arch/um/kernel/skas/uaccess.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
   4  */
   5
   6 #include <linux/err.h>
   7 #include <linux/highmem.h>
   8 #include <linux/mm.h>
   9 #include <linux/module.h>
  10 #include <linux/sched.h>
  11 #include <asm/current.h>
  12 #include <asm/page.h>
  13 #include <asm/pgtable.h>
  14 #include <kern_util.h>
  15 #include <os.h>
  16
  17 pte_t *virt_to_pte(struct mm_struct *mm, unsigned long addr)
  18 {
  19         pgd_t *pgd;
  20         p4d_t *p4d;
  21         pud_t *pud;
  22         pmd_t *pmd;
  23
  24         if (mm == NULL)
  25                 return NULL;
  26
  27         pgd = pgd_offset(mm, addr);
  28         if (!pgd_present(*pgd))
  29                 return NULL;
  30
  31         p4d = p4d_offset(pgd, addr);
  32         if (!p4d_present(*p4d))
  33                 return NULL;
  34
  35         pud = pud_offset(p4d, addr);
  36         if (!pud_present(*pud))
  37                 return NULL;
  38
  39         pmd = pmd_offset(pud, addr);
  40         if (!pmd_present(*pmd))
  41                 return NULL;
  42
  43         return pte_offset_kernel(pmd, addr);
  44 }
  45
  46 static pte_t *maybe_map(unsigned long virt, int is_write)
  47 {
  48         pte_t *pte = virt_to_pte(current->mm, virt);
  49         int err, dummy_code;
  50
  51         if ((pte == NULL) || !pte_present(*pte) ||
  52             (is_write && !pte_write(*pte))) {
  53                 err = handle_page_fault(virt, 0, is_write, 1, &dummy_code);
  54                 if (err)
  55                         return NULL;
  56                 pte = virt_to_pte(current->mm, virt);
  57         }
  58         if (!pte_present(*pte))
  59                 pte = NULL;
  60
  61         return pte;
  62 }
  63
  64 static int do_op_one_page(unsigned long addr, int len, int is_write,
  65                  int (*op)(unsigned long addr, int len, void *arg), void *arg)
  66 {
  67         struct page *page;
  68         pte_t *pte;
  69         int n;
  70
  71         pte = maybe_map(addr, is_write);
  72         if (pte == NULL)
  73                 return -1;
  74
  75         page = pte_page(*pte);
  76 #ifdef CONFIG_64BIT
  77         pagefault_disable();
  78         addr = (unsigned long) page_address(page) +
  79                 (addr & ~PAGE_MASK);
  80 #else
  81         addr = (unsigned long) kmap_atomic(page) +
  82                 (addr & ~PAGE_MASK);
  83 #endif
  84         n = (*op)(addr, len, arg);
  85
  86 #ifdef CONFIG_64BIT
  87         pagefault_enable();
  88 #else
  89         kunmap_atomic((void *)addr);
  90 #endif
  91
  92         return n;
  93 }
  94
  95 static long buffer_op(unsigned long addr, int len, int is_write,
  96                       int (*op)(unsigned long, int, void *), void *arg)
  97 {
  98         long size, remain, n;
  99
 100         size = min(PAGE_ALIGN(addr) - addr, (unsigned long) len);
 101         remain = len;
 102
 103         n = do_op_one_page(addr, size, is_write, op, arg);
 104         if (n != 0) {
 105                 remain = (n < 0 ? remain : 0);
 106                 goto out;
 107         }
 108
 109         addr += size;
 110         remain -= size;
 111         if (remain == 0)
 112                 goto out;
 113
 114         while (addr < ((addr + remain) & PAGE_MASK)) {
 115                 n = do_op_one_page(addr, PAGE_SIZE, is_write, op, arg);
 116                 if (n != 0) {
 117                         remain = (n < 0 ? remain : 0);
 118                         goto out;
 119                 }
 120
 121                 addr += PAGE_SIZE;
 122                 remain -= PAGE_SIZE;
 123         }
 124         if (remain == 0)
 125                 goto out;
 126
 127         n = do_op_one_page(addr, remain, is_write, op, arg);
 128         if (n != 0) {
 129                 remain = (n < 0 ? remain : 0);
 130                 goto out;
 131         }
 132
 133         return 0;
 134  out:
 135         return remain;
 136 }
 137
 138 static int copy_chunk_from_user(unsigned long from, int len, void *arg)
 139 {
 140         unsigned long *to_ptr = arg, to = *to_ptr;
 141
 142         memcpy((void *) to, (void *) from, len);
 143         *to_ptr += len;
 144         return 0;
 145 }
 146
 147 unsigned long raw_copy_from_user(void *to, const void __user *from, unsigned long n)
 148 {
 149         if (uaccess_kernel()) {
 150                 memcpy(to, (__force void*)from, n);
 151                 return 0;
 152         }
 153
 154         return buffer_op((unsigned long) from, n, 0, copy_chunk_from_user, &to);
 155 }
 156 EXPORT_SYMBOL(raw_copy_from_user);
 157
 158 static int copy_chunk_to_user(unsigned long to, int len, void *arg)
 159 {
 160         unsigned long *from_ptr = arg, from = *from_ptr;
 161
 162         memcpy((void *) to, (void *) from, len);
 163         *from_ptr += len;
 164         return 0;
 165 }
 166
 167 unsigned long raw_copy_to_user(void __user *to, const void *from, unsigned long n)
 168 {
 169         if (uaccess_kernel()) {
 170                 memcpy((__force void *) to, from, n);
 171                 return 0;
 172         }
 173
 174         return buffer_op((unsigned long) to, n, 1, copy_chunk_to_user, &from);
 175 }
 176 EXPORT_SYMBOL(raw_copy_to_user);
 177
 178 static int strncpy_chunk_from_user(unsigned long from, int len, void *arg)
 179 {
 180         char **to_ptr = arg, *to = *to_ptr;
 181         int n;
 182
 183         strncpy(to, (void *) from, len);
 184         n = strnlen(to, len);
 185         *to_ptr += n;
 186
 187         if (n < len)
 188                 return 1;
 189         return 0;
 190 }
 191
 192 long __strncpy_from_user(char *dst, const char __user *src, long count)
 193 {
 194         long n;
 195         char *ptr = dst;
 196
 197         if (uaccess_kernel()) {
 198                 strncpy(dst, (__force void *) src, count);
 199                 return strnlen(dst, count);
 200         }
 201
 202         n = buffer_op((unsigned long) src, count, 0, strncpy_chunk_from_user,
 203                       &ptr);
 204         if (n != 0)
 205                 return -EFAULT;
 206         return strnlen(dst, count);
 207 }
 208 EXPORT_SYMBOL(__strncpy_from_user);
 209
 210 static int clear_chunk(unsigned long addr, int len, void *unused)
 211 {
 212         memset((void *) addr, 0, len);
 213         return 0;
 214 }
 215
 216 unsigned long __clear_user(void __user *mem, unsigned long len)
 217 {
 218         if (uaccess_kernel()) {
 219                 memset((__force void*)mem, 0, len);
 220                 return 0;
 221         }
 222
 223         return buffer_op((unsigned long) mem, len, 1, clear_chunk, NULL);
 224 }
 225 EXPORT_SYMBOL(__clear_user);
 226
 227 static int strnlen_chunk(unsigned long str, int len, void *arg)
 228 {
 229         int *len_ptr = arg, n;
 230
 231         n = strnlen((void *) str, len);
 232         *len_ptr += n;
 233
 234         if (n < len)
 235                 return 1;
 236         return 0;
 237 }
 238
 239 long __strnlen_user(const void __user *str, long len)
 240 {
 241         int count = 0, n;
 242
 243         if (uaccess_kernel())
 244                 return strnlen((__force char*)str, len) + 1;
 245
 246         n = buffer_op((unsigned long) str, len, 0, strnlen_chunk, &count);
 247         if (n == 0)
 248                 return count + 1;
 249         return 0;
 250 }
 251 EXPORT_SYMBOL(__strnlen_user);