2 * Access kernel memory without faulting -- s390 specific implementation.
4 * Copyright IBM Corp. 2009
6 * Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>,
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 <asm/ctl_reg.h>
18 * This function writes to kernel memory bypassing DAT and possible
19 * write protection. It copies one to four bytes from src to dst
20 * using the stura instruction.
21 * Returns the number of bytes copied or -EFAULT.
23 static long probe_kernel_write_odd(void *dst, const void *src, size_t size)
25 unsigned long count, aligned;
29 aligned = (unsigned long) dst & ~3UL;
30 offset = (unsigned long) dst & 3;
31 count = min_t(unsigned long, 4 - offset, size);
32 mask = (0xf << (4 - count)) & 0xf;
43 EX_TABLE(0b,3b) EX_TABLE(1b,3b) EX_TABLE(2b,3b)
44 : "+d" (rc), "+a" (aligned)
45 : "a" (mask), "a" (src) : "cc", "memory", "0", "1");
46 return rc ? rc : count;
49 long probe_kernel_write(void *dst, const void *src, size_t size)
54 copied = probe_kernel_write_odd(dst, src, size);
61 return copied < 0 ? -EFAULT : 0;
64 static int __memcpy_real(void *dest, void *src, size_t count)
66 register unsigned long _dest asm("2") = (unsigned long) dest;
67 register unsigned long _len1 asm("3") = (unsigned long) count;
68 register unsigned long _src asm("4") = (unsigned long) src;
69 register unsigned long _len2 asm("5") = (unsigned long) count;
73 "0: mvcle %1,%2,0x0\n"
78 : "+d" (rc), "+d" (_dest), "+d" (_src), "+d" (_len1),
79 "+d" (_len2), "=m" (*((long *) dest))
80 : "m" (*((long *) src))
86 * Copy memory in real mode (kernel to kernel)
88 int memcpy_real(void *dest, void *src, size_t count)
95 local_irq_save(flags);
96 __arch_local_irq_stnsm(0xfbUL);
97 rc = __memcpy_real(dest, src, count);
98 local_irq_restore(flags);
103 * Copy memory to absolute zero
105 void copy_to_absolute_zero(void *dest, void *src, size_t count)
109 BUG_ON((unsigned long) dest + count >= sizeof(struct _lowcore));
111 __ctl_store(cr0, 0, 0);
112 __ctl_clear_bit(0, 28); /* disable lowcore protection */
113 memcpy_real(dest + store_prefix(), src, count);
114 __ctl_load(cr0, 0, 0);
119 * Copy memory from kernel (real) to user (virtual)
121 int copy_to_user_real(void __user *dest, void *src, size_t count)
123 int offs = 0, size, rc;
126 buf = (char *) __get_free_page(GFP_KERNEL);
130 while (offs < count) {
131 size = min(PAGE_SIZE, count - offs);
132 if (memcpy_real(buf, src + offs, size))
134 if (copy_to_user(dest + offs, buf, size))
140 free_page((unsigned long) buf);
145 * Copy memory from user (virtual) to kernel (real)
147 int copy_from_user_real(void *dest, void __user *src, size_t count)
149 int offs = 0, size, rc;
152 buf = (char *) __get_free_page(GFP_KERNEL);
156 while (offs < count) {
157 size = min(PAGE_SIZE, count - offs);
158 if (copy_from_user(buf, src + offs, size))
160 if (memcpy_real(dest + offs, buf, size))
166 free_page((unsigned long) buf);