/*
 *  linux/arch/ppc64/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/unistd.h>
#include <linux/stddef.h>
#include <linux/elf.h>
#include <asm/ppc32.h>
#include <asm/sigcontext.h>
#include <asm/ucontext.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/ppcdebug.h>
#include <asm/unistd.h>
#include <asm/cacheflush.h>

#define DEBUG_SIG 0

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

#ifndef MIN
#define MIN(a,b) (((a) < (b)) ? (a) : (b))
#endif

#define GP_REGS_SIZE	MIN(sizeof(elf_gregset_t), sizeof(struct pt_regs))
#define FP_REGS_SIZE	sizeof(elf_fpregset_t)

#define TRAMP_TRACEBACK	3
#define TRAMP_SIZE	6

/*
 * When we have signals to deliver, we set up on the user stack,
 * going down from the original stack pointer:
 *	1) a rt_sigframe struct which contains the ucontext	
 *	2) a gap of __SIGNAL_FRAMESIZE bytes which acts as a dummy caller
 *	   frame for the signal handler.
 */

struct rt_sigframe {
	/* sys_rt_sigreturn requires the ucontext be the first field */
	struct ucontext uc;
	unsigned long _unused[2];
	unsigned int tramp[TRAMP_SIZE];
	struct siginfo *pinfo;
	void *puc;
	struct siginfo info;
	/* 64 bit ABI allows for 288 bytes below sp before decrementing it. */
	char abigap[288];
};


/*
 * Atomically swap in the new signal mask, and wait for a signal.
 */
long 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->gpr[3] = EINTR;
	regs->ccr |= 0x10000000;
	while (1) {
		current->state = TASK_INTERRUPTIBLE;
		schedule();
		if (do_signal(&saveset, regs))
			return regs->gpr[3];
	}
}

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


/*
 * Set up the sigcontext for the signal frame.
 */

static int
setup_sigcontext(struct sigcontext *sc, struct pt_regs *regs,
		 int signr, sigset_t *set, unsigned long handler)
{
	int err = 0;

	if (regs->msr & MSR_FP)
		giveup_fpu(current);

	current->thread.saved_msr = regs->msr & ~(MSR_FP | MSR_FE0 | MSR_FE1);
	regs->msr = current->thread.saved_msr | current->thread.fpexc_mode;
	current->thread.saved_softe = regs->softe;

	err |= __put_user(&sc->gp_regs, &sc->regs);
	err |= __copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE);
	err |= __copy_to_user(&sc->fp_regs, &current->thread.fpr, FP_REGS_SIZE);
	err |= __put_user(signr, &sc->signal);
	err |= __put_user(handler, &sc->handler);
	if (set != NULL)
		err |=  __put_user(set->sig[0], &sc->oldmask);

	regs->msr &= ~(MSR_FP | MSR_FE0 | MSR_FE1);
	current->thread.fpscr = 0;

	return err;
}

/*
 * Restore the sigcontext from the signal frame.
 */

static int
restore_sigcontext(struct pt_regs *regs, sigset_t *set, struct sigcontext *sc)
{
	unsigned int err = 0;

	if (regs->msr & MSR_FP)
		giveup_fpu(current);

	err |= __copy_from_user(regs, &sc->gp_regs, GP_REGS_SIZE);
	err |= __copy_from_user(&current->thread.fpr, &sc->fp_regs, FP_REGS_SIZE);
	current->thread.fpexc_mode = regs->msr & (MSR_FE0 | MSR_FE1);
	if (set != NULL)
		err |=  __get_user(set->sig[0], &sc->oldmask);

	/* Don't allow the signal handler to change these modulo FE{0,1} */
	regs->msr = current->thread.saved_msr & ~(MSR_FP | MSR_FE0 | MSR_FE1);
	regs->softe = current->thread.saved_softe;

	return err;
}

/*
 * Allocate space for the signal frame
 */
static inline void *
get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size)
{
        unsigned long newsp;

        /* Default to using normal stack */
        newsp = regs->gpr[1];

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

        return (void *)((newsp - frame_size) & -8ul);
}

static int
setup_trampoline(unsigned int syscall, unsigned int *tramp)
{
	int i, err = 0;

	/* addi r1, r1, __SIGNAL_FRAMESIZE  # Pop the dummy stackframe */
	err |= __put_user(0x38210000UL | (__SIGNAL_FRAMESIZE & 0xffff), &tramp[0]);
	/* li r0, __NR_[rt_]sigreturn| */
	err |= __put_user(0x38000000UL | (syscall & 0xffff), &tramp[1]);
	/* sc */
	err |= __put_user(0x44000002UL, &tramp[2]);

	/* Minimal traceback info */
	for (i=TRAMP_TRACEBACK; i < TRAMP_SIZE ;i++)
		err |= __put_user(0, &tramp[i]);

	if (!err)
		flush_icache_range((unsigned long) &tramp[0],
			   (unsigned long) &tramp[TRAMP_SIZE]);

	return err;
}

/*
 * 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 *uc = (struct ucontext *)regs->gpr[1];
	sigset_t set;
	stack_t st;

	if (verify_area(VERIFY_READ, uc, sizeof(*uc)))
		goto badframe;

	if (__copy_from_user(&set, &uc->uc_sigmask, sizeof(set)))
		goto badframe;
	sigdelsetmask(&set, ~_BLOCKABLE);
	spin_lock_irq(&current->sighand->siglock);
	current->blocked = set;
	recalc_sigpending();
	spin_unlock_irq(&current->sighand->siglock);

	if (restore_sigcontext(regs, NULL, &uc->uc_mcontext))
		goto badframe;

	if (__copy_from_user(&st, &uc->uc_stack, sizeof(st)))
		goto badframe;
	/* This function sets back the stack flags into
	   the current task structure.  */
	sys_sigaltstack(&st, NULL, 0, 0, 0, 0, regs);

	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
	do_exit(SIGSEGV);
}

static void
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 *funct_desc_ptr;
	struct rt_sigframe *frame;
	unsigned long newsp = 0;
	int err = 0;

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

	if (verify_area(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;

	/* Set up to return from userspace. */
	err |= setup_trampoline(__NR_rt_sigreturn, &frame->tramp[0]);
	if (err)
		goto badframe;

	funct_desc_ptr = (func_descr_t *) ka->sa.sa_handler;

	/* Allocate a dummy caller frame for the signal handler. */
	newsp = (unsigned long)frame - __SIGNAL_FRAMESIZE;
	err |= put_user(0, (unsigned long *)newsp);

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

	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);
}


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

	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;
}

static inline void
syscall_restart(struct pt_regs *regs, struct k_sigaction *ka)
{
	switch ((int)regs->result) {
	case -ERESTART_RESTARTBLOCK:
		current_thread_info()->restart_block.fn = do_no_restart_syscall;
		/* fallthrough */
	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;

	/*
	 * 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, regs, NULL);
	if (signr > 0) {
		struct k_sigaction *ka = &current->sighand->action[signr-1];

		/* Whee!  Actually deliver the signal.  */
		if (regs->trap == 0x0C00)
			syscall_restart(regs, ka);
		handle_signal(signr, ka, &info, oldset, regs);
		return 1;
	}

	if (regs->trap == 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;
}