drivers/char/adi.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * Privileged ADI driver for sparc64
0004  *
0005  * Author: Tom Hromatka <tom.hromatka@oracle.com>
0006  */
0007 #include <linux/kernel.h>
0008 #include <linux/miscdevice.h>
0009 #include <linux/module.h>
0010 #include <linux/proc_fs.h>
0011 #include <linux/slab.h>
0012 #include <linux/uaccess.h>
0013 #include <asm/asi.h>
0014
0015 #define MAX_BUF_SZ  PAGE_SIZE
0016
0017 static int adi_open(struct inode *inode, struct file *file)
0018 {
0019     file->f_mode |= FMODE_UNSIGNED_OFFSET;
0020     return 0;
0021 }
0022
0023 static int read_mcd_tag(unsigned long addr)
0024 {
0025     long err;
0026     int ver;
0027
0028     __asm__ __volatile__(
0029         "1: ldxa [%[addr]] %[asi], %[ver]\n"
0030         "   mov 0, %[err]\n"
0031         "2:\n"
0032         "   .section .fixup,#alloc,#execinstr\n"
0033         "   .align 4\n"
0034         "3: sethi %%hi(2b), %%g1\n"
0035         "   jmpl  %%g1 + %%lo(2b), %%g0\n"
0036         "   mov %[invalid], %[err]\n"
0037         "   .previous\n"
0038         "   .section __ex_table, \"a\"\n"
0039         "   .align 4\n"
0040         "   .word  1b, 3b\n"
0041         "   .previous\n"
0042         : [ver] "=r" (ver), [err] "=r" (err)
0043         : [addr] "r"  (addr), [invalid] "i" (EFAULT),
0044           [asi] "i" (ASI_MCD_REAL)
0045         : "memory", "g1"
0046         );
0047
0048     if (err)
0049         return -EFAULT;
0050     else
0051         return ver;
0052 }
0053
0054 static ssize_t adi_read(struct file *file, char __user *buf,
0055             size_t count, loff_t *offp)
0056 {
0057     size_t ver_buf_sz, bytes_read = 0;
0058     int ver_buf_idx = 0;
0059     loff_t offset;
0060     u8 *ver_buf;
0061     ssize_t ret;
0062
0063     ver_buf_sz = min_t(size_t, count, MAX_BUF_SZ);
0064     ver_buf = kmalloc(ver_buf_sz, GFP_KERNEL);
0065     if (!ver_buf)
0066         return -ENOMEM;
0067
0068     offset = (*offp) * adi_blksize();
0069
0070     while (bytes_read < count) {
0071         ret = read_mcd_tag(offset);
0072         if (ret < 0)
0073             goto out;
0074
0075         ver_buf[ver_buf_idx] = (u8)ret;
0076         ver_buf_idx++;
0077         offset += adi_blksize();
0078
0079         if (ver_buf_idx >= ver_buf_sz) {
0080             if (copy_to_user(buf + bytes_read, ver_buf,
0081                      ver_buf_sz)) {
0082                 ret = -EFAULT;
0083                 goto out;
0084             }
0085
0086             bytes_read += ver_buf_sz;
0087             ver_buf_idx = 0;
0088
0089             ver_buf_sz = min(count - bytes_read,
0090                      (size_t)MAX_BUF_SZ);
0091         }
0092     }
0093
0094     (*offp) += bytes_read;
0095     ret = bytes_read;
0096 out:
0097     kfree(ver_buf);
0098     return ret;
0099 }
0100
0101 static int set_mcd_tag(unsigned long addr, u8 ver)
0102 {
0103     long err;
0104
0105     __asm__ __volatile__(
0106         "1: stxa %[ver], [%[addr]] %[asi]\n"
0107         "   mov 0, %[err]\n"
0108         "2:\n"
0109         "   .section .fixup,#alloc,#execinstr\n"
0110         "   .align 4\n"
0111         "3: sethi %%hi(2b), %%g1\n"
0112         "   jmpl %%g1 + %%lo(2b), %%g0\n"
0113         "   mov %[invalid], %[err]\n"
0114         "   .previous\n"
0115         "   .section __ex_table, \"a\"\n"
0116         "   .align 4\n"
0117         "   .word 1b, 3b\n"
0118         "   .previous\n"
0119         : [err] "=r" (err)
0120         : [ver] "r" (ver), [addr] "r"  (addr),
0121           [invalid] "i" (EFAULT), [asi] "i" (ASI_MCD_REAL)
0122         : "memory", "g1"
0123         );
0124
0125     if (err)
0126         return -EFAULT;
0127     else
0128         return ver;
0129 }
0130
0131 static ssize_t adi_write(struct file *file, const char __user *buf,
0132              size_t count, loff_t *offp)
0133 {
0134     size_t ver_buf_sz, bytes_written = 0;
0135     loff_t offset;
0136     u8 *ver_buf;
0137     ssize_t ret;
0138     int i;
0139
0140     if (count <= 0)
0141         return -EINVAL;
0142
0143     ver_buf_sz = min_t(size_t, count, MAX_BUF_SZ);
0144     ver_buf = kmalloc(ver_buf_sz, GFP_KERNEL);
0145     if (!ver_buf)
0146         return -ENOMEM;
0147
0148     offset = (*offp) * adi_blksize();
0149
0150     do {
0151         if (copy_from_user(ver_buf, &buf[bytes_written],
0152                    ver_buf_sz)) {
0153             ret = -EFAULT;
0154             goto out;
0155         }
0156
0157         for (i = 0; i < ver_buf_sz; i++) {
0158             ret = set_mcd_tag(offset, ver_buf[i]);
0159             if (ret < 0)
0160                 goto out;
0161
0162             offset += adi_blksize();
0163         }
0164
0165         bytes_written += ver_buf_sz;
0166         ver_buf_sz = min(count - bytes_written, (size_t)MAX_BUF_SZ);
0167     } while (bytes_written < count);
0168
0169     (*offp) += bytes_written;
0170     ret = bytes_written;
0171 out:
0172     __asm__ __volatile__("membar #Sync");
0173     kfree(ver_buf);
0174     return ret;
0175 }
0176
0177 static loff_t adi_llseek(struct file *file, loff_t offset, int whence)
0178 {
0179     loff_t ret = -EINVAL;
0180
0181     switch (whence) {
0182     case SEEK_END:
0183     case SEEK_DATA:
0184     case SEEK_HOLE:
0185         /* unsupported */
0186         return -EINVAL;
0187     case SEEK_CUR:
0188         if (offset == 0)
0189             return file->f_pos;
0190
0191         offset += file->f_pos;
0192         break;
0193     case SEEK_SET:
0194         break;
0195     }
0196
0197     if (offset != file->f_pos) {
0198         file->f_pos = offset;
0199         file->f_version = 0;
0200         ret = offset;
0201     }
0202
0203     return ret;
0204 }
0205
0206 static const struct file_operations adi_fops = {
0207     .owner      = THIS_MODULE,
0208     .llseek     = adi_llseek,
0209     .open       = adi_open,
0210     .read       = adi_read,
0211     .write      = adi_write,
0212 };
0213
0214 static struct miscdevice adi_miscdev = {
0215     .minor = MISC_DYNAMIC_MINOR,
0216     .name = KBUILD_MODNAME,
0217     .fops = &adi_fops,
0218 };
0219
0220 static int __init adi_init(void)
0221 {
0222     if (!adi_capable())
0223         return -EPERM;
0224
0225     return misc_register(&adi_miscdev);
0226 }
0227
0228 static void __exit adi_exit(void)
0229 {
0230     misc_deregister(&adi_miscdev);
0231 }
0232
0233 module_init(adi_init);
0234 module_exit(adi_exit);
0235
0236 MODULE_AUTHOR("Tom Hromatka <tom.hromatka@oracle.com>");
0237 MODULE_DESCRIPTION("Privileged interface to ADI");
0238 MODULE_VERSION("1.0");
0239 MODULE_LICENSE("GPL v2");