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