Loading...
1/*
2 * Access kernel memory without faulting -- s390 specific implementation.
3 *
4 * Copyright IBM Corp. 2009, 2015
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#include <asm/io.h>
18
19static notrace long s390_kernel_write_odd(void *dst, const void *src, size_t size)
20{
21 unsigned long aligned, offset, count;
22 char tmp[8];
23
24 aligned = (unsigned long) dst & ~7UL;
25 offset = (unsigned long) dst & 7UL;
26 size = min(8UL - offset, size);
27 count = size - 1;
28 asm volatile(
29 " bras 1,0f\n"
30 " mvc 0(1,%4),0(%5)\n"
31 "0: mvc 0(8,%3),0(%0)\n"
32 " ex %1,0(1)\n"
33 " lg %1,0(%3)\n"
34 " lra %0,0(%0)\n"
35 " sturg %1,%0\n"
36 : "+&a" (aligned), "+&a" (count), "=m" (tmp)
37 : "a" (&tmp), "a" (&tmp[offset]), "a" (src)
38 : "cc", "memory", "1");
39 return size;
40}
41
42/*
43 * s390_kernel_write - write to kernel memory bypassing DAT
44 * @dst: destination address
45 * @src: source address
46 * @size: number of bytes to copy
47 *
48 * This function writes to kernel memory bypassing DAT and possible page table
49 * write protection. It writes to the destination using the sturg instruction.
50 * Therefore we have a read-modify-write sequence: the function reads eight
51 * bytes from destination at an eight byte boundary, modifies the bytes
52 * requested and writes the result back in a loop.
53 *
54 * Note: this means that this function may not be called concurrently on
55 * several cpus with overlapping words, since this may potentially
56 * cause data corruption.
57 */
58void notrace s390_kernel_write(void *dst, const void *src, size_t size)
59{
60 long copied;
61
62 while (size) {
63 copied = s390_kernel_write_odd(dst, src, size);
64 dst += copied;
65 src += copied;
66 size -= copied;
67 }
68}
69
70static int __memcpy_real(void *dest, void *src, size_t count)
71{
72 register unsigned long _dest asm("2") = (unsigned long) dest;
73 register unsigned long _len1 asm("3") = (unsigned long) count;
74 register unsigned long _src asm("4") = (unsigned long) src;
75 register unsigned long _len2 asm("5") = (unsigned long) count;
76 int rc = -EFAULT;
77
78 asm volatile (
79 "0: mvcle %1,%2,0x0\n"
80 "1: jo 0b\n"
81 " lhi %0,0x0\n"
82 "2:\n"
83 EX_TABLE(1b,2b)
84 : "+d" (rc), "+d" (_dest), "+d" (_src), "+d" (_len1),
85 "+d" (_len2), "=m" (*((long *) dest))
86 : "m" (*((long *) src))
87 : "cc", "memory");
88 return rc;
89}
90
91/*
92 * Copy memory in real mode (kernel to kernel)
93 */
94int memcpy_real(void *dest, void *src, size_t count)
95{
96 int irqs_disabled, rc;
97 unsigned long flags;
98
99 if (!count)
100 return 0;
101 flags = __arch_local_irq_stnsm(0xf8UL);
102 irqs_disabled = arch_irqs_disabled_flags(flags);
103 if (!irqs_disabled)
104 trace_hardirqs_off();
105 rc = __memcpy_real(dest, src, count);
106 if (!irqs_disabled)
107 trace_hardirqs_on();
108 __arch_local_irq_ssm(flags);
109 return rc;
110}
111
112/*
113 * Copy memory in absolute mode (kernel to kernel)
114 */
115void memcpy_absolute(void *dest, void *src, size_t count)
116{
117 unsigned long cr0, flags, prefix;
118
119 flags = arch_local_irq_save();
120 __ctl_store(cr0, 0, 0);
121 __ctl_clear_bit(0, 28); /* disable lowcore protection */
122 prefix = store_prefix();
123 if (prefix) {
124 local_mcck_disable();
125 set_prefix(0);
126 memcpy(dest, src, count);
127 set_prefix(prefix);
128 local_mcck_enable();
129 } else {
130 memcpy(dest, src, count);
131 }
132 __ctl_load(cr0, 0, 0);
133 arch_local_irq_restore(flags);
134}
135
136/*
137 * Copy memory from kernel (real) to user (virtual)
138 */
139int copy_to_user_real(void __user *dest, void *src, unsigned long count)
140{
141 int offs = 0, size, rc;
142 char *buf;
143
144 buf = (char *) __get_free_page(GFP_KERNEL);
145 if (!buf)
146 return -ENOMEM;
147 rc = -EFAULT;
148 while (offs < count) {
149 size = min(PAGE_SIZE, count - offs);
150 if (memcpy_real(buf, src + offs, size))
151 goto out;
152 if (copy_to_user(dest + offs, buf, size))
153 goto out;
154 offs += size;
155 }
156 rc = 0;
157out:
158 free_page((unsigned long) buf);
159 return rc;
160}
161
162/*
163 * Check if physical address is within prefix or zero page
164 */
165static int is_swapped(unsigned long addr)
166{
167 unsigned long lc;
168 int cpu;
169
170 if (addr < sizeof(struct lowcore))
171 return 1;
172 for_each_online_cpu(cpu) {
173 lc = (unsigned long) lowcore_ptr[cpu];
174 if (addr > lc + sizeof(struct lowcore) - 1 || addr < lc)
175 continue;
176 return 1;
177 }
178 return 0;
179}
180
181/*
182 * Convert a physical pointer for /dev/mem access
183 *
184 * For swapped prefix pages a new buffer is returned that contains a copy of
185 * the absolute memory. The buffer size is maximum one page large.
186 */
187void *xlate_dev_mem_ptr(phys_addr_t addr)
188{
189 void *bounce = (void *) addr;
190 unsigned long size;
191
192 get_online_cpus();
193 preempt_disable();
194 if (is_swapped(addr)) {
195 size = PAGE_SIZE - (addr & ~PAGE_MASK);
196 bounce = (void *) __get_free_page(GFP_ATOMIC);
197 if (bounce)
198 memcpy_absolute(bounce, (void *) addr, size);
199 }
200 preempt_enable();
201 put_online_cpus();
202 return bounce;
203}
204
205/*
206 * Free converted buffer for /dev/mem access (if necessary)
207 */
208void unxlate_dev_mem_ptr(phys_addr_t addr, void *buf)
209{
210 if ((void *) addr != buf)
211 free_page((unsigned long) buf);
212}
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/maccess.h>
21#include <asm/ctlreg.h>
22
23unsigned long __bootdata_preserved(__memcpy_real_area);
24pte_t *__bootdata_preserved(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 while (size) {
72 copied = s390_kernel_write_odd(tmp, src, size);
73 tmp += copied;
74 src += copied;
75 size -= copied;
76 }
77 spin_unlock_irqrestore(&s390_kernel_write_lock, flags);
78
79 return dst;
80}
81
82size_t memcpy_real_iter(struct iov_iter *iter, unsigned long src, size_t count)
83{
84 size_t len, copied, res = 0;
85 unsigned long phys, offset;
86 void *chunk;
87 pte_t pte;
88
89 BUILD_BUG_ON(MEMCPY_REAL_SIZE != PAGE_SIZE);
90 while (count) {
91 phys = src & MEMCPY_REAL_MASK;
92 offset = src & ~MEMCPY_REAL_MASK;
93 chunk = (void *)(__memcpy_real_area + offset);
94 len = min(count, MEMCPY_REAL_SIZE - offset);
95 pte = mk_pte_phys(phys, PAGE_KERNEL_RO);
96
97 mutex_lock(&memcpy_real_mutex);
98 if (pte_val(pte) != pte_val(*memcpy_real_ptep)) {
99 __ptep_ipte(__memcpy_real_area, memcpy_real_ptep, 0, 0, IPTE_GLOBAL);
100 set_pte(memcpy_real_ptep, pte);
101 }
102 copied = copy_to_iter(chunk, len, iter);
103 mutex_unlock(&memcpy_real_mutex);
104
105 count -= copied;
106 src += copied;
107 res += copied;
108 if (copied < len)
109 break;
110 }
111 return res;
112}
113
114int memcpy_real(void *dest, unsigned long src, size_t count)
115{
116 struct iov_iter iter;
117 struct kvec kvec;
118
119 kvec.iov_base = dest;
120 kvec.iov_len = count;
121 iov_iter_kvec(&iter, ITER_DEST, &kvec, 1, count);
122 if (memcpy_real_iter(&iter, src, count) < count)
123 return -EFAULT;
124 return 0;
125}
126
127/*
128 * Find CPU that owns swapped prefix page
129 */
130static int get_swapped_owner(phys_addr_t addr)
131{
132 phys_addr_t lc;
133 int cpu;
134
135 for_each_online_cpu(cpu) {
136 lc = virt_to_phys(lowcore_ptr[cpu]);
137 if (addr > lc + sizeof(struct lowcore) - 1 || addr < lc)
138 continue;
139 return cpu;
140 }
141 return -1;
142}
143
144/*
145 * Convert a physical pointer for /dev/mem access
146 *
147 * For swapped prefix pages a new buffer is returned that contains a copy of
148 * the absolute memory. The buffer size is maximum one page large.
149 */
150void *xlate_dev_mem_ptr(phys_addr_t addr)
151{
152 void *ptr = phys_to_virt(addr);
153 void *bounce = ptr;
154 struct lowcore *abs_lc;
155 unsigned long size;
156 int this_cpu, cpu;
157
158 cpus_read_lock();
159 this_cpu = get_cpu();
160 if (addr >= sizeof(struct lowcore)) {
161 cpu = get_swapped_owner(addr);
162 if (cpu < 0)
163 goto out;
164 }
165 bounce = (void *)__get_free_page(GFP_ATOMIC);
166 if (!bounce)
167 goto out;
168 size = PAGE_SIZE - (addr & ~PAGE_MASK);
169 if (addr < sizeof(struct lowcore)) {
170 abs_lc = get_abs_lowcore();
171 ptr = (void *)abs_lc + addr;
172 memcpy(bounce, ptr, size);
173 put_abs_lowcore(abs_lc);
174 } else if (cpu == this_cpu) {
175 ptr = (void *)(addr - virt_to_phys(lowcore_ptr[cpu]));
176 memcpy(bounce, ptr, size);
177 } else {
178 memcpy(bounce, ptr, size);
179 }
180out:
181 put_cpu();
182 cpus_read_unlock();
183 return bounce;
184}
185
186/*
187 * Free converted buffer for /dev/mem access (if necessary)
188 */
189void unxlate_dev_mem_ptr(phys_addr_t addr, void *ptr)
190{
191 if (addr != virt_to_phys(ptr))
192 free_page((unsigned long)ptr);
193}