linux/arch/um/kernel/skas/uaccess.c
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   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 <kern_util.h>
  14#include <asm/futex.h>
  15#include <os.h>
  16
  17pte_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
  46static 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
  64static 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
  95static 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
 138static 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
 147unsigned 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}
 156EXPORT_SYMBOL(raw_copy_from_user);
 157
 158static 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
 167unsigned 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}
 176EXPORT_SYMBOL(raw_copy_to_user);
 177
 178static 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
 192long __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}
 208EXPORT_SYMBOL(__strncpy_from_user);
 209
 210static int clear_chunk(unsigned long addr, int len, void *unused)
 211{
 212        memset((void *) addr, 0, len);
 213        return 0;
 214}
 215
 216unsigned 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}
 225EXPORT_SYMBOL(__clear_user);
 226
 227static 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
 239long __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}
 251EXPORT_SYMBOL(__strnlen_user);
 252
 253/**
 254 * arch_futex_atomic_op_inuser() - Atomic arithmetic operation with constant
 255 *                        argument and comparison of the previous
 256 *                        futex value with another constant.
 257 *
 258 * @encoded_op: encoded operation to execute
 259 * @uaddr:      pointer to user space address
 260 *
 261 * Return:
 262 * 0 - On success
 263 * -EFAULT - User access resulted in a page fault
 264 * -EAGAIN - Atomic operation was unable to complete due to contention
 265 * -ENOSYS - Operation not supported
 266 */
 267
 268int arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval, u32 __user *uaddr)
 269{
 270        int oldval, ret;
 271        struct page *page;
 272        unsigned long addr = (unsigned long) uaddr;
 273        pte_t *pte;
 274
 275        ret = -EFAULT;
 276        if (!access_ok(uaddr, sizeof(*uaddr)))
 277                return -EFAULT;
 278        preempt_disable();
 279        pte = maybe_map(addr, 1);
 280        if (pte == NULL)
 281                goto out_inuser;
 282
 283        page = pte_page(*pte);
 284#ifdef CONFIG_64BIT
 285        pagefault_disable();
 286        addr = (unsigned long) page_address(page) +
 287                        (((unsigned long) addr) & ~PAGE_MASK);
 288#else
 289        addr = (unsigned long) kmap_atomic(page) +
 290                ((unsigned long) addr & ~PAGE_MASK);
 291#endif
 292        uaddr = (u32 *) addr;
 293        oldval = *uaddr;
 294
 295        ret = 0;
 296
 297        switch (op) {
 298        case FUTEX_OP_SET:
 299                *uaddr = oparg;
 300                break;
 301        case FUTEX_OP_ADD:
 302                *uaddr += oparg;
 303                break;
 304        case FUTEX_OP_OR:
 305                *uaddr |= oparg;
 306                break;
 307        case FUTEX_OP_ANDN:
 308                *uaddr &= ~oparg;
 309                break;
 310        case FUTEX_OP_XOR:
 311                *uaddr ^= oparg;
 312                break;
 313        default:
 314                ret = -ENOSYS;
 315        }
 316#ifdef CONFIG_64BIT
 317        pagefault_enable();
 318#else
 319        kunmap_atomic((void *)addr);
 320#endif
 321
 322out_inuser:
 323        preempt_enable();
 324
 325        if (ret == 0)
 326                *oval = oldval;
 327
 328        return ret;
 329}
 330EXPORT_SYMBOL(arch_futex_atomic_op_inuser);
 331
 332/**
 333 * futex_atomic_cmpxchg_inatomic() - Compare and exchange the content of the
 334 *                              uaddr with newval if the current value is
 335 *                              oldval.
 336 * @uval:       pointer to store content of @uaddr
 337 * @uaddr:      pointer to user space address
 338 * @oldval:     old value
 339 * @newval:     new value to store to @uaddr
 340 *
 341 * Return:
 342 * 0 - On success
 343 * -EFAULT - User access resulted in a page fault
 344 * -EAGAIN - Atomic operation was unable to complete due to contention
 345 * -ENOSYS - Function not implemented (only if !HAVE_FUTEX_CMPXCHG)
 346 */
 347
 348int futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
 349                              u32 oldval, u32 newval)
 350{
 351        struct page *page;
 352        pte_t *pte;
 353        int ret = -EFAULT;
 354
 355        if (!access_ok(uaddr, sizeof(*uaddr)))
 356                return -EFAULT;
 357
 358        preempt_disable();
 359        pte = maybe_map((unsigned long) uaddr, 1);
 360        if (pte == NULL)
 361                goto out_inatomic;
 362
 363        page = pte_page(*pte);
 364#ifdef CONFIG_64BIT
 365        pagefault_disable();
 366        uaddr = page_address(page) + (((unsigned long) uaddr) & ~PAGE_MASK);
 367#else
 368        uaddr = kmap_atomic(page) + ((unsigned long) uaddr & ~PAGE_MASK);
 369#endif
 370
 371        *uval = *uaddr;
 372
 373        ret = cmpxchg(uaddr, oldval, newval);
 374
 375#ifdef CONFIG_64BIT
 376        pagefault_enable();
 377#else
 378        kunmap_atomic(uaddr);
 379#endif
 380        ret = 0;
 381
 382out_inatomic:
 383        preempt_enable();
 384        return ret;
 385}
 386EXPORT_SYMBOL(futex_atomic_cmpxchg_inatomic);
 387