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 #include <asm/stacktrace.h>
  20
  21 static notrace long s390_kernel_write_odd(void *dst, const void *src, size_t size)
  22 {
  23         unsigned long aligned, offset, count;
  24         char tmp[8];
  25
  26         aligned = (unsigned long) dst & ~7UL;
  27         offset = (unsigned long) dst & 7UL;
  28         size = min(8UL - offset, size);
  29         count = size - 1;
  30         asm volatile(
  31                 "       bras    1,0f\n"
  32                 "       mvc     0(1,%4),0(%5)\n"
  33                 "0:     mvc     0(8,%3),0(%0)\n"
  34                 "       ex      %1,0(1)\n"
  35                 "       lg      %1,0(%3)\n"
  36                 "       lra     %0,0(%0)\n"
  37                 "       sturg   %1,%0\n"
  38                 : "+&a" (aligned), "+&a" (count), "=m" (tmp)
  39                 : "a" (&tmp), "a" (&tmp[offset]), "a" (src)
  40                 : "cc", "memory", "1");
  41         return size;
  42 }
  43
  44 /*
  45  * s390_kernel_write - write to kernel memory bypassing DAT
  46  * @dst: destination address
  47  * @src: source address
  48  * @size: number of bytes to copy
  49  *
  50  * This function writes to kernel memory bypassing DAT and possible page table
  51  * write protection. It writes to the destination using the sturg instruction.
  52  * Therefore we have a read-modify-write sequence: the function reads eight
  53  * bytes from destination at an eight byte boundary, modifies the bytes
  54  * requested and writes the result back in a loop.
  55  *
  56  * Note: this means that this function may not be called concurrently on
  57  *       several cpus with overlapping words, since this may potentially
  58  *       cause data corruption.
  59  */
  60 void notrace s390_kernel_write(void *dst, const void *src, size_t size)
  61 {
  62         long copied;
  63
  64         while (size) {
  65                 copied = s390_kernel_write_odd(dst, src, size);
  66                 dst += copied;
  67                 src += copied;
  68                 size -= copied;
  69         }
  70 }
  71
  72 static int __memcpy_real(void *dest, void *src, size_t count)
  73 {
  74         register unsigned long _dest asm("2") = (unsigned long) dest;
  75         register unsigned long _len1 asm("3") = (unsigned long) count;
  76         register unsigned long _src  asm("4") = (unsigned long) src;
  77         register unsigned long _len2 asm("5") = (unsigned long) count;
  78         int rc = -EFAULT;
  79
  80         asm volatile (
  81                 "0:     mvcle   %1,%2,0x0\n"
  82                 "1:     jo      0b\n"
  83                 "       lhi     %0,0x0\n"
  84                 "2:\n"
  85                 EX_TABLE(1b,2b)
  86                 : "+d" (rc), "+d" (_dest), "+d" (_src), "+d" (_len1),
  87                   "+d" (_len2), "=m" (*((long *) dest))
  88                 : "m" (*((long *) src))
  89                 : "cc", "memory");
  90         return rc;
  91 }
  92
  93 static unsigned long _memcpy_real(unsigned long dest, unsigned long src,
  94                                   unsigned long 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((void *) dest, (void *) src, (size_t) 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 real mode (kernel to kernel)
 114  */
 115 int memcpy_real(void *dest, void *src, size_t count)
 116 {
 117         if (S390_lowcore.nodat_stack != 0)
 118                 return CALL_ON_STACK(_memcpy_real, S390_lowcore.nodat_stack,
 119                                      3, dest, src, count);
 120         /*
 121          * This is a really early memcpy_real call, the stacks are
 122          * not set up yet. Just call _memcpy_real on the early boot
 123          * stack
 124          */
 125         return _memcpy_real((unsigned long) dest,(unsigned long) src,
 126                             (unsigned long) count);
 127 }
 128
 129 /*
 130  * Copy memory in absolute mode (kernel to kernel)
 131  */
 132 void memcpy_absolute(void *dest, void *src, size_t count)
 133 {
 134         unsigned long cr0, flags, prefix;
 135
 136         flags = arch_local_irq_save();
 137         __ctl_store(cr0, 0, 0);
 138         __ctl_clear_bit(0, 28); /* disable lowcore protection */
 139         prefix = store_prefix();
 140         if (prefix) {
 141                 local_mcck_disable();
 142                 set_prefix(0);
 143                 memcpy(dest, src, count);
 144                 set_prefix(prefix);
 145                 local_mcck_enable();
 146         } else {
 147                 memcpy(dest, src, count);
 148         }
 149         __ctl_load(cr0, 0, 0);
 150         arch_local_irq_restore(flags);
 151 }
 152
 153 /*
 154  * Copy memory from kernel (real) to user (virtual)
 155  */
 156 int copy_to_user_real(void __user *dest, void *src, unsigned long 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 (memcpy_real(buf, src + offs, size))
 168                         goto out;
 169                 if (copy_to_user(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(phys_addr_t 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(phys_addr_t addr, void *buf)
 226 {
 227         if ((void *) addr != buf)
 228                 free_page((unsigned long) buf);
 229 }