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