fpsimd.c

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/*
 * FP/SIMD context switching and fault handling
 *
 * Copyright (C) 2012 ARM Ltd.
 * Author: Catalin Marinas <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/signal.h>

#include <asm/fpsimd.h>
#include <asm/cputype.h>

#define FPEXC_IOF   (1 << 0)
#define FPEXC_DZF   (1 << 1)
#define FPEXC_OFF   (1 << 2)
#define FPEXC_UFF   (1 << 3)
#define FPEXC_IXF   (1 << 4)
#define FPEXC_IDF   (1 << 7)

/*
 * Trapped FP/ASIMD access.
 */
void do_fpsimd_acc(unsigned int esr, struct pt_regs *regs)
{
    /* TODO: implement lazy context saving/restoring */
    WARN_ON(1);
}

/*
 * Raise a SIGFPE for the current process.
 */
void do_fpsimd_exc(unsigned int esr, struct pt_regs *regs)
{
    siginfo_t info;
    unsigned int si_code = 0;

    if (esr & FPEXC_IOF)
        si_code = FPE_FLTINV;
    else if (esr & FPEXC_DZF)
        si_code = FPE_FLTDIV;
    else if (esr & FPEXC_OFF)
        si_code = FPE_FLTOVF;
    else if (esr & FPEXC_UFF)
        si_code = FPE_FLTUND;
    else if (esr & FPEXC_IXF)
        si_code = FPE_FLTRES;

    memset(&info, 0, sizeof(info));
    info.si_signo = SIGFPE;
    info.si_code = si_code;
    info.si_addr = (void __user *)instruction_pointer(regs);

    send_sig_info(SIGFPE, &info, current);
}

void fpsimd_thread_switch(struct task_struct *next)
{
    /* check if not kernel threads */
    if (current->mm)
        fpsimd_save_state(&current->thread.fpsimd_state);
    if (next->mm)
        fpsimd_load_state(&next->thread.fpsimd_state);
}

void fpsimd_flush_thread(void)
{
    memset(&current->thread.fpsimd_state, 0, sizeof(struct fpsimd_state));
    fpsimd_load_state(&current->thread.fpsimd_state);
}

/*
 * FP/SIMD support code initialisation.
 */
static int __init fpsimd_init(void)
{
    u64 pfr = read_cpuid(ID_AA64PFR0_EL1);

    if (pfr & (0xf << 16)) {
        pr_notice("Floating-point is not implemented\n");
        return 0;
    }
    elf_hwcap |= HWCAP_FP;

    if (pfr & (0xf << 20))
        pr_notice("Advanced SIMD is not implemented\n");
    else
        elf_hwcap |= HWCAP_ASIMD;

    return 0;
}
late_initcall(fpsimd_init);