// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright IBM Corp. 2016
 * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
 */

#include <linux/cpufeature.h>
#include <linux/kernel.h>
#include <linux/syscalls.h>
#include <linux/signal.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <asm/guarded_storage.h>
#include "entry.h"

void guarded_storage_release(struct task_struct *tsk)
{
        kfree(tsk->thread.gs_cb);
        kfree(tsk->thread.gs_bc_cb);
}

static int gs_enable(void)
{
        struct gs_cb *gs_cb;

        if (!current->thread.gs_cb) {
                gs_cb = kzalloc_obj(*gs_cb);
                if (!gs_cb)
                        return -ENOMEM;
                gs_cb->gsd = 25;
                preempt_disable();
                local_ctl_set_bit(2, CR2_GUARDED_STORAGE_BIT);
                load_gs_cb(gs_cb);
                current->thread.gs_cb = gs_cb;
                preempt_enable();
        }
        return 0;
}

static int gs_disable(void)
{
        if (current->thread.gs_cb) {
                preempt_disable();
                kfree(current->thread.gs_cb);
                current->thread.gs_cb = NULL;
                local_ctl_clear_bit(2, CR2_GUARDED_STORAGE_BIT);
                preempt_enable();
        }
        return 0;
}

static int gs_set_bc_cb(struct gs_cb __user *u_gs_cb)
{
        struct gs_cb *gs_cb;

        gs_cb = current->thread.gs_bc_cb;
        if (!gs_cb) {
                gs_cb = kzalloc_obj(*gs_cb);
                if (!gs_cb)
                        return -ENOMEM;
                current->thread.gs_bc_cb = gs_cb;
        }
        if (copy_from_user(gs_cb, u_gs_cb, sizeof(*gs_cb)))
                return -EFAULT;
        return 0;
}

static int gs_clear_bc_cb(void)
{
        struct gs_cb *gs_cb;

        gs_cb = current->thread.gs_bc_cb;
        current->thread.gs_bc_cb = NULL;
        kfree(gs_cb);
        return 0;
}

void gs_load_bc_cb(struct pt_regs *regs)
{
        struct gs_cb *gs_cb;

        preempt_disable();
        clear_thread_flag(TIF_GUARDED_STORAGE);
        gs_cb = current->thread.gs_bc_cb;
        if (gs_cb) {
                kfree(current->thread.gs_cb);
                current->thread.gs_bc_cb = NULL;
                local_ctl_set_bit(2, CR2_GUARDED_STORAGE_BIT);
                load_gs_cb(gs_cb);
                current->thread.gs_cb = gs_cb;
        }
        preempt_enable();
}

static int gs_broadcast(void)
{
        struct task_struct *sibling;

        read_lock(&tasklist_lock);
        for_each_thread(current, sibling) {
                if (!sibling->thread.gs_bc_cb)
                        continue;
                if (test_and_set_tsk_thread_flag(sibling, TIF_GUARDED_STORAGE))
                        kick_process(sibling);
        }
        read_unlock(&tasklist_lock);
        return 0;
}

SYSCALL_DEFINE2(s390_guarded_storage, int, command,
                struct gs_cb __user *, gs_cb)
{
        if (!cpu_has_gs())
                return -EOPNOTSUPP;
        switch (command) {
        case GS_ENABLE:
                return gs_enable();
        case GS_DISABLE:
                return gs_disable();
        case GS_SET_BC_CB:
                return gs_set_bc_cb(gs_cb);
        case GS_CLEAR_BC_CB:
                return gs_clear_bc_cb();
        case GS_BROADCAST:
                return gs_broadcast();
        default:
                return -EINVAL;
        }
}