Linux 4.8-rc8
[linux/fpc-iii.git] / arch / s390 / mm / maccess.c
blob792f9c63fbca5b97e03d1251bfff1facc987f9c4
1 /*
2 * Access kernel memory without faulting -- s390 specific implementation.
4 * Copyright IBM Corp. 2009, 2015
6 * Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>,
8 */
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>
19 static notrace long s390_kernel_write_odd(void *dst, const void *src, size_t size)
21 unsigned long aligned, offset, count;
22 char tmp[8];
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;
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
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.
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.
58 void notrace s390_kernel_write(void *dst, const void *src, size_t size)
60 long copied;
62 while (size) {
63 copied = s390_kernel_write_odd(dst, src, size);
64 dst += copied;
65 src += copied;
66 size -= copied;
70 static int __memcpy_real(void *dest, void *src, size_t count)
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;
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;
92 * Copy memory in real mode (kernel to kernel)
94 int memcpy_real(void *dest, void *src, size_t count)
96 int irqs_disabled, rc;
97 unsigned long flags;
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;
113 * Copy memory in absolute mode (kernel to kernel)
115 void memcpy_absolute(void *dest, void *src, size_t count)
117 unsigned long cr0, flags, prefix;
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);
132 __ctl_load(cr0, 0, 0);
133 arch_local_irq_restore(flags);
137 * Copy memory from kernel (real) to user (virtual)
139 int copy_to_user_real(void __user *dest, void *src, unsigned long count)
141 int offs = 0, size, rc;
142 char *buf;
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;
156 rc = 0;
157 out:
158 free_page((unsigned long) buf);
159 return rc;
163 * Check if physical address is within prefix or zero page
165 static int is_swapped(unsigned long addr)
167 unsigned long lc;
168 int cpu;
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;
178 return 0;
182 * Convert a physical pointer for /dev/mem access
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.
187 void *xlate_dev_mem_ptr(phys_addr_t addr)
189 void *bounce = (void *) addr;
190 unsigned long size;
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);
200 preempt_enable();
201 put_online_cpus();
202 return bounce;
206 * Free converted buffer for /dev/mem access (if necessary)
208 void unxlate_dev_mem_ptr(phys_addr_t addr, void *buf)
210 if ((void *) addr != buf)
211 free_page((unsigned long) buf);