git.oblomov.eu Git - linux-2.6/blob - arch/um/sys-i386/ldt.c

   1 /*
   2  * Copyright (C) 2001, 2002 Jeff Dike (jdike@karaya.com)
   3  * Licensed under the GPL
   4  */
   5
   6 #include "linux/stddef.h"
   7 #include "linux/config.h"
   8 #include "linux/sched.h"
   9 #include "linux/slab.h"
  10 #include "linux/types.h"
  11 #include "linux/errno.h"
  12 #include "asm/uaccess.h"
  13 #include "asm/smp.h"
  14 #include "asm/ldt.h"
  15 #include "asm/unistd.h"
  16 #include "choose-mode.h"
  17 #include "kern.h"
  18 #include "mode_kern.h"
  19 #include "os.h"
  20
  21 extern int modify_ldt(int func, void *ptr, unsigned long bytecount);
  22
  23 #ifdef CONFIG_MODE_TT
  24
  25 static long do_modify_ldt_tt(int func, void __user *ptr,
  26                               unsigned long bytecount)
  27 {
  28         struct user_desc info;
  29         int res = 0;
  30         void *buf = NULL;
  31         void *p = NULL; /* What we pass to host. */
  32
  33         switch(func){
  34         case 1:
  35         case 0x11: /* write_ldt */
  36                 /* Do this check now to avoid overflows. */
  37                 if (bytecount != sizeof(struct user_desc)) {
  38                         res = -EINVAL;
  39                         goto out;
  40                 }
  41
  42                 if(copy_from_user(&info, ptr, sizeof(info))) {
  43                         res = -EFAULT;
  44                         goto out;
  45                 }
  46
  47                 p = &info;
  48                 break;
  49         case 0:
  50         case 2: /* read_ldt */
  51
  52                 /* The use of info avoids kmalloc on the write case, not on the
  53                  * read one. */
  54                 buf = kmalloc(bytecount, GFP_KERNEL);
  55                 if (!buf) {
  56                         res = -ENOMEM;
  57                         goto out;
  58                 }
  59                 p = buf;
  60                 break;
  61         default:
  62                 res = -ENOSYS;
  63                 goto out;
  64         }
  65
  66         res = modify_ldt(func, p, bytecount);
  67         if(res < 0)
  68                 goto out;
  69
  70         switch(func){
  71         case 0:
  72         case 2:
  73                 /* Modify_ldt was for reading and returned the number of read
  74                  * bytes.*/
  75                 if(copy_to_user(ptr, p, res))
  76                         res = -EFAULT;
  77                 break;
  78         }
  79
  80 out:
  81         kfree(buf);
  82         return res;
  83 }
  84
  85 #endif
  86
  87 #ifdef CONFIG_MODE_SKAS
  88
  89 #include "skas.h"
  90 #include "skas_ptrace.h"
  91 #include "asm/mmu_context.h"
  92 #include "proc_mm.h"
  93
  94 long write_ldt_entry(struct mm_id * mm_idp, int func, struct user_desc * desc,
  95                      void **addr, int done)
  96 {
  97         long res;
  98
  99         if(proc_mm){
 100                 /* This is a special handling for the case, that the mm to
 101                  * modify isn't current->active_mm.
 102                  * If this is called directly by modify_ldt,
 103                  *     (current->active_mm->context.skas.u == mm_idp)
 104                  * will be true. So no call to switch_mm_skas(mm_idp) is done.
 105                  * If this is called in case of init_new_ldt or PTRACE_LDT,
 106                  * mm_idp won't belong to current->active_mm, but child->mm.
 107                  * So we need to switch child's mm into our userspace, then
 108                  * later switch back.
 109                  *
 110                  * Note: I'm unshure: should interrupts be disabled here?
 111                  */
 112                 if(!current->active_mm || current->active_mm == &init_mm ||
 113                    mm_idp != &current->active_mm->context.skas.id)
 114                         switch_mm_skas(mm_idp);
 115         }
 116
 117         if(ptrace_ldt) {
 118                 struct ptrace_ldt ldt_op = (struct ptrace_ldt) {
 119                         .func = func,
 120                         .ptr = desc,
 121                         .bytecount = sizeof(*desc)};
 122                 u32 cpu;
 123                 int pid;
 124
 125                 if(!proc_mm)
 126                         pid = mm_idp->u.pid;
 127                 else {
 128                         cpu = get_cpu();
 129                         pid = userspace_pid[cpu];
 130                 }
 131
 132                 res = ptrace(PTRACE_LDT, pid, 0, (unsigned long) &ldt_op);
 133                 if(res)
 134                         res = errno;
 135
 136                 if(proc_mm)
 137                         put_cpu();
 138         }
 139         else {
 140                 void *stub_addr;
 141                 res = syscall_stub_data(mm_idp, (unsigned long *)desc,
 142                                         (sizeof(*desc) + sizeof(long) - 1) &
 143                                             ~(sizeof(long) - 1),
 144                                         addr, &stub_addr);
 145                 if(!res){
 146                         unsigned long args[] = { func,
 147                                                  (unsigned long)stub_addr,
 148                                                  sizeof(*desc),
 149                                                  0, 0, 0 };
 150                         res = run_syscall_stub(mm_idp, __NR_modify_ldt, args,
 151                                                0, addr, done);
 152                 }
 153         }
 154
 155         if(proc_mm){
 156                 /* This is the second part of special handling, that makes
 157                  * PTRACE_LDT possible to implement.
 158                  */
 159                 if(current->active_mm && current->active_mm != &init_mm &&
 160                    mm_idp != &current->active_mm->context.skas.id)
 161                         switch_mm_skas(&current->active_mm->context.skas.id);
 162         }
 163
 164         return res;
 165 }
 166
 167 static long read_ldt_from_host(void __user * ptr, unsigned long bytecount)
 168 {
 169         int res, n;
 170         struct ptrace_ldt ptrace_ldt = (struct ptrace_ldt) {
 171                         .func = 0,
 172                         .bytecount = bytecount,
 173                         .ptr = (void *)kmalloc(bytecount, GFP_KERNEL)};
 174         u32 cpu;
 175
 176         if(ptrace_ldt.ptr == NULL)
 177                 return -ENOMEM;
 178
 179         /* This is called from sys_modify_ldt only, so userspace_pid gives
 180          * us the right number
 181          */
 182
 183         cpu = get_cpu();
 184         res = ptrace(PTRACE_LDT, userspace_pid[cpu], 0,
 185                      (unsigned long) &ptrace_ldt);
 186         put_cpu();
 187         if(res < 0)
 188                 goto out;
 189
 190         n = copy_to_user(ptr, ptrace_ldt.ptr, res);
 191         if(n != 0)
 192                 res = -EFAULT;
 193
 194   out:
 195         kfree(ptrace_ldt.ptr);
 196
 197         return res;
 198 }
 199
 200 /*
 201  * In skas mode, we hold our own ldt data in UML.
 202  * Thus, the code implementing sys_modify_ldt_skas
 203  * is very similar to (and mostly stolen from) sys_modify_ldt
 204  * for arch/i386/kernel/ldt.c
 205  * The routines copied and modified in part are:
 206  * - read_ldt
 207  * - read_default_ldt
 208  * - write_ldt
 209  * - sys_modify_ldt_skas
 210  */
 211
 212 static int read_ldt(void __user * ptr, unsigned long bytecount)
 213 {
 214         int i, err = 0;
 215         unsigned long size;
 216         uml_ldt_t * ldt = &current->mm->context.skas.ldt;
 217
 218         if(!ldt->entry_count)
 219                 goto out;
 220         if(bytecount > LDT_ENTRY_SIZE*LDT_ENTRIES)
 221                 bytecount = LDT_ENTRY_SIZE*LDT_ENTRIES;
 222         err = bytecount;
 223
 224         if(ptrace_ldt){
 225                 return read_ldt_from_host(ptr, bytecount);
 226         }
 227
 228         down(&ldt->semaphore);
 229         if(ldt->entry_count <= LDT_DIRECT_ENTRIES){
 230                 size = LDT_ENTRY_SIZE*LDT_DIRECT_ENTRIES;
 231                 if(size > bytecount)
 232                         size = bytecount;
 233                 if(copy_to_user(ptr, ldt->u.entries, size))
 234                         err = -EFAULT;
 235                 bytecount -= size;
 236                 ptr += size;
 237         }
 238         else {
 239                 for(i=0; i<ldt->entry_count/LDT_ENTRIES_PER_PAGE && bytecount;
 240                          i++){
 241                         size = PAGE_SIZE;
 242                         if(size > bytecount)
 243                                 size = bytecount;
 244                         if(copy_to_user(ptr, ldt->u.pages[i], size)){
 245                                 err = -EFAULT;
 246                                 break;
 247                         }
 248                         bytecount -= size;
 249                         ptr += size;
 250                 }
 251         }
 252         up(&ldt->semaphore);
 253
 254         if(bytecount == 0 || err == -EFAULT)
 255                 goto out;
 256
 257         if(clear_user(ptr, bytecount))
 258                 err = -EFAULT;
 259
 260 out:
 261         return err;
 262 }
 263
 264 static int read_default_ldt(void __user * ptr, unsigned long bytecount)
 265 {
 266         int err;
 267
 268         if(bytecount > 5*LDT_ENTRY_SIZE)
 269                 bytecount = 5*LDT_ENTRY_SIZE;
 270
 271         err = bytecount;
 272         /* UML doesn't support lcall7 and lcall27.
 273          * So, we don't really have a default ldt, but emulate
 274          * an empty ldt of common host default ldt size.
 275          */
 276         if(clear_user(ptr, bytecount))
 277                 err = -EFAULT;
 278
 279         return err;
 280 }
 281
 282 static int write_ldt(void __user * ptr, unsigned long bytecount, int func)
 283 {
 284         uml_ldt_t * ldt = &current->mm->context.skas.ldt;
 285         struct mm_id * mm_idp = &current->mm->context.skas.id;
 286         int i, err;
 287         struct user_desc ldt_info;
 288         struct ldt_entry entry0, *ldt_p;
 289         void *addr = NULL;
 290
 291         err = -EINVAL;
 292         if(bytecount != sizeof(ldt_info))
 293                 goto out;
 294         err = -EFAULT;
 295         if(copy_from_user(&ldt_info, ptr, sizeof(ldt_info)))
 296                 goto out;
 297
 298         err = -EINVAL;
 299         if(ldt_info.entry_number >= LDT_ENTRIES)
 300                 goto out;
 301         if(ldt_info.contents == 3){
 302                 if (func == 1)
 303                         goto out;
 304                 if (ldt_info.seg_not_present == 0)
 305                         goto out;
 306         }
 307
 308         if(!ptrace_ldt)
 309                 down(&ldt->semaphore);
 310
 311         err = write_ldt_entry(mm_idp, func, &ldt_info, &addr, 1);
 312         if(err)
 313                 goto out_unlock;
 314         else if(ptrace_ldt) {
 315         /* With PTRACE_LDT available, this is used as a flag only */
 316                 ldt->entry_count = 1;
 317                 goto out;
 318         }
 319
 320         if(ldt_info.entry_number >= ldt->entry_count &&
 321            ldt_info.entry_number >= LDT_DIRECT_ENTRIES){
 322                 for(i=ldt->entry_count/LDT_ENTRIES_PER_PAGE;
 323                     i*LDT_ENTRIES_PER_PAGE <= ldt_info.entry_number;
 324                     i++){
 325                         if(i == 0)
 326                                 memcpy(&entry0, ldt->u.entries,
 327                                        sizeof(entry0));
 328                         ldt->u.pages[i] = (struct ldt_entry *)
 329                                 __get_free_page(GFP_KERNEL|__GFP_ZERO);
 330                         if(!ldt->u.pages[i]){
 331                                 err = -ENOMEM;
 332                                 /* Undo the change in host */
 333                                 memset(&ldt_info, 0, sizeof(ldt_info));
 334                                 write_ldt_entry(mm_idp, 1, &ldt_info, &addr, 1);
 335                                 goto out_unlock;
 336                         }
 337                         if(i == 0) {
 338                                 memcpy(ldt->u.pages[0], &entry0,
 339                                        sizeof(entry0));
 340                                 memcpy(ldt->u.pages[0]+1, ldt->u.entries+1,
 341                                        sizeof(entry0)*(LDT_DIRECT_ENTRIES-1));
 342                         }
 343                         ldt->entry_count = (i + 1) * LDT_ENTRIES_PER_PAGE;
 344                 }
 345         }
 346         if(ldt->entry_count <= ldt_info.entry_number)
 347                 ldt->entry_count = ldt_info.entry_number + 1;
 348
 349         if(ldt->entry_count <= LDT_DIRECT_ENTRIES)
 350                 ldt_p = ldt->u.entries + ldt_info.entry_number;
 351         else
 352                 ldt_p = ldt->u.pages[ldt_info.entry_number/LDT_ENTRIES_PER_PAGE] +
 353                         ldt_info.entry_number%LDT_ENTRIES_PER_PAGE;
 354
 355         if(ldt_info.base_addr == 0 && ldt_info.limit == 0 &&
 356            (func == 1 || LDT_empty(&ldt_info))){
 357                 ldt_p->a = 0;
 358                 ldt_p->b = 0;
 359         }
 360         else{
 361                 if (func == 1)
 362                         ldt_info.useable = 0;
 363                 ldt_p->a = LDT_entry_a(&ldt_info);
 364                 ldt_p->b = LDT_entry_b(&ldt_info);
 365         }
 366         err = 0;
 367
 368 out_unlock:
 369         up(&ldt->semaphore);
 370 out:
 371         return err;
 372 }
 373
 374 static long do_modify_ldt_skas(int func, void __user *ptr,
 375                                unsigned long bytecount)
 376 {
 377         int ret = -ENOSYS;
 378
 379         switch (func) {
 380                 case 0:
 381                         ret = read_ldt(ptr, bytecount);
 382                         break;
 383                 case 1:
 384                 case 0x11:
 385                         ret = write_ldt(ptr, bytecount, func);
 386                         break;
 387                 case 2:
 388                         ret = read_default_ldt(ptr, bytecount);
 389                         break;
 390         }
 391         return ret;
 392 }
 393
 394 short dummy_list[9] = {0, -1};
 395 short * host_ldt_entries = NULL;
 396
 397 void ldt_get_host_info(void)
 398 {
 399         long ret;
 400         struct ldt_entry * ldt;
 401         int i, size, k, order;
 402
 403         host_ldt_entries = dummy_list+1;
 404
 405         for(i = LDT_PAGES_MAX-1, order=0; i; i>>=1, order++);
 406
 407         ldt = (struct ldt_entry *)
 408               __get_free_pages(GFP_KERNEL|__GFP_ZERO, order);
 409         if(ldt == NULL) {
 410                 printk("ldt_get_host_info: couldn't allocate buffer for host ldt\n");
 411                 return;
 412         }
 413
 414         ret = modify_ldt(0, ldt, (1<<order)*PAGE_SIZE);
 415         if(ret < 0) {
 416                 printk("ldt_get_host_info: couldn't read host ldt\n");
 417                 goto out_free;
 418         }
 419         if(ret == 0) {
 420                 /* default_ldt is active, simply write an empty entry 0 */
 421                 host_ldt_entries = dummy_list;
 422                 goto out_free;
 423         }
 424
 425         for(i=0, size=0; i<ret/LDT_ENTRY_SIZE; i++){
 426                 if(ldt[i].a != 0 || ldt[i].b != 0)
 427                         size++;
 428         }
 429
 430         if(size < sizeof(dummy_list)/sizeof(dummy_list[0])) {
 431                 host_ldt_entries = dummy_list;
 432         }
 433         else {
 434                 size = (size + 1) * sizeof(dummy_list[0]);
 435                 host_ldt_entries = (short *)kmalloc(size, GFP_KERNEL);
 436                 if(host_ldt_entries == NULL) {
 437                         printk("ldt_get_host_info: couldn't allocate host ldt list\n");
 438                         goto out_free;
 439                 }
 440         }
 441
 442         for(i=0, k=0; i<ret/LDT_ENTRY_SIZE; i++){
 443                 if(ldt[i].a != 0 || ldt[i].b != 0) {
 444                         host_ldt_entries[k++] = i;
 445                 }
 446         }
 447         host_ldt_entries[k] = -1;
 448
 449 out_free:
 450         free_pages((unsigned long)ldt, order);
 451 }
 452
 453 long init_new_ldt(struct mmu_context_skas * new_mm,
 454                   struct mmu_context_skas * from_mm)
 455 {
 456         struct user_desc desc;
 457         short * num_p;
 458         int i;
 459         long page, err=0;
 460         void *addr = NULL;
 461         struct proc_mm_op copy;
 462
 463
 464         if(!ptrace_ldt)
 465                 init_MUTEX(&new_mm->ldt.semaphore);
 466
 467         if(!from_mm){
 468                 memset(&desc, 0, sizeof(desc));
 469                 /*
 470                  * We have to initialize a clean ldt.
 471                  */
 472                 if(proc_mm) {
 473                         /*
 474                          * If the new mm was created using proc_mm, host's
 475                          * default-ldt currently is assigned, which normally
 476                          * contains the call-gates for lcall7 and lcall27.
 477                          * To remove these gates, we simply write an empty
 478                          * entry as number 0 to the host.
 479                          */
 480                         err = write_ldt_entry(&new_mm->id, 1, &desc,
 481                                               &addr, 1);
 482                 }
 483                 else{
 484                         /*
 485                          * Now we try to retrieve info about the ldt, we
 486                          * inherited from the host. All ldt-entries found
 487                          * will be reset in the following loop
 488                          */
 489                         if(host_ldt_entries == NULL)
 490                                 ldt_get_host_info();
 491                         for(num_p=host_ldt_entries; *num_p != -1; num_p++){
 492                                 desc.entry_number = *num_p;
 493                                 err = write_ldt_entry(&new_mm->id, 1, &desc,
 494                                                       &addr, *(num_p + 1) == -1);
 495                                 if(err)
 496                                         break;
 497                         }
 498                 }
 499                 new_mm->ldt.entry_count = 0;
 500
 501                 goto out;
 502         }
 503
 504         if(proc_mm){
 505                 /* We have a valid from_mm, so we now have to copy the LDT of
 506                  * from_mm to new_mm, because using proc_mm an new mm with
 507                  * an empty/default LDT was created in new_mm()
 508                  */
 509                 copy = ((struct proc_mm_op) { .op       = MM_COPY_SEGMENTS,
 510                                               .u        =
 511                                               { .copy_segments =
 512                                                         from_mm->id.u.mm_fd } } );
 513                 i = os_write_file(new_mm->id.u.mm_fd, &copy, sizeof(copy));
 514                 if(i != sizeof(copy))
 515                         printk("new_mm : /proc/mm copy_segments failed, "
 516                                "err = %d\n", -i);
 517         }
 518
 519         if(!ptrace_ldt) {
 520                 /* Our local LDT is used to supply the data for
 521                  * modify_ldt(READLDT), if PTRACE_LDT isn't available,
 522                  * i.e., we have to use the stub for modify_ldt, which
 523                  * can't handle the big read buffer of up to 64kB.
 524                  */
 525                 down(&from_mm->ldt.semaphore);
 526                 if(from_mm->ldt.entry_count <= LDT_DIRECT_ENTRIES){
 527                         memcpy(new_mm->ldt.u.entries, from_mm->ldt.u.entries,
 528                                sizeof(new_mm->ldt.u.entries));
 529                 }
 530                 else{
 531                         i = from_mm->ldt.entry_count / LDT_ENTRIES_PER_PAGE;
 532                         while(i-->0){
 533                                 page = __get_free_page(GFP_KERNEL|__GFP_ZERO);
 534                                 if (!page){
 535                                         err = -ENOMEM;
 536                                         break;
 537                                 }
 538                                 new_mm->ldt.u.pages[i] =
 539                                         (struct ldt_entry *) page;
 540                                 memcpy(new_mm->ldt.u.pages[i],
 541                                        from_mm->ldt.u.pages[i], PAGE_SIZE);
 542                         }
 543                 }
 544                 new_mm->ldt.entry_count = from_mm->ldt.entry_count;
 545                 up(&from_mm->ldt.semaphore);
 546         }
 547
 548     out:
 549         return err;
 550 }
 551
 552
 553 void free_ldt(struct mmu_context_skas * mm)
 554 {
 555         int i;
 556
 557         if(!ptrace_ldt && mm->ldt.entry_count > LDT_DIRECT_ENTRIES){
 558                 i = mm->ldt.entry_count / LDT_ENTRIES_PER_PAGE;
 559                 while(i-- > 0){
 560                         free_page((long )mm->ldt.u.pages[i]);
 561                 }
 562         }
 563         mm->ldt.entry_count = 0;
 564 }
 565 #endif
 566
 567 int sys_modify_ldt(int func, void __user *ptr, unsigned long bytecount)
 568 {
 569         return(CHOOSE_MODE_PROC(do_modify_ldt_tt, do_modify_ldt_skas, func,
 570                                 ptr, bytecount));
 571 }