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 
save_v86_state(struct kernel_vm86_regs * regs,int retval)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 
SYSCALL_DEFINE1(vm86old,struct vm86_struct __user *,user_vm86)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 
SYSCALL_DEFINE2(vm86,unsigned long,cmd,unsigned long,arg)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 
do_sys_vm86(struct vm86plus_struct __user * user_vm86,bool plus)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 		char comm[TASK_COMM_LEN];
250 
251 		pr_info_once("vm86: '%s' uses VM86_SCREEN_BITMAP, which is no longer supported\n", get_task_comm(comm, current));
252 		return -EINVAL;
253 	}
254 
255 	memset(&vm86regs, 0, sizeof(vm86regs));
256 
257 	vm86regs.pt.bx = v.regs.ebx;
258 	vm86regs.pt.cx = v.regs.ecx;
259 	vm86regs.pt.dx = v.regs.edx;
260 	vm86regs.pt.si = v.regs.esi;
261 	vm86regs.pt.di = v.regs.edi;
262 	vm86regs.pt.bp = v.regs.ebp;
263 	vm86regs.pt.ax = v.regs.eax;
264 	vm86regs.pt.ip = v.regs.eip;
265 	vm86regs.pt.cs = v.regs.cs;
266 	vm86regs.pt.flags = v.regs.eflags;
267 	vm86regs.pt.sp = v.regs.esp;
268 	vm86regs.pt.ss = v.regs.ss;
269 	vm86regs.es = v.regs.es;
270 	vm86regs.ds = v.regs.ds;
271 	vm86regs.fs = v.regs.fs;
272 	vm86regs.gs = v.regs.gs;
273 
274 	vm86->flags = v.flags;
275 	vm86->cpu_type = v.cpu_type;
276 
277 	if (copy_from_user(&vm86->int_revectored,
278 			   &user_vm86->int_revectored,
279 			   sizeof(struct revectored_struct)))
280 		return -EFAULT;
281 	if (copy_from_user(&vm86->int21_revectored,
282 			   &user_vm86->int21_revectored,
283 			   sizeof(struct revectored_struct)))
284 		return -EFAULT;
285 	if (plus) {
286 		if (copy_from_user(&vm86->vm86plus, &user_vm86->vm86plus,
287 				   sizeof(struct vm86plus_info_struct)))
288 			return -EFAULT;
289 		vm86->vm86plus.is_vm86pus = 1;
290 	} else
291 		memset(&vm86->vm86plus, 0,
292 		       sizeof(struct vm86plus_info_struct));
293 
294 	memcpy(&vm86->regs32, regs, sizeof(struct pt_regs));
295 	vm86->user_vm86 = user_vm86;
296 
297 /*
298  * The flags register is also special: we cannot trust that the user
299  * has set it up safely, so this makes sure interrupt etc flags are
300  * inherited from protected mode.
301  */
302 	VEFLAGS = vm86regs.pt.flags;
303 	vm86regs.pt.flags &= SAFE_MASK;
304 	vm86regs.pt.flags |= regs->flags & ~SAFE_MASK;
305 	vm86regs.pt.flags |= X86_VM_MASK;
306 
307 	vm86regs.pt.orig_ax = regs->orig_ax;
308 
309 	switch (vm86->cpu_type) {
310 	case CPU_286:
311 		vm86->veflags_mask = 0;
312 		break;
313 	case CPU_386:
314 		vm86->veflags_mask = X86_EFLAGS_NT | X86_EFLAGS_IOPL;
315 		break;
316 	case CPU_486:
317 		vm86->veflags_mask = X86_EFLAGS_AC | X86_EFLAGS_NT | X86_EFLAGS_IOPL;
318 		break;
319 	default:
320 		vm86->veflags_mask = X86_EFLAGS_ID | X86_EFLAGS_AC | X86_EFLAGS_NT | X86_EFLAGS_IOPL;
321 		break;
322 	}
323 
324 /*
325  * Save old state
326  */
327 	vm86->saved_sp0 = tsk->thread.sp0;
328 	savesegment(gs, vm86->regs32.gs);
329 
330 	/* make room for real-mode segments */
331 	preempt_disable();
332 	tsk->thread.sp0 += 16;
333 
334 	if (boot_cpu_has(X86_FEATURE_SEP)) {
335 		tsk->thread.sysenter_cs = 0;
336 		refresh_sysenter_cs(&tsk->thread);
337 	}
338 
339 	update_task_stack(tsk);
340 	preempt_enable();
341 
342 	memcpy((struct kernel_vm86_regs *)regs, &vm86regs, sizeof(vm86regs));
343 	return regs->ax;
344 }
345 
set_IF(struct kernel_vm86_regs * regs)346 static inline void set_IF(struct kernel_vm86_regs *regs)
347 {
348 	VEFLAGS |= X86_EFLAGS_VIF;
349 }
350 
clear_IF(struct kernel_vm86_regs * regs)351 static inline void clear_IF(struct kernel_vm86_regs *regs)
352 {
353 	VEFLAGS &= ~X86_EFLAGS_VIF;
354 }
355 
clear_TF(struct kernel_vm86_regs * regs)356 static inline void clear_TF(struct kernel_vm86_regs *regs)
357 {
358 	regs->pt.flags &= ~X86_EFLAGS_TF;
359 }
360 
clear_AC(struct kernel_vm86_regs * regs)361 static inline void clear_AC(struct kernel_vm86_regs *regs)
362 {
363 	regs->pt.flags &= ~X86_EFLAGS_AC;
364 }
365 
366 /*
367  * It is correct to call set_IF(regs) from the set_vflags_*
368  * functions. However someone forgot to call clear_IF(regs)
369  * in the opposite case.
370  * After the command sequence CLI PUSHF STI POPF you should
371  * end up with interrupts disabled, but you ended up with
372  * interrupts enabled.
373  *  ( I was testing my own changes, but the only bug I
374  *    could find was in a function I had not changed. )
375  * [KD]
376  */
377 
set_vflags_long(unsigned long flags,struct kernel_vm86_regs * regs)378 static inline void set_vflags_long(unsigned long flags, struct kernel_vm86_regs *regs)
379 {
380 	set_flags(VEFLAGS, flags, current->thread.vm86->veflags_mask);
381 	set_flags(regs->pt.flags, flags, SAFE_MASK);
382 	if (flags & X86_EFLAGS_IF)
383 		set_IF(regs);
384 	else
385 		clear_IF(regs);
386 }
387 
set_vflags_short(unsigned short flags,struct kernel_vm86_regs * regs)388 static inline void set_vflags_short(unsigned short flags, struct kernel_vm86_regs *regs)
389 {
390 	set_flags(VFLAGS, flags, current->thread.vm86->veflags_mask);
391 	set_flags(regs->pt.flags, flags, SAFE_MASK);
392 	if (flags & X86_EFLAGS_IF)
393 		set_IF(regs);
394 	else
395 		clear_IF(regs);
396 }
397 
get_vflags(struct kernel_vm86_regs * regs)398 static inline unsigned long get_vflags(struct kernel_vm86_regs *regs)
399 {
400 	unsigned long flags = regs->pt.flags & RETURN_MASK;
401 
402 	if (VEFLAGS & X86_EFLAGS_VIF)
403 		flags |= X86_EFLAGS_IF;
404 	flags |= X86_EFLAGS_IOPL;
405 	return flags | (VEFLAGS & current->thread.vm86->veflags_mask);
406 }
407 
is_revectored(int nr,struct revectored_struct * bitmap)408 static inline int is_revectored(int nr, struct revectored_struct *bitmap)
409 {
410 	return test_bit(nr, bitmap->__map);
411 }
412 
413 #define val_byte(val, n) (((__u8 *)&val)[n])
414 
415 #define pushb(base, ptr, val, err_label) \
416 	do { \
417 		__u8 __val = val; \
418 		ptr--; \
419 		if (put_user(__val, base + ptr) < 0) \
420 			goto err_label; \
421 	} while (0)
422 
423 #define pushw(base, ptr, val, err_label) \
424 	do { \
425 		__u16 __val = val; \
426 		ptr--; \
427 		if (put_user(val_byte(__val, 1), base + ptr) < 0) \
428 			goto err_label; \
429 		ptr--; \
430 		if (put_user(val_byte(__val, 0), base + ptr) < 0) \
431 			goto err_label; \
432 	} while (0)
433 
434 #define pushl(base, ptr, val, err_label) \
435 	do { \
436 		__u32 __val = val; \
437 		ptr--; \
438 		if (put_user(val_byte(__val, 3), base + ptr) < 0) \
439 			goto err_label; \
440 		ptr--; \
441 		if (put_user(val_byte(__val, 2), base + ptr) < 0) \
442 			goto err_label; \
443 		ptr--; \
444 		if (put_user(val_byte(__val, 1), base + ptr) < 0) \
445 			goto err_label; \
446 		ptr--; \
447 		if (put_user(val_byte(__val, 0), base + ptr) < 0) \
448 			goto err_label; \
449 	} while (0)
450 
451 #define popb(base, ptr, err_label) \
452 	({ \
453 		__u8 __res; \
454 		if (get_user(__res, base + ptr) < 0) \
455 			goto err_label; \
456 		ptr++; \
457 		__res; \
458 	})
459 
460 #define popw(base, ptr, err_label) \
461 	({ \
462 		__u16 __res; \
463 		if (get_user(val_byte(__res, 0), base + ptr) < 0) \
464 			goto err_label; \
465 		ptr++; \
466 		if (get_user(val_byte(__res, 1), base + ptr) < 0) \
467 			goto err_label; \
468 		ptr++; \
469 		__res; \
470 	})
471 
472 #define popl(base, ptr, err_label) \
473 	({ \
474 		__u32 __res; \
475 		if (get_user(val_byte(__res, 0), base + ptr) < 0) \
476 			goto err_label; \
477 		ptr++; \
478 		if (get_user(val_byte(__res, 1), base + ptr) < 0) \
479 			goto err_label; \
480 		ptr++; \
481 		if (get_user(val_byte(__res, 2), base + ptr) < 0) \
482 			goto err_label; \
483 		ptr++; \
484 		if (get_user(val_byte(__res, 3), base + ptr) < 0) \
485 			goto err_label; \
486 		ptr++; \
487 		__res; \
488 	})
489 
490 /* There are so many possible reasons for this function to return
491  * VM86_INTx, so adding another doesn't bother me. We can expect
492  * userspace programs to be able to handle it. (Getting a problem
493  * in userspace is always better than an Oops anyway.) [KD]
494  */
do_int(struct kernel_vm86_regs * regs,int i,unsigned char __user * ssp,unsigned short sp)495 static void do_int(struct kernel_vm86_regs *regs, int i,
496     unsigned char __user *ssp, unsigned short sp)
497 {
498 	unsigned long __user *intr_ptr;
499 	unsigned long segoffs;
500 	struct vm86 *vm86 = current->thread.vm86;
501 
502 	if (regs->pt.cs == BIOSSEG)
503 		goto cannot_handle;
504 	if (is_revectored(i, &vm86->int_revectored))
505 		goto cannot_handle;
506 	if (i == 0x21 && is_revectored(AH(regs), &vm86->int21_revectored))
507 		goto cannot_handle;
508 	intr_ptr = (unsigned long __user *) (i << 2);
509 	if (get_user(segoffs, intr_ptr))
510 		goto cannot_handle;
511 	if ((segoffs >> 16) == BIOSSEG)
512 		goto cannot_handle;
513 	pushw(ssp, sp, get_vflags(regs), cannot_handle);
514 	pushw(ssp, sp, regs->pt.cs, cannot_handle);
515 	pushw(ssp, sp, IP(regs), cannot_handle);
516 	regs->pt.cs = segoffs >> 16;
517 	SP(regs) -= 6;
518 	IP(regs) = segoffs & 0xffff;
519 	clear_TF(regs);
520 	clear_IF(regs);
521 	clear_AC(regs);
522 	return;
523 
524 cannot_handle:
525 	save_v86_state(regs, VM86_INTx + (i << 8));
526 }
527 
handle_vm86_trap(struct kernel_vm86_regs * regs,long error_code,int trapno)528 int handle_vm86_trap(struct kernel_vm86_regs *regs, long error_code, int trapno)
529 {
530 	struct vm86 *vm86 = current->thread.vm86;
531 
532 	if (vm86->vm86plus.is_vm86pus) {
533 		if ((trapno == 3) || (trapno == 1)) {
534 			save_v86_state(regs, VM86_TRAP + (trapno << 8));
535 			return 0;
536 		}
537 		do_int(regs, trapno, (unsigned char __user *) (regs->pt.ss << 4), SP(regs));
538 		return 0;
539 	}
540 	if (trapno != 1)
541 		return 1; /* we let this handle by the calling routine */
542 	current->thread.trap_nr = trapno;
543 	current->thread.error_code = error_code;
544 	force_sig(SIGTRAP);
545 	return 0;
546 }
547 
handle_vm86_fault(struct kernel_vm86_regs * regs,long error_code)548 void handle_vm86_fault(struct kernel_vm86_regs *regs, long error_code)
549 {
550 	unsigned char opcode;
551 	unsigned char __user *csp;
552 	unsigned char __user *ssp;
553 	unsigned short ip, sp, orig_flags;
554 	int data32, pref_done;
555 	struct vm86plus_info_struct *vmpi = &current->thread.vm86->vm86plus;
556 
557 #define CHECK_IF_IN_TRAP \
558 	if (vmpi->vm86dbg_active && vmpi->vm86dbg_TFpendig) \
559 		newflags |= X86_EFLAGS_TF
560 
561 	orig_flags = *(unsigned short *)&regs->pt.flags;
562 
563 	csp = (unsigned char __user *) (regs->pt.cs << 4);
564 	ssp = (unsigned char __user *) (regs->pt.ss << 4);
565 	sp = SP(regs);
566 	ip = IP(regs);
567 
568 	data32 = 0;
569 	pref_done = 0;
570 	do {
571 		switch (opcode = popb(csp, ip, simulate_sigsegv)) {
572 		case 0x66:      /* 32-bit data */     data32 = 1; break;
573 		case 0x67:      /* 32-bit address */  break;
574 		case 0x2e:      /* CS */              break;
575 		case 0x3e:      /* DS */              break;
576 		case 0x26:      /* ES */              break;
577 		case 0x36:      /* SS */              break;
578 		case 0x65:      /* GS */              break;
579 		case 0x64:      /* FS */              break;
580 		case 0xf2:      /* repnz */       break;
581 		case 0xf3:      /* rep */             break;
582 		default: pref_done = 1;
583 		}
584 	} while (!pref_done);
585 
586 	switch (opcode) {
587 
588 	/* pushf */
589 	case 0x9c:
590 		if (data32) {
591 			pushl(ssp, sp, get_vflags(regs), simulate_sigsegv);
592 			SP(regs) -= 4;
593 		} else {
594 			pushw(ssp, sp, get_vflags(regs), simulate_sigsegv);
595 			SP(regs) -= 2;
596 		}
597 		IP(regs) = ip;
598 		goto vm86_fault_return;
599 
600 	/* popf */
601 	case 0x9d:
602 		{
603 		unsigned long newflags;
604 		if (data32) {
605 			newflags = popl(ssp, sp, simulate_sigsegv);
606 			SP(regs) += 4;
607 		} else {
608 			newflags = popw(ssp, sp, simulate_sigsegv);
609 			SP(regs) += 2;
610 		}
611 		IP(regs) = ip;
612 		CHECK_IF_IN_TRAP;
613 		if (data32)
614 			set_vflags_long(newflags, regs);
615 		else
616 			set_vflags_short(newflags, regs);
617 
618 		goto check_vip;
619 		}
620 
621 	/* int xx */
622 	case 0xcd: {
623 		int intno = popb(csp, ip, simulate_sigsegv);
624 		IP(regs) = ip;
625 		if (vmpi->vm86dbg_active) {
626 			if ((1 << (intno & 7)) & vmpi->vm86dbg_intxxtab[intno >> 3]) {
627 				save_v86_state(regs, VM86_INTx + (intno << 8));
628 				return;
629 			}
630 		}
631 		do_int(regs, intno, ssp, sp);
632 		return;
633 	}
634 
635 	/* iret */
636 	case 0xcf:
637 		{
638 		unsigned long newip;
639 		unsigned long newcs;
640 		unsigned long newflags;
641 		if (data32) {
642 			newip = popl(ssp, sp, simulate_sigsegv);
643 			newcs = popl(ssp, sp, simulate_sigsegv);
644 			newflags = popl(ssp, sp, simulate_sigsegv);
645 			SP(regs) += 12;
646 		} else {
647 			newip = popw(ssp, sp, simulate_sigsegv);
648 			newcs = popw(ssp, sp, simulate_sigsegv);
649 			newflags = popw(ssp, sp, simulate_sigsegv);
650 			SP(regs) += 6;
651 		}
652 		IP(regs) = newip;
653 		regs->pt.cs = newcs;
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 	/* cli */
664 	case 0xfa:
665 		IP(regs) = ip;
666 		clear_IF(regs);
667 		goto vm86_fault_return;
668 
669 	/* sti */
670 	/*
671 	 * Damn. This is incorrect: the 'sti' instruction should actually
672 	 * enable interrupts after the /next/ instruction. Not good.
673 	 *
674 	 * Probably needs some horsing around with the TF flag. Aiee..
675 	 */
676 	case 0xfb:
677 		IP(regs) = ip;
678 		set_IF(regs);
679 		goto check_vip;
680 
681 	default:
682 		save_v86_state(regs, VM86_UNKNOWN);
683 	}
684 
685 	return;
686 
687 check_vip:
688 	if ((VEFLAGS & (X86_EFLAGS_VIP | X86_EFLAGS_VIF)) ==
689 	    (X86_EFLAGS_VIP | X86_EFLAGS_VIF)) {
690 		save_v86_state(regs, VM86_STI);
691 		return;
692 	}
693 
694 vm86_fault_return:
695 	if (vmpi->force_return_for_pic  && (VEFLAGS & (X86_EFLAGS_IF | X86_EFLAGS_VIF))) {
696 		save_v86_state(regs, VM86_PICRETURN);
697 		return;
698 	}
699 	if (orig_flags & X86_EFLAGS_TF)
700 		handle_vm86_trap(regs, 0, X86_TRAP_DB);
701 	return;
702 
703 simulate_sigsegv:
704 	/* FIXME: After a long discussion with Stas we finally
705 	 *        agreed, that this is wrong. Here we should
706 	 *        really send a SIGSEGV to the user program.
707 	 *        But how do we create the correct context? We
708 	 *        are inside a general protection fault handler
709 	 *        and has just returned from a page fault handler.
710 	 *        The correct context for the signal handler
711 	 *        should be a mixture of the two, but how do we
712 	 *        get the information? [KD]
713 	 */
714 	save_v86_state(regs, VM86_UNKNOWN);
715 }
716 
717 /* ---------------- vm86 special IRQ passing stuff ----------------- */
718 
719 #define VM86_IRQNAME		"vm86irq"
720 
721 static struct vm86_irqs {
722 	struct task_struct *tsk;
723 	int sig;
724 } vm86_irqs[16];
725 
726 static DEFINE_SPINLOCK(irqbits_lock);
727 static int irqbits;
728 
729 #define ALLOWED_SIGS (1 /* 0 = don't send a signal */ \
730 	| (1 << SIGUSR1) | (1 << SIGUSR2) | (1 << SIGIO)  | (1 << SIGURG) \
731 	| (1 << SIGUNUSED))
732 
irq_handler(int intno,void * dev_id)733 static irqreturn_t irq_handler(int intno, void *dev_id)
734 {
735 	int irq_bit;
736 	unsigned long flags;
737 
738 	spin_lock_irqsave(&irqbits_lock, flags);
739 	irq_bit = 1 << intno;
740 	if ((irqbits & irq_bit) || !vm86_irqs[intno].tsk)
741 		goto out;
742 	irqbits |= irq_bit;
743 	if (vm86_irqs[intno].sig)
744 		send_sig(vm86_irqs[intno].sig, vm86_irqs[intno].tsk, 1);
745 	/*
746 	 * IRQ will be re-enabled when user asks for the irq (whether
747 	 * polling or as a result of the signal)
748 	 */
749 	disable_irq_nosync(intno);
750 	spin_unlock_irqrestore(&irqbits_lock, flags);
751 	return IRQ_HANDLED;
752 
753 out:
754 	spin_unlock_irqrestore(&irqbits_lock, flags);
755 	return IRQ_NONE;
756 }
757 
free_vm86_irq(int irqnumber)758 static inline void free_vm86_irq(int irqnumber)
759 {
760 	unsigned long flags;
761 
762 	free_irq(irqnumber, NULL);
763 	vm86_irqs[irqnumber].tsk = NULL;
764 
765 	spin_lock_irqsave(&irqbits_lock, flags);
766 	irqbits &= ~(1 << irqnumber);
767 	spin_unlock_irqrestore(&irqbits_lock, flags);
768 }
769 
release_vm86_irqs(struct task_struct * task)770 void release_vm86_irqs(struct task_struct *task)
771 {
772 	int i;
773 	for (i = FIRST_VM86_IRQ ; i <= LAST_VM86_IRQ; i++)
774 	    if (vm86_irqs[i].tsk == task)
775 		free_vm86_irq(i);
776 }
777 
get_and_reset_irq(int irqnumber)778 static inline int get_and_reset_irq(int irqnumber)
779 {
780 	int bit;
781 	unsigned long flags;
782 	int ret = 0;
783 
784 	if (invalid_vm86_irq(irqnumber)) return 0;
785 	if (vm86_irqs[irqnumber].tsk != current) return 0;
786 	spin_lock_irqsave(&irqbits_lock, flags);
787 	bit = irqbits & (1 << irqnumber);
788 	irqbits &= ~bit;
789 	if (bit) {
790 		enable_irq(irqnumber);
791 		ret = 1;
792 	}
793 
794 	spin_unlock_irqrestore(&irqbits_lock, flags);
795 	return ret;
796 }
797 
798 
do_vm86_irq_handling(int subfunction,int irqnumber)799 static int do_vm86_irq_handling(int subfunction, int irqnumber)
800 {
801 	int ret;
802 	switch (subfunction) {
803 		case VM86_GET_AND_RESET_IRQ: {
804 			return get_and_reset_irq(irqnumber);
805 		}
806 		case VM86_GET_IRQ_BITS: {
807 			return irqbits;
808 		}
809 		case VM86_REQUEST_IRQ: {
810 			int sig = irqnumber >> 8;
811 			int irq = irqnumber & 255;
812 			if (!capable(CAP_SYS_ADMIN)) return -EPERM;
813 			if (!((1 << sig) & ALLOWED_SIGS)) return -EPERM;
814 			if (invalid_vm86_irq(irq)) return -EPERM;
815 			if (vm86_irqs[irq].tsk) return -EPERM;
816 			ret = request_irq(irq, &irq_handler, 0, VM86_IRQNAME, NULL);
817 			if (ret) return ret;
818 			vm86_irqs[irq].sig = sig;
819 			vm86_irqs[irq].tsk = current;
820 			return irq;
821 		}
822 		case  VM86_FREE_IRQ: {
823 			if (invalid_vm86_irq(irqnumber)) return -EPERM;
824 			if (!vm86_irqs[irqnumber].tsk) return 0;
825 			if (vm86_irqs[irqnumber].tsk != current) return -EPERM;
826 			free_vm86_irq(irqnumber);
827 			return 0;
828 		}
829 	}
830 	return -EINVAL;
831 }
832 
833