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Linux/arch/x86/kernel/vm86_32.c

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  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 
 48 #include <asm/uaccess.h>
 49 #include <asm/io.h>
 50 #include <asm/tlbflush.h>
 51 #include <asm/irq.h>
 52 
 53 /*
 54  * Known problems:
 55  *
 56  * Interrupt handling is not guaranteed:
 57  * - a real x86 will disable all interrupts for one instruction
 58  *   after a "mov ss,xx" to make stack handling atomic even without
 59  *   the 'lss' instruction. We can't guarantee this in v86 mode,
 60  *   as the next instruction might result in a page fault or similar.
 61  * - a real x86 will have interrupts disabled for one instruction
 62  *   past the 'sti' that enables them. We don't bother with all the
 63  *   details yet.
 64  *
 65  * Let's hope these problems do not actually matter for anything.
 66  */
 67 
 68 
 69 #define KVM86   ((struct kernel_vm86_struct *)regs)
 70 #define VMPI    KVM86->vm86plus
 71 
 72 
 73 /*
 74  * 8- and 16-bit register defines..
 75  */
 76 #define AL(regs)        (((unsigned char *)&((regs)->pt.ax))[0])
 77 #define AH(regs)        (((unsigned char *)&((regs)->pt.ax))[1])
 78 #define IP(regs)        (*(unsigned short *)&((regs)->pt.ip))
 79 #define SP(regs)        (*(unsigned short *)&((regs)->pt.sp))
 80 
 81 /*
 82  * virtual flags (16 and 32-bit versions)
 83  */
 84 #define VFLAGS  (*(unsigned short *)&(current->thread.v86flags))
 85 #define VEFLAGS (current->thread.v86flags)
 86 
 87 #define set_flags(X, new, mask) \
 88 ((X) = ((X) & ~(mask)) | ((new) & (mask)))
 89 
 90 #define SAFE_MASK       (0xDD5)
 91 #define RETURN_MASK     (0xDFF)
 92 
 93 /* convert kernel_vm86_regs to vm86_regs */
 94 static int copy_vm86_regs_to_user(struct vm86_regs __user *user,
 95                                   const struct kernel_vm86_regs *regs)
 96 {
 97         int ret = 0;
 98 
 99         /*
100          * kernel_vm86_regs is missing gs, so copy everything up to
101          * (but not including) orig_eax, and then rest including orig_eax.
102          */
103         ret += copy_to_user(user, regs, offsetof(struct kernel_vm86_regs, pt.orig_ax));
104         ret += copy_to_user(&user->orig_eax, &regs->pt.orig_ax,
105                             sizeof(struct kernel_vm86_regs) -
106                             offsetof(struct kernel_vm86_regs, pt.orig_ax));
107 
108         return ret;
109 }
110 
111 /* convert vm86_regs to kernel_vm86_regs */
112 static int copy_vm86_regs_from_user(struct kernel_vm86_regs *regs,
113                                     const struct vm86_regs __user *user,
114                                     unsigned extra)
115 {
116         int ret = 0;
117 
118         /* copy ax-fs inclusive */
119         ret += copy_from_user(regs, user, offsetof(struct kernel_vm86_regs, pt.orig_ax));
120         /* copy orig_ax-__gsh+extra */
121         ret += copy_from_user(&regs->pt.orig_ax, &user->orig_eax,
122                               sizeof(struct kernel_vm86_regs) -
123                               offsetof(struct kernel_vm86_regs, pt.orig_ax) +
124                               extra);
125         return ret;
126 }
127 
128 struct pt_regs *save_v86_state(struct kernel_vm86_regs *regs)
129 {
130         struct tss_struct *tss;
131         struct pt_regs *ret;
132         unsigned long tmp;
133 
134         /*
135          * This gets called from entry.S with interrupts disabled, but
136          * from process context. Enable interrupts here, before trying
137          * to access user space.
138          */
139         local_irq_enable();
140 
141         if (!current->thread.vm86_info) {
142                 pr_alert("no vm86_info: BAD\n");
143                 do_exit(SIGSEGV);
144         }
145         set_flags(regs->pt.flags, VEFLAGS, X86_EFLAGS_VIF | current->thread.v86mask);
146         tmp = copy_vm86_regs_to_user(&current->thread.vm86_info->regs, regs);
147         tmp += put_user(current->thread.screen_bitmap, &current->thread.vm86_info->screen_bitmap);
148         if (tmp) {
149                 pr_alert("could not access userspace vm86_info\n");
150                 do_exit(SIGSEGV);
151         }
152 
153         tss = &per_cpu(cpu_tss, get_cpu());
154         current->thread.sp0 = current->thread.saved_sp0;
155         current->thread.sysenter_cs = __KERNEL_CS;
156         load_sp0(tss, &current->thread);
157         current->thread.saved_sp0 = 0;
158         put_cpu();
159 
160         ret = KVM86->regs32;
161 
162         ret->fs = current->thread.saved_fs;
163         set_user_gs(ret, current->thread.saved_gs);
164 
165         return ret;
166 }
167 
168 static void mark_screen_rdonly(struct mm_struct *mm)
169 {
170         pgd_t *pgd;
171         pud_t *pud;
172         pmd_t *pmd;
173         pte_t *pte;
174         spinlock_t *ptl;
175         int i;
176 
177         down_write(&mm->mmap_sem);
178         pgd = pgd_offset(mm, 0xA0000);
179         if (pgd_none_or_clear_bad(pgd))
180                 goto out;
181         pud = pud_offset(pgd, 0xA0000);
182         if (pud_none_or_clear_bad(pud))
183                 goto out;
184         pmd = pmd_offset(pud, 0xA0000);
185         split_huge_page_pmd_mm(mm, 0xA0000, pmd);
186         if (pmd_none_or_clear_bad(pmd))
187                 goto out;
188         pte = pte_offset_map_lock(mm, pmd, 0xA0000, &ptl);
189         for (i = 0; i < 32; i++) {
190                 if (pte_present(*pte))
191                         set_pte(pte, pte_wrprotect(*pte));
192                 pte++;
193         }
194         pte_unmap_unlock(pte, ptl);
195 out:
196         up_write(&mm->mmap_sem);
197         flush_tlb();
198 }
199 
200 
201 
202 static int do_vm86_irq_handling(int subfunction, int irqnumber);
203 static void do_sys_vm86(struct kernel_vm86_struct *info, struct task_struct *tsk);
204 
205 SYSCALL_DEFINE1(vm86old, struct vm86_struct __user *, v86)
206 {
207         struct kernel_vm86_struct info; /* declare this _on top_,
208                                          * this avoids wasting of stack space.
209                                          * This remains on the stack until we
210                                          * return to 32 bit user space.
211                                          */
212         struct task_struct *tsk = current;
213         int tmp;
214 
215         if (tsk->thread.saved_sp0)
216                 return -EPERM;
217         tmp = copy_vm86_regs_from_user(&info.regs, &v86->regs,
218                                        offsetof(struct kernel_vm86_struct, vm86plus) -
219                                        sizeof(info.regs));
220         if (tmp)
221                 return -EFAULT;
222         memset(&info.vm86plus, 0, (int)&info.regs32 - (int)&info.vm86plus);
223         info.regs32 = current_pt_regs();
224         tsk->thread.vm86_info = v86;
225         do_sys_vm86(&info, tsk);
226         return 0;       /* we never return here */
227 }
228 
229 
230 SYSCALL_DEFINE2(vm86, unsigned long, cmd, unsigned long, arg)
231 {
232         struct kernel_vm86_struct info; /* declare this _on top_,
233                                          * this avoids wasting of stack space.
234                                          * This remains on the stack until we
235                                          * return to 32 bit user space.
236                                          */
237         struct task_struct *tsk;
238         int tmp;
239         struct vm86plus_struct __user *v86;
240 
241         tsk = current;
242         switch (cmd) {
243         case VM86_REQUEST_IRQ:
244         case VM86_FREE_IRQ:
245         case VM86_GET_IRQ_BITS:
246         case VM86_GET_AND_RESET_IRQ:
247                 return do_vm86_irq_handling(cmd, (int)arg);
248         case VM86_PLUS_INSTALL_CHECK:
249                 /*
250                  * NOTE: on old vm86 stuff this will return the error
251                  *  from access_ok(), because the subfunction is
252                  *  interpreted as (invalid) address to vm86_struct.
253                  *  So the installation check works.
254                  */
255                 return 0;
256         }
257 
258         /* we come here only for functions VM86_ENTER, VM86_ENTER_NO_BYPASS */
259         if (tsk->thread.saved_sp0)
260                 return -EPERM;
261         v86 = (struct vm86plus_struct __user *)arg;
262         tmp = copy_vm86_regs_from_user(&info.regs, &v86->regs,
263                                        offsetof(struct kernel_vm86_struct, regs32) -
264                                        sizeof(info.regs));
265         if (tmp)
266                 return -EFAULT;
267         info.regs32 = current_pt_regs();
268         info.vm86plus.is_vm86pus = 1;
269         tsk->thread.vm86_info = (struct vm86_struct __user *)v86;
270         do_sys_vm86(&info, tsk);
271         return 0;       /* we never return here */
272 }
273 
274 
275 static void do_sys_vm86(struct kernel_vm86_struct *info, struct task_struct *tsk)
276 {
277         struct tss_struct *tss;
278 /*
279  * make sure the vm86() system call doesn't try to do anything silly
280  */
281         info->regs.pt.ds = 0;
282         info->regs.pt.es = 0;
283         info->regs.pt.fs = 0;
284 #ifndef CONFIG_X86_32_LAZY_GS
285         info->regs.pt.gs = 0;
286 #endif
287 
288 /*
289  * The flags register is also special: we cannot trust that the user
290  * has set it up safely, so this makes sure interrupt etc flags are
291  * inherited from protected mode.
292  */
293         VEFLAGS = info->regs.pt.flags;
294         info->regs.pt.flags &= SAFE_MASK;
295         info->regs.pt.flags |= info->regs32->flags & ~SAFE_MASK;
296         info->regs.pt.flags |= X86_VM_MASK;
297 
298         switch (info->cpu_type) {
299         case CPU_286:
300                 tsk->thread.v86mask = 0;
301                 break;
302         case CPU_386:
303                 tsk->thread.v86mask = X86_EFLAGS_NT | X86_EFLAGS_IOPL;
304                 break;
305         case CPU_486:
306                 tsk->thread.v86mask = X86_EFLAGS_AC | X86_EFLAGS_NT | X86_EFLAGS_IOPL;
307                 break;
308         default:
309                 tsk->thread.v86mask = X86_EFLAGS_ID | X86_EFLAGS_AC | X86_EFLAGS_NT | X86_EFLAGS_IOPL;
310                 break;
311         }
312 
313 /*
314  * Save old state, set default return value (%ax) to 0 (VM86_SIGNAL)
315  */
316         info->regs32->ax = VM86_SIGNAL;
317         tsk->thread.saved_sp0 = tsk->thread.sp0;
318         tsk->thread.saved_fs = info->regs32->fs;
319         tsk->thread.saved_gs = get_user_gs(info->regs32);
320 
321         tss = &per_cpu(cpu_tss, get_cpu());
322         tsk->thread.sp0 = (unsigned long) &info->VM86_TSS_ESP0;
323         if (cpu_has_sep)
324                 tsk->thread.sysenter_cs = 0;
325         load_sp0(tss, &tsk->thread);
326         put_cpu();
327 
328         tsk->thread.screen_bitmap = info->screen_bitmap;
329         if (info->flags & VM86_SCREEN_BITMAP)
330                 mark_screen_rdonly(tsk->mm);
331 
332         /*call __audit_syscall_exit since we do not exit via the normal paths */
333 #ifdef CONFIG_AUDITSYSCALL
334         if (unlikely(current->audit_context))
335                 __audit_syscall_exit(1, 0);
336 #endif
337 
338         __asm__ __volatile__(
339                 "movl %0,%%esp\n\t"
340                 "movl %1,%%ebp\n\t"
341 #ifdef CONFIG_X86_32_LAZY_GS
342                 "mov  %2, %%gs\n\t"
343 #endif
344                 "jmp resume_userspace"
345                 : /* no outputs */
346                 :"r" (&info->regs), "r" (task_thread_info(tsk)), "r" (0));
347         /* we never return here */
348 }
349 
350 static inline void return_to_32bit(struct kernel_vm86_regs *regs16, int retval)
351 {
352         struct pt_regs *regs32;
353 
354         regs32 = save_v86_state(regs16);
355         regs32->ax = retval;
356         __asm__ __volatile__("movl %0,%%esp\n\t"
357                 "movl %1,%%ebp\n\t"
358                 "jmp resume_userspace"
359                 : : "r" (regs32), "r" (current_thread_info()));
360 }
361 
362 static inline void set_IF(struct kernel_vm86_regs *regs)
363 {
364         VEFLAGS |= X86_EFLAGS_VIF;
365         if (VEFLAGS & X86_EFLAGS_VIP)
366                 return_to_32bit(regs, VM86_STI);
367 }
368 
369 static inline void clear_IF(struct kernel_vm86_regs *regs)
370 {
371         VEFLAGS &= ~X86_EFLAGS_VIF;
372 }
373 
374 static inline void clear_TF(struct kernel_vm86_regs *regs)
375 {
376         regs->pt.flags &= ~X86_EFLAGS_TF;
377 }
378 
379 static inline void clear_AC(struct kernel_vm86_regs *regs)
380 {
381         regs->pt.flags &= ~X86_EFLAGS_AC;
382 }
383 
384 /*
385  * It is correct to call set_IF(regs) from the set_vflags_*
386  * functions. However someone forgot to call clear_IF(regs)
387  * in the opposite case.
388  * After the command sequence CLI PUSHF STI POPF you should
389  * end up with interrupts disabled, but you ended up with
390  * interrupts enabled.
391  *  ( I was testing my own changes, but the only bug I
392  *    could find was in a function I had not changed. )
393  * [KD]
394  */
395 
396 static inline void set_vflags_long(unsigned long flags, struct kernel_vm86_regs *regs)
397 {
398         set_flags(VEFLAGS, flags, current->thread.v86mask);
399         set_flags(regs->pt.flags, flags, SAFE_MASK);
400         if (flags & X86_EFLAGS_IF)
401                 set_IF(regs);
402         else
403                 clear_IF(regs);
404 }
405 
406 static inline void set_vflags_short(unsigned short flags, struct kernel_vm86_regs *regs)
407 {
408         set_flags(VFLAGS, flags, current->thread.v86mask);
409         set_flags(regs->pt.flags, flags, SAFE_MASK);
410         if (flags & X86_EFLAGS_IF)
411                 set_IF(regs);
412         else
413                 clear_IF(regs);
414 }
415 
416 static inline unsigned long get_vflags(struct kernel_vm86_regs *regs)
417 {
418         unsigned long flags = regs->pt.flags & RETURN_MASK;
419 
420         if (VEFLAGS & X86_EFLAGS_VIF)
421                 flags |= X86_EFLAGS_IF;
422         flags |= X86_EFLAGS_IOPL;
423         return flags | (VEFLAGS & current->thread.v86mask);
424 }
425 
426 static inline int is_revectored(int nr, struct revectored_struct *bitmap)
427 {
428         __asm__ __volatile__("btl %2,%1\n\tsbbl %0,%0"
429                 :"=r" (nr)
430                 :"m" (*bitmap), "r" (nr));
431         return nr;
432 }
433 
434 #define val_byte(val, n) (((__u8 *)&val)[n])
435 
436 #define pushb(base, ptr, val, err_label) \
437         do { \
438                 __u8 __val = val; \
439                 ptr--; \
440                 if (put_user(__val, base + ptr) < 0) \
441                         goto err_label; \
442         } while (0)
443 
444 #define pushw(base, ptr, val, err_label) \
445         do { \
446                 __u16 __val = val; \
447                 ptr--; \
448                 if (put_user(val_byte(__val, 1), base + ptr) < 0) \
449                         goto err_label; \
450                 ptr--; \
451                 if (put_user(val_byte(__val, 0), base + ptr) < 0) \
452                         goto err_label; \
453         } while (0)
454 
455 #define pushl(base, ptr, val, err_label) \
456         do { \
457                 __u32 __val = val; \
458                 ptr--; \
459                 if (put_user(val_byte(__val, 3), base + ptr) < 0) \
460                         goto err_label; \
461                 ptr--; \
462                 if (put_user(val_byte(__val, 2), base + ptr) < 0) \
463                         goto err_label; \
464                 ptr--; \
465                 if (put_user(val_byte(__val, 1), base + ptr) < 0) \
466                         goto err_label; \
467                 ptr--; \
468                 if (put_user(val_byte(__val, 0), base + ptr) < 0) \
469                         goto err_label; \
470         } while (0)
471 
472 #define popb(base, ptr, err_label) \
473         ({ \
474                 __u8 __res; \
475                 if (get_user(__res, base + ptr) < 0) \
476                         goto err_label; \
477                 ptr++; \
478                 __res; \
479         })
480 
481 #define popw(base, ptr, err_label) \
482         ({ \
483                 __u16 __res; \
484                 if (get_user(val_byte(__res, 0), base + ptr) < 0) \
485                         goto err_label; \
486                 ptr++; \
487                 if (get_user(val_byte(__res, 1), base + ptr) < 0) \
488                         goto err_label; \
489                 ptr++; \
490                 __res; \
491         })
492 
493 #define popl(base, ptr, err_label) \
494         ({ \
495                 __u32 __res; \
496                 if (get_user(val_byte(__res, 0), base + ptr) < 0) \
497                         goto err_label; \
498                 ptr++; \
499                 if (get_user(val_byte(__res, 1), base + ptr) < 0) \
500                         goto err_label; \
501                 ptr++; \
502                 if (get_user(val_byte(__res, 2), base + ptr) < 0) \
503                         goto err_label; \
504                 ptr++; \
505                 if (get_user(val_byte(__res, 3), base + ptr) < 0) \
506                         goto err_label; \
507                 ptr++; \
508                 __res; \
509         })
510 
511 /* There are so many possible reasons for this function to return
512  * VM86_INTx, so adding another doesn't bother me. We can expect
513  * userspace programs to be able to handle it. (Getting a problem
514  * in userspace is always better than an Oops anyway.) [KD]
515  */
516 static void do_int(struct kernel_vm86_regs *regs, int i,
517     unsigned char __user *ssp, unsigned short sp)
518 {
519         unsigned long __user *intr_ptr;
520         unsigned long segoffs;
521 
522         if (regs->pt.cs == BIOSSEG)
523                 goto cannot_handle;
524         if (is_revectored(i, &KVM86->int_revectored))
525                 goto cannot_handle;
526         if (i == 0x21 && is_revectored(AH(regs), &KVM86->int21_revectored))
527                 goto cannot_handle;
528         intr_ptr = (unsigned long __user *) (i << 2);
529         if (get_user(segoffs, intr_ptr))
530                 goto cannot_handle;
531         if ((segoffs >> 16) == BIOSSEG)
532                 goto cannot_handle;
533         pushw(ssp, sp, get_vflags(regs), cannot_handle);
534         pushw(ssp, sp, regs->pt.cs, cannot_handle);
535         pushw(ssp, sp, IP(regs), cannot_handle);
536         regs->pt.cs = segoffs >> 16;
537         SP(regs) -= 6;
538         IP(regs) = segoffs & 0xffff;
539         clear_TF(regs);
540         clear_IF(regs);
541         clear_AC(regs);
542         return;
543 
544 cannot_handle:
545         return_to_32bit(regs, VM86_INTx + (i << 8));
546 }
547 
548 int handle_vm86_trap(struct kernel_vm86_regs *regs, long error_code, int trapno)
549 {
550         if (VMPI.is_vm86pus) {
551                 if ((trapno == 3) || (trapno == 1)) {
552                         KVM86->regs32->ax = VM86_TRAP + (trapno << 8);
553                         /* setting this flag forces the code in entry_32.S to
554                            the path where we call save_v86_state() and change
555                            the stack pointer to KVM86->regs32 */
556                         set_thread_flag(TIF_NOTIFY_RESUME);
557                         return 0;
558                 }
559                 do_int(regs, trapno, (unsigned char __user *) (regs->pt.ss << 4), SP(regs));
560                 return 0;
561         }
562         if (trapno != 1)
563                 return 1; /* we let this handle by the calling routine */
564         current->thread.trap_nr = trapno;
565         current->thread.error_code = error_code;
566         force_sig(SIGTRAP, current);
567         return 0;
568 }
569 
570 void handle_vm86_fault(struct kernel_vm86_regs *regs, long error_code)
571 {
572         unsigned char opcode;
573         unsigned char __user *csp;
574         unsigned char __user *ssp;
575         unsigned short ip, sp, orig_flags;
576         int data32, pref_done;
577 
578 #define CHECK_IF_IN_TRAP \
579         if (VMPI.vm86dbg_active && VMPI.vm86dbg_TFpendig) \
580                 newflags |= X86_EFLAGS_TF
581 #define VM86_FAULT_RETURN do { \
582         if (VMPI.force_return_for_pic  && (VEFLAGS & (X86_EFLAGS_IF | X86_EFLAGS_VIF))) \
583                 return_to_32bit(regs, VM86_PICRETURN); \
584         if (orig_flags & X86_EFLAGS_TF) \
585                 handle_vm86_trap(regs, 0, 1); \
586         return; } while (0)
587 
588         orig_flags = *(unsigned short *)&regs->pt.flags;
589 
590         csp = (unsigned char __user *) (regs->pt.cs << 4);
591         ssp = (unsigned char __user *) (regs->pt.ss << 4);
592         sp = SP(regs);
593         ip = IP(regs);
594 
595         data32 = 0;
596         pref_done = 0;
597         do {
598                 switch (opcode = popb(csp, ip, simulate_sigsegv)) {
599                 case 0x66:      /* 32-bit data */     data32 = 1; break;
600                 case 0x67:      /* 32-bit address */  break;
601                 case 0x2e:      /* CS */              break;
602                 case 0x3e:      /* DS */              break;
603                 case 0x26:      /* ES */              break;
604                 case 0x36:      /* SS */              break;
605                 case 0x65:      /* GS */              break;
606                 case 0x64:      /* FS */              break;
607                 case 0xf2:      /* repnz */       break;
608                 case 0xf3:      /* rep */             break;
609                 default: pref_done = 1;
610                 }
611         } while (!pref_done);
612 
613         switch (opcode) {
614 
615         /* pushf */
616         case 0x9c:
617                 if (data32) {
618                         pushl(ssp, sp, get_vflags(regs), simulate_sigsegv);
619                         SP(regs) -= 4;
620                 } else {
621                         pushw(ssp, sp, get_vflags(regs), simulate_sigsegv);
622                         SP(regs) -= 2;
623                 }
624                 IP(regs) = ip;
625                 VM86_FAULT_RETURN;
626 
627         /* popf */
628         case 0x9d:
629                 {
630                 unsigned long newflags;
631                 if (data32) {
632                         newflags = popl(ssp, sp, simulate_sigsegv);
633                         SP(regs) += 4;
634                 } else {
635                         newflags = popw(ssp, sp, simulate_sigsegv);
636                         SP(regs) += 2;
637                 }
638                 IP(regs) = ip;
639                 CHECK_IF_IN_TRAP;
640                 if (data32)
641                         set_vflags_long(newflags, regs);
642                 else
643                         set_vflags_short(newflags, regs);
644 
645                 VM86_FAULT_RETURN;
646                 }
647 
648         /* int xx */
649         case 0xcd: {
650                 int intno = popb(csp, ip, simulate_sigsegv);
651                 IP(regs) = ip;
652                 if (VMPI.vm86dbg_active) {
653                         if ((1 << (intno & 7)) & VMPI.vm86dbg_intxxtab[intno >> 3])
654                                 return_to_32bit(regs, VM86_INTx + (intno << 8));
655                 }
656                 do_int(regs, intno, ssp, sp);
657                 return;
658         }
659 
660         /* iret */
661         case 0xcf:
662                 {
663                 unsigned long newip;
664                 unsigned long newcs;
665                 unsigned long newflags;
666                 if (data32) {
667                         newip = popl(ssp, sp, simulate_sigsegv);
668                         newcs = popl(ssp, sp, simulate_sigsegv);
669                         newflags = popl(ssp, sp, simulate_sigsegv);
670                         SP(regs) += 12;
671                 } else {
672                         newip = popw(ssp, sp, simulate_sigsegv);
673                         newcs = popw(ssp, sp, simulate_sigsegv);
674                         newflags = popw(ssp, sp, simulate_sigsegv);
675                         SP(regs) += 6;
676                 }
677                 IP(regs) = newip;
678                 regs->pt.cs = newcs;
679                 CHECK_IF_IN_TRAP;
680                 if (data32) {
681                         set_vflags_long(newflags, regs);
682                 } else {
683                         set_vflags_short(newflags, regs);
684                 }
685                 VM86_FAULT_RETURN;
686                 }
687 
688         /* cli */
689         case 0xfa:
690                 IP(regs) = ip;
691                 clear_IF(regs);
692                 VM86_FAULT_RETURN;
693 
694         /* sti */
695         /*
696          * Damn. This is incorrect: the 'sti' instruction should actually
697          * enable interrupts after the /next/ instruction. Not good.
698          *
699          * Probably needs some horsing around with the TF flag. Aiee..
700          */
701         case 0xfb:
702                 IP(regs) = ip;
703                 set_IF(regs);
704                 VM86_FAULT_RETURN;
705 
706         default:
707                 return_to_32bit(regs, VM86_UNKNOWN);
708         }
709 
710         return;
711 
712 simulate_sigsegv:
713         /* FIXME: After a long discussion with Stas we finally
714          *        agreed, that this is wrong. Here we should
715          *        really send a SIGSEGV to the user program.
716          *        But how do we create the correct context? We
717          *        are inside a general protection fault handler
718          *        and has just returned from a page fault handler.
719          *        The correct context for the signal handler
720          *        should be a mixture of the two, but how do we
721          *        get the information? [KD]
722          */
723         return_to_32bit(regs, VM86_UNKNOWN);
724 }
725 
726 /* ---------------- vm86 special IRQ passing stuff ----------------- */
727 
728 #define VM86_IRQNAME            "vm86irq"
729 
730 static struct vm86_irqs {
731         struct task_struct *tsk;
732         int sig;
733 } vm86_irqs[16];
734 
735 static DEFINE_SPINLOCK(irqbits_lock);
736 static int irqbits;
737 
738 #define ALLOWED_SIGS (1 /* 0 = don't send a signal */ \
739         | (1 << SIGUSR1) | (1 << SIGUSR2) | (1 << SIGIO)  | (1 << SIGURG) \
740         | (1 << SIGUNUSED))
741 
742 static irqreturn_t irq_handler(int intno, void *dev_id)
743 {
744         int irq_bit;
745         unsigned long flags;
746 
747         spin_lock_irqsave(&irqbits_lock, flags);
748         irq_bit = 1 << intno;
749         if ((irqbits & irq_bit) || !vm86_irqs[intno].tsk)
750                 goto out;
751         irqbits |= irq_bit;
752         if (vm86_irqs[intno].sig)
753                 send_sig(vm86_irqs[intno].sig, vm86_irqs[intno].tsk, 1);
754         /*
755          * IRQ will be re-enabled when user asks for the irq (whether
756          * polling or as a result of the signal)
757          */
758         disable_irq_nosync(intno);
759         spin_unlock_irqrestore(&irqbits_lock, flags);
760         return IRQ_HANDLED;
761 
762 out:
763         spin_unlock_irqrestore(&irqbits_lock, flags);
764         return IRQ_NONE;
765 }
766 
767 static inline void free_vm86_irq(int irqnumber)
768 {
769         unsigned long flags;
770 
771         free_irq(irqnumber, NULL);
772         vm86_irqs[irqnumber].tsk = NULL;
773 
774         spin_lock_irqsave(&irqbits_lock, flags);
775         irqbits &= ~(1 << irqnumber);
776         spin_unlock_irqrestore(&irqbits_lock, flags);
777 }
778 
779 void release_vm86_irqs(struct task_struct *task)
780 {
781         int i;
782         for (i = FIRST_VM86_IRQ ; i <= LAST_VM86_IRQ; i++)
783             if (vm86_irqs[i].tsk == task)
784                 free_vm86_irq(i);
785 }
786 
787 static inline int get_and_reset_irq(int irqnumber)
788 {
789         int bit;
790         unsigned long flags;
791         int ret = 0;
792 
793         if (invalid_vm86_irq(irqnumber)) return 0;
794         if (vm86_irqs[irqnumber].tsk != current) return 0;
795         spin_lock_irqsave(&irqbits_lock, flags);
796         bit = irqbits & (1 << irqnumber);
797         irqbits &= ~bit;
798         if (bit) {
799                 enable_irq(irqnumber);
800                 ret = 1;
801         }
802 
803         spin_unlock_irqrestore(&irqbits_lock, flags);
804         return ret;
805 }
806 
807 
808 static int do_vm86_irq_handling(int subfunction, int irqnumber)
809 {
810         int ret;
811         switch (subfunction) {
812                 case VM86_GET_AND_RESET_IRQ: {
813                         return get_and_reset_irq(irqnumber);
814                 }
815                 case VM86_GET_IRQ_BITS: {
816                         return irqbits;
817                 }
818                 case VM86_REQUEST_IRQ: {
819                         int sig = irqnumber >> 8;
820                         int irq = irqnumber & 255;
821                         if (!capable(CAP_SYS_ADMIN)) return -EPERM;
822                         if (!((1 << sig) & ALLOWED_SIGS)) return -EPERM;
823                         if (invalid_vm86_irq(irq)) return -EPERM;
824                         if (vm86_irqs[irq].tsk) return -EPERM;
825                         ret = request_irq(irq, &irq_handler, 0, VM86_IRQNAME, NULL);
826                         if (ret) return ret;
827                         vm86_irqs[irq].sig = sig;
828                         vm86_irqs[irq].tsk = current;
829                         return irq;
830                 }
831                 case  VM86_FREE_IRQ: {
832                         if (invalid_vm86_irq(irqnumber)) return -EPERM;
833                         if (!vm86_irqs[irqnumber].tsk) return 0;
834                         if (vm86_irqs[irqnumber].tsk != current) return -EPERM;
835                         free_vm86_irq(irqnumber);
836                         return 0;
837                 }
838         }
839         return -EINVAL;
840 }
841 
842 

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