fpu.c

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/* MN10300 FPU management
 *
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells ([email protected])
 *
 * 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>

#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);
}

/*
 * 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;
}