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 19 static 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 */ 58 void 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 70 static 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 */ 94 int memcpy_real(void *dest, void *src, size_t count) 95 { 96 unsigned long flags; 97 int rc; 98 99 if (!count) 100 return 0; 101 local_irq_save(flags); 102 __arch_local_irq_stnsm(0xfbUL); 103 rc = __memcpy_real(dest, src, count); 104 local_irq_restore(flags); 105 return rc; 106 } 107 108 /* 109 * Copy memory in absolute mode (kernel to kernel) 110 */ 111 void memcpy_absolute(void *dest, void *src, size_t count) 112 { 113 unsigned long cr0, flags, prefix; 114 115 flags = arch_local_irq_save(); 116 __ctl_store(cr0, 0, 0); 117 __ctl_clear_bit(0, 28); /* disable lowcore protection */ 118 prefix = store_prefix(); 119 if (prefix) { 120 local_mcck_disable(); 121 set_prefix(0); 122 memcpy(dest, src, count); 123 set_prefix(prefix); 124 local_mcck_enable(); 125 } else { 126 memcpy(dest, src, count); 127 } 128 __ctl_load(cr0, 0, 0); 129 arch_local_irq_restore(flags); 130 } 131 132 /* 133 * Copy memory from kernel (real) to user (virtual) 134 */ 135 int copy_to_user_real(void __user *dest, void *src, unsigned long count) 136 { 137 int offs = 0, size, rc; 138 char *buf; 139 140 buf = (char *) __get_free_page(GFP_KERNEL); 141 if (!buf) 142 return -ENOMEM; 143 rc = -EFAULT; 144 while (offs < count) { 145 size = min(PAGE_SIZE, count - offs); 146 if (memcpy_real(buf, src + offs, size)) 147 goto out; 148 if (copy_to_user(dest + offs, buf, size)) 149 goto out; 150 offs += size; 151 } 152 rc = 0; 153 out: 154 free_page((unsigned long) buf); 155 return rc; 156 } 157 158 /* 159 * Check if physical address is within prefix or zero page 160 */ 161 static int is_swapped(unsigned long addr) 162 { 163 unsigned long lc; 164 int cpu; 165 166 if (addr < sizeof(struct _lowcore)) 167 return 1; 168 for_each_online_cpu(cpu) { 169 lc = (unsigned long) lowcore_ptr[cpu]; 170 if (addr > lc + sizeof(struct _lowcore) - 1 || addr < lc) 171 continue; 172 return 1; 173 } 174 return 0; 175 } 176 177 /* 178 * Convert a physical pointer for /dev/mem access 179 * 180 * For swapped prefix pages a new buffer is returned that contains a copy of 181 * the absolute memory. The buffer size is maximum one page large. 182 */ 183 void *xlate_dev_mem_ptr(phys_addr_t addr) 184 { 185 void *bounce = (void *) addr; 186 unsigned long size; 187 188 get_online_cpus(); 189 preempt_disable(); 190 if (is_swapped(addr)) { 191 size = PAGE_SIZE - (addr & ~PAGE_MASK); 192 bounce = (void *) __get_free_page(GFP_ATOMIC); 193 if (bounce) 194 memcpy_absolute(bounce, (void *) addr, size); 195 } 196 preempt_enable(); 197 put_online_cpus(); 198 return bounce; 199 } 200 201 /* 202 * Free converted buffer for /dev/mem access (if necessary) 203 */ 204 void unxlate_dev_mem_ptr(phys_addr_t addr, void *buf) 205 { 206 if ((void *) addr != buf) 207 free_page((unsigned long) buf); 208 } 209