arch/s390/mm/maccess.c

   1 /*
   2  * Access kernel memory without faulting -- s390 specific implementation.
   3  *
   4  * Copyright IBM Corp. 2009
   5  *
   6  *   Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>,
   7  *
   8  */
   9
  10 #include <linux/uaccess.h>
  11 #include <linux/kernel.h>
  12 #include <linux/types.h>
  13 #include <linux/errno.h>
  14 #include <linux/gfp.h>
  15 #include <asm/system.h>
  16
  17 /*
  18  * This function writes to kernel memory bypassing DAT and possible
  19  * write protection. It copies one to four bytes from src to dst
  20  * using the stura instruction.
  21  * Returns the number of bytes copied or -EFAULT.
  22  */
  23 static long probe_kernel_write_odd(void *dst, const void *src, size_t size)
  24 {
  25         unsigned long count, aligned;
  26         int offset, mask;
  27         int rc = -EFAULT;
  28
  29         aligned = (unsigned long) dst & ~3UL;
  30         offset = (unsigned long) dst & 3;
  31         count = min_t(unsigned long, 4 - offset, size);
  32         mask = (0xf << (4 - count)) & 0xf;
  33         mask >>= offset;
  34         asm volatile(
  35                 "       bras    1,0f\n"
  36                 "       icm     0,0,0(%3)\n"
  37                 "0:     l       0,0(%1)\n"
  38                 "       lra     %1,0(%1)\n"
  39                 "1:     ex      %2,0(1)\n"
  40                 "2:     stura   0,%1\n"
  41                 "       la      %0,0\n"
  42                 "3:\n"
  43                 EX_TABLE(0b,3b) EX_TABLE(1b,3b) EX_TABLE(2b,3b)
  44                 : "+d" (rc), "+a" (aligned)
  45                 : "a" (mask), "a" (src) : "cc", "memory", "0", "1");
  46         return rc ? rc : count;
  47 }
  48
  49 long probe_kernel_write(void *dst, const void *src, size_t size)
  50 {
  51         long copied = 0;
  52
  53         while (size) {
  54                 copied = probe_kernel_write_odd(dst, src, size);
  55                 if (copied < 0)
  56                         break;
  57                 dst += copied;
  58                 src += copied;
  59                 size -= copied;
  60         }
  61         return copied < 0 ? -EFAULT : 0;
  62 }
  63
  64 /*
  65  * Copy memory in real mode (kernel to kernel)
  66  */
  67 int memcpy_real(void *dest, void *src, size_t count)
  68 {
  69         register unsigned long _dest asm("2") = (unsigned long) dest;
  70         register unsigned long _len1 asm("3") = (unsigned long) count;
  71         register unsigned long _src  asm("4") = (unsigned long) src;
  72         register unsigned long _len2 asm("5") = (unsigned long) count;
  73         unsigned long flags;
  74         int rc = -EFAULT;
  75
  76         if (!count)
  77                 return 0;
  78         flags = __arch_local_irq_stnsm(0xf8UL);
  79         asm volatile (
  80                 "0:     mvcle   %1,%2,0x0\n"
  81                 "1:     jo      0b\n"
  82                 "       lhi     %0,0x0\n"
  83                 "2:\n"
  84                 EX_TABLE(1b,2b)
  85                 : "+d" (rc), "+d" (_dest), "+d" (_src), "+d" (_len1),
  86                   "+d" (_len2), "=m" (*((long *) dest))
  87                 : "m" (*((long *) src))
  88                 : "cc", "memory");
  89         arch_local_irq_restore(flags);
  90         return rc;
  91 }
  92
  93 /*
  94  * Copy memory to absolute zero
  95  */
  96 void copy_to_absolute_zero(void *dest, void *src, size_t count)
  97 {
  98         unsigned long cr0;
  99
 100         BUG_ON((unsigned long) dest + count >= sizeof(struct _lowcore));
 101         preempt_disable();
 102         __ctl_store(cr0, 0, 0);
 103         __ctl_clear_bit(0, 28); /* disable lowcore protection */
 104         memcpy_real(dest + store_prefix(), src, count);
 105         __ctl_load(cr0, 0, 0);
 106         preempt_enable();
 107 }
 108
 109 /*
 110  * Copy memory from kernel (real) to user (virtual)
 111  */
 112 int copy_to_user_real(void __user *dest, void *src, size_t count)
 113 {
 114         int offs = 0, size, rc;
 115         char *buf;
 116
 117         buf = (char *) __get_free_page(GFP_KERNEL);
 118         if (!buf)
 119                 return -ENOMEM;
 120         rc = -EFAULT;
 121         while (offs < count) {
 122                 size = min(PAGE_SIZE, count - offs);
 123                 if (memcpy_real(buf, src + offs, size))
 124                         goto out;
 125                 if (copy_to_user(dest + offs, buf, size))
 126                         goto out;
 127                 offs += size;
 128         }
 129         rc = 0;
 130 out:
 131         free_page((unsigned long) buf);
 132         return rc;
 133 }
 134
 135 /*
 136  * Copy memory from user (virtual) to kernel (real)
 137  */
 138 int copy_from_user_real(void *dest, void __user *src, size_t count)
 139 {
 140         int offs = 0, size, rc;
 141         char *buf;
 142
 143         buf = (char *) __get_free_page(GFP_KERNEL);
 144         if (!buf)
 145                 return -ENOMEM;
 146         rc = -EFAULT;
 147         while (offs < count) {
 148                 size = min(PAGE_SIZE, count - offs);
 149                 if (copy_from_user(buf, src + offs, size))
 150                         goto out;
 151                 if (memcpy_real(dest + offs, buf, size))
 152                         goto out;
 153                 offs += size;
 154         }
 155         rc = 0;
 156 out:
 157         free_page((unsigned long) buf);
 158         return rc;
 159 }
 160