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 <linux/cpu.h>
16 #include <asm/ctl_reg.h>
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.
24 static long probe_kernel_write_odd(void *dst, const void *src, size_t size)
26 unsigned long count, aligned;
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;
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;
50 long probe_kernel_write(void *dst, const void *src, size_t size)
55 copied = probe_kernel_write_odd(dst, src, size);
62 return copied < 0 ? -EFAULT : 0;
65 static int __memcpy_real(void *dest, void *src, size_t count)
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;
74 "0: mvcle %1,%2,0x0\n"
79 : "+d" (rc), "+d" (_dest), "+d" (_src), "+d" (_len1),
80 "+d" (_len2), "=m" (*((long *) dest))
81 : "m" (*((long *) src))
87 * Copy memory in real mode (kernel to kernel)
89 int memcpy_real(void *dest, void *src, size_t count)
96 local_irq_save(flags);
97 __arch_local_irq_stnsm(0xfbUL);
98 rc = __memcpy_real(dest, src, count);
99 local_irq_restore(flags);
104 * Copy memory to absolute zero
106 void copy_to_absolute_zero(void *dest, void *src, size_t count)
110 BUG_ON((unsigned long) dest + count >= sizeof(struct _lowcore));
112 __ctl_store(cr0, 0, 0);
113 __ctl_clear_bit(0, 28); /* disable lowcore protection */
114 memcpy_real(dest + store_prefix(), src, count);
115 __ctl_load(cr0, 0, 0);
120 * Copy memory from kernel (real) to user (virtual)
122 int copy_to_user_real(void __user *dest, void *src, size_t count)
124 int offs = 0, size, rc;
127 buf = (char *) __get_free_page(GFP_KERNEL);
131 while (offs < count) {
132 size = min(PAGE_SIZE, count - offs);
133 if (memcpy_real(buf, src + offs, size))
135 if (copy_to_user(dest + offs, buf, size))
141 free_page((unsigned long) buf);
146 * Copy memory from user (virtual) to kernel (real)
148 int copy_from_user_real(void *dest, void __user *src, size_t count)
150 int offs = 0, size, rc;
153 buf = (char *) __get_free_page(GFP_KERNEL);
157 while (offs < count) {
158 size = min(PAGE_SIZE, count - offs);
159 if (copy_from_user(buf, src + offs, size))
161 if (memcpy_real(dest + offs, buf, size))
167 free_page((unsigned long) buf);
172 * Check if physical address is within prefix or zero page
174 static int is_swapped(unsigned long addr)
179 if (addr < sizeof(struct _lowcore))
181 for_each_online_cpu(cpu) {
182 lc = (unsigned long) lowcore_ptr[cpu];
183 if (addr > lc + sizeof(struct _lowcore) - 1 || addr < lc)
191 * Return swapped prefix or zero page address
193 static unsigned long get_swapped(unsigned long addr)
195 unsigned long prefix = store_prefix();
197 if (addr < sizeof(struct _lowcore))
198 return addr + prefix;
199 if (addr >= prefix && addr < prefix + sizeof(struct _lowcore))
200 return addr - prefix;
205 * Convert a physical pointer for /dev/mem access
207 * For swapped prefix pages a new buffer is returned that contains a copy of
208 * the absolute memory. The buffer size is maximum one page large.
210 void *xlate_dev_mem_ptr(unsigned long addr)
212 void *bounce = (void *) addr;
217 if (is_swapped(addr)) {
218 size = PAGE_SIZE - (addr & ~PAGE_MASK);
219 bounce = (void *) __get_free_page(GFP_ATOMIC);
221 memcpy_real(bounce, (void *) get_swapped(addr), size);
229 * Free converted buffer for /dev/mem access (if necessary)
231 void unxlate_dev_mem_ptr(unsigned long addr, void *buf)
233 if ((void *) addr != buf)
234 free_page((unsigned long) buf);