/* MN10300 FPU management
 *
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */
#include <asm/uaccess.h>
#include <asm/fpu.h>
#include <asm/elf.h>
#include <asm/exceptions.h>
#include <asm/system.h>

#ifdef CONFIG_LAZY_SAVE_FPU
struct task_struct *fpu_state_owner;
#endif

/*
 * error functions in FPU disabled exception
 */
asmlinkage void fpu_disabled_in_kernel(struct pt_regs *regs)
{
        die_if_no_fixup("An FPU Disabled exception happened in kernel space\n",
                        regs, EXCEP_FPU_DISABLED);
}

/*
 * handle an FPU operational exception
 * - there's a possibility that if the FPU is asynchronous, the signal might
 *   be meant for a process other than the current one
 */
asmlinkage void fpu_exception(struct pt_regs *regs, enum exception_code code)
{
        struct task_struct *tsk = current;
        siginfo_t info;
        u32 fpcr;

        if (!user_mode(regs))
                die_if_no_fixup("An FPU Operation exception happened in"
                                " kernel space\n",
                                regs, code);

        if (!is_using_fpu(tsk))
                die_if_no_fixup("An FPU Operation exception happened,"
                                " but the FPU is not in use",
                                regs, code);

        info.si_signo = SIGFPE;
        info.si_errno = 0;
        info.si_addr = (void *) tsk->thread.uregs->pc;
        info.si_code = FPE_FLTINV;

        unlazy_fpu(tsk);

        fpcr = tsk->thread.fpu_state.fpcr;

        if (fpcr & FPCR_EC_Z)
                info.si_code = FPE_FLTDIV;
        else if (fpcr & FPCR_EC_O)
                info.si_code = FPE_FLTOVF;
        else if (fpcr & FPCR_EC_U)
                info.si_code = FPE_FLTUND;
        else if (fpcr & FPCR_EC_I)
                info.si_code = FPE_FLTRES;

        force_sig_info(SIGFPE, &info, tsk);
}

/*
 * handle an FPU invalid_op exception
 * - Derived from DO_EINFO() macro in arch/mn10300/kernel/traps.c
 */
asmlinkage void fpu_invalid_op(struct pt_regs *regs, enum exception_code code)
{
        siginfo_t info;

        if (!user_mode(regs))
                die_if_no_fixup("FPU invalid opcode", regs, code);

        info.si_signo = SIGILL;
        info.si_errno = 0;
        info.si_code = ILL_COPROC;
        info.si_addr = (void *) regs->pc;
        force_sig_info(info.si_signo, &info, current);
}

/*
 * save the FPU state to a signal context
 */
int fpu_setup_sigcontext(struct fpucontext *fpucontext)
{
        struct task_struct *tsk = current;

        if (!is_using_fpu(tsk))
                return 0;

        /* transfer the current FPU state to memory and cause fpu_init() to be
         * triggered by the next attempted FPU operation by the current
         * process.
         */
        preempt_disable();

#ifndef CONFIG_LAZY_SAVE_FPU
        if (tsk->thread.fpu_flags & THREAD_HAS_FPU) {
                fpu_save(&tsk->thread.fpu_state);
                tsk->thread.uregs->epsw &= ~EPSW_FE;
                tsk->thread.fpu_flags &= ~THREAD_HAS_FPU;
        }
#else /* !CONFIG_LAZY_SAVE_FPU */
        if (fpu_state_owner == tsk) {
                fpu_save(&tsk->thread.fpu_state);
                fpu_state_owner->thread.uregs->epsw &= ~EPSW_FE;
                fpu_state_owner = NULL;
        }
#endif /* !CONFIG_LAZY_SAVE_FPU */

        preempt_enable();

        /* we no longer have a valid current FPU state */
        clear_using_fpu(tsk);

        /* transfer the saved FPU state onto the userspace stack */
        if (copy_to_user(fpucontext,
                         &tsk->thread.fpu_state,
                         min(sizeof(struct fpu_state_struct),
                             sizeof(struct fpucontext))))
                return -1;

        return 1;
}

/*
 * kill a process's FPU state during restoration after signal handling
 */
void fpu_kill_state(struct task_struct *tsk)
{
        /* disown anything left in the FPU */
        preempt_disable();

#ifndef CONFIG_LAZY_SAVE_FPU
        if (tsk->thread.fpu_flags & THREAD_HAS_FPU) {
                tsk->thread.uregs->epsw &= ~EPSW_FE;
                tsk->thread.fpu_flags &= ~THREAD_HAS_FPU;
        }
#else /* !CONFIG_LAZY_SAVE_FPU */
        if (fpu_state_owner == tsk) {
                fpu_state_owner->thread.uregs->epsw &= ~EPSW_FE;
                fpu_state_owner = NULL;
        }
#endif /* !CONFIG_LAZY_SAVE_FPU */

        preempt_enable();

        /* we no longer have a valid current FPU state */
        clear_using_fpu(tsk);
}

/*
 * restore the FPU state from a signal context
 */
int fpu_restore_sigcontext(struct fpucontext *fpucontext)
{
        struct task_struct *tsk = current;
        int ret;

        /* load up the old FPU state */
        ret = copy_from_user(&tsk->thread.fpu_state, fpucontext,
                             min(sizeof(struct fpu_state_struct),
                                 sizeof(struct fpucontext)));
        if (!ret)
                set_using_fpu(tsk);

        return ret;
}

/*
 * fill in the FPU structure for a core dump
 */
int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpreg)
{
        struct task_struct *tsk = current;
        int fpvalid;

        fpvalid = is_using_fpu(tsk);
        if (fpvalid) {
                unlazy_fpu(tsk);
                memcpy(fpreg, &tsk->thread.fpu_state, sizeof(*fpreg));
        }

        return fpvalid;
}