/*
 *  arch/ppc/kernel/signal.c
 *
 *  PowerPC version 
 *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
 *
 *  Derived from "arch/i386/kernel/signal.c"
 *    Copyright (C) 1991, 1992 Linus Torvalds
 *    1997-11-28  Modified for POSIX.1b signals by Richard Henderson
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version
 *  2 of the License, or (at your option) any later version.
 */

#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/errno.h>
#include <linux/wait.h>
#include <linux/ptrace.h>
#include <linux/unistd.h>
#include <linux/stddef.h>
#include <linux/elf.h>
#include <linux/tty.h>
#include <linux/binfmts.h>
#include <asm/ucontext.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/cacheflush.h>

#define DEBUG_SIG 0

#define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))

extern void sigreturn_exit(struct pt_regs *);

#define GP_REGS_SIZE	min(sizeof(elf_gregset_t), sizeof(struct pt_regs))

/* 
 * These are the flags in the MSR that the user is allowed to change
 * by modifying the saved value of the MSR on the stack.  SE and BE
 * should not be in this list since gdb may want to change these.  I.e,
 * you should be able to step out of a signal handler to see what
 * instruction executes next after the signal handler completes.
 * Alternately, if you stepped into a signal handler, you should be
 * able to continue 'til the next breakpoint from within the signal
 * handler, even if the handler returns.
 */
#define MSR_USERCHANGE	(MSR_FE0 | MSR_FE1)

int do_signal(sigset_t *oldset, struct pt_regs *regs);

/*
 * Atomically swap in the new signal mask, and wait for a signal.
 */
int
sys_sigsuspend(old_sigset_t mask, int p2, int p3, int p4, int p6, int p7,
	       struct pt_regs *regs)
{
	sigset_t saveset;

	mask &= _BLOCKABLE;
	spin_lock_irq(&current->sighand->siglock);
	saveset = current->blocked;
	siginitset(&current->blocked, mask);
	recalc_sigpending();
	spin_unlock_irq(&current->sighand->siglock);

	regs->result = -EINTR;
	regs->ccr |= 0x10000000;
	regs->gpr[3] = EINTR;
	while (1) {
		current->state = TASK_INTERRUPTIBLE;
		schedule();
		if (do_signal(&saveset, regs))
			sigreturn_exit(regs);
	}
}

int
sys_rt_sigsuspend(sigset_t *unewset, size_t sigsetsize, int p3, int p4, int p6,
		  int p7, struct pt_regs *regs)
{
	sigset_t saveset, newset;

	/* XXX: Don't preclude handling different sized sigset_t's.  */
	if (sigsetsize != sizeof(sigset_t))
		return -EINVAL;

	if (copy_from_user(&newset, unewset, sizeof(newset)))
		return -EFAULT;
	sigdelsetmask(&newset, ~_BLOCKABLE);

	spin_lock_irq(&current->sighand->siglock);
	saveset = current->blocked;
	current->blocked = newset;
	recalc_sigpending();
	spin_unlock_irq(&current->sighand->siglock);

	regs->result = -EINTR;
	regs->ccr |= 0x10000000;
	regs->gpr[3] = EINTR;
	while (1) {
		current->state = TASK_INTERRUPTIBLE;
		schedule();
		if (do_signal(&saveset, regs))
			sigreturn_exit(regs);
	}
}


int
sys_sigaltstack(const stack_t *uss, stack_t *uoss, int r5, int r6,
		int r7, int r8, struct pt_regs *regs)
{
	return do_sigaltstack(uss, uoss, regs->gpr[1]);
}

int 
sys_sigaction(int sig, const struct old_sigaction *act,
	      struct old_sigaction *oact)
{
	struct k_sigaction new_ka, old_ka;
	int ret;

	if (act) {
		old_sigset_t mask;
		if (verify_area(VERIFY_READ, act, sizeof(*act)) ||
		    __get_user(new_ka.sa.sa_handler, &act->sa_handler) ||
		    __get_user(new_ka.sa.sa_restorer, &act->sa_restorer))
			return -EFAULT;
		__get_user(new_ka.sa.sa_flags, &act->sa_flags);
		__get_user(mask, &act->sa_mask);
		siginitset(&new_ka.sa.sa_mask, mask);
	}

	ret = do_sigaction(sig, (act? &new_ka: NULL), (oact? &old_ka: NULL));

	if (!ret && oact) {
		if (verify_area(VERIFY_WRITE, oact, sizeof(*oact)) ||
		    __put_user(old_ka.sa.sa_handler, &oact->sa_handler) ||
		    __put_user(old_ka.sa.sa_restorer, &oact->sa_restorer))
			return -EFAULT;
		__put_user(old_ka.sa.sa_flags, &oact->sa_flags);
		__put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask);
	}

	return ret;
}

/*
 * When we have signals to deliver, we set up on the
 * user stack, going down from the original stack pointer:
 *	a sigregs struct
 *	a sigcontext struct
 *	a gap of __SIGNAL_FRAMESIZE bytes
 *
 * Each of these things must be a multiple of 16 bytes in size.
 *
 */
struct sigregs {
	elf_gregset_t	gp_regs;
	double		fp_regs[ELF_NFPREG];
	unsigned long	tramp[2];
	/* Programs using the rs6000/xcoff abi can save up to 19 gp regs
	   and 18 fp regs below sp before decrementing it. */
	int		abigap[56];
};

struct rt_sigframe
{
	unsigned long	_unused[2];
	struct siginfo *pinfo;
	void *puc;
	struct siginfo info;
	struct ucontext uc;
};


/*
 *  When we have rt signals to deliver, we set up on the
 *  user stack, going down from the original stack pointer:
 *	   a sigregs struct
 *	   one rt_sigframe struct (siginfo + ucontext)
 *	   a gap of __SIGNAL_FRAMESIZE bytes
 *
 *  Each of these things must be a multiple of 16 bytes in size.
 *
 */
int sys_rt_sigreturn(int r3, int r4, int r5, int r6, int r7, int r8,
		     struct pt_regs *regs)
{
	struct rt_sigframe *rt_sf;
	struct sigcontext sigctx;
	struct sigregs *sr;
	elf_gregset_t saved_regs;  /* an array of ELF_NGREG unsigned longs */
	sigset_t set;
	stack_t st;

	rt_sf = (struct rt_sigframe *)(regs->gpr[1] + __SIGNAL_FRAMESIZE);
	if (copy_from_user(&sigctx, &rt_sf->uc.uc_mcontext, sizeof(sigctx))
	    || copy_from_user(&set, &rt_sf->uc.uc_sigmask, sizeof(set))
	    || copy_from_user(&st, &rt_sf->uc.uc_stack, sizeof(st)))
		goto badframe;
	sigdelsetmask(&set, ~_BLOCKABLE);
	spin_lock_irq(&current->sighand->siglock);
	current->blocked = set;
	recalc_sigpending();
	spin_unlock_irq(&current->sighand->siglock);
	if (regs->msr & MSR_FP)
		giveup_fpu(current);

	/* restore registers -
	 * sigctx is initialized to point to the 
	 * preamble frame (where registers are stored) 
	 * see handle_signal()
	 */
	sr = (struct sigregs *) sigctx.regs;
	if (copy_from_user(saved_regs, &sr->gp_regs, sizeof(sr->gp_regs)))
		goto badframe;
	saved_regs[PT_MSR] = (regs->msr & ~MSR_USERCHANGE)
		| (saved_regs[PT_MSR] & MSR_USERCHANGE);
	memcpy(regs, saved_regs, GP_REGS_SIZE);
	if (copy_from_user(current->thread.fpr, &sr->fp_regs,
			   sizeof(sr->fp_regs)))
		goto badframe;
	/* This function sets back the stack flags into
	   the current task structure.  */
	sys_sigaltstack(&st, NULL, 0, 0, 0, 0, regs);

	sigreturn_exit(regs);		/* doesn't return here */
	return 0;

badframe:
	do_exit(SIGSEGV);
}

static void
setup_rt_frame(struct pt_regs *regs, struct sigregs *frame,
	       signed long newsp)
{
	struct rt_sigframe *rt_sf = (struct rt_sigframe *) newsp;

	/* Set up preamble frame */
	if (verify_area(VERIFY_WRITE, frame, sizeof(*frame)))
		goto badframe;
	CHECK_FULL_REGS(regs);
	if (regs->msr & MSR_FP)
		giveup_fpu(current);
	if (__copy_to_user(&frame->gp_regs, regs, GP_REGS_SIZE)
	    || __copy_to_user(&frame->fp_regs, current->thread.fpr,
			      ELF_NFPREG * sizeof(double))
	/* Set up to return from user space.
	   It calls the sc exception at offset 0x9999 
	   for sys_rt_sigreturn().
	*/
	    || __put_user(0x38000000UL + __NR_rt_sigreturn, &frame->tramp[0])
	    || __put_user(0x44000002UL, &frame->tramp[1]))	/* sc */
		goto badframe;
	flush_icache_range((unsigned long) &frame->tramp[0],
			   (unsigned long) &frame->tramp[2]);
	current->thread.fpscr = 0;	/* turn off all fp exceptions */

	/* Retrieve rt_sigframe from stack and
	   set up registers for signal handler
	*/
	newsp -= __SIGNAL_FRAMESIZE;
	if (put_user(regs->gpr[1], (unsigned long *)newsp)
	    || get_user(regs->nip, &rt_sf->uc.uc_mcontext.handler)
	    || get_user(regs->gpr[3], &rt_sf->uc.uc_mcontext.signal)
	    || get_user(regs->gpr[4], (unsigned long *)&rt_sf->pinfo)
	    || get_user(regs->gpr[5], (unsigned long *)&rt_sf->puc))
		goto badframe;

	regs->gpr[1] = newsp;
	regs->gpr[6] = (unsigned long) rt_sf;
	regs->link = (unsigned long) frame->tramp;

	return;

badframe:
#if DEBUG_SIG
	printk("badframe in setup_rt_frame, regs=%p frame=%p newsp=%lx\n",
	       regs, frame, newsp);
#endif
	do_exit(SIGSEGV);
}

/*
 * Do a signal return; undo the signal stack.
 */
int sys_sigreturn(int r3, int r4, int r5, int r6, int r7, int r8,
		  struct pt_regs *regs)
{
	struct sigcontext *sc, sigctx;
	struct sigregs *sr;
	elf_gregset_t saved_regs;  /* an array of ELF_NGREG unsigned longs */
	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;
#if _NSIG_WORDS > 1
	set.sig[1] = sigctx._unused[3];
#endif
	sigdelsetmask(&set, ~_BLOCKABLE);
	spin_lock_irq(&current->sighand->siglock);
	current->blocked = set;
	recalc_sigpending();
	spin_unlock_irq(&current->sighand->siglock);
	if (regs->msr & MSR_FP )
		giveup_fpu(current);

	/* restore registers */
	sr = (struct sigregs *) sigctx.regs;
	if (copy_from_user(saved_regs, &sr->gp_regs, sizeof(sr->gp_regs)))
		goto badframe;
	saved_regs[PT_MSR] = (regs->msr & ~MSR_USERCHANGE)
		| (saved_regs[PT_MSR] & MSR_USERCHANGE);
	memcpy(regs, saved_regs, GP_REGS_SIZE);

	if (copy_from_user(current->thread.fpr, &sr->fp_regs,
			   sizeof(sr->fp_regs)))
		goto badframe;

	sigreturn_exit(regs);		/* doesn't return here */
	return 0;

badframe:
	do_exit(SIGSEGV);
}	

/*
 * Set up a signal frame.
 */
static void
setup_frame(struct pt_regs *regs, struct sigregs *frame,
	    unsigned long newsp)
{
	struct sigcontext *sc = (struct sigcontext *) newsp;

	if (verify_area(VERIFY_WRITE, frame, sizeof(*frame)))
		goto badframe;
	CHECK_FULL_REGS(regs);
	if (regs->msr & MSR_FP)
		giveup_fpu(current);
	if (__copy_to_user(&frame->gp_regs, regs, GP_REGS_SIZE)
	    || __copy_to_user(&frame->fp_regs, current->thread.fpr,
			      ELF_NFPREG * sizeof(double))
	    || __put_user(0x38000000UL + __NR_sigreturn, &frame->tramp[0])
	    || __put_user(0x44000002UL, &frame->tramp[1]))   /* sc */
		goto badframe;
	flush_icache_range((unsigned long) &frame->tramp[0],
			   (unsigned long) &frame->tramp[2]);
	current->thread.fpscr = 0;	/* turn off all fp exceptions */

	newsp -= __SIGNAL_FRAMESIZE;
	if (put_user(regs->gpr[1], (unsigned long *)newsp)
	    || get_user(regs->nip, &sc->handler)
	    || get_user(regs->gpr[3], &sc->signal))
		goto badframe;
	regs->gpr[1] = newsp;
	regs->gpr[4] = (unsigned long) sc;
	regs->link = (unsigned long) frame->tramp;

	return;

badframe:
#if DEBUG_SIG
	printk("badframe in setup_frame, regs=%p frame=%p newsp=%lx\n",
	       regs, frame, newsp);
#endif
	do_exit(SIGSEGV);
}

/*
 * OK, we're invoking a handler
 */
static void
handle_signal(unsigned long sig, siginfo_t *info, sigset_t *oldset,
	struct pt_regs * regs, unsigned long *newspp, unsigned long frame)
{
	struct sigcontext *sc;
	struct rt_sigframe *rt_sf;
	struct k_sigaction *ka = &current->sighand->action[sig-1];

	if (TRAP(regs) == 0x0C00 /* System Call! */
	    && ((int)regs->result == -ERESTARTNOHAND ||
		(int)regs->result == -ERESTART_RESTARTBLOCK ||
		((int)regs->result == -ERESTARTSYS &&
		 !(ka->sa.sa_flags & SA_RESTART)))) {
		if ((int)regs->result == -ERESTART_RESTARTBLOCK)
			current_thread_info()->restart_block.fn
				= do_no_restart_syscall;
		regs->result = -EINTR;
		regs->gpr[3] = EINTR;
		regs->ccr |= 0x10000000;
	}

	/* Set up Signal Frame */
	if (ka->sa.sa_flags & SA_SIGINFO) {
		/* Put a Real Time Context onto stack */
		*newspp -= sizeof(*rt_sf);
		rt_sf = (struct rt_sigframe *) *newspp;
		if (verify_area(VERIFY_WRITE, rt_sf, sizeof(*rt_sf)))
			goto badframe;

		if (__put_user((unsigned long) ka->sa.sa_handler, &rt_sf->uc.uc_mcontext.handler)
		    || __put_user(&rt_sf->info, &rt_sf->pinfo)
		    || __put_user(&rt_sf->uc, &rt_sf->puc)
		    /* Put the siginfo */
		    || copy_siginfo_to_user(&rt_sf->info, info)
		    /* Create the ucontext */
		    || __put_user(0, &rt_sf->uc.uc_flags)
		    || __put_user(0, &rt_sf->uc.uc_link)
		    || __put_user(current->sas_ss_sp, &rt_sf->uc.uc_stack.ss_sp)
		    || __put_user(sas_ss_flags(regs->gpr[1]), 
				  &rt_sf->uc.uc_stack.ss_flags)
		    || __put_user(current->sas_ss_size, &rt_sf->uc.uc_stack.ss_size)
		    || __copy_to_user(&rt_sf->uc.uc_sigmask, oldset, sizeof(*oldset))
		    /* mcontext.regs points to preamble register frame */
		    || __put_user((struct pt_regs *)frame, &rt_sf->uc.uc_mcontext.regs)
		    || __put_user(sig, &rt_sf->uc.uc_mcontext.signal))
			goto badframe;
	} else {
		/* Put a sigcontext on the stack */
		*newspp -= sizeof(*sc);
		sc = (struct sigcontext *) *newspp;
		if (verify_area(VERIFY_WRITE, sc, sizeof(*sc)))
			goto badframe;
		
		if (__put_user((unsigned long) ka->sa.sa_handler, &sc->handler)
		    || __put_user(oldset->sig[0], &sc->oldmask)
#if _NSIG_WORDS > 1
		    || __put_user(oldset->sig[1], &sc->_unused[3])
#endif
		    || __put_user((struct pt_regs *)frame, &sc->regs)
		    || __put_user(sig, &sc->signal))
			goto badframe;
	}

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

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

badframe:
#if DEBUG_SIG
	printk("badframe in handle_signal, regs=%p frame=%lx newsp=%lx\n",
	       regs, frame, *newspp);
	printk("sc=%p sig=%d ka=%p info=%p oldset=%p\n", sc, sig, ka, info, oldset);
#endif
	do_exit(SIGSEGV);
}

/*
 * 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, NULL);
	if (signr > 0) {
		ka = &current->sighand->action[signr-1];
		if ( (ka->sa.sa_flags & SA_ONSTACK)
		     && (! on_sig_stack(regs->gpr[1])))
			newsp = (current->sas_ss_sp + current->sas_ss_size);
		else
			newsp = regs->gpr[1];
		newsp = frame = newsp - sizeof(struct sigregs);

		/* Whee!  Actually deliver the signal.  */
		handle_signal(signr, &info, oldset, regs, &newsp, frame);
	}

	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;
		}
	}

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

	if (ka->sa.sa_flags & SA_SIGINFO)
		setup_rt_frame(regs, (struct sigregs *) frame, newsp);
	else
		setup_frame(regs, (struct sigregs *) frame, newsp);
	return 1;
}

