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
s390_kernel_write_odd(void * dst,const void * src,size_t size)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 */
s390_kernel_write(void * dst,const void * src,size_t size)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
__memcpy_real(void * dest,void * src,size_t count)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 */
memcpy_real(void * dest,void * src,size_t count)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 */
memcpy_absolute(void * dest,void * src,size_t count)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 */
copy_to_user_real(void __user * dest,void * src,unsigned long count)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 */
is_swapped(unsigned long addr)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 */
xlate_dev_mem_ptr(phys_addr_t addr)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 */
unxlate_dev_mem_ptr(phys_addr_t addr,void * buf)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 }
209