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