// SPDX-License-Identifier: GPL-2.0
/*
 * Privileged ADI driver for sparc64
 *
 * Author: Tom Hromatka <tom.hromatka@oracle.com>
 */
#include <linux/kernel.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/proc_fs.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <asm/asi.h>

#define MAX_BUF_SZ      PAGE_SIZE

static int read_mcd_tag(unsigned long addr)
{
        long err;
        int ver;

        __asm__ __volatile__(
                "1:     ldxa [%[addr]] %[asi], %[ver]\n"
                "       mov 0, %[err]\n"
                "2:\n"
                "       .section .fixup,#alloc,#execinstr\n"
                "       .align 4\n"
                "3:     sethi %%hi(2b), %%g1\n"
                "       jmpl  %%g1 + %%lo(2b), %%g0\n"
                "       mov %[invalid], %[err]\n"
                "       .previous\n"
                "       .section __ex_table, \"a\"\n"
                "       .align 4\n"
                "       .word  1b, 3b\n"
                "       .previous\n"
                : [ver] "=r" (ver), [err] "=r" (err)
                : [addr] "r"  (addr), [invalid] "i" (EFAULT),
                  [asi] "i" (ASI_MCD_REAL)
                : "memory", "g1"
                );

        if (err)
                return -EFAULT;
        else
                return ver;
}

static ssize_t adi_read(struct file *file, char __user *buf,
                        size_t count, loff_t *offp)
{
        size_t ver_buf_sz, bytes_read = 0;
        int ver_buf_idx = 0;
        loff_t offset;
        u8 *ver_buf;
        ssize_t ret;

        ver_buf_sz = min_t(size_t, count, MAX_BUF_SZ);
        ver_buf = kmalloc(ver_buf_sz, GFP_KERNEL);
        if (!ver_buf)
                return -ENOMEM;

        offset = (*offp) * adi_blksize();

        while (bytes_read < count) {
                ret = read_mcd_tag(offset);
                if (ret < 0)
                        goto out;

                ver_buf[ver_buf_idx] = (u8)ret;
                ver_buf_idx++;
                offset += adi_blksize();

                if (ver_buf_idx >= ver_buf_sz) {
                        if (copy_to_user(buf + bytes_read, ver_buf,
                                         ver_buf_sz)) {
                                ret = -EFAULT;
                                goto out;
                        }

                        bytes_read += ver_buf_sz;
                        ver_buf_idx = 0;

                        ver_buf_sz = min_t(size_t, count - bytes_read,
                                           MAX_BUF_SZ);
                }
        }

        (*offp) += bytes_read;
        ret = bytes_read;
out:
        kfree(ver_buf);
        return ret;
}

static int set_mcd_tag(unsigned long addr, u8 ver)
{
        long err;

        __asm__ __volatile__(
                "1:     stxa %[ver], [%[addr]] %[asi]\n"
                "       mov 0, %[err]\n"
                "2:\n"
                "       .section .fixup,#alloc,#execinstr\n"
                "       .align 4\n"
                "3:     sethi %%hi(2b), %%g1\n"
                "       jmpl %%g1 + %%lo(2b), %%g0\n"
                "       mov %[invalid], %[err]\n"
                "       .previous\n"
                "       .section __ex_table, \"a\"\n"
                "       .align 4\n"
                "       .word 1b, 3b\n"
                "       .previous\n"
                : [err] "=r" (err)
                : [ver] "r" (ver), [addr] "r"  (addr),
                  [invalid] "i" (EFAULT), [asi] "i" (ASI_MCD_REAL)
                : "memory", "g1"
                );

        if (err)
                return -EFAULT;
        else
                return ver;
}

static ssize_t adi_write(struct file *file, const char __user *buf,
                         size_t count, loff_t *offp)
{
        size_t ver_buf_sz, bytes_written = 0;
        loff_t offset;
        u8 *ver_buf;
        ssize_t ret;
        int i;

        if (count == 0)
                return -EINVAL;

        ver_buf_sz = min_t(size_t, count, MAX_BUF_SZ);
        ver_buf = kmalloc(ver_buf_sz, GFP_KERNEL);
        if (!ver_buf)
                return -ENOMEM;

        offset = (*offp) * adi_blksize();

        do {
                if (copy_from_user(ver_buf, &buf[bytes_written],
                                   ver_buf_sz)) {
                        ret = -EFAULT;
                        goto out;
                }

                for (i = 0; i < ver_buf_sz; i++) {
                        ret = set_mcd_tag(offset, ver_buf[i]);
                        if (ret < 0)
                                goto out;

                        offset += adi_blksize();
                }

                bytes_written += ver_buf_sz;
                ver_buf_sz = min_t(size_t, count - bytes_written, MAX_BUF_SZ);
        } while (bytes_written < count);

        (*offp) += bytes_written;
        ret = bytes_written;
out:
        __asm__ __volatile__("membar #Sync");
        kfree(ver_buf);
        return ret;
}

static loff_t adi_llseek(struct file *file, loff_t offset, int whence)
{
        loff_t ret = -EINVAL;

        switch (whence) {
        case SEEK_END:
        case SEEK_DATA:
        case SEEK_HOLE:
                /* unsupported */
                return -EINVAL;
        case SEEK_CUR:
                if (offset == 0)
                        return file->f_pos;

                offset += file->f_pos;
                break;
        case SEEK_SET:
                break;
        }

        if (offset != file->f_pos) {
                file->f_pos = offset;
                ret = offset;
        }

        return ret;
}

static const struct file_operations adi_fops = {
        .owner          = THIS_MODULE,
        .llseek         = adi_llseek,
        .read           = adi_read,
        .write          = adi_write,
        .fop_flags      = FOP_UNSIGNED_OFFSET,
};

static struct miscdevice adi_miscdev = {
        .minor = MISC_DYNAMIC_MINOR,
        .name = KBUILD_MODNAME,
        .fops = &adi_fops,
};

static int __init adi_init(void)
{
        if (!adi_capable())
                return -EPERM;

        return misc_register(&adi_miscdev);
}

static void __exit adi_exit(void)
{
        misc_deregister(&adi_miscdev);
}

module_init(adi_init);
module_exit(adi_exit);

MODULE_AUTHOR("Tom Hromatka <tom.hromatka@oracle.com>");
MODULE_DESCRIPTION("Privileged interface to ADI");
MODULE_VERSION("1.0");
MODULE_LICENSE("GPL v2");