arch/x86/um/ldt.c

   1 /*
   2  * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
   3  * Licensed under the GPL
   4  */
   5
   6 #include <linux/mm.h>
   7 #include <linux/sched.h>
   8 #include <linux/slab.h>
   9 #include <asm/unistd.h>
  10 #include "os.h"
  11 #include "proc_mm.h"
  12 #include "skas.h"
  13 #include "skas_ptrace.h"
  14 #include "sysdep/tls.h"
  15
  16 extern int modify_ldt(int func, void *ptr, unsigned long bytecount);
  17
  18 static long write_ldt_entry(struct mm_id *mm_idp, int func,
  19                      struct user_desc *desc, void **addr, int done)
  20 {
  21         long res;
  22
  23         if (proc_mm) {
  24                 /*
  25                  * This is a special handling for the case, that the mm to
  26                  * modify isn't current->active_mm.
  27                  * If this is called directly by modify_ldt,
  28                  *     (current->active_mm->context.skas.u == mm_idp)
  29                  * will be true. So no call to __switch_mm(mm_idp) is done.
  30                  * If this is called in case of init_new_ldt or PTRACE_LDT,
  31                  * mm_idp won't belong to current->active_mm, but child->mm.
  32                  * So we need to switch child's mm into our userspace, then
  33                  * later switch back.
  34                  *
  35                  * Note: I'm unsure: should interrupts be disabled here?
  36                  */
  37                 if (!current->active_mm || current->active_mm == &init_mm ||
  38                     mm_idp != &current->active_mm->context.id)
  39                         __switch_mm(mm_idp);
  40         }
  41
  42         if (ptrace_ldt) {
  43                 struct ptrace_ldt ldt_op = (struct ptrace_ldt) {
  44                         .func = func,
  45                         .ptr = desc,
  46                         .bytecount = sizeof(*desc)};
  47                 u32 cpu;
  48                 int pid;
  49
  50                 if (!proc_mm)
  51                         pid = mm_idp->u.pid;
  52                 else {
  53                         cpu = get_cpu();
  54                         pid = userspace_pid[cpu];
  55                 }
  56
  57                 res = os_ptrace_ldt(pid, 0, (unsigned long) &ldt_op);
  58
  59                 if (proc_mm)
  60                         put_cpu();
  61         }
  62         else {
  63                 void *stub_addr;
  64                 res = syscall_stub_data(mm_idp, (unsigned long *)desc,
  65                                         (sizeof(*desc) + sizeof(long) - 1) &
  66                                             ~(sizeof(long) - 1),
  67                                         addr, &stub_addr);
  68                 if (!res) {
  69                         unsigned long args[] = { func,
  70                                                  (unsigned long)stub_addr,
  71                                                  sizeof(*desc),
  72                                                  0, 0, 0 };
  73                         res = run_syscall_stub(mm_idp, __NR_modify_ldt, args,
  74                                                0, addr, done);
  75                 }
  76         }
  77
  78         if (proc_mm) {
  79                 /*
  80                  * This is the second part of special handling, that makes
  81                  * PTRACE_LDT possible to implement.
  82                  */
  83                 if (current->active_mm && current->active_mm != &init_mm &&
  84                     mm_idp != &current->active_mm->context.id)
  85                         __switch_mm(&current->active_mm->context.id);
  86         }
  87
  88         return res;
  89 }
  90
  91 static long read_ldt_from_host(void __user * ptr, unsigned long bytecount)
  92 {
  93         int res, n;
  94         struct ptrace_ldt ptrace_ldt = (struct ptrace_ldt) {
  95                         .func = 0,
  96                         .bytecount = bytecount,
  97                         .ptr = kmalloc(bytecount, GFP_KERNEL)};
  98         u32 cpu;
  99
 100         if (ptrace_ldt.ptr == NULL)
 101                 return -ENOMEM;
 102
 103         /*
 104          * This is called from sys_modify_ldt only, so userspace_pid gives
 105          * us the right number
 106          */
 107
 108         cpu = get_cpu();
 109         res = os_ptrace_ldt(userspace_pid[cpu], 0, (unsigned long) &ptrace_ldt);
 110         put_cpu();
 111         if (res < 0)
 112                 goto out;
 113
 114         n = copy_to_user(ptr, ptrace_ldt.ptr, res);
 115         if (n != 0)
 116                 res = -EFAULT;
 117
 118   out:
 119         kfree(ptrace_ldt.ptr);
 120
 121         return res;
 122 }
 123
 124 /*
 125  * In skas mode, we hold our own ldt data in UML.
 126  * Thus, the code implementing sys_modify_ldt_skas
 127  * is very similar to (and mostly stolen from) sys_modify_ldt
 128  * for arch/i386/kernel/ldt.c
 129  * The routines copied and modified in part are:
 130  * - read_ldt
 131  * - read_default_ldt
 132  * - write_ldt
 133  * - sys_modify_ldt_skas
 134  */
 135
 136 static int read_ldt(void __user * ptr, unsigned long bytecount)
 137 {
 138         int i, err = 0;
 139         unsigned long size;
 140         uml_ldt_t * ldt = &current->mm->context.ldt;
 141
 142         if (!ldt->entry_count)
 143                 goto out;
 144         if (bytecount > LDT_ENTRY_SIZE*LDT_ENTRIES)
 145                 bytecount = LDT_ENTRY_SIZE*LDT_ENTRIES;
 146         err = bytecount;
 147
 148         if (ptrace_ldt)
 149                 return read_ldt_from_host(ptr, bytecount);
 150
 151         mutex_lock(&ldt->lock);
 152         if (ldt->entry_count <= LDT_DIRECT_ENTRIES) {
 153                 size = LDT_ENTRY_SIZE*LDT_DIRECT_ENTRIES;
 154                 if (size > bytecount)
 155                         size = bytecount;
 156                 if (copy_to_user(ptr, ldt->u.entries, size))
 157                         err = -EFAULT;
 158                 bytecount -= size;
 159                 ptr += size;
 160         }
 161         else {
 162                 for (i=0; i<ldt->entry_count/LDT_ENTRIES_PER_PAGE && bytecount;
 163                      i++) {
 164                         size = PAGE_SIZE;
 165                         if (size > bytecount)
 166                                 size = bytecount;
 167                         if (copy_to_user(ptr, ldt->u.pages[i], size)) {
 168                                 err = -EFAULT;
 169                                 break;
 170                         }
 171                         bytecount -= size;
 172                         ptr += size;
 173                 }
 174         }
 175         mutex_unlock(&ldt->lock);
 176
 177         if (bytecount == 0 || err == -EFAULT)
 178                 goto out;
 179
 180         if (clear_user(ptr, bytecount))
 181                 err = -EFAULT;
 182
 183 out:
 184         return err;
 185 }
 186
 187 static int read_default_ldt(void __user * ptr, unsigned long bytecount)
 188 {
 189         int err;
 190
 191         if (bytecount > 5*LDT_ENTRY_SIZE)
 192                 bytecount = 5*LDT_ENTRY_SIZE;
 193
 194         err = bytecount;
 195         /*
 196          * UML doesn't support lcall7 and lcall27.
 197          * So, we don't really have a default ldt, but emulate
 198          * an empty ldt of common host default ldt size.
 199          */
 200         if (clear_user(ptr, bytecount))
 201                 err = -EFAULT;
 202
 203         return err;
 204 }
 205
 206 static int write_ldt(void __user * ptr, unsigned long bytecount, int func)
 207 {
 208         uml_ldt_t * ldt = &current->mm->context.ldt;
 209         struct mm_id * mm_idp = &current->mm->context.id;
 210         int i, err;
 211         struct user_desc ldt_info;
 212         struct ldt_entry entry0, *ldt_p;
 213         void *addr = NULL;
 214
 215         err = -EINVAL;
 216         if (bytecount != sizeof(ldt_info))
 217                 goto out;
 218         err = -EFAULT;
 219         if (copy_from_user(&ldt_info, ptr, sizeof(ldt_info)))
 220                 goto out;
 221
 222         err = -EINVAL;
 223         if (ldt_info.entry_number >= LDT_ENTRIES)
 224                 goto out;
 225         if (ldt_info.contents == 3) {
 226                 if (func == 1)
 227                         goto out;
 228                 if (ldt_info.seg_not_present == 0)
 229                         goto out;
 230         }
 231
 232         if (!ptrace_ldt)
 233                 mutex_lock(&ldt->lock);
 234
 235         err = write_ldt_entry(mm_idp, func, &ldt_info, &addr, 1);
 236         if (err)
 237                 goto out_unlock;
 238         else if (ptrace_ldt) {
 239                 /* With PTRACE_LDT available, this is used as a flag only */
 240                 ldt->entry_count = 1;
 241                 goto out;
 242         }
 243
 244         if (ldt_info.entry_number >= ldt->entry_count &&
 245             ldt_info.entry_number >= LDT_DIRECT_ENTRIES) {
 246                 for (i=ldt->entry_count/LDT_ENTRIES_PER_PAGE;
 247                      i*LDT_ENTRIES_PER_PAGE <= ldt_info.entry_number;
 248                      i++) {
 249                         if (i == 0)
 250                                 memcpy(&entry0, ldt->u.entries,
 251                                        sizeof(entry0));
 252                         ldt->u.pages[i] = (struct ldt_entry *)
 253                                 __get_free_page(GFP_KERNEL|__GFP_ZERO);
 254                         if (!ldt->u.pages[i]) {
 255                                 err = -ENOMEM;
 256                                 /* Undo the change in host */
 257                                 memset(&ldt_info, 0, sizeof(ldt_info));
 258                                 write_ldt_entry(mm_idp, 1, &ldt_info, &addr, 1);
 259                                 goto out_unlock;
 260                         }
 261                         if (i == 0) {
 262                                 memcpy(ldt->u.pages[0], &entry0,
 263                                        sizeof(entry0));
 264                                 memcpy(ldt->u.pages[0]+1, ldt->u.entries+1,
 265                                        sizeof(entry0)*(LDT_DIRECT_ENTRIES-1));
 266                         }
 267                         ldt->entry_count = (i + 1) * LDT_ENTRIES_PER_PAGE;
 268                 }
 269         }
 270         if (ldt->entry_count <= ldt_info.entry_number)
 271                 ldt->entry_count = ldt_info.entry_number + 1;
 272
 273         if (ldt->entry_count <= LDT_DIRECT_ENTRIES)
 274                 ldt_p = ldt->u.entries + ldt_info.entry_number;
 275         else
 276                 ldt_p = ldt->u.pages[ldt_info.entry_number/LDT_ENTRIES_PER_PAGE] +
 277                         ldt_info.entry_number%LDT_ENTRIES_PER_PAGE;
 278
 279         if (ldt_info.base_addr == 0 && ldt_info.limit == 0 &&
 280            (func == 1 || LDT_empty(&ldt_info))) {
 281                 ldt_p->a = 0;
 282                 ldt_p->b = 0;
 283         }
 284         else{
 285                 if (func == 1)
 286                         ldt_info.useable = 0;
 287                 ldt_p->a = LDT_entry_a(&ldt_info);
 288                 ldt_p->b = LDT_entry_b(&ldt_info);
 289         }
 290         err = 0;
 291
 292 out_unlock:
 293         mutex_unlock(&ldt->lock);
 294 out:
 295         return err;
 296 }
 297
 298 static long do_modify_ldt_skas(int func, void __user *ptr,
 299                                unsigned long bytecount)
 300 {
 301         int ret = -ENOSYS;
 302
 303         switch (func) {
 304                 case 0:
 305                         ret = read_ldt(ptr, bytecount);
 306                         break;
 307                 case 1:
 308                 case 0x11:
 309                         ret = write_ldt(ptr, bytecount, func);
 310                         break;
 311                 case 2:
 312                         ret = read_default_ldt(ptr, bytecount);
 313                         break;
 314         }
 315         return ret;
 316 }
 317
 318 static DEFINE_SPINLOCK(host_ldt_lock);
 319 static short dummy_list[9] = {0, -1};
 320 static short * host_ldt_entries = NULL;
 321
 322 static void ldt_get_host_info(void)
 323 {
 324         long ret;
 325         struct ldt_entry * ldt;
 326         short *tmp;
 327         int i, size, k, order;
 328
 329         spin_lock(&host_ldt_lock);
 330
 331         if (host_ldt_entries != NULL) {
 332                 spin_unlock(&host_ldt_lock);
 333                 return;
 334         }
 335         host_ldt_entries = dummy_list+1;
 336
 337         spin_unlock(&host_ldt_lock);
 338
 339         for (i = LDT_PAGES_MAX-1, order=0; i; i>>=1, order++)
 340                 ;
 341
 342         ldt = (struct ldt_entry *)
 343               __get_free_pages(GFP_KERNEL|__GFP_ZERO, order);
 344         if (ldt == NULL) {
 345                 printk(KERN_ERR "ldt_get_host_info: couldn't allocate buffer "
 346                        "for host ldt\n");
 347                 return;
 348         }
 349
 350         ret = modify_ldt(0, ldt, (1<<order)*PAGE_SIZE);
 351         if (ret < 0) {
 352                 printk(KERN_ERR "ldt_get_host_info: couldn't read host ldt\n");
 353                 goto out_free;
 354         }
 355         if (ret == 0) {
 356                 /* default_ldt is active, simply write an empty entry 0 */
 357                 host_ldt_entries = dummy_list;
 358                 goto out_free;
 359         }
 360
 361         for (i=0, size=0; i<ret/LDT_ENTRY_SIZE; i++) {
 362                 if (ldt[i].a != 0 || ldt[i].b != 0)
 363                         size++;
 364         }
 365
 366         if (size < ARRAY_SIZE(dummy_list))
 367                 host_ldt_entries = dummy_list;
 368         else {
 369                 size = (size + 1) * sizeof(dummy_list[0]);
 370                 tmp = kmalloc(size, GFP_KERNEL);
 371                 if (tmp == NULL) {
 372                         printk(KERN_ERR "ldt_get_host_info: couldn't allocate "
 373                                "host ldt list\n");
 374                         goto out_free;
 375                 }
 376                 host_ldt_entries = tmp;
 377         }
 378
 379         for (i=0, k=0; i<ret/LDT_ENTRY_SIZE; i++) {
 380                 if (ldt[i].a != 0 || ldt[i].b != 0)
 381                         host_ldt_entries[k++] = i;
 382         }
 383         host_ldt_entries[k] = -1;
 384
 385 out_free:
 386         free_pages((unsigned long)ldt, order);
 387 }
 388
 389 long init_new_ldt(struct mm_context *new_mm, struct mm_context *from_mm)
 390 {
 391         struct user_desc desc;
 392         short * num_p;
 393         int i;
 394         long page, err=0;
 395         void *addr = NULL;
 396         struct proc_mm_op copy;
 397
 398
 399         if (!ptrace_ldt)
 400                 mutex_init(&new_mm->ldt.lock);
 401
 402         if (!from_mm) {
 403                 memset(&desc, 0, sizeof(desc));
 404                 /*
 405                  * We have to initialize a clean ldt.
 406                  */
 407                 if (proc_mm) {
 408                         /*
 409                          * If the new mm was created using proc_mm, host's
 410                          * default-ldt currently is assigned, which normally
 411                          * contains the call-gates for lcall7 and lcall27.
 412                          * To remove these gates, we simply write an empty
 413                          * entry as number 0 to the host.
 414                          */
 415                         err = write_ldt_entry(&new_mm->id, 1, &desc, &addr, 1);
 416                 }
 417                 else{
 418                         /*
 419                          * Now we try to retrieve info about the ldt, we
 420                          * inherited from the host. All ldt-entries found
 421                          * will be reset in the following loop
 422                          */
 423                         ldt_get_host_info();
 424                         for (num_p=host_ldt_entries; *num_p != -1; num_p++) {
 425                                 desc.entry_number = *num_p;
 426                                 err = write_ldt_entry(&new_mm->id, 1, &desc,
 427                                                       &addr, *(num_p + 1) == -1);
 428                                 if (err)
 429                                         break;
 430                         }
 431                 }
 432                 new_mm->ldt.entry_count = 0;
 433
 434                 goto out;
 435         }
 436
 437         if (proc_mm) {
 438                 /*
 439                  * We have a valid from_mm, so we now have to copy the LDT of
 440                  * from_mm to new_mm, because using proc_mm an new mm with
 441                  * an empty/default LDT was created in new_mm()
 442                  */
 443                 copy = ((struct proc_mm_op) { .op       = MM_COPY_SEGMENTS,
 444                                               .u        =
 445                                               { .copy_segments =
 446                                                         from_mm->id.u.mm_fd } } );
 447                 i = os_write_file(new_mm->id.u.mm_fd, &copy, sizeof(copy));
 448                 if (i != sizeof(copy))
 449                         printk(KERN_ERR "new_mm : /proc/mm copy_segments "
 450                                "failed, err = %d\n", -i);
 451         }
 452
 453         if (!ptrace_ldt) {
 454                 /*
 455                  * Our local LDT is used to supply the data for
 456                  * modify_ldt(READLDT), if PTRACE_LDT isn't available,
 457                  * i.e., we have to use the stub for modify_ldt, which
 458                  * can't handle the big read buffer of up to 64kB.
 459                  */
 460                 mutex_lock(&from_mm->ldt.lock);
 461                 if (from_mm->ldt.entry_count <= LDT_DIRECT_ENTRIES)
 462                         memcpy(new_mm->ldt.u.entries, from_mm->ldt.u.entries,
 463                                sizeof(new_mm->ldt.u.entries));
 464                 else {
 465                         i = from_mm->ldt.entry_count / LDT_ENTRIES_PER_PAGE;
 466                         while (i-->0) {
 467                                 page = __get_free_page(GFP_KERNEL|__GFP_ZERO);
 468                                 if (!page) {
 469                                         err = -ENOMEM;
 470                                         break;
 471                                 }
 472                                 new_mm->ldt.u.pages[i] =
 473                                         (struct ldt_entry *) page;
 474                                 memcpy(new_mm->ldt.u.pages[i],
 475                                        from_mm->ldt.u.pages[i], PAGE_SIZE);
 476                         }
 477                 }
 478                 new_mm->ldt.entry_count = from_mm->ldt.entry_count;
 479                 mutex_unlock(&from_mm->ldt.lock);
 480         }
 481
 482     out:
 483         return err;
 484 }
 485
 486
 487 void free_ldt(struct mm_context *mm)
 488 {
 489         int i;
 490
 491         if (!ptrace_ldt && mm->ldt.entry_count > LDT_DIRECT_ENTRIES) {
 492                 i = mm->ldt.entry_count / LDT_ENTRIES_PER_PAGE;
 493                 while (i-- > 0)
 494                         free_page((long) mm->ldt.u.pages[i]);
 495         }
 496         mm->ldt.entry_count = 0;
 497 }
 498
 499 int sys_modify_ldt(int func, void __user *ptr, unsigned long bytecount)
 500 {
 501         return do_modify_ldt_skas(func, ptr, bytecount);
 502 }