arch/x86/kernel/vm86_32.c

   1 /*
   2  *  Copyright (C) 1994  Linus Torvalds
   3  *
   4  *  29 dec 2001 - Fixed oopses caused by unchecked access to the vm86
   5  *                stack - Manfred Spraul <manfred@colorfullife.com>
   6  *
   7  *  22 mar 2002 - Manfred detected the stackfaults, but didn't handle
   8  *                them correctly. Now the emulation will be in a
   9  *                consistent state after stackfaults - Kasper Dupont
  10  *                <kasperd@daimi.au.dk>
  11  *
  12  *  22 mar 2002 - Added missing clear_IF in set_vflags_* Kasper Dupont
  13  *                <kasperd@daimi.au.dk>
  14  *
  15  *  ?? ??? 2002 - Fixed premature returns from handle_vm86_fault
  16  *                caused by Kasper Dupont's changes - Stas Sergeev
  17  *
  18  *   4 apr 2002 - Fixed CHECK_IF_IN_TRAP broken by Stas' changes.
  19  *                Kasper Dupont <kasperd@daimi.au.dk>
  20  *
  21  *   9 apr 2002 - Changed syntax of macros in handle_vm86_fault.
  22  *                Kasper Dupont <kasperd@daimi.au.dk>
  23  *
  24  *   9 apr 2002 - Changed stack access macros to jump to a label
  25  *                instead of returning to userspace. This simplifies
  26  *                do_int, and is needed by handle_vm6_fault. Kasper
  27  *                Dupont <kasperd@daimi.au.dk>
  28  *
  29  */
  30
  31 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  32
  33 #include <linux/capability.h>
  34 #include <linux/errno.h>
  35 #include <linux/interrupt.h>
  36 #include <linux/syscalls.h>
  37 #include <linux/sched.h>
  38 #include <linux/sched/task_stack.h>
  39 #include <linux/kernel.h>
  40 #include <linux/signal.h>
  41 #include <linux/string.h>
  42 #include <linux/mm.h>
  43 #include <linux/smp.h>
  44 #include <linux/highmem.h>
  45 #include <linux/ptrace.h>
  46 #include <linux/audit.h>
  47 #include <linux/stddef.h>
  48 #include <linux/slab.h>
  49 #include <linux/security.h>
  50
  51 #include <linux/uaccess.h>
  52 #include <asm/io.h>
  53 #include <asm/tlbflush.h>
  54 #include <asm/irq.h>
  55 #include <asm/traps.h>
  56 #include <asm/vm86.h>
  57
  58 /*
  59  * Known problems:
  60  *
  61  * Interrupt handling is not guaranteed:
  62  * - a real x86 will disable all interrupts for one instruction
  63  *   after a "mov ss,xx" to make stack handling atomic even without
  64  *   the 'lss' instruction. We can't guarantee this in v86 mode,
  65  *   as the next instruction might result in a page fault or similar.
  66  * - a real x86 will have interrupts disabled for one instruction
  67  *   past the 'sti' that enables them. We don't bother with all the
  68  *   details yet.
  69  *
  70  * Let's hope these problems do not actually matter for anything.
  71  */
  72
  73
  74 /*
  75  * 8- and 16-bit register defines..
  76  */
  77 #define AL(regs)        (((unsigned char *)&((regs)->pt.ax))[0])
  78 #define AH(regs)        (((unsigned char *)&((regs)->pt.ax))[1])
  79 #define IP(regs)        (*(unsigned short *)&((regs)->pt.ip))
  80 #define SP(regs)        (*(unsigned short *)&((regs)->pt.sp))
  81
  82 /*
  83  * virtual flags (16 and 32-bit versions)
  84  */
  85 #define VFLAGS  (*(unsigned short *)&(current->thread.vm86->veflags))
  86 #define VEFLAGS (current->thread.vm86->veflags)
  87
  88 #define set_flags(X, new, mask) \
  89 ((X) = ((X) & ~(mask)) | ((new) & (mask)))
  90
  91 #define SAFE_MASK       (0xDD5)
  92 #define RETURN_MASK     (0xDFF)
  93
  94 void save_v86_state(struct kernel_vm86_regs *regs, int retval)
  95 {
  96         struct tss_struct *tss;
  97         struct task_struct *tsk = current;
  98         struct vm86plus_struct __user *user;
  99         struct vm86 *vm86 = current->thread.vm86;
 100         long err = 0;
 101
 102         /*
 103          * This gets called from entry.S with interrupts disabled, but
 104          * from process context. Enable interrupts here, before trying
 105          * to access user space.
 106          */
 107         local_irq_enable();
 108
 109         if (!vm86 || !vm86->user_vm86) {
 110                 pr_alert("no user_vm86: BAD\n");
 111                 do_exit(SIGSEGV);
 112         }
 113         set_flags(regs->pt.flags, VEFLAGS, X86_EFLAGS_VIF | vm86->veflags_mask);
 114         user = vm86->user_vm86;
 115
 116         if (!access_ok(VERIFY_WRITE, user, vm86->vm86plus.is_vm86pus ?
 117                        sizeof(struct vm86plus_struct) :
 118                        sizeof(struct vm86_struct))) {
 119                 pr_alert("could not access userspace vm86 info\n");
 120                 do_exit(SIGSEGV);
 121         }
 122
 123         put_user_try {
 124                 put_user_ex(regs->pt.bx, &user->regs.ebx);
 125                 put_user_ex(regs->pt.cx, &user->regs.ecx);
 126                 put_user_ex(regs->pt.dx, &user->regs.edx);
 127                 put_user_ex(regs->pt.si, &user->regs.esi);
 128                 put_user_ex(regs->pt.di, &user->regs.edi);
 129                 put_user_ex(regs->pt.bp, &user->regs.ebp);
 130                 put_user_ex(regs->pt.ax, &user->regs.eax);
 131                 put_user_ex(regs->pt.ip, &user->regs.eip);
 132                 put_user_ex(regs->pt.cs, &user->regs.cs);
 133                 put_user_ex(regs->pt.flags, &user->regs.eflags);
 134                 put_user_ex(regs->pt.sp, &user->regs.esp);
 135                 put_user_ex(regs->pt.ss, &user->regs.ss);
 136                 put_user_ex(regs->es, &user->regs.es);
 137                 put_user_ex(regs->ds, &user->regs.ds);
 138                 put_user_ex(regs->fs, &user->regs.fs);
 139                 put_user_ex(regs->gs, &user->regs.gs);
 140
 141                 put_user_ex(vm86->screen_bitmap, &user->screen_bitmap);
 142         } put_user_catch(err);
 143         if (err) {
 144                 pr_alert("could not access userspace vm86 info\n");
 145                 do_exit(SIGSEGV);
 146         }
 147
 148         tss = &per_cpu(cpu_tss, get_cpu());
 149         tsk->thread.sp0 = vm86->saved_sp0;
 150         tsk->thread.sysenter_cs = __KERNEL_CS;
 151         load_sp0(tss, &tsk->thread);
 152         vm86->saved_sp0 = 0;
 153         put_cpu();
 154
 155         memcpy(&regs->pt, &vm86->regs32, sizeof(struct pt_regs));
 156
 157         lazy_load_gs(vm86->regs32.gs);
 158
 159         regs->pt.ax = retval;
 160 }
 161
 162 static void mark_screen_rdonly(struct mm_struct *mm)
 163 {
 164         struct vm_area_struct *vma;
 165         spinlock_t *ptl;
 166         pgd_t *pgd;
 167         pud_t *pud;
 168         pmd_t *pmd;
 169         pte_t *pte;
 170         int i;
 171
 172         down_write(&mm->mmap_sem);
 173         pgd = pgd_offset(mm, 0xA0000);
 174         if (pgd_none_or_clear_bad(pgd))
 175                 goto out;
 176         pud = pud_offset(pgd, 0xA0000);
 177         if (pud_none_or_clear_bad(pud))
 178                 goto out;
 179         pmd = pmd_offset(pud, 0xA0000);
 180
 181         if (pmd_trans_huge(*pmd)) {
 182                 vma = find_vma(mm, 0xA0000);
 183                 split_huge_pmd(vma, pmd, 0xA0000);
 184         }
 185         if (pmd_none_or_clear_bad(pmd))
 186                 goto out;
 187         pte = pte_offset_map_lock(mm, pmd, 0xA0000, &ptl);
 188         for (i = 0; i < 32; i++) {
 189                 if (pte_present(*pte))
 190                         set_pte(pte, pte_wrprotect(*pte));
 191                 pte++;
 192         }
 193         pte_unmap_unlock(pte, ptl);
 194 out:
 195         up_write(&mm->mmap_sem);
 196         flush_tlb();
 197 }
 198
 199
 200
 201 static int do_vm86_irq_handling(int subfunction, int irqnumber);
 202 static long do_sys_vm86(struct vm86plus_struct __user *user_vm86, bool plus);
 203
 204 SYSCALL_DEFINE1(vm86old, struct vm86_struct __user *, user_vm86)
 205 {
 206         return do_sys_vm86((struct vm86plus_struct __user *) user_vm86, false);
 207 }
 208
 209
 210 SYSCALL_DEFINE2(vm86, unsigned long, cmd, unsigned long, arg)
 211 {
 212         switch (cmd) {
 213         case VM86_REQUEST_IRQ:
 214         case VM86_FREE_IRQ:
 215         case VM86_GET_IRQ_BITS:
 216         case VM86_GET_AND_RESET_IRQ:
 217                 return do_vm86_irq_handling(cmd, (int)arg);
 218         case VM86_PLUS_INSTALL_CHECK:
 219                 /*
 220                  * NOTE: on old vm86 stuff this will return the error
 221                  *  from access_ok(), because the subfunction is
 222                  *  interpreted as (invalid) address to vm86_struct.
 223                  *  So the installation check works.
 224                  */
 225                 return 0;
 226         }
 227
 228         /* we come here only for functions VM86_ENTER, VM86_ENTER_NO_BYPASS */
 229         return do_sys_vm86((struct vm86plus_struct __user *) arg, true);
 230 }
 231
 232
 233 static long do_sys_vm86(struct vm86plus_struct __user *user_vm86, bool plus)
 234 {
 235         struct tss_struct *tss;
 236         struct task_struct *tsk = current;
 237         struct vm86 *vm86 = tsk->thread.vm86;
 238         struct kernel_vm86_regs vm86regs;
 239         struct pt_regs *regs = current_pt_regs();
 240         unsigned long err = 0;
 241
 242         err = security_mmap_addr(0);
 243         if (err) {
 244                 /*
 245                  * vm86 cannot virtualize the address space, so vm86 users
 246                  * need to manage the low 1MB themselves using mmap.  Given
 247                  * that BIOS places important data in the first page, vm86
 248                  * is essentially useless if mmap_min_addr != 0.  DOSEMU,
 249                  * for example, won't even bother trying to use vm86 if it
 250                  * can't map a page at virtual address 0.
 251                  *
 252                  * To reduce the available kernel attack surface, simply
 253                  * disallow vm86(old) for users who cannot mmap at va 0.
 254                  *
 255                  * The implementation of security_mmap_addr will allow
 256                  * suitably privileged users to map va 0 even if
 257                  * vm.mmap_min_addr is set above 0, and we want this
 258                  * behavior for vm86 as well, as it ensures that legacy
 259                  * tools like vbetool will not fail just because of
 260                  * vm.mmap_min_addr.
 261                  */
 262                 pr_info_once("Denied a call to vm86(old) from %s[%d] (uid: %d).  Set the vm.mmap_min_addr sysctl to 0 and/or adjust LSM mmap_min_addr policy to enable vm86 if you are using a vm86-based DOS emulator.\n",
 263                              current->comm, task_pid_nr(current),
 264                              from_kuid_munged(&init_user_ns, current_uid()));
 265                 return -EPERM;
 266         }
 267
 268         if (!vm86) {
 269                 if (!(vm86 = kzalloc(sizeof(*vm86), GFP_KERNEL)))
 270                         return -ENOMEM;
 271                 tsk->thread.vm86 = vm86;
 272         }
 273         if (vm86->saved_sp0)
 274                 return -EPERM;
 275
 276         if (!access_ok(VERIFY_READ, user_vm86, plus ?
 277                        sizeof(struct vm86_struct) :
 278                        sizeof(struct vm86plus_struct)))
 279                 return -EFAULT;
 280
 281         memset(&vm86regs, 0, sizeof(vm86regs));
 282         get_user_try {
 283                 unsigned short seg;
 284                 get_user_ex(vm86regs.pt.bx, &user_vm86->regs.ebx);
 285                 get_user_ex(vm86regs.pt.cx, &user_vm86->regs.ecx);
 286                 get_user_ex(vm86regs.pt.dx, &user_vm86->regs.edx);
 287                 get_user_ex(vm86regs.pt.si, &user_vm86->regs.esi);
 288                 get_user_ex(vm86regs.pt.di, &user_vm86->regs.edi);
 289                 get_user_ex(vm86regs.pt.bp, &user_vm86->regs.ebp);
 290                 get_user_ex(vm86regs.pt.ax, &user_vm86->regs.eax);
 291                 get_user_ex(vm86regs.pt.ip, &user_vm86->regs.eip);
 292                 get_user_ex(seg, &user_vm86->regs.cs);
 293                 vm86regs.pt.cs = seg;
 294                 get_user_ex(vm86regs.pt.flags, &user_vm86->regs.eflags);
 295                 get_user_ex(vm86regs.pt.sp, &user_vm86->regs.esp);
 296                 get_user_ex(seg, &user_vm86->regs.ss);
 297                 vm86regs.pt.ss = seg;
 298                 get_user_ex(vm86regs.es, &user_vm86->regs.es);
 299                 get_user_ex(vm86regs.ds, &user_vm86->regs.ds);
 300                 get_user_ex(vm86regs.fs, &user_vm86->regs.fs);
 301                 get_user_ex(vm86regs.gs, &user_vm86->regs.gs);
 302
 303                 get_user_ex(vm86->flags, &user_vm86->flags);
 304                 get_user_ex(vm86->screen_bitmap, &user_vm86->screen_bitmap);
 305                 get_user_ex(vm86->cpu_type, &user_vm86->cpu_type);
 306         } get_user_catch(err);
 307         if (err)
 308                 return err;
 309
 310         if (copy_from_user(&vm86->int_revectored,
 311                            &user_vm86->int_revectored,
 312                            sizeof(struct revectored_struct)))
 313                 return -EFAULT;
 314         if (copy_from_user(&vm86->int21_revectored,
 315                            &user_vm86->int21_revectored,
 316                            sizeof(struct revectored_struct)))
 317                 return -EFAULT;
 318         if (plus) {
 319                 if (copy_from_user(&vm86->vm86plus, &user_vm86->vm86plus,
 320                                    sizeof(struct vm86plus_info_struct)))
 321                         return -EFAULT;
 322                 vm86->vm86plus.is_vm86pus = 1;
 323         } else
 324                 memset(&vm86->vm86plus, 0,
 325                        sizeof(struct vm86plus_info_struct));
 326
 327         memcpy(&vm86->regs32, regs, sizeof(struct pt_regs));
 328         vm86->user_vm86 = user_vm86;
 329
 330 /*
 331  * The flags register is also special: we cannot trust that the user
 332  * has set it up safely, so this makes sure interrupt etc flags are
 333  * inherited from protected mode.
 334  */
 335         VEFLAGS = vm86regs.pt.flags;
 336         vm86regs.pt.flags &= SAFE_MASK;
 337         vm86regs.pt.flags |= regs->flags & ~SAFE_MASK;
 338         vm86regs.pt.flags |= X86_VM_MASK;
 339
 340         vm86regs.pt.orig_ax = regs->orig_ax;
 341
 342         switch (vm86->cpu_type) {
 343         case CPU_286:
 344                 vm86->veflags_mask = 0;
 345                 break;
 346         case CPU_386:
 347                 vm86->veflags_mask = X86_EFLAGS_NT | X86_EFLAGS_IOPL;
 348                 break;
 349         case CPU_486:
 350                 vm86->veflags_mask = X86_EFLAGS_AC | X86_EFLAGS_NT | X86_EFLAGS_IOPL;
 351                 break;
 352         default:
 353                 vm86->veflags_mask = X86_EFLAGS_ID | X86_EFLAGS_AC | X86_EFLAGS_NT | X86_EFLAGS_IOPL;
 354                 break;
 355         }
 356
 357 /*
 358  * Save old state
 359  */
 360         vm86->saved_sp0 = tsk->thread.sp0;
 361         lazy_save_gs(vm86->regs32.gs);
 362
 363         tss = &per_cpu(cpu_tss, get_cpu());
 364         /* make room for real-mode segments */
 365         tsk->thread.sp0 += 16;
 366
 367         if (static_cpu_has(X86_FEATURE_SEP))
 368                 tsk->thread.sysenter_cs = 0;
 369
 370         load_sp0(tss, &tsk->thread);
 371         put_cpu();
 372
 373         if (vm86->flags & VM86_SCREEN_BITMAP)
 374                 mark_screen_rdonly(tsk->mm);
 375
 376         memcpy((struct kernel_vm86_regs *)regs, &vm86regs, sizeof(vm86regs));
 377         force_iret();
 378         return regs->ax;
 379 }
 380
 381 static inline void set_IF(struct kernel_vm86_regs *regs)
 382 {
 383         VEFLAGS |= X86_EFLAGS_VIF;
 384 }
 385
 386 static inline void clear_IF(struct kernel_vm86_regs *regs)
 387 {
 388         VEFLAGS &= ~X86_EFLAGS_VIF;
 389 }
 390
 391 static inline void clear_TF(struct kernel_vm86_regs *regs)
 392 {
 393         regs->pt.flags &= ~X86_EFLAGS_TF;
 394 }
 395
 396 static inline void clear_AC(struct kernel_vm86_regs *regs)
 397 {
 398         regs->pt.flags &= ~X86_EFLAGS_AC;
 399 }
 400
 401 /*
 402  * It is correct to call set_IF(regs) from the set_vflags_*
 403  * functions. However someone forgot to call clear_IF(regs)
 404  * in the opposite case.
 405  * After the command sequence CLI PUSHF STI POPF you should
 406  * end up with interrupts disabled, but you ended up with
 407  * interrupts enabled.
 408  *  ( I was testing my own changes, but the only bug I
 409  *    could find was in a function I had not changed. )
 410  * [KD]
 411  */
 412
 413 static inline void set_vflags_long(unsigned long flags, struct kernel_vm86_regs *regs)
 414 {
 415         set_flags(VEFLAGS, flags, current->thread.vm86->veflags_mask);
 416         set_flags(regs->pt.flags, flags, SAFE_MASK);
 417         if (flags & X86_EFLAGS_IF)
 418                 set_IF(regs);
 419         else
 420                 clear_IF(regs);
 421 }
 422
 423 static inline void set_vflags_short(unsigned short flags, struct kernel_vm86_regs *regs)
 424 {
 425         set_flags(VFLAGS, flags, current->thread.vm86->veflags_mask);
 426         set_flags(regs->pt.flags, flags, SAFE_MASK);
 427         if (flags & X86_EFLAGS_IF)
 428                 set_IF(regs);
 429         else
 430                 clear_IF(regs);
 431 }
 432
 433 static inline unsigned long get_vflags(struct kernel_vm86_regs *regs)
 434 {
 435         unsigned long flags = regs->pt.flags & RETURN_MASK;
 436
 437         if (VEFLAGS & X86_EFLAGS_VIF)
 438                 flags |= X86_EFLAGS_IF;
 439         flags |= X86_EFLAGS_IOPL;
 440         return flags | (VEFLAGS & current->thread.vm86->veflags_mask);
 441 }
 442
 443 static inline int is_revectored(int nr, struct revectored_struct *bitmap)
 444 {
 445         return test_bit(nr, bitmap->__map);
 446 }
 447
 448 #define val_byte(val, n) (((__u8 *)&val)[n])
 449
 450 #define pushb(base, ptr, val, err_label) \
 451         do { \
 452                 __u8 __val = val; \
 453                 ptr--; \
 454                 if (put_user(__val, base + ptr) < 0) \
 455                         goto err_label; \
 456         } while (0)
 457
 458 #define pushw(base, ptr, val, err_label) \
 459         do { \
 460                 __u16 __val = val; \
 461                 ptr--; \
 462                 if (put_user(val_byte(__val, 1), base + ptr) < 0) \
 463                         goto err_label; \
 464                 ptr--; \
 465                 if (put_user(val_byte(__val, 0), base + ptr) < 0) \
 466                         goto err_label; \
 467         } while (0)
 468
 469 #define pushl(base, ptr, val, err_label) \
 470         do { \
 471                 __u32 __val = val; \
 472                 ptr--; \
 473                 if (put_user(val_byte(__val, 3), base + ptr) < 0) \
 474                         goto err_label; \
 475                 ptr--; \
 476                 if (put_user(val_byte(__val, 2), base + ptr) < 0) \
 477                         goto err_label; \
 478                 ptr--; \
 479                 if (put_user(val_byte(__val, 1), base + ptr) < 0) \
 480                         goto err_label; \
 481                 ptr--; \
 482                 if (put_user(val_byte(__val, 0), base + ptr) < 0) \
 483                         goto err_label; \
 484         } while (0)
 485
 486 #define popb(base, ptr, err_label) \
 487         ({ \
 488                 __u8 __res; \
 489                 if (get_user(__res, base + ptr) < 0) \
 490                         goto err_label; \
 491                 ptr++; \
 492                 __res; \
 493         })
 494
 495 #define popw(base, ptr, err_label) \
 496         ({ \
 497                 __u16 __res; \
 498                 if (get_user(val_byte(__res, 0), base + ptr) < 0) \
 499                         goto err_label; \
 500                 ptr++; \
 501                 if (get_user(val_byte(__res, 1), base + ptr) < 0) \
 502                         goto err_label; \
 503                 ptr++; \
 504                 __res; \
 505         })
 506
 507 #define popl(base, ptr, err_label) \
 508         ({ \
 509                 __u32 __res; \
 510                 if (get_user(val_byte(__res, 0), base + ptr) < 0) \
 511                         goto err_label; \
 512                 ptr++; \
 513                 if (get_user(val_byte(__res, 1), base + ptr) < 0) \
 514                         goto err_label; \
 515                 ptr++; \
 516                 if (get_user(val_byte(__res, 2), base + ptr) < 0) \
 517                         goto err_label; \
 518                 ptr++; \
 519                 if (get_user(val_byte(__res, 3), base + ptr) < 0) \
 520                         goto err_label; \
 521                 ptr++; \
 522                 __res; \
 523         })
 524
 525 /* There are so many possible reasons for this function to return
 526  * VM86_INTx, so adding another doesn't bother me. We can expect
 527  * userspace programs to be able to handle it. (Getting a problem
 528  * in userspace is always better than an Oops anyway.) [KD]
 529  */
 530 static void do_int(struct kernel_vm86_regs *regs, int i,
 531     unsigned char __user *ssp, unsigned short sp)
 532 {
 533         unsigned long __user *intr_ptr;
 534         unsigned long segoffs;
 535         struct vm86 *vm86 = current->thread.vm86;
 536
 537         if (regs->pt.cs == BIOSSEG)
 538                 goto cannot_handle;
 539         if (is_revectored(i, &vm86->int_revectored))
 540                 goto cannot_handle;
 541         if (i == 0x21 && is_revectored(AH(regs), &vm86->int21_revectored))
 542                 goto cannot_handle;
 543         intr_ptr = (unsigned long __user *) (i << 2);
 544         if (get_user(segoffs, intr_ptr))
 545                 goto cannot_handle;
 546         if ((segoffs >> 16) == BIOSSEG)
 547                 goto cannot_handle;
 548         pushw(ssp, sp, get_vflags(regs), cannot_handle);
 549         pushw(ssp, sp, regs->pt.cs, cannot_handle);
 550         pushw(ssp, sp, IP(regs), cannot_handle);
 551         regs->pt.cs = segoffs >> 16;
 552         SP(regs) -= 6;
 553         IP(regs) = segoffs & 0xffff;
 554         clear_TF(regs);
 555         clear_IF(regs);
 556         clear_AC(regs);
 557         return;
 558
 559 cannot_handle:
 560         save_v86_state(regs, VM86_INTx + (i << 8));
 561 }
 562
 563 int handle_vm86_trap(struct kernel_vm86_regs *regs, long error_code, int trapno)
 564 {
 565         struct vm86 *vm86 = current->thread.vm86;
 566
 567         if (vm86->vm86plus.is_vm86pus) {
 568                 if ((trapno == 3) || (trapno == 1)) {
 569                         save_v86_state(regs, VM86_TRAP + (trapno << 8));
 570                         return 0;
 571                 }
 572                 do_int(regs, trapno, (unsigned char __user *) (regs->pt.ss << 4), SP(regs));
 573                 return 0;
 574         }
 575         if (trapno != 1)
 576                 return 1; /* we let this handle by the calling routine */
 577         current->thread.trap_nr = trapno;
 578         current->thread.error_code = error_code;
 579         force_sig(SIGTRAP, current);
 580         return 0;
 581 }
 582
 583 void handle_vm86_fault(struct kernel_vm86_regs *regs, long error_code)
 584 {
 585         unsigned char opcode;
 586         unsigned char __user *csp;
 587         unsigned char __user *ssp;
 588         unsigned short ip, sp, orig_flags;
 589         int data32, pref_done;
 590         struct vm86plus_info_struct *vmpi = &current->thread.vm86->vm86plus;
 591
 592 #define CHECK_IF_IN_TRAP \
 593         if (vmpi->vm86dbg_active && vmpi->vm86dbg_TFpendig) \
 594                 newflags |= X86_EFLAGS_TF
 595
 596         orig_flags = *(unsigned short *)&regs->pt.flags;
 597
 598         csp = (unsigned char __user *) (regs->pt.cs << 4);
 599         ssp = (unsigned char __user *) (regs->pt.ss << 4);
 600         sp = SP(regs);
 601         ip = IP(regs);
 602
 603         data32 = 0;
 604         pref_done = 0;
 605         do {
 606                 switch (opcode = popb(csp, ip, simulate_sigsegv)) {
 607                 case 0x66:      /* 32-bit data */     data32 = 1; break;
 608                 case 0x67:      /* 32-bit address */  break;
 609                 case 0x2e:      /* CS */              break;
 610                 case 0x3e:      /* DS */              break;
 611                 case 0x26:      /* ES */              break;
 612                 case 0x36:      /* SS */              break;
 613                 case 0x65:      /* GS */              break;
 614                 case 0x64:      /* FS */              break;
 615                 case 0xf2:      /* repnz */       break;
 616                 case 0xf3:      /* rep */             break;
 617                 default: pref_done = 1;
 618                 }
 619         } while (!pref_done);
 620
 621         switch (opcode) {
 622
 623         /* pushf */
 624         case 0x9c:
 625                 if (data32) {
 626                         pushl(ssp, sp, get_vflags(regs), simulate_sigsegv);
 627                         SP(regs) -= 4;
 628                 } else {
 629                         pushw(ssp, sp, get_vflags(regs), simulate_sigsegv);
 630                         SP(regs) -= 2;
 631                 }
 632                 IP(regs) = ip;
 633                 goto vm86_fault_return;
 634
 635         /* popf */
 636         case 0x9d:
 637                 {
 638                 unsigned long newflags;
 639                 if (data32) {
 640                         newflags = popl(ssp, sp, simulate_sigsegv);
 641                         SP(regs) += 4;
 642                 } else {
 643                         newflags = popw(ssp, sp, simulate_sigsegv);
 644                         SP(regs) += 2;
 645                 }
 646                 IP(regs) = ip;
 647                 CHECK_IF_IN_TRAP;
 648                 if (data32)
 649                         set_vflags_long(newflags, regs);
 650                 else
 651                         set_vflags_short(newflags, regs);
 652
 653                 goto check_vip;
 654                 }
 655
 656         /* int xx */
 657         case 0xcd: {
 658                 int intno = popb(csp, ip, simulate_sigsegv);
 659                 IP(regs) = ip;
 660                 if (vmpi->vm86dbg_active) {
 661                         if ((1 << (intno & 7)) & vmpi->vm86dbg_intxxtab[intno >> 3]) {
 662                                 save_v86_state(regs, VM86_INTx + (intno << 8));
 663                                 return;
 664                         }
 665                 }
 666                 do_int(regs, intno, ssp, sp);
 667                 return;
 668         }
 669
 670         /* iret */
 671         case 0xcf:
 672                 {
 673                 unsigned long newip;
 674                 unsigned long newcs;
 675                 unsigned long newflags;
 676                 if (data32) {
 677                         newip = popl(ssp, sp, simulate_sigsegv);
 678                         newcs = popl(ssp, sp, simulate_sigsegv);
 679                         newflags = popl(ssp, sp, simulate_sigsegv);
 680                         SP(regs) += 12;
 681                 } else {
 682                         newip = popw(ssp, sp, simulate_sigsegv);
 683                         newcs = popw(ssp, sp, simulate_sigsegv);
 684                         newflags = popw(ssp, sp, simulate_sigsegv);
 685                         SP(regs) += 6;
 686                 }
 687                 IP(regs) = newip;
 688                 regs->pt.cs = newcs;
 689                 CHECK_IF_IN_TRAP;
 690                 if (data32) {
 691                         set_vflags_long(newflags, regs);
 692                 } else {
 693                         set_vflags_short(newflags, regs);
 694                 }
 695                 goto check_vip;
 696                 }
 697
 698         /* cli */
 699         case 0xfa:
 700                 IP(regs) = ip;
 701                 clear_IF(regs);
 702                 goto vm86_fault_return;
 703
 704         /* sti */
 705         /*
 706          * Damn. This is incorrect: the 'sti' instruction should actually
 707          * enable interrupts after the /next/ instruction. Not good.
 708          *
 709          * Probably needs some horsing around with the TF flag. Aiee..
 710          */
 711         case 0xfb:
 712                 IP(regs) = ip;
 713                 set_IF(regs);
 714                 goto check_vip;
 715
 716         default:
 717                 save_v86_state(regs, VM86_UNKNOWN);
 718         }
 719
 720         return;
 721
 722 check_vip:
 723         if (VEFLAGS & X86_EFLAGS_VIP) {
 724                 save_v86_state(regs, VM86_STI);
 725                 return;
 726         }
 727
 728 vm86_fault_return:
 729         if (vmpi->force_return_for_pic  && (VEFLAGS & (X86_EFLAGS_IF | X86_EFLAGS_VIF))) {
 730                 save_v86_state(regs, VM86_PICRETURN);
 731                 return;
 732         }
 733         if (orig_flags & X86_EFLAGS_TF)
 734                 handle_vm86_trap(regs, 0, X86_TRAP_DB);
 735         return;
 736
 737 simulate_sigsegv:
 738         /* FIXME: After a long discussion with Stas we finally
 739          *        agreed, that this is wrong. Here we should
 740          *        really send a SIGSEGV to the user program.
 741          *        But how do we create the correct context? We
 742          *        are inside a general protection fault handler
 743          *        and has just returned from a page fault handler.
 744          *        The correct context for the signal handler
 745          *        should be a mixture of the two, but how do we
 746          *        get the information? [KD]
 747          */
 748         save_v86_state(regs, VM86_UNKNOWN);
 749 }
 750
 751 /* ---------------- vm86 special IRQ passing stuff ----------------- */
 752
 753 #define VM86_IRQNAME            "vm86irq"
 754
 755 static struct vm86_irqs {
 756         struct task_struct *tsk;
 757         int sig;
 758 } vm86_irqs[16];
 759
 760 static DEFINE_SPINLOCK(irqbits_lock);
 761 static int irqbits;
 762
 763 #define ALLOWED_SIGS (1 /* 0 = don't send a signal */ \
 764         | (1 << SIGUSR1) | (1 << SIGUSR2) | (1 << SIGIO)  | (1 << SIGURG) \
 765         | (1 << SIGUNUSED))
 766
 767 static irqreturn_t irq_handler(int intno, void *dev_id)
 768 {
 769         int irq_bit;
 770         unsigned long flags;
 771
 772         spin_lock_irqsave(&irqbits_lock, flags);
 773         irq_bit = 1 << intno;
 774         if ((irqbits & irq_bit) || !vm86_irqs[intno].tsk)
 775                 goto out;
 776         irqbits |= irq_bit;
 777         if (vm86_irqs[intno].sig)
 778                 send_sig(vm86_irqs[intno].sig, vm86_irqs[intno].tsk, 1);
 779         /*
 780          * IRQ will be re-enabled when user asks for the irq (whether
 781          * polling or as a result of the signal)
 782          */
 783         disable_irq_nosync(intno);
 784         spin_unlock_irqrestore(&irqbits_lock, flags);
 785         return IRQ_HANDLED;
 786
 787 out:
 788         spin_unlock_irqrestore(&irqbits_lock, flags);
 789         return IRQ_NONE;
 790 }
 791
 792 static inline void free_vm86_irq(int irqnumber)
 793 {
 794         unsigned long flags;
 795
 796         free_irq(irqnumber, NULL);
 797         vm86_irqs[irqnumber].tsk = NULL;
 798
 799         spin_lock_irqsave(&irqbits_lock, flags);
 800         irqbits &= ~(1 << irqnumber);
 801         spin_unlock_irqrestore(&irqbits_lock, flags);
 802 }
 803
 804 void release_vm86_irqs(struct task_struct *task)
 805 {
 806         int i;
 807         for (i = FIRST_VM86_IRQ ; i <= LAST_VM86_IRQ; i++)
 808             if (vm86_irqs[i].tsk == task)
 809                 free_vm86_irq(i);
 810 }
 811
 812 static inline int get_and_reset_irq(int irqnumber)
 813 {
 814         int bit;
 815         unsigned long flags;
 816         int ret = 0;
 817
 818         if (invalid_vm86_irq(irqnumber)) return 0;
 819         if (vm86_irqs[irqnumber].tsk != current) return 0;
 820         spin_lock_irqsave(&irqbits_lock, flags);
 821         bit = irqbits & (1 << irqnumber);
 822         irqbits &= ~bit;
 823         if (bit) {
 824                 enable_irq(irqnumber);
 825                 ret = 1;
 826         }
 827
 828         spin_unlock_irqrestore(&irqbits_lock, flags);
 829         return ret;
 830 }
 831
 832
 833 static int do_vm86_irq_handling(int subfunction, int irqnumber)
 834 {
 835         int ret;
 836         switch (subfunction) {
 837                 case VM86_GET_AND_RESET_IRQ: {
 838                         return get_and_reset_irq(irqnumber);
 839                 }
 840                 case VM86_GET_IRQ_BITS: {
 841                         return irqbits;
 842                 }
 843                 case VM86_REQUEST_IRQ: {
 844                         int sig = irqnumber >> 8;
 845                         int irq = irqnumber & 255;
 846                         if (!capable(CAP_SYS_ADMIN)) return -EPERM;
 847                         if (!((1 << sig) & ALLOWED_SIGS)) return -EPERM;
 848                         if (invalid_vm86_irq(irq)) return -EPERM;
 849                         if (vm86_irqs[irq].tsk) return -EPERM;
 850                         ret = request_irq(irq, &irq_handler, 0, VM86_IRQNAME, NULL);
 851                         if (ret) return ret;
 852                         vm86_irqs[irq].sig = sig;
 853                         vm86_irqs[irq].tsk = current;
 854                         return irq;
 855                 }
 856                 case  VM86_FREE_IRQ: {
 857                         if (invalid_vm86_irq(irqnumber)) return -EPERM;
 858                         if (!vm86_irqs[irqnumber].tsk) return 0;
 859                         if (vm86_irqs[irqnumber].tsk != current) return -EPERM;
 860                         free_vm86_irq(irqnumber);
 861                         return 0;
 862                 }
 863         }
 864         return -EINVAL;
 865 }
 866