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TOMOYO Linux Cross Reference
Linux/arch/x86/kernel/vm86_32.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  *  Copyright (C) 1994  Linus Torvalds
  4  *
  5  *  29 dec 2001 - Fixed oopses caused by unchecked access to the vm86
  6  *                stack - Manfred Spraul <manfred@colorfullife.com>
  7  *
  8  *  22 mar 2002 - Manfred detected the stackfaults, but didn't handle
  9  *                them correctly. Now the emulation will be in a
 10  *                consistent state after stackfaults - Kasper Dupont
 11  *                <kasperd@daimi.au.dk>
 12  *
 13  *  22 mar 2002 - Added missing clear_IF in set_vflags_* Kasper Dupont
 14  *                <kasperd@daimi.au.dk>
 15  *
 16  *  ?? ??? 2002 - Fixed premature returns from handle_vm86_fault
 17  *                caused by Kasper Dupont's changes - Stas Sergeev
 18  *
 19  *   4 apr 2002 - Fixed CHECK_IF_IN_TRAP broken by Stas' changes.
 20  *                Kasper Dupont <kasperd@daimi.au.dk>
 21  *
 22  *   9 apr 2002 - Changed syntax of macros in handle_vm86_fault.
 23  *                Kasper Dupont <kasperd@daimi.au.dk>
 24  *
 25  *   9 apr 2002 - Changed stack access macros to jump to a label
 26  *                instead of returning to userspace. This simplifies
 27  *                do_int, and is needed by handle_vm6_fault. Kasper
 28  *                Dupont <kasperd@daimi.au.dk>
 29  *
 30  */
 31 
 32 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 33 
 34 #include <linux/capability.h>
 35 #include <linux/errno.h>
 36 #include <linux/interrupt.h>
 37 #include <linux/syscalls.h>
 38 #include <linux/sched.h>
 39 #include <linux/sched/task_stack.h>
 40 #include <linux/kernel.h>
 41 #include <linux/signal.h>
 42 #include <linux/string.h>
 43 #include <linux/mm.h>
 44 #include <linux/smp.h>
 45 #include <linux/highmem.h>
 46 #include <linux/ptrace.h>
 47 #include <linux/audit.h>
 48 #include <linux/stddef.h>
 49 #include <linux/slab.h>
 50 #include <linux/security.h>
 51 
 52 #include <linux/uaccess.h>
 53 #include <asm/io.h>
 54 #include <asm/tlbflush.h>
 55 #include <asm/irq.h>
 56 #include <asm/traps.h>
 57 #include <asm/vm86.h>
 58 #include <asm/switch_to.h>
 59 
 60 /*
 61  * Known problems:
 62  *
 63  * Interrupt handling is not guaranteed:
 64  * - a real x86 will disable all interrupts for one instruction
 65  *   after a "mov ss,xx" to make stack handling atomic even without
 66  *   the 'lss' instruction. We can't guarantee this in v86 mode,
 67  *   as the next instruction might result in a page fault or similar.
 68  * - a real x86 will have interrupts disabled for one instruction
 69  *   past the 'sti' that enables them. We don't bother with all the
 70  *   details yet.
 71  *
 72  * Let's hope these problems do not actually matter for anything.
 73  */
 74 
 75 
 76 /*
 77  * 8- and 16-bit register defines..
 78  */
 79 #define AL(regs)        (((unsigned char *)&((regs)->pt.ax))[0])
 80 #define AH(regs)        (((unsigned char *)&((regs)->pt.ax))[1])
 81 #define IP(regs)        (*(unsigned short *)&((regs)->pt.ip))
 82 #define SP(regs)        (*(unsigned short *)&((regs)->pt.sp))
 83 
 84 /*
 85  * virtual flags (16 and 32-bit versions)
 86  */
 87 #define VFLAGS  (*(unsigned short *)&(current->thread.vm86->veflags))
 88 #define VEFLAGS (current->thread.vm86->veflags)
 89 
 90 #define set_flags(X, new, mask) \
 91 ((X) = ((X) & ~(mask)) | ((new) & (mask)))
 92 
 93 #define SAFE_MASK       (0xDD5)
 94 #define RETURN_MASK     (0xDFF)
 95 
 96 void save_v86_state(struct kernel_vm86_regs *regs, int retval)
 97 {
 98         struct task_struct *tsk = current;
 99         struct vm86plus_struct __user *user;
100         struct vm86 *vm86 = current->thread.vm86;
101         long err = 0;
102 
103         /*
104          * This gets called from entry.S with interrupts disabled, but
105          * from process context. Enable interrupts here, before trying
106          * to access user space.
107          */
108         local_irq_enable();
109 
110         if (!vm86 || !vm86->user_vm86) {
111                 pr_alert("no user_vm86: BAD\n");
112                 do_exit(SIGSEGV);
113         }
114         set_flags(regs->pt.flags, VEFLAGS, X86_EFLAGS_VIF | vm86->veflags_mask);
115         user = vm86->user_vm86;
116 
117         if (!access_ok(VERIFY_WRITE, user, vm86->vm86plus.is_vm86pus ?
118                        sizeof(struct vm86plus_struct) :
119                        sizeof(struct vm86_struct))) {
120                 pr_alert("could not access userspace vm86 info\n");
121                 do_exit(SIGSEGV);
122         }
123 
124         put_user_try {
125                 put_user_ex(regs->pt.bx, &user->regs.ebx);
126                 put_user_ex(regs->pt.cx, &user->regs.ecx);
127                 put_user_ex(regs->pt.dx, &user->regs.edx);
128                 put_user_ex(regs->pt.si, &user->regs.esi);
129                 put_user_ex(regs->pt.di, &user->regs.edi);
130                 put_user_ex(regs->pt.bp, &user->regs.ebp);
131                 put_user_ex(regs->pt.ax, &user->regs.eax);
132                 put_user_ex(regs->pt.ip, &user->regs.eip);
133                 put_user_ex(regs->pt.cs, &user->regs.cs);
134                 put_user_ex(regs->pt.flags, &user->regs.eflags);
135                 put_user_ex(regs->pt.sp, &user->regs.esp);
136                 put_user_ex(regs->pt.ss, &user->regs.ss);
137                 put_user_ex(regs->es, &user->regs.es);
138                 put_user_ex(regs->ds, &user->regs.ds);
139                 put_user_ex(regs->fs, &user->regs.fs);
140                 put_user_ex(regs->gs, &user->regs.gs);
141 
142                 put_user_ex(vm86->screen_bitmap, &user->screen_bitmap);
143         } put_user_catch(err);
144         if (err) {
145                 pr_alert("could not access userspace vm86 info\n");
146                 do_exit(SIGSEGV);
147         }
148 
149         preempt_disable();
150         tsk->thread.sp0 = vm86->saved_sp0;
151         tsk->thread.sysenter_cs = __KERNEL_CS;
152         update_task_stack(tsk);
153         refresh_sysenter_cs(&tsk->thread);
154         vm86->saved_sp0 = 0;
155         preempt_enable();
156 
157         memcpy(&regs->pt, &vm86->regs32, sizeof(struct pt_regs));
158 
159         lazy_load_gs(vm86->regs32.gs);
160 
161         regs->pt.ax = retval;
162 }
163 
164 static void mark_screen_rdonly(struct mm_struct *mm)
165 {
166         struct vm_area_struct *vma;
167         spinlock_t *ptl;
168         pgd_t *pgd;
169         p4d_t *p4d;
170         pud_t *pud;
171         pmd_t *pmd;
172         pte_t *pte;
173         int i;
174 
175         down_write(&mm->mmap_sem);
176         pgd = pgd_offset(mm, 0xA0000);
177         if (pgd_none_or_clear_bad(pgd))
178                 goto out;
179         p4d = p4d_offset(pgd, 0xA0000);
180         if (p4d_none_or_clear_bad(p4d))
181                 goto out;
182         pud = pud_offset(p4d, 0xA0000);
183         if (pud_none_or_clear_bad(pud))
184                 goto out;
185         pmd = pmd_offset(pud, 0xA0000);
186 
187         if (pmd_trans_huge(*pmd)) {
188                 vma = find_vma(mm, 0xA0000);
189                 split_huge_pmd(vma, pmd, 0xA0000);
190         }
191         if (pmd_none_or_clear_bad(pmd))
192                 goto out;
193         pte = pte_offset_map_lock(mm, pmd, 0xA0000, &ptl);
194         for (i = 0; i < 32; i++) {
195                 if (pte_present(*pte))
196                         set_pte(pte, pte_wrprotect(*pte));
197                 pte++;
198         }
199         pte_unmap_unlock(pte, ptl);
200 out:
201         up_write(&mm->mmap_sem);
202         flush_tlb_mm_range(mm, 0xA0000, 0xA0000 + 32*PAGE_SIZE, PAGE_SHIFT, false);
203 }
204 
205 
206 
207 static int do_vm86_irq_handling(int subfunction, int irqnumber);
208 static long do_sys_vm86(struct vm86plus_struct __user *user_vm86, bool plus);
209 
210 SYSCALL_DEFINE1(vm86old, struct vm86_struct __user *, user_vm86)
211 {
212         return do_sys_vm86((struct vm86plus_struct __user *) user_vm86, false);
213 }
214 
215 
216 SYSCALL_DEFINE2(vm86, unsigned long, cmd, unsigned long, arg)
217 {
218         switch (cmd) {
219         case VM86_REQUEST_IRQ:
220         case VM86_FREE_IRQ:
221         case VM86_GET_IRQ_BITS:
222         case VM86_GET_AND_RESET_IRQ:
223                 return do_vm86_irq_handling(cmd, (int)arg);
224         case VM86_PLUS_INSTALL_CHECK:
225                 /*
226                  * NOTE: on old vm86 stuff this will return the error
227                  *  from access_ok(), because the subfunction is
228                  *  interpreted as (invalid) address to vm86_struct.
229                  *  So the installation check works.
230                  */
231                 return 0;
232         }
233 
234         /* we come here only for functions VM86_ENTER, VM86_ENTER_NO_BYPASS */
235         return do_sys_vm86((struct vm86plus_struct __user *) arg, true);
236 }
237 
238 
239 static long do_sys_vm86(struct vm86plus_struct __user *user_vm86, bool plus)
240 {
241         struct task_struct *tsk = current;
242         struct vm86 *vm86 = tsk->thread.vm86;
243         struct kernel_vm86_regs vm86regs;
244         struct pt_regs *regs = current_pt_regs();
245         unsigned long err = 0;
246 
247         err = security_mmap_addr(0);
248         if (err) {
249                 /*
250                  * vm86 cannot virtualize the address space, so vm86 users
251                  * need to manage the low 1MB themselves using mmap.  Given
252                  * that BIOS places important data in the first page, vm86
253                  * is essentially useless if mmap_min_addr != 0.  DOSEMU,
254                  * for example, won't even bother trying to use vm86 if it
255                  * can't map a page at virtual address 0.
256                  *
257                  * To reduce the available kernel attack surface, simply
258                  * disallow vm86(old) for users who cannot mmap at va 0.
259                  *
260                  * The implementation of security_mmap_addr will allow
261                  * suitably privileged users to map va 0 even if
262                  * vm.mmap_min_addr is set above 0, and we want this
263                  * behavior for vm86 as well, as it ensures that legacy
264                  * tools like vbetool will not fail just because of
265                  * vm.mmap_min_addr.
266                  */
267                 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",
268                              current->comm, task_pid_nr(current),
269                              from_kuid_munged(&init_user_ns, current_uid()));
270                 return -EPERM;
271         }
272 
273         if (!vm86) {
274                 if (!(vm86 = kzalloc(sizeof(*vm86), GFP_KERNEL)))
275                         return -ENOMEM;
276                 tsk->thread.vm86 = vm86;
277         }
278         if (vm86->saved_sp0)
279                 return -EPERM;
280 
281         if (!access_ok(VERIFY_READ, user_vm86, plus ?
282                        sizeof(struct vm86_struct) :
283                        sizeof(struct vm86plus_struct)))
284                 return -EFAULT;
285 
286         memset(&vm86regs, 0, sizeof(vm86regs));
287         get_user_try {
288                 unsigned short seg;
289                 get_user_ex(vm86regs.pt.bx, &user_vm86->regs.ebx);
290                 get_user_ex(vm86regs.pt.cx, &user_vm86->regs.ecx);
291                 get_user_ex(vm86regs.pt.dx, &user_vm86->regs.edx);
292                 get_user_ex(vm86regs.pt.si, &user_vm86->regs.esi);
293                 get_user_ex(vm86regs.pt.di, &user_vm86->regs.edi);
294                 get_user_ex(vm86regs.pt.bp, &user_vm86->regs.ebp);
295                 get_user_ex(vm86regs.pt.ax, &user_vm86->regs.eax);
296                 get_user_ex(vm86regs.pt.ip, &user_vm86->regs.eip);
297                 get_user_ex(seg, &user_vm86->regs.cs);
298                 vm86regs.pt.cs = seg;
299                 get_user_ex(vm86regs.pt.flags, &user_vm86->regs.eflags);
300                 get_user_ex(vm86regs.pt.sp, &user_vm86->regs.esp);
301                 get_user_ex(seg, &user_vm86->regs.ss);
302                 vm86regs.pt.ss = seg;
303                 get_user_ex(vm86regs.es, &user_vm86->regs.es);
304                 get_user_ex(vm86regs.ds, &user_vm86->regs.ds);
305                 get_user_ex(vm86regs.fs, &user_vm86->regs.fs);
306                 get_user_ex(vm86regs.gs, &user_vm86->regs.gs);
307 
308                 get_user_ex(vm86->flags, &user_vm86->flags);
309                 get_user_ex(vm86->screen_bitmap, &user_vm86->screen_bitmap);
310                 get_user_ex(vm86->cpu_type, &user_vm86->cpu_type);
311         } get_user_catch(err);
312         if (err)
313                 return err;
314 
315         if (copy_from_user(&vm86->int_revectored,
316                            &user_vm86->int_revectored,
317                            sizeof(struct revectored_struct)))
318                 return -EFAULT;
319         if (copy_from_user(&vm86->int21_revectored,
320                            &user_vm86->int21_revectored,
321                            sizeof(struct revectored_struct)))
322                 return -EFAULT;
323         if (plus) {
324                 if (copy_from_user(&vm86->vm86plus, &user_vm86->vm86plus,
325                                    sizeof(struct vm86plus_info_struct)))
326                         return -EFAULT;
327                 vm86->vm86plus.is_vm86pus = 1;
328         } else
329                 memset(&vm86->vm86plus, 0,
330                        sizeof(struct vm86plus_info_struct));
331 
332         memcpy(&vm86->regs32, regs, sizeof(struct pt_regs));
333         vm86->user_vm86 = user_vm86;
334 
335 /*
336  * The flags register is also special: we cannot trust that the user
337  * has set it up safely, so this makes sure interrupt etc flags are
338  * inherited from protected mode.
339  */
340         VEFLAGS = vm86regs.pt.flags;
341         vm86regs.pt.flags &= SAFE_MASK;
342         vm86regs.pt.flags |= regs->flags & ~SAFE_MASK;
343         vm86regs.pt.flags |= X86_VM_MASK;
344 
345         vm86regs.pt.orig_ax = regs->orig_ax;
346 
347         switch (vm86->cpu_type) {
348         case CPU_286:
349                 vm86->veflags_mask = 0;
350                 break;
351         case CPU_386:
352                 vm86->veflags_mask = X86_EFLAGS_NT | X86_EFLAGS_IOPL;
353                 break;
354         case CPU_486:
355                 vm86->veflags_mask = X86_EFLAGS_AC | X86_EFLAGS_NT | X86_EFLAGS_IOPL;
356                 break;
357         default:
358                 vm86->veflags_mask = X86_EFLAGS_ID | X86_EFLAGS_AC | X86_EFLAGS_NT | X86_EFLAGS_IOPL;
359                 break;
360         }
361 
362 /*
363  * Save old state
364  */
365         vm86->saved_sp0 = tsk->thread.sp0;
366         lazy_save_gs(vm86->regs32.gs);
367 
368         /* make room for real-mode segments */
369         preempt_disable();
370         tsk->thread.sp0 += 16;
371 
372         if (static_cpu_has(X86_FEATURE_SEP)) {
373                 tsk->thread.sysenter_cs = 0;
374                 refresh_sysenter_cs(&tsk->thread);
375         }
376 
377         update_task_stack(tsk);
378         preempt_enable();
379 
380         if (vm86->flags & VM86_SCREEN_BITMAP)
381                 mark_screen_rdonly(tsk->mm);
382 
383         memcpy((struct kernel_vm86_regs *)regs, &vm86regs, sizeof(vm86regs));
384         force_iret();
385         return regs->ax;
386 }
387 
388 static inline void set_IF(struct kernel_vm86_regs *regs)
389 {
390         VEFLAGS |= X86_EFLAGS_VIF;
391 }
392 
393 static inline void clear_IF(struct kernel_vm86_regs *regs)
394 {
395         VEFLAGS &= ~X86_EFLAGS_VIF;
396 }
397 
398 static inline void clear_TF(struct kernel_vm86_regs *regs)
399 {
400         regs->pt.flags &= ~X86_EFLAGS_TF;
401 }
402 
403 static inline void clear_AC(struct kernel_vm86_regs *regs)
404 {
405         regs->pt.flags &= ~X86_EFLAGS_AC;
406 }
407 
408 /*
409  * It is correct to call set_IF(regs) from the set_vflags_*
410  * functions. However someone forgot to call clear_IF(regs)
411  * in the opposite case.
412  * After the command sequence CLI PUSHF STI POPF you should
413  * end up with interrupts disabled, but you ended up with
414  * interrupts enabled.
415  *  ( I was testing my own changes, but the only bug I
416  *    could find was in a function I had not changed. )
417  * [KD]
418  */
419 
420 static inline void set_vflags_long(unsigned long flags, struct kernel_vm86_regs *regs)
421 {
422         set_flags(VEFLAGS, flags, current->thread.vm86->veflags_mask);
423         set_flags(regs->pt.flags, flags, SAFE_MASK);
424         if (flags & X86_EFLAGS_IF)
425                 set_IF(regs);
426         else
427                 clear_IF(regs);
428 }
429 
430 static inline void set_vflags_short(unsigned short flags, struct kernel_vm86_regs *regs)
431 {
432         set_flags(VFLAGS, flags, current->thread.vm86->veflags_mask);
433         set_flags(regs->pt.flags, flags, SAFE_MASK);
434         if (flags & X86_EFLAGS_IF)
435                 set_IF(regs);
436         else
437                 clear_IF(regs);
438 }
439 
440 static inline unsigned long get_vflags(struct kernel_vm86_regs *regs)
441 {
442         unsigned long flags = regs->pt.flags & RETURN_MASK;
443 
444         if (VEFLAGS & X86_EFLAGS_VIF)
445                 flags |= X86_EFLAGS_IF;
446         flags |= X86_EFLAGS_IOPL;
447         return flags | (VEFLAGS & current->thread.vm86->veflags_mask);
448 }
449 
450 static inline int is_revectored(int nr, struct revectored_struct *bitmap)
451 {
452         return test_bit(nr, bitmap->__map);
453 }
454 
455 #define val_byte(val, n) (((__u8 *)&val)[n])
456 
457 #define pushb(base, ptr, val, err_label) \
458         do { \
459                 __u8 __val = val; \
460                 ptr--; \
461                 if (put_user(__val, base + ptr) < 0) \
462                         goto err_label; \
463         } while (0)
464 
465 #define pushw(base, ptr, val, err_label) \
466         do { \
467                 __u16 __val = val; \
468                 ptr--; \
469                 if (put_user(val_byte(__val, 1), base + ptr) < 0) \
470                         goto err_label; \
471                 ptr--; \
472                 if (put_user(val_byte(__val, 0), base + ptr) < 0) \
473                         goto err_label; \
474         } while (0)
475 
476 #define pushl(base, ptr, val, err_label) \
477         do { \
478                 __u32 __val = val; \
479                 ptr--; \
480                 if (put_user(val_byte(__val, 3), base + ptr) < 0) \
481                         goto err_label; \
482                 ptr--; \
483                 if (put_user(val_byte(__val, 2), base + ptr) < 0) \
484                         goto err_label; \
485                 ptr--; \
486                 if (put_user(val_byte(__val, 1), base + ptr) < 0) \
487                         goto err_label; \
488                 ptr--; \
489                 if (put_user(val_byte(__val, 0), base + ptr) < 0) \
490                         goto err_label; \
491         } while (0)
492 
493 #define popb(base, ptr, err_label) \
494         ({ \
495                 __u8 __res; \
496                 if (get_user(__res, base + ptr) < 0) \
497                         goto err_label; \
498                 ptr++; \
499                 __res; \
500         })
501 
502 #define popw(base, ptr, err_label) \
503         ({ \
504                 __u16 __res; \
505                 if (get_user(val_byte(__res, 0), base + ptr) < 0) \
506                         goto err_label; \
507                 ptr++; \
508                 if (get_user(val_byte(__res, 1), base + ptr) < 0) \
509                         goto err_label; \
510                 ptr++; \
511                 __res; \
512         })
513 
514 #define popl(base, ptr, err_label) \
515         ({ \
516                 __u32 __res; \
517                 if (get_user(val_byte(__res, 0), base + ptr) < 0) \
518                         goto err_label; \
519                 ptr++; \
520                 if (get_user(val_byte(__res, 1), base + ptr) < 0) \
521                         goto err_label; \
522                 ptr++; \
523                 if (get_user(val_byte(__res, 2), base + ptr) < 0) \
524                         goto err_label; \
525                 ptr++; \
526                 if (get_user(val_byte(__res, 3), base + ptr) < 0) \
527                         goto err_label; \
528                 ptr++; \
529                 __res; \
530         })
531 
532 /* There are so many possible reasons for this function to return
533  * VM86_INTx, so adding another doesn't bother me. We can expect
534  * userspace programs to be able to handle it. (Getting a problem
535  * in userspace is always better than an Oops anyway.) [KD]
536  */
537 static void do_int(struct kernel_vm86_regs *regs, int i,
538     unsigned char __user *ssp, unsigned short sp)
539 {
540         unsigned long __user *intr_ptr;
541         unsigned long segoffs;
542         struct vm86 *vm86 = current->thread.vm86;
543 
544         if (regs->pt.cs == BIOSSEG)
545                 goto cannot_handle;
546         if (is_revectored(i, &vm86->int_revectored))
547                 goto cannot_handle;
548         if (i == 0x21 && is_revectored(AH(regs), &vm86->int21_revectored))
549                 goto cannot_handle;
550         intr_ptr = (unsigned long __user *) (i << 2);
551         if (get_user(segoffs, intr_ptr))
552                 goto cannot_handle;
553         if ((segoffs >> 16) == BIOSSEG)
554                 goto cannot_handle;
555         pushw(ssp, sp, get_vflags(regs), cannot_handle);
556         pushw(ssp, sp, regs->pt.cs, cannot_handle);
557         pushw(ssp, sp, IP(regs), cannot_handle);
558         regs->pt.cs = segoffs >> 16;
559         SP(regs) -= 6;
560         IP(regs) = segoffs & 0xffff;
561         clear_TF(regs);
562         clear_IF(regs);
563         clear_AC(regs);
564         return;
565 
566 cannot_handle:
567         save_v86_state(regs, VM86_INTx + (i << 8));
568 }
569 
570 int handle_vm86_trap(struct kernel_vm86_regs *regs, long error_code, int trapno)
571 {
572         struct vm86 *vm86 = current->thread.vm86;
573 
574         if (vm86->vm86plus.is_vm86pus) {
575                 if ((trapno == 3) || (trapno == 1)) {
576                         save_v86_state(regs, VM86_TRAP + (trapno << 8));
577                         return 0;
578                 }
579                 do_int(regs, trapno, (unsigned char __user *) (regs->pt.ss << 4), SP(regs));
580                 return 0;
581         }
582         if (trapno != 1)
583                 return 1; /* we let this handle by the calling routine */
584         current->thread.trap_nr = trapno;
585         current->thread.error_code = error_code;
586         force_sig(SIGTRAP, current);
587         return 0;
588 }
589 
590 void handle_vm86_fault(struct kernel_vm86_regs *regs, long error_code)
591 {
592         unsigned char opcode;
593         unsigned char __user *csp;
594         unsigned char __user *ssp;
595         unsigned short ip, sp, orig_flags;
596         int data32, pref_done;
597         struct vm86plus_info_struct *vmpi = &current->thread.vm86->vm86plus;
598 
599 #define CHECK_IF_IN_TRAP \
600         if (vmpi->vm86dbg_active && vmpi->vm86dbg_TFpendig) \
601                 newflags |= X86_EFLAGS_TF
602 
603         orig_flags = *(unsigned short *)&regs->pt.flags;
604 
605         csp = (unsigned char __user *) (regs->pt.cs << 4);
606         ssp = (unsigned char __user *) (regs->pt.ss << 4);
607         sp = SP(regs);
608         ip = IP(regs);
609 
610         data32 = 0;
611         pref_done = 0;
612         do {
613                 switch (opcode = popb(csp, ip, simulate_sigsegv)) {
614                 case 0x66:      /* 32-bit data */     data32 = 1; break;
615                 case 0x67:      /* 32-bit address */  break;
616                 case 0x2e:      /* CS */              break;
617                 case 0x3e:      /* DS */              break;
618                 case 0x26:      /* ES */              break;
619                 case 0x36:      /* SS */              break;
620                 case 0x65:      /* GS */              break;
621                 case 0x64:      /* FS */              break;
622                 case 0xf2:      /* repnz */       break;
623                 case 0xf3:      /* rep */             break;
624                 default: pref_done = 1;
625                 }
626         } while (!pref_done);
627 
628         switch (opcode) {
629 
630         /* pushf */
631         case 0x9c:
632                 if (data32) {
633                         pushl(ssp, sp, get_vflags(regs), simulate_sigsegv);
634                         SP(regs) -= 4;
635                 } else {
636                         pushw(ssp, sp, get_vflags(regs), simulate_sigsegv);
637                         SP(regs) -= 2;
638                 }
639                 IP(regs) = ip;
640                 goto vm86_fault_return;
641 
642         /* popf */
643         case 0x9d:
644                 {
645                 unsigned long newflags;
646                 if (data32) {
647                         newflags = popl(ssp, sp, simulate_sigsegv);
648                         SP(regs) += 4;
649                 } else {
650                         newflags = popw(ssp, sp, simulate_sigsegv);
651                         SP(regs) += 2;
652                 }
653                 IP(regs) = ip;
654                 CHECK_IF_IN_TRAP;
655                 if (data32)
656                         set_vflags_long(newflags, regs);
657                 else
658                         set_vflags_short(newflags, regs);
659 
660                 goto check_vip;
661                 }
662 
663         /* int xx */
664         case 0xcd: {
665                 int intno = popb(csp, ip, simulate_sigsegv);
666                 IP(regs) = ip;
667                 if (vmpi->vm86dbg_active) {
668                         if ((1 << (intno & 7)) & vmpi->vm86dbg_intxxtab[intno >> 3]) {
669                                 save_v86_state(regs, VM86_INTx + (intno << 8));
670                                 return;
671                         }
672                 }
673                 do_int(regs, intno, ssp, sp);
674                 return;
675         }
676 
677         /* iret */
678         case 0xcf:
679                 {
680                 unsigned long newip;
681                 unsigned long newcs;
682                 unsigned long newflags;
683                 if (data32) {
684                         newip = popl(ssp, sp, simulate_sigsegv);
685                         newcs = popl(ssp, sp, simulate_sigsegv);
686                         newflags = popl(ssp, sp, simulate_sigsegv);
687                         SP(regs) += 12;
688                 } else {
689                         newip = popw(ssp, sp, simulate_sigsegv);
690                         newcs = popw(ssp, sp, simulate_sigsegv);
691                         newflags = popw(ssp, sp, simulate_sigsegv);
692                         SP(regs) += 6;
693                 }
694                 IP(regs) = newip;
695                 regs->pt.cs = newcs;
696                 CHECK_IF_IN_TRAP;
697                 if (data32) {
698                         set_vflags_long(newflags, regs);
699                 } else {
700                         set_vflags_short(newflags, regs);
701                 }
702                 goto check_vip;
703                 }
704 
705         /* cli */
706         case 0xfa:
707                 IP(regs) = ip;
708                 clear_IF(regs);
709                 goto vm86_fault_return;
710 
711         /* sti */
712         /*
713          * Damn. This is incorrect: the 'sti' instruction should actually
714          * enable interrupts after the /next/ instruction. Not good.
715          *
716          * Probably needs some horsing around with the TF flag. Aiee..
717          */
718         case 0xfb:
719                 IP(regs) = ip;
720                 set_IF(regs);
721                 goto check_vip;
722 
723         default:
724                 save_v86_state(regs, VM86_UNKNOWN);
725         }
726 
727         return;
728 
729 check_vip:
730         if ((VEFLAGS & (X86_EFLAGS_VIP | X86_EFLAGS_VIF)) ==
731             (X86_EFLAGS_VIP | X86_EFLAGS_VIF)) {
732                 save_v86_state(regs, VM86_STI);
733                 return;
734         }
735 
736 vm86_fault_return:
737         if (vmpi->force_return_for_pic  && (VEFLAGS & (X86_EFLAGS_IF | X86_EFLAGS_VIF))) {
738                 save_v86_state(regs, VM86_PICRETURN);
739                 return;
740         }
741         if (orig_flags & X86_EFLAGS_TF)
742                 handle_vm86_trap(regs, 0, X86_TRAP_DB);
743         return;
744 
745 simulate_sigsegv:
746         /* FIXME: After a long discussion with Stas we finally
747          *        agreed, that this is wrong. Here we should
748          *        really send a SIGSEGV to the user program.
749          *        But how do we create the correct context? We
750          *        are inside a general protection fault handler
751          *        and has just returned from a page fault handler.
752          *        The correct context for the signal handler
753          *        should be a mixture of the two, but how do we
754          *        get the information? [KD]
755          */
756         save_v86_state(regs, VM86_UNKNOWN);
757 }
758 
759 /* ---------------- vm86 special IRQ passing stuff ----------------- */
760 
761 #define VM86_IRQNAME            "vm86irq"
762 
763 static struct vm86_irqs {
764         struct task_struct *tsk;
765         int sig;
766 } vm86_irqs[16];
767 
768 static DEFINE_SPINLOCK(irqbits_lock);
769 static int irqbits;
770 
771 #define ALLOWED_SIGS (1 /* 0 = don't send a signal */ \
772         | (1 << SIGUSR1) | (1 << SIGUSR2) | (1 << SIGIO)  | (1 << SIGURG) \
773         | (1 << SIGUNUSED))
774 
775 static irqreturn_t irq_handler(int intno, void *dev_id)
776 {
777         int irq_bit;
778         unsigned long flags;
779 
780         spin_lock_irqsave(&irqbits_lock, flags);
781         irq_bit = 1 << intno;
782         if ((irqbits & irq_bit) || !vm86_irqs[intno].tsk)
783                 goto out;
784         irqbits |= irq_bit;
785         if (vm86_irqs[intno].sig)
786                 send_sig(vm86_irqs[intno].sig, vm86_irqs[intno].tsk, 1);
787         /*
788          * IRQ will be re-enabled when user asks for the irq (whether
789          * polling or as a result of the signal)
790          */
791         disable_irq_nosync(intno);
792         spin_unlock_irqrestore(&irqbits_lock, flags);
793         return IRQ_HANDLED;
794 
795 out:
796         spin_unlock_irqrestore(&irqbits_lock, flags);
797         return IRQ_NONE;
798 }
799 
800 static inline void free_vm86_irq(int irqnumber)
801 {
802         unsigned long flags;
803 
804         free_irq(irqnumber, NULL);
805         vm86_irqs[irqnumber].tsk = NULL;
806 
807         spin_lock_irqsave(&irqbits_lock, flags);
808         irqbits &= ~(1 << irqnumber);
809         spin_unlock_irqrestore(&irqbits_lock, flags);
810 }
811 
812 void release_vm86_irqs(struct task_struct *task)
813 {
814         int i;
815         for (i = FIRST_VM86_IRQ ; i <= LAST_VM86_IRQ; i++)
816             if (vm86_irqs[i].tsk == task)
817                 free_vm86_irq(i);
818 }
819 
820 static inline int get_and_reset_irq(int irqnumber)
821 {
822         int bit;
823         unsigned long flags;
824         int ret = 0;
825 
826         if (invalid_vm86_irq(irqnumber)) return 0;
827         if (vm86_irqs[irqnumber].tsk != current) return 0;
828         spin_lock_irqsave(&irqbits_lock, flags);
829         bit = irqbits & (1 << irqnumber);
830         irqbits &= ~bit;
831         if (bit) {
832                 enable_irq(irqnumber);
833                 ret = 1;
834         }
835 
836         spin_unlock_irqrestore(&irqbits_lock, flags);
837         return ret;
838 }
839 
840 
841 static int do_vm86_irq_handling(int subfunction, int irqnumber)
842 {
843         int ret;
844         switch (subfunction) {
845                 case VM86_GET_AND_RESET_IRQ: {
846                         return get_and_reset_irq(irqnumber);
847                 }
848                 case VM86_GET_IRQ_BITS: {
849                         return irqbits;
850                 }
851                 case VM86_REQUEST_IRQ: {
852                         int sig = irqnumber >> 8;
853                         int irq = irqnumber & 255;
854                         if (!capable(CAP_SYS_ADMIN)) return -EPERM;
855                         if (!((1 << sig) & ALLOWED_SIGS)) return -EPERM;
856                         if (invalid_vm86_irq(irq)) return -EPERM;
857                         if (vm86_irqs[irq].tsk) return -EPERM;
858                         ret = request_irq(irq, &irq_handler, 0, VM86_IRQNAME, NULL);
859                         if (ret) return ret;
860                         vm86_irqs[irq].sig = sig;
861                         vm86_irqs[irq].tsk = current;
862                         return irq;
863                 }
864                 case  VM86_FREE_IRQ: {
865                         if (invalid_vm86_irq(irqnumber)) return -EPERM;
866                         if (!vm86_irqs[irqnumber].tsk) return 0;
867                         if (vm86_irqs[irqnumber].tsk != current) return -EPERM;
868                         free_vm86_irq(irqnumber);
869                         return 0;
870                 }
871         }
872         return -EINVAL;
873 }
874 
875 

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