1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Access kernel memory without faulting -- s390 specific implementation. 4 * 5 * Copyright IBM Corp. 2009, 2015 6 * 7 * Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>, 8 * 9 */ 10 11 #include <linux/uaccess.h> 12 #include <linux/kernel.h> 13 #include <linux/types.h> 14 #include <linux/errno.h> 15 #include <linux/gfp.h> 16 #include <linux/cpu.h> 17 #include <asm/ctl_reg.h> 18 #include <asm/io.h> 19 20 static notrace long s390_kernel_write_odd(void *dst, const void *src, size_t size) 21 { 22 unsigned long aligned, offset, count; 23 char tmp[8]; 24 25 aligned = (unsigned long) dst & ~7UL; 26 offset = (unsigned long) dst & 7UL; 27 size = min(8UL - offset, size); 28 count = size - 1; 29 asm volatile( 30 " bras 1,0f\n" 31 " mvc 0(1,%4),0(%5)\n" 32 "0: mvc 0(8,%3),0(%0)\n" 33 " ex %1,0(1)\n" 34 " lg %1,0(%3)\n" 35 " lra %0,0(%0)\n" 36 " sturg %1,%0\n" 37 : "+&a" (aligned), "+&a" (count), "=m" (tmp) 38 : "a" (&tmp), "a" (&tmp[offset]), "a" (src) 39 : "cc", "memory", "1"); 40 return size; 41 } 42 43 /* 44 * s390_kernel_write - write to kernel memory bypassing DAT 45 * @dst: destination address 46 * @src: source address 47 * @size: number of bytes to copy 48 * 49 * This function writes to kernel memory bypassing DAT and possible page table 50 * write protection. It writes to the destination using the sturg instruction. 51 * Therefore we have a read-modify-write sequence: the function reads eight 52 * bytes from destination at an eight byte boundary, modifies the bytes 53 * requested and writes the result back in a loop. 54 * 55 * Note: this means that this function may not be called concurrently on 56 * several cpus with overlapping words, since this may potentially 57 * cause data corruption. 58 */ 59 void notrace s390_kernel_write(void *dst, const void *src, size_t size) 60 { 61 long copied; 62 63 while (size) { 64 copied = s390_kernel_write_odd(dst, src, size); 65 dst += copied; 66 src += copied; 67 size -= copied; 68 } 69 } 70 71 static int __memcpy_real(void *dest, void *src, size_t count) 72 { 73 register unsigned long _dest asm("2") = (unsigned long) dest; 74 register unsigned long _len1 asm("3") = (unsigned long) count; 75 register unsigned long _src asm("4") = (unsigned long) src; 76 register unsigned long _len2 asm("5") = (unsigned long) count; 77 int rc = -EFAULT; 78 79 asm volatile ( 80 "0: mvcle %1,%2,0x0\n" 81 "1: jo 0b\n" 82 " lhi %0,0x0\n" 83 "2:\n" 84 EX_TABLE(1b,2b) 85 : "+d" (rc), "+d" (_dest), "+d" (_src), "+d" (_len1), 86 "+d" (_len2), "=m" (*((long *) dest)) 87 : "m" (*((long *) src)) 88 : "cc", "memory"); 89 return rc; 90 } 91 92 static unsigned long _memcpy_real(unsigned long dest, unsigned long src, 93 unsigned long count) 94 { 95 int irqs_disabled, rc; 96 unsigned long flags; 97 98 if (!count) 99 return 0; 100 flags = __arch_local_irq_stnsm(0xf8UL); 101 irqs_disabled = arch_irqs_disabled_flags(flags); 102 if (!irqs_disabled) 103 trace_hardirqs_off(); 104 rc = __memcpy_real((void *) dest, (void *) src, (size_t) count); 105 if (!irqs_disabled) 106 trace_hardirqs_on(); 107 __arch_local_irq_ssm(flags); 108 return rc; 109 } 110 111 /* 112 * Copy memory in real mode (kernel to kernel) 113 */ 114 int memcpy_real(void *dest, void *src, size_t count) 115 { 116 if (S390_lowcore.nodat_stack != 0) 117 return CALL_ON_STACK(_memcpy_real, S390_lowcore.nodat_stack, 118 3, dest, src, count); 119 /* 120 * This is a really early memcpy_real call, the stacks are 121 * not set up yet. Just call _memcpy_real on the early boot 122 * stack 123 */ 124 return _memcpy_real((unsigned long) dest,(unsigned long) src, 125 (unsigned long) count); 126 } 127 128 /* 129 * Copy memory in absolute mode (kernel to kernel) 130 */ 131 void memcpy_absolute(void *dest, void *src, size_t count) 132 { 133 unsigned long cr0, flags, prefix; 134 135 flags = arch_local_irq_save(); 136 __ctl_store(cr0, 0, 0); 137 __ctl_clear_bit(0, 28); /* disable lowcore protection */ 138 prefix = store_prefix(); 139 if (prefix) { 140 local_mcck_disable(); 141 set_prefix(0); 142 memcpy(dest, src, count); 143 set_prefix(prefix); 144 local_mcck_enable(); 145 } else { 146 memcpy(dest, src, count); 147 } 148 __ctl_load(cr0, 0, 0); 149 arch_local_irq_restore(flags); 150 } 151 152 /* 153 * Copy memory from kernel (real) to user (virtual) 154 */ 155 int copy_to_user_real(void __user *dest, void *src, unsigned long count) 156 { 157 int offs = 0, size, rc; 158 char *buf; 159 160 buf = (char *) __get_free_page(GFP_KERNEL); 161 if (!buf) 162 return -ENOMEM; 163 rc = -EFAULT; 164 while (offs < count) { 165 size = min(PAGE_SIZE, count - offs); 166 if (memcpy_real(buf, src + offs, size)) 167 goto out; 168 if (copy_to_user(dest + offs, buf, size)) 169 goto out; 170 offs += size; 171 } 172 rc = 0; 173 out: 174 free_page((unsigned long) buf); 175 return rc; 176 } 177 178 /* 179 * Check if physical address is within prefix or zero page 180 */ 181 static int is_swapped(unsigned long addr) 182 { 183 unsigned long lc; 184 int cpu; 185 186 if (addr < sizeof(struct lowcore)) 187 return 1; 188 for_each_online_cpu(cpu) { 189 lc = (unsigned long) lowcore_ptr[cpu]; 190 if (addr > lc + sizeof(struct lowcore) - 1 || addr < lc) 191 continue; 192 return 1; 193 } 194 return 0; 195 } 196 197 /* 198 * Convert a physical pointer for /dev/mem access 199 * 200 * For swapped prefix pages a new buffer is returned that contains a copy of 201 * the absolute memory. The buffer size is maximum one page large. 202 */ 203 void *xlate_dev_mem_ptr(phys_addr_t addr) 204 { 205 void *bounce = (void *) addr; 206 unsigned long size; 207 208 get_online_cpus(); 209 preempt_disable(); 210 if (is_swapped(addr)) { 211 size = PAGE_SIZE - (addr & ~PAGE_MASK); 212 bounce = (void *) __get_free_page(GFP_ATOMIC); 213 if (bounce) 214 memcpy_absolute(bounce, (void *) addr, size); 215 } 216 preempt_enable(); 217 put_online_cpus(); 218 return bounce; 219 } 220 221 /* 222 * Free converted buffer for /dev/mem access (if necessary) 223 */ 224 void unxlate_dev_mem_ptr(phys_addr_t addr, void *buf) 225 { 226 if ((void *) addr != buf) 227 free_page((unsigned long) buf); 228 } 229