drivers/char/adi.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Privileged ADI driver for sparc64
   4  *
   5  * Author: Tom Hromatka <tom.hromatka@oracle.com>
   6  */
   7 #include <linux/kernel.h>
   8 #include <linux/miscdevice.h>
   9 #include <linux/module.h>
  10 #include <linux/proc_fs.h>
  11 #include <linux/slab.h>
  12 #include <linux/uaccess.h>
  13 #include <asm/asi.h>
  14
  15 #define MAX_BUF_SZ      PAGE_SIZE
  16
  17 static int read_mcd_tag(unsigned long addr)
  18 {
  19         long err;
  20         int ver;
  21
  22         __asm__ __volatile__(
  23                 "1:     ldxa [%[addr]] %[asi], %[ver]\n"
  24                 "       mov 0, %[err]\n"
  25                 "2:\n"
  26                 "       .section .fixup,#alloc,#execinstr\n"
  27                 "       .align 4\n"
  28                 "3:     sethi %%hi(2b), %%g1\n"
  29                 "       jmpl  %%g1 + %%lo(2b), %%g0\n"
  30                 "       mov %[invalid], %[err]\n"
  31                 "       .previous\n"
  32                 "       .section __ex_table, \"a\"\n"
  33                 "       .align 4\n"
  34                 "       .word  1b, 3b\n"
  35                 "       .previous\n"
  36                 : [ver] "=r" (ver), [err] "=r" (err)
  37                 : [addr] "r"  (addr), [invalid] "i" (EFAULT),
  38                   [asi] "i" (ASI_MCD_REAL)
  39                 : "memory", "g1"
  40                 );
  41
  42         if (err)
  43                 return -EFAULT;
  44         else
  45                 return ver;
  46 }
  47
  48 static ssize_t adi_read(struct file *file, char __user *buf,
  49                         size_t count, loff_t *offp)
  50 {
  51         size_t ver_buf_sz, bytes_read = 0;
  52         int ver_buf_idx = 0;
  53         loff_t offset;
  54         u8 *ver_buf;
  55         ssize_t ret;
  56
  57         ver_buf_sz = min_t(size_t, count, MAX_BUF_SZ);
  58         ver_buf = kmalloc(ver_buf_sz, GFP_KERNEL);
  59         if (!ver_buf)
  60                 return -ENOMEM;
  61
  62         offset = (*offp) * adi_blksize();
  63
  64         while (bytes_read < count) {
  65                 ret = read_mcd_tag(offset);
  66                 if (ret < 0)
  67                         goto out;
  68
  69                 ver_buf[ver_buf_idx] = (u8)ret;
  70                 ver_buf_idx++;
  71                 offset += adi_blksize();
  72
  73                 if (ver_buf_idx >= ver_buf_sz) {
  74                         if (copy_to_user(buf + bytes_read, ver_buf,
  75                                          ver_buf_sz)) {
  76                                 ret = -EFAULT;
  77                                 goto out;
  78                         }
  79
  80                         bytes_read += ver_buf_sz;
  81                         ver_buf_idx = 0;
  82
  83                         ver_buf_sz = min(count - bytes_read,
  84                                          (size_t)MAX_BUF_SZ);
  85                 }
  86         }
  87
  88         (*offp) += bytes_read;
  89         ret = bytes_read;
  90 out:
  91         kfree(ver_buf);
  92         return ret;
  93 }
  94
  95 static int set_mcd_tag(unsigned long addr, u8 ver)
  96 {
  97         long err;
  98
  99         __asm__ __volatile__(
 100                 "1:     stxa %[ver], [%[addr]] %[asi]\n"
 101                 "       mov 0, %[err]\n"
 102                 "2:\n"
 103                 "       .section .fixup,#alloc,#execinstr\n"
 104                 "       .align 4\n"
 105                 "3:     sethi %%hi(2b), %%g1\n"
 106                 "       jmpl %%g1 + %%lo(2b), %%g0\n"
 107                 "       mov %[invalid], %[err]\n"
 108                 "       .previous\n"
 109                 "       .section __ex_table, \"a\"\n"
 110                 "       .align 4\n"
 111                 "       .word 1b, 3b\n"
 112                 "       .previous\n"
 113                 : [err] "=r" (err)
 114                 : [ver] "r" (ver), [addr] "r"  (addr),
 115                   [invalid] "i" (EFAULT), [asi] "i" (ASI_MCD_REAL)
 116                 : "memory", "g1"
 117                 );
 118
 119         if (err)
 120                 return -EFAULT;
 121         else
 122                 return ver;
 123 }
 124
 125 static ssize_t adi_write(struct file *file, const char __user *buf,
 126                          size_t count, loff_t *offp)
 127 {
 128         size_t ver_buf_sz, bytes_written = 0;
 129         loff_t offset;
 130         u8 *ver_buf;
 131         ssize_t ret;
 132         int i;
 133
 134         if (count <= 0)
 135                 return -EINVAL;
 136
 137         ver_buf_sz = min_t(size_t, count, MAX_BUF_SZ);
 138         ver_buf = kmalloc(ver_buf_sz, GFP_KERNEL);
 139         if (!ver_buf)
 140                 return -ENOMEM;
 141
 142         offset = (*offp) * adi_blksize();
 143
 144         do {
 145                 if (copy_from_user(ver_buf, &buf[bytes_written],
 146                                    ver_buf_sz)) {
 147                         ret = -EFAULT;
 148                         goto out;
 149                 }
 150
 151                 for (i = 0; i < ver_buf_sz; i++) {
 152                         ret = set_mcd_tag(offset, ver_buf[i]);
 153                         if (ret < 0)
 154                                 goto out;
 155
 156                         offset += adi_blksize();
 157                 }
 158
 159                 bytes_written += ver_buf_sz;
 160                 ver_buf_sz = min(count - bytes_written, (size_t)MAX_BUF_SZ);
 161         } while (bytes_written < count);
 162
 163         (*offp) += bytes_written;
 164         ret = bytes_written;
 165 out:
 166         __asm__ __volatile__("membar #Sync");
 167         kfree(ver_buf);
 168         return ret;
 169 }
 170
 171 static loff_t adi_llseek(struct file *file, loff_t offset, int whence)
 172 {
 173         loff_t ret = -EINVAL;
 174
 175         switch (whence) {
 176         case SEEK_END:
 177         case SEEK_DATA:
 178         case SEEK_HOLE:
 179                 /* unsupported */
 180                 return -EINVAL;
 181         case SEEK_CUR:
 182                 if (offset == 0)
 183                         return file->f_pos;
 184
 185                 offset += file->f_pos;
 186                 break;
 187         case SEEK_SET:
 188                 break;
 189         }
 190
 191         if (offset != file->f_pos) {
 192                 file->f_pos = offset;
 193                 ret = offset;
 194         }
 195
 196         return ret;
 197 }
 198
 199 static const struct file_operations adi_fops = {
 200         .owner          = THIS_MODULE,
 201         .llseek         = adi_llseek,
 202         .read           = adi_read,
 203         .write          = adi_write,
 204         .fop_flags      = FOP_UNSIGNED_OFFSET,
 205 };
 206
 207 static struct miscdevice adi_miscdev = {
 208         .minor = MISC_DYNAMIC_MINOR,
 209         .name = KBUILD_MODNAME,
 210         .fops = &adi_fops,
 211 };
 212
 213 static int __init adi_init(void)
 214 {
 215         if (!adi_capable())
 216                 return -EPERM;
 217
 218         return misc_register(&adi_miscdev);
 219 }
 220
 221 static void __exit adi_exit(void)
 222 {
 223         misc_deregister(&adi_miscdev);
 224 }
 225
 226 module_init(adi_init);
 227 module_exit(adi_exit);
 228
 229 MODULE_AUTHOR("Tom Hromatka <tom.hromatka@oracle.com>");
 230 MODULE_DESCRIPTION("Privileged interface to ADI");
 231 MODULE_VERSION("1.0");
 232 MODULE_LICENSE("GPL v2");