as a signature to notice
		 * signal handler stack frames.
		 */
		err |= __put_user(0x9c5f,         (short __user*)(frame->retcode+0));
		err |= __put_user(__NR_sigreturn, (short __user*)(frame->retcode+2));
		err |= __put_user(0xe93d,         (short __user*)(frame->retcode+4));
	}

	if (err)
		goto give_sigsegv;

	/*
	 * Set up registers for signal handler.
	 *
	 * Where the code enters now.
	 * Where the code enter later.
	 * First argument, signo.
	 */
	regs->erp = (unsigned long) ka->sa.sa_handler;
	regs->srp = return_ip;
	regs->r10 = sig;

	/* Actually move the USP to reflect the stacked frame. */
	wrusp((unsigned long)frame);

	return;

give_sigsegv:
	if (sig == SIGSEGV)
		ka->sa.sa_handler = SIG_DFL;

	force_sig(SIGSEGV, current);
}

static void
setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
	       sigset_t *set, struct pt_regs * regs)
{
	int err;
	unsigned long return_ip;
	struct rt_signal_frame __user *frame;

	err = 0;
	frame = get_sigframe(ka, regs, sizeof(*frame));

	if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
		goto give_sigsegv;

	/* TODO: what is the current->exec_domain stuff and invmap ? */

	err |= __put_user(&frame->info, &frame->pinfo);
	err |= __put_user(&frame->uc, &frame->puc);
	err |= copy_siginfo_to_user(&frame->info, info);

	if (err)
		goto give_sigsegv;

	/* Clear all the bits of the ucontext we don't use.  */
	err |= __clear_user(&frame->uc, offsetof(struct ucontext, uc_mcontext));
	err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, set->sig[0]);
	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));

	if (err)
		goto give_sigsegv;

	/*
	 * Set up to return from user-space. If provided, use a stub
	 * already located in user-space.
	 */
	if (ka->sa.sa_flags & SA_RESTORER) {
		return_ip = (unsigned long) ka->sa.sa_restorer;
	} else {
		/* Trampoline - the desired return ip is in the signal return page. */
		return_ip = cris_signal_return_page + 6;

		/*
		 * This is movu.w __NR_rt_sigreturn, r9; break 13;
		 *
		 * WE DO NOT USE IT ANY MORE! It's only left here for historical
		 * reasons and because gdb uses it as a signature to notice
		 * signal handler stack frames.
		 */
		err |= __put_user(0x9c5f, (short __user*)(frame->retcode+0));

		err |= __put_user(__NR_rt_sigreturn,
				  (short __user*)(frame->retcode+2));

		err |= __put_user(0xe93d, (short __user*)(frame->retcode+4));
	}

	if (err)
		goto give_sigsegv;

	/*
	 * Set up registers for signal handler.
	 *
	 * Where the code enters now.
	 * Where the code enters later.
	 * First argument is signo.
	 * Second argument is (siginfo_t *).
	 * Third argument is unused.
	 */
	regs->erp = (unsigned long) ka->sa.sa_handler;
	regs->srp = return_ip;
	regs->r10 = sig;
	regs->r11 = (unsigned long) &frame->info;
	regs->r12 = 0;

	/* Actually move the usp to reflect the stacked frame. */
	wrusp((unsigned long)frame);

	return;

give_sigsegv:
	if (sig == SIGSEGV)
		ka->sa.sa_handler = SIG_DFL;

	force_sig(SIGSEGV, current);
}

/* Invoke a singal handler to, well, handle the signal. */
static inline void
handle_signal(int canrestart, unsigned long sig,
	      siginfo_t *info, struct k_sigaction *ka,
              sigset_t *oldset, struct pt_regs * regs)
{
	/* Check if this got called from a system call. */
	if (canrestart) {
		/* If so, check system call restarting. */
		switch (regs->r10) {
			case -ERESTART_RESTARTBLOCK:
			case -ERESTARTNOHAND:
				/*
				 * This means that the syscall should
				 * only be restarted if there was no
				 * handler for the signal, and since
				 * this point isn't reached unless
				 * there is a handler, there's no need
				 * to restart.
				 */
				regs->r10 = -EINTR;
				break;

                        case -ERESTARTSYS:
				/*
				 * This means restart the syscall if
                                 * there is no handler, or the handler
                                 * was registered with SA_RESTART.
				 */
				if (!(ka->sa.sa_flags & SA_RESTART)) {
					regs->r10 = -EINTR;
					break;
				}

				/* Fall through. */

			case -ERESTARTNOINTR:
				/*
				 * This means that the syscall should
                                 * be called again after the signal
                                 * handler returns.
				 */
				RESTART_CRIS_SYS(regs);
				break;
                }
        }

	/* Set up the stack frame. */
	if (ka->sa.sa_flags & SA_SIGINFO)
		setup_rt_frame(sig, ka, info, oldset, regs);
	else
		setup_frame(sig, ka, oldset, regs);

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

	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);
}

/*
 * 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.
 *
 * Also note that the regs structure given here as an argument, is the latest
 * pushed pt_regs. It may or may not be the same as the first pushed registers
 * when the initial usermode->kernelmode transition took place. Therefore
 * we can use user_mode(regs) to see if we came directly from kernel or user
 * mode below.
 */
int
do_signal(int canrestart, sigset_t *oldset, struct pt_regs *regs)
{
	int signr;
	siginfo_t info;
        struct k_sigaction ka;

	/*
	 * The common case should go fast, which is why this point is
	 * reached from kernel-mode. If that's the case, just return
	 * without doing anything.
	 */
	if (!user_mode(regs))
		return 1;

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

	signr = get_signal_to_deliver(&info, &ka, regs, NULL);

	if (signr > 0) {
		/* Deliver the signal. */
		handle_signal(canrestart, signr, &info, &ka, oldset, regs);
		return 1;
	}

	/* Got here from a system call? */
	if (canrestart) {
		/* Restart the system call - no handlers present. */
		if (regs->r10 == -ERESTARTNOHAND ||
		    regs->r10 == -ERESTARTSYS ||
		    regs->r10 == -ERESTARTNOINTR) {
			RESTART_CRIS_SYS(regs);
		}

		if (regs->r10 == -ERESTART_RESTARTBLOCK){
			regs->r10 = __NR_restart_syscall;
			regs->erp -= 2;
		}
	}

	return 0;
}

asmlinkage void
ugdb_trap_user(struct thread_info *ti, int sig)
{
	if (((user_regs(ti)->exs & 0xff00) >> 8) != SINGLE_STEP_INTR_VECT) {
		/* Zero single-step PC if the reason we stopped wasn't a single
		   step exception. This is to avoid relying on it when it isn't
		   reliable. */
		user_regs(ti)->spc = 0;
	}
	/* FIXME: Filter out false h/w breakpoint hits (i.e. EDA
	   not within any configured h/w breakpoint range). Synchronize with
	   what already exists for kernel debugging.  */
	if (((user_regs(ti)->exs & 0xff00) >> 8) == BREAK_8_INTR_VECT) {
		/* Break 8: subtract 2 from ERP unless in a delay slot. */
		if (!(user_regs(ti)->erp & 0x1))
			user_regs(ti)->erp -= 2;
	}
	sys_kill(ti->task->pid, sig);
}

void
keep_debug_flags(unsigned long oldccs, unsigned long oldspc,
		 struct pt_regs *regs)
{
	if (oldccs & (1 << Q_CCS_BITNR)) {
		/* Pending single step due to single-stepping the break 13
		   in the signal trampoline: keep the Q flag. */
		regs->ccs |= (1 << Q_CCS_BITNR);
		/* S flag should be set - complain if it's not. */
		if (!(oldccs & (1 << (S_CCS_BITNR + CCS_SHIFT)))) {
			printk("Q flag but no S flag?");
		}
		regs->ccs |= (1 << (S_CCS_BITNR + CCS_SHIFT));
		/* Assume the SPC is valid and interesting. */
		regs->spc = oldspc;

	} else if (oldccs & (1 << (S_CCS_BITNR + CCS_SHIFT))) {
		/* If a h/w bp was set in the signal handler we need
		   to keep the S flag. */
		regs->ccs |= (1 << (S_CCS_BITNR + CCS_SHIFT));
		/* Don't keep the old SPC though; if we got here due to
		   a single-step, the Q flag should have been set. */
	} else if (regs->spc) {
		/* If we were single-stepping *before* the signal was taken,
		   we don't want to restore that state now, because GDB will
		   have forgotten all about it. */
		regs->spc = 0;
		regs->ccs &= ~(1 << (S_CCS_BITNR + CCS_SHIFT));
	}
}

/* Set up the trampolines on the signal return page. */
int __init
cris_init_signal(void)
{
	u16* data = kmalloc(PAGE_SIZE, GFP_KERNEL);

	/* This is movu.w __NR_sigreturn, r9; break 13; */
	data[0] = 0x9c5f;
	data[1] = __NR_sigreturn;
	data[2] = 0xe93d;
	/* This is movu.w __NR_rt_sigreturn, r9; break 13; */
	data[3] = 0x9c5f;
	data[4] = __NR_rt_sigreturn;
	data[5] = 0xe93d;

	/* Map to userspace with appropriate permissions (no write access...) */
	cris_signal_return_page = (unsigned long)
          __ioremap_prot(virt_to_phys(data), PAGE_SIZE, PAGE_SIGNAL_TRAMPOLINE);

	return 0;
}

__initcall(cris_init_signal);