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 #include <asm/stacktrace.h> 20 21 static notrace long s390_kernel_write_odd(void *dst, const void *src, size_t size) 22 { 23 unsigned long aligned, offset, count; 24 char tmp[8]; 25 26 aligned = (unsigned long) dst & ~7UL; 27 offset = (unsigned long) dst & 7UL; 28 size = min(8UL - offset, size); 29 count = size - 1; 30 asm volatile( 31 " bras 1,0f\n" 32 " mvc 0(1,%4),0(%5)\n" 33 "0: mvc 0(8,%3),0(%0)\n" 34 " ex %1,0(1)\n" 35 " lg %1,0(%3)\n" 36 " lra %0,0(%0)\n" 37 " sturg %1,%0\n" 38 : "+&a" (aligned), "+&a" (count), "=m" (tmp) 39 : "a" (&tmp), "a" (&tmp[offset]), "a" (src) 40 : "cc", "memory", "1"); 41 return size; 42 } 43 44 /* 45 * s390_kernel_write - write to kernel memory bypassing DAT 46 * @dst: destination address 47 * @src: source address 48 * @size: number of bytes to copy 49 * 50 * This function writes to kernel memory bypassing DAT and possible page table 51 * write protection. It writes to the destination using the sturg instruction. 52 * Therefore we have a read-modify-write sequence: the function reads eight 53 * bytes from destination at an eight byte boundary, modifies the bytes 54 * requested and writes the result back in a loop. 55 * 56 * Note: this means that this function may not be called concurrently on 57 * several cpus with overlapping words, since this may potentially 58 * cause data corruption. 59 */ 60 void notrace s390_kernel_write(void *dst, const void *src, size_t size) 61 { 62 long copied; 63 64 while (size) { 65 copied = s390_kernel_write_odd(dst, src, size); 66 dst += copied; 67 src += copied; 68 size -= copied; 69 } 70 } 71 72 static int __memcpy_real(void *dest, void *src, size_t count) 73 { 74 register unsigned long _dest asm("2") = (unsigned long) dest; 75 register unsigned long _len1 asm("3") = (unsigned long) count; 76 register unsigned long _src asm("4") = (unsigned long) src; 77 register unsigned long _len2 asm("5") = (unsigned long) count; 78 int rc = -EFAULT; 79 80 asm volatile ( 81 "0: mvcle %1,%2,0x0\n" 82 "1: jo 0b\n" 83 " lhi %0,0x0\n" 84 "2:\n" 85 EX_TABLE(1b,2b) 86 : "+d" (rc), "+d" (_dest), "+d" (_src), "+d" (_len1), 87 "+d" (_len2), "=m" (*((long *) dest)) 88 : "m" (*((long *) src)) 89 : "cc", "memory"); 90 return rc; 91 } 92 93 static unsigned long _memcpy_real(unsigned long dest, unsigned long src, 94 unsigned long 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((void *) dest, (void *) src, (size_t) 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 real mode (kernel to kernel) 114 */ 115 int memcpy_real(void *dest, void *src, size_t count) 116 { 117 if (S390_lowcore.nodat_stack != 0) 118 return CALL_ON_STACK(_memcpy_real, S390_lowcore.nodat_stack, 119 3, dest, src, count); 120 /* 121 * This is a really early memcpy_real call, the stacks are 122 * not set up yet. Just call _memcpy_real on the early boot 123 * stack 124 */ 125 return _memcpy_real((unsigned long) dest,(unsigned long) src, 126 (unsigned long) count); 127 } 128 129 /* 130 * Copy memory in absolute mode (kernel to kernel) 131 */ 132 void memcpy_absolute(void *dest, void *src, size_t count) 133 { 134 unsigned long cr0, flags, prefix; 135 136 flags = arch_local_irq_save(); 137 __ctl_store(cr0, 0, 0); 138 __ctl_clear_bit(0, 28); /* disable lowcore protection */ 139 prefix = store_prefix(); 140 if (prefix) { 141 local_mcck_disable(); 142 set_prefix(0); 143 memcpy(dest, src, count); 144 set_prefix(prefix); 145 local_mcck_enable(); 146 } else { 147 memcpy(dest, src, count); 148 } 149 __ctl_load(cr0, 0, 0); 150 arch_local_irq_restore(flags); 151 } 152 153 /* 154 * Copy memory from kernel (real) to user (virtual) 155 */ 156 int copy_to_user_real(void __user *dest, void *src, unsigned long count) 157 { 158 int offs = 0, size, rc; 159 char *buf; 160 161 buf = (char *) __get_free_page(GFP_KERNEL); 162 if (!buf) 163 return -ENOMEM; 164 rc = -EFAULT; 165 while (offs < count) { 166 size = min(PAGE_SIZE, count - offs); 167 if (memcpy_real(buf, src + offs, size)) 168 goto out; 169 if (copy_to_user(dest + offs, buf, size)) 170 goto out; 171 offs += size; 172 } 173 rc = 0; 174 out: 175 free_page((unsigned long) buf); 176 return rc; 177 } 178 179 /* 180 * Check if physical address is within prefix or zero page 181 */ 182 static int is_swapped(unsigned long addr) 183 { 184 unsigned long lc; 185 int cpu; 186 187 if (addr < sizeof(struct lowcore)) 188 return 1; 189 for_each_online_cpu(cpu) { 190 lc = (unsigned long) lowcore_ptr[cpu]; 191 if (addr > lc + sizeof(struct lowcore) - 1 || addr < lc) 192 continue; 193 return 1; 194 } 195 return 0; 196 } 197 198 /* 199 * Convert a physical pointer for /dev/mem access 200 * 201 * For swapped prefix pages a new buffer is returned that contains a copy of 202 * the absolute memory. The buffer size is maximum one page large. 203 */ 204 void *xlate_dev_mem_ptr(phys_addr_t addr) 205 { 206 void *bounce = (void *) addr; 207 unsigned long size; 208 209 get_online_cpus(); 210 preempt_disable(); 211 if (is_swapped(addr)) { 212 size = PAGE_SIZE - (addr & ~PAGE_MASK); 213 bounce = (void *) __get_free_page(GFP_ATOMIC); 214 if (bounce) 215 memcpy_absolute(bounce, (void *) addr, size); 216 } 217 preempt_enable(); 218 put_online_cpus(); 219 return bounce; 220 } 221 222 /* 223 * Free converted buffer for /dev/mem access (if necessary) 224 */ 225 void unxlate_dev_mem_ptr(phys_addr_t addr, void *buf) 226 { 227 if ((void *) addr != buf) 228 free_page((unsigned long) buf); 229 } 230