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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
23unsigned long __bootdata_preserved(__memcpy_real_area);
24static __ro_after_init pte_t *memcpy_real_ptep;
25static DEFINE_MUTEX(memcpy_real_mutex);
26
27static 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 */
62static DEFINE_SPINLOCK(s390_kernel_write_lock);
63
64notrace 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
86void __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
93size_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
124int 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, ITER_DEST, &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 */
140static 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 */
160void *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 }
191out:
192 put_cpu();
193 cpus_read_unlock();
194 return bounce;
195}
196
197/*
198 * Free converted buffer for /dev/mem access (if necessary)
199 */
200void 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}
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
18/*
19 * This function writes to kernel memory bypassing DAT and possible
20 * write protection. It copies one to four bytes from src to dst
21 * using the stura instruction.
22 * Returns the number of bytes copied or -EFAULT.
23 */
24static long probe_kernel_write_odd(void *dst, const void *src, size_t size)
25{
26 unsigned long count, aligned;
27 int offset, mask;
28 int rc = -EFAULT;
29
30 aligned = (unsigned long) dst & ~3UL;
31 offset = (unsigned long) dst & 3;
32 count = min_t(unsigned long, 4 - offset, size);
33 mask = (0xf << (4 - count)) & 0xf;
34 mask >>= offset;
35 asm volatile(
36 " bras 1,0f\n"
37 " icm 0,0,0(%3)\n"
38 "0: l 0,0(%1)\n"
39 " lra %1,0(%1)\n"
40 "1: ex %2,0(1)\n"
41 "2: stura 0,%1\n"
42 " la %0,0\n"
43 "3:\n"
44 EX_TABLE(0b,3b) EX_TABLE(1b,3b) EX_TABLE(2b,3b)
45 : "+d" (rc), "+a" (aligned)
46 : "a" (mask), "a" (src) : "cc", "memory", "0", "1");
47 return rc ? rc : count;
48}
49
50long probe_kernel_write(void *dst, const void *src, size_t size)
51{
52 long copied = 0;
53
54 while (size) {
55 copied = probe_kernel_write_odd(dst, src, size);
56 if (copied < 0)
57 break;
58 dst += copied;
59 src += copied;
60 size -= copied;
61 }
62 return copied < 0 ? -EFAULT : 0;
63}
64
65static int __memcpy_real(void *dest, void *src, size_t count)
66{
67 register unsigned long _dest asm("2") = (unsigned long) dest;
68 register unsigned long _len1 asm("3") = (unsigned long) count;
69 register unsigned long _src asm("4") = (unsigned long) src;
70 register unsigned long _len2 asm("5") = (unsigned long) count;
71 int rc = -EFAULT;
72
73 asm volatile (
74 "0: mvcle %1,%2,0x0\n"
75 "1: jo 0b\n"
76 " lhi %0,0x0\n"
77 "2:\n"
78 EX_TABLE(1b,2b)
79 : "+d" (rc), "+d" (_dest), "+d" (_src), "+d" (_len1),
80 "+d" (_len2), "=m" (*((long *) dest))
81 : "m" (*((long *) src))
82 : "cc", "memory");
83 return rc;
84}
85
86/*
87 * Copy memory in real mode (kernel to kernel)
88 */
89int memcpy_real(void *dest, void *src, size_t count)
90{
91 unsigned long flags;
92 int rc;
93
94 if (!count)
95 return 0;
96 local_irq_save(flags);
97 __arch_local_irq_stnsm(0xfbUL);
98 rc = __memcpy_real(dest, src, count);
99 local_irq_restore(flags);
100 return rc;
101}
102
103/*
104 * Copy memory in absolute mode (kernel to kernel)
105 */
106void memcpy_absolute(void *dest, void *src, size_t count)
107{
108 unsigned long cr0, flags, prefix;
109
110 flags = arch_local_irq_save();
111 __ctl_store(cr0, 0, 0);
112 __ctl_clear_bit(0, 28); /* disable lowcore protection */
113 prefix = store_prefix();
114 if (prefix) {
115 local_mcck_disable();
116 set_prefix(0);
117 memcpy(dest, src, count);
118 set_prefix(prefix);
119 local_mcck_enable();
120 } else {
121 memcpy(dest, src, count);
122 }
123 __ctl_load(cr0, 0, 0);
124 arch_local_irq_restore(flags);
125}
126
127/*
128 * Copy memory from kernel (real) to user (virtual)
129 */
130int copy_to_user_real(void __user *dest, void *src, size_t count)
131{
132 int offs = 0, size, rc;
133 char *buf;
134
135 buf = (char *) __get_free_page(GFP_KERNEL);
136 if (!buf)
137 return -ENOMEM;
138 rc = -EFAULT;
139 while (offs < count) {
140 size = min(PAGE_SIZE, count - offs);
141 if (memcpy_real(buf, src + offs, size))
142 goto out;
143 if (copy_to_user(dest + offs, buf, size))
144 goto out;
145 offs += size;
146 }
147 rc = 0;
148out:
149 free_page((unsigned long) buf);
150 return rc;
151}
152
153/*
154 * Copy memory from user (virtual) to kernel (real)
155 */
156int copy_from_user_real(void *dest, void __user *src, size_t count)
157{
158 int offs = 0, size, rc;
159 char *buf;
160
161 buf = (char *) __get_free_page(GFP_KERNEL);
162 if (!buf)
163 return -ENOMEM;
164 rc = -EFAULT;
165 while (offs < count) {
166 size = min(PAGE_SIZE, count - offs);
167 if (copy_from_user(buf, src + offs, size))
168 goto out;
169 if (memcpy_real(dest + offs, buf, size))
170 goto out;
171 offs += size;
172 }
173 rc = 0;
174out:
175 free_page((unsigned long) buf);
176 return rc;
177}
178
179/*
180 * Check if physical address is within prefix or zero page
181 */
182static int is_swapped(unsigned long addr)
183{
184 unsigned long lc;
185 int cpu;
186
187 if (addr < sizeof(struct _lowcore))
188 return 1;
189 for_each_online_cpu(cpu) {
190 lc = (unsigned long) lowcore_ptr[cpu];
191 if (addr > lc + sizeof(struct _lowcore) - 1 || addr < lc)
192 continue;
193 return 1;
194 }
195 return 0;
196}
197
198/*
199 * Convert a physical pointer for /dev/mem access
200 *
201 * For swapped prefix pages a new buffer is returned that contains a copy of
202 * the absolute memory. The buffer size is maximum one page large.
203 */
204void *xlate_dev_mem_ptr(unsigned long addr)
205{
206 void *bounce = (void *) addr;
207 unsigned long size;
208
209 get_online_cpus();
210 preempt_disable();
211 if (is_swapped(addr)) {
212 size = PAGE_SIZE - (addr & ~PAGE_MASK);
213 bounce = (void *) __get_free_page(GFP_ATOMIC);
214 if (bounce)
215 memcpy_absolute(bounce, (void *) addr, size);
216 }
217 preempt_enable();
218 put_online_cpus();
219 return bounce;
220}
221
222/*
223 * Free converted buffer for /dev/mem access (if necessary)
224 */
225void unxlate_dev_mem_ptr(unsigned long addr, void *buf)
226{
227 if ((void *) addr != buf)
228 free_page((unsigned long) buf);
229}