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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// 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
20static notrace long s390_kernel_write_odd(void *dst, const void *src, size_t size)
21{
22 unsigned long aligned, offset, count;
23 char tmp[8];
24
25 aligned = (unsigned long) dst & ~7UL;
26 offset = (unsigned long) dst & 7UL;
27 size = min(8UL - offset, size);
28 count = size - 1;
29 asm volatile(
30 " bras 1,0f\n"
31 " mvc 0(1,%4),0(%5)\n"
32 "0: mvc 0(8,%3),0(%0)\n"
33 " ex %1,0(1)\n"
34 " lg %1,0(%3)\n"
35 " lra %0,0(%0)\n"
36 " sturg %1,%0\n"
37 : "+&a" (aligned), "+&a" (count), "=m" (tmp)
38 : "a" (&tmp), "a" (&tmp[offset]), "a" (src)
39 : "cc", "memory", "1");
40 return size;
41}
42
43/*
44 * s390_kernel_write - write to kernel memory bypassing DAT
45 * @dst: destination address
46 * @src: source address
47 * @size: number of bytes to copy
48 *
49 * This function writes to kernel memory bypassing DAT and possible page table
50 * write protection. It writes to the destination using the sturg instruction.
51 * Therefore we have a read-modify-write sequence: the function reads eight
52 * bytes from destination at an eight byte boundary, modifies the bytes
53 * requested and writes the result back in a loop.
54 *
55 * Note: this means that this function may not be called concurrently on
56 * several cpus with overlapping words, since this may potentially
57 * cause data corruption.
58 */
59void notrace s390_kernel_write(void *dst, const void *src, size_t size)
60{
61 long copied;
62
63 while (size) {
64 copied = s390_kernel_write_odd(dst, src, size);
65 dst += copied;
66 src += copied;
67 size -= copied;
68 }
69}
70
71static int __memcpy_real(void *dest, void *src, size_t count)
72{
73 register unsigned long _dest asm("2") = (unsigned long) dest;
74 register unsigned long _len1 asm("3") = (unsigned long) count;
75 register unsigned long _src asm("4") = (unsigned long) src;
76 register unsigned long _len2 asm("5") = (unsigned long) count;
77 int rc = -EFAULT;
78
79 asm volatile (
80 "0: mvcle %1,%2,0x0\n"
81 "1: jo 0b\n"
82 " lhi %0,0x0\n"
83 "2:\n"
84 EX_TABLE(1b,2b)
85 : "+d" (rc), "+d" (_dest), "+d" (_src), "+d" (_len1),
86 "+d" (_len2), "=m" (*((long *) dest))
87 : "m" (*((long *) src))
88 : "cc", "memory");
89 return rc;
90}
91
92/*
93 * Copy memory in real mode (kernel to kernel)
94 */
95int memcpy_real(void *dest, void *src, size_t count)
96{
97 int irqs_disabled, rc;
98 unsigned long flags;
99
100 if (!count)
101 return 0;
102 flags = __arch_local_irq_stnsm(0xf8UL);
103 irqs_disabled = arch_irqs_disabled_flags(flags);
104 if (!irqs_disabled)
105 trace_hardirqs_off();
106 rc = __memcpy_real(dest, src, count);
107 if (!irqs_disabled)
108 trace_hardirqs_on();
109 __arch_local_irq_ssm(flags);
110 return rc;
111}
112
113/*
114 * Copy memory in absolute mode (kernel to kernel)
115 */
116void memcpy_absolute(void *dest, void *src, size_t count)
117{
118 unsigned long cr0, flags, prefix;
119
120 flags = arch_local_irq_save();
121 __ctl_store(cr0, 0, 0);
122 __ctl_clear_bit(0, 28); /* disable lowcore protection */
123 prefix = store_prefix();
124 if (prefix) {
125 local_mcck_disable();
126 set_prefix(0);
127 memcpy(dest, src, count);
128 set_prefix(prefix);
129 local_mcck_enable();
130 } else {
131 memcpy(dest, src, count);
132 }
133 __ctl_load(cr0, 0, 0);
134 arch_local_irq_restore(flags);
135}
136
137/*
138 * Copy memory from kernel (real) to user (virtual)
139 */
140int copy_to_user_real(void __user *dest, void *src, unsigned long count)
141{
142 int offs = 0, size, rc;
143 char *buf;
144
145 buf = (char *) __get_free_page(GFP_KERNEL);
146 if (!buf)
147 return -ENOMEM;
148 rc = -EFAULT;
149 while (offs < count) {
150 size = min(PAGE_SIZE, count - offs);
151 if (memcpy_real(buf, src + offs, size))
152 goto out;
153 if (copy_to_user(dest + offs, buf, size))
154 goto out;
155 offs += size;
156 }
157 rc = 0;
158out:
159 free_page((unsigned long) buf);
160 return rc;
161}
162
163/*
164 * Check if physical address is within prefix or zero page
165 */
166static int is_swapped(unsigned long addr)
167{
168 unsigned long lc;
169 int cpu;
170
171 if (addr < sizeof(struct lowcore))
172 return 1;
173 for_each_online_cpu(cpu) {
174 lc = (unsigned long) lowcore_ptr[cpu];
175 if (addr > lc + sizeof(struct lowcore) - 1 || addr < lc)
176 continue;
177 return 1;
178 }
179 return 0;
180}
181
182/*
183 * Convert a physical pointer for /dev/mem access
184 *
185 * For swapped prefix pages a new buffer is returned that contains a copy of
186 * the absolute memory. The buffer size is maximum one page large.
187 */
188void *xlate_dev_mem_ptr(phys_addr_t addr)
189{
190 void *bounce = (void *) addr;
191 unsigned long size;
192
193 get_online_cpus();
194 preempt_disable();
195 if (is_swapped(addr)) {
196 size = PAGE_SIZE - (addr & ~PAGE_MASK);
197 bounce = (void *) __get_free_page(GFP_ATOMIC);
198 if (bounce)
199 memcpy_absolute(bounce, (void *) addr, size);
200 }
201 preempt_enable();
202 put_online_cpus();
203 return bounce;
204}
205
206/*
207 * Free converted buffer for /dev/mem access (if necessary)
208 */
209void unxlate_dev_mem_ptr(phys_addr_t addr, void *buf)
210{
211 if ((void *) addr != buf)
212 free_page((unsigned long) buf);
213}