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 */
8
9 #include <linux/uaccess.h>
10 #include <linux/kernel.h>
11 #include <linux/types.h>
12 #include <linux/errno.h>
13 #include <linux/gfp.h>
14 #include <linux/cpu.h>
15 #include <linux/uio.h>
16 #include <asm/asm-extable.h>
17 #include <asm/ctl_reg.h>
18 #include <asm/io.h>
19 #include <asm/abs_lowcore.h>
20 #include <asm/stacktrace.h>
21 #include <asm/maccess.h>
22
23 unsigned long __bootdata_preserved(__memcpy_real_area);
24 static __ro_after_init pte_t *memcpy_real_ptep;
25 static DEFINE_MUTEX(memcpy_real_mutex);
26
s390_kernel_write_odd(void * dst,const void * src,size_t size)27 static notrace long s390_kernel_write_odd(void *dst, const void *src, size_t size)
28 {
29 unsigned long aligned, offset, count;
30 char tmp[8];
31
32 aligned = (unsigned long) dst & ~7UL;
33 offset = (unsigned long) dst & 7UL;
34 size = min(8UL - offset, size);
35 count = size - 1;
36 asm volatile(
37 " bras 1,0f\n"
38 " mvc 0(1,%4),0(%5)\n"
39 "0: mvc 0(8,%3),0(%0)\n"
40 " ex %1,0(1)\n"
41 " lg %1,0(%3)\n"
42 " lra %0,0(%0)\n"
43 " sturg %1,%0\n"
44 : "+&a" (aligned), "+&a" (count), "=m" (tmp)
45 : "a" (&tmp), "a" (&tmp[offset]), "a" (src)
46 : "cc", "memory", "1");
47 return size;
48 }
49
50 /*
51 * s390_kernel_write - write to kernel memory bypassing DAT
52 * @dst: destination address
53 * @src: source address
54 * @size: number of bytes to copy
55 *
56 * This function writes to kernel memory bypassing DAT and possible page table
57 * write protection. It writes to the destination using the sturg instruction.
58 * Therefore we have a read-modify-write sequence: the function reads eight
59 * bytes from destination at an eight byte boundary, modifies the bytes
60 * requested and writes the result back in a loop.
61 */
62 static DEFINE_SPINLOCK(s390_kernel_write_lock);
63
s390_kernel_write(void * dst,const void * src,size_t size)64 notrace void *s390_kernel_write(void *dst, const void *src, size_t size)
65 {
66 void *tmp = dst;
67 unsigned long flags;
68 long copied;
69
70 spin_lock_irqsave(&s390_kernel_write_lock, flags);
71 if (!(flags & PSW_MASK_DAT)) {
72 memcpy(dst, src, size);
73 } else {
74 while (size) {
75 copied = s390_kernel_write_odd(tmp, src, size);
76 tmp += copied;
77 src += copied;
78 size -= copied;
79 }
80 }
81 spin_unlock_irqrestore(&s390_kernel_write_lock, flags);
82
83 return dst;
84 }
85
memcpy_real_init(void)86 void __init memcpy_real_init(void)
87 {
88 memcpy_real_ptep = vmem_get_alloc_pte(__memcpy_real_area, true);
89 if (!memcpy_real_ptep)
90 panic("Couldn't setup memcpy real area");
91 }
92
memcpy_real_iter(struct iov_iter * iter,unsigned long src,size_t count)93 size_t memcpy_real_iter(struct iov_iter *iter, unsigned long src, size_t count)
94 {
95 size_t len, copied, res = 0;
96 unsigned long phys, offset;
97 void *chunk;
98 pte_t pte;
99
100 while (count) {
101 phys = src & PAGE_MASK;
102 offset = src & ~PAGE_MASK;
103 chunk = (void *)(__memcpy_real_area + offset);
104 len = min(count, PAGE_SIZE - offset);
105 pte = mk_pte_phys(phys, PAGE_KERNEL_RO);
106
107 mutex_lock(&memcpy_real_mutex);
108 if (pte_val(pte) != pte_val(*memcpy_real_ptep)) {
109 __ptep_ipte(__memcpy_real_area, memcpy_real_ptep, 0, 0, IPTE_GLOBAL);
110 set_pte(memcpy_real_ptep, pte);
111 }
112 copied = copy_to_iter(chunk, len, iter);
113 mutex_unlock(&memcpy_real_mutex);
114
115 count -= copied;
116 src += copied;
117 res += copied;
118 if (copied < len)
119 break;
120 }
121 return res;
122 }
123
memcpy_real(void * dest,unsigned long src,size_t count)124 int memcpy_real(void *dest, unsigned long src, size_t count)
125 {
126 struct iov_iter iter;
127 struct kvec kvec;
128
129 kvec.iov_base = dest;
130 kvec.iov_len = count;
131 iov_iter_kvec(&iter, WRITE, &kvec, 1, count);
132 if (memcpy_real_iter(&iter, src, count) < count)
133 return -EFAULT;
134 return 0;
135 }
136
137 /*
138 * Find CPU that owns swapped prefix page
139 */
get_swapped_owner(phys_addr_t addr)140 static int get_swapped_owner(phys_addr_t addr)
141 {
142 phys_addr_t lc;
143 int cpu;
144
145 for_each_online_cpu(cpu) {
146 lc = virt_to_phys(lowcore_ptr[cpu]);
147 if (addr > lc + sizeof(struct lowcore) - 1 || addr < lc)
148 continue;
149 return cpu;
150 }
151 return -1;
152 }
153
154 /*
155 * Convert a physical pointer for /dev/mem access
156 *
157 * For swapped prefix pages a new buffer is returned that contains a copy of
158 * the absolute memory. The buffer size is maximum one page large.
159 */
xlate_dev_mem_ptr(phys_addr_t addr)160 void *xlate_dev_mem_ptr(phys_addr_t addr)
161 {
162 void *ptr = phys_to_virt(addr);
163 void *bounce = ptr;
164 struct lowcore *abs_lc;
165 unsigned long flags;
166 unsigned long size;
167 int this_cpu, cpu;
168
169 cpus_read_lock();
170 this_cpu = get_cpu();
171 if (addr >= sizeof(struct lowcore)) {
172 cpu = get_swapped_owner(addr);
173 if (cpu < 0)
174 goto out;
175 }
176 bounce = (void *)__get_free_page(GFP_ATOMIC);
177 if (!bounce)
178 goto out;
179 size = PAGE_SIZE - (addr & ~PAGE_MASK);
180 if (addr < sizeof(struct lowcore)) {
181 abs_lc = get_abs_lowcore(&flags);
182 ptr = (void *)abs_lc + addr;
183 memcpy(bounce, ptr, size);
184 put_abs_lowcore(abs_lc, flags);
185 } else if (cpu == this_cpu) {
186 ptr = (void *)(addr - virt_to_phys(lowcore_ptr[cpu]));
187 memcpy(bounce, ptr, size);
188 } else {
189 memcpy(bounce, ptr, size);
190 }
191 out:
192 put_cpu();
193 cpus_read_unlock();
194 return bounce;
195 }
196
197 /*
198 * Free converted buffer for /dev/mem access (if necessary)
199 */
unxlate_dev_mem_ptr(phys_addr_t addr,void * ptr)200 void unxlate_dev_mem_ptr(phys_addr_t addr, void *ptr)
201 {
202 if (addr != virt_to_phys(ptr))
203 free_page((unsigned long)ptr);
204 }
205