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
  18 /*
  19  * This function writes to kernel memory bypassing DAT and possible
  20  * write protection. It copies one to four bytes from src to dst
  21  * using the stura instruction.
  22  * Returns the number of bytes copied or -EFAULT.
  23  */
  24 static long probe_kernel_write_odd(void *dst, const void *src, size_t size)
  25 {
  26         unsigned long count, aligned;
  27         int offset, mask;
  28         int rc = -EFAULT;
  29
  30         aligned = (unsigned long) dst & ~3UL;
  31         offset = (unsigned long) dst & 3;
  32         count = min_t(unsigned long, 4 - offset, size);
  33         mask = (0xf << (4 - count)) & 0xf;
  34         mask >>= offset;
  35         asm volatile(
  36                 "       bras    1,0f\n"
  37                 "       icm     0,0,0(%3)\n"
  38                 "0:     l       0,0(%1)\n"
  39                 "       lra     %1,0(%1)\n"
  40                 "1:     ex      %2,0(1)\n"
  41                 "2:     stura   0,%1\n"
  42                 "       la      %0,0\n"
  43                 "3:\n"
  44                 EX_TABLE(0b,3b) EX_TABLE(1b,3b) EX_TABLE(2b,3b)
  45                 : "+d" (rc), "+a" (aligned)
  46                 : "a" (mask), "a" (src) : "cc", "memory", "0", "1");
  47         return rc ? rc : count;
  48 }
  49
  50 long probe_kernel_write(void *dst, const void *src, size_t size)
  51 {
  52         long copied = 0;
  53
  54         while (size) {
  55                 copied = probe_kernel_write_odd(dst, src, size);
  56                 if (copied < 0)
  57                         break;
  58                 dst += copied;
  59                 src += copied;
  60                 size -= copied;
  61         }
  62         return copied < 0 ? -EFAULT : 0;
  63 }
  64
  65 static int __memcpy_real(void *dest, void *src, size_t count)
  66 {
  67         register unsigned long _dest asm("2") = (unsigned long) dest;
  68         register unsigned long _len1 asm("3") = (unsigned long) count;
  69         register unsigned long _src  asm("4") = (unsigned long) src;
  70         register unsigned long _len2 asm("5") = (unsigned long) count;
  71         int rc = -EFAULT;
  72
  73         asm volatile (
  74                 "0:     mvcle   %1,%2,0x0\n"
  75                 "1:     jo      0b\n"
  76                 "       lhi     %0,0x0\n"
  77                 "2:\n"
  78                 EX_TABLE(1b,2b)
  79                 : "+d" (rc), "+d" (_dest), "+d" (_src), "+d" (_len1),
  80                   "+d" (_len2), "=m" (*((long *) dest))
  81                 : "m" (*((long *) src))
  82                 : "cc", "memory");
  83         return rc;
  84 }
  85
  86 /*
  87  * Copy memory in real mode (kernel to kernel)
  88  */
  89 int memcpy_real(void *dest, void *src, size_t count)
  90 {
  91         unsigned long flags;
  92         int rc;
  93
  94         if (!count)
  95                 return 0;
  96         local_irq_save(flags);
  97         __arch_local_irq_stnsm(0xfbUL);
  98         rc = __memcpy_real(dest, src, count);
  99         local_irq_restore(flags);
 100         return rc;
 101 }
 102
 103 /*
 104  * Copy memory in absolute mode (kernel to kernel)
 105  */
 106 void memcpy_absolute(void *dest, void *src, size_t count)
 107 {
 108         unsigned long cr0, flags, prefix;
 109
 110         flags = arch_local_irq_save();
 111         __ctl_store(cr0, 0, 0);
 112         __ctl_clear_bit(0, 28); /* disable lowcore protection */
 113         prefix = store_prefix();
 114         if (prefix) {
 115                 local_mcck_disable();
 116                 set_prefix(0);
 117                 memcpy(dest, src, count);
 118                 set_prefix(prefix);
 119                 local_mcck_enable();
 120         } else {
 121                 memcpy(dest, src, count);
 122         }
 123         __ctl_load(cr0, 0, 0);
 124         arch_local_irq_restore(flags);
 125 }
 126
 127 /*
 128  * Copy memory from kernel (real) to user (virtual)
 129  */
 130 int copy_to_user_real(void __user *dest, void *src, size_t count)
 131 {
 132         int offs = 0, size, rc;
 133         char *buf;
 134
 135         buf = (char *) __get_free_page(GFP_KERNEL);
 136         if (!buf)
 137                 return -ENOMEM;
 138         rc = -EFAULT;
 139         while (offs < count) {
 140                 size = min(PAGE_SIZE, count - offs);
 141                 if (memcpy_real(buf, src + offs, size))
 142                         goto out;
 143                 if (copy_to_user(dest + offs, buf, size))
 144                         goto out;
 145                 offs += size;
 146         }
 147         rc = 0;
 148 out:
 149         free_page((unsigned long) buf);
 150         return rc;
 151 }
 152
 153 /*
 154  * Copy memory from user (virtual) to kernel (real)
 155  */
 156 int copy_from_user_real(void *dest, void __user *src, size_t count)
 157 {
 158         int offs = 0, size, rc;
 159         char *buf;
 160
 161         buf = (char *) __get_free_page(GFP_KERNEL);
 162         if (!buf)
 163                 return -ENOMEM;
 164         rc = -EFAULT;
 165         while (offs < count) {
 166                 size = min(PAGE_SIZE, count - offs);
 167                 if (copy_from_user(buf, src + offs, size))
 168                         goto out;
 169                 if (memcpy_real(dest + offs, buf, size))
 170                         goto out;
 171                 offs += size;
 172         }
 173         rc = 0;
 174 out:
 175         free_page((unsigned long) buf);
 176         return rc;
 177 }
 178
 179 /*
 180  * Check if physical address is within prefix or zero page
 181  */
 182 static int is_swapped(unsigned long addr)
 183 {
 184         unsigned long lc;
 185         int cpu;
 186
 187         if (addr < sizeof(struct _lowcore))
 188                 return 1;
 189         for_each_online_cpu(cpu) {
 190                 lc = (unsigned long) lowcore_ptr[cpu];
 191                 if (addr > lc + sizeof(struct _lowcore) - 1 || addr < lc)
 192                         continue;
 193                 return 1;
 194         }
 195         return 0;
 196 }
 197
 198 /*
 199  * Convert a physical pointer for /dev/mem access
 200  *
 201  * For swapped prefix pages a new buffer is returned that contains a copy of
 202  * the absolute memory. The buffer size is maximum one page large.
 203  */
 204 void *xlate_dev_mem_ptr(unsigned long addr)
 205 {
 206         void *bounce = (void *) addr;
 207         unsigned long size;
 208
 209         get_online_cpus();
 210         preempt_disable();
 211         if (is_swapped(addr)) {
 212                 size = PAGE_SIZE - (addr & ~PAGE_MASK);
 213                 bounce = (void *) __get_free_page(GFP_ATOMIC);
 214                 if (bounce)
 215                         memcpy_absolute(bounce, (void *) addr, size);
 216         }
 217         preempt_enable();
 218         put_online_cpus();
 219         return bounce;
 220 }
 221
 222 /*
 223  * Free converted buffer for /dev/mem access (if necessary)
 224  */
 225 void unxlate_dev_mem_ptr(unsigned long addr, void *buf)
 226 {
 227         if ((void *) addr != buf)
 228                 free_page((unsigned long) buf);
 229 }