// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright IBM Corp. 2012
 * Author(s): Jan Glauber <jang@linux.vnet.ibm.com>
 */

#include <linux/kernel.h>
#include <linux/syscalls.h>
#include <linux/signal.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/kernel_stat.h>
#include <linux/sched/task_stack.h>

#include <asm/runtime_instr.h>
#include <asm/cpu_mf.h>
#include <asm/irq.h>

#include "entry.h"

/* empty control block to disable RI by loading it */
struct runtime_instr_cb runtime_instr_empty_cb;

void runtime_instr_release(struct task_struct *tsk)
{
        kfree(tsk->thread.ri_cb);
}

static void disable_runtime_instr(void)
{
        struct task_struct *task = current;
        struct pt_regs *regs;

        if (!task->thread.ri_cb)
                return;
        regs = task_pt_regs(task);
        preempt_disable();
        load_runtime_instr_cb(&runtime_instr_empty_cb);
        kfree(task->thread.ri_cb);
        task->thread.ri_cb = NULL;
        preempt_enable();

        /*
         * Make sure the RI bit is deleted from the PSW. If the user did not
         * switch off RI before the system call the process will get a
         * specification exception otherwise.
         */
        regs->psw.mask &= ~PSW_MASK_RI;
}

static void init_runtime_instr_cb(struct runtime_instr_cb *cb)
{
        cb->rla = 0xfff;
        cb->s = 1;
        cb->k = 1;
        cb->ps = 1;
        cb->pc = 1;
        cb->key = PAGE_DEFAULT_KEY >> 4;
        cb->v = 1;
}

/*
 * The signum argument is unused. In older kernels it was used to
 * specify a real-time signal. For backwards compatibility user space
 * should pass a valid real-time signal number (the signum argument
 * was checked in older kernels).
 */
SYSCALL_DEFINE2(s390_runtime_instr, int, command, int, signum)
{
        struct runtime_instr_cb *cb;

        if (!test_facility(64))
                return -EOPNOTSUPP;

        if (command == S390_RUNTIME_INSTR_STOP) {
                disable_runtime_instr();
                return 0;
        }

        if (command != S390_RUNTIME_INSTR_START)
                return -EINVAL;

        if (!current->thread.ri_cb) {
                cb = kzalloc_obj(*cb);
                if (!cb)
                        return -ENOMEM;
        } else {
                cb = current->thread.ri_cb;
                memset(cb, 0, sizeof(*cb));
        }

        init_runtime_instr_cb(cb);

        /* now load the control block to make it available */
        preempt_disable();
        current->thread.ri_cb = cb;
        load_runtime_instr_cb(cb);
        preempt_enable();
        return 0;
}