1 /* 2 * Access kernel memory without faulting -- s390 specific implementation. 3 * 4 * Copyright IBM Corp. 2009 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 19 /* 20 * This function writes to kernel memory bypassing DAT and possible 21 * write protection. It copies one to four bytes from src to dst 22 * using the stura instruction. 23 * Returns the number of bytes copied or -EFAULT. 24 */ 25 static long probe_kernel_write_odd(void *dst, const void *src, size_t size) 26 { 27 unsigned long count, aligned; 28 int offset, mask; 29 int rc = -EFAULT; 30 31 aligned = (unsigned long) dst & ~3UL; 32 offset = (unsigned long) dst & 3; 33 count = min_t(unsigned long, 4 - offset, size); 34 mask = (0xf << (4 - count)) & 0xf; 35 mask >>= offset; 36 asm volatile( 37 " bras 1,0f\n" 38 " icm 0,0,0(%3)\n" 39 "0: l 0,0(%1)\n" 40 " lra %1,0(%1)\n" 41 "1: ex %2,0(1)\n" 42 "2: stura 0,%1\n" 43 " la %0,0\n" 44 "3:\n" 45 EX_TABLE(0b,3b) EX_TABLE(1b,3b) EX_TABLE(2b,3b) 46 : "+d" (rc), "+a" (aligned) 47 : "a" (mask), "a" (src) : "cc", "memory", "0", "1"); 48 return rc ? rc : count; 49 } 50 51 long probe_kernel_write(void *dst, const void *src, size_t size) 52 { 53 long copied = 0; 54 55 while (size) { 56 copied = probe_kernel_write_odd(dst, src, size); 57 if (copied < 0) 58 break; 59 dst += copied; 60 src += copied; 61 size -= copied; 62 } 63 return copied < 0 ? -EFAULT : 0; 64 } 65 66 static int __memcpy_real(void *dest, void *src, size_t count) 67 { 68 register unsigned long _dest asm("2") = (unsigned long) dest; 69 register unsigned long _len1 asm("3") = (unsigned long) count; 70 register unsigned long _src asm("4") = (unsigned long) src; 71 register unsigned long _len2 asm("5") = (unsigned long) count; 72 int rc = -EFAULT; 73 74 asm volatile ( 75 "0: mvcle %1,%2,0x0\n" 76 "1: jo 0b\n" 77 " lhi %0,0x0\n" 78 "2:\n" 79 EX_TABLE(1b,2b) 80 : "+d" (rc), "+d" (_dest), "+d" (_src), "+d" (_len1), 81 "+d" (_len2), "=m" (*((long *) dest)) 82 : "m" (*((long *) src)) 83 : "cc", "memory"); 84 return rc; 85 } 86 87 /* 88 * Copy memory in real mode (kernel to kernel) 89 */ 90 int memcpy_real(void *dest, void *src, size_t count) 91 { 92 unsigned long flags; 93 int rc; 94 95 if (!count) 96 return 0; 97 local_irq_save(flags); 98 __arch_local_irq_stnsm(0xfbUL); 99 rc = __memcpy_real(dest, src, count); 100 local_irq_restore(flags); 101 return rc; 102 } 103 104 /* 105 * Copy memory in absolute mode (kernel to kernel) 106 */ 107 void memcpy_absolute(void *dest, void *src, size_t count) 108 { 109 unsigned long cr0, flags, prefix; 110 111 flags = arch_local_irq_save(); 112 __ctl_store(cr0, 0, 0); 113 __ctl_clear_bit(0, 28); /* disable lowcore protection */ 114 prefix = store_prefix(); 115 if (prefix) { 116 local_mcck_disable(); 117 set_prefix(0); 118 memcpy(dest, src, count); 119 set_prefix(prefix); 120 local_mcck_enable(); 121 } else { 122 memcpy(dest, src, count); 123 } 124 __ctl_load(cr0, 0, 0); 125 arch_local_irq_restore(flags); 126 } 127 128 /* 129 * Copy memory from kernel (real) to user (virtual) 130 */ 131 int copy_to_user_real(void __user *dest, void *src, unsigned long count) 132 { 133 int offs = 0, size, rc; 134 char *buf; 135 136 buf = (char *) __get_free_page(GFP_KERNEL); 137 if (!buf) 138 return -ENOMEM; 139 rc = -EFAULT; 140 while (offs < count) { 141 size = min(PAGE_SIZE, count - offs); 142 if (memcpy_real(buf, src + offs, size)) 143 goto out; 144 if (copy_to_user(dest + offs, buf, size)) 145 goto out; 146 offs += size; 147 } 148 rc = 0; 149 out: 150 free_page((unsigned long) buf); 151 return rc; 152 } 153 154 /* 155 * Check if physical address is within prefix or zero page 156 */ 157 static int is_swapped(unsigned long addr) 158 { 159 unsigned long lc; 160 int cpu; 161 162 if (addr < sizeof(struct _lowcore)) 163 return 1; 164 for_each_online_cpu(cpu) { 165 lc = (unsigned long) lowcore_ptr[cpu]; 166 if (addr > lc + sizeof(struct _lowcore) - 1 || addr < lc) 167 continue; 168 return 1; 169 } 170 return 0; 171 } 172 173 /* 174 * Convert a physical pointer for /dev/mem access 175 * 176 * For swapped prefix pages a new buffer is returned that contains a copy of 177 * the absolute memory. The buffer size is maximum one page large. 178 */ 179 void *xlate_dev_mem_ptr(phys_addr_t addr) 180 { 181 void *bounce = (void *) addr; 182 unsigned long size; 183 184 get_online_cpus(); 185 preempt_disable(); 186 if (is_swapped(addr)) { 187 size = PAGE_SIZE - (addr & ~PAGE_MASK); 188 bounce = (void *) __get_free_page(GFP_ATOMIC); 189 if (bounce) 190 memcpy_absolute(bounce, (void *) addr, size); 191 } 192 preempt_enable(); 193 put_online_cpus(); 194 return bounce; 195 } 196 197 /* 198 * Free converted buffer for /dev/mem access (if necessary) 199 */ 200 void unxlate_dev_mem_ptr(phys_addr_t addr, void *buf) 201 { 202 if ((void *) addr != buf) 203 free_page((unsigned long) buf); 204 } 205