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 unsure: 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 = os_ptrace_ldt(pid, 0, (unsigned long) &ldt_op);
 133
 134                 if(proc_mm)
 135                         put_cpu();
 136         }
 137         else {
 138                 void *stub_addr;
 139                 res = syscall_stub_data(mm_idp, (unsigned long *)desc,
 140                                         (sizeof(*desc) + sizeof(long) - 1) &
 141                                             ~(sizeof(long) - 1),
 142                                         addr, &stub_addr);
 143                 if(!res){
 144                         unsigned long args[] = { func,
 145                                                  (unsigned long)stub_addr,
 146                                                  sizeof(*desc),
 147                                                  0, 0, 0 };
 148                         res = run_syscall_stub(mm_idp, __NR_modify_ldt, args,
 149                                                0, addr, done);
 150                 }
 151         }
 152
 153         if(proc_mm){
 154                 /* This is the second part of special handling, that makes
 155                  * PTRACE_LDT possible to implement.
 156                  */
 157                 if(current->active_mm && current->active_mm != &init_mm &&
 158                    mm_idp != &current->active_mm->context.skas.id)
 159                         switch_mm_skas(&current->active_mm->context.skas.id);
 160         }
 161
 162         return res;
 163 }
 164
 165 static long read_ldt_from_host(void __user * ptr, unsigned long bytecount)
 166 {
 167         int res, n;
 168         struct ptrace_ldt ptrace_ldt = (struct ptrace_ldt) {
 169                         .func = 0,
 170                         .bytecount = bytecount,
 171                         .ptr = (void *)kmalloc(bytecount, GFP_KERNEL)};
 172         u32 cpu;
 173
 174         if(ptrace_ldt.ptr == NULL)
 175                 return -ENOMEM;
 176
 177         /* This is called from sys_modify_ldt only, so userspace_pid gives
 178          * us the right number
 179          */
 180
 181         cpu = get_cpu();
 182         res = os_ptrace_ldt(userspace_pid[cpu], 0, (unsigned long) &ptrace_ldt);
 183         put_cpu();
 184         if(res < 0)
 185                 goto out;
 186
 187         n = copy_to_user(ptr, ptrace_ldt.ptr, res);
 188         if(n != 0)
 189                 res = -EFAULT;
 190
 191   out:
 192         kfree(ptrace_ldt.ptr);
 193
 194         return res;
 195 }
 196
 197 /*
 198  * In skas mode, we hold our own ldt data in UML.
 199  * Thus, the code implementing sys_modify_ldt_skas
 200  * is very similar to (and mostly stolen from) sys_modify_ldt
 201  * for arch/i386/kernel/ldt.c
 202  * The routines copied and modified in part are:
 203  * - read_ldt
 204  * - read_default_ldt
 205  * - write_ldt
 206  * - sys_modify_ldt_skas
 207  */
 208
 209 static int read_ldt(void __user * ptr, unsigned long bytecount)
 210 {
 211         int i, err = 0;
 212         unsigned long size;
 213         uml_ldt_t * ldt = &current->mm->context.skas.ldt;
 214
 215         if(!ldt->entry_count)
 216                 goto out;
 217         if(bytecount > LDT_ENTRY_SIZE*LDT_ENTRIES)
 218                 bytecount = LDT_ENTRY_SIZE*LDT_ENTRIES;
 219         err = bytecount;
 220
 221         if(ptrace_ldt){
 222                 return read_ldt_from_host(ptr, bytecount);
 223         }
 224
 225         down(&ldt->semaphore);
 226         if(ldt->entry_count <= LDT_DIRECT_ENTRIES){
 227                 size = LDT_ENTRY_SIZE*LDT_DIRECT_ENTRIES;
 228                 if(size > bytecount)
 229                         size = bytecount;
 230                 if(copy_to_user(ptr, ldt->u.entries, size))
 231                         err = -EFAULT;
 232                 bytecount -= size;
 233                 ptr += size;
 234         }
 235         else {
 236                 for(i=0; i<ldt->entry_count/LDT_ENTRIES_PER_PAGE && bytecount;
 237                          i++){
 238                         size = PAGE_SIZE;
 239                         if(size > bytecount)
 240                                 size = bytecount;
 241                         if(copy_to_user(ptr, ldt->u.pages[i], size)){
 242                                 err = -EFAULT;
 243                                 break;
 244                         }
 245                         bytecount -= size;
 246                         ptr += size;
 247                 }
 248         }
 249         up(&ldt->semaphore);
 250
 251         if(bytecount == 0 || err == -EFAULT)
 252                 goto out;
 253
 254         if(clear_user(ptr, bytecount))
 255                 err = -EFAULT;
 256
 257 out:
 258         return err;
 259 }
 260
 261 static int read_default_ldt(void __user * ptr, unsigned long bytecount)
 262 {
 263         int err;
 264
 265         if(bytecount > 5*LDT_ENTRY_SIZE)
 266                 bytecount = 5*LDT_ENTRY_SIZE;
 267
 268         err = bytecount;
 269         /* UML doesn't support lcall7 and lcall27.
 270          * So, we don't really have a default ldt, but emulate
 271          * an empty ldt of common host default ldt size.
 272          */
 273         if(clear_user(ptr, bytecount))
 274                 err = -EFAULT;
 275
 276         return err;
 277 }
 278
 279 static int write_ldt(void __user * ptr, unsigned long bytecount, int func)
 280 {
 281         uml_ldt_t * ldt = &current->mm->context.skas.ldt;
 282         struct mm_id * mm_idp = &current->mm->context.skas.id;
 283         int i, err;
 284         struct user_desc ldt_info;
 285         struct ldt_entry entry0, *ldt_p;
 286         void *addr = NULL;
 287
 288         err = -EINVAL;
 289         if(bytecount != sizeof(ldt_info))
 290                 goto out;
 291         err = -EFAULT;
 292         if(copy_from_user(&ldt_info, ptr, sizeof(ldt_info)))
 293                 goto out;
 294
 295         err = -EINVAL;
 296         if(ldt_info.entry_number >= LDT_ENTRIES)
 297                 goto out;
 298         if(ldt_info.contents == 3){
 299                 if (func == 1)
 300                         goto out;
 301                 if (ldt_info.seg_not_present == 0)
 302                         goto out;
 303         }
 304
 305         if(!ptrace_ldt)
 306                 down(&ldt->semaphore);
 307
 308         err = write_ldt_entry(mm_idp, func, &ldt_info, &addr, 1);
 309         if(err)
 310                 goto out_unlock;
 311         else if(ptrace_ldt) {
 312         /* With PTRACE_LDT available, this is used as a flag only */
 313                 ldt->entry_count = 1;
 314                 goto out;
 315         }
 316
 317         if(ldt_info.entry_number >= ldt->entry_count &&
 318            ldt_info.entry_number >= LDT_DIRECT_ENTRIES){
 319                 for(i=ldt->entry_count/LDT_ENTRIES_PER_PAGE;
 320                     i*LDT_ENTRIES_PER_PAGE <= ldt_info.entry_number;
 321                     i++){
 322                         if(i == 0)
 323                                 memcpy(&entry0, ldt->u.entries,
 324                                        sizeof(entry0));
 325                         ldt->u.pages[i] = (struct ldt_entry *)
 326                                 __get_free_page(GFP_KERNEL|__GFP_ZERO);
 327                         if(!ldt->u.pages[i]){
 328                                 err = -ENOMEM;
 329                                 /* Undo the change in host */
 330                                 memset(&ldt_info, 0, sizeof(ldt_info));
 331                                 write_ldt_entry(mm_idp, 1, &ldt_info, &addr, 1);
 332                                 goto out_unlock;
 333                         }
 334                         if(i == 0) {
 335                                 memcpy(ldt->u.pages[0], &entry0,
 336                                        sizeof(entry0));
 337                                 memcpy(ldt->u.pages[0]+1, ldt->u.entries+1,
 338                                        sizeof(entry0)*(LDT_DIRECT_ENTRIES-1));
 339                         }
 340                         ldt->entry_count = (i + 1) * LDT_ENTRIES_PER_PAGE;
 341                 }
 342         }
 343         if(ldt->entry_count <= ldt_info.entry_number)
 344                 ldt->entry_count = ldt_info.entry_number + 1;
 345
 346         if(ldt->entry_count <= LDT_DIRECT_ENTRIES)
 347                 ldt_p = ldt->u.entries + ldt_info.entry_number;
 348         else
 349                 ldt_p = ldt->u.pages[ldt_info.entry_number/LDT_ENTRIES_PER_PAGE] +
 350                         ldt_info.entry_number%LDT_ENTRIES_PER_PAGE;
 351
 352         if(ldt_info.base_addr == 0 && ldt_info.limit == 0 &&
 353            (func == 1 || LDT_empty(&ldt_info))){
 354                 ldt_p->a = 0;
 355                 ldt_p->b = 0;
 356         }
 357         else{
 358                 if (func == 1)
 359                         ldt_info.useable = 0;
 360                 ldt_p->a = LDT_entry_a(&ldt_info);
 361                 ldt_p->b = LDT_entry_b(&ldt_info);
 362         }
 363         err = 0;
 364
 365 out_unlock:
 366         up(&ldt->semaphore);
 367 out:
 368         return err;
 369 }
 370
 371 static long do_modify_ldt_skas(int func, void __user *ptr,
 372                                unsigned long bytecount)
 373 {
 374         int ret = -ENOSYS;
 375
 376         switch (func) {
 377                 case 0:
 378                         ret = read_ldt(ptr, bytecount);
 379                         break;
 380                 case 1:
 381                 case 0x11:
 382                         ret = write_ldt(ptr, bytecount, func);
 383                         break;
 384                 case 2:
 385                         ret = read_default_ldt(ptr, bytecount);
 386                         break;
 387         }
 388         return ret;
 389 }
 390
 391 short dummy_list[9] = {0, -1};
 392 short * host_ldt_entries = NULL;
 393
 394 void ldt_get_host_info(void)
 395 {
 396         long ret;
 397         struct ldt_entry * ldt;
 398         int i, size, k, order;
 399
 400         host_ldt_entries = dummy_list+1;
 401
 402         for(i = LDT_PAGES_MAX-1, order=0; i; i>>=1, order++);
 403
 404         ldt = (struct ldt_entry *)
 405               __get_free_pages(GFP_KERNEL|__GFP_ZERO, order);
 406         if(ldt == NULL) {
 407                 printk("ldt_get_host_info: couldn't allocate buffer for host ldt\n");
 408                 return;
 409         }
 410
 411         ret = modify_ldt(0, ldt, (1<<order)*PAGE_SIZE);
 412         if(ret < 0) {
 413                 printk("ldt_get_host_info: couldn't read host ldt\n");
 414                 goto out_free;
 415         }
 416         if(ret == 0) {
 417                 /* default_ldt is active, simply write an empty entry 0 */
 418                 host_ldt_entries = dummy_list;
 419                 goto out_free;
 420         }
 421
 422         for(i=0, size=0; i<ret/LDT_ENTRY_SIZE; i++){
 423                 if(ldt[i].a != 0 || ldt[i].b != 0)
 424                         size++;
 425         }
 426
 427         if(size < sizeof(dummy_list)/sizeof(dummy_list[0])) {
 428                 host_ldt_entries = dummy_list;
 429         }
 430         else {
 431                 size = (size + 1) * sizeof(dummy_list[0]);
 432                 host_ldt_entries = (short *)kmalloc(size, GFP_KERNEL);
 433                 if(host_ldt_entries == NULL) {
 434                         printk("ldt_get_host_info: couldn't allocate host ldt list\n");
 435                         goto out_free;
 436                 }
 437         }
 438
 439         for(i=0, k=0; i<ret/LDT_ENTRY_SIZE; i++){
 440                 if(ldt[i].a != 0 || ldt[i].b != 0) {
 441                         host_ldt_entries[k++] = i;
 442                 }
 443         }
 444         host_ldt_entries[k] = -1;
 445
 446 out_free:
 447         free_pages((unsigned long)ldt, order);
 448 }
 449
 450 long init_new_ldt(struct mmu_context_skas * new_mm,
 451                   struct mmu_context_skas * from_mm)
 452 {
 453         struct user_desc desc;
 454         short * num_p;
 455         int i;
 456         long page, err=0;
 457         void *addr = NULL;
 458         struct proc_mm_op copy;
 459
 460
 461         if(!ptrace_ldt)
 462                 init_MUTEX(&new_mm->ldt.semaphore);
 463
 464         if(!from_mm){
 465                 memset(&desc, 0, sizeof(desc));
 466                 /*
 467                  * We have to initialize a clean ldt.
 468                  */
 469                 if(proc_mm) {
 470                         /*
 471                          * If the new mm was created using proc_mm, host's
 472                          * default-ldt currently is assigned, which normally
 473                          * contains the call-gates for lcall7 and lcall27.
 474                          * To remove these gates, we simply write an empty
 475                          * entry as number 0 to the host.
 476                          */
 477                         err = write_ldt_entry(&new_mm->id, 1, &desc,
 478                                               &addr, 1);
 479                 }
 480                 else{
 481                         /*
 482                          * Now we try to retrieve info about the ldt, we
 483                          * inherited from the host. All ldt-entries found
 484                          * will be reset in the following loop
 485                          */
 486                         if(host_ldt_entries == NULL)
 487                                 ldt_get_host_info();
 488                         for(num_p=host_ldt_entries; *num_p != -1; num_p++){
 489                                 desc.entry_number = *num_p;
 490                                 err = write_ldt_entry(&new_mm->id, 1, &desc,
 491                                                       &addr, *(num_p + 1) == -1);
 492                                 if(err)
 493                                         break;
 494                         }
 495                 }
 496                 new_mm->ldt.entry_count = 0;
 497
 498                 goto out;
 499         }
 500
 501         if(proc_mm){
 502                 /* We have a valid from_mm, so we now have to copy the LDT of
 503                  * from_mm to new_mm, because using proc_mm an new mm with
 504                  * an empty/default LDT was created in new_mm()
 505                  */
 506                 copy = ((struct proc_mm_op) { .op       = MM_COPY_SEGMENTS,
 507                                               .u        =
 508                                               { .copy_segments =
 509                                                         from_mm->id.u.mm_fd } } );
 510                 i = os_write_file(new_mm->id.u.mm_fd, &copy, sizeof(copy));
 511                 if(i != sizeof(copy))
 512                         printk("new_mm : /proc/mm copy_segments failed, "
 513                                "err = %d\n", -i);
 514         }
 515
 516         if(!ptrace_ldt) {
 517                 /* Our local LDT is used to supply the data for
 518                  * modify_ldt(READLDT), if PTRACE_LDT isn't available,
 519                  * i.e., we have to use the stub for modify_ldt, which
 520                  * can't handle the big read buffer of up to 64kB.
 521                  */
 522                 down(&from_mm->ldt.semaphore);
 523                 if(from_mm->ldt.entry_count <= LDT_DIRECT_ENTRIES){
 524                         memcpy(new_mm->ldt.u.entries, from_mm->ldt.u.entries,
 525                                sizeof(new_mm->ldt.u.entries));
 526                 }
 527                 else{
 528                         i = from_mm->ldt.entry_count / LDT_ENTRIES_PER_PAGE;
 529                         while(i-->0){
 530                                 page = __get_free_page(GFP_KERNEL|__GFP_ZERO);
 531                                 if (!page){
 532                                         err = -ENOMEM;
 533                                         break;
 534                                 }
 535                                 new_mm->ldt.u.pages[i] =
 536                                         (struct ldt_entry *) page;
 537                                 memcpy(new_mm->ldt.u.pages[i],
 538                                        from_mm->ldt.u.pages[i], PAGE_SIZE);
 539                         }
 540                 }
 541                 new_mm->ldt.entry_count = from_mm->ldt.entry_count;
 542                 up(&from_mm->ldt.semaphore);
 543         }
 544
 545     out:
 546         return err;
 547 }
 548
 549
 550 void free_ldt(struct mmu_context_skas * mm)
 551 {
 552         int i;
 553
 554         if(!ptrace_ldt && mm->ldt.entry_count > LDT_DIRECT_ENTRIES){
 555                 i = mm->ldt.entry_count / LDT_ENTRIES_PER_PAGE;
 556                 while(i-- > 0){
 557                         free_page((long )mm->ldt.u.pages[i]);
 558                 }
 559         }
 560         mm->ldt.entry_count = 0;
 561 }
 562 #endif
 563
 564 int sys_modify_ldt(int func, void __user *ptr, unsigned long bytecount)
 565 {
 566         return(CHOOSE_MODE_PROC(do_modify_ldt_tt, do_modify_ldt_skas, func,
 567                                 ptr, bytecount));
 568 }