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 int irqs_disabled, rc; 97 unsigned long flags; 98 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; 110 } 111 112 /* 113 * Copy memory in absolute mode (kernel to kernel) 114 */ 115 void memcpy_absolute(void *dest, void *src, size_t count) 116 { 117 unsigned long cr0, flags, prefix; 118 119 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); 131 } 132 __ctl_load(cr0, 0, 0); 133 arch_local_irq_restore(flags); 134 } 135 136 /* 137 * Copy memory from kernel (real) to user (virtual) 138 */ 139 int copy_to_user_real(void __user *dest, void *src, unsigned long count) 140 { 141 int offs = 0, size, rc; 142 char *buf; 143 144 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; 155 } 156 rc = 0; 157 out: 158 free_page((unsigned long) buf); 159 return rc; 160 } 161 162 /* 163 * Check if physical address is within prefix or zero page 164 */ 165 static int is_swapped(unsigned long addr) 166 { 167 unsigned long lc; 168 int cpu; 169 170 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; 177 } 178 return 0; 179 } 180 181 /* 182 * Convert a physical pointer for /dev/mem access 183 * 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. 186 */ 187 void *xlate_dev_mem_ptr(phys_addr_t addr) 188 { 189 void *bounce = (void *) addr; 190 unsigned long size; 191 192 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); 199 } 200 preempt_enable(); 201 put_online_cpus(); 202 return bounce; 203 } 204 205 /* 206 * Free converted buffer for /dev/mem access (if necessary) 207 */ 208 void unxlate_dev_mem_ptr(phys_addr_t addr, void *buf) 209 { 210 if ((void *) addr != buf) 211 free_page((unsigned long) buf); 212 } 213