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 static DEFINE_SPINLOCK(s390_kernel_write_lock);
  57
  58 void notrace s390_kernel_write(void *dst, const void *src, size_t size)
  59 {
  60         unsigned long flags;
  61         long copied;
  62
  63         spin_lock_irqsave(&s390_kernel_write_lock, flags);
  64         while (size) {
  65                 copied = s390_kernel_write_odd(dst, src, size);
  66                 dst += copied;
  67                 src += copied;
  68                 size -= copied;
  69         }
  70         spin_unlock_irqrestore(&s390_kernel_write_lock, flags);
  71 }
  72
  73 static int __no_sanitize_address __memcpy_real(void *dest, void *src, size_t count)
  74 {
  75         register unsigned long _dest asm("2") = (unsigned long) dest;
  76         register unsigned long _len1 asm("3") = (unsigned long) count;
  77         register unsigned long _src  asm("4") = (unsigned long) src;
  78         register unsigned long _len2 asm("5") = (unsigned long) count;
  79         int rc = -EFAULT;
  80
  81         asm volatile (
  82                 "0:     mvcle   %1,%2,0x0\n"
  83                 "1:     jo      0b\n"
  84                 "       lhi     %0,0x0\n"
  85                 "2:\n"
  86                 EX_TABLE(1b,2b)
  87                 : "+d" (rc), "+d" (_dest), "+d" (_src), "+d" (_len1),
  88                   "+d" (_len2), "=m" (*((long *) dest))
  89                 : "m" (*((long *) src))
  90                 : "cc", "memory");
  91         return rc;
  92 }
  93
  94 static unsigned long __no_sanitize_address _memcpy_real(unsigned long dest,
  95                                                         unsigned long src,
  96                                                         unsigned long count)
  97 {
  98         int irqs_disabled, rc;
  99         unsigned long flags;
 100
 101         if (!count)
 102                 return 0;
 103         flags = arch_local_irq_save();
 104         irqs_disabled = arch_irqs_disabled_flags(flags);
 105         if (!irqs_disabled)
 106                 trace_hardirqs_off();
 107         __arch_local_irq_stnsm(0xf8); // disable DAT
 108         rc = __memcpy_real((void *) dest, (void *) src, (size_t) count);
 109         if (flags & PSW_MASK_DAT)
 110                 __arch_local_irq_stosm(0x04); // enable DAT
 111         if (!irqs_disabled)
 112                 trace_hardirqs_on();
 113         __arch_local_irq_ssm(flags);
 114         return rc;
 115 }
 116
 117 /*
 118  * Copy memory in real mode (kernel to kernel)
 119  */
 120 int memcpy_real(void *dest, void *src, size_t count)
 121 {
 122         int rc;
 123
 124         if (S390_lowcore.nodat_stack != 0) {
 125                 preempt_disable();
 126                 rc = CALL_ON_STACK(_memcpy_real, S390_lowcore.nodat_stack, 3,
 127                                    dest, src, count);
 128                 preempt_enable();
 129                 return rc;
 130         }
 131         /*
 132          * This is a really early memcpy_real call, the stacks are
 133          * not set up yet. Just call _memcpy_real on the early boot
 134          * stack
 135          */
 136         return _memcpy_real((unsigned long) dest,(unsigned long) src,
 137                             (unsigned long) count);
 138 }
 139
 140 /*
 141  * Copy memory in absolute mode (kernel to kernel)
 142  */
 143 void memcpy_absolute(void *dest, void *src, size_t count)
 144 {
 145         unsigned long cr0, flags, prefix;
 146
 147         flags = arch_local_irq_save();
 148         __ctl_store(cr0, 0, 0);
 149         __ctl_clear_bit(0, 28); /* disable lowcore protection */
 150         prefix = store_prefix();
 151         if (prefix) {
 152                 local_mcck_disable();
 153                 set_prefix(0);
 154                 memcpy(dest, src, count);
 155                 set_prefix(prefix);
 156                 local_mcck_enable();
 157         } else {
 158                 memcpy(dest, src, count);
 159         }
 160         __ctl_load(cr0, 0, 0);
 161         arch_local_irq_restore(flags);
 162 }
 163
 164 /*
 165  * Copy memory from kernel (real) to user (virtual)
 166  */
 167 int copy_to_user_real(void __user *dest, void *src, unsigned long count)
 168 {
 169         int offs = 0, size, rc;
 170         char *buf;
 171
 172         buf = (char *) __get_free_page(GFP_KERNEL);
 173         if (!buf)
 174                 return -ENOMEM;
 175         rc = -EFAULT;
 176         while (offs < count) {
 177                 size = min(PAGE_SIZE, count - offs);
 178                 if (memcpy_real(buf, src + offs, size))
 179                         goto out;
 180                 if (copy_to_user(dest + offs, buf, size))
 181                         goto out;
 182                 offs += size;
 183         }
 184         rc = 0;
 185 out:
 186         free_page((unsigned long) buf);
 187         return rc;
 188 }
 189
 190 /*
 191  * Check if physical address is within prefix or zero page
 192  */
 193 static int is_swapped(unsigned long addr)
 194 {
 195         unsigned long lc;
 196         int cpu;
 197
 198         if (addr < sizeof(struct lowcore))
 199                 return 1;
 200         for_each_online_cpu(cpu) {
 201                 lc = (unsigned long) lowcore_ptr[cpu];
 202                 if (addr > lc + sizeof(struct lowcore) - 1 || addr < lc)
 203                         continue;
 204                 return 1;
 205         }
 206         return 0;
 207 }
 208
 209 /*
 210  * Convert a physical pointer for /dev/mem access
 211  *
 212  * For swapped prefix pages a new buffer is returned that contains a copy of
 213  * the absolute memory. The buffer size is maximum one page large.
 214  */
 215 void *xlate_dev_mem_ptr(phys_addr_t addr)
 216 {
 217         void *bounce = (void *) addr;
 218         unsigned long size;
 219
 220         get_online_cpus();
 221         preempt_disable();
 222         if (is_swapped(addr)) {
 223                 size = PAGE_SIZE - (addr & ~PAGE_MASK);
 224                 bounce = (void *) __get_free_page(GFP_ATOMIC);
 225                 if (bounce)
 226                         memcpy_absolute(bounce, (void *) addr, size);
 227         }
 228         preempt_enable();
 229         put_online_cpus();
 230         return bounce;
 231 }
 232
 233 /*
 234  * Free converted buffer for /dev/mem access (if necessary)
 235  */
 236 void unxlate_dev_mem_ptr(phys_addr_t addr, void *buf)
 237 {
 238         if ((void *) addr != buf)
 239                 free_page((unsigned long) buf);
 240 }