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 <linux/cpu.h>
  16 #include <asm/ctl_reg.h>
  17 #include <asm/io.h>
  18
  19 /*
  20  * This function writes to kernel memory bypassing DAT and possible
  21  * write protection. It copies one to four bytes from src to dst
  22  * using the stura instruction.
  23  * Returns the number of bytes copied or -EFAULT.
  24  */
  25 static long probe_kernel_write_odd(void *dst, const void *src, size_t size)
  26 {
  27         unsigned long count, aligned;
  28         int offset, mask;
  29         int rc = -EFAULT;
  30
  31         aligned = (unsigned long) dst & ~3UL;
  32         offset = (unsigned long) dst & 3;
  33         count = min_t(unsigned long, 4 - offset, size);
  34         mask = (0xf << (4 - count)) & 0xf;
  35         mask >>= offset;
  36         asm volatile(
  37                 "       bras    1,0f\n"
  38                 "       icm     0,0,0(%3)\n"
  39                 "0:     l       0,0(%1)\n"
  40                 "       lra     %1,0(%1)\n"
  41                 "1:     ex      %2,0(1)\n"
  42                 "2:     stura   0,%1\n"
  43                 "       la      %0,0\n"
  44                 "3:\n"
  45                 EX_TABLE(0b,3b) EX_TABLE(1b,3b) EX_TABLE(2b,3b)
  46                 : "+d" (rc), "+a" (aligned)
  47                 : "a" (mask), "a" (src) : "cc", "memory", "0", "1");
  48         return rc ? rc : count;
  49 }
  50
  51 long probe_kernel_write(void *dst, const void *src, size_t size)
  52 {
  53         long copied = 0;
  54
  55         while (size) {
  56                 copied = probe_kernel_write_odd(dst, src, size);
  57                 if (copied < 0)
  58                         break;
  59                 dst += copied;
  60                 src += copied;
  61                 size -= copied;
  62         }
  63         return copied < 0 ? -EFAULT : 0;
  64 }
  65
  66 static int __memcpy_real(void *dest, void *src, size_t count)
  67 {
  68         register unsigned long _dest asm("2") = (unsigned long) dest;
  69         register unsigned long _len1 asm("3") = (unsigned long) count;
  70         register unsigned long _src  asm("4") = (unsigned long) src;
  71         register unsigned long _len2 asm("5") = (unsigned long) count;
  72         int rc = -EFAULT;
  73
  74         asm volatile (
  75                 "0:     mvcle   %1,%2,0x0\n"
  76                 "1:     jo      0b\n"
  77                 "       lhi     %0,0x0\n"
  78                 "2:\n"
  79                 EX_TABLE(1b,2b)
  80                 : "+d" (rc), "+d" (_dest), "+d" (_src), "+d" (_len1),
  81                   "+d" (_len2), "=m" (*((long *) dest))
  82                 : "m" (*((long *) src))
  83                 : "cc", "memory");
  84         return rc;
  85 }
  86
  87 /*
  88  * Copy memory in real mode (kernel to kernel)
  89  */
  90 int memcpy_real(void *dest, void *src, size_t count)
  91 {
  92         unsigned long flags;
  93         int rc;
  94
  95         if (!count)
  96                 return 0;
  97         local_irq_save(flags);
  98         __arch_local_irq_stnsm(0xfbUL);
  99         rc = __memcpy_real(dest, src, count);
 100         local_irq_restore(flags);
 101         return rc;
 102 }
 103
 104 /*
 105  * Copy memory in absolute mode (kernel to kernel)
 106  */
 107 void memcpy_absolute(void *dest, void *src, size_t count)
 108 {
 109         unsigned long cr0, flags, prefix;
 110
 111         flags = arch_local_irq_save();
 112         __ctl_store(cr0, 0, 0);
 113         __ctl_clear_bit(0, 28); /* disable lowcore protection */
 114         prefix = store_prefix();
 115         if (prefix) {
 116                 local_mcck_disable();
 117                 set_prefix(0);
 118                 memcpy(dest, src, count);
 119                 set_prefix(prefix);
 120                 local_mcck_enable();
 121         } else {
 122                 memcpy(dest, src, count);
 123         }
 124         __ctl_load(cr0, 0, 0);
 125         arch_local_irq_restore(flags);
 126 }
 127
 128 /*
 129  * Copy memory from kernel (real) to user (virtual)
 130  */
 131 int copy_to_user_real(void __user *dest, void *src, unsigned long count)
 132 {
 133         int offs = 0, size, rc;
 134         char *buf;
 135
 136         buf = (char *) __get_free_page(GFP_KERNEL);
 137         if (!buf)
 138                 return -ENOMEM;
 139         rc = -EFAULT;
 140         while (offs < count) {
 141                 size = min(PAGE_SIZE, count - offs);
 142                 if (memcpy_real(buf, src + offs, size))
 143                         goto out;
 144                 if (copy_to_user(dest + offs, buf, size))
 145                         goto out;
 146                 offs += size;
 147         }
 148         rc = 0;
 149 out:
 150         free_page((unsigned long) buf);
 151         return rc;
 152 }
 153
 154 /*
 155  * Check if physical address is within prefix or zero page
 156  */
 157 static int is_swapped(unsigned long addr)
 158 {
 159         unsigned long lc;
 160         int cpu;
 161
 162         if (addr < sizeof(struct _lowcore))
 163                 return 1;
 164         for_each_online_cpu(cpu) {
 165                 lc = (unsigned long) lowcore_ptr[cpu];
 166                 if (addr > lc + sizeof(struct _lowcore) - 1 || addr < lc)
 167                         continue;
 168                 return 1;
 169         }
 170         return 0;
 171 }
 172
 173 /*
 174  * Convert a physical pointer for /dev/mem access
 175  *
 176  * For swapped prefix pages a new buffer is returned that contains a copy of
 177  * the absolute memory. The buffer size is maximum one page large.
 178  */
 179 void *xlate_dev_mem_ptr(unsigned long addr)
 180 {
 181         void *bounce = (void *) addr;
 182         unsigned long size;
 183
 184         get_online_cpus();
 185         preempt_disable();
 186         if (is_swapped(addr)) {
 187                 size = PAGE_SIZE - (addr & ~PAGE_MASK);
 188                 bounce = (void *) __get_free_page(GFP_ATOMIC);
 189                 if (bounce)
 190                         memcpy_absolute(bounce, (void *) addr, size);
 191         }
 192         preempt_enable();
 193         put_online_cpus();
 194         return bounce;
 195 }
 196
 197 /*
 198  * Free converted buffer for /dev/mem access (if necessary)
 199  */
 200 void unxlate_dev_mem_ptr(unsigned long addr, void *buf)
 201 {
 202         if ((void *) addr != buf)
 203                 free_page((unsigned long) buf);
 204 }