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         unsigned long flags;
  97         int rc;
  98
  99         if (!count)
 100                 return 0;
 101         local_irq_save(flags);
 102         __arch_local_irq_stnsm(0xfbUL);
 103         rc = __memcpy_real(dest, src, count);
 104         local_irq_restore(flags);
 105         return rc;
 106 }
 107
 108 /*
 109  * Copy memory in absolute mode (kernel to kernel)
 110  */
 111 void memcpy_absolute(void *dest, void *src, size_t count)
 112 {
 113         unsigned long cr0, flags, prefix;
 114
 115         flags = arch_local_irq_save();
 116         __ctl_store(cr0, 0, 0);
 117         __ctl_clear_bit(0, 28); /* disable lowcore protection */
 118         prefix = store_prefix();
 119         if (prefix) {
 120                 local_mcck_disable();
 121                 set_prefix(0);
 122                 memcpy(dest, src, count);
 123                 set_prefix(prefix);
 124                 local_mcck_enable();
 125         } else {
 126                 memcpy(dest, src, count);
 127         }
 128         __ctl_load(cr0, 0, 0);
 129         arch_local_irq_restore(flags);
 130 }
 131
 132 /*
 133  * Copy memory from kernel (real) to user (virtual)
 134  */
 135 int copy_to_user_real(void __user *dest, void *src, unsigned long count)
 136 {
 137         int offs = 0, size, rc;
 138         char *buf;
 139
 140         buf = (char *) __get_free_page(GFP_KERNEL);
 141         if (!buf)
 142                 return -ENOMEM;
 143         rc = -EFAULT;
 144         while (offs < count) {
 145                 size = min(PAGE_SIZE, count - offs);
 146                 if (memcpy_real(buf, src + offs, size))
 147                         goto out;
 148                 if (copy_to_user(dest + offs, buf, size))
 149                         goto out;
 150                 offs += size;
 151         }
 152         rc = 0;
 153 out:
 154         free_page((unsigned long) buf);
 155         return rc;
 156 }
 157
 158 /*
 159  * Check if physical address is within prefix or zero page
 160  */
 161 static int is_swapped(unsigned long addr)
 162 {
 163         unsigned long lc;
 164         int cpu;
 165
 166         if (addr < sizeof(struct lowcore))
 167                 return 1;
 168         for_each_online_cpu(cpu) {
 169                 lc = (unsigned long) lowcore_ptr[cpu];
 170                 if (addr > lc + sizeof(struct lowcore) - 1 || addr < lc)
 171                         continue;
 172                 return 1;
 173         }
 174         return 0;
 175 }
 176
 177 /*
 178  * Convert a physical pointer for /dev/mem access
 179  *
 180  * For swapped prefix pages a new buffer is returned that contains a copy of
 181  * the absolute memory. The buffer size is maximum one page large.
 182  */
 183 void *xlate_dev_mem_ptr(phys_addr_t addr)
 184 {
 185         void *bounce = (void *) addr;
 186         unsigned long size;
 187
 188         get_online_cpus();
 189         preempt_disable();
 190         if (is_swapped(addr)) {
 191                 size = PAGE_SIZE - (addr & ~PAGE_MASK);
 192                 bounce = (void *) __get_free_page(GFP_ATOMIC);
 193                 if (bounce)
 194                         memcpy_absolute(bounce, (void *) addr, size);
 195         }
 196         preempt_enable();
 197         put_online_cpus();
 198         return bounce;
 199 }
 200
 201 /*
 202  * Free converted buffer for /dev/mem access (if necessary)
 203  */
 204 void unxlate_dev_mem_ptr(phys_addr_t addr, void *buf)
 205 {
 206         if ((void *) addr != buf)
 207                 free_page((unsigned long) buf);
 208 }