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