linux/arch/arm64/kernel/fpsimd.c

/*
 * FP/SIMD context switching and fault handling
 *
 * Copyright (C) 2012 ARM Ltd.
 * Author: Catalin Marinas <catalin.marinas@arm.com>
 *
 * 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 <linux/hardirq.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);
}

#ifdef CONFIG_KERNEL_MODE_NEON

/*
 * Kernel-side NEON support functions
 */
void kernel_neon_begin(void)
{
	/* Avoid using the NEON in interrupt context */
	BUG_ON(in_interrupt());
	preempt_disable();

	if (current->mm)
		fpsimd_save_state(&current->thread.fpsimd_state);
}
EXPORT_SYMBOL(kernel_neon_begin);

void kernel_neon_end(void)
{
	if (current->mm)
		fpsimd_load_state(&current->thread.fpsimd_state);

	preempt_enable();
}
EXPORT_SYMBOL(kernel_neon_end);

#endif /* CONFIG_KERNEL_MODE_NEON */

/*
 * 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);