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 <linux/io.h>
17 #include <asm/asm-extable.h>
18 #include <asm/abs_lowcore.h>
19 #include <asm/stacktrace.h>
20 #include <asm/sections.h>
21 #include <asm/maccess.h>
22 #include <asm/ctlreg.h>
23
24 unsigned long __bootdata_preserved(__memcpy_real_area);
25 pte_t *__bootdata_preserved(memcpy_real_ptep);
26 static DEFINE_MUTEX(memcpy_real_mutex);
27
s390_kernel_write_odd(void * dst,const void * src,size_t size)28 static notrace long s390_kernel_write_odd(void *dst, const void *src, size_t size)
29 {
30 unsigned long aligned, offset, count;
31 char tmp[8];
32
33 aligned = (unsigned long) dst & ~7UL;
34 offset = (unsigned long) dst & 7UL;
35 size = min(8UL - offset, size);
36 count = size - 1;
37 asm volatile(
38 " bras 1,0f\n"
39 " mvc 0(1,%4),0(%5)\n"
40 "0: mvc 0(8,%3),0(%0)\n"
41 " ex %1,0(1)\n"
42 " lg %1,0(%3)\n"
43 " lra %0,0(%0)\n"
44 " sturg %1,%0\n"
45 : "+&a" (aligned), "+&a" (count), "=m" (tmp)
46 : "a" (&tmp), "a" (&tmp[offset]), "a" (src)
47 : "cc", "memory", "1");
48 return size;
49 }
50
51 /*
52 * __s390_kernel_write - write to kernel memory bypassing DAT
53 * @dst: destination address
54 * @src: source address
55 * @size: number of bytes to copy
56 *
57 * This function writes to kernel memory bypassing DAT and possible page table
58 * write protection. It writes to the destination using the sturg instruction.
59 * Therefore we have a read-modify-write sequence: the function reads eight
60 * bytes from destination at an eight byte boundary, modifies the bytes
61 * requested and writes the result back in a loop.
62 */
63 static DEFINE_SPINLOCK(s390_kernel_write_lock);
64
__s390_kernel_write(void * dst,const void * src,size_t size)65 notrace void *__s390_kernel_write(void *dst, const void *src, size_t size)
66 {
67 void *tmp = dst;
68 unsigned long flags;
69 long copied;
70
71 spin_lock_irqsave(&s390_kernel_write_lock, flags);
72 while (size) {
73 copied = s390_kernel_write_odd(tmp, src, size);
74 tmp += copied;
75 src += copied;
76 size -= copied;
77 }
78 spin_unlock_irqrestore(&s390_kernel_write_lock, flags);
79
80 return dst;
81 }
82
memcpy_real_iter(struct iov_iter * iter,unsigned long src,size_t count)83 size_t memcpy_real_iter(struct iov_iter *iter, unsigned long src, size_t count)
84 {
85 size_t len, copied, res = 0;
86 unsigned long phys, offset;
87 void *chunk;
88 pte_t pte;
89
90 BUILD_BUG_ON(MEMCPY_REAL_SIZE != PAGE_SIZE);
91 while (count) {
92 phys = src & MEMCPY_REAL_MASK;
93 offset = src & ~MEMCPY_REAL_MASK;
94 chunk = (void *)(__memcpy_real_area + offset);
95 len = min(count, MEMCPY_REAL_SIZE - offset);
96 pte = mk_pte_phys(phys, PAGE_KERNEL_RO);
97
98 mutex_lock(&memcpy_real_mutex);
99 if (pte_val(pte) != pte_val(*memcpy_real_ptep)) {
100 __ptep_ipte(__memcpy_real_area, memcpy_real_ptep, 0, 0, IPTE_GLOBAL);
101 set_pte(memcpy_real_ptep, pte);
102 }
103 copied = copy_to_iter(chunk, len, iter);
104 mutex_unlock(&memcpy_real_mutex);
105
106 count -= copied;
107 src += copied;
108 res += copied;
109 if (copied < len)
110 break;
111 }
112 return res;
113 }
114
memcpy_real(void * dest,unsigned long src,size_t count)115 int memcpy_real(void *dest, unsigned long src, size_t count)
116 {
117 struct iov_iter iter;
118 struct kvec kvec;
119
120 kvec.iov_base = dest;
121 kvec.iov_len = count;
122 iov_iter_kvec(&iter, ITER_DEST, &kvec, 1, count);
123 if (memcpy_real_iter(&iter, src, count) < count)
124 return -EFAULT;
125 return 0;
126 }
127
128 /*
129 * Find CPU that owns swapped prefix page
130 */
get_swapped_owner(phys_addr_t addr)131 static int get_swapped_owner(phys_addr_t addr)
132 {
133 phys_addr_t lc;
134 int cpu;
135
136 for_each_online_cpu(cpu) {
137 lc = virt_to_phys(lowcore_ptr[cpu]);
138 if (addr > lc + sizeof(struct lowcore) - 1 || addr < lc)
139 continue;
140 return cpu;
141 }
142 return -1;
143 }
144
145 /*
146 * Convert a physical pointer for /dev/mem access
147 *
148 * For swapped prefix pages a new buffer is returned that contains a copy of
149 * the absolute memory. The buffer size is maximum one page large.
150 */
xlate_dev_mem_ptr(phys_addr_t addr)151 void *xlate_dev_mem_ptr(phys_addr_t addr)
152 {
153 void *ptr = phys_to_virt(addr);
154 void *bounce = ptr;
155 struct lowcore *abs_lc;
156 unsigned long size;
157 int this_cpu, cpu;
158
159 cpus_read_lock();
160 this_cpu = get_cpu();
161 if (addr >= sizeof(struct lowcore)) {
162 cpu = get_swapped_owner(addr);
163 if (cpu < 0)
164 goto out;
165 }
166 bounce = (void *)__get_free_page(GFP_ATOMIC);
167 if (!bounce)
168 goto out;
169 size = PAGE_SIZE - (addr & ~PAGE_MASK);
170 if (addr < sizeof(struct lowcore)) {
171 abs_lc = get_abs_lowcore();
172 ptr = (void *)abs_lc + addr;
173 memcpy(bounce, ptr, size);
174 put_abs_lowcore(abs_lc);
175 } else if (cpu == this_cpu) {
176 ptr = (void *)(addr - virt_to_phys(lowcore_ptr[cpu]));
177 memcpy(bounce, ptr, size);
178 } else {
179 memcpy(bounce, ptr, size);
180 }
181 out:
182 put_cpu();
183 cpus_read_unlock();
184 return bounce;
185 }
186
187 /*
188 * Free converted buffer for /dev/mem access (if necessary)
189 */
unxlate_dev_mem_ptr(phys_addr_t addr,void * ptr)190 void unxlate_dev_mem_ptr(phys_addr_t addr, void *ptr)
191 {
192 if (addr != virt_to_phys(ptr))
193 free_page((unsigned long)ptr);
194 }
195