xref: /linux/arch/x86/kernel/vm86_32.c (revision c159dfbdd4fc62fa08f6715d9d6c34d39cf40446)
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 
102 	/*
103 	 * This gets called from entry.S with interrupts disabled, but
104 	 * from process context. Enable interrupts here, before trying
105 	 * to access user space.
106 	 */
107 	local_irq_enable();
108 
109 	BUG_ON(!vm86);
110 
111 	set_flags(regs->pt.flags, VEFLAGS, X86_EFLAGS_VIF | vm86->veflags_mask);
112 	user = vm86->user_vm86;
113 
114 	if (!user_access_begin(user, vm86->vm86plus.is_vm86pus ?
115 		       sizeof(struct vm86plus_struct) :
116 		       sizeof(struct vm86_struct)))
117 		goto Efault;
118 
119 	unsafe_put_user(regs->pt.bx, &user->regs.ebx, Efault_end);
120 	unsafe_put_user(regs->pt.cx, &user->regs.ecx, Efault_end);
121 	unsafe_put_user(regs->pt.dx, &user->regs.edx, Efault_end);
122 	unsafe_put_user(regs->pt.si, &user->regs.esi, Efault_end);
123 	unsafe_put_user(regs->pt.di, &user->regs.edi, Efault_end);
124 	unsafe_put_user(regs->pt.bp, &user->regs.ebp, Efault_end);
125 	unsafe_put_user(regs->pt.ax, &user->regs.eax, Efault_end);
126 	unsafe_put_user(regs->pt.ip, &user->regs.eip, Efault_end);
127 	unsafe_put_user(regs->pt.cs, &user->regs.cs, Efault_end);
128 	unsafe_put_user(regs->pt.flags, &user->regs.eflags, Efault_end);
129 	unsafe_put_user(regs->pt.sp, &user->regs.esp, Efault_end);
130 	unsafe_put_user(regs->pt.ss, &user->regs.ss, Efault_end);
131 	unsafe_put_user(regs->es, &user->regs.es, Efault_end);
132 	unsafe_put_user(regs->ds, &user->regs.ds, Efault_end);
133 	unsafe_put_user(regs->fs, &user->regs.fs, Efault_end);
134 	unsafe_put_user(regs->gs, &user->regs.gs, Efault_end);
135 
136 	/*
137 	 * Don't write screen_bitmap in case some user had a value there
138 	 * and expected it to remain unchanged.
139 	 */
140 
141 	user_access_end();
142 
143 exit_vm86:
144 	preempt_disable();
145 	tsk->thread.sp0 = vm86->saved_sp0;
146 	tsk->thread.sysenter_cs = __KERNEL_CS;
147 	update_task_stack(tsk);
148 	refresh_sysenter_cs(&tsk->thread);
149 	vm86->saved_sp0 = 0;
150 	preempt_enable();
151 
152 	memcpy(&regs->pt, &vm86->regs32, sizeof(struct pt_regs));
153 
154 	loadsegment(gs, vm86->regs32.gs);
155 
156 	regs->pt.ax = retval;
157 	return;
158 
159 Efault_end:
160 	user_access_end();
161 Efault:
162 	pr_alert("could not access userspace vm86 info\n");
163 	force_exit_sig(SIGSEGV);
164 	goto exit_vm86;
165 }
166 
167 static int do_vm86_irq_handling(int subfunction, int irqnumber);
168 static long do_sys_vm86(struct vm86plus_struct __user *user_vm86, bool plus);
169 
170 SYSCALL_DEFINE1(vm86old, struct vm86_struct __user *, user_vm86)
171 {
172 	return do_sys_vm86((struct vm86plus_struct __user *) user_vm86, false);
173 }
174 
175 
176 SYSCALL_DEFINE2(vm86, unsigned long, cmd, unsigned long, arg)
177 {
178 	switch (cmd) {
179 	case VM86_REQUEST_IRQ:
180 	case VM86_FREE_IRQ:
181 	case VM86_GET_IRQ_BITS:
182 	case VM86_GET_AND_RESET_IRQ:
183 		return do_vm86_irq_handling(cmd, (int)arg);
184 	case VM86_PLUS_INSTALL_CHECK:
185 		/*
186 		 * NOTE: on old vm86 stuff this will return the error
187 		 *  from access_ok(), because the subfunction is
188 		 *  interpreted as (invalid) address to vm86_struct.
189 		 *  So the installation check works.
190 		 */
191 		return 0;
192 	}
193 
194 	/* we come here only for functions VM86_ENTER, VM86_ENTER_NO_BYPASS */
195 	return do_sys_vm86((struct vm86plus_struct __user *) arg, true);
196 }
197 
198 
199 static long do_sys_vm86(struct vm86plus_struct __user *user_vm86, bool plus)
200 {
201 	struct task_struct *tsk = current;
202 	struct vm86 *vm86 = tsk->thread.vm86;
203 	struct kernel_vm86_regs vm86regs;
204 	struct pt_regs *regs = current_pt_regs();
205 	unsigned long err = 0;
206 	struct vm86_struct v;
207 
208 	err = security_mmap_addr(0);
209 	if (err) {
210 		/*
211 		 * vm86 cannot virtualize the address space, so vm86 users
212 		 * need to manage the low 1MB themselves using mmap.  Given
213 		 * that BIOS places important data in the first page, vm86
214 		 * is essentially useless if mmap_min_addr != 0.  DOSEMU,
215 		 * for example, won't even bother trying to use vm86 if it
216 		 * can't map a page at virtual address 0.
217 		 *
218 		 * To reduce the available kernel attack surface, simply
219 		 * disallow vm86(old) for users who cannot mmap at va 0.
220 		 *
221 		 * The implementation of security_mmap_addr will allow
222 		 * suitably privileged users to map va 0 even if
223 		 * vm.mmap_min_addr is set above 0, and we want this
224 		 * behavior for vm86 as well, as it ensures that legacy
225 		 * tools like vbetool will not fail just because of
226 		 * vm.mmap_min_addr.
227 		 */
228 		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",
229 			     current->comm, task_pid_nr(current),
230 			     from_kuid_munged(&init_user_ns, current_uid()));
231 		return -EPERM;
232 	}
233 
234 	if (!vm86) {
235 		if (!(vm86 = kzalloc(sizeof(*vm86), GFP_KERNEL)))
236 			return -ENOMEM;
237 		tsk->thread.vm86 = vm86;
238 	}
239 	if (vm86->saved_sp0)
240 		return -EPERM;
241 
242 	if (copy_from_user(&v, user_vm86,
243 			offsetof(struct vm86_struct, int_revectored)))
244 		return -EFAULT;
245 
246 
247 	/* VM86_SCREEN_BITMAP had numerous bugs and appears to have no users. */
248 	if (v.flags & VM86_SCREEN_BITMAP) {
249 		pr_info_once("vm86: '%s' uses VM86_SCREEN_BITMAP, which is no longer supported\n",
250 			     current->comm);
251 		return -EINVAL;
252 	}
253 
254 	memset(&vm86regs, 0, sizeof(vm86regs));
255 
256 	vm86regs.pt.bx = v.regs.ebx;
257 	vm86regs.pt.cx = v.regs.ecx;
258 	vm86regs.pt.dx = v.regs.edx;
259 	vm86regs.pt.si = v.regs.esi;
260 	vm86regs.pt.di = v.regs.edi;
261 	vm86regs.pt.bp = v.regs.ebp;
262 	vm86regs.pt.ax = v.regs.eax;
263 	vm86regs.pt.ip = v.regs.eip;
264 	vm86regs.pt.cs = v.regs.cs;
265 	vm86regs.pt.flags = v.regs.eflags;
266 	vm86regs.pt.sp = v.regs.esp;
267 	vm86regs.pt.ss = v.regs.ss;
268 	vm86regs.es = v.regs.es;
269 	vm86regs.ds = v.regs.ds;
270 	vm86regs.fs = v.regs.fs;
271 	vm86regs.gs = v.regs.gs;
272 
273 	vm86->flags = v.flags;
274 	vm86->cpu_type = v.cpu_type;
275 
276 	if (copy_from_user(&vm86->int_revectored,
277 			   &user_vm86->int_revectored,
278 			   sizeof(struct revectored_struct)))
279 		return -EFAULT;
280 	if (copy_from_user(&vm86->int21_revectored,
281 			   &user_vm86->int21_revectored,
282 			   sizeof(struct revectored_struct)))
283 		return -EFAULT;
284 	if (plus) {
285 		if (copy_from_user(&vm86->vm86plus, &user_vm86->vm86plus,
286 				   sizeof(struct vm86plus_info_struct)))
287 			return -EFAULT;
288 		vm86->vm86plus.is_vm86pus = 1;
289 	} else
290 		memset(&vm86->vm86plus, 0,
291 		       sizeof(struct vm86plus_info_struct));
292 
293 	memcpy(&vm86->regs32, regs, sizeof(struct pt_regs));
294 	vm86->user_vm86 = user_vm86;
295 
296 /*
297  * The flags register is also special: we cannot trust that the user
298  * has set it up safely, so this makes sure interrupt etc flags are
299  * inherited from protected mode.
300  */
301 	VEFLAGS = vm86regs.pt.flags;
302 	vm86regs.pt.flags &= SAFE_MASK;
303 	vm86regs.pt.flags |= regs->flags & ~SAFE_MASK;
304 	vm86regs.pt.flags |= X86_VM_MASK;
305 
306 	vm86regs.pt.orig_ax = regs->orig_ax;
307 
308 	switch (vm86->cpu_type) {
309 	case CPU_286:
310 		vm86->veflags_mask = 0;
311 		break;
312 	case CPU_386:
313 		vm86->veflags_mask = X86_EFLAGS_NT | X86_EFLAGS_IOPL;
314 		break;
315 	case CPU_486:
316 		vm86->veflags_mask = X86_EFLAGS_AC | X86_EFLAGS_NT | X86_EFLAGS_IOPL;
317 		break;
318 	default:
319 		vm86->veflags_mask = X86_EFLAGS_ID | X86_EFLAGS_AC | X86_EFLAGS_NT | X86_EFLAGS_IOPL;
320 		break;
321 	}
322 
323 /*
324  * Save old state
325  */
326 	vm86->saved_sp0 = tsk->thread.sp0;
327 	savesegment(gs, vm86->regs32.gs);
328 
329 	/* make room for real-mode segments */
330 	preempt_disable();
331 	tsk->thread.sp0 += 16;
332 
333 	if (boot_cpu_has(X86_FEATURE_SEP)) {
334 		tsk->thread.sysenter_cs = 0;
335 		refresh_sysenter_cs(&tsk->thread);
336 	}
337 
338 	update_task_stack(tsk);
339 	preempt_enable();
340 
341 	memcpy((struct kernel_vm86_regs *)regs, &vm86regs, sizeof(vm86regs));
342 	return regs->ax;
343 }
344 
345 static inline void set_IF(struct kernel_vm86_regs *regs)
346 {
347 	VEFLAGS |= X86_EFLAGS_VIF;
348 }
349 
350 static inline void clear_IF(struct kernel_vm86_regs *regs)
351 {
352 	VEFLAGS &= ~X86_EFLAGS_VIF;
353 }
354 
355 static inline void clear_TF(struct kernel_vm86_regs *regs)
356 {
357 	regs->pt.flags &= ~X86_EFLAGS_TF;
358 }
359 
360 static inline void clear_AC(struct kernel_vm86_regs *regs)
361 {
362 	regs->pt.flags &= ~X86_EFLAGS_AC;
363 }
364 
365 /*
366  * It is correct to call set_IF(regs) from the set_vflags_*
367  * functions. However someone forgot to call clear_IF(regs)
368  * in the opposite case.
369  * After the command sequence CLI PUSHF STI POPF you should
370  * end up with interrupts disabled, but you ended up with
371  * interrupts enabled.
372  *  ( I was testing my own changes, but the only bug I
373  *    could find was in a function I had not changed. )
374  * [KD]
375  */
376 
377 static inline void set_vflags_long(unsigned long flags, struct kernel_vm86_regs *regs)
378 {
379 	set_flags(VEFLAGS, flags, current->thread.vm86->veflags_mask);
380 	set_flags(regs->pt.flags, flags, SAFE_MASK);
381 	if (flags & X86_EFLAGS_IF)
382 		set_IF(regs);
383 	else
384 		clear_IF(regs);
385 }
386 
387 static inline void set_vflags_short(unsigned short flags, struct kernel_vm86_regs *regs)
388 {
389 	set_flags(VFLAGS, flags, current->thread.vm86->veflags_mask);
390 	set_flags(regs->pt.flags, flags, SAFE_MASK);
391 	if (flags & X86_EFLAGS_IF)
392 		set_IF(regs);
393 	else
394 		clear_IF(regs);
395 }
396 
397 static inline unsigned long get_vflags(struct kernel_vm86_regs *regs)
398 {
399 	unsigned long flags = regs->pt.flags & RETURN_MASK;
400 
401 	if (VEFLAGS & X86_EFLAGS_VIF)
402 		flags |= X86_EFLAGS_IF;
403 	flags |= X86_EFLAGS_IOPL;
404 	return flags | (VEFLAGS & current->thread.vm86->veflags_mask);
405 }
406 
407 static inline int is_revectored(int nr, struct revectored_struct *bitmap)
408 {
409 	return test_bit(nr, bitmap->__map);
410 }
411 
412 #define val_byte(val, n) (((__u8 *)&val)[n])
413 
414 #define pushb(base, ptr, val, err_label) \
415 	do { \
416 		__u8 __val = val; \
417 		ptr--; \
418 		if (put_user(__val, base + ptr) < 0) \
419 			goto err_label; \
420 	} while (0)
421 
422 #define pushw(base, ptr, val, err_label) \
423 	do { \
424 		__u16 __val = val; \
425 		ptr--; \
426 		if (put_user(val_byte(__val, 1), base + ptr) < 0) \
427 			goto err_label; \
428 		ptr--; \
429 		if (put_user(val_byte(__val, 0), base + ptr) < 0) \
430 			goto err_label; \
431 	} while (0)
432 
433 #define pushl(base, ptr, val, err_label) \
434 	do { \
435 		__u32 __val = val; \
436 		ptr--; \
437 		if (put_user(val_byte(__val, 3), base + ptr) < 0) \
438 			goto err_label; \
439 		ptr--; \
440 		if (put_user(val_byte(__val, 2), base + ptr) < 0) \
441 			goto err_label; \
442 		ptr--; \
443 		if (put_user(val_byte(__val, 1), base + ptr) < 0) \
444 			goto err_label; \
445 		ptr--; \
446 		if (put_user(val_byte(__val, 0), base + ptr) < 0) \
447 			goto err_label; \
448 	} while (0)
449 
450 #define popb(base, ptr, err_label) \
451 	({ \
452 		__u8 __res; \
453 		if (get_user(__res, base + ptr) < 0) \
454 			goto err_label; \
455 		ptr++; \
456 		__res; \
457 	})
458 
459 #define popw(base, ptr, err_label) \
460 	({ \
461 		__u16 __res; \
462 		if (get_user(val_byte(__res, 0), base + ptr) < 0) \
463 			goto err_label; \
464 		ptr++; \
465 		if (get_user(val_byte(__res, 1), base + ptr) < 0) \
466 			goto err_label; \
467 		ptr++; \
468 		__res; \
469 	})
470 
471 #define popl(base, ptr, err_label) \
472 	({ \
473 		__u32 __res; \
474 		if (get_user(val_byte(__res, 0), base + ptr) < 0) \
475 			goto err_label; \
476 		ptr++; \
477 		if (get_user(val_byte(__res, 1), base + ptr) < 0) \
478 			goto err_label; \
479 		ptr++; \
480 		if (get_user(val_byte(__res, 2), base + ptr) < 0) \
481 			goto err_label; \
482 		ptr++; \
483 		if (get_user(val_byte(__res, 3), base + ptr) < 0) \
484 			goto err_label; \
485 		ptr++; \
486 		__res; \
487 	})
488 
489 /* There are so many possible reasons for this function to return
490  * VM86_INTx, so adding another doesn't bother me. We can expect
491  * userspace programs to be able to handle it. (Getting a problem
492  * in userspace is always better than an Oops anyway.) [KD]
493  */
494 static void do_int(struct kernel_vm86_regs *regs, int i,
495     unsigned char __user *ssp, unsigned short sp)
496 {
497 	unsigned long __user *intr_ptr;
498 	unsigned long segoffs;
499 	struct vm86 *vm86 = current->thread.vm86;
500 
501 	if (regs->pt.cs == BIOSSEG)
502 		goto cannot_handle;
503 	if (is_revectored(i, &vm86->int_revectored))
504 		goto cannot_handle;
505 	if (i == 0x21 && is_revectored(AH(regs), &vm86->int21_revectored))
506 		goto cannot_handle;
507 	intr_ptr = (unsigned long __user *) (i << 2);
508 	if (get_user(segoffs, intr_ptr))
509 		goto cannot_handle;
510 	if ((segoffs >> 16) == BIOSSEG)
511 		goto cannot_handle;
512 	pushw(ssp, sp, get_vflags(regs), cannot_handle);
513 	pushw(ssp, sp, regs->pt.cs, cannot_handle);
514 	pushw(ssp, sp, IP(regs), cannot_handle);
515 	regs->pt.cs = segoffs >> 16;
516 	SP(regs) -= 6;
517 	IP(regs) = segoffs & 0xffff;
518 	clear_TF(regs);
519 	clear_IF(regs);
520 	clear_AC(regs);
521 	return;
522 
523 cannot_handle:
524 	save_v86_state(regs, VM86_INTx + (i << 8));
525 }
526 
527 int handle_vm86_trap(struct kernel_vm86_regs *regs, long error_code, int trapno)
528 {
529 	struct vm86 *vm86 = current->thread.vm86;
530 
531 	if (vm86->vm86plus.is_vm86pus) {
532 		if ((trapno == 3) || (trapno == 1)) {
533 			save_v86_state(regs, VM86_TRAP + (trapno << 8));
534 			return 0;
535 		}
536 		do_int(regs, trapno, (unsigned char __user *) (regs->pt.ss << 4), SP(regs));
537 		return 0;
538 	}
539 	if (trapno != 1)
540 		return 1; /* we let this handle by the calling routine */
541 	current->thread.trap_nr = trapno;
542 	current->thread.error_code = error_code;
543 	force_sig(SIGTRAP);
544 	return 0;
545 }
546 
547 void handle_vm86_fault(struct kernel_vm86_regs *regs, long error_code)
548 {
549 	unsigned char opcode;
550 	unsigned char __user *csp;
551 	unsigned char __user *ssp;
552 	unsigned short ip, sp, orig_flags;
553 	int data32, pref_done;
554 	struct vm86plus_info_struct *vmpi = &current->thread.vm86->vm86plus;
555 
556 #define CHECK_IF_IN_TRAP \
557 	if (vmpi->vm86dbg_active && vmpi->vm86dbg_TFpendig) \
558 		newflags |= X86_EFLAGS_TF
559 
560 	orig_flags = *(unsigned short *)&regs->pt.flags;
561 
562 	csp = (unsigned char __user *) (regs->pt.cs << 4);
563 	ssp = (unsigned char __user *) (regs->pt.ss << 4);
564 	sp = SP(regs);
565 	ip = IP(regs);
566 
567 	data32 = 0;
568 	pref_done = 0;
569 	do {
570 		switch (opcode = popb(csp, ip, simulate_sigsegv)) {
571 		case 0x66:      /* 32-bit data */     data32 = 1; break;
572 		case 0x67:      /* 32-bit address */  break;
573 		case 0x2e:      /* CS */              break;
574 		case 0x3e:      /* DS */              break;
575 		case 0x26:      /* ES */              break;
576 		case 0x36:      /* SS */              break;
577 		case 0x65:      /* GS */              break;
578 		case 0x64:      /* FS */              break;
579 		case 0xf2:      /* repnz */       break;
580 		case 0xf3:      /* rep */             break;
581 		default: pref_done = 1;
582 		}
583 	} while (!pref_done);
584 
585 	switch (opcode) {
586 
587 	/* pushf */
588 	case 0x9c:
589 		if (data32) {
590 			pushl(ssp, sp, get_vflags(regs), simulate_sigsegv);
591 			SP(regs) -= 4;
592 		} else {
593 			pushw(ssp, sp, get_vflags(regs), simulate_sigsegv);
594 			SP(regs) -= 2;
595 		}
596 		IP(regs) = ip;
597 		goto vm86_fault_return;
598 
599 	/* popf */
600 	case 0x9d:
601 		{
602 		unsigned long newflags;
603 		if (data32) {
604 			newflags = popl(ssp, sp, simulate_sigsegv);
605 			SP(regs) += 4;
606 		} else {
607 			newflags = popw(ssp, sp, simulate_sigsegv);
608 			SP(regs) += 2;
609 		}
610 		IP(regs) = ip;
611 		CHECK_IF_IN_TRAP;
612 		if (data32)
613 			set_vflags_long(newflags, regs);
614 		else
615 			set_vflags_short(newflags, regs);
616 
617 		goto check_vip;
618 		}
619 
620 	/* int xx */
621 	case 0xcd: {
622 		int intno = popb(csp, ip, simulate_sigsegv);
623 		IP(regs) = ip;
624 		if (vmpi->vm86dbg_active) {
625 			if ((1 << (intno & 7)) & vmpi->vm86dbg_intxxtab[intno >> 3]) {
626 				save_v86_state(regs, VM86_INTx + (intno << 8));
627 				return;
628 			}
629 		}
630 		do_int(regs, intno, ssp, sp);
631 		return;
632 	}
633 
634 	/* iret */
635 	case 0xcf:
636 		{
637 		unsigned long newip;
638 		unsigned long newcs;
639 		unsigned long newflags;
640 		if (data32) {
641 			newip = popl(ssp, sp, simulate_sigsegv);
642 			newcs = popl(ssp, sp, simulate_sigsegv);
643 			newflags = popl(ssp, sp, simulate_sigsegv);
644 			SP(regs) += 12;
645 		} else {
646 			newip = popw(ssp, sp, simulate_sigsegv);
647 			newcs = popw(ssp, sp, simulate_sigsegv);
648 			newflags = popw(ssp, sp, simulate_sigsegv);
649 			SP(regs) += 6;
650 		}
651 		IP(regs) = newip;
652 		regs->pt.cs = newcs;
653 		CHECK_IF_IN_TRAP;
654 		if (data32) {
655 			set_vflags_long(newflags, regs);
656 		} else {
657 			set_vflags_short(newflags, regs);
658 		}
659 		goto check_vip;
660 		}
661 
662 	/* cli */
663 	case 0xfa:
664 		IP(regs) = ip;
665 		clear_IF(regs);
666 		goto vm86_fault_return;
667 
668 	/* sti */
669 	/*
670 	 * Damn. This is incorrect: the 'sti' instruction should actually
671 	 * enable interrupts after the /next/ instruction. Not good.
672 	 *
673 	 * Probably needs some horsing around with the TF flag. Aiee..
674 	 */
675 	case 0xfb:
676 		IP(regs) = ip;
677 		set_IF(regs);
678 		goto check_vip;
679 
680 	default:
681 		save_v86_state(regs, VM86_UNKNOWN);
682 	}
683 
684 	return;
685 
686 check_vip:
687 	if ((VEFLAGS & (X86_EFLAGS_VIP | X86_EFLAGS_VIF)) ==
688 	    (X86_EFLAGS_VIP | X86_EFLAGS_VIF)) {
689 		save_v86_state(regs, VM86_STI);
690 		return;
691 	}
692 
693 vm86_fault_return:
694 	if (vmpi->force_return_for_pic  && (VEFLAGS & (X86_EFLAGS_IF | X86_EFLAGS_VIF))) {
695 		save_v86_state(regs, VM86_PICRETURN);
696 		return;
697 	}
698 	if (orig_flags & X86_EFLAGS_TF)
699 		handle_vm86_trap(regs, 0, X86_TRAP_DB);
700 	return;
701 
702 simulate_sigsegv:
703 	/* FIXME: After a long discussion with Stas we finally
704 	 *        agreed, that this is wrong. Here we should
705 	 *        really send a SIGSEGV to the user program.
706 	 *        But how do we create the correct context? We
707 	 *        are inside a general protection fault handler
708 	 *        and has just returned from a page fault handler.
709 	 *        The correct context for the signal handler
710 	 *        should be a mixture of the two, but how do we
711 	 *        get the information? [KD]
712 	 */
713 	save_v86_state(regs, VM86_UNKNOWN);
714 }
715 
716 /* ---------------- vm86 special IRQ passing stuff ----------------- */
717 
718 #define VM86_IRQNAME		"vm86irq"
719 
720 static struct vm86_irqs {
721 	struct task_struct *tsk;
722 	int sig;
723 } vm86_irqs[16];
724 
725 static DEFINE_SPINLOCK(irqbits_lock);
726 static int irqbits;
727 
728 #define ALLOWED_SIGS (1 /* 0 = don't send a signal */ \
729 	| (1 << SIGUSR1) | (1 << SIGUSR2) | (1 << SIGIO)  | (1 << SIGURG) \
730 	| (1 << SIGUNUSED))
731 
732 static irqreturn_t irq_handler(int intno, void *dev_id)
733 {
734 	int irq_bit;
735 	unsigned long flags;
736 
737 	spin_lock_irqsave(&irqbits_lock, flags);
738 	irq_bit = 1 << intno;
739 	if ((irqbits & irq_bit) || !vm86_irqs[intno].tsk)
740 		goto out;
741 	irqbits |= irq_bit;
742 	if (vm86_irqs[intno].sig)
743 		send_sig(vm86_irqs[intno].sig, vm86_irqs[intno].tsk, 1);
744 	/*
745 	 * IRQ will be re-enabled when user asks for the irq (whether
746 	 * polling or as a result of the signal)
747 	 */
748 	disable_irq_nosync(intno);
749 	spin_unlock_irqrestore(&irqbits_lock, flags);
750 	return IRQ_HANDLED;
751 
752 out:
753 	spin_unlock_irqrestore(&irqbits_lock, flags);
754 	return IRQ_NONE;
755 }
756 
757 static inline void free_vm86_irq(int irqnumber)
758 {
759 	unsigned long flags;
760 
761 	free_irq(irqnumber, NULL);
762 	vm86_irqs[irqnumber].tsk = NULL;
763 
764 	spin_lock_irqsave(&irqbits_lock, flags);
765 	irqbits &= ~(1 << irqnumber);
766 	spin_unlock_irqrestore(&irqbits_lock, flags);
767 }
768 
769 void release_vm86_irqs(struct task_struct *task)
770 {
771 	int i;
772 	for (i = FIRST_VM86_IRQ ; i <= LAST_VM86_IRQ; i++)
773 	    if (vm86_irqs[i].tsk == task)
774 		free_vm86_irq(i);
775 }
776 
777 static inline int get_and_reset_irq(int irqnumber)
778 {
779 	int bit;
780 	unsigned long flags;
781 	int ret = 0;
782 
783 	if (invalid_vm86_irq(irqnumber)) return 0;
784 	if (vm86_irqs[irqnumber].tsk != current) return 0;
785 	spin_lock_irqsave(&irqbits_lock, flags);
786 	bit = irqbits & (1 << irqnumber);
787 	irqbits &= ~bit;
788 	if (bit) {
789 		enable_irq(irqnumber);
790 		ret = 1;
791 	}
792 
793 	spin_unlock_irqrestore(&irqbits_lock, flags);
794 	return ret;
795 }
796 
797 
798 static int do_vm86_irq_handling(int subfunction, int irqnumber)
799 {
800 	int ret;
801 	switch (subfunction) {
802 		case VM86_GET_AND_RESET_IRQ: {
803 			return get_and_reset_irq(irqnumber);
804 		}
805 		case VM86_GET_IRQ_BITS: {
806 			return irqbits;
807 		}
808 		case VM86_REQUEST_IRQ: {
809 			int sig = irqnumber >> 8;
810 			int irq = irqnumber & 255;
811 			if (!capable(CAP_SYS_ADMIN)) return -EPERM;
812 			if (!((1 << sig) & ALLOWED_SIGS)) return -EPERM;
813 			if (invalid_vm86_irq(irq)) return -EPERM;
814 			if (vm86_irqs[irq].tsk) return -EPERM;
815 			ret = request_irq(irq, &irq_handler, 0, VM86_IRQNAME, NULL);
816 			if (ret) return ret;
817 			vm86_irqs[irq].sig = sig;
818 			vm86_irqs[irq].tsk = current;
819 			return irq;
820 		}
821 		case  VM86_FREE_IRQ: {
822 			if (invalid_vm86_irq(irqnumber)) return -EPERM;
823 			if (!vm86_irqs[irqnumber].tsk) return 0;
824 			if (vm86_irqs[irqnumber].tsk != current) return -EPERM;
825 			free_vm86_irq(irqnumber);
826 			return 0;
827 		}
828 	}
829 	return -EINVAL;
830 }
831 
832