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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 
 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         return buffer_op((unsigned long) from, n, 0, copy_chunk_from_user, &to);
150 }
151 EXPORT_SYMBOL(raw_copy_from_user);
152 
153 static int copy_chunk_to_user(unsigned long to, int len, void *arg)
154 {
155         unsigned long *from_ptr = arg, from = *from_ptr;
156 
157         memcpy((void *) to, (void *) from, len);
158         *from_ptr += len;
159         return 0;
160 }
161 
162 unsigned long raw_copy_to_user(void __user *to, const void *from, unsigned long n)
163 {
164         return buffer_op((unsigned long) to, n, 1, copy_chunk_to_user, &from);
165 }
166 EXPORT_SYMBOL(raw_copy_to_user);
167 
168 static int strncpy_chunk_from_user(unsigned long from, int len, void *arg)
169 {
170         char **to_ptr = arg, *to = *to_ptr;
171         int n;
172 
173         strncpy(to, (void *) from, len);
174         n = strnlen(to, len);
175         *to_ptr += n;
176 
177         if (n < len)
178                 return 1;
179         return 0;
180 }
181 
182 long strncpy_from_user(char *dst, const char __user *src, long count)
183 {
184         long n;
185         char *ptr = dst;
186 
187         if (!access_ok(src, 1))
188                 return -EFAULT;
189         n = buffer_op((unsigned long) src, count, 0, strncpy_chunk_from_user,
190                       &ptr);
191         if (n != 0)
192                 return -EFAULT;
193         return strnlen(dst, count);
194 }
195 EXPORT_SYMBOL(strncpy_from_user);
196 
197 static int clear_chunk(unsigned long addr, int len, void *unused)
198 {
199         memset((void *) addr, 0, len);
200         return 0;
201 }
202 
203 unsigned long __clear_user(void __user *mem, unsigned long len)
204 {
205         return buffer_op((unsigned long) mem, len, 1, clear_chunk, NULL);
206 }
207 EXPORT_SYMBOL(__clear_user);
208 
209 static int strnlen_chunk(unsigned long str, int len, void *arg)
210 {
211         int *len_ptr = arg, n;
212 
213         n = strnlen((void *) str, len);
214         *len_ptr += n;
215 
216         if (n < len)
217                 return 1;
218         return 0;
219 }
220 
221 long strnlen_user(const char __user *str, long len)
222 {
223         int count = 0, n;
224 
225         if (!access_ok(str, 1))
226                 return -EFAULT;
227         n = buffer_op((unsigned long) str, len, 0, strnlen_chunk, &count);
228         if (n == 0)
229                 return count + 1;
230         return 0;
231 }
232 EXPORT_SYMBOL(strnlen_user);
233 
234 /**
235  * arch_futex_atomic_op_inuser() - Atomic arithmetic operation with constant
236  *                        argument and comparison of the previous
237  *                        futex value with another constant.
238  *
239  * @encoded_op: encoded operation to execute
240  * @uaddr:      pointer to user space address
241  *
242  * Return:
243  * 0 - On success
244  * -EFAULT - User access resulted in a page fault
245  * -EAGAIN - Atomic operation was unable to complete due to contention
246  * -ENOSYS - Operation not supported
247  */
248 
249 int arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval, u32 __user *uaddr)
250 {
251         int oldval, ret;
252         struct page *page;
253         unsigned long addr = (unsigned long) uaddr;
254         pte_t *pte;
255 
256         ret = -EFAULT;
257         if (!access_ok(uaddr, sizeof(*uaddr)))
258                 return -EFAULT;
259         preempt_disable();
260         pte = maybe_map(addr, 1);
261         if (pte == NULL)
262                 goto out_inuser;
263 
264         page = pte_page(*pte);
265 #ifdef CONFIG_64BIT
266         pagefault_disable();
267         addr = (unsigned long) page_address(page) +
268                         (((unsigned long) addr) & ~PAGE_MASK);
269 #else
270         addr = (unsigned long) kmap_atomic(page) +
271                 ((unsigned long) addr & ~PAGE_MASK);
272 #endif
273         uaddr = (u32 *) addr;
274         oldval = *uaddr;
275 
276         ret = 0;
277 
278         switch (op) {
279         case FUTEX_OP_SET:
280                 *uaddr = oparg;
281                 break;
282         case FUTEX_OP_ADD:
283                 *uaddr += oparg;
284                 break;
285         case FUTEX_OP_OR:
286                 *uaddr |= oparg;
287                 break;
288         case FUTEX_OP_ANDN:
289                 *uaddr &= ~oparg;
290                 break;
291         case FUTEX_OP_XOR:
292                 *uaddr ^= oparg;
293                 break;
294         default:
295                 ret = -ENOSYS;
296         }
297 #ifdef CONFIG_64BIT
298         pagefault_enable();
299 #else
300         kunmap_atomic((void *)addr);
301 #endif
302 
303 out_inuser:
304         preempt_enable();
305 
306         if (ret == 0)
307                 *oval = oldval;
308 
309         return ret;
310 }
311 EXPORT_SYMBOL(arch_futex_atomic_op_inuser);
312 
313 /**
314  * futex_atomic_cmpxchg_inatomic() - Compare and exchange the content of the
315  *                              uaddr with newval if the current value is
316  *                              oldval.
317  * @uval:       pointer to store content of @uaddr
318  * @uaddr:      pointer to user space address
319  * @oldval:     old value
320  * @newval:     new value to store to @uaddr
321  *
322  * Return:
323  * 0 - On success
324  * -EFAULT - User access resulted in a page fault
325  * -EAGAIN - Atomic operation was unable to complete due to contention
326  */
327 
328 int futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
329                               u32 oldval, u32 newval)
330 {
331         struct page *page;
332         pte_t *pte;
333         int ret = -EFAULT;
334 
335         if (!access_ok(uaddr, sizeof(*uaddr)))
336                 return -EFAULT;
337 
338         preempt_disable();
339         pte = maybe_map((unsigned long) uaddr, 1);
340         if (pte == NULL)
341                 goto out_inatomic;
342 
343         page = pte_page(*pte);
344 #ifdef CONFIG_64BIT
345         pagefault_disable();
346         uaddr = page_address(page) + (((unsigned long) uaddr) & ~PAGE_MASK);
347 #else
348         uaddr = kmap_atomic(page) + ((unsigned long) uaddr & ~PAGE_MASK);
349 #endif
350 
351         *uval = *uaddr;
352 
353         ret = cmpxchg(uaddr, oldval, newval);
354 
355 #ifdef CONFIG_64BIT
356         pagefault_enable();
357 #else
358         kunmap_atomic(uaddr);
359 #endif
360         ret = 0;
361 
362 out_inatomic:
363         preempt_enable();
364         return ret;
365 }
366 EXPORT_SYMBOL(futex_atomic_cmpxchg_inatomic);
367 

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