signal_64.c

linux-2.6.15.6

/*
 * Handle {get,set,swap}_context operations
 */
int sys_swapcontext(struct ucontext __user *old_ctx,
		    struct ucontext __user *new_ctx,
		    long ctx_size, long r6, long r7, long r8, struct pt_regs *regs)
{
	unsigned char tmp;
	sigset_t set;

	/* Context size is for future use. Right now, we only make sure
	 * we are passed something we understand
	 */
	if (ctx_size < sizeof(struct ucontext))
		return -EINVAL;

	if (old_ctx != NULL) {
		if (!access_ok(VERIFY_WRITE, old_ctx, sizeof(*old_ctx))
		    || setup_sigcontext(&old_ctx->uc_mcontext, regs, 0, NULL, 0)
		    || __copy_to_user(&old_ctx->uc_sigmask,
				      &current->blocked, sizeof(sigset_t)))
			return -EFAULT;
	}
	if (new_ctx == NULL)
		return 0;
	if (!access_ok(VERIFY_READ, new_ctx, sizeof(*new_ctx))
	    || __get_user(tmp, (u8 __user *) new_ctx)
	    || __get_user(tmp, (u8 __user *) (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 access_ok
	 * 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 (__copy_from_user(&set, &new_ctx->uc_sigmask, sizeof(set)))
		do_exit(SIGSEGV);
	restore_sigmask(&set);
	if (restore_sigcontext(regs, NULL, 0, &new_ctx->uc_mcontext))
		do_exit(SIGSEGV);

	/* This returns like rt_sigreturn */
	return 0;
}


/*
 * Do a signal return; undo the signal stack.
 */

int sys_rt_sigreturn(unsigned long r3, unsigned long r4, unsigned long r5,
		     unsigned long r6, unsigned long r7, unsigned long r8,
		     struct pt_regs *regs)
{
	struct ucontext __user *uc = (struct ucontext __user *)regs->gpr[1];
	sigset_t set;

	/* Always make any pending restarted system calls return -EINTR */
	current_thread_info()->restart_block.fn = do_no_restart_syscall;

	if (!access_ok(VERIFY_READ, uc, sizeof(*uc)))
		goto badframe;

	if (__copy_from_user(&set, &uc->uc_sigmask, sizeof(set)))
		goto badframe;
	restore_sigmask(&set);
	if (restore_sigcontext(regs, NULL, 1, &uc->uc_mcontext))
		goto badframe;

	/* do_sigaltstack expects a __user pointer and won't modify
	 * what's in there anyway
	 */
	do_sigaltstack(&uc->uc_stack, NULL, regs->gpr[1]);

	return regs->result;

badframe:
#if DEBUG_SIG
	printk("badframe in sys_rt_sigreturn, regs=%p uc=%p &uc->uc_mcontext=%p\n",
	       regs, uc, &uc->uc_mcontext);
#endif
	force_sig(SIGSEGV, current);
	return 0;
}

static int setup_rt_frame(int signr, struct k_sigaction *ka, siginfo_t *info,
		sigset_t *set, struct pt_regs *regs)
{
	/* Handler is *really* a pointer to the function descriptor for
	 * the signal routine.  The first entry in the function
	 * descriptor is the entry address of signal and the second
	 * entry is the TOC value we need to use.
	 */
	func_descr_t __user *funct_desc_ptr;
	struct rt_sigframe __user *frame;
	unsigned long newsp = 0;
	long err = 0;

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

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

	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 badframe;

	/* Create the ucontext.  */
	err |= __put_user(0, &frame->uc.uc_flags);
	err |= __put_user(0, &frame->uc.uc_link);
	err |= __put_user(current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
	err |= __put_user(sas_ss_flags(regs->gpr[1]),
			  &frame->uc.uc_stack.ss_flags);
	err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
	err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, signr, NULL,
				(unsigned long)ka->sa.sa_handler);
	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
	if (err)
		goto badframe;

	/* Make sure signal handler doesn't get spurious FP exceptions */
	current->thread.fpscr.val = 0;

	/* Set up to return from userspace. */
	if (vdso64_rt_sigtramp && current->thread.vdso_base) {
		regs->link = current->thread.vdso_base + vdso64_rt_sigtramp;
	} else {
		err |= setup_trampoline(__NR_rt_sigreturn, &frame->tramp[0]);
		if (err)
			goto badframe;
		regs->link = (unsigned long) &frame->tramp[0];
	}
	funct_desc_ptr = (func_descr_t __user *) ka->sa.sa_handler;

	/* Allocate a dummy caller frame for the signal handler. */
	newsp = (unsigned long)frame - __SIGNAL_FRAMESIZE;
	err |= put_user(regs->gpr[1], (unsigned long __user *)newsp);

	/* Set up "regs" so we "return" to the signal handler. */
	err |= get_user(regs->nip, &funct_desc_ptr->entry);
	regs->gpr[1] = newsp;
	err |= get_user(regs->gpr[2], &funct_desc_ptr->toc);
	regs->gpr[3] = signr;
	regs->result = 0;
	if (ka->sa.sa_flags & SA_SIGINFO) {
		err |= get_user(regs->gpr[4], (unsigned long __user *)&frame->pinfo);
		err |= get_user(regs->gpr[5], (unsigned long __user *)&frame->puc);
		regs->gpr[6] = (unsigned long) frame;
	} else {
		regs->gpr[4] = (unsigned long)&frame->uc.uc_mcontext;
	}
	if (err)
		goto badframe;

	if (test_thread_flag(TIF_SINGLESTEP))
		ptrace_notify(SIGTRAP);

	return 1;

badframe:
#if DEBUG_SIG
	printk("badframe in setup_rt_frame, regs=%p frame=%p newsp=%lx\n",
	       regs, frame, newsp);
#endif
	force_sigsegv(signr, current);
	return 0;
}


/*
 * OK, we're invoking a handler
 */
static int handle_signal(unsigned long sig, struct k_sigaction *ka,
			 siginfo_t *info, sigset_t *oldset, struct pt_regs *regs)
{
	int ret;

	/* Set up Signal Frame */
	ret = setup_rt_frame(sig, ka, info, oldset, regs);

	if (ret) {
		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 ret;
}

static inline void syscall_restart(struct pt_regs *regs, struct k_sigaction *ka)
{
	switch ((int)regs->result) {
	case -ERESTART_RESTARTBLOCK:
	case -ERESTARTNOHAND:
		/* ERESTARTNOHAND means that the syscall should only be
		 * restarted if there was no handler for the signal, and since
		 * we only get here if there is a handler, we dont restart.
		 */
		regs->result = -EINTR;
		break;
	case -ERESTARTSYS:
		/* ERESTARTSYS means to restart the syscall if there is no
		 * handler or the handler was registered with SA_RESTART
		 */
		if (!(ka->sa.sa_flags & SA_RESTART)) {
			regs->result = -EINTR;
			break;
		}
		/* fallthrough */
	case -ERESTARTNOINTR:
		/* ERESTARTNOINTR means that the syscall should be
		 * called again after the signal handler returns.
		 */
		regs->gpr[3] = regs->orig_gpr3;
		regs->nip -= 4;
		regs->result = 0;
		break;
	}
}

/*
 * 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;
	int signr;
	struct k_sigaction ka;

	/*
	 * If the current thread is 32 bit - invoke the
	 * 32 bit signal handling code
	 */
	if (test_thread_flag(TIF_32BIT))
		return do_signal32(oldset, regs);

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

	signr = get_signal_to_deliver(&info, &ka, regs, NULL);
	if (signr > 0) {
		/* Whee!  Actually deliver the signal.  */
		if (TRAP(regs) == 0x0C00)
			syscall_restart(regs, &ka);

		/*
		 * Reenable the DABR before delivering the signal to
		 * user space. The DABR will have been cleared if it
		 * triggered inside the kernel.
		 */
		if (current->thread.dabr)
			set_dabr(current->thread.dabr);

		return handle_signal(signr, &ka, &info, oldset, regs);
	}

	if (TRAP(regs) == 0x0C00) {	/* System Call! */
		if ((int)regs->result == -ERESTARTNOHAND ||
		    (int)regs->result == -ERESTARTSYS ||
		    (int)regs->result == -ERESTARTNOINTR) {
			regs->gpr[3] = regs->orig_gpr3;
			regs->nip -= 4; /* Back up & retry system call */
			regs->result = 0;
		} else if ((int)regs->result == -ERESTART_RESTARTBLOCK) {
			regs->gpr[0] = __NR_restart_syscall;
			regs->nip -= 4;
			regs->result = 0;
		}
	}

	return 0;
}
EXPORT_SYMBOL(do_signal);