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
s390_kernel_write_odd(void * dst,const void * src,size_t size)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
s390_kernel_write(void * dst,const void * src,size_t size)58 notrace void *s390_kernel_write(void *dst, const void *src, size_t size)
59 {
60 void *tmp = dst;
61 unsigned long flags;
62 long copied;
63
64 spin_lock_irqsave(&s390_kernel_write_lock, flags);
65 if (!(flags & PSW_MASK_DAT)) {
66 memcpy(dst, src, size);
67 } else {
68 while (size) {
69 copied = s390_kernel_write_odd(tmp, src, size);
70 tmp += copied;
71 src += copied;
72 size -= copied;
73 }
74 }
75 spin_unlock_irqrestore(&s390_kernel_write_lock, flags);
76
77 return dst;
78 }
79
__memcpy_real(void * dest,void * src,size_t count)80 static int __no_sanitize_address __memcpy_real(void *dest, void *src, size_t count)
81 {
82 register unsigned long _dest asm("2") = (unsigned long) dest;
83 register unsigned long _len1 asm("3") = (unsigned long) count;
84 register unsigned long _src asm("4") = (unsigned long) src;
85 register unsigned long _len2 asm("5") = (unsigned long) count;
86 int rc = -EFAULT;
87
88 asm volatile (
89 "0: mvcle %1,%2,0x0\n"
90 "1: jo 0b\n"
91 " lhi %0,0x0\n"
92 "2:\n"
93 EX_TABLE(1b,2b)
94 : "+d" (rc), "+d" (_dest), "+d" (_src), "+d" (_len1),
95 "+d" (_len2), "=m" (*((long *) dest))
96 : "m" (*((long *) src))
97 : "cc", "memory");
98 return rc;
99 }
100
_memcpy_real(unsigned long dest,unsigned long src,unsigned long count)101 static unsigned long __no_sanitize_address _memcpy_real(unsigned long dest,
102 unsigned long src,
103 unsigned long count)
104 {
105 int irqs_disabled, rc;
106 unsigned long flags;
107
108 if (!count)
109 return 0;
110 flags = arch_local_irq_save();
111 irqs_disabled = arch_irqs_disabled_flags(flags);
112 if (!irqs_disabled)
113 trace_hardirqs_off();
114 __arch_local_irq_stnsm(0xf8); // disable DAT
115 rc = __memcpy_real((void *) dest, (void *) src, (size_t) count);
116 if (flags & PSW_MASK_DAT)
117 __arch_local_irq_stosm(0x04); // enable DAT
118 if (!irqs_disabled)
119 trace_hardirqs_on();
120 __arch_local_irq_ssm(flags);
121 return rc;
122 }
123
124 /*
125 * Copy memory in real mode (kernel to kernel)
126 */
memcpy_real(void * dest,void * src,size_t count)127 int memcpy_real(void *dest, void *src, size_t count)
128 {
129 int rc;
130
131 if (S390_lowcore.nodat_stack != 0) {
132 preempt_disable();
133 rc = CALL_ON_STACK(_memcpy_real, S390_lowcore.nodat_stack, 3,
134 dest, src, count);
135 preempt_enable();
136 return rc;
137 }
138 /*
139 * This is a really early memcpy_real call, the stacks are
140 * not set up yet. Just call _memcpy_real on the early boot
141 * stack
142 */
143 return _memcpy_real((unsigned long) dest,(unsigned long) src,
144 (unsigned long) count);
145 }
146
147 /*
148 * Copy memory in absolute mode (kernel to kernel)
149 */
memcpy_absolute(void * dest,void * src,size_t count)150 void memcpy_absolute(void *dest, void *src, size_t count)
151 {
152 unsigned long cr0, flags, prefix;
153
154 flags = arch_local_irq_save();
155 __ctl_store(cr0, 0, 0);
156 __ctl_clear_bit(0, 28); /* disable lowcore protection */
157 prefix = store_prefix();
158 if (prefix) {
159 local_mcck_disable();
160 set_prefix(0);
161 memcpy(dest, src, count);
162 set_prefix(prefix);
163 local_mcck_enable();
164 } else {
165 memcpy(dest, src, count);
166 }
167 __ctl_load(cr0, 0, 0);
168 arch_local_irq_restore(flags);
169 }
170
171 /*
172 * Copy memory from kernel (real) to user (virtual)
173 */
copy_to_user_real(void __user * dest,void * src,unsigned long count)174 int copy_to_user_real(void __user *dest, void *src, unsigned long count)
175 {
176 int offs = 0, size, rc;
177 char *buf;
178
179 buf = (char *) __get_free_page(GFP_KERNEL);
180 if (!buf)
181 return -ENOMEM;
182 rc = -EFAULT;
183 while (offs < count) {
184 size = min(PAGE_SIZE, count - offs);
185 if (memcpy_real(buf, src + offs, size))
186 goto out;
187 if (copy_to_user(dest + offs, buf, size))
188 goto out;
189 offs += size;
190 }
191 rc = 0;
192 out:
193 free_page((unsigned long) buf);
194 return rc;
195 }
196
197 /*
198 * Check if physical address is within prefix or zero page
199 */
is_swapped(unsigned long addr)200 static int is_swapped(unsigned long addr)
201 {
202 unsigned long lc;
203 int cpu;
204
205 if (addr < sizeof(struct lowcore))
206 return 1;
207 for_each_online_cpu(cpu) {
208 lc = (unsigned long) lowcore_ptr[cpu];
209 if (addr > lc + sizeof(struct lowcore) - 1 || addr < lc)
210 continue;
211 return 1;
212 }
213 return 0;
214 }
215
216 /*
217 * Convert a physical pointer for /dev/mem access
218 *
219 * For swapped prefix pages a new buffer is returned that contains a copy of
220 * the absolute memory. The buffer size is maximum one page large.
221 */
xlate_dev_mem_ptr(phys_addr_t addr)222 void *xlate_dev_mem_ptr(phys_addr_t addr)
223 {
224 void *bounce = (void *) addr;
225 unsigned long size;
226
227 get_online_cpus();
228 preempt_disable();
229 if (is_swapped(addr)) {
230 size = PAGE_SIZE - (addr & ~PAGE_MASK);
231 bounce = (void *) __get_free_page(GFP_ATOMIC);
232 if (bounce)
233 memcpy_absolute(bounce, (void *) addr, size);
234 }
235 preempt_enable();
236 put_online_cpus();
237 return bounce;
238 }
239
240 /*
241 * Free converted buffer for /dev/mem access (if necessary)
242 */
unxlate_dev_mem_ptr(phys_addr_t addr,void * buf)243 void unxlate_dev_mem_ptr(phys_addr_t addr, void *buf)
244 {
245 if ((void *) addr != buf)
246 free_page((unsigned long) buf);
247 }
248