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 <[email protected]>
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 * <[email protected]>
12 *
13 * 22 mar 2002 - Added missing clear_IF in set_vflags_* Kasper Dupont
14 * <[email protected]>
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 <[email protected]>
21 *
22 * 9 apr 2002 - Changed syntax of macros in handle_vm86_fault.
23 * Kasper Dupont <[email protected]>
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 <[email protected]>
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(®s->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 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
set_IF(struct kernel_vm86_regs * regs)345 static inline void set_IF(struct kernel_vm86_regs *regs)
346 {
347 VEFLAGS |= X86_EFLAGS_VIF;
348 }
349
clear_IF(struct kernel_vm86_regs * regs)350 static inline void clear_IF(struct kernel_vm86_regs *regs)
351 {
352 VEFLAGS &= ~X86_EFLAGS_VIF;
353 }
354
clear_TF(struct kernel_vm86_regs * regs)355 static inline void clear_TF(struct kernel_vm86_regs *regs)
356 {
357 regs->pt.flags &= ~X86_EFLAGS_TF;
358 }
359
clear_AC(struct kernel_vm86_regs * regs)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
set_vflags_long(unsigned long flags,struct kernel_vm86_regs * regs)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
set_vflags_short(unsigned short flags,struct kernel_vm86_regs * regs)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
get_vflags(struct kernel_vm86_regs * regs)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
is_revectored(int nr,struct revectored_struct * bitmap)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 */
do_int(struct kernel_vm86_regs * regs,int i,unsigned char __user * ssp,unsigned short sp)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
handle_vm86_trap(struct kernel_vm86_regs * regs,long error_code,int trapno)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
handle_vm86_fault(struct kernel_vm86_regs * regs,long error_code)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 = ¤t->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 *)®s->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
irq_handler(int intno,void * dev_id)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
free_vm86_irq(int irqnumber)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
release_vm86_irqs(struct task_struct * task)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
get_and_reset_irq(int irqnumber)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
do_vm86_irq_handling(int subfunction,int irqnumber)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