arch/s390/mm/maccess.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Access kernel memory without faulting -- s390 specific implementation.
   4  *
   5  * Copyright IBM Corp. 2009, 2015
   6  *
   7  *   Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>,
   8  *
   9  */
  10
  11 #include <linux/uaccess.h>
  12 #include <linux/kernel.h>
  13 #include <linux/types.h>
  14 #include <linux/errno.h>
  15 #include <linux/gfp.h>
  16 #include <linux/cpu.h>
  17 #include <asm/ctl_reg.h>
  18 #include <asm/io.h>
  19
  20 static notrace long s390_kernel_write_odd(void *dst, const void *src, size_t size)
  21 {
  22         unsigned long aligned, offset, count;
  23         char tmp[8];
  24
  25         aligned = (unsigned long) dst & ~7UL;
  26         offset = (unsigned long) dst & 7UL;
  27         size = min(8UL - offset, size);
  28         count = size - 1;
  29         asm volatile(
  30                 "       bras    1,0f\n"
  31                 "       mvc     0(1,%4),0(%5)\n"
  32                 "0:     mvc     0(8,%3),0(%0)\n"
  33                 "       ex      %1,0(1)\n"
  34                 "       lg      %1,0(%3)\n"
  35                 "       lra     %0,0(%0)\n"
  36                 "       sturg   %1,%0\n"
  37                 : "+&a" (aligned), "+&a" (count), "=m" (tmp)
  38                 : "a" (&tmp), "a" (&tmp[offset]), "a" (src)
  39                 : "cc", "memory", "1");
  40         return size;
  41 }
  42
  43 /*
  44  * s390_kernel_write - write to kernel memory bypassing DAT
  45  * @dst: destination address
  46  * @src: source address
  47  * @size: number of bytes to copy
  48  *
  49  * This function writes to kernel memory bypassing DAT and possible page table
  50  * write protection. It writes to the destination using the sturg instruction.
  51  * Therefore we have a read-modify-write sequence: the function reads eight
  52  * bytes from destination at an eight byte boundary, modifies the bytes
  53  * requested and writes the result back in a loop.
  54  *
  55  * Note: this means that this function may not be called concurrently on
  56  *       several cpus with overlapping words, since this may potentially
  57  *       cause data corruption.
  58  */
  59 void notrace s390_kernel_write(void *dst, const void *src, size_t size)
  60 {
  61         long copied;
  62
  63         while (size) {
  64                 copied = s390_kernel_write_odd(dst, src, size);
  65                 dst += copied;
  66                 src += copied;
  67                 size -= copied;
  68         }
  69 }
  70
  71 static int __memcpy_real(void *dest, void *src, size_t count)
  72 {
  73         register unsigned long _dest asm("2") = (unsigned long) dest;
  74         register unsigned long _len1 asm("3") = (unsigned long) count;
  75         register unsigned long _src  asm("4") = (unsigned long) src;
  76         register unsigned long _len2 asm("5") = (unsigned long) count;
  77         int rc = -EFAULT;
  78
  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         return rc;
  90 }
  91
  92 /*
  93  * Copy memory in real mode (kernel to kernel)
  94  */
  95 int memcpy_real(void *dest, void *src, size_t count)
  96 {
  97         int irqs_disabled, rc;
  98         unsigned long flags;
  99
 100         if (!count)
 101                 return 0;
 102         flags = __arch_local_irq_stnsm(0xf8UL);
 103         irqs_disabled = arch_irqs_disabled_flags(flags);
 104         if (!irqs_disabled)
 105                 trace_hardirqs_off();
 106         rc = __memcpy_real(dest, src, count);
 107         if (!irqs_disabled)
 108                 trace_hardirqs_on();
 109         __arch_local_irq_ssm(flags);
 110         return rc;
 111 }
 112
 113 /*
 114  * Copy memory in absolute mode (kernel to kernel)
 115  */
 116 void memcpy_absolute(void *dest, void *src, size_t count)
 117 {
 118         unsigned long cr0, flags, prefix;
 119
 120         flags = arch_local_irq_save();
 121         __ctl_store(cr0, 0, 0);
 122         __ctl_clear_bit(0, 28); /* disable lowcore protection */
 123         prefix = store_prefix();
 124         if (prefix) {
 125                 local_mcck_disable();
 126                 set_prefix(0);
 127                 memcpy(dest, src, count);
 128                 set_prefix(prefix);
 129                 local_mcck_enable();
 130         } else {
 131                 memcpy(dest, src, count);
 132         }
 133         __ctl_load(cr0, 0, 0);
 134         arch_local_irq_restore(flags);
 135 }
 136
 137 /*
 138  * Copy memory from kernel (real) to user (virtual)
 139  */
 140 int copy_to_user_real(void __user *dest, void *src, unsigned long count)
 141 {
 142         int offs = 0, size, rc;
 143         char *buf;
 144
 145         buf = (char *) __get_free_page(GFP_KERNEL);
 146         if (!buf)
 147                 return -ENOMEM;
 148         rc = -EFAULT;
 149         while (offs < count) {
 150                 size = min(PAGE_SIZE, count - offs);
 151                 if (memcpy_real(buf, src + offs, size))
 152                         goto out;
 153                 if (copy_to_user(dest + offs, buf, size))
 154                         goto out;
 155                 offs += size;
 156         }
 157         rc = 0;
 158 out:
 159         free_page((unsigned long) buf);
 160         return rc;
 161 }
 162
 163 /*
 164  * Check if physical address is within prefix or zero page
 165  */
 166 static int is_swapped(unsigned long addr)
 167 {
 168         unsigned long lc;
 169         int cpu;
 170
 171         if (addr < sizeof(struct lowcore))
 172                 return 1;
 173         for_each_online_cpu(cpu) {
 174                 lc = (unsigned long) lowcore_ptr[cpu];
 175                 if (addr > lc + sizeof(struct lowcore) - 1 || addr < lc)
 176                         continue;
 177                 return 1;
 178         }
 179         return 0;
 180 }
 181
 182 /*
 183  * Convert a physical pointer for /dev/mem access
 184  *
 185  * For swapped prefix pages a new buffer is returned that contains a copy of
 186  * the absolute memory. The buffer size is maximum one page large.
 187  */
 188 void *xlate_dev_mem_ptr(phys_addr_t addr)
 189 {
 190         void *bounce = (void *) addr;
 191         unsigned long size;
 192
 193         get_online_cpus();
 194         preempt_disable();
 195         if (is_swapped(addr)) {
 196                 size = PAGE_SIZE - (addr & ~PAGE_MASK);
 197                 bounce = (void *) __get_free_page(GFP_ATOMIC);
 198                 if (bounce)
 199                         memcpy_absolute(bounce, (void *) addr, size);
 200         }
 201         preempt_enable();
 202         put_online_cpus();
 203         return bounce;
 204 }
 205
 206 /*
 207  * Free converted buffer for /dev/mem access (if necessary)
 208  */
 209 void unxlate_dev_mem_ptr(phys_addr_t addr, void *buf)
 210 {
 211         if ((void *) addr != buf)
 212                 free_page((unsigned long) buf);
 213 }