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Linux/arch/s390/mm/maccess.c

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  1 /*
  2  * Access kernel memory without faulting -- s390 specific implementation.
  3  *
  4  * Copyright IBM Corp. 2009
  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 /*
 20  * This function writes to kernel memory bypassing DAT and possible
 21  * write protection. It copies one to four bytes from src to dst
 22  * using the stura instruction.
 23  * Returns the number of bytes copied or -EFAULT.
 24  */
 25 static long probe_kernel_write_odd(void *dst, const void *src, size_t size)
 26 {
 27         unsigned long count, aligned;
 28         int offset, mask;
 29         int rc = -EFAULT;
 30 
 31         aligned = (unsigned long) dst & ~3UL;
 32         offset = (unsigned long) dst & 3;
 33         count = min_t(unsigned long, 4 - offset, size);
 34         mask = (0xf << (4 - count)) & 0xf;
 35         mask >>= offset;
 36         asm volatile(
 37                 "       bras    1,0f\n"
 38                 "       icm     0,0,0(%3)\n"
 39                 "0:     l       0,0(%1)\n"
 40                 "       lra     %1,0(%1)\n"
 41                 "1:     ex      %2,0(1)\n"
 42                 "2:     stura   0,%1\n"
 43                 "       la      %0,0\n"
 44                 "3:\n"
 45                 EX_TABLE(0b,3b) EX_TABLE(1b,3b) EX_TABLE(2b,3b)
 46                 : "+d" (rc), "+a" (aligned)
 47                 : "a" (mask), "a" (src) : "cc", "memory", "", "1");
 48         return rc ? rc : count;
 49 }
 50 
 51 long probe_kernel_write(void *dst, const void *src, size_t size)
 52 {
 53         long copied = 0;
 54 
 55         while (size) {
 56                 copied = probe_kernel_write_odd(dst, src, size);
 57                 if (copied < 0)
 58                         break;
 59                 dst += copied;
 60                 src += copied;
 61                 size -= copied;
 62         }
 63         return copied < 0 ? -EFAULT : 0;
 64 }
 65 
 66 static int __memcpy_real(void *dest, void *src, size_t count)
 67 {
 68         register unsigned long _dest asm("2") = (unsigned long) dest;
 69         register unsigned long _len1 asm("3") = (unsigned long) count;
 70         register unsigned long _src  asm("4") = (unsigned long) src;
 71         register unsigned long _len2 asm("5") = (unsigned long) count;
 72         int rc = -EFAULT;
 73 
 74         asm volatile (
 75                 "0:     mvcle   %1,%2,0x0\n"
 76                 "1:     jo      0b\n"
 77                 "       lhi     %0,0x0\n"
 78                 "2:\n"
 79                 EX_TABLE(1b,2b)
 80                 : "+d" (rc), "+d" (_dest), "+d" (_src), "+d" (_len1),
 81                   "+d" (_len2), "=m" (*((long *) dest))
 82                 : "m" (*((long *) src))
 83                 : "cc", "memory");
 84         return rc;
 85 }
 86 
 87 /*
 88  * Copy memory in real mode (kernel to kernel)
 89  */
 90 int memcpy_real(void *dest, void *src, size_t count)
 91 {
 92         unsigned long flags;
 93         int rc;
 94 
 95         if (!count)
 96                 return 0;
 97         local_irq_save(flags);
 98         __arch_local_irq_stnsm(0xfbUL);
 99         rc = __memcpy_real(dest, src, count);
100         local_irq_restore(flags);
101         return rc;
102 }
103 
104 /*
105  * Copy memory in absolute mode (kernel to kernel)
106  */
107 void memcpy_absolute(void *dest, void *src, size_t count)
108 {
109         unsigned long cr0, flags, prefix;
110 
111         flags = arch_local_irq_save();
112         __ctl_store(cr0, 0, 0);
113         __ctl_clear_bit(0, 28); /* disable lowcore protection */
114         prefix = store_prefix();
115         if (prefix) {
116                 local_mcck_disable();
117                 set_prefix(0);
118                 memcpy(dest, src, count);
119                 set_prefix(prefix);
120                 local_mcck_enable();
121         } else {
122                 memcpy(dest, src, count);
123         }
124         __ctl_load(cr0, 0, 0);
125         arch_local_irq_restore(flags);
126 }
127 
128 /*
129  * Copy memory from kernel (real) to user (virtual)
130  */
131 int copy_to_user_real(void __user *dest, void *src, unsigned long count)
132 {
133         int offs = 0, size, rc;
134         char *buf;
135 
136         buf = (char *) __get_free_page(GFP_KERNEL);
137         if (!buf)
138                 return -ENOMEM;
139         rc = -EFAULT;
140         while (offs < count) {
141                 size = min(PAGE_SIZE, count - offs);
142                 if (memcpy_real(buf, src + offs, size))
143                         goto out;
144                 if (copy_to_user(dest + offs, buf, size))
145                         goto out;
146                 offs += size;
147         }
148         rc = 0;
149 out:
150         free_page((unsigned long) buf);
151         return rc;
152 }
153 
154 /*
155  * Check if physical address is within prefix or zero page
156  */
157 static int is_swapped(unsigned long addr)
158 {
159         unsigned long lc;
160         int cpu;
161 
162         if (addr < sizeof(struct _lowcore))
163                 return 1;
164         for_each_online_cpu(cpu) {
165                 lc = (unsigned long) lowcore_ptr[cpu];
166                 if (addr > lc + sizeof(struct _lowcore) - 1 || addr < lc)
167                         continue;
168                 return 1;
169         }
170         return 0;
171 }
172 
173 /*
174  * Convert a physical pointer for /dev/mem access
175  *
176  * For swapped prefix pages a new buffer is returned that contains a copy of
177  * the absolute memory. The buffer size is maximum one page large.
178  */
179 void *xlate_dev_mem_ptr(unsigned long addr)
180 {
181         void *bounce = (void *) addr;
182         unsigned long size;
183 
184         get_online_cpus();
185         preempt_disable();
186         if (is_swapped(addr)) {
187                 size = PAGE_SIZE - (addr & ~PAGE_MASK);
188                 bounce = (void *) __get_free_page(GFP_ATOMIC);
189                 if (bounce)
190                         memcpy_absolute(bounce, (void *) addr, size);
191         }
192         preempt_enable();
193         put_online_cpus();
194         return bounce;
195 }
196 
197 /*
198  * Free converted buffer for /dev/mem access (if necessary)
199  */
200 void unxlate_dev_mem_ptr(unsigned long addr, void *buf)
201 {
202         if ((void *) addr != buf)
203                 free_page((unsigned long) buf);
204 }
205 

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