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 static DEFINE_SPINLOCK(s390_kernel_write_lock); 57 58 void notrace s390_kernel_write(void *dst, const void *src, size_t size) 59 { 60 unsigned long flags; 61 long copied; 62 63 spin_lock_irqsave(&s390_kernel_write_lock, flags); 64 while (size) { 65 copied = s390_kernel_write_odd(dst, src, size); 66 dst += copied; 67 src += copied; 68 size -= copied; 69 } 70 spin_unlock_irqrestore(&s390_kernel_write_lock, flags); 71 } 72 73 static int __memcpy_real(void *dest, void *src, size_t count) 74 { 75 register unsigned long _dest asm("2") = (unsigned long) dest; 76 register unsigned long _len1 asm("3") = (unsigned long) count; 77 register unsigned long _src asm("4") = (unsigned long) src; 78 register unsigned long _len2 asm("5") = (unsigned long) count; 79 int rc = -EFAULT; 80 81 asm volatile ( 82 "0: mvcle %1,%2,0x0\n" 83 "1: jo 0b\n" 84 " lhi %0,0x0\n" 85 "2:\n" 86 EX_TABLE(1b,2b) 87 : "+d" (rc), "+d" (_dest), "+d" (_src), "+d" (_len1), 88 "+d" (_len2), "=m" (*((long *) dest)) 89 : "m" (*((long *) src)) 90 : "cc", "memory"); 91 return rc; 92 } 93 94 static unsigned long _memcpy_real(unsigned long dest, unsigned long src, 95 unsigned long count) 96 { 97 int irqs_disabled, rc; 98 unsigned long flags; 99 100 if (!count) 101 return 0; 102 flags = __arch_local_irq_stnsm(0xf8UL); 103 irqs_disabled = arch_irqs_disabled_flags(flags); 104 if (!irqs_disabled) 105 trace_hardirqs_off(); 106 rc = __memcpy_real((void *) dest, (void *) src, (size_t) count); 107 if (!irqs_disabled) 108 trace_hardirqs_on(); 109 __arch_local_irq_ssm(flags); 110 return rc; 111 } 112 113 /* 114 * Copy memory in real mode (kernel to kernel) 115 */ 116 int memcpy_real(void *dest, void *src, size_t count) 117 { 118 if (S390_lowcore.nodat_stack != 0) 119 return CALL_ON_STACK(_memcpy_real, S390_lowcore.nodat_stack, 120 3, dest, src, count); 121 /* 122 * This is a really early memcpy_real call, the stacks are 123 * not set up yet. Just call _memcpy_real on the early boot 124 * stack 125 */ 126 return _memcpy_real((unsigned long) dest,(unsigned long) src, 127 (unsigned long) count); 128 } 129 130 /* 131 * Copy memory in absolute mode (kernel to kernel) 132 */ 133 void memcpy_absolute(void *dest, void *src, size_t count) 134 { 135 unsigned long cr0, flags, prefix; 136 137 flags = arch_local_irq_save(); 138 __ctl_store(cr0, 0, 0); 139 __ctl_clear_bit(0, 28); /* disable lowcore protection */ 140 prefix = store_prefix(); 141 if (prefix) { 142 local_mcck_disable(); 143 set_prefix(0); 144 memcpy(dest, src, count); 145 set_prefix(prefix); 146 local_mcck_enable(); 147 } else { 148 memcpy(dest, src, count); 149 } 150 __ctl_load(cr0, 0, 0); 151 arch_local_irq_restore(flags); 152 } 153 154 /* 155 * Copy memory from kernel (real) to user (virtual) 156 */ 157 int copy_to_user_real(void __user *dest, void *src, unsigned long count) 158 { 159 int offs = 0, size, rc; 160 char *buf; 161 162 buf = (char *) __get_free_page(GFP_KERNEL); 163 if (!buf) 164 return -ENOMEM; 165 rc = -EFAULT; 166 while (offs < count) { 167 size = min(PAGE_SIZE, count - offs); 168 if (memcpy_real(buf, src + offs, size)) 169 goto out; 170 if (copy_to_user(dest + offs, buf, size)) 171 goto out; 172 offs += size; 173 } 174 rc = 0; 175 out: 176 free_page((unsigned long) buf); 177 return rc; 178 } 179 180 /* 181 * Check if physical address is within prefix or zero page 182 */ 183 static int is_swapped(unsigned long addr) 184 { 185 unsigned long lc; 186 int cpu; 187 188 if (addr < sizeof(struct lowcore)) 189 return 1; 190 for_each_online_cpu(cpu) { 191 lc = (unsigned long) lowcore_ptr[cpu]; 192 if (addr > lc + sizeof(struct lowcore) - 1 || addr < lc) 193 continue; 194 return 1; 195 } 196 return 0; 197 } 198 199 /* 200 * Convert a physical pointer for /dev/mem access 201 * 202 * For swapped prefix pages a new buffer is returned that contains a copy of 203 * the absolute memory. The buffer size is maximum one page large. 204 */ 205 void *xlate_dev_mem_ptr(phys_addr_t addr) 206 { 207 void *bounce = (void *) addr; 208 unsigned long size; 209 210 get_online_cpus(); 211 preempt_disable(); 212 if (is_swapped(addr)) { 213 size = PAGE_SIZE - (addr & ~PAGE_MASK); 214 bounce = (void *) __get_free_page(GFP_ATOMIC); 215 if (bounce) 216 memcpy_absolute(bounce, (void *) addr, size); 217 } 218 preempt_enable(); 219 put_online_cpus(); 220 return bounce; 221 } 222 223 /* 224 * Free converted buffer for /dev/mem access (if necessary) 225 */ 226 void unxlate_dev_mem_ptr(phys_addr_t addr, void *buf) 227 { 228 if ((void *) addr != buf) 229 free_page((unsigned long) buf); 230 } 231