4 * Copyright (C) 1994 Linus Torvalds
6 * 29 dec 2001 - Fixed oopses caused by unchecked access to the vm86
7 * stack - Manfred Spraul <manfred@colorfullife.com>
9 * 22 mar 2002 - Manfred detected the stackfaults, but didn't handle
10 * them correctly. Now the emulation will be in a
11 * consistent state after stackfaults - Kasper Dupont
12 * <kasperd@daimi.au.dk>
14 * 22 mar 2002 - Added missing clear_IF in set_vflags_* Kasper Dupont
15 * <kasperd@daimi.au.dk>
17 * ?? ??? 2002 - Fixed premature returns from handle_vm86_fault
18 * caused by Kasper Dupont's changes - Stas Sergeev
20 * 4 apr 2002 - Fixed CHECK_IF_IN_TRAP broken by Stas' changes.
21 * Kasper Dupont <kasperd@daimi.au.dk>
23 * 9 apr 2002 - Changed syntax of macros in handle_vm86_fault.
24 * Kasper Dupont <kasperd@daimi.au.dk>
26 * 9 apr 2002 - Changed stack access macros to jump to a label
27 * instead of returning to userspace. This simplifies
28 * do_int, and is needed by handle_vm6_fault. Kasper
29 * Dupont <kasperd@daimi.au.dk>
33 #include <linux/capability.h>
34 #include <linux/errno.h>
35 #include <linux/interrupt.h>
36 #include <linux/sched.h>
37 #include <linux/kernel.h>
38 #include <linux/signal.h>
39 #include <linux/string.h>
41 #include <linux/smp.h>
42 #include <linux/smp_lock.h>
43 #include <linux/highmem.h>
44 #include <linux/ptrace.h>
45 #include <linux/audit.h>
46 #include <linux/stddef.h>
48 #include <asm/uaccess.h>
50 #include <asm/tlbflush.h>
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
65 * Let's hope these problems do not actually matter for anything.
69 #define KVM86 ((struct kernel_vm86_struct *)regs)
70 #define VMPI KVM86->vm86plus
74 * 8- and 16-bit register defines..
76 #define AL(regs) (((unsigned char *)&((regs)->pt.eax))[0])
77 #define AH(regs) (((unsigned char *)&((regs)->pt.eax))[1])
78 #define IP(regs) (*(unsigned short *)&((regs)->pt.eip))
79 #define SP(regs) (*(unsigned short *)&((regs)->pt.esp))
82 * virtual flags (16 and 32-bit versions)
84 #define VFLAGS (*(unsigned short *)&(current->thread.v86flags))
85 #define VEFLAGS (current->thread.v86flags)
87 #define set_flags(X,new,mask) \
88 ((X) = ((X) & ~(mask)) | ((new) & (mask)))
90 #define SAFE_MASK (0xDD5)
91 #define RETURN_MASK (0xDFF)
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
)
99 /* kernel_vm86_regs is missing xfs, so copy everything up to
100 (but not including) xgs, and then rest after xgs. */
101 ret
+= copy_to_user(user
, regs
, offsetof(struct kernel_vm86_regs
, pt
.xgs
));
102 ret
+= copy_to_user(&user
->__null_gs
, ®s
->pt
.xgs
,
103 sizeof(struct kernel_vm86_regs
) -
104 offsetof(struct kernel_vm86_regs
, pt
.xgs
));
109 /* convert vm86_regs to kernel_vm86_regs */
110 static int copy_vm86_regs_from_user(struct kernel_vm86_regs
*regs
,
111 const struct vm86_regs __user
*user
,
116 ret
+= copy_from_user(regs
, user
, offsetof(struct kernel_vm86_regs
, pt
.xgs
));
117 ret
+= copy_from_user(®s
->pt
.xgs
, &user
->__null_gs
,
118 sizeof(struct kernel_vm86_regs
) -
119 offsetof(struct kernel_vm86_regs
, pt
.xgs
) +
125 struct pt_regs
* FASTCALL(save_v86_state(struct kernel_vm86_regs
* regs
));
126 struct pt_regs
* fastcall
save_v86_state(struct kernel_vm86_regs
* regs
)
128 struct tss_struct
*tss
;
133 * This gets called from entry.S with interrupts disabled, but
134 * from process context. Enable interrupts here, before trying
135 * to access user space.
139 if (!current
->thread
.vm86_info
) {
140 printk("no vm86_info: BAD\n");
143 set_flags(regs
->pt
.eflags
, VEFLAGS
, VIF_MASK
| current
->thread
.v86mask
);
144 tmp
= copy_vm86_regs_to_user(¤t
->thread
.vm86_info
->regs
,regs
);
145 tmp
+= put_user(current
->thread
.screen_bitmap
,¤t
->thread
.vm86_info
->screen_bitmap
);
147 printk("vm86: could not access userspace vm86_info\n");
151 tss
= &per_cpu(init_tss
, get_cpu());
152 current
->thread
.esp0
= current
->thread
.saved_esp0
;
153 current
->thread
.sysenter_cs
= __KERNEL_CS
;
154 load_esp0(tss
, ¤t
->thread
);
155 current
->thread
.saved_esp0
= 0;
160 loadsegment(fs
, current
->thread
.saved_fs
);
161 ret
->xgs
= current
->thread
.saved_gs
;
166 static void mark_screen_rdonly(struct mm_struct
*mm
)
175 pgd
= pgd_offset(mm
, 0xA0000);
176 if (pgd_none_or_clear_bad(pgd
))
178 pud
= pud_offset(pgd
, 0xA0000);
179 if (pud_none_or_clear_bad(pud
))
181 pmd
= pmd_offset(pud
, 0xA0000);
182 if (pmd_none_or_clear_bad(pmd
))
184 pte
= pte_offset_map_lock(mm
, pmd
, 0xA0000, &ptl
);
185 for (i
= 0; i
< 32; i
++) {
186 if (pte_present(*pte
))
187 set_pte(pte
, pte_wrprotect(*pte
));
190 pte_unmap_unlock(pte
, ptl
);
197 static int do_vm86_irq_handling(int subfunction
, int irqnumber
);
198 static void do_sys_vm86(struct kernel_vm86_struct
*info
, struct task_struct
*tsk
);
200 asmlinkage
int sys_vm86old(struct pt_regs regs
)
202 struct vm86_struct __user
*v86
= (struct vm86_struct __user
*)regs
.ebx
;
203 struct kernel_vm86_struct info
; /* declare this _on top_,
204 * this avoids wasting of stack space.
205 * This remains on the stack until we
206 * return to 32 bit user space.
208 struct task_struct
*tsk
;
209 int tmp
, ret
= -EPERM
;
212 if (tsk
->thread
.saved_esp0
)
214 tmp
= copy_vm86_regs_from_user(&info
.regs
, &v86
->regs
,
215 offsetof(struct kernel_vm86_struct
, vm86plus
) -
220 memset(&info
.vm86plus
, 0, (int)&info
.regs32
- (int)&info
.vm86plus
);
222 tsk
->thread
.vm86_info
= v86
;
223 do_sys_vm86(&info
, tsk
);
224 ret
= 0; /* we never return here */
230 asmlinkage
int sys_vm86(struct pt_regs regs
)
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.
237 struct task_struct
*tsk
;
239 struct vm86plus_struct __user
*v86
;
243 case VM86_REQUEST_IRQ
:
245 case VM86_GET_IRQ_BITS
:
246 case VM86_GET_AND_RESET_IRQ
:
247 ret
= do_vm86_irq_handling(regs
.ebx
, (int)regs
.ecx
);
249 case VM86_PLUS_INSTALL_CHECK
:
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.
259 /* we come here only for functions VM86_ENTER, VM86_ENTER_NO_BYPASS */
261 if (tsk
->thread
.saved_esp0
)
263 v86
= (struct vm86plus_struct __user
*)regs
.ecx
;
264 tmp
= copy_vm86_regs_from_user(&info
.regs
, &v86
->regs
,
265 offsetof(struct kernel_vm86_struct
, regs32
) -
271 info
.vm86plus
.is_vm86pus
= 1;
272 tsk
->thread
.vm86_info
= (struct vm86_struct __user
*)v86
;
273 do_sys_vm86(&info
, tsk
);
274 ret
= 0; /* we never return here */
280 static void do_sys_vm86(struct kernel_vm86_struct
*info
, struct task_struct
*tsk
)
282 struct tss_struct
*tss
;
284 * make sure the vm86() system call doesn't try to do anything silly
286 info
->regs
.pt
.xds
= 0;
287 info
->regs
.pt
.xes
= 0;
288 info
->regs
.pt
.xgs
= 0;
290 /* we are clearing fs later just before "jmp resume_userspace",
291 * because it is not saved/restored.
295 * The eflags register is also special: we cannot trust that the user
296 * has set it up safely, so this makes sure interrupt etc flags are
297 * inherited from protected mode.
299 VEFLAGS
= info
->regs
.pt
.eflags
;
300 info
->regs
.pt
.eflags
&= SAFE_MASK
;
301 info
->regs
.pt
.eflags
|= info
->regs32
->eflags
& ~SAFE_MASK
;
302 info
->regs
.pt
.eflags
|= VM_MASK
;
304 switch (info
->cpu_type
) {
306 tsk
->thread
.v86mask
= 0;
309 tsk
->thread
.v86mask
= NT_MASK
| IOPL_MASK
;
312 tsk
->thread
.v86mask
= AC_MASK
| NT_MASK
| IOPL_MASK
;
315 tsk
->thread
.v86mask
= ID_MASK
| AC_MASK
| NT_MASK
| IOPL_MASK
;
320 * Save old state, set default return value (%eax) to 0
322 info
->regs32
->eax
= 0;
323 tsk
->thread
.saved_esp0
= tsk
->thread
.esp0
;
324 savesegment(fs
, tsk
->thread
.saved_fs
);
325 tsk
->thread
.saved_gs
= info
->regs32
->xgs
;
327 tss
= &per_cpu(init_tss
, get_cpu());
328 tsk
->thread
.esp0
= (unsigned long) &info
->VM86_TSS_ESP0
;
330 tsk
->thread
.sysenter_cs
= 0;
331 load_esp0(tss
, &tsk
->thread
);
334 tsk
->thread
.screen_bitmap
= info
->screen_bitmap
;
335 if (info
->flags
& VM86_SCREEN_BITMAP
)
336 mark_screen_rdonly(tsk
->mm
);
338 /*call audit_syscall_exit since we do not exit via the normal paths */
339 if (unlikely(current
->audit_context
))
340 audit_syscall_exit(AUDITSC_RESULT(0), 0);
342 __asm__
__volatile__(
346 "jmp resume_userspace"
348 :"r" (&info
->regs
), "r" (task_thread_info(tsk
)), "r" (0));
349 /* we never return here */
352 static inline void return_to_32bit(struct kernel_vm86_regs
* regs16
, int retval
)
354 struct pt_regs
* regs32
;
356 regs32
= save_v86_state(regs16
);
357 regs32
->eax
= retval
;
358 __asm__
__volatile__("movl %0,%%esp\n\t"
360 "jmp resume_userspace"
361 : : "r" (regs32
), "r" (current_thread_info()));
364 static inline void set_IF(struct kernel_vm86_regs
* regs
)
367 if (VEFLAGS
& VIP_MASK
)
368 return_to_32bit(regs
, VM86_STI
);
371 static inline void clear_IF(struct kernel_vm86_regs
* regs
)
373 VEFLAGS
&= ~VIF_MASK
;
376 static inline void clear_TF(struct kernel_vm86_regs
* regs
)
378 regs
->pt
.eflags
&= ~TF_MASK
;
381 static inline void clear_AC(struct kernel_vm86_regs
* regs
)
383 regs
->pt
.eflags
&= ~AC_MASK
;
386 /* It is correct to call set_IF(regs) from the set_vflags_*
387 * functions. However someone forgot to call clear_IF(regs)
388 * in the opposite case.
389 * After the command sequence CLI PUSHF STI POPF you should
390 * end up with interrups disabled, but you ended up with
391 * interrupts enabled.
392 * ( I was testing my own changes, but the only bug I
393 * could find was in a function I had not changed. )
397 static inline void set_vflags_long(unsigned long eflags
, struct kernel_vm86_regs
* regs
)
399 set_flags(VEFLAGS
, eflags
, current
->thread
.v86mask
);
400 set_flags(regs
->pt
.eflags
, eflags
, SAFE_MASK
);
401 if (eflags
& IF_MASK
)
407 static inline void set_vflags_short(unsigned short flags
, struct kernel_vm86_regs
* regs
)
409 set_flags(VFLAGS
, flags
, current
->thread
.v86mask
);
410 set_flags(regs
->pt
.eflags
, flags
, SAFE_MASK
);
417 static inline unsigned long get_vflags(struct kernel_vm86_regs
* regs
)
419 unsigned long flags
= regs
->pt
.eflags
& RETURN_MASK
;
421 if (VEFLAGS
& VIF_MASK
)
424 return flags
| (VEFLAGS
& current
->thread
.v86mask
);
427 static inline int is_revectored(int nr
, struct revectored_struct
* bitmap
)
429 __asm__
__volatile__("btl %2,%1\n\tsbbl %0,%0"
431 :"m" (*bitmap
),"r" (nr
));
435 #define val_byte(val, n) (((__u8 *)&val)[n])
437 #define pushb(base, ptr, val, err_label) \
441 if (put_user(__val, base + ptr) < 0) \
445 #define pushw(base, ptr, val, err_label) \
449 if (put_user(val_byte(__val, 1), base + ptr) < 0) \
452 if (put_user(val_byte(__val, 0), base + ptr) < 0) \
456 #define pushl(base, ptr, val, err_label) \
460 if (put_user(val_byte(__val, 3), base + ptr) < 0) \
463 if (put_user(val_byte(__val, 2), base + ptr) < 0) \
466 if (put_user(val_byte(__val, 1), base + ptr) < 0) \
469 if (put_user(val_byte(__val, 0), base + ptr) < 0) \
473 #define popb(base, ptr, err_label) \
476 if (get_user(__res, base + ptr) < 0) \
482 #define popw(base, ptr, err_label) \
485 if (get_user(val_byte(__res, 0), base + ptr) < 0) \
488 if (get_user(val_byte(__res, 1), base + ptr) < 0) \
494 #define popl(base, ptr, err_label) \
497 if (get_user(val_byte(__res, 0), base + ptr) < 0) \
500 if (get_user(val_byte(__res, 1), base + ptr) < 0) \
503 if (get_user(val_byte(__res, 2), base + ptr) < 0) \
506 if (get_user(val_byte(__res, 3), base + ptr) < 0) \
512 /* There are so many possible reasons for this function to return
513 * VM86_INTx, so adding another doesn't bother me. We can expect
514 * userspace programs to be able to handle it. (Getting a problem
515 * in userspace is always better than an Oops anyway.) [KD]
517 static void do_int(struct kernel_vm86_regs
*regs
, int i
,
518 unsigned char __user
* ssp
, unsigned short sp
)
520 unsigned long __user
*intr_ptr
;
521 unsigned long segoffs
;
523 if (regs
->pt
.xcs
== BIOSSEG
)
525 if (is_revectored(i
, &KVM86
->int_revectored
))
527 if (i
==0x21 && is_revectored(AH(regs
),&KVM86
->int21_revectored
))
529 intr_ptr
= (unsigned long __user
*) (i
<< 2);
530 if (get_user(segoffs
, intr_ptr
))
532 if ((segoffs
>> 16) == BIOSSEG
)
534 pushw(ssp
, sp
, get_vflags(regs
), cannot_handle
);
535 pushw(ssp
, sp
, regs
->pt
.xcs
, cannot_handle
);
536 pushw(ssp
, sp
, IP(regs
), cannot_handle
);
537 regs
->pt
.xcs
= segoffs
>> 16;
539 IP(regs
) = segoffs
& 0xffff;
546 return_to_32bit(regs
, VM86_INTx
+ (i
<< 8));
549 int handle_vm86_trap(struct kernel_vm86_regs
* regs
, long error_code
, int trapno
)
551 if (VMPI
.is_vm86pus
) {
552 if ( (trapno
==3) || (trapno
==1) )
553 return_to_32bit(regs
, VM86_TRAP
+ (trapno
<< 8));
554 do_int(regs
, trapno
, (unsigned char __user
*) (regs
->pt
.xss
<< 4), SP(regs
));
558 return 1; /* we let this handle by the calling routine */
559 if (current
->ptrace
& PT_PTRACED
) {
561 spin_lock_irqsave(¤t
->sighand
->siglock
, flags
);
562 sigdelset(¤t
->blocked
, SIGTRAP
);
564 spin_unlock_irqrestore(¤t
->sighand
->siglock
, flags
);
566 send_sig(SIGTRAP
, current
, 1);
567 current
->thread
.trap_no
= trapno
;
568 current
->thread
.error_code
= error_code
;
572 void handle_vm86_fault(struct kernel_vm86_regs
* regs
, long error_code
)
574 unsigned char opcode
;
575 unsigned char __user
*csp
;
576 unsigned char __user
*ssp
;
577 unsigned short ip
, sp
, orig_flags
;
578 int data32
, pref_done
;
580 #define CHECK_IF_IN_TRAP \
581 if (VMPI.vm86dbg_active && VMPI.vm86dbg_TFpendig) \
583 #define VM86_FAULT_RETURN do { \
584 if (VMPI.force_return_for_pic && (VEFLAGS & (IF_MASK | VIF_MASK))) \
585 return_to_32bit(regs, VM86_PICRETURN); \
586 if (orig_flags & TF_MASK) \
587 handle_vm86_trap(regs, 0, 1); \
590 orig_flags
= *(unsigned short *)®s
->pt
.eflags
;
592 csp
= (unsigned char __user
*) (regs
->pt
.xcs
<< 4);
593 ssp
= (unsigned char __user
*) (regs
->pt
.xss
<< 4);
600 switch (opcode
= popb(csp
, ip
, simulate_sigsegv
)) {
601 case 0x66: /* 32-bit data */ data32
=1; break;
602 case 0x67: /* 32-bit address */ break;
603 case 0x2e: /* CS */ break;
604 case 0x3e: /* DS */ break;
605 case 0x26: /* ES */ break;
606 case 0x36: /* SS */ break;
607 case 0x65: /* GS */ break;
608 case 0x64: /* FS */ break;
609 case 0xf2: /* repnz */ break;
610 case 0xf3: /* rep */ break;
611 default: pref_done
= 1;
613 } while (!pref_done
);
620 pushl(ssp
, sp
, get_vflags(regs
), simulate_sigsegv
);
623 pushw(ssp
, sp
, get_vflags(regs
), simulate_sigsegv
);
632 unsigned long newflags
;
634 newflags
=popl(ssp
, sp
, simulate_sigsegv
);
637 newflags
= popw(ssp
, sp
, simulate_sigsegv
);
643 set_vflags_long(newflags
, regs
);
645 set_vflags_short(newflags
, regs
);
652 int intno
=popb(csp
, ip
, simulate_sigsegv
);
654 if (VMPI
.vm86dbg_active
) {
655 if ( (1 << (intno
&7)) & VMPI
.vm86dbg_intxxtab
[intno
>> 3] )
656 return_to_32bit(regs
, VM86_INTx
+ (intno
<< 8));
658 do_int(regs
, intno
, ssp
, sp
);
667 unsigned long newflags
;
669 newip
=popl(ssp
, sp
, simulate_sigsegv
);
670 newcs
=popl(ssp
, sp
, simulate_sigsegv
);
671 newflags
=popl(ssp
, sp
, simulate_sigsegv
);
674 newip
= popw(ssp
, sp
, simulate_sigsegv
);
675 newcs
= popw(ssp
, sp
, simulate_sigsegv
);
676 newflags
= popw(ssp
, sp
, simulate_sigsegv
);
680 regs
->pt
.xcs
= newcs
;
683 set_vflags_long(newflags
, regs
);
685 set_vflags_short(newflags
, regs
);
698 * Damn. This is incorrect: the 'sti' instruction should actually
699 * enable interrupts after the /next/ instruction. Not good.
701 * Probably needs some horsing around with the TF flag. Aiee..
709 return_to_32bit(regs
, VM86_UNKNOWN
);
715 /* FIXME: After a long discussion with Stas we finally
716 * agreed, that this is wrong. Here we should
717 * really send a SIGSEGV to the user program.
718 * But how do we create the correct context? We
719 * are inside a general protection fault handler
720 * and has just returned from a page fault handler.
721 * The correct context for the signal handler
722 * should be a mixture of the two, but how do we
723 * get the information? [KD]
725 return_to_32bit(regs
, VM86_UNKNOWN
);
728 /* ---------------- vm86 special IRQ passing stuff ----------------- */
730 #define VM86_IRQNAME "vm86irq"
732 static struct vm86_irqs
{
733 struct task_struct
*tsk
;
737 static DEFINE_SPINLOCK(irqbits_lock
);
740 #define ALLOWED_SIGS ( 1 /* 0 = don't send a signal */ \
741 | (1 << SIGUSR1) | (1 << SIGUSR2) | (1 << SIGIO) | (1 << SIGURG) \
744 static irqreturn_t
irq_handler(int intno
, void *dev_id
)
749 spin_lock_irqsave(&irqbits_lock
, flags
);
750 irq_bit
= 1 << intno
;
751 if ((irqbits
& irq_bit
) || ! vm86_irqs
[intno
].tsk
)
754 if (vm86_irqs
[intno
].sig
)
755 send_sig(vm86_irqs
[intno
].sig
, vm86_irqs
[intno
].tsk
, 1);
757 * IRQ will be re-enabled when user asks for the irq (whether
758 * polling or as a result of the signal)
760 disable_irq_nosync(intno
);
761 spin_unlock_irqrestore(&irqbits_lock
, flags
);
765 spin_unlock_irqrestore(&irqbits_lock
, flags
);
769 static inline void free_vm86_irq(int irqnumber
)
773 free_irq(irqnumber
, NULL
);
774 vm86_irqs
[irqnumber
].tsk
= NULL
;
776 spin_lock_irqsave(&irqbits_lock
, flags
);
777 irqbits
&= ~(1 << irqnumber
);
778 spin_unlock_irqrestore(&irqbits_lock
, flags
);
781 void release_vm86_irqs(struct task_struct
*task
)
784 for (i
= FIRST_VM86_IRQ
; i
<= LAST_VM86_IRQ
; i
++)
785 if (vm86_irqs
[i
].tsk
== task
)
789 static inline int get_and_reset_irq(int irqnumber
)
795 if (invalid_vm86_irq(irqnumber
)) return 0;
796 if (vm86_irqs
[irqnumber
].tsk
!= current
) return 0;
797 spin_lock_irqsave(&irqbits_lock
, flags
);
798 bit
= irqbits
& (1 << irqnumber
);
801 enable_irq(irqnumber
);
805 spin_unlock_irqrestore(&irqbits_lock
, flags
);
810 static int do_vm86_irq_handling(int subfunction
, int irqnumber
)
813 switch (subfunction
) {
814 case VM86_GET_AND_RESET_IRQ
: {
815 return get_and_reset_irq(irqnumber
);
817 case VM86_GET_IRQ_BITS
: {
820 case VM86_REQUEST_IRQ
: {
821 int sig
= irqnumber
>> 8;
822 int irq
= irqnumber
& 255;
823 if (!capable(CAP_SYS_ADMIN
)) return -EPERM
;
824 if (!((1 << sig
) & ALLOWED_SIGS
)) return -EPERM
;
825 if (invalid_vm86_irq(irq
)) return -EPERM
;
826 if (vm86_irqs
[irq
].tsk
) return -EPERM
;
827 ret
= request_irq(irq
, &irq_handler
, 0, VM86_IRQNAME
, NULL
);
829 vm86_irqs
[irq
].sig
= sig
;
830 vm86_irqs
[irq
].tsk
= current
;
833 case VM86_FREE_IRQ
: {
834 if (invalid_vm86_irq(irqnumber
)) return -EPERM
;
835 if (!vm86_irqs
[irqnumber
].tsk
) return 0;
836 if (vm86_irqs
[irqnumber
].tsk
!= current
) return -EPERM
;
837 free_vm86_irq(irqnumber
);