arch/s390/mm/maccess.c

   1 /*
   2  * Access kernel memory without faulting -- s390 specific implementation.
   3  *
   4  * Copyright IBM Corp. 2009, 2015
   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 static notrace long s390_kernel_write_odd(void *dst, const void *src, size_t size)
  20 {
  21         unsigned long aligned, offset, count;
  22         char tmp[8];
  23
  24         aligned = (unsigned long) dst & ~7UL;
  25         offset = (unsigned long) dst & 7UL;
  26         size = min(8UL - offset, size);
  27         count = size - 1;
  28         asm volatile(
  29                 "       bras    1,0f\n"
  30                 "       mvc     0(1,%4),0(%5)\n"
  31                 "0:     mvc     0(8,%3),0(%0)\n"
  32                 "       ex      %1,0(1)\n"
  33                 "       lg      %1,0(%3)\n"
  34                 "       lra     %0,0(%0)\n"
  35                 "       sturg   %1,%0\n"
  36                 : "+&a" (aligned), "+&a" (count), "=m" (tmp)
  37                 : "a" (&tmp), "a" (&tmp[offset]), "a" (src)
  38                 : "cc", "memory", "1");
  39         return size;
  40 }
  41
  42 /*
  43  * s390_kernel_write - write to kernel memory bypassing DAT
  44  * @dst: destination address
  45  * @src: source address
  46  * @size: number of bytes to copy
  47  *
  48  * This function writes to kernel memory bypassing DAT and possible page table
  49  * write protection. It writes to the destination using the sturg instruction.
  50  * Therefore we have a read-modify-write sequence: the function reads eight
  51  * bytes from destination at an eight byte boundary, modifies the bytes
  52  * requested and writes the result back in a loop.
  53  *
  54  * Note: this means that this function may not be called concurrently on
  55  *       several cpus with overlapping words, since this may potentially
  56  *       cause data corruption.
  57  */
  58 void notrace s390_kernel_write(void *dst, const void *src, size_t size)
  59 {
  60         long copied;
  61
  62         while (size) {
  63                 copied = s390_kernel_write_odd(dst, src, size);
  64                 dst += copied;
  65                 src += copied;
  66                 size -= copied;
  67         }
  68 }
  69
  70 static int __memcpy_real(void *dest, void *src, size_t count)
  71 {
  72         register unsigned long _dest asm("2") = (unsigned long) dest;
  73         register unsigned long _len1 asm("3") = (unsigned long) count;
  74         register unsigned long _src  asm("4") = (unsigned long) src;
  75         register unsigned long _len2 asm("5") = (unsigned long) count;
  76         int rc = -EFAULT;
  77
  78         asm volatile (
  79                 "0:     mvcle   %1,%2,0x0\n"
  80                 "1:     jo      0b\n"
  81                 "       lhi     %0,0x0\n"
  82                 "2:\n"
  83                 EX_TABLE(1b,2b)
  84                 : "+d" (rc), "+d" (_dest), "+d" (_src), "+d" (_len1),
  85                   "+d" (_len2), "=m" (*((long *) dest))
  86                 : "m" (*((long *) src))
  87                 : "cc", "memory");
  88         return rc;
  89 }
  90
  91 /*
  92  * Copy memory in real mode (kernel to kernel)
  93  */
  94 int memcpy_real(void *dest, void *src, size_t count)
  95 {
  96         int irqs_disabled, rc;
  97         unsigned long flags;
  98
  99         if (!count)
 100                 return 0;
 101         flags = __arch_local_irq_stnsm(0xf8UL);
 102         irqs_disabled = arch_irqs_disabled_flags(flags);
 103         if (!irqs_disabled)
 104                 trace_hardirqs_off();
 105         rc = __memcpy_real(dest, src, count);
 106         if (!irqs_disabled)
 107                 trace_hardirqs_on();
 108         __arch_local_irq_ssm(flags);
 109         return rc;
 110 }
 111
 112 /*
 113  * Copy memory in absolute mode (kernel to kernel)
 114  */
 115 void memcpy_absolute(void *dest, void *src, size_t count)
 116 {
 117         unsigned long cr0, flags, prefix;
 118
 119         flags = arch_local_irq_save();
 120         __ctl_store(cr0, 0, 0);
 121         __ctl_clear_bit(0, 28); /* disable lowcore protection */
 122         prefix = store_prefix();
 123         if (prefix) {
 124                 local_mcck_disable();
 125                 set_prefix(0);
 126                 memcpy(dest, src, count);
 127                 set_prefix(prefix);
 128                 local_mcck_enable();
 129         } else {
 130                 memcpy(dest, src, count);
 131         }
 132         __ctl_load(cr0, 0, 0);
 133         arch_local_irq_restore(flags);
 134 }
 135
 136 /*
 137  * Copy memory from kernel (real) to user (virtual)
 138  */
 139 int copy_to_user_real(void __user *dest, void *src, unsigned long count)
 140 {
 141         int offs = 0, size, rc;
 142         char *buf;
 143
 144         buf = (char *) __get_free_page(GFP_KERNEL);
 145         if (!buf)
 146                 return -ENOMEM;
 147         rc = -EFAULT;
 148         while (offs < count) {
 149                 size = min(PAGE_SIZE, count - offs);
 150                 if (memcpy_real(buf, src + offs, size))
 151                         goto out;
 152                 if (copy_to_user(dest + offs, buf, size))
 153                         goto out;
 154                 offs += size;
 155         }
 156         rc = 0;
 157 out:
 158         free_page((unsigned long) buf);
 159         return rc;
 160 }
 161
 162 /*
 163  * Check if physical address is within prefix or zero page
 164  */
 165 static int is_swapped(unsigned long addr)
 166 {
 167         unsigned long lc;
 168         int cpu;
 169
 170         if (addr < sizeof(struct lowcore))
 171                 return 1;
 172         for_each_online_cpu(cpu) {
 173                 lc = (unsigned long) lowcore_ptr[cpu];
 174                 if (addr > lc + sizeof(struct lowcore) - 1 || addr < lc)
 175                         continue;
 176                 return 1;
 177         }
 178         return 0;
 179 }
 180
 181 /*
 182  * Convert a physical pointer for /dev/mem access
 183  *
 184  * For swapped prefix pages a new buffer is returned that contains a copy of
 185  * the absolute memory. The buffer size is maximum one page large.
 186  */
 187 void *xlate_dev_mem_ptr(phys_addr_t addr)
 188 {
 189         void *bounce = (void *) addr;
 190         unsigned long size;
 191
 192         get_online_cpus();
 193         preempt_disable();
 194         if (is_swapped(addr)) {
 195                 size = PAGE_SIZE - (addr & ~PAGE_MASK);
 196                 bounce = (void *) __get_free_page(GFP_ATOMIC);
 197                 if (bounce)
 198                         memcpy_absolute(bounce, (void *) addr, size);
 199         }
 200         preempt_enable();
 201         put_online_cpus();
 202         return bounce;
 203 }
 204
 205 /*
 206  * Free converted buffer for /dev/mem access (if necessary)
 207  */
 208 void unxlate_dev_mem_ptr(phys_addr_t addr, void *buf)
 209 {
 210         if ((void *) addr != buf)
 211                 free_page((unsigned long) buf);
 212 }